Showing papers on "Cefotaxime published in 2007"

First Report of the Emergence of CTX-M-Type Extended-Spectrum β-Lactamases (ESBLs) as the Predominant ESBL Isolated in a U.S. Health Care System

Abstract: CTX-M-type extended-spectrum β-lactamases (ESBLs) have become increasingly common worldwide, with the notable exception of the United States, where TEM- and SHV-type ESBLs have appeared to predominate. We have noted the emergence of ESBLs in our health care system (the University Health System in San Antonio, TX), especially in Escherichia coli isolates, that preferentially hydrolyze cefotaxime rather than ceftazidime, suggesting the possibility of CTX-M-type enzymes. Microbiology laboratory records were reviewed to identify ESBL-producing isolates and to compare the diameters of ceftazidime disk diffusion zones of inhibition to cefotaxime zone diameters. All isolates had been initially detected and confirmed using the procedures recommended by the Clinical and Laboratory Standards Institute. A total of 94 stored ESBL-producing isolates recovered between January 2000 and June 2006 (predominately from blood and normally sterile fluids) were retrieved for further study and screened using PCR primers specific for the presence of CTX-M, TEM, and SHV ESBLs. Only small numbers of retained ESBL-producing isolates were available for study in 2000 and 2002. The percentages of available ESBL-producing organisms in the following years were found to produce CTX-M enzymes: 2000, 25%; 2001, 10%; 2002, 0%; 2003, 60%; 2004, 69%; 2005, 89%; and 2006, 70%. The most common CTX-M-type ESBL was CTX-M-15, followed by CTX-M-16, CTX-M-8, and CTX-M-14. Comparing the disk diffusion zone diameters of cefotaxime and ceftazidime was helpful with the initial recognition of CTX-M-producing E. coli, which had an average cefotaxime zone diameter 7 mm smaller than the ceftazidime zone. However, comparing ceftazidime and cefotaxime zones for CTX-M-producing Klebsiella spp. was not helpful with initial recognition. CTX-M enzymes were also identified in Proteus mirabilis, Enterobacter spp., and Morganella morganii. Based on pulsed-field gel electrophoresis typing of the E. coli isolates, the CTX-M-producing isolates did not represent the spread of a single clone in the institution or in the community. In conclusion, CTX-M-type ESBLs are now the most common ESBL type isolated from patients in our health care system and may also be present but unrecognized in other U.S. locales.

Spread of Extended-Spectrum β-Lactamase CTX-M-Producing Escherichia coli Clinical Isolates in Community and Nosocomial Environments in Portugal

Abstract: Of the 181 unduplicated Escherichia coli strains isolated in nine different hospitals in three Portuguese regions, 119 were extended-spectrum β-lactamase (ESBL)-CTX-M producers and were selected for phenotype and genotype characterization. CTX-M producer strains were prevalent among community-acquired infections (56%), urinary tract infections (76%), and patients ≥60 years old (76%). In MIC tests, all strains were resistant to cefotaxime, 92% were resistant to ceftazidime, 93% were resistant to quinolones, 89% were resistant to aminoglycoside, and 26% were resistant to trimethoprim-sulfamethoxazole; all strains were sensitive to carbapenems, and 92% of the strains had a multidrug resistance phenotype. Molecular methods identified 109 isolates harboring a blaCTX-M-15 gene, 1 harboring the blaCTX-M-32 gene (first identification in the country), and 9 harboring the blaCTX-M-14 gene. All isolates presented the ISEcp1 element upstream from the blaCTX-M genes; one presented the IS903 element (downstream of blaCTX-M-14 gene), and none had the IS26 element; 85% carried blaTEM-1B, and 84% also carried a blaOXA-30. Genetic relatedness analysis based on pulsed-field gel electrophoresis defined five clusters and indicated that 76% of all isolates (from cluster IV) corresponded to a single epidemic strain. Of the 47 strains from one hospital, 41 belonged to cluster IV and were disseminated in three main wards. CTX-M-producing E. coli strains are currently a problem in Portugal, with CTX-M-15 particularly common. This study suggests that the horizontal transfer of blaCTX-M genes, mediated by plasmids and/or mobile elements, contributes to the dissemination of CTX-M enzymes to community and hospital environments. The use of extended-spectrum cephalosporins, quinolones, and aminoglycosides is compromised, leaving carbapenems as the therapeutic option for severe infections caused by ESBL producers.

In vitro activity of ceftaroline (PPI-0903M, T-91825) against bacteria with defined resistance mechanisms and phenotypes

Abstract: Background Ceftaroline (PPI-0903M, T-91825) is a novel cephalosporin, administered as an N-phosphono prodrug. We investigated its in vitro activity and resistance selection potential. Methods MICs were determined by CLSI agar dilution, but with varied inocula. Mutant selection was investigated in single- and multi-step procedures. Results MICs for methicillin-resistant Staphylococcus aureus (MRSA) were 0.5–2 mg/L, compared with 0.12–0.25 mg/L for methicillin-susceptible S. aureus; corresponding values for coagulase-negative staphylococci were 0.25–2 and 0.06–0.12 mg/L, respectively. Even with 2% NaCl added, all MRSA were susceptible at 2 mg/L. MICs for Enterococcus faecalis were from 0.25 to 8 mg/L; E. faecium was resistant. MICs for Escherichia coli, Klebsiella spp., Morganella morganii and Proteeae without acquired resistance were 0.06–0.5 mg/L versus 0.12–1 mg/L for Enterobacter, Serratia and Citrobacter spp. and 2–8 mg/L for Acinetobacter spp. MICs rose to 1–2 mg/L for many Enterobacteriaceae with classical TEM s-lactamases, and were much higher for those with extended-spectrum s-lactamases (ESBLs), hyperproduced AmpC or K1 enzymes. MICs for strains with classical TEM/SHV s-lactamases rose if the inoculum was increased to 106 cfu/spot; this effect was even more marked for those with ESBLs. Resistance due to Class A s-lactamases was reversed by clavulanate. Geometric mean MICs were 0.005, 0.05 and 0.09 mg/L for penicillin-susceptible, -intermediate and -resistant Streptococcus pneumoniae strains, respectively—lower than for any comparator s-lactam. Haemophilus influenzae and Moraxella catarrhalis were very susceptible, although with marginally raised MICs for s-lactamase-positive Moraxella strains and for haemophili with chromosomal ampicillin resistance. Ceftaroline selected AmpC-derepressed Enterobacter mutants similarly to cefotaxime in single-step experiments; in multi-step procedures it selected ESBL variants of blaTEM in E. coli. Resistance selection was not seen with S. aureus, H. influenzae or pneumococci. Conclusions Ceftaroline has impressive anti-MRSA and anti-pneumococcal activity. Slight lability to classical TEM and SHV s-lactamases is exceptional for an oxyimino-cephalosporin, but was reversible with clavulanate, as was the greater resistance mediated by ESBLs. Resistance selection occurred with Enterobacteriaceae, not MRSA.

Ampicillin-Resistant Non-β-Lactamase-Producing Haemophilus influenzae in Spain: Recent Emergence of Clonal Isolates with Increased Resistance to Cefotaxime and Cefixime

Abstract: The sequence of the ftsI gene encoding the transpeptidase domain of penicillin-binding protein 3 (PBP 3) was determined for 354 nonconsecutive Haemophilus influenzae isolates from Spain; 17.8% of them were ampicillin susceptible, 56% were beta-lactamase nonproducing ampicillin resistant (BLNAR), 15.8% were beta-lactamase producers and ampicillin resistant, and 10.4% displayed both resistance mechanisms. The ftsI gene sequences had 28 different mutation patterns and amino acid substitutions at 23 positions. Some 93.2% of the BLNAR strains had amino acid substitutions at the Lys-Thr-Gly (KTG) motif, the two most common being Asn526 to Lys (83.9%) and Arg517 to His (9.3%). Amino acid substitutions at positions 377, 385, and 389, which conferred cefotaxime and cefixime MICs 10 to 60 times higher than those of susceptible strains, were found for the first time in Europe. In 72 isolates for which the repressor acrR gene of the AcrAB efflux pump was sequenced, numerous amino acid substitutions were found. Eight isolates with ampicillin MICs of 0.25 to 2 microg/ml showed changes that predicted the early termination of the acrR reading frame. Pulsed-field gel electrophoresis analysis demonstrated that most BLNAR strains were genetically diverse, although clonal dissemination was detected in a group of isolates presenting with increased resistance to cefotaxime and cefixime. Background antibiotic use at the community level revealed a marked trend toward increased amoxicillin-clavulanic acid consumption. BLNAR H. influenzae strains have arisen by vertical and horizontal spread and have evolved to adapt rapidly to the increased selective pressures posed by the use of oral penicillins and cephalosporins.

Resistance patterns of urinary isolates in a tertiary Indian hospital.

Abstract: Background: To analyze the pathogenic organisms recovered from patients with urinary tract infection in a tertiary Indian hospital setting along with determination of the occurrence and antimicrobial sensitivity of uropathogens on a retrospective basis during a period of one year. Methods : A total of 5073 urine samples were processed. Urine culture was done using conventional microbiological techniques. Biochemical testing was used to identify the organisms and antibiotic sensitivity was done by the Kirby Bauer method. Results: A total of 2436 uropathogens were isolated. E coli were seen in 50.7% samples followed by Klebsiella sp (27.6%). Staphylococcus aureus was the commonest Gram- positive isolate (1.5%). Urinary tract infection (UTI) was seen in 70.5% females as compared to 29.5% males. A high recovery of isolates was noted from July to September. Multi drug resistance was commonest with Enterococcus (78.8%) followed by Pseudomonas (65.1%). Drugs, which retained usefulness for Gram-negative isolates, were amikacin, norfloxacin and cefotaxime. For Gram-positive isolates, vancomycin, teicoplanin, lincomycin and Norfloxacin were very effective. Conclusions : Our study highlights the changing etiology of UTI and emergence of drug resistance within the Indian subcontinent. Keywords: Urinary Tract Infections, Pathogens, Antibiotics

In vitro evaluation of antibiotics' combinations for empirical therapy of suspected methicillin resistant Staphylococcus aureus severe respiratory infections

Abstract: Methicillin resistant Staphylococcus aureus (MRSA) is an increasingly common cause of nosocomial infections, causing severe morbidity and mortality worldwide, and accounting in some hospitals for more than 50% of all S. aureus diseases. Treatment of infections caused by resistant bacterial pathogens mainly relies on two therapeutic modalities: development of new antimicrobials and use of combinations of available antibiotics. Combinations of antibiotics used in the empiric treatment of infections with suspected methicillin resistant Staphylococcus aureus etiology were investigated. Double (vancomycin or teicoplanin with either levofloxacin or cefotaxime) and triple (vancomycin or teicoplanin + levofloxacin + one among amikacin, ceftazidime, cefepime, imipenem, piperacillin/tazobactam) combinations were evaluated by means of checkerboard assay and time kill curves. Mutational rates of single and combined drugs at antimicrobial concentrations equal to the resistance breakpoints were also calculated. Vancomycin or teicoplanin + levofloxacin showed synergy in 16/50 and in 9/50 strains respectively, while vancomycin or teicoplanin + cefotaxime resulted synergic for 43/50 and 23/50 strains, respectively. Triple combinations, involving teicoplanin, levofloxacin and ceftazidime or piperacillin/tazobactam gave synergy in 20/25 strains. Teicoplanin + levofloxacin gave synergy in triple combinations more frequently than vancomycin + levofloxacin. For single antibiotics, mutational frequencies ranged between 10-5 and <10-9 for levofloxacin, cefotaxime, amikacin and imipenem, and <10-9 for vancomycin and teicoplanin. When tested in combinations, mutational frequencies fell below 10-9 for all the combinations. In vitro evidence of synergy between glycopeptides, fluoroquinolones (levofloxacin) and β-lactams and of reduction of mutational frequencies by combinations are suggestive for a potential role in empirical therapy of severe pneumonia with suspected MRSA etiology.

Antibiotic resistance profile & extended spectrum beta-lactamase (ESBL) production in Acinetobacter species.

Abstract: Background & objectives Members of the genus Acinetobacter are an important cause of nosocomial infections and with widespread resistance to various antibiotics. Extended spectrum beta lactamase (ESBL) associated resistance among Acinetobacter species is now known. The aim of this study was to speciate clinical isolates of Acinetobacter, analyze their resistance patterns, identify the production ESBLs and compare the role of different cephalosporins in detecting ESBL production in the isolates. Methods One hundred and fifty clinical isolates of Acinetobacter were speciated by various phenotypic tests. Antibiotic susceptibility was determined by the standard disc diffusion method. ESBL production was detected by the double disk approximation test using clavulanate containing disk and four different cephalosporin disks. Results of the above test were confirmed using the NCCLS phenotypic confirmatory test for ESBLs on a limited number of isolates. Results Most of the isolates were of respiratory origin. A. calcoaceticus A. baumannii (Acb) complex was the predominant species isolated (75%). Most isolates were resistant to the antibiotics tested including the third generation cephalosporins. Most isolates were sensitive to carbapenems and cefoperazone-sulbactam. ESBL production was detected in 28 per cent of the isolates. In the double disc approximation test, cefepime and cefotaxime could detect most of the ESBLs in Acinetobacter isolates. Interpretation & conclusion A high level of antibiotic resistance was found in Acinetobacter in our study. Acb complex was the predominant and the more resistant species. Relatively high levels (28%) of ESBL have been detected in Acinetobacter and may reflect the scenario in India. ESBL production in Acinetobacter should be promptly detected and reported as it helps in treating individual cases and also in controlling the spread of these resistant phenotypes to other individuals.

Escherichia coli from community-acquired urinary tract infections resistant to fluoroquinolones and extended-spectrum beta-lactams

Abstract: Background: Uropathogenic Escherichia coli are increasingly becoming resistant to flouroquinolones and to other commonly available antimicrobials. We sought to investigate the genetic basis for fluoroquinolone and extended spectrum beta-lactam (ESBL) resistance in 17 fluoroquinolone-resistant (MIC of levofloxacin and ciprofloxacin >32 μg/ml) E. coli isolated from patients with urinary tract infections (UTIs). Methods: We applied PCR and Pulsed Field Gel Electrophoresis (PFGE) to characterize resistance genes and to determine clonal relatedness of strains, respectively. Results: Twelve of the 17 E. coli were resistant to multiple drugs, including ampicillin, co-amoxyclav, cefotaxime, ceftriaxone, ceftazidime and gentamicin and nalidixic acid and produced plasmid-mediated CTX-M-15 type ESBLs and CMY-2 AmpC type enzymes. The other 5 E. coli that were non-ESBL-producing were multiply resistant to ampicillin, nitrofurantoin, cefoxitin, nalidixic acid. Resistance to fluoroquinolones resulted from a combination of the presence of qnrA, qnrB, ciprofloxacin acetylating enzyme designated aac(6’)-1b-cr, and mutations in the two amino acid substitutions; 83 Serine (TCG) to Leucine (TTG) and 87 Aspartic acid (GAC) to Asparagine (AAC). Conclusion: Antibiogram patterns and PFGE of E. coli showed that these were community acquired UTI caused by pockets of clonally-related and some discreet strain types. Plasmid-mediated CTX-M-15 beta-lactamases and CMY-2 AmpC enzymes and fluoroquinolone resistant E. coli are becoming increasingly prevalent in hospitals in Kenya, posing a major challenge in the management of UTIs.

Dose-related selection of fluoroquinolone-resistant Escherichia coli

Abstract: The worldwide increase in antibiotic resistance is a concern for public health. When the appropriate antibiotic dosage is determined, the priorities are efficacy and toxicity. The aim of this thesis was to gain knowledge about the most efficient dosing regimens in order to minimize the emergence and selection of antibiotic-resistant mutants. We also wanted to assess the impact of antibiotic selective pressure and host to host transmission for the dissemination of resistance. Escherichia coli bacteria with different levels of cefotaxime susceptibility were competed in an in vitro kinetic model, demonstrating a complex selection of low-level resistance influenced e.g. by the time duration of selective concentrations and the rise of new mutants. We also constructed a mathematical model incorporating biologically relevant parameters and showed its usefulness when assessing the risks of resistance development. When E. coli populations with pre-existing fluoroquinolone-resistant mutants were exposed to simulated serum concentrations, several currently used doses of fluoroquinolones clearly enhanced the development and selection of resistance. The mutant prevention concentration (MPC) was measured for several E. coli isolates with different fluoroquinolone susceptibilities, and because of fluctuating antibiotic concentrations in the human body, the pharmacokinetics was considered when evaluating MPC. Results indicate that the area under the serum concentration time curve in relation to the MPC may be a useful predictor for emergence of resistance. In the commensal flora of healthy human couples we noted a high frequency of trimethoprim-resistant E. coli. There was also an extensive sharing and transmission of E. coli clones. Treating the female with trimethoprim reduced the number of intestinal E. coli which might have facilitated the transmission from the male partner. These findings suggest that the rate of transmission is high and effectively contributes to the spread of both susceptible and antibiotic-resistant E. coli in intrafamilial settings.

Nosocomial outbreak of CTX-M-15-producing E. coli in Norway

Abstract: Seven E. coli isolates expressing resistance to 3rd generation cephalosporins were recovered from blood (n=2), kidney and lung tissue (n= 1), and urinary tract (n=4) samples from seven patients hospitalised or recently discharged from the Divisions of Geriatrics and Pulmonary Medicine, Central Hospital of Rogaland, between July and September 2004. All isolates expressed a typical ESBL-cefotaximase profile (cefotaxime MIC>ceftazidime MIC) with clavulanic acid synergy. A bla CTX-M-15 genotype was confirmed in six strains that were coresistant to gentamicin, nitrofurantoin, trimethoprim-sulfamethoxazole and ciprofloxacin. A bla CTX-M-3 genotype was detected in the last strain. Xbal-PFGE patterns of the six bla CTX-M-15 isolates revealed a clonal relationship. Bla CTX-M-15 strains were also positive for the ISEcpl-like insertion sequences that have been shown to be involved in the mobilization of blac CTX-M. Further analyses revealed two bla CTX-M-15 -positive E. coli urinary isolates clonally related to the outbreak strain from two different patients at the same divisions in January and February 2004. These patients were later re-hospitalised and one had E. coli with an ESBL-cefotaximase profile in sputum and nasopharyngeal specimen during the outbreak period. Clinical evaluation suggests that the CTX-M-producing E. coli strains contributed to death in three patients due to delayed efficient antimicrobial therapy. The outbreak emphasises the epidemic potential of multiple-antibiotic-resistant CTX-M-15-producing E. coli also in a country with low antibiotic usage and low prevalence of antimicrobial resistance.

Third generation cephalosporins versus conventional antibiotics for treating acute bacterial meningitis

Abstract: Background Antibiotic therapy for suspected acute bacterial meningitis (ABM) needs to be started immediately even before the results of cerebrospinal fluid culture and antibiotic sensitivity are available. It is not clear whether the available evidence supports the choice of third generation cephalosporins over the conventional antibiotic combination of ampicillin and chloramphenicol. Immediate institution of effective treatment through intravenous route may reduce death and disability in survivors. Objectives The objective of this review is to determine the effectiveness and safety of the third generation cephalosporins and conventional treatment with penicillin/ampicillin- chloramphenicol in patients with community-acquired acute bacterial meningitis. Search strategy We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library Issue 4 2003) which contains the Cochrane Acute Respiratory Infections Group trials register MEDLINE (January 1966 to November 2003) and EMBASE (January 1990 to November 2003). We also searched the reference list of review articles and textbook chapters and contacted experts for any unpublished trials. Selection criteria Randomised controlled trials comparing ceftriaxone or cefotaxime with conventional antibiotics as empirical therapy of acute bacterial meningitis. Data collection and analysis Two independent reviewers applied the study selection criteria assessed methodological quality and extracted data. Main results Eighteen trials included 993 patients in the analysis. The kappa (chance-corrected agreement) between the observers in study selection and data extraction was substantial. There was no heterogeneity of results among the studies in any outcome except diarrhoea. There was no statistically significant difference between the groups in the risk of death (risk difference -1%; 95% confidence interval (CI) -4% to +3%) risk of deafness (risk difference -4%; 95% CI -9% to +1%) risk of treatment failure (risk difference -2%; 95% CI -5% to +2%). However there were significantly decreased risk of culture positivity of CSF after 10-48 hours (risk difference - 6%; 95% CI -11% to 0%) and statistically significant increased in the risk of diarrhoea between the groups (risk difference +8%; 95% CI +3% to +13%) with the third generation cephalosporins. The risk of neutropenia and ski rash were not significantly different between the two groups. However all the studies have been conducted in the eighties except two which have been conducted in 1993 and 1996. Authors conclusions Although the review shows no clinically important difference between ceftriaxone or cefotaxime and conventional antibiotics the studies are done decades ago and may not apply to current routine practice. However in situations where ceftriaxone or cefotaxime are not available or affordable ampicillin-chloramphenicol combination may be used as an alternative. The antimicrobial resistance pattern against various antibiotics needs to be closely monitored in developing as well as developed countries. The factors determining overuse of antibiotics in developing countries and educational interventions to limit such practice are priority area for research in developing countries. (authors)

Continuous vs. intermittent cefotaxime administration in patients with chronic obstructive pulmonary disease and respiratory tract infections: pharmacokinetics/pharmacodynamics, bacterial susceptibility and clinical efficacy

Abstract: AIM: To compare the pharmacokinetics/pharmacodynamics, antibiotic resistance and clinical efficacy of continuous (CA) vs. intermittent administration (IA) of cefotaxime in patients with obstructive pulmonary disease and respiratory infections. METHODS: A randomized controlled prospective nonblinded study was performed in 93 consecutive hospitalized patients requiring antibiotics for acute exacerbations of chronic obstructive pulmonary disease. Forty-seven patients received 2 g of cefotaxime intravenously over 24 h plus a loading dose of 1 g, and 46 patients were given the drug intermittently (1 g three times daily). RESULTS: Similar pathogens were identified in both groups, being mostly Haemophilus influenzae (51%), Streptococcus pneumoniae (21%) and Moraxella catharralis (18%). Mean minimal inhibitory concentration (MIC) values were also similar before and after treatment in both groups. Clinical cure was achieved in 37/40 (93%) (CA) vs. 40/43 (93%) (IA) of patients (P = 0.93). In microbiologically evaluable patients, criteria such as 70% of treatment time with antibiotic concentrations > or = MIC (CA 100%vs. IA 60% of patients) and/or > or = 5 x MIC (CA 100%vs. IA 55% of patients) were significantly better following continuous administration (P MIC and > 5 x MIC compared with intermittent dosing. Continuous administration of cefotaxime at a lower dose [2 g (CA) vs. 3 g (CI)] is equally effective pharmacodynamically and microbiologically, may be more cost-effective and offers at least the same clinical efficacy. Based on these observations, we recommend continuous administration of cefotaxime as the preferred mode of administration.

In vitro activity of azithromycin, newer quinolones and cephalosporins in ciprofloxacin-resistant Salmonella causing enteric fever.

Abstract: The therapeutic alternatives available for use against ciprofloxacin-resistant enteric fever isolates in an endemic area are limited. The antibiotics currently available are the quinolones, thirdgeneration cephalosporins and conventional first-line drugs. In this study, the MICs of various newer drugs were determined for 31 ciprofloxacin-resistant enteric fever isolates (26 Salmonella enterica serovar Typhi and 5 S. enterica serovar Paratyphi A). MICs for ciprofloxacin, ofloxacin, gatifloxacin, levofloxacin, cefotaxime, cefixime, cefepime and azithromycin were determined using Etest strips and the agar dilution method. By Etest, all of the ciprofloxacin-resistant isolates had ciprofloxacin MICs ¢32 m gm l ”1 . S. Typhi showed MIC90 values of 0.50, 0.25 and 0.38 m gm l ”1 for cefixime, cefotaxime and cefepime, respectively. For the cephalosporins, a negligible difference in MIC90 and MIC50 values for S. Typhi and S. Paratyphi A was observed. A single isolate of S. Typhi showed a high azithromycin MIC of 64 m gm l ”1 . The MIC90 value for azithromycin in S. Typhi and S. Paratyphi was 24 m gm l ”1 . Gatifloxacin demonstrated lower resistance (80.8%) compared with the other quinolones (92–100%) in S. Typhi. The rise in MIC levels of these antimicrobials is a matter for serious concern.

Bacteriological findings in patients with ocular infection and antibiotic susceptibility patterns of isolated pathogens.

Abstract: Introduction: Isolation of common pathogens involved in ocular infection, and their in-vitro susceptibility to commonlyused ocular antibiotics, as well as the trends in antibiotic resistance developed by these pathogens, were investigated. Methods: Corneal scrapings were obtained from 318 hospitalised patients and inoculated directly onto enriched and differential culture media. Subcultures were performed on selective media. The necessary biochemical tests were conducted and the organisms identified using standard procedures. Susceptibility of isolated pathogens to commonly-used ocular antibiotics was examined using standard susceptibility testing. Results: 70 different organisms were isolated. Gram-positive cocci accounted for 47 (67.2 percent) and gram-negative bacilli for 23 (32.8 percent) bacterial isolates. Coagulasenegative Staphylococci (33 percent) and Pseudomonas species (24 percent) were the most commonly-isolated organisms. In susceptibility testing, Gentamycin had coverage against 35 (74.5 percent) of 47 gram-positive cocci and 19 (82.6 percent) of 23 gram-negative bacilli tested. The coverage of Tetracycline, Cephalotin and Ceftriaxon against gram-positive cocci were 61.7, 55 and 53 percent, respectively. All the tested gram-positive cocci showed resistance to Cefotaxime and Penicillin. Ceftriaxon and Tobramycin had coverage against 17 (73.9 percent) and 14 (60.8 percent) of 23 gram-negative bacilli isolates, respectively. The coverage of Vancomycin against coagulase-negative Staphylococci was 100%, but all the isolates of Staphylococcus aureus were resistant to Vancomycin. Conclusion: Susceptibility analysis revealed that antibiotic with the greatest coverage was Gentamycin (77.1 percent of 54 isolates). Gentamycin also had good coverage against gram-positive cocci, which constituted the majority (67.1 percent) of ocular isolates.

Factors associated with antimicrobial resistance and mortality in pneumococcal bacteremia.

Abstract: We conducted a multicenter, retrospective cohort study of patients with Streptococcus pneumoniae bacteremia to determine factors associated with antibiotic resistance and mortality. Risk factors were identified using multivariate logistic regression. There were 1574 patients at 34 sites enrolled. Compared to isolates from patients not receiving an antibiotic before the index blood culture, patients receiving an antibiotic were less likely to harbor an antibiotic susceptible organism. Susceptibility to penicillin decreased from 78% (95% confidence interval [CI] 75-80) to 49% (95% CI 39-59); to cefotaxime/ceftriaxone, from 92% (95% CI 90-93) to 82% (95% CI 72-89); and to macrolide, from 84% (95% CI 82-87) to 55% (95% CI 41-68). Factors associated with macrolide non-susceptibility include: > 24 h of antibiotic therapy at time of the index culture (odds ratio [OR] 4.0), residing in southern U.S. (OR 1.7), and having an antibiotic allergy (OR 1.7). Harboring an antibiotic non-susceptible strain (OR 1.4) and male sex (OR 1.4) were associated with increased risk of mortality, whereas black race (OR 0.6) and evidence of focal infection (OR 0.6) were associated with decreased risk.

[Changes in the profiles of causative agents and antibiotic resistance rate for spontaneous bacterial peritonitis: an analysis of cultured microorganisms in recent 12 years].

Abstract: BACKGROUNDS/AIMS The causative agents for spontaneous bacterial peritonitis (SBP) and antibiotic resistance rate vary according to the regions and time. This study evaluated the recent changes in the profiles of microorganisms and antibiotic resistance rate for the choice of effective antibiotics in treating SBP. METHODS The clinical records of 1,018 episodes of SBP from November, 1994 to December, 2005, were analyzed retrospectively. The profiles of the causative agents for SBP and the rate of antibiotic resistance were compared in every 4-year-term. RESULTS The microorganisms were isolated in 394 out of 1018 episodes (38.7%). Gram negative and positive organisms constituted 71.6% and 21.3%, respectively. The five most commonly isolated organisms were E. coli (35.8%), K. pneumoniae (15.5%), viridans Streptococci (10.4%), S. pneumoniae (4.8%) and Aeromonas group (4.6%). The rate of E. coli resistant to cefotaxime (0%, 5.4%, 7.4%) and ciprofloxacin (4.3%, 21.6%, 28.4%) were increased in recent years. In the gram positive organisms, all isolates of viridans Streptococci and Pneumococci were sensitive to cefotaxime and ciprofloxacin. Recently, methicillin-resistant Staphylococcus aureus (MRSA) (28%) and vancomycin-resistant Enterococci (VRE) (31%) have been isolated. In each period, the overall antibiotic resistance rates to cefotaxime were 12.5%, 14.0%, 14.8%, to ciprofloxacin were 3.1%, 16.7%, 18.0%, and to imipenem were 4.7%, 7.0%, 4.2%. CONCLUSIONS Cefotaxime may still be the choice of primary empirical antibiotics for the treatment of SBP in Korea because the rate of resistance is acceptable. However, it is important to be aware of the recent increase in ciprofloxacin-resistant E. coli, extended spectrum beta-lactamase (ESBL)-producing gram negative bacilli, MRSA and VRE.

Pseudomonas aeruginosa: freqüência de resistência a múltiplos fármacos e resistência cruzada entre antimicrobianos no Recife/PE

Abstract: BACKGROUND AND OBJECTIVES: The frequency of multiple-antibiotic resistant bacteria has been increasing in recent years. Among the gram-negative bacteria Pseudomonas aeruginosa (P. aeruginosa) shows a great propensity for the development of multidrug resistance mechanisms. The objective of this study was to identify the profile of susceptibility to antibiotics, the frequency of multidrug resistance and the cross-resistance between drugs of P. aeruginosa strains in two tertiary hospitals in Recife, Pernambuco. METHODS: The study was carried out between September 2004 and January 2006. The antimicrobial susceptibility testing was performed in 304 strains of P. aeruginosa by the disc diffusion method in accordance with National Committee for Clinical and Laboratory Standards (NCCLS) guidelines. RESULTS: The most frequent materials were urine (26.7%) and respiratory tract secretion (26.1%) The antibiotics tested and their respective susceptibilities were as follows: piperacillin-tazobactam (66.2%); aztreonam (59.8%); amikacin (59.4%); meropenem (58.2%); imipenem (57.7%); ciprofloxacin (49.7%); gentamicin and cefepime (48.6%); ceftazidime (30%) and cefotaxime (6.8%). A high prevalence of multi-resistance was detected. Half (49.7%) the strains showed resistance to three or more antibiotics and 28% were resistant to six antimicrobials or more. Also, cross-resistance between the beta-lactams (carbapenems and piperacilin/tazobactam) and aminoglicosides and quinolones was between 22.9% and 38.1%. These drugs are commonly combined in the treatment of severe infections caused by Pseudomonas, which reflects the difficulty in choosing the appropriate option for combination therapy. CONCLUSIONS: The frequency of multidrug-resistant strains of P. aeruginosa in this study was similar to other hospitals in Brazil and higher than in other countries. In order to reduce the frequency of these multiresistant clones, epidemiologic surveillance and the rational use of antibiotic protocols need to be urgently implemented.

First detection and sequence analysis of the bla-CTX-M-15 gene in Lebanese isolates of extended-spectrum-β-lactamase-producing Shigella sonnei

Abstract: The emergence in Shigella species of extended-spectrum beta-lactamases (ESBL) that impart resistance to third-generation cephalosporins is a growing concern world-wide. So far, however, ESBL-producing Shigella have only been reported seven times, albeit from seven different countries. In Lebanon, three ESBL-producing clinical isolates of S. sonnei were recovered from 30 cases of shigellosis diagnosed between July 2004 and October 2005. All three were found to be resistant to amoxycillin, cefotaxime, ceftazidime, aztreonam, trimethoprim/sulphamethoxazole, gentamicin, and kanamycin. Each harboured the bla-CTX-M gene, and the results of sequence analysis indicated this to be of the bla-CTX-M-15 type and encoded on a 70-kb plasmid, flanked by an insertion element (ISEcp1). The bla-TEM-1 gene was also detected on the chromosomes of two of the ESBL-producing isolates. Class-2 integrons containing dhfr1, aadA1 and sat1 genes were detected on the chromosomes of all three isolates but not on the plasmids. Fluoroquinolone-modifying factors [QnrA, QnrB, QnrS or AAC(6')-Ib-cr] were not detected. The results of RAPD analysis, combined with data on antimicrobial susceptibility, indicated that each isolate was unique. In conclusion, the emergence of ESBL-producing isolates of S. sonnei has been demonstrated for the first time in Lebanon. The resistance of these isolates to third-generation cephalosporins was mediated by the CTX-M-15 enzyme, which was plasmid-encoded.

In vitro interactions of LytA, the major pneumococcal autolysin, with two bacteriophage lytic enzymes (Cpl-1 and Pal), cefotaxime and moxifloxacin against antibiotic-susceptible and -resistant Streptococcus pneumoniae strains

Abstract: Objectives: In an innovative therapeutic exploitation against antibiotic-resistant Streptococcus pneumoniae, here we have evaluated the in vitro activity of a purified bacterially-encoded cell wall lytic enzyme, LytA (the major pneumococcal autolysin), and compared it with those of Cpl-1 and Pal (pneumococcal phage lytic enzymes) and two antibiotics versus four pneumococcal strains. Methods: Two serotype 3, penicillin-susceptible strains and two penicillin-resistant (serotypes 19F and 19A, respectively) S. pneumoniae clinical isolates were used. The effect of several combinations of lytic enzymes and antibiotics (cefotaxime and moxifloxacin) was studied by chequerboard and time-kill assays, the latter at concentrations of 0.25 x MIC. Results: LytA was more active than Cpl-1 and Pal. By the chequerboard technique, the combination of LytA and cefotaxime was synergistic for one of the two cefotaxime-resistant strains studied. The combined use of Cpl-1 and Pal was synergistic for three of the four strains, as was Cpl-1 with antibiotics for two of the three strains studied. In the time-kill assays, after 5 h of exposure to LytA, Cpl-1 or Pal, the mean differences in colony counts versus controls were -3.55, -2.66 and -2.71 log 10 cfu/mL, respectively. The combination of LytA/Pal reduced the bacterial inoculum >2 log units for three of the four strains. LytA combined with cefotaxime or moxifloxacin achieved >3 log units decrease for the strains tested. Particularly, a strong synergism was observed with LytA/cefotaxime for one cefotaxime-resistant meningeal strain. LytA/moxifloxacin was synergistic for the quinolone-resistant strain when tested by time-kill methodology, and just close to synergistic (fractional inhibitory concentration index of 0.58) by the chequerboard technique. Antagonism was not observed for any combination when assayed by either method. Conclusions: LytA, Cpl-1 or Pal, alone or in combination, might prove to be effective in combination therapy, as well as in monotherapy against S. pneumoniae. These results suggest avenues of research to study the cell wall lytic enzymes as anti-pneumococcal therapeutic agents.

Role of β-lactamase inhibitors in enterobacterial isolates producing extended-spectrum β-lactamases

Abstract: OBJECTIVES: To determine the in vitro activity of beta-lactamase inhibitors (clavulanic acid and sulbactam) in combination with third-generation cephalosporins and monobactam against extended-spectrum beta-lactamase (ESBL)-producing members of the Enterobacteriaceae family. METHODS: A total of 361 ESBL-producing enterobacterial isolates obtained from patients of a university hospital were screened for the status of co-production of AmpC beta-lactamase. These strains were further subjected to an MIC study using third-generation cephalosporins and monobactam, and reductions were observed after combining with beta-lactamase inhibitors at a fixed concentration of 4 mg/L. RESULTS: Most of the isolates showed 8-fold reduction with sulbactam when combined with ceftriaxone, cefpodoxime and cefotaxime but not with ceftazidime and aztreonam, whereas clavulanic acid showed the same result with all the cephalosporins tested. Further, both the inhibitors showed greater reduced MIC when combined with aztreonam. CONCLUSIONS: As the ability of clavulanic acid to induce AmpC production may interfere with ESBL detection, sulbactam is likely to be preferred over clavulanic acid after standardization of an appropriate concentration for ESBL detection in the scenario of increased prevalence of AmpC producers. Greater in vitro activity of these inhibitors when combined with aztreonam further indicates the need of studies to evaluate these combination antimicrobials in clinical settings as they can play a significant role for clinicians as viable alternatives to treat infections caused by such organisms.

Prevalence of fecal carriage of ESBL-producing Enterobacteriaceae in hospitalized and ambulatory patients during two non-outbreak periods.

Abstract: Beta-lactam resistance in Enterobacteriaceae associated with plasmid-mediated extended-spectrum beta-lactamase (ESBL) has become a worldwide problem [1]. ESBLs were initially associated with nosocomial outbreaks caused by strains producing single enzymes, but recent studies have revealed a more complex situation, with a significant increase among community isolates [2]. The rate of fecal carriage of ESBL-producing bacterial isolates in nosocomial outbreaks has been studied previously [3, 4], but few prospective studies investigating the prevalence of fecal carriage during non-outbreak periods have been conducted [5, 6]. In an effort to fill this knowledge gap, we performed a study of hospitalized patients and outpatients to determine the prevalence of fecal carriage of ESBL-producing Enterobacteriaceae in stool samples submitted to our laboratory for culture during two non-outbreak periods separated by 17 months (April 2002–February 2003 and August 2004– July 2005). A total of 7,065 and 7,686 fecal samples from 4,676 and 4,708 patients were analyzed in each period, respectively. Ambulatory patients accounted for 75.5 and 70% of the total in each respective period. The samples were cultured using standard methods for Salmonella, Shigella, Campylobacter, Yersinia, Aeromonas and Plesiomonas. In 13.8% of all stool cultures collected during both periods, other nonCampylobacter strains belonging to the family Enterobacteriaceae were isolated. These grew in modified charcoal-cefazolin-deoxycholate agar containing cefoperazone 32 mg/l and amphotericin B supplement (Oxoid, Basingstoke, UK) incubated for 48 h under microaerobic conditions—a method used routinely to isolate Campylobacter spp in our laboratory. All of the non-Campylobacter strains that grew in the medium containing cefoperazone were identified according to conventional methods [7] and screened for production of ESBL by identification of the resistance phenotype and using the double-disk synergy test with cefotaxime, ceftazidime, cefepime, aztreonam and amoxicillin-clavulanic acid [8]. Results were confirmed by determining the MICs using the E-test (AB Biodisk, Solna, Sweden) with cefotaxime/cefotaxime-clavulanic acid, ceftazidime/ceftazidime-clavulanic acid and cefepime/cefepime-clavulanic acid. Strains producing ESBL were defined as strains showing synergism between clavulanic acid and cefotaxime, ceftazidime, cefepime and/or aztreonam [9]. All strains suspected of having a resistance pattern compatible with hyperproduction of the chromosomal enzymes as well as resistant strains without synergy were excluded from the study. Of the enterobacteria isolated in the modified charcoalcefazolin-deoxycholate agar, 16.3 and 26.76% (105 of 643 and 349 of 1,304 in each period, respectively) were ESBLproducing strains. Statistical significance was calculated for comparison of proportions using the chi-square test, and a p value of <0.05 was considered statistically significant (SPSS V 12.0; SPSS, Chicago, IL, USA). The rates of fecal carriage of ESBL-producing strains belonging to the Enterobacteriaceae family increased dramatically in our area from 2.3% (105 of 4,676 patients) in 2002 to 7.4% (349 of 4,708 patients) in 2004 (p<0.001). Eur J Clin Microbiol Infect Dis (2007) 26:77–78 DOI 10.1007/s10096-006-0242-8

CTX-M Extended-spectrum β-Lactamases, Washington State

Abstract: To the Editor: The CTX-M–type β-lactamases are non-TEM and non-SHV plasmid-mediated, class A, extended-spectrum β-lactamases (ESBLs). The CTX-M–type β-lactamases have recently emerged as the most common type of ESBLs, with a global distribution (1). In contrast, the CTX-M–type ESBLs are rarely reported in the United States and have not been identified in pathogens isolated from infected patients with gastroenteritis. We screened 637 Salmonella and 126 Shigella isolates, collected in the state of Washington during 2003–2004, for CTX-M–type β-lactamases. Of these, 60 Salmonella isolates that exhibited an ESBL phenotype were further characterized by PCR for TEV, SHV, CTM-X, and CMY. All were positive for the CMY-2 or TEM-1 β-lactam genes. One Shigella sonnei isolate (WA7593), cultured from a fecal specimen in August 2004, tested positive with an ESBL confirmatory disk diffusion panel (ceftazidime 24 mm, ceftazidime/clavulanate 32 mm, cefotaxime 14 mm, and cefotaxime/clavulanate 34 mm; [2]). The patient had recently traveled to Pakistan and likely became ill there and returned to the United States while still sick. The transfer of extended-spectrum cephalosporin resistance was tested by conjugation to Escherichia coli J53 aziR (3). The MIC for S. sonnei WA7593 and its transconjugant, WA7593TC1, were tested by using the E-test (AB Biodisk, Solna, Sweden). Both strains were resistant to cefotaxime and susceptible to ceftazidime and showed almost the same antimicrobial susceptibility patterns as β-lactam antimicrobial drugs (Table). Table MICs of antimicrobial drugs for Shigella sonnei clinical isolate WA7593 and its transconjugant WA7593TC1 The type of ESBL produced by these strains was determined by using PCR specific for TEM and CTX-M (4,5). Both strains were PCR positive for TEM and CTX-M. The TEM type PCR products were then sequenced and identified as TEM-1; no variation was found on the promoter region of blaTEM-1. The entire sequence of bla CTX-M from WA7593 was then sequenced (1), and the product showed 100% homology with blaCTX-M-15 (GenBank accession no. {"type":"entrez-nucleotide","attrs":{"text":"AY960984","term_id":"63029819","term_text":"AY960984"}}AY960984). The mobile element associated with the transfer of blaCTX-M-15 was investigated by sequencing the flanking regions. PCRs were performed with primers from the internal regions of bla CTX-M gene and primers for insertion sequences ISEcp1 and IS903 (4,5). Positive PCR products were obtained with primers ISEcp1F and CTX2 (943 bp); no amplified product was produced with primers CTX1 and IS903R. Sequencing of a 943-bp amplicon showed that blaCTX-M15 was flanked upstream by an ISEcp1-like element. The presence of an integron in S. sonnei WA7593 and WA7593TC1 was investigated by using integron-specific primers hep35 and hep36 (2). Only S. sonnei WA7593 produced a PCR product. This finding suggests that the transmission of blaCTX-M15 is not by integron-mediated transfer. A further 162 Shigella spp. and 260 Salmonella spp. isolated from 2003 through 2005 were also screened for ESBL production; no further isolates were identified. The presence of a CTX-M–type, ESBL-producing isolate is rarely reported in the United States. The only other reference was from a multistate study in 2001–2002 that identified CTX-M type from E. coli isolates from urine, sputum, and blood (6). No further reports about CTX-M–producing organisms have been disseminated. Our investigation suggests that CTX-M–type ESBLs may spread throughout the United States through infected travelers. This finding is notable because S. sonnei is a common enteric pathogen. Our results further emphasize that travelers from others parts of the world can introduce highly mobile and clinically important resistance mechanisms into the community. The spread of CTX-M ESBLs may be faster and more widespread than previously thought; therefore, CTX-M type should be taken seriously as a surveillance target in the United States, especially in patients with a history of travel outside North America.