Showing papers on "Klebsiella pneumoniae published in 1997"

Imipenem resistance in Klebsiella pneumoniae is associated with the combination of ACT-1, a plasmid-mediated AmpC beta-lactamase, and the foss of an outer membrane protein.

Abstract: Six Escherichia coli and 12 Klebsiella pneumoniae isolates from a single hospital expressed a common beta-lactamase with a pI of approximately 9.0 and were resistant to cefoxitin and cefotetan (MIC ranges, 64 to > 128 and 16 to > 128 micrograms/ml, respectively). Seventeen of the 18 strains produced multiple beta-lactamases. Most significantly, three K. pneumoniae strains were also resistant to imipenem (MICs, 8 to 32 micrograms/ml). Spectrophotometric beta-lactamase assays with purified enzyme indicated hydrolysis of cephamycins, in addition to cephaloridine and benzylpenicillin. The 4ene encoding the pI 9.0 beta-lactamase (designated ACT-1 for AmpC type) was cloned and sequenced, which revealed an ampC-type beta-lactamase gene that originated from Enterobacter cloacae and that had 86% sequence homology to the P99 beta-lactamase and 94% homology to the partial sequence of MIR-1. Southern blotting revealed that the gene encoding ACT-1 was on a large plasmid in some of the K. pneumoniae strains as well as on the chromosomes of all of the strains, suggesting that the gene is located on an easily mobilized element. Outer membrane protein profiles of the K. pneumoniae strains revealed that the three imipenem-resistant strains were lacking a major outer membrane protein of approximately 42 kDa which was present in the imipenem-susceptible strains. ACT-1 is the first plasmid-mediated AmpC-type beta-lactamase derived from Enterobacter which has been completely sequenced. This work demonstrates that in addition to resistance to cephamycins, imipenem resistance can occur in K. pneumoniae when a high level of the ACT-1 beta-lactamase is produced in combination with the loss of a major outer membrane protein.

Comparison of screening methods for detection of extended-spectrum beta-lactamases and their prevalence among blood isolates of Escherichia coli and Klebsiella spp. in a Belgian teaching hospital.

Abstract: Using a set of 33 well-defined extended-spectrum beta-lactamase (ESBL)-producing strains of Escherichia coli and Klebsiella pneumoniae, we compared three screening methods for ESBL detection: (i) a double-disk synergy test, (ii) a three-dimensional test (both the double-disk synergy test and the three-dimensional test were performed with ceftriaxone, ceftazidime, aztreonam, and cefepime), and (iii) the Etest ESBL screen (AB Biodisk, Solna, Sweden), based on the recognition of a reduction in the ceftazidime MIC in the presence of clavulanic acid. In the double-disk test, all four indicator antibiotics scored equally and 31 of the 33 reference strains were recognized. In the three-dimensional test, ceftriaxone was the only satisfactory indicator and 30 ESBL-positive strains were detected by this antibiotic. Both systems produced two false-positive results with cefepime. With the Etest ESBL screen, 15 of 16 TEM-related and 11 of 16 SHV-related ESBL-producing strains scored positive. In 10 cases the clavulanic acid on one end of the strip interfered with the MIC determination for ceftazidime, which was read on the opposite end. This MIC had to be determined with an extra ceftazidime-only strip. No false-positive results were noted. Eighty-six blood isolates of E. coli and Klebsiella species were screened for ESBL expression by the double-disk and three-dimensional tests, both with ceftriaxone. Six strains with suspicious antibiogram phenotypes also gave positive results by the double-disk test. One E. coli strain remained undetected by the three-dimensional test. Identification of the enzymes suspected of being ESBLs by isoelectric focusing (all strains) and DNA sequencing (1 strain) confirmed the screening test results except for one Klebsiella oxytoca strain, which proved to be a hyperproducer of its chromosomal enzyme and which also had a negative Etest score. The five true ESBL producers were all confirmed by the Etest ESBL screen. Pulsed-field gel electrophoresis proved that the E. coli strains were unrelated, but that two of the three K. pneumoniae strains were closely related.

Nitric oxide is required for effective innate immunity against Klebsiella pneumoniae.

Abstract: Nitric oxide (NO) has been associated with protection against various parasitic and viral infections and may play a similar role in bacterial infections. We studied the role of NO in host defense against Klebsiella pneumoniae infection in the lung. Initial studies demonstrated a time-dependent increase in NO production of the lungs of CBA/J mice following the intratracheal administration of K. pneumoniae (7 x 10(2) CFU). To assess the role of NO in Klebsiella pneumonia, mice were treated intraperitoneally with either L-NAME (N-omega-nitro-L-arginine methylester), a competitive inhibitor of NO synthesis, or D-NAME, an inert enantiomer. The treatment of Klebsiella-infected mice with L-NAME resulted in a 10- and 46-fold increase in K. pneumoniae CFU in lungs and blood, respectively, at 48 h post-K. pneumoniae inoculation compared to treatment of mice with D-NAME. In addition, a greater-than-twofold increase in mortality was evident in L-NAME-treated mice compared to the mortality in control animals. No significant difference in bronchoalveolar lavage inflammatory cell profiles was noted between L-NAME- and D-NAME-treated mice with Klebsiella pneumonia. Interestingly, increased levels of tumor necrosis factor, gamma interferon, macrophage inflammatory protein 1alpha (MIP-1alpha), and MIP-2 mRNA and protein were noted in infected mice treated with L-NAME compared to the levels in mice treated with D-NAME. Importantly, the in vitro incubation of murine alveolar macrophages with L-NAME, but not with D-NAME, resulted in a significant impairment in both the phagocytosis and killing of K. pneumoniae. In total, these results suggest that NO plays a critical role in antibacterial host defense against K. pneumoniae, in part by regulating macrophage phagocytic and microbicidal activity.

Substitution of alanine for aspartate at position 179 in the SHV‐6 extended‐spectrum β‐lactamase

Abstract: SHV-6 was previously identified by its susceptibility pattern and biochemical criteria in a clinical isolate of Klebsiella pneumoniae which was resistant to ceftazidime. It contains only a single point difference with the βlaSHV-1 gene as determined by PCR amplification and nucleotide sequencing. This is the result of a single amino acid substitution, Ala for Asp, at position 179. Directed mutagenesis experiments have shown this substitution to confer selective resistance to ceftazidime in the TEM family.

Spatial Distribution and Coexistence of Klebsiella pneumoniae and Pseudomonas aeruginosa in Biofilms

Abstract: The heterotrophic bacteria Klebsiella pneumoniae and Pseudomonas aeruginosa stably coexisted in laboratory-grown biofilms, even though the growth rate of K. pneumoniae was twice that of P. aeruginosa under planktonic growth conditions. The failure of K. pneumoniae to displace P. aeruginosa from the biofilm could not be attributed to concentration gradients of the limiting nutrient (glucose) arising from the interaction of reaction and diffusion. Comparisons of the growth rates of the two species in mono- and binary-population biofilms suggested partial segregation of the two species in the latter. We used a fluorescently labeled monoclonal antibody to examine the spatial distribution of K. pneumoniae in frozen cross sections of biofilm to confirm this segregation. K. pneumoniae microcolonies resided on top of, or intermixed with, a base film of P. aeruginosa. We hypothesize that microscale structural heterogeneity and differing rates of bacterial attachment and detachment of the two species are responsible for coexistence in this system.

Invasion of cultured human epithelial cells by Klebsiella pneumoniae isolated from the urinary tract.

Abstract: The mechanisms which enable entry into cultured human epithelial cells by Klebsiella pneumoniae were compared with those of Salmonella typhi Ty2. K. pneumoniae 3091, isolated from a urine sample of a patient with a urinary tract infection, invaded human epithelial cells from the bladder and ileocecum and persisted for days in vitro. Electron microscopic studies demonstrated that K. pneumoniae was always contained in endosomes. The internalization mechanism(s) triggered by K. pneumoniae was studied by invasion assays conducted with different inhibitors that act on prokaryotic and eukaryotic cell structures and processes. Chloramphenicol inhibition of bacterial uptake revealed that bacterial de novo protein synthesis was essential for efficient invasion by K. pneumoniae and S. typhi. Interference with receptor-mediated endocytosis by g-strophanthin or monodansylcadaverine and inhibition of endosome acidification by monensin reduced the number of viable intracellular K. pneumoniae cells, but not S. typhi cells. The depolymerization of microfilaments by cytochalasin D inhibited the uptake of both bacteria. Microtubule depolymerization caused by colchicine, demecolcine, or nocodazole and the stabilization of microtubules with taxol reduced only the invasion ability of K. pneumoniae. S. typhi invasion was unaffected by microtubule depolymerization or stabilization. These data suggest that the internalization mechanism triggered by K. pneumoniae 3091 is strikingly different from the solely microfilament-dependent invasion mechanism exhibited by many of the well-studied enteric bacteria, such as enteroinvasive Escherichia coli, Salmonella, Shigella, and Yersinia strains.

Alterations in the GyrA subunit of DNA gyrase and the ParC subunit of topoisomerase IV in quinolone-resistant clinical isolates of Klebsiella pneumoniae.

Abstract: We determined a partial sequence of the Klebsiella pneumoniae parC gene, including the region analogous to the quinolone resistance-determining region of the Escherichia coli gyrA gene, and examined 26 clinical strains of K. pneumoniae for an association of alterations in GyrA and ParC with susceptibilities to quinolones. The study suggests that in K. pneumoniae DNA gyrase is a primary target of quinolones and that ParC alterations play a complementary role in the development of higher-level fluoroquinolone resistance.

Evidence of interhospital transmission of extended-spectrum beta-lactam-resistant Klebsiella pneumoniae in the United States, 1986 to 1993. The National Nosocomial Infections Surveillance System.

Abstract: Background In addition to single-hospital outbreaks, interhospital transmission of extended-spectrum beta-lactam-resistant (ESBLR) Klebsiella pneumoniae has been suspected in some reports. However, these studies lacked sufficient epidemiological information to confirm such an occurrence. Methods We reviewed the surveillance data reported to the National Nosocomial Infections Surveillance (NNIS) System during 1986 to 1993 for K pneumoniae isolates and their susceptibility to either ceftazidime, cefotaxime, ceftriaxone, or aztreonam. Pulsed-field gel electrophoresis (PFGE) was used to study available ESBLR K pneumoniae isolates. Results Among 8,319 K pneumoniae isolates associated with nosocomial infections, 727 (8.7%) were resistant or had intermediate-level resistance to at least one of these antibiotics. One hospital (hospital A) accounted for 321 isolates (44.2%) of ESBLR K pneumoniae. During 1986 to 1993, the percentage of K pneumoniae isolates that were ESBLR increased from 0 to 57.7% in hospital A, from 0 to 35.6% in NNIS hospitals 0 to 20 miles from hospital A (area B), and from 1.6 to 7.3% in NNIS hospitals more than 20 miles from hospital A, including hospitals located throughout the United States. Analysis of PFGE restriction profiles showed a genetic relationship between a cluster of isolates from hospital A and some isolates from one hospital in area B, and consecutive admission in these two hospitals was confirmed for two patients from whom isolates were available. Conclusions These data provide evidence of interhospital transmission of ESBLR K pneumoniae in one region of the United States and stress the interrelationship between hospitals when trying to control antimicrobial resistance.

Evidence of Interhospital Transmission of Extended-Spectrum β-Lactam-Resistant Klebsiella pneumoniae in the United States, 1986 to 1993

Abstract: Background: In addition to single-hospital outbreaks, interhospital transmission of extended-spectrum β-lactam-resistant (ESBLR) Klebsiella pneumoniae has been suspected in some reports. However, these studies lacked sufficient epidemiological information to confirm such an occurrence. Methods: We reviewed the surveillance data reported to the National Nosocomial Infections Surveillance (NNIS) System during 1986 to 1993 for K pneumoniae isolates and their susceptibility to either ceftazidime, cefotaxime, ceftriaxone, or aztreonam. Pulsed-field gel electrophoresis (PFGE) was used to study available ESBLR K pneumoniae isolates. Results: Among 8,319 K pneumoniae isolates associated with nosocomial infections, 727 (8.7%) were resistant or had intermediate-level resistance to at least one of these antibiotics. One hospital (hospital A) accounted for 321 isolates (44.2%) of ESBLR K pneumoniae . During 1986 to 1993, the percentage of K pneumoniae isolates that were ESBLR increased from 0 to 57.7% in hospital A, from 0 to 35.6% in NNIS hospitals 0 to 20 miles from hospital A (area B), and from 1.6 to 7.3% in NNIS hospitals more than 20 miles from hospital A, including hospitals located throughout the United States. Analysis of PFGE restriction profiles showed a genetic relationship between a cluster of isolates from hospital A and some isolates from one hospital in area B, and consecutive admission in these two hospitals was confirmed for two patients from whom isolates were available. Conclusions: These data provide evidence of interhospital transmission of ESBLR K pneumoniae in one region of the United States and stress the interrelationship between hospitals when trying to control antimicrobial resistance.

Efficacies of piperacillin-tazobactam and cefepime in rats with experimental intra-abdominal abscesses due to an extended-spectrum beta-lactamase-producing strain of Klebsiella pneumoniae.

Abstract: The in vivo activities of piperacillin-tazobactam and cefepime were compared with those of ticarcillin-clavulanate, ceftazidime, cefotaxime, and imipenem in a rat model of intra-abdominal abscess with a strain of Klebsiella pneumoniae elaborating an extended-spectrum beta-lactamase (TEM-26). With the exception of ceftazidime, all of the antimicrobial agents significantly reduced bacterial counts within abscesses at the end of therapy compared with those in untreated controls. Residual viable cell counts (mean +/- standard deviation in log10 CFU/gram) were as follows: control, 8.76 +/- 0.97; ceftazidime, 8.00 +/- 0.76; piperacillin-tazobactam, 3.87 +/- 1.72; ticarcillin-clavulanate, 3.74 +/- 1.34; cefepime, 3.15 +/- 1.19; cefotaxime, 2.61 +/- 0.77; imipenem, 2.41 +/- 0.93. Imipenem was more effective than either of the inhibitor combinations (P < 0.05). Cefotaxime was unexpectedly effective given its poor in vivo activity against this organism in our earlier studies, which used a different dose and total duration of therapy (L. B. Rice, J. D. C. Yao, K. Klimm, G. M. Eliopoulos, and R. C. Moellering, Jr., Antimicrob. Agents Chemother. 35:1243-1244, 1991). These observations suggest that the effectiveness of cephalosporins in the treatment of experimental infections caused by extended-spectrum beta-lactamase-producing K. pneumoniae may be highly dependent on dosing regimens, even for a specific organism and site of infection.

Clinical, bacteriological, and serological aspects of Klebsiella infections and their spondylarthropathic sequelae.

Abstract: Since Friedlander in 1883 first demonstrated capsulated rodshaped bacteria in the lungs of patients dying of pneumonia, Klebsiella has been known to physicians primarily as the pathogencausing“Friedlander’spneumonia.”Theproductionofenormous amounts of capsular polysaccharides in vivo as well as on agar medium is characteristic of bacteria of this genus and is unique among the members of the family Enterobacteriaceae, to which Klebsiella belongs. Despite the discovery of other virulence factors such as fimbriae, siderophores, and O antigens (104), the efforts to clarify the pathogenic mechanisms of Klebsiella mainly focus on their capsular antigens, which are considered to be the ultimate determinants of their pathogenicity. Thus, Klebsiella is regarded as a paradigm for systemic infections caused by capsulated bacteria. In contrast to other capsulated pathogens such as Streptococcus pneumoniae and Haemophilus influenzae, however, Klebsiella spp. are not closely adapted and restricted to the host habitat but are rather widespread in nature and can be found in water and soil as well as on plants.

Binding of the type 3 fimbriae of Klebsiella pneumoniae to human endothelial and urinary bladder cells.

Abstract: Binding of the two identified type 3 fimbrial variants of Klebsiella pneumoniae to human endothelial EA-hy926 and bladder T24 cells was assessed. The recombinant Escherichia coli strain LE392(pFK12), expressing plasmid-encoded type 3 fimbriae of K. pneumoniae, adhered to both cell lines, and the fimbriae purified from the strain bound to both cell lines in a dose-dependent manner. Adhesiveness to both cell lines of chromosomally encoded type 3 fimbriae from K. pneumoniae IApc35 was lower. No binding was detected with type 1 fimbriae of K. pneumoniae. Both type 3 fimbrial variants exhibited a significantly lower affinity for the cell lines than did S fimbriae of meningitis-associated E. coli.

Antibody responses to gut bacteria in ankylosing spondylitis, rheumatoid arthritis, Crohn's disease and ulcerative colitis

Abstract: Specific immunoreactive anti-Klebsiella antibodies are found in patients with ankylosing spondylitis (AS), a significant proportion of whom have occult inflammatory bowel disease. Molecular mimicry between Klebsiella or other bacterial antigens and HLA-B27 has been suggested in the pathogenesis of AS. The specificity of increased immunoreactivity against Klebsiella remains to be assessed against the abundant anaerobic bacterial flora, present either in healthy controls or in patients with ulcerative colitis (UC) and Crohn's disease (CD). Total immunoglobulin (Ig; IgG, IgA, IgM) immunoreactivity was measured by ELISA against Klebsiella pneumoniae, Proteus mirabilis, Escherichia coli and ten anaerobic isolates of the predominant normal bowel flora in 35 patients with active AS, 60 patients with inflammatory bowel disease (30 CD, 30 UC), 60 patients with active rheumatoid arthritis (RA) and 60 healthy controls. Ig immunoreactivity to K. pneumoniae was significantly elevated in AS (P < 0.001), CD (P < 0.001) and UC (P < 0.001) patients compared with RA patients and healthy controls. Furthermore, Ig immunoreactivity to P. mirabilis was significantly elevated only in RA patients, compared with the other inflammatory groups (P < 0.001) and controls (P < 0.001). There was no significant antibody response against E. coli or the ten obligate anaerobes in any of the test groups. The data suggested an increased immune response to Klebsiella in patients with AS, UC, CD and to Proteus in patients with RA. The specificity of these responses in some patients supported a possible role for enteric Klebsiella in the pathogenesis of AS and Proteus in RA. The role of Klebsiella in inflammatory bowel disease requires further study.

Extended spectrum beta-lactamase mediated resistance to third generation cephalosporins in Klebsiella pneumoniae in Nagpur, central India.

Abstract: Out of 66 clinical isolates of Klebsiella pneumoniae, 17 showed resistance or decreased susceptibility to third generation cephalosporins (17 to cefotaxime, 16 to ceftriaxone, and 9 to ceftazidime) while the remaining 49 were sensitive by the disc diffusion method. The minimum inhibitory concentrations (MICs) of the third generation cephalosporins (3GC) for the strains ranged from 2-128 micrograms/ml by agar dilution method. Their sensitive phenotypes had zone diameters smaller (mean difference 3. 1 mm for ceftriaxone, and 6.5 mm for ceftazidime), and MICs > 10 fold higher than the corresponding values in the fully sensitive isolates. Resistance to cefotaxime was transferred to recipient Escherichia coli K12 strain in 15 isolates. All the resistant isolates were sensitive to imipenem but were variably sensitive to aminoglycosides, and quinolones. In all 17 resistant isolates extended spectrum beta-lactamase (ES beta L) was detected. The sensitivity testing systems may fail to recognise the potential ES beta L mediated resistance to 3GC. Hence ES beta L detection should be routinely undertaken.

A novel class C beta-lactamase (FOX-2) in Escherichia coli conferring resistance to cephamycins.

Abstract: An Escherichia coli strain resistant to a broad spectrum of beta-lactams, including cephamycins, was isolated from a patient suffering from urinary tract infection. A resistance plasmid (pMVP-7) was transferred from the clinical isolate to an Escherichia coli recipient. Both strains produce a cefoxitin-hydrolyzing beta-lactamase focusing at pI 6.7. The phenotype was similar to that of a Klebsiella pneumoniae strain producing cephamycinase FOX-1, so primers were selected from the FOX-1 sequence to amplify the bla gene of the transconjugant. The PCR product obtained was sequenced. The percentage of identity of the deduced amino acid sequence with sequences of other AmpC-type beta-lactamases was 96.9% with FOX-1, 74.9% with CMY-1, and 67.7% with MOX-1. This new plasmid-mediated enzyme is most closely related to FOX-1 (11 amino acid exchanges). We therefore propose the designation FOX-2.

The Klebsiella pneumoniae cytochrome bd' terminal oxidase complex and its role in microaerobic nitrogen fixation.

Abstract: Cytochrome bd' has been implicated in having an important role in microaerobic nitrogen fixation in the enteric bacterium Klebsiella pneumoniae, where it is expressed under all conditions that permit diazotrophy. In this paper the sequence of the genes encoding this terminal oxidase (cydAB) of Klebsiella pneumoniae and the characterization of a cyd mutant are reported. The deduced amino acid sequences support the proposal that His 19, His 186 and Met 393 provide three of the four axial ligands to the Fe of the three haems in the oxidase complex. The nitrogen-fixing ability of the mutant was severely impaired in the presence of low concentrations of oxygen compared with the wild-type bacterium. Only the wild-type organism was capable of microaerobic nitrogenase activity supported by fermentation products. It is proposed that formate dehydrogenase-O may be involved in supplying electrons to a respiratory chain terminated by the bd-type oxidase, which would remove inhibitory oxygen and supply ATP for nitrogenase activity.

Comparative in vitro activities of carbapenem L-749,345 and other antimicrobials against multiresistant gram-negative clinical pathogens.

Abstract: Carbapenems L-749,345 and imipenem had the lowest MICs at which 90% of isolates were inhibited (0.5 microg/ml) of 14 antimicrobial agents tested against 76 multiresistant gram-negative clinical isolates with TEM- or SHV-type extended-spectrum beta-lactamases and chromosomal or plasmid-determined AmpC beta-lactamases, but the MIC of L-749,345 for one isolate of Klebsiella pneumoniae was 16 microg/ml.

In vivo selection of Klebsiella pneumoniae strains with enhanced quinolone resistance during fluoroquinolone treatment of urinary tract infections.

Abstract: We report two cases of failure of fluoroquinolone treatment of urinary tract infections with Klebsiella pneumoniae strains harboring quinolone resistance-associated alterations in GyrA and ParC and in vivo selection of posttreatment isolates with enhanced fluoroquinolone resistance. Active efflux leading to decreased accumulation of a drug enhanced fluoroquinolone resistance in one posttreatment isolate, and an additional mutation in parC resulting in an additional amino acid change in ParC was associated with increased resistance in the other.

An allelic variant of the chromosomal gene for class A beta-lactamase K2, specific for Klebsiella pneumoniae, is the ancestor of SHV-1.

Abstract: Fecal Klebsiella isolates from neonates in 22 Swedish special care units were examined by a PCR we developed for detection of the SHV-1 beta-lactamase gene. All 105 K. pneumoniae isolates and all 11 K. pneumoniae reference strains (including the K. pneumoniae subsp. pneumoniae, ozaenae, and rhinoscleromatis type strains) tested were positive, whereas all 67 K. oxytoca isolates and the K. oxytoca, K. planticola, and K. terrigena type strains tested were negative. Resistance to beta-lactams in K. pneumoniae was not transferable by conjugation, and the beta-lactamase gene was never found on a plasmid. Southern blot analysis showed that the gene had a defined chromosomal location. Isoelectric focusing and sequencing of 231-bp PCR amplicons from different isolates revealed many variants of the enzyme, with the two main groups being SHV-1 like (pI 7.6; 68 isolates) and LEN-1 like (pI 7.1; 14 isolates). Clavulanic acid markedly reduced the MICs of ampicillin for all the K. pneumoniae isolates tested. This fact, MIC profiles (penicillin rather than cephalosporin resistance), pIs, and sequence data showed that the chromosomal beta-lactamase of K. pneumoniae is a class A, group 2 enzyme distinct from the chromosomal AmpC enzymes found in several other gram-negative bacteria and from the chromosomal beta-lactamase K1 of K. oxytoca. We propose that the chromosomal beta-lactamase of K. pneumoniae be designated K2 and suggest that an allelic pI 7.6 variant of this enzyme is the ancestor of the SHV family of plasmid-mediated beta-lactamases.

Cloning and expression in Escherichia coli of genetic determinants for production of and immunity to microcin E492 from Klebsiella pneumoniae.

Abstract: Microcin E492 is a polypeptide antibiotic that is produced and excreted by Klebsiella pneumoniae RYC492. The genetic determinants for microcin synthesis and immunity were cloned in Escherichia coli VCS257 into the cosmid vector pHC79, starting from total DNA of K. pneumoniae RYC492. The microcin E492 expressed in E. coli had the same properties as that of K. pneumoniae, i.e., the same molecular weight, the ability to form ionic channels in planar phospholipid bilayers, and essentially identical biological properties. Microcin E492 expression in E. coli, like that in K. pneumoniae, was mainly in the exponential phase of growth, declining in the stationary phase. The immunity determinant was subcloned into the same vector, and its expression was found to disappear in the stationary phase. This phenomenon is not dependent on rpoS, the stationary-phase sigma factor.

Antimicrobial Susceptibility of Klebsiella pneumoniae Producing Extended-Spectrum beta-lactamase (ESBL) Isolated in Hospitals in Brazil.

Abstract: The prevalence of klebsiella pneumoniae producing extended-spectrum beta-lactamase (ESBL) has been increasing all over the world. Infections caused by ESBL producing isolates are difficult to detect with current susceptibility tests, and are difficult to treat. ESBLs confer resistance to all currently available beta-lactam, except carbapenems. In addition, ESBL production is usually associated with resistance to other classes of antimicrobial agents such as aminoglycosides and quinolones. The objective of this study was to evaluate the in vitro susceptibility patterns of ESBL producing K pneumoniae isolated in Brazil. Seventy-two strains were tested using E test against 30 antimicrobial agents, including carbapenems, second and third generation cephalosporins, aminoglycosides, quinolones, and some new compounds. The most active compounds (i.e. 100% susceptibility) were meropenem (MIC90, 0.125µg/mL), imipenem (MIC90, 0.25µg/mL), and cefotetan (MIC90, 2µg/mL). Ciprofloxacin (MIC90, 1µg/mL, 94% susceptibility) and cefepime (MIC90, 6µg/mL, 92% susceptibility), were also very active against our collection of ESBL producing K pneumoniae. None of the six aminoglycosides showed good activity against these strains (16% to 41% susceptibility) and only 39% of the isolates were susceptible to piperacillin/tazobactam. The results of our study indicated that the carbapenems are the most active compounds against ESBL producing L pneumoniae in Brazil, and ciprofloxacin remains very active against these strains. Cefotetan and cefepime were also very active against ESBL producing K.pneumoniaein Brazil; however, further studies are necessary to evaluate the role of these cephalosporins in the treatment of infections due to ESBL producing strains.

Identification of a Klebsiella pneumoniae strain associated with nosocomial urinary tract infection.

Abstract: To differentiate between relapse of infection and reinfection of the urinary tract due to Klebsiella pneumoniae, 33 K. pneumoniae isolates collected from 20 patients with spinal cord injury (SCI) over 2 years were typed by genomic fingerprinting by repetitive-element PCR. Clinical isolates obtained from the same patients with recurrent episodes of urinary tract infection (UTI) revealed identical genomic fingerprints indicating relapse of UTI due to K. pneumoniae, despite appropriate antibiotic therapy. Seventeen isolates obtained from 8 of the 20 SCI patients shared a common genotype, termed RD6. Among non-SCI patients residing in other nursing units, the RD6 genotype was found in 5 of 10 patients with K. pneumoniae UTI but in only 1 of 20 patients with K. pneumoniae infection that did not involve the urinary tract, suggesting a strong association of this genotype with UTI. All RD6 isolates exhibited strong adherence (> or =50 adherent bacteria per cell) to HEp-2 cells, whereas other K. pneumoniae isolates generally did not adhere to or adhered very weakly to HEp-2 cells (< or =5 adherent bacteria per cell). Adherence was inhibited either by 4% D-mannose or by anti-type 1 fimbrial rabbit serum. These results suggest that the capacity of K. pneumoniae RD6 isolates to cause UTI may be mediated by its striking adherence to mammalian cells.

Study of an outbreak of cefoxitin-resistant Klebsiella pneumoniae in a general hospital.

Abstract: During a 3-month period, six Klebsiella pneumoniae isolates resistant to cefoxitin and penicillin-inhibitor combinations were derived from patients in the intensive care unit of a hospital in Athens, Greece. Enterobacterial repetitive intergenic consensus PCR and pulsed-field gel electrophoresis provided evidence of the clonal origin of the isolates. Conventional techniques and ribotyping were inadequate in proving that the isolates were related. Resistance was due to a plasmidic class C beta-lactamase.

Reservoirs of nosocomial pathogens in neonatal intensive care unit.

Abstract: A total of 256 swabs taken from different areas of neonatal intensive care units (ICU) in KCG Hospital and AMC Hospital, Bangalore were bacteriologically investigated for prevalence, source and spread of nosocomial bacteria. Culture studies revealed growth in 217 (84.8%) swab samples indicating considerable contamination of different areas of the units and sources of infection. Klebsiella pneumoniae (27.3%) was the predominant organism followed by Esch coli (16.8%), Staph aureus (11.7%), Staph epidermidis and Pseudomonas aeruginosa (10.2%), enterococcus and proteus (4.7%), Citrobacter freundi (3.5%) and Clostridium tetani (2.4%) isolated from the equipment, cradles, other inanimate objects and environmental surfaces. Out of 312 isolates, monobacterial prevalence was 43.6% in contrast to polybacterial prevalence of 56.4%. Klebsiella pneumoniae (74.3%) was the predominant monobacterial isolate. The indoor air of the units was found to carry common nosocomial bacteria of 4 or more different bacterial species at dangerous levels as observed by colony counts of 15 to 30 on exposed blood agar plates. Almost all sources in ICU revealed the presence of Klebsiella Pneumoniae, Esch coli, pseudomonas and staphylococcus thus forming the potential reservoirs of nosocomial infections to babies and this could be attributed to overcrowding, poor ventilation system and failure to follow basic principles of strict protective barrier nursing.

Genes encoding s-triazine degradation are plasmid-borne in Klebsiella pneumoniae strain 99

Abstract: Klebsiella pneumoniae strain 99 degrades the s-triazine compound ammelide through cyanuric acid and biuret to yield urea, carbon dioxide, and ammonia. The urea and ammonia formed from the degradation of ammelide or cyanuric acid are utilized as sources of nitrogen for growth of the organism. When plasmids of the IncIα incompatibility group were transferred into K pneumoniae strain 99, the ability to degrade s-triazine compounds was lost at high frequency. Analysis of the plasmid profiles of s-triazine + and s-triazine - derivatives of strain 99 indicated that the largest of the at least five plasmids detected in this organism carries the genes encoding the s-triazine degradation pathway. Conjugal transfer of this plasmid from wild-type strain 99 into a type strain ofKlebsiella planticola (ATCC 33531) resulted in exconjugants able to utilize ammelide or cyanuric acid as nitrogen sources. Thus, the genes required for s-triazine degradation are present on a large IncIα plasmid in K. pneumoniae strain 99.