A meta-analysis was performed to summarize the impact of methicillin-resistance on mortality in Staphylococcus aureus bacteremia. A search of the MEDLINE database for studies published during the period of 1 January 1980 through 31 December 2000 and a bibliographic review identified English-language studies of S. aureus bacteremia. Studies were included if they contained the numbers of and mortality rates for patients with methicillin-resistant S. aureus (MRSA) and methicillin-susceptible S. aureus (MSSA) bacteremia. Data were extracted on demographic characteristics of the patients, adjustment for severity and comorbid illness, source of bacteremia, and crude and adjusted odds ratios (ORs) and 95% confidence intervals (CIs) for in-hospital mortality. When the results were pooled with a random-effects model, a significant increase in mortality associated with MRSA bacteremia was evident (OR, 1.93; 95% CI, 1.54-2.42; P<.001); significant heterogeneity was present. We explored the reasons for heterogeneity by means of subgroup analyses. MRSA bacteremia is associated with significantly higher mortality rate than is MSSA bacteremia.

/pdf/comparison-of-mortality-associated-with-methicillin-4yelhafml9.pdf

Comparison of mortality associated with methicillin-resistant and methicillin-susceptible staphylococcus aureus bacteremia: A meta-analysis

There is an association between the development of antimicrobial resistance in Staphylococcus aureus, enterococci, and gram-negative bacilli and increases in mortality, morbidity, length of hospitalization, and cost of health care. For many patients, inadequate or delayed therapy and severe underlying disease are primarily responsible for the adverse outcomes of infections caused by antimicrobial-resistant organisms. Patients with infections due to antimicrobial-resistant organisms have higher costs (approximately 6,000-30,000 dollars) than do patients with infections due to antimicrobial-susceptible organisms; the difference in cost is even greater when patients infected with antimicrobial-resistant organisms are compared with patients without infection. Strategies to prevent nosocomial emergence and spread of antimicrobial-resistant organisms are essential.

The Relationship between Antimicrobial Resistance and Patient Outcomes: Mortality, Length of Hospital Stay, and Health Care Costs

Data for 479 patients were analyzed to assess the impact of methicillin resistance on the outcomes of patients with Staphylococcus aureus surgical site infections (SSIs). Patients infected with methicillin-resistant S. aureus (MRSA) had a greater 90-day mortality rate than did patients infected with methicillin-susceptible S. aureus (MSSA; adjusted odds ratio, 3.4; 95% confidence interval, 1.5-7.2). Patients infected with MRSA had a greater duration of hospitalization after infection (median additional days, 5; P<.001), although this was not significant on multivariate analysis (P=.11). Median hospital charges were 29,455 dollars for control subjects, 52,791 dollars for patients with MSSA SSI, and 92,363 dollars for patients with MRSA SSI (P<.001 for all group comparisons). Patients with MRSA SSI had a 1.19-fold increase in hospital charges (P=.03) and had mean attributable excess charges of 13,901 dollars per SSI compared with patients who had MSSA SSIs. Methicillin resistance is independently associated with increased mortality and hospital charges among patients with S. aureus SSI.

/pdf/adverse-clinical-and-economic-outcomes-attributable-to-4ajiw8997b.pdf

Adverse clinical and economic outcomes attributable to methicillin resistance among patients with Staphylococcus aureus surgical site infection

Mechanisms of quinolone resistance in Escherichia coli and Salmonella: Recent developments

Background: Staphylococcus aureus bacteremia carries high mortality rates The clinical impact of methicillin resistance remains controversial: outcome comparisons between patients with bacteremia involving methicillin-susceptible (MSSA) and methicillinresistant (MRSA) S aureus are difficult to perform because of important differences in severity of illness Methods: A retrospective cohort analysis and 2 independent case-control analyses were performed to determine and compare outcomes and attributable mortality rates of MSSA (n=38) and MRSA bacteremia (n=47) in critically ill patients For the case-control studies, matching (1:2 ratio) was based on the APACHE (Acute Physiology and Chronic Health Evaluation) II classification: APACHE II score (±1 point) and diagnostic category Results: Patients with MRSA bacteremia had more acute renal failure and hemodynamic instability than patients with MSSA bacteremia They had a longer intensive care unit stay and ventilator dependency Patients with MRSA bacteremia had a higher 30-day mortality rate (532% vs 184%) and in-hospital mortality rate (638% vs 237%) (P05) Multivariate survival analysis demonstrated acute renal failure, length of mechanical ventilation, age, and methicillin resistance to be independently associated with mortality (P05) The attributable mortality rate for MSSA bacteremia was 13%: mortality rates for cases and controls were respectively 237% and 224% (P=94) The attributable mortality rate for MRSA bacteremia was 234%: mortality rates for cases and controls were respectively 638% and 404% (P = 02) The difference (221%) between both attributable mortality rates was significant (95% confidence interval, 88%-353%) Conclusion: In critically ill patients, after accurate adjustment for disease severity and acute illness, we found MRSA bacteremia to have a higher attributable mortality than MSSA bacteremia Arch Intern Med 2002;162:2229-2235

https://jamanetwork.com/journals/jamainternalmedicine/articlepdf/213720/ioi10766.pdf

Outcome and attributable mortality in critically ill patients with bacteremia involving methicillin-susceptible and methicillin-resistant Staphylococcus aureus.

A total of 88 salmonella isolates (72 clinical isolates for which the ciprofloxacin MIC was >0.06 μg/ml, 15 isolates for which the ciprofloxacin MIC was ≤0.06 μg/ml, and Salmonella enterica serotype Typhimurium ATCC 13311) were studied for the presence of genetic alterations in four quinolone resistance genes, gyrA, gyrB, parC, and parE, by multiplex PCR amplimer conformation analysis. The genetic alterations were confirmed by direct nucleotide sequencing. A considerable number of strains had a mutation in parC, the first to be reported in salmonellae. Seven of the isolates sensitive to 0.06 μg of ciprofloxacin per ml had a novel mutation at codon 57 of parC (Tyr57→Ser) which was also found in 29 isolates for which ciprofloxacin MICs were >0.06 μg/ml. Thirty-two isolates had a single gyrA mutation (Ser83→Phe, Ser83→Tyr, Asp87→Asn, Asp87→Tyr, or Asp87→Gly), 34 had both a gyrA mutation and a parC mutation (29 isolates with a parC mutation of Tyr57→Ser and 5 isolates with a parC mutation of Ser80→Arg). Six isolates which were isolated recently (from 1998 to 2001) were resistant to 4 μg of ciprofloxacin per ml. Two of these isolates had double gyrA mutations (Ser83→Phe and Asp87→Asn) and a parC mutation (Ser80→Arg) (MICs, 8 to 32 μg/ml), and four of these isolates had double gyrA mutations (Ser83→Phe and Asp87→Gly), one parC mutation (Ser80→Arg), and one parE mutation (Ser458→Pro) (MICs, 16 to 64 μg/ml). All six of these isolates and those with a Ser80→Arg parC mutation were S. enterica serotype Typhimurium. One S. enterica serotype Typhi isolate harbored a single gyrA mutation (Ser83→Phe), and an S. enterica serotype Paratyphi A isolate harbored a gyrA mutation (Ser83→Tyr) and a parC mutation (Tyr57→Ser); both of these isolates had decreased susceptibilities to the fluoroquinolones. The MICs of ciprofloxacin, levofloxacin, and sparfloxacin were in general the lowest of those of the six fluoroquinolones tested. Isolates with a single gyrA mutation were less resistant to fluoroquinolones than those with an additional parC mutation (Tyr57→Ser or Ser80→Arg), while those with double gyrA mutations were more resistant.

Mutations in Topoisomerase Genes of Fluoroquinolone-Resistant Salmonellae in Hong Kong

Hong Kong strains of methicillin-resistant and methicillin-sensitive Staphylococcus aureus have similar virulence.

A total of 217 and 73 strains of Salmonella enterica serotype Typhi isolated from 1985 to 1997 in Hong Kong and in 2 months of 1989 and 1990 in Vietnam, respectively, were studied. These isolates were typed by plasmid profile analysis, plasmid fingerprinting, ribotyping with PstI, and total DNA fingerprinting with NarI. There appeared to be no major outbreak of typhoid fever in Hong Kong during the study period since there was considerable heterogeneity among the isolates. Isolates from Hong Kong were different from those from Vietnam. Thirty-seven percent of Vietnamese isolates belonged to two predominant clones, with the rest being heterogeneous in nature. Total DNA fingerprinting supplemented with ribotyping could be a reliable and rapid method for epidemiological typing of S. enterica serotype Typhi.

Molecular Methods for the Epidemiological Typing of Salmonella enterica Serotype Typhi from Hong Kong and Vietnam

This study was initiated throughout Hong Kong, to reveal the characteristics of community-acquired infections. All specimens collected by general practitioners from infected patients were followed prospectively, and those that were culture-positive were analysed. Four thousand seven hundred and forty-one specimens were collected from 3977 patients by 89 doctors from July 2000 to October 2001. The most common specimens were throat swabs (33%), urine (26%) and sputa (16%). The average culture-positive rate was 28%. The most common organisms were Escherichia coli (18%), beta-haemolytic streptococci (15%) and Staphylococcus aureus (12%). Fluoroquinolone resistance was relatively high (up to 35%) in organisms commonly causing urinary tract infection (E. coli, Proteus and Morganella). Although none of the pneumococci was resistant to penicillin 1 mg/L, the proportion with intermediate resistance (0.1-1 mg/L) was alarming (81%). There were three strains of methicillin-resistant S. aureus. A decrease in ampicillin resistance but a high prevalence of macrolide resistance were noted in Haemophilus influenzae. All Neisseria gonorrhoeae isolates were resistant to penicillin, up to 79% to the fluoroquinolones, 15% to spectinomycin, but all were susceptible to ceftriaxone. Respiratory pathogens (Streptococcus pneumoniae, beta-haemolytic streptococci and H. influenzae) were relatively susceptible to the newer fluoroquinolones (0-2%, 0.5-6% and 2% resistant, respectively) or third-generation cephalosporins (0-2% resistant). The distribution of organisms and their antibiotic resistance varied over time. Thus frequent surveillance is needed to provide information on the drugs of choice for different infections.

/pdf/what-have-we-learnt-from-community-acquired-infections-in-20e5b8th5u.pdf

J. M. Ling

Papers

Mutations in Topoisomerase Genes of Fluoroquinolone-Resistant Salmonellae in Hong Kong

Hong Kong strains of methicillin-resistant and methicillin-sensitive Staphylococcus aureus have similar virulence.

Molecular Methods for the Epidemiological Typing of Salmonella enterica Serotype Typhi from Hong Kong and Vietnam

What have we learnt from community-acquired infections in Hong Kong?

Emerging resistance in Salmonella enterica serotype Typhi in Hong Kong