Previous antibiotic exposure and antimicrobial resistance in invasive pneumococcal disease: results from prospective surveillance.

BACKGROUND: Estimating the risk of antibiotic resistance is important in selecting empiric antibiotics. We asked how the timing, number of courses, and duration of antibiotic therapy in the previous 3 months affected antibiotic resistance in isolates causing invasive pneumococcal disease (IPD). METHODS: We conducted prospective surveillance for IPD in Toronto, Canada, from 2002 to 2011. Antimicrobial susceptibility was measured by broth microdilution. Clinical information, including prior antibiotic use, was collected by chart review and interview with patients and prescribers. RESULTS: Clinical information and antimicrobial susceptibility were available for 4062 (90%) episodes; 1193 (29%) of episodes were associated with receipt of 1782 antibiotic courses in the prior 3 months. Selection for antibiotic resistance was class specific. Time elapsed since most recent antibiotic was inversely associated with resistance (cephalosporins: adjusted odds ratio [OR] per day, 0.98; 95% confidence interval [CI], .96-1.00; P = .02; macrolides: OR, 0.98; 95% CI, .96-.99; P = .005; penicillins: OR [log(days)], 0.62; 95% CI, .44-.89; P = .009; fluoroquinolones: profile penalized-likelihood OR [log(days)], 0.62; 95% CI, .39-1.04; P = .07). Risk of resistance after exposure declined most rapidly for fluoroquinolones and penicillins and reached baseline in 2-3 months. The decline in resistance was slowest for macrolides, and in particular for azithromycin. There was no significant association between duration of therapy and resistance for any antibiotic class. Too few patients received multiple courses of the same antibiotic class to assess the significance of repeat courses. CONCLUSIONS: Time elapsed since last exposure to a class of antibiotics is the most important factor predicting antimicrobial resistance in pneumococci. The duration of effect is longer for macrolides than other classes.

Detection and characterization of heterogeneous vancomycin-intermediate Staphylococcus aureus isolates in Canada: results from the Canadian Nosocomial Infection Surveillance Program, 1995-2006.

We describe the epidemiology of heterogeneously resistant Staphylococcus aureus (hVISA) identified in Canadian hospitals between 1995 and 2006. hVISA isolates were confirmed by the population analysis profiling-area under the curve method. Only 25 hVISA isolates (1.3% of all isolates) were detected. hVISA isolates were more likely to have been health care associated (odds ratio [OR], 5.1; 95% confidence interval [CI], 1.9 to 14.2) and to have been recovered from patients hospitalized in central Canada (OR, 3.0; 95% CI, 1.2 to 7.4). There has been no evidence of vancomycin "MIC creep" in Canadian strains of methicillin (meticillin)-resistant S. aureus, and hVISA strains are currently uncommon.

Effect of multivitamin and mineral supplementation on episodes of infection in nursing home residents: a randomized, placebo-controlled study.

OBJECTIVES: To evaluate the effect of vitamin and mineral supplementation on infections in an elderly institutionalized population. DESIGN: Eighteen-month, randomized, placebo-controlled trial. SETTING: Twenty-one long-term care facilities. PARTICIPANTS: Seven hundred sixty-three subjects from 21 long-term care facilities. INTERVENTION: Participants were randomized to receive one multivitamin and mineral supplementation daily or placebo. MEASUREMENTS: The primary outcome was number of infections per subject. Secondary outcomes were antibiotic use and hospitalization rates. Infection control surveillance was conducted over 18 months using standardized criteria. RESULTS: Outcome data from 748 subjects, mean age 85, were included in the intention-to-treat analysis. Using univariate analyses, there was no difference in infectious episodes between the supplemented and placebo groups (3.5 infections per 1,000 resident-days vs 3.8 infections per 1,000 resident-days, odds ratio (OR)=0.92, 95% confidence interval (CI)=0.82-1.03, P=.12). There was a reduction in antibiotic usage in the supplementation group, but this was not significant in the multivariate model. There was no difference in the number of hospital visits. In the multivariate analysis, the effect of multivitamin use on total number of infections was not significant (OR=0.77, 95% CI=0.54-1.1). Subjects without dementia had a greater rate of infections than those with dementia (OR=1.44, 95% CI=1.19-1.76). In post hoc subgroup analysis, subjects without dementia who received supplementation had a significantly lower rate of infections than those who received placebo (relative risk=0.81, 95% CI=0.66-0.99). CONCLUSION: Overall, multivitamin and mineral supplementation does not have a significant effect on the incidence of infections in institutionalized seniors, although the subgroup of residents in long-term care without dementia may benefit from supplementation. Further research is needed to determine its effect in high-risk subgroups within the nursing home population.

An outbreak due to multiresistant Acinetobacter baumannii in a burn unit: risk factors for acquisition and management.

OBJECTIVES: To describe the investigation and management of an outbreak due to multiresistant Acinetobacter baumannii and to determine risk factors for acquisition of the organism. SETTING: A 14-bed regional burn unit in a Canadian tertiary-care teaching hospital. DESIGN: Case-control study with multivariate analysis of potential risk factors using logistic regression analysis. Surveillance cultures were obtained from the hospital environment, from noninfected patients, and from healthcare providers. RESULTS: A total of 31 (13%) of 247 patients with acute burn injuries acquired multiresistant A. baumannii between December 1998 and March 2000; 18 (58%) of the patients were infected. The organism was recovered from the hospital environment and the hands of healthcare providers. Significant risk factors for acquisition of multiresistant A. baumannii were receipt of blood products (odds ratio [OR], 10.8; 95% confidence interval [CI95], 3.4 to 34.4; P < .001); procedures performed in the hydrotherapy room (OR, 4.1; CI95, 1.3 to 13.1; P = .02); and increased duration of mechanical ventilation (OR, 1.1 per day; CI95, 1.0 to 1.1; P= .02). INTERVENTIONS: Improved compliance with hand hygiene, strict patient isolation, meticulous environmental cleaning, and temporary closure of the unit to new admissions. CONCLUSIONS: Acquisition of multiresistant A. baumannii was likely multifactorial, related to environmental contamination and contact with transiently colonized healthcare providers. Control measures addressing these potential sources of multiresistant A. baumannii were successful in terminating the outbreak. Ongoing surveillance and continued attention to hand hygiene and adequate environmental cleaning are essential to prevent recurrent outbreaks due to antibiotic-resistant bacteria in burn units.