Sasi Dharan

Risk Factors for Persistent Carriage of Methicillin-Resistant Staphylococcus aureus

We determined risk factors associated with persistent carriage of methicillin-resistant Staphylococcus aureus (MRSA) among 102 patients enrolled in a double-blind, placebo-controlled trial of nasally administered mupirocin ointment. MRSA decolonization was unsuccessful in 77 (79%) of 98 patients who met the criteria for evaluation. By univariate analysis, 4 variables were found to be associated with persistent MRSA colonization (P < .1 for all 4): absence of mupirocin treatment, previous fluoroquinolone therapy, > or = 2 MRSA-positive body sites, and low-level mupirocin resistance. After multivariable Cox proportional hazards modeling, the presence of > or = 2 positive body sites (adjusted hazard ratio [AHR], 1.7; 95% confidence interval [CI], 1.0-2.9) and previous receipt of a fluoroquinolone (AHR, 1.8; 95% CI, 1.0-3.3) were independently associated with MRSA persistence, whereas nasal mupirocin tended to confer protection (AHR, 0.6; 95% CI, 0.4-1.0). Low-level mupirocin resistance was observed in 9 genotypically different MRSA strains and was not independently associated with chronic MRSA carriage (AHR, 1.5; 95% CI, 0.9-2.5). Our findings suggest that multisite MRSA carriage and previous receipt of a fluoroquinolone are independent risk factors for persistent MRSA colonization.

Comparative efficacy of hand hygiene agents in the reduction of bacteria and viruses.

Background Health care-associated infections most commonly result from person-to-person transmission via the hands of health care workers. Methods We studied the efficacy of hand hygiene agents (n=14) following 10-second applications to reduce the level of challenge organisms (Serratia marcescens and MS2 bacteriophage) from the hands of healthy volunteers using the ASTM-E-1174-94 test method. Results The highest log10 reductions of S marcescens were achieved with agents containing chlorhexidine gluconate (CHG), triclosan, benzethonium chloride, and the controls, tap water alone and nonantimicrobial soap and water (episode 1 of hand hygiene, 1.60-2.01; episode 10, 1.60-3.63). Handwipes but not alcohol-based handrubs were significantly inferior from these agents after a single episode of hand hygiene, but both groups were significantly inferior after 10 episodes. After a single episode of hand hygiene, alcohol/silver iodide, CHG, triclosan, and benzethonium chloride were similar to the controls in reduction of MS2, but, in general, handwipes and alcohol-based handrubs showed significantly lower efficacy. After 10 episodes, only benzethonium chloride (1.33) performed as well as the controls (1.59-1.89) in the reduction of MS2. Conclusions Antimicrobial handwashing agents were the most efficacious in bacterial removal, whereas waterless agents showed variable efficacy. Alcohol-based handrubs compared with other products demonstrated better efficacy after a single episode of hand hygiene than after 10 episodes. Effective hand hygiene for high levels of viral contamination with a nonenveloped virus was best achieved by physical removal with a nonantimicrobial soap or tap water alone.

Use of Oligoarrays for Characterization of Community-Onset Methicillin-Resistant Staphylococcus aureus

ABSTRACT Until recently, methicillin-resistant Staphylococcus aureus (MRSA) was considered the prototype of a hospital-acquired bacterial pathogen. However, recent reports have shown that MRSA has now emerged in the community. Characterization of specific markers for distinguishing the origin of isolates could contribute to improved knowledge of MRSA epidemiology. The release of whole-genome sequences of hospital- and community-acquired S. aureus strains allowed the development of whole-genome content analysis techniques, including microarrays. We developed a microarray composed of 8,191 open reading frame-specific oligonucleotides covering >99% of the four sequenced S. aureus genomes (N315, Mu50, MW2, and COL) to evaluate gene contents of hospital- and community-onset S. aureus strains. In parallel, pulsed-field gel electrophoresis, variable number of tandem repeats, antibiogram, staphylococcal cassette chromosome-mec element typing, and presence of the Panton-Valentine leukocidin gene were evaluated in a collection of 15 clinical isolates. Clusters obtained with microarrays showed a high degree of similarity with those obtained by pulsed-field gel electrophoresis or variable number of tandem repeats. Clusters clearly segregated hospital-onset strains from community-onset strains. Moreover, the microarray approach allowed definition of novel marker genes and chromosomal regions specific for given groups of isolates, thus providing better discrimination and additional information compared to pulsed-field gel electrophoresis and variable number of tandem repeats. Finally, the comparative genome hybridization approach unraveled the occurrence of multiple horizontal transfer events leading to community-onset MRSA as well as the need for a specific genetic background in recipient strains for both the acquisition and the stability of the mec element.

Comparison of waterless hand antisepsis agents at short application times: raising the flag of concern

OBJECTIVE Although alcohol-based hand rinses and gels have recommended application times of 30 to 60 seconds, healthcare workers usually take much less time for hand hygiene. We compared the efficacies of four alcohol-based hand rubs produced in Europe (hand rinses A, B, and C and one gel formulation) with the efficacy of the European Norm 1500 (EN 1500) reference waterless hand antisepsis agent (60% 2-propanol) at short application times. DESIGN Comparative crossover study. SETTING Infection Control Program laboratory of a large tertiary-care teaching hospital. PARTICIPANTS Twelve healthy volunteers. INTERVENTION Measurement of residual bacterial counts and log reduction factors following inoculation of fingertips with Staphylococcus aurens American Type Culture Collection (ATCC) 6538, Pseudomonas aeruginosa ATCC 15442, and a clinical isolate of Enterococcus faecalis. RESULTS All hand rinses satisfied EN 1500 standards following a single application for 15 and 30 seconds, but reduction factors for the gel formulation were significantly lower for all tested organisms (all P < .025). CONCLUSIONS Under stringent conditions similar to clinical practice, all three hand rinses proved to be more efficacious than the marketed alcohol-based gel in reducing bacterial counts on hands. Further studies are necessary to determine the in vivo efficacy of alcohol-based gels and whether they are as efficacious as alcohol-based rinses in reducing the transmission of nosocomial infections.

Pseudomonas aeruginosa outbreak in a pediatric intensive care unit linked to a humanitarian organization residential center

Background: Pseudomonas aeruginosa commonly colonizes the hospital environment. Between April 2006 and September 2008, we investigated an outbreak of P. aeruginosa infection occurring in a pediatric intensive care unit. We conducted epidemiologic and molecular investigations to identify the source of the outbreak. Methods: Retrospective case finding; surveillance cultures of patients and environmental sites; admission screening; case-control study; and molecular typing. Patient and Setting: Infants and children in a pediatric intensive care unit of a tertiary-care institution. Results: Thirty-seven cases of P. aeruginosa infection or colonization were detected between April 2006 and September 2008, including 3 fatal bloodstream infections. A closely-related strain was detected in 4 residents of a humanitarian nongovernmental organization (NGO) center who developed an infection, from 4 additional residents upon their hospital admission, and from a sink drain at the NGO residential center. NGO recipients represented 65% (24/37) of the total number of cases of P. aeruginosa colonization or infection during the outbreak period. Investigation at the residential center showed widespread contamination of the sewage system (10/14 sinks and shower drains, 70%) and a high prevalence (38%) of P. aeruginosa carriage among children. Conclusions: These findings suggest that the probable cause of the outbreak was the contamination of the NGO residential center with further nosocomial transmission after admission, and highlight the importance of considering external sources when investigating hospital outbreaks.

Outbreak of Endophthalmitis After Cataract Surgery: The Importance of the Quality of the Surgical Wound

Postoperative endophthalmitis is a rare but potentially devastating condition. We investigated an outbreak of 8 cases of endophthalmitis in patients who underwent phakectomy performed by a single surgeon from January through September 2004. The outbreak was traced to damaged surgical blades, and it highlights the importance of the quality of the surgical wound.