Methicillin-ResistantStaphylococcus aureusInfection and Colonization Among Hospitalized Prisoners

Prevention Strategies for Recurrent Community-Associated Staphylococcus aureus Skin and Soft Tissue Infections

PURPOSE OF REVIEW

Staphylococcus aureus skin and soft tissue infections (SSTI) are a major source of morbidity. More than half of patients experiencing SSTI will have at least one recurrent infection. These infections frequently cluster in households. Given the burden these infections pose to patients and healthcare, prevention strategies are of major clinical importance and represent an active area of research. Bacterial colonization is frequently an early and critical step in the pathogenesis of infection. As such, strategies to prevent reinfection have aimed to decrease staphylococcal colonization of the skin and mucus membranes, a process referred to as decolonization.

RECENT FINDINGS

Treatment of acute SSTI with incision and drainage and systemic antibiotics is the mainstay of therapy for healing of the acute infection. Systemic antibiotics also provide benefit through reduced incidence of recurrent SSTI. Education for patients and families regarding optimization of personal and household hygiene measures, and avoidance of sharing personal hygiene items, is an essential component in prevention efforts. For patients experiencing recurrent SSTI, or in households in which multiple members have experienced SSTI, decolonization should be recommended for all household members. A recommended decolonization regimen includes application of intranasal mupirocin and antiseptic body washes with chlorhexidine or dilute bleach water baths. For patients who continue to experience recurrent SSTI, periodic decolonization should be considered. Personal decolonization with topical antimicrobials and antiseptics reduces the incidence of recurrent S. aureus SSTI. Future avenues for investigation include strategies for household environmental decontamination as well as manipulation of the host microbiota.

Prevention of Recurrent Staphylococcal Skin Infections

Staphylococcus aureus infections pose a significant health burden. The emergence of community-associated methicillin-resistant S aureus has resulted in an epidemic of skin and soft tissue infections (SSTI), and many patients experience recurrent SSTI. As S aureus colonization is associated with subsequent infection, decolonization is recommended for patients with recurrent SSTI or in settings of ongoing transmission. S aureus infections often cluster within households, and asymptomatic carriers serve as reservoirs for transmission; therefore, a household approach to decolonization is more effective than measures performed by individuals alone. Novel strategies for the prevention of recurrent SSTI are needed.

Hand and nasal carriage of discordant Staphylococcus aureus isolates among urban jail detainees

In 928 Dallas County Jail detainees, nasal carriage of Staphylococcus aureus was found in 32.8% (26.5% methicillin-susceptible Staphylococcus aureus [MSSA] and 6.3% methicillin-resistant S. aureus [MRSA]), and hand carriage was found in 24.9% (20.7% MSSA and 4.1% MRSA). Among MRSA nasal carriers, 41% had hand MRSA carriage; 29% with hand MRSA carriage had no nasal S. aureus carriage. The prevalence of carriage was not associated with duration of the jail stay up to 180 days.

Community-associated methicillin-resistant Staphylococcus aureus: epidemiology and clinical consequences of an emerging epidemic

Staphylococcus aureus is an important cause of skin and soft-tissue infections (SSTIs), endovascular infections, pneumonia, septic arthritis, endocarditis, osteomyelitis, foreign-body infections, and sepsis. Methicillin-resistant S. aureus (MRSA) isolates were once confined largely to hospitals, other health care environments, and patients frequenting these facilities. Since the mid-1990s, however, there has been an explosion in the number of MRSA infections reported in populations lacking risk factors for exposure to the health care system. This increase in the incidence of MRSA infection has been associated with the recognition of new MRSA clones known as community-associated MRSA (CA-MRSA). CA-MRSA strains differ from the older, health care-associated MRSA strains; they infect a different group of patients, they cause different clinical syndromes, they differ in antimicrobial susceptibility patterns, they spread rapidly among healthy people in the community, and they frequently cause infections in health care environments as well. This review details what is known about the epidemiology of CA-MRSA strains and the clinical spectrum of infectious syndromes associated with them that ranges from a commensal state to severe, overwhelming infection. It also addresses the therapy of these infections and strategies for their prevention.

Prevalence, risk factors, and molecular epidemiology of methicillin-resistant Staphylococcus aureus among newly arrested men in Baltimore, Maryland

BACKGROUND

Outbreaks of methicillin-resistant Staphylococcus aureus (MRSA) within prison populations seemingly attest to its spread within the corrections industry; however, the extent of MRSA colonization on arrest is unknown.

METHODS

This study determined the prevalence and risk factors of S aureus on arrest. Nasal swabs from 602 newly arrested men were evaluated. Risk factors were assessed through self-report. Molecular characterization of each isolate was completed.

RESULTS

The prevalence of S aureus nasal colonization was 40.4% (243/602). MRSA colonization was found in 15.8% (95/602) of the total population and in 39.1% (95/243) of the total S aureus isolates. Twenty-three skin infections were identified; of these, 11 (47.8%) were S aureus infections, with methicillin-susceptible S aureus (MSSA) in accounting for 3 cases (13.1%) and MRSA accounting for 8 cases (34.8%). In 2 cases (25%) of MRSA wound infection, the nasal colonizing strain was MSSA. By pulsed-field gel electrophoresis, 76 of 95 (80%) nasal isolates were found to be USA300 or related subtypes, with the other 19 (20%) being non-USA300 strains. The Panton-Valentine leukocidin gene was identified in 38 (97.4%) USA300 isolates and in 6 (31.6%) non-USA 300 isolates.

CONCLUSION

MRSA colonization is far greater in this sample than in the general public. USA300 subtypes are highly prevalent. History of previous arrest was not associated with increased MRSA prevalence. MRSA risk factors differed significantly between those with and without a history of previous arrest.

Long-term follow-up of methicillin-resistant Staphylococcus aureus molecular epidemiology after emergence of clone USA300 in San Francisco jail populations

We performed a longitudinal analysis of 502 unique methicillin-resistant Staphylococcus aureus (MRSA) clinical isolates originating from San Francisco jail inmates between 2000 and 2007. Strain USA300, first encountered in 2001, accounted for 82.1% (412/502) of MRSA infections. Non-USA300 MRSA strains were rarely found after 2005 (one isolate in 2006, three in 2007).

Prevalence of methicillin-resistant Staphylococcus aureus and Acinetobacter baumannii in a long-term acute care facility

BACKGROUND

Patients in long-term acute care (LTAC) facilities often have many known risk factors for acquisition of antibiotic-resistant bacteria. However, the prevalence of resistance in these facilities has not been well described.

METHODS

We performed a single-day, point-prevalence study of a 180-bed, university-affiliated LTAC facility in Baltimore to assess the prevalence of methicillin-resistant Staphylococcus aureus (MRSA) and Acinetobacter baumannii in the anterior nares, perirectal area, sputum, and wounds.

RESULTS

Among the 147 patients evaluated, we found a high prevalence of colonization by both MRSA (28%) and A baumannii (30%). Of the A baumannii isolates, 90% were susceptible to imipenem and 92% were susceptible to ampicillin-sulbactam. No isolates were resistant to both imipenem and ampicillin-sulbactam.

CONCLUSION

The high prevalence of resistance found in this study supports the need for increased surveillance of patients in the LTAC environment. The fact that these patients are often frequently transferred to tertiary care facilities also supports the need for coordination and collaboration among facilities within the same health care system and the broader geographic area.

Predominance of methicillin-resistant Staphylococcus aureus among pathogens causing skin and soft tissue infections in a large urban jail: risk factors and recurrence rates

In the 1990s, community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) strains emerged as pathogens outside of the health care environment. Epidemic foci of CA-MRSA infections were reported in jails and prisons, but risk factors for MRSA infection there are not known. All skin and soft tissue infections (SSTIs) cultured in the Cook County Jail in March 2004 to August 2005 were reviewed. Demographic and clinical risk factors were compared among patients with methicillin-susceptible S. aureus (MSSA) SSTIs and those with MRSA SSTIs. Antibiotic susceptibilities were recorded, and we performed multilocus sequence typing on a sample of MRSA isolates. There were 378 SSTIs from different patients requiring culture, of which 240 (63.5%) were of MRSA and 43 (11.4%) were of MSSA; 84.8% of S. aureus isolates were MRSA. MRSA- and MSSA-infected patients were similar with regard to age, gender, ethnicity, previous exposure to the jail, and comorbidities. In the 12 months prior to the index culture, MRSA patients were more likely to have received a beta-lactam antibiotic (25% versus 9%; P = 0.02). Among 26 MRSA strains, 24 (92%) had the sequence type 8 (ST8) genotype. Within 6 months, 14% (95% confidence interval, 8.7% to 22.3%) of MRSA SSTI patients in the jail had a recurrent SSTI compared with 8.8% (95% confidence interval, 2.1% to 32.6%) of MSSA SSTI patients (P = 0.004). MRSA is the predominant cause of SSTIs requiring culture in the jail. Few risk factors differentiated MRSA from MSSA SSTIs, and detainee patients with MRSA SSTIs are at high risk for recurrent SSTIs.

Comparison of the BD GeneOhm methicillin-resistant Staphylococcus aureus (MRSA) PCR assay to culture by use of BBL CHROMagar MRSA for detection of MRSA in nasal surveillance cultures from an at-risk community population

We compared the BD GeneOhm methicillin-resistant Staphylococcus aureus (MRSA) PCR assay to culture with BBL CHROMagar MRSA for nasal surveillance among 602 arrestees from the Baltimore City Jail. The sensitivity and specificity were 88.5% and 91.0%, respectively, and after secondary analysis using enrichment broth, they were 89.0% and 91.7%, respectively. Twenty-three of 42 false-positive PCR lysates contained methicillin-susceptible S. aureus.

Prediction of methicillin-resistant Staphylococcus aureus involvement in disease sites by concomitant nasal sampling

Nasal colonization with methicillin-resistant Staphylococcus aureus (MRSA) is believed to precede disease. It is therefore reasonable to expect that testing for nasal MRSA colonization could provide guidance in the choice of empirical therapy for infections. We conducted a retrospective review of 5,779 nasal MRSA tests performed within a 24-h period before or after a clinical culture showed the growth of any organism. A positive nasal MRSA test strongly predicted MRSA involvement at a clinical site (relative risk, 12.9 times higher than in the remainder of the population; 95% confidence intervals [CI], 10.4, 16.1). Nasal MRSA colonization also strongly predicted antimicrobial resistance in other organisms. A negative nasal test was less useful; only 217 of 323 patients (67.2%; 95% CI, 61.8, 72.3) with clinical cultures involving MRSA had detectable, concomitant nasal MRSA colonization. Patients with clindamycin-susceptible MRSA infections were less likely (59%) to have nasal colonization than those with clindamycin-resistant MRSA infections (71%; P = 0.042). Patients nasally colonized with MRSA were substantially more likely to have antibiotic-resistant floras in clinical specimens, and this should be considered when initiating therapy. However, nearly a third of MRSA-infected patients were not nasally colonized, suggesting that nasal colonization need not precede disease and that a negative test for nasal colonization would not rule out MRSA disease in settings of moderate or high prevalence.