Optimal surveillance culture sites for detection of methicillin-resistant Staphylococcus aureus in newborns

Effectiveness of umbilical culture for surveillance of methicillin-resistant Staphylococcus aureus among neonates admitted to neonatal intensive care units

To compare the culture sensitivities of MRSA detection, we collected 988 paired umbilical and nasal cultures from screened neonates. MRSA positivity rates were 79.1% from umbilicus and 41.9% from nares (P = .01). The umbilicus was a more useful culture site than the nares for surveillance of MRSA among neonates upon admission.

The effect of routine surveillance and decolonization on the rate of Staphylococcus aureus infections in a level IV neonatal intensive care unit

OBJECTIVE

To evaluate the impact of active surveillance cultures (ASC) for Staphylococcus aureus (SA) and decolonization on the rate of infection in neonates in a neonatal intensive care unit (NICU).

STUDY DESIGN

Using a quasi-experimental design with control groups, rates of SA infections before and after implementing weekly ASC and topical mupirocin decolonization in a level IV NICU were compared. Comparators were the rates of gram negative bloodstream infections (BSI) and of SA BSI at an affiliated NICU where the intervention was not implemented.

RESULT

There was a 77% (p < 0.010) reduction in rate of NICU-wide methicillin-susceptible SA (MSSA) BSI, but no significant change in rate of methicillin-resistant SA BSI, likely due to a prevalent mupirocin-resistant clone. Rates of gram negative BSI and SA BSI at an affiliated NICU did not change significantly.

CONCLUSION

Weekly ASC and decolonization were associated with a unit-wide reduction in MSSA infections in a NICU.

Strategies to Prevent Methicillin-ResistantStaphylococcus aureusTransmission and Infection in Acute Care Hospitals: 2014 Update

Previously published guidelines are available that provide comprehensive recommendations for detecting and preventing healthcare-associated infections (HAIs). The intent of this document is to highlight practical recommendations in a concise format designed to assist acute care hospitals in implementing and prioritizing their methicillin-resistantStaphylococcus aureus(MRSA) prevention efforts. This document updates “Strategies to Prevent Transmission of Methicillin-ResistantStaphylococcus aureusin Acute Care Hospitals,” published in 2008. This expert guidance document is sponsored by the Society for Healthcare Epidemiology of America (SHEA) and is the product of a collaborative effort led by SHEA, the Infectious Diseases Society of America (IDSA), the American Hospital Association (AHA), the Association for Professionals in Infection Control and Epidemiology (APIC), and The Joint Commission, with major contributions from representatives of a number of organizations and societies with content expertise. The list of endorsing and supporting organizations is presented in the introduction to the 2014 updates.

Community-associated methicillin-resistant Staphylococcus aureus: prevalence in skin and soft tissue infections at emergency departments in the Greater Toronto Area and associated risk factors

Objective:

Community-associated methicillin-resistantStaphylococcus aureus(CA-MRSA), which is caused primarily by the Canadian methicillin-resistantStaphylococcus aureus-10 (CMRSA-10) strain (also known as the USA300 strain) has emerged rapidly in the United States and is now emerging in Canada. We assessed the prevalence, risk factors, microbiological characteristics and outcomes of CA-MRSA in patients with purulent skin and soft tissue infections (SSTIs) presenting to emergency departments (EDs) in the Greater Toronto Area.

Methods:

Patients withStaphylococcus aureusSSTIs who presented to 7 EDs between Mar. 1 and Jun. 30, 2007, were eligible for inclusion in this study. Antimicrobial susceptibilities and molecular characteristics of MRSA strains were identified. Demographic, risk factor and clinical data were collected through telephone interviews.

Results:

MRSA was isolated from 58 (19%) of 299 eligible patients. CMRSA-10 was identified at 6 of the 7 study sites and accounted for 29 (50%) of all cases of MRSA. Telephone interviews were completed for 161 of the eligible patients. Individuals with CMRSA-10 were younger (median 34 v. 63 yr,p= 0.002), less likely to report recent antibiotic use (22% v. 67%,p= 0.046) or health care–related risk factors (33% v. 72%,p= 0.097) and more likely to report community-related risk factors (56% v. 6%,p= 0.008) than patients with other MRSA strains. CMRSA-10 SSTIs were treated with incision and drainage (1 patient), antibiotic therapy (3 patients) or both (5 patients), and all resolved. CMRSA-10 isolates were susceptible to clindamycin, tetracycline and trimethoprimsulfamethoxazole.

Conclusion:

CA-MRSA is a significant cause of SSTIs in the Greater Toronto Area, and can affect patients without known community-related risk factors. The changing epidemiology of CA-MRSA necessitates further surveillance to inform prevention strategies and empiric treatment guidelines.

Capturing the cloud of diversity reveals complexity and heterogeneity of MRSA carriage, infection and transmission

Genome sequencing is revolutionizing clinical microbiology and our understanding of infectious diseases. Previous studies have largely relied on the sequencing of a single isolate from each individual. However, it is not clear what degree of bacterial diversity exists within, and is transmitted between individuals. Understanding this ‘cloud of diversity’ is key to accurate identification of transmission pathways. Here, we report the deep sequencing of methicillin-resistant Staphylococcus aureus among staff and animal patients involved in a transmission network at a veterinary hospital. We demonstrate considerable within-host diversity and that within-host diversity may rise and fall over time. Isolates from invasive disease contained multiple mutations in the same genes, including inactivation of a global regulator of virulence and changes in phage copy number. This study highlights the need for sequencing of multiple isolates from individuals to gain an accurate picture of transmission networks and to further understand the basis of pathogenesis.

Populations of bacterial pathogens can be diverse within colonized individuals. Here, the authors sequence the genomes of methicillin-resistant Staphylococcus aureus isolated from staff and animal patients at a veterinary hospital and show considerable within-host diversity that can rise and fall over time.

Prevalence of methicillin-resistant Staphylococcus aureus in skin and soft tissue infections in patients presenting to Canadian emergency departments

Background:

Community-associated methicillin-resistantStaphylococcus aureus(MRSA) is an increasingly common cause of skin and soft tissue infection (SSTI) worldwide. The prevalence of MRSA in SSTIs across Canada has not been well described. Studies in the United States have shown significant geographic variability in the prevalence of MRSA. This study characterizes the geographic prevalence and microbiology of MRSA in patients presenting to Canadian emergency departments with SSTIs.

Methods:

Using a prospective, observational design, we enrolled patients with acute purulent SSTIs presenting to 17 hospital emergency departments and 2 community health centres (spanning 6 Canadian provinces) between July 1, 2008, and April 30, 2009. Eligible patients were those whose wound cultures grewS. aureus. MRSA isolates were characterized by antimicrobial susceptibility testing and pulsed-field gel electrophoresis. All patients were subjected to a structured chart audit, and patients whose wound swabs grew MRSA were contacted by telephone to gather detailed information regarding risk factors for MRSA infection, history of illness, and outcomes.

Results:

Of the 1,353S. aureus–positive encounters recorded, 431 (32%) grew MRSA and 922 (68%) wounds grew methicillin-susceptibleS. aureus. We observed significant variation in both the prevalence of MRSA (11–100%) and the proportion of community-associated strains of MRSA (0– 100%) across our study sites, with a significantly higher prevalence of MRSA in western Canada.

Interpretation:

MRSA continues to emerge across Canada, and the prevalence of MRSA in SSTIs across Canada is variable and higher than previously expected.

[Update on outbreaks reported from neonatal intensive care units (2010-203): Staphylococcus aureus]

In terms of the unique risk profile of the patients and the morbidity associated with S. aureus infections in this vulnerable patient population, the literature on outbreaks of S. aureus (including MRSA) in neonatal intensive care units (NICUs) needs to be analyzed separately from reports derived from other intensive care units. With the objective of updating important information for those involved in outbreak management and fostering preventive efforts, this article summarizes the results of a systematic literature analysis, referring to an earlier publication by Gastmeier et al. It focuses on NICU outbreaks caused by S. aureus (including MRSA) and on controlling them.

Strategies to Prevent Transmission of Methicillin-ResistantStaphylococcus aureusin Acute Care Hospitals

Previously published guidelines are available that provide comprehensive recommendations for detecting and preventing healthcare-associated infections (HAIs). Our intent in this document is to highlight practical recommendations in a concise format to assist acute care hospitals in their efforts to prevent transmission of methicillin-resistantStaphylococcus aureus(MRSA). Refer to the Society for Healthcare Epidemiology of America/Infectious Diseases Society of America “Compendium of Strategies to Prevent Healthcare-Associated Infections” Executive Summary, Introduction, and accompanying editorial for additional discussion.

1. Burden of HAIs caused by MRSA in acute care facilities

a. In the United States, the proportion of hospital-associatedS. aureusinfections that are caused by strains resistant to methicillin has steadily increased. In 2004, MRSA accounted for 63% ofS. aureusinfections in hospitals.

b. Although the proportion ofS. aureus–associated HAIs among intensive care unit (ICU) patients that are due to methicillin-resistant strains has increased (a relative measure of the MRSA problem), recent data suggest that the incidence of central line–associated bloodstream infection caused by MRSA (an absolute measure of the problem) has decreased in several types of ICUs since 2001. Although these findings suggest that there has been some success in preventing nosocomial MRSA transmission and infection, many patient groups continue to be at risk for such transmission.

c. MRSA has also been documented in other areas of the hospital and in other types of healthcare facilities, including those that provide long-term care.

Decolonization to prevent Staphylococcus aureus transmission and infections in the neonatal intensive care unit

Staphylococcus aureus (S. aureus) continues to be a leading cause of outbreaks and health-care-associated infections in neonatal intensive care units. In the first few months of life, many neonates acquire S. aureus as part of their delicate and evolving microbiota. Neonates that asymptomatically acquire S. aureus colonization are at increased risk of developing a subsequent S. aureus infection. This review discusses the epidemiology and prevention of S. aureus disease in neonates and how decolonization to eradicate S. aureus may decrease S. aureus transmission and infections in the neonatal intensive care unit.

Multiple-strain colonization in nasal carriers of Staphylococcus aureus

Staphylococcus aureus is a commensal that can also cause invasive infection. Reports suggest that nasal cocolonization occurs rarely, but the resources required to sequence multiple colonies have precluded its large-scale investigation. A staged protocol was developed to maximize detection of mixed-spa-type colonization while minimizing laboratory resources using 3,197 S. aureus-positive samples from a longitudinal study of healthy individuals in Oxfordshire, United Kingdom. Initial typing of pooled material from each sample identified a single unambiguous strain in 89.6% of samples. Twelve single-colony isolates were typed from samples producing ambiguous initial results. All samples could be resolved into one or more spa types using the protocol. Cocolonization point prevalence was 3.4 to 5.8% over 24 months of follow-up in 360 recruitment-positives. However, 18% were cocolonized at least once, most only transiently. Cocolonizing spa types were completely unrelated in 56% of samples. Of 272 recruitment-positives returning ≥12 swabs, 166 (61%) carried S. aureus continuously but only 106 (39%) carried the same single spa type without any cocolonization; 31 (11%) switched spa type and 29 (11%) had transient cocarriage. S. aureus colonization is dynamic even in long-term carriers. New unrelated cocolonizing strains could increase invasive disease risk, and ongoing within-host evolution could increase invasive potential, possibilities that future studies should explore.

Major characteristics of Staphylococcus aureus colonizing Jordanian infants

BACKGROUND

Colonization of infants with methicillin-resistant Staphylococcus aureus (MRSA) carries specific toxin genes. In particular, Panton-Valentine leukocidin (PVL) are a risk factor for subsequent infection during hospitalization. This prospective study investigated important epidemiological characteristics of Staphylococcus aureus colonizing the nares and intestines of Jordanian infants.

METHODS

A total of 860 nasal and stool specimens were obtained from each of the 430 infants admitted to the neonatal intensive care unit or referred to outpatient clinics of Jordan University Hospital. All specimens were cultured to recover S. aureus, all isolates were tested for antimicrobial susceptibility and the MRSA strains for presence of specific toxin genes and SCCmec using polymerase chain reaction.

RESULTS

Eighty of the 430 (18.6%) infants were colonized with S. aureus, of these, 27 (6.3%) harbored the organism in both the nose and intestine. The frequency of S. aureus nasal and intestinal carriage in outpatient infants compared to inpatients admitted to the neonatal intensive care unit was significantly higher (27.3% vs 2.8%) and (17.1% vs 2.3%), respectively. MRSA accounted for 57/107 (53.3%) of all isolates, and of these 16/57 (28%) were PVL-positive and carried SCCmec type IV, except one, which was type III. All nasal and intestinal MRSA carried at least one toxin gene (tst, eta, seb), but few carried two toxin genes.

CONCLUSION

This study demonstrates that S. aureus strains are more frequently colonizing Jordanian outpatient infants than inpatients and all MRSA strains carried 1-3 clinically important staphylococcal toxin genes. Further studies are needed to investigate the role of these toxins in hospitalized infants.

Comprehensive strategy including prophylactic mupirocin to reduce Staphylococcus aureus colonization and infection in high-risk neonates

OBJECTIVE

To examine the use of long-term prophylactic mupirocin as part of a comprehensive strategy in reducing Staphylococcus aureus colonization and infection in a neonatal intensive care unit (NICU).

STUDY DESIGN

Twice daily mupirocin was applied to all infants admitted to the NICU throughout hospitalization starting in 2004. S. aureus surveillance was implemented in 2008. The efficacy of these practices was evaluated with a retrospective review of infants admitted from 2004 to 2010 found to be colonized or infected with S. aureus.

RESULT

During the study period, 66 of 6283 NICU infants had a S. aureus infection with 67% methicillin resistance. There were three distinctive S. aureus outbreaks, the first being a methicillin-resistant strain July 2004. After implementation of daily mupirocin, the outbreak was eradicated and the rate of S. aureus infection significantly decreased (1.82 to 0.40/1000 patient-days-at-risk, P=0.0049). Mupirocin was discontinued March 2005 followed by a methicillin-sensitive S. aureus outbreak November 2005. In December 2005, mupirocin was reinstituted and has continued to present day, again significantly reducing S. aureus infections (1.42 to 0.33/1000 patient-days-at-risk, P<0.0001) with zero isolates resistant to mupirocin. In the pre-mupirocin period, S. aureus colonization was upwards of 60% now with rates typically <5%. S. aureus colonization strongly predicted later invasive infection (P<0.0001).

CONCLUSION

Although controversial, prophylactic mupirocin in all NICU infants has acted as a barrier to colonization and markedly decreased S. aureus infection rates over a 5-year period.

Surveillance swabbing for MRSA on neonatal intensive care units – is weekly nasal swabbing the best option?

Most paediatric meticillin resistant Staphylococcus aureus (MRSA) infections occur in neonatal units, but evidence for ongoing MRSA surveillance is lacking and practice varies.

The aim of this study was to determine the optimal strategy for neonatal MRSA screening according to swab site, gestational age and birth weight. MRSA detection on simultaneous weekly nasal and groin surveillance swabs and suspected infected sites was determined for all admissions to a tertiary neonatal unit over eight years. Twenty one thousand, seven hundred and thirty six surveillance specimens were examined (3,784 admissions). Infants colonised with MRSA were smaller and of lower gestational age compared with uncolonised infants ( p<0.0001). Infants initially positive on groin swabs alone (13/68; 19%) were of significantly greater gestational age and weight at birth compared with infants initially positive on nose swabs/both nose and groin swabs (55/68; 80%). Infants initially identified on groin swabs were all subsequently detected on nasal swabs or discharged within two weeks of age. 18/86 (21%) of MRSA cases were initially detected on swabbing suspected infected sites. Surveillance swabbing identified 43% of infants before MRSA bacteraemia. Eighty five per cent of colonised infants would be detected by weekly nasal swabs and by swabbing suspected infected sites. Groin swabs detect a small number of bigger mature babies who are discharged before two weeks of age.

Methicillin-resistant Staphylococcus aureus colonization among women admitted for preterm delivery

OBJECTIVE

Methicillin-resistant Staphylococcus aureus infection is associated with morbidity in the neonatal intensive care unit. The purpose of this study was to determine the relationship between preterm maternal methicillin-resistant S aureus colonization and subsequent colonization and infection in premature neonates.

STUDY DESIGN

We conducted a prospective cohort study of 422 women admitted for preterm delivery. Methicillin-resistant S aureus cultures were collected from mothers and their neonates admitted to neonatal intensive care unit. We determined the proportion of women and neonates colonized with methicillin-resistant S aureus and examined possible factors associated with colonization and infection.

RESULTS

Fifteen of 422 (3.6%) women were found to be colonized with methicillin-resistant S aureus. Thirteen of 212 (6.1%) neonates admitted to neonatal intensive care unit were methicillin-resistant S aureus colonized and 3 of 13 (23.1%) developed a methicillin-resistant S aureus infection. We identified 1 methicillin-resistant S aureus colonized maternal-neonatal pair. The infant became methicillin-resistant S aureus positive 30 days after admission and did not develop a methicillin-resistant S aureus infection.

CONCLUSION

These findings suggest that maternal methicillin-resistant S aureus colonization is not a significant risk factor for vertical transmission of neonatal methicillin-resistant S aureus colonization.

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.

Importance of colonization site in the current epidemic of staphylococcal skin abscesses

OBJECTIVE

The goal was to compare rectal and nasal Staphylococcus aureus colonization rates and S aureus pulsed-field types (PFTs) for children with S aureus skin and soft-tissue abscesses and normal control subjects.

METHODS

Sixty consecutive children with S aureus skin and soft-tissue abscesses that required surgical drainage and 90 control subjects were enrolled. Cultures of the nares and rectum were taken in both groups. S aureus isolates from all sites were characterized through multiple-locus, variable-number, tandem-repeat analysis, pulsed-field gel electrophoresis, staphylococcal cassette chromosome mec typing for methicillin-resistant S aureus isolates, and determination of the presence of Panton-Valentine leukocidin genes.

RESULTS

S aureus was detected significantly more often in the rectum of children with abscesses (47%) compared with those in the control group (1%; P = .0001). Rates of nasal colonization with S aureus were equivalent for children with abscesses (27%) and control subjects (20%; P = .33). S aureus recovered from the rectum was identical to S aureus in the abscess in 88% of cases, compared with 75% of nasal isolates. PFT USA300, staphylococcal cassette chromosome mec type IV, and Panton-Valentine leukocidin genes were significantly increased in the S aureus isolates from children with abscesses compared with those from control subjects.

CONCLUSIONS

Skin and soft-tissue abscesses in the current epidemic of community-associated staphylococcal disease are strongly associated with rectal colonization by PFT USA300. Nasal colonization in children does not seem to be a risk factor.

Perioperative management of neurosurgical patients with methicillin-resistant Staphylococcus aureus

Object

The emergence of methicillin-resistant Staphylococcus aureus (MRSA) has posed a challenge in the treatment of neurosurgical patients. The authors investigated the impact of MRSA colonization and infection in the neurosurgical population at a community-based, tertiary care referral center.

Methods

Hospitalized patients under the care of the Kaiser Permanente inpatient neurosurgery service were prospectively entered into a database. In Phase I of the study, 492 consecutive patients were followed. Per hospital policy, the 260 patients from this group who were admitted to the intensive care unit (ICU) underwent screening for MRSA based on nasal swab cultures and a review of their medical history for prior MRSA infections. These patients were designated as either MRSA positive (17 patients, 6.5% of screened patients) or MRSA negative (243 patients). The 232 patients admitted to non-ICU nursing units did not undergo MRSA screening and were designated as unscreened. In Phase II of the study, the authors reviewed 1005 neurosurgical admissions and completed a detailed chart review in 62 MRSA-positive patients (6.2%). Eleven patients received nonoperative treatment. Five patients presented with community-acquired neurosurgical infections, and the causative organism was MRSA in 3 cases. Forty-six patients underwent 55 procedures, and the authors reviewed their perioperative management.

Results

In Phase I of the study, the authors found that for the MRSA-positive, MRSA-negative, and unscreened groups, the rates of postoperative neurosurgical wound infections caused by all pathogens were 23.5, 4.1, and 1.3%, respectively. For MRSA wound infections, the rates were 23.5, 0.8, and 0%, respectively. In Phase II, patients with MRSA were noted to have the following clinical features: male sex in 63%, a malignancy in 39.1%, diabetes in 34.8%, prior MRSA infection in 21.7%, immunosuppressed state in 17.4%, and a traumatic injury in 15.2%. The rate of postoperative neurosurgical wound infection in patients who received MRSA-specific prophylactic antibiotic therapy (usually vancomycin) was 7.4% (27 procedures) compared with 32.1% (28 procedures) in patients who received the standard treatment (usually cefazolin) (p = 0.04). Wound care for ICU patients was standardized for postoperative Days 0–7 with chlorhexidine cleaning at bandage changes at 3-day intervals. Wound cultures from neurosurgical site infections in patients with prior MRSA colonization or infection grew MRSA in 7 of 11 patients.

Conclusions

Neurosurgical patients identified with MRSA colonization or a prior history of MRSA infections benefit from specific perioperative care, including prophylactic antibiotics active against MRSA (such as vancomycin) and postoperative wound care with coverings and chlorhexidine antisepsis to reduce MRSA wound colonization.

Screening for Staphylococcus aureus carriage in pregnancy: usefulness of novel sampling and culture strategies

OBJECTIVE

The purpose of this study was to determine the most sensitive strategy for the detection of Staphylococcus aureus among pregnant women and newborn infants.

STUDY DESIGN

We obtained cultures for S aureus from 5 body sites of women at 35-37 weeks' gestation. We obtained cultures from their newborn infants before hospital discharge.

RESULTS

Of 209 women who were screened, 29% of the women had at least 1 culture that was positive for S aureus; 5% of infants were S aureus carriers. The sensitivities of each site for S aureus detection were 52% nares, 50% throat, 13% rectum, 8% vagina, and 10% skin. The most sensitive combination of 2 sites was nares and throat (88%). Perinatal transmission of S aureus occurred in 4 women. Maternal methicillin-resistant S aureus carriage rate was 1%. Two infants carried the USA300 methicillin-resistant S aureus.

CONCLUSION

Screening single body sites is insensitive for the detection of S aureus carriage in pregnancy. Sampling nares and throat is essential to the identification of S aureus carriers.

Body site colonization in patients with community-associated methicillin-resistant Staphylococcus aureus and other types of S. aureus skin infections

Efforts to control spread of community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) are often based on eradication of colonization. However, the role of nasal and non-nasal colonization in the pathogenesis of these infections remains poorly understood. Patients with acute S. aureus skin and soft tissue infection (SSTI) were prospectively enrolled. Each subject's nasal, axillary, inguinal and rectal areas were swabbed for S. aureus and epidemiological risk factors were surveyed. Among the 117 patients enrolled, there were 99 patients who had an SSTI and for whom data could be analysed. Sixty-five patients had a CA-MRSA SSTI. Among these patients, MRSA colonization in the nares, axilla, inguinal area and rectum was 25, 6, 11 and 13%, respectively, and 37% overall were MRSA colonized. Most (96%) MRSA colonization was detected using nose and inguinal screening alone. Non-nasal colonization was 25% among CA-MRSA patients, but only 6% among patients with CA-methicillin-susceptible S. aureus (MSSA) or healthcare-associated MRSA or MSSA. These findings suggest that colonization patterns in CA-MRSA infection are distinct from those in non-CA-MRSA S. aureus infections. The relatively high prevalence of non-nasal colonization may play a key role in CA-MRSA transmission and acquisition of infection.

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.

Intestinal carriage of Staphylococcus aureus: how does its frequency compare with that of nasal carriage and what is its clinical impact?

The bacterial species Staphylococcus aureus, including its methicillin-resistant variant (MRSA), finds its primary ecological niche in the human nose, but is also able to colonize the intestines and the perineal region. Intestinal carriage has not been widely investigated despite its potential clinical impact. This review summarizes literature on the topic and sketches the current state of affairs from a microbiological and infectious diseases' perspective. Major findings are that the average reported detection rate of intestinal carriage in healthy individuals and patients is 20% for S. aureus and 9% for MRSA, which is approximately half of that for nasal carriage. Nasal carriage seems to predispose to intestinal carriage, but sole intestinal carriage occurs relatively frequently and is observed in 1 out of 3 intestinal carriers, which provides a rationale to include intestinal screening for surveillance or in outbreak settings. Colonization of the intestinal tract with S. aureus at a young age occurs at a high frequency and may affect the host's immune system. The frequency of intestinal carriage is generally underestimated and may significantly contribute to bacterial dissemination and subsequent risk of infections. Whether intestinal rather than nasal S. aureus carriage is a primary predictor for infections is still ill-defined.