Familial carriage of methicillin-resistant Staphylococcus aureus and subsequent infection in a premature neonate

Prolonged silent carriage, genomic virulence potential and transmission between staff and patients characterize a neonatal intensive care unit (NICU) outbreak of methicillin-resistant Staphylococcus aureus (MRSA)

BACKGROUND

Methicillin-resistant Staphylococcus aureus (MRSA) is an important pathogen in neonatal intensive care units (NICU) that confers significant morbidity and mortality.

OBJECTIVE

Improving our understanding of MRSA transmission dynamics, especially among high-risk patients, is an infection prevention priority.

METHODS

We investigated a cluster of clinical MRSA cases in the NICU using a combination of epidemiologic review and whole-genome sequencing (WGS) of isolates from clinical and surveillance cultures obtained from patients and healthcare personnel (HCP).

RESULTS

Phylogenetic analysis identified 2 genetically distinct phylogenetic clades and revealed multiple silent-transmission events between HCP and infants. The predominant outbreak strain harbored multiple virulence factors. Epidemiologic investigation and genomic analysis identified a HCP colonized with the dominant MRSA outbreak strain who cared for most NICU patients who were infected or colonized with the same strain, including 1 NICU patient with severe infection 7 months before the described outbreak. These results guided implementation of infection prevention interventions that prevented further transmission events.

CONCLUSIONS

Silent transmission of MRSA between HCP and NICU patients likely contributed to a NICU outbreak involving a virulent MRSA strain. WGS enabled data-driven decision making to inform implementation of infection control policies that mitigated the outbreak. Prospective WGS coupled with epidemiologic analysis can be used to detect transmission events and prompt early implementation of control strategies.

The Correlation Between Biofilm-Forming Ability of Community-Acquired Methicillin-Resistant Staphylococcus aureus Isolated from the Respiratory Tract and Clinical Characteristics in Children

Objective

This study aimed to investigate the biofilm-forming ability, molecular typing, and antimicrobial resistance of community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) strains isolated from the respiratory tract of children and their correlation with clinical characteristics.

Methods

All CA-MRSA strains were isolated from hospitalized children, and their presentation, molecular typing, antimicrobial susceptibility, and biofilm formation were investigated. The clinical characteristics were compared between the strong and weak biofilm producer groups.

Results

Fifty-three CA-MRSA strains were isolated from the respiratory samples of 53 children, with nearly half of them being young infants (0-12 months). Approximately, 88.7% (47/53) of the isolates were resistant to four or more antibiotics, mainly β-lactam antibiotics, lincosamides, and macrolides. Twelve sequence types (STs) and 20 subtypes of staphylococcal protein A (spa) typing were identified, with ST59-t437 (39.6%, 21/53) as the predominant subtype. All strains showed the ability to form biofilms. When compared to children with weak biofilm-forming CA-MRSA strains, those with strong biofilm-forming strains had higher proportions of lower respiratory tract infections (LRTI) (88.5% vs 59.3%), obvious cough symptoms (84.6% vs 51.9%), and severe chest imaging manifestations (76.9% vs 37.0%). Furthermore, a strong biofilm-forming ability significantly increased the risk of prolonged cough in children with LRTI (44.4% vs 14.3%), and a positive correlation between the duration of cough and the extent of biofilm formation was observed. Medical history investigation revealed that the strong biofilm-forming group had a much higher percentage of macrolides intake than the weak biofilm-forming group in the last month before admission (61.5% vs 14.8%).

Conclusion

ST59-t437 was the most prevalent clone in CA-MRSA respiratory isolates among the hospitalized children. All CA-MRSA strains formed biofilms. The stronger the biofilm-forming ability, the more serious and prolonged were the respiratory symptoms.

Reducing antibiotic prescribing and addressing the global problem of antibiotic resistance by targeted hygiene in the home and everyday life settings: A position paper

Antimicrobial resistance (AMR) continues to threaten global health. Although global and national AMR action plans are in place, infection prevention and control is primarily discussed in the context of health care facilities with home and everyday life settings barely addressed. As seen with the recent global SARS-CoV-2 pandemic, everyday hygiene measures can play an important role in containing the threat from infectious microorganisms. This position paper has been developed following a meeting of global experts in London, 2019. It presents evidence that home and community settings are important for infection transmission and also the acquisition and spread of AMR. It also demonstrates that the targeted hygiene approach offers a framework for maximizing protection against colonization and infections, thereby reducing antibiotic prescribing and minimizing selection pressure for the development of antibiotic resistance. If combined with the provision of clean water and sanitation, targeted hygiene can reduce the circulation of resistant bacteria in homes and communities, regardless of a country's Human Development Index (overall social and economic development). Achieving a reduction of AMR strains in health care settings requires a mirrored reduction in the community. The authors call upon national and international policy makers, health agencies, and health care professionals to further recognize the importance of targeted hygiene in the home and everyday life settings for preventing and controlling infection, in a unified quest to tackle AMR.

Acinetobacter baumannii and methicillin-resistant Staphylococcus aureus in long-term care facilities in eastern Taiwan

Objective:

The prevention of infections is crucial in long-term care programs. Investigations of the occurrence and sources of pathogens in long-term care facilities (LTCFs) are still lacking, especially in eastern Taiwan. In this study, we conducted a surveillance of two common pathogens, Acinetobacter baumannii (AB) and methicillin-resistant Staphylococcus aureus (MRSA), in LTCFs in Hualien.

Materials and Methods:

Pathogenic assays including isolation, identification, and antimicrobial susceptibility tests were conducted for AB and MRSA at LTCFs in Eastern Taiwan. Staphylococcal cassette chromosome mec typing assays were done to understand the relatedness of clonal strains of MRSA.

Results:

All AB-positive samples in the LTCFs were mainly from water-rich samples and were drug susceptible. Our data indicated that the AB strains from LTCFs were similar to those from Puzi River watersheds in Taiwan, which were not drug resistant to commonly used antibiotics. On the other hand, the drug resistance analysis of MRSA indicated that the genotypes from the LTCFs were similar to those from nearby hospitals. Eight strains of MRSA were isolated from four LTCFs, of which five were identified as hospital-acquired strains according to SSCmed typing assays.

Conclusion:

These findings suggest that MRSA in LTCFs might propagate from hospitals and could be transmitted between hospitals and LTCFs. Health authorities should be aware of this risk. The long-term follow-up of MRSA is recommended in local medical institutions as well as in LTCFs for correlative analysis.

Prevalence and risk factors of community-associated methicillin-resistant Staphylococcus aureus carriage in Asia-Pacific region from 2000 to 2016: a systematic review and meta-analysis

OBJECTIVE

Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) is an emerging global public health threat. In response to a highlighted strategic priority of the World Health Organization Global Action Plan on Antimicrobial Resistance, to "strengthen the knowledge and evidence base through surveillance and research", we synthesized published articles to estimate CA-MRSA carriage prevalence in the Asia-Pacific region.

METHODS

A systematic review was conducted following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines (PROSPERO CRD:42017067399). We searched MEDLINE, EMBASE, and PubMed for articles published from 1 January 2000 to 19 May 2017, which reported CA-MRSA carriage (defined as either colonization or infection) in Asia-Pacific region from 2000 to 2016. Studies were stratified according to settings (community or hospital where CA-MRSA was isolated) and study populations (general public or subpopulations with specified characteristics). Ranges of CA-MRSA carriage prevalence were reported for study groups.

RESULTS

In total, 152 studies were identified. Large diversity was observed among studies in most study groups. In community-level studies, the CA-MRSA carriage prevalence among the general public ranged from 0% to 23.5%, whereas that ranged from 0.7% to 10.4% in hospital settings. From community-level studies, countries with the highest prevalence were India (16.5%-23.5%), followed by Vietnam (7.9%) and Taiwan (3.5%-3.8%). Children aged ≤6 (range: 0.5%-40.3%) and household members of CA-MRSA carriers (range: 13.0%-26.4%) are subgroups without specific health conditions but with much higher CA-MRSA carriage when compared to the general population.

CONCLUSION

Our CA-MRSA prevalence estimates serve as the baseline for future national and international surveillance. The ranges of prevalence and characteristics associated with CA-MRSA carriage can inform health authorities to formulate infection control policies for high-risk subgroups. Future studies should explore the heterogeneities in CA-MRSA carriage prevalence among subgroups and countries to clarify the predominant transmission mechanisms in Asia-Pacific and other regions.

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.

Transmission of Methicillin-ResistantStaphylococcus aureusto Preterm Infants Through Breast Milk

Objective:

To determine a potential source of MRSA colonization and infection among preterm infants in a neonatal intensive care unit (NICU) using molecular analysis of breast milk samples.

Design:

Case report, outbreak investigation.

Results:

Preterm triplets were delivered at 26 weeks' gestation via cesarean section when routine active surveillance for MRSA was performed for all infants in a NICU. Surveillance consisted of swabbing the throat, nose, and umbilicus (TNU) weekly. Although infants A and B initially had negative TNU swabs, repeat cultures were positive for MRSA on day of life (DOL) 10 and DOL 18, respectively. Surveillance and clinical cultures for infant C were negative. Infant A developed sepsis, and multiple blood cultures were positive for MRSA beginning on DOL 14. Infant B developed conjunctivitis and a conjunctival exudate culture was positive for MRSA on DOL 70. Both infants were fed breast milk via nasogastric tube. Cultures of breast milk samples for infants A and B dated prior to either infant's first positive surveillance culture were positive for MRSA. All MRSA isolates had identical results on antibiotic susceptibility testing. PFGE demonstrated identical banding patterns for the MRSA isolates from the blood culture of infant A, breast milk for infants A and B, and a surveillance swab from infant B. At no time did the mother develop evidence of mastitis or other local breast infection.

Conclusions:

MRSA can be passed from mother to preterm infant through contaminated breast milk, even in the absence of maternal infection. Colonization and clinical disease can result.

Prevalence of and risk factors for MRSA colonization in HIV-positive outpatients in Singapore

BACKGROUND

Whilst there have been studies on the risks and outcomes of MRSA colonization and infections in HIV-positive patients, local data is limited on the risk factors for MRSA colonization among these patients. We undertook this study in a tertiary HIV care centre to document the risk factors for colonization and to determine the prevalence of MRSA colonization among HIV-positive outpatients in Singapore.

METHODS

This was a cross-sectional study in which factors associated with MRSA positivity among patients with HIV infection were evaluated. A set of standardized questionnaire and data collection forms were available to interview all recruited patients. Following the interview, trained nurses collected swabs from the anterior nares/axilla/groin (NAG), throat and peri-anal regions. Information on demographics, clinical history, laboratory results and hospitalization history were retrieved from medical records.

RESULTS

MRSA was detected in swab cultures from at least 1 site in 15 patients (5.1%). Inclusion of throat and/or peri-anal swabs increased the sensitivity of NAG screening by 20%. Predictors for MRSA colonization among HIV-positive patients were age, history of pneumonia, lymphoma, presence of a percutaneous device within the past 12 months, history of household members hospitalized more than two times within the past 12 months, and a most recent CD4 count less than 200.

CONCLUSIONS

This study highlights that a proportion of MRSA carriers would have been undetected without multiple-site screening cultures. This study could shed insight into identifying patients at risk of MRSA colonization upon hospital visit and this may suggest that a risk factor-based approach for MRSA surveillance focusing on high risk populations could be considered.

Staphylococcus aureus- the predominant pathogen in the neonatal ICU of a tertiary care hospital in amritsar, India

BACKGROUND

An early treatment and the appropriate and the rational use of antibiotics would minimize the risk of severe morbidity and mortality in neonatal sepsis, and reduce the emergence of multi-drug resistant organisms in intensive care units. For the success of an early empiric treatment, a periodic review of the cases to assess any changing trends in the infecting organisms and their antimicrobial susceptibility is important.

AIM

To study the most commonly encountered bacterial pathogens which caused neonatal sepsis and their sensitivity patterns, so that guidelines could be prepared for a rational antibiotic therapy.

SETTING AND DESIGN

This was a retrospective study which was conducted in the Department of Microbiology and the Neonatal Intensive Care Unit (NICU) at SGRDIMSAR, Amritsar, during June 2011 to June 2012.

METHODS AND MATERIALS

Blood specimens for culture were drawn from 311 newborns who were admitted in an NICU with sepsis. The specimens were inoculated into brain heart infusion broth. Subcultures were performed on days 1, 2, 3, 5, 7 and 10. The isolates were identified by doing standard biochemical tests. The antibiotic resistance patterns of the isolates were studied by the Kirby Bauer disc diffusion technique.

RESULTS

A total of 131 organisms were isolated from the 311 blood cultures. These included Staphylococcus aureus (n=68), Coagulase Negative Staphylococcus (CoNS) (n=30), Klebsiella pneumoniae (n=10), Acinetobacter baumannii (n=9), Escherichia coli (n=05), Enterobacter cloacae (n=04), Citrobacter diversus (n=02), Pseudomonas aeruginosa (n=02) and Candida (n=01). Staphylococcus aureus was the main pathogen in both early and late-onset sepsis. On antibiotic sensitivity testing, 57.35% of the Staphylococcus aureus isolates were found to be methicillin resistant. More than 90% gram negative rods were resistant to amikacin. The resistance to the third generation cephalosporins varied between 50-55%. The resistance to ciprofloxacin was quite high; however, most of the isolates were susceptible to levofloxacin. A majority of the isolates were susceptible to piperacillin- tazobactum and imipenem.

CONCLUSION

The present study emphasized the importance of periodic surveys on the microbial flora which was encountered in particular neonatal settings to recognize the trend.

Epidemiology and clinical features of methicillin-resistant Staphylococcus aureus in the University Hospital, Jeddah, Saudi Arabia

OBJECTIVE

To describe the prevalence, demography and clinical characteristics of patients who were colonized or infected with methicillin-resistant Staphylococcus aureus (MRSA) in 1998 at King Abdulaziz University Hospital, Jeddah, Saudi Arabia.

PATIENTS AND METHODS

Results of MRSA-positive cultures of clinical specimens obtained as part of investigations for suspected infections were retrieved from the King Abdulaziz University Hospital Infection Control Department's records. Charts of patients were reviewed.

RESULTS

Of 292 S aureus isolates identified, 111 (38%) were MRSA, or 6.0 MRSA isolates/1000 admissions, which represented a marked increase over MRSA prevalence in 1988 (less than 2%). Nosocomial acquisition occurred in 74.8% of isolates. All age groups were affected, but 45.9% of patients were in the 'extremes of age' group (younger than one or older than 60 years of age). The prevalence was highest in the medical ward (27%), followed by the paediatrics combined medical and surgical ward (20.7%), the outpatient department (18%), the adult surgical ward (17.1%) and the intensive care units (17.1%). Two-thirds (66.7%) of cases represented infection and the remainder represented colonization. Surgical wounds (31.1%), the chest (27%) and endovascular catheters (20.3%) were the most common sites of infection. Bacteremia occurred in 27% of patients. Local signs (68.9%) and fever (60.8%) were the most common clinical manifestations. Respiratory distress and septic shock occurred in 28.4% and 6.8% of cases, respectively. Of 74 patients with MRSA infection and 37 patients with MRSA colonization, 91.9% and 56.8% received antibiotics in the preceding six weeks, respectively (P<0.0001). The total mortality of patients with MRSA infection was 60.8%; 37.8% of deaths were the result of MRSA infection and 23% were the result of other diseases.

CONCLUSIONS

The prevalence of MRSA is high and rapidly increasing at King Abdulaziz University Hospital, as it is worldwide. Control measures to prevent the spread of MRSA in hospitals should continue with reinforcement of hygienic precautions and development of policies to restrict the use of antibiotics.

Spread of methicillin-resistant Staphylococcus aureus in a large tertiary NICU: network analysis

OBJECTIVE

Methicillin-resistant Staphylococcus aureus (MRSA) colonization in NICUs increases the risk of nosocomial infection. Network analysis provides tools to examine the interactions among patients and staff members that put patients at risk of colonization.

METHODS

Data from MRSA surveillance cultures were combined with patient room locations, nursing assignments, and sibship information to create patient- and unit-based networks. Multivariate models were constructed to quantify the risk of incident MRSA colonization as a function of exposure to MRSA-colonized infants in these networks.

RESULTS

A MRSA-negative infant in the NICU simultaneously with a MRSA-positive infant had higher odds of becoming colonized when the colonized infant was a sibling, compared with an unrelated patient (odds ratio: 8.8 [95% confidence interval [CI]: 5.3-14.8]). Although knowing that a patient was MRSA-positive and was placed on contact precautions reduced the overall odds of another patient becoming colonized by 35% (95% CI: 20%-47%), having a nurse in common with that patient still increased the odds of colonization by 43% (95% CI: 14%-80%). Normalized group degree centrality, a unitwide network measure of connectedness between colonized and uncolonized patients, was a significant predictor of incident MRSA cases (odds ratio: 18.1 [95% CI: 3.6-90.0]).

CONCLUSIONS

Despite current infection-control strategies, patients remain at significant risk of MRSA colonization from MRSA-positive siblings and from other patients with whom they share nursing care. Strategies that minimize the frequency of staff members caring for both colonized and uncolonized infants may be beneficial in reducing the spread of MRSA colonization.

Potential role of pet animals in household transmission of methicillin-resistant Staphylococcus aureus: a narrative review

In this narrative review, we found numerous reports suggesting that dogs and cats may play a role in household methicillin-resistant Staphylococcus aureus (MRSA) transmission and recurrent MRSA infection in human contacts. Future work should emphasize elucidating more clearly the prevalence of MRSA in household pets and characterize transmission dynamics of MRSA humans and pet animals.

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.

High prevalence of MRSA in household contacts

In a 6-y period, 114 household contacts connected to newly diagnosed MRSA patients screened for MRSA in the southern part of Sweden. In 22 of 51 (43%) families, 1 to 4 household contact(s) connected to a MRSA patient were positive for MRSA. In the 22 families, 42 of 60 (70%) household contacts were positive for MRSA and transmission of MRSA occurred between adult couples, parents and children, grandparent and children and between siblings. Within a family, MRSA-positive family members had in all but 1 instance identical MRSA strain genotypes (spa types) making intrafamilial spread of MRSA highly probable. MRSA transmission among household contacts may contribute to the prevalence of MRSA in the community and failure to identify MRSA in household contacts may maintain MRSA colonization in an already known MRSA patient. MRSA screening of family members living in the same household as a known MRSA patient should therefore be considered.

[Hand hygiene: scientific evidence and common sense]

Hand washing was rightly considered a measure of personal hygiene for centuries. Today there is enough scientific evidence showing that a simple and inexpensive measure can help significantly reduce clinical infections. In spite of this, published studies show that hand hygiene only takes place between 15% and 50% of the instances in which it should be done. In order to support countries in setting priorities to deal with infections related to health care, the World Health Organization has developed a campaign to improve compliance with hand hygiene. Fundamental elements of the campaign include staff training, change of habits, motivating health professionals, and enabling access to effective products at the point of patient care. At institutional level, healthcare managers need to make a firm commitment, and make hand hygiene one of the quality assurance objectives of their organisations.

Seven-year experience with a surveillance program to reduce methicillin-resistant Staphylococcus aureus colonization in a neonatal intensive care unit

OBJECTIVES

The objectives of this study were to determine the incidence rates of neonatal methicillin-resistant Staphylococcus aureus colonization and infection after the implementation of a NICU methicillin-resistant S aureus surveillance and isolation program and to describe the characteristics of infants with methicillin-resistant S aureus colonization and invasive disease.

METHODS

From August 2000 through August 2007, all infants admitted to the study NICU were screened for methicillin-resistant S aureus colonization with weekly nasal/rectal swabs; colonized or infected infants were isolated and cared for as a cohort. The annual incidence rates of methicillin-resistant S aureus colonization and infection were monitored, and characteristics of methicillin-resistant S aureus-colonized and -infected infants were compared. Data were collected from infant, maternal, and hospital laboratory records.

RESULTS

During the study period, 7997 infants were admitted to the NICU and 102 methicillin-resistant S aureus-colonized or -infected infants (1.3%) were identified. The incidence of methicillin-resistant S aureus decreased progressively from 1.79 cases per 1000 patient-days in 2000 to 0.15 cases per 1000 patient-days in 2005, but the incidence then increased to 1.26 cases per 1000 patient-days in 2007. Fifteen of the 102 case infants (14.7%) had invasive infections; no significant differences between infected and colonized infants were identified. Methicillin-resistant S aureus isolates with 14 different antibiograms were found during the study period. There was a shift from isolates predominantly likely to be hospital-associated in 2000-2004 to those likely to be community-associated in 2006-2007.

CONCLUSIONS

A continuous program of weekly methicillin-resistant S aureus surveillance cultures and isolation of affected infants was associated with a variable incidence of methicillin-resistant S aureus colonization over a 7-year study period. Methicillin-resistant S aureus was not eradicated from this tertiary-care NICU, and our data suggest that infants were colonized by multiple different methicillin-resistant S aureus strains during the study period.

The first vancomycin-intermediate Staphylococcus aureus strains isolated from patients in Thailand

We screened 533 and 361 methicillin (meticillin)-resistant Staphylococcus aureus strains isolated in a university hospital in 2002 and 2003 and in 2006 and 2007, respectively, and identified 4 (0.8%) of the strains in the first group and 8 (2.2%) of the strains in second group as heterogeneous vancomycin-resistant S. aureus (heterogeneous VISA) strains and 3 (0.8%) of the strains in the second group as VISA strains. This is the first report of VISA strains isolated from patients in Thailand.

Spread of methicillin-resistant Staphylococcus aureus USA300 in a neonatal intensive care unit

BACKGROUND

Reports of community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) in neonatal intensive care units (NICU) and in otherwise healthy patients without obvious risk factors have been increasing in frequency. Described herein is a cluster of cases of CA-MRSA USA300 strains in an NICU affecting infants, health-care workers and the health-care workers' families.

METHODS

Infants and health-care workers with infection and colonization due to MRSA between 1 January 2004 and 30 June 2005 in a tertiary care center NICU in San Antonio, TX were studied. Antimicrobial susceptibility testing and polymerase chain reaction detection of the mecA gene characterized the MRSA isolates. All MRSA cases were reviewed for clinical severity of infection and outcome.

RESULTS

During the 18 months studied, a total of four (0.6%) of 676 infants had CA-MRSA bacteremia or colonization. One infant with necrotizing pneumonia died and three health-care workers who directly cared for the infected infants developed soft-tissue infections caused by CA-MRSA. Four family members of two health-care workers subsequently developed soft-tissue infections. All of the analyzed isolates (eight of nine) belonged to pulsed-field type USA300 and possessed Panton-Valentine leukocidin genes, which have been associated with severe skin and soft-tissue infections, and necrotizing pneumonia.

CONCLUSIONS

It is likely that the CA-MRSA USA300 strain can be transmitted between NICU patients to health-care workers and their family members. The CA-MRSA cases reported here reinforce the virulence of CA-MRSA USA300 strains and emphasize the need to embrace infection control practices designed to protect hospitalized patients, health-care workers and their family members.

Using focus groups to revise an educational booklet for people living with methicillin-resistant Staphylococcus aureus (MRSA)

The incidence of methicillin-resistant staphylococcus aureus (MRSA) has grown in epidemic proportions; in many individuals, MRSA causes recurrent infections. MRSA infections can be transmitted from person to person through direct contact or contact with contaminated objects. Once confined to hospitalized individuals, MRSA is now seen in otherwise healthy individuals and congregate community settings. There is a demand for educational materials to guide MRSA patients in self-care, preventing recurrences, and reducing transmission. In 2004, Tacoma-Pierce County Health Department in Washington State led the effort to create an educational booklet for people with MRSA. Due to resource constraints, it was created without audience testing. In 2005, the revision of Living With MRSA involved audience testing using two focus groups comprising people living with MRSA and their families. This report describes the work of an interdisciplinary professional work group using focus groups to revise an educational booklet for people living with MRSA as patients, family members, and caregivers.

Clinical outcomes in methicillin-resistant Staphylococcus aureus-colonized neonates in the neonatal intensive care unit

BACKGROUND

Methicillin-resistant Staphylococcus aureus (MRSA) colonization can persist for prolonged periods, and patient-related factors are associated with persistent carriage in adults. However, such knowledge is lacking among neonates.

OBJECTIVES

To better understand the outcome of MRSA-colonized neonates in the neonatal intensive care unit (NICU), we prospectively followed all colonized neonates until decolonization over 39 months and determined the incidence, duration of colonization, clinical outcomes and risk factors associated with prolonged carriage of MRSA.

METHODS

Nasal and inguinal cultures were obtained from all newly admitted neonates following an outbreak of MRSA. Weekly and 1-2 monthly cultures were obtained from all hospitalized and discharged neonates colonized with MRSA, respectively, until 2 consecutive cultures were negative.

RESULTS

152 of 1,456 (10.4%) neonates became colonized. The mean time to acquire MRSA colonization was 17.1 +/- 40.7 (range 1-471) days. The median time to decolonization was 36 days. About 20% of decolonized patients had been colonized for a prolonged period of >or=160 days. 47.5% of colonized patients were sent home colonized, and none with prolonged carriage developed MRSA-related infections in the following 6 months in contrast to 6 infants (3.9%) who developed MRSA sepsis during hospitalization. The only risk factor associated with prolonged carriage was the concurrent colonization of both the inguinal and nasal areas on admission.

CONCLUSION

Nearly all neonates with acquired colonization became decolonized either prior to or after discharge from NICU. A significant percentage failed to decolonize prior to hospital discharge, but almost all decolonized by 30 months in the community without evidence of systemic or local infections.

Multiple cases of familial transmission of community-acquired methicillin-resistant Staphylococcus aureus

The worldwide emergence of community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) can have severe public health implications. Familial transmissions of CA-MRSA in The Netherlands were investigated. Among the families studied, two clusters of CA-MRSA could be identified. This report demonstrates that family members can serve as reservoirs of CA-MRSA which may become a serious problem in containing the spread of MRSA.

Fifteen-year study of the changing epidemiology of methicillin-resistant Staphylococcus aureus

PURPOSE

The study's purpose was to elucidate the evolutionary, microbiologic, and clinical characteristics of methicillin-resistant Staphylococcus aureus (MRSA) infections.

METHODS

MRSA cases from military medical facilities in San Diego, from 1990 to 2004, were evaluated and categorized as community-acquired or nosocomial. Sequence type, staphylococcal chromosomal cassette gene type, and Panton-Valentine leukocidin gene status were determined for a subset of isolates.

RESULTS

Over the 15-year period, 1888 cases of MRSA were identified; 65% were community acquired. The incidence (155 infections/100000 person-year in 2004) and household-associated cases rapidly increased since 2002. Among persons with community-acquired MRSA, 16% were hospitalized and only 17% were initially given an effective antibiotic. Community-acquired MRSA cases compared with nosocomial MRSA cases were more often soft-tissue and less often urinary, lung, or bloodstream infections (P<.001). Patients with community-acquired MRSA were younger (22 vs 64 years, P<.001) and less likely to have concurrent medical conditions (9% vs 98%, P<.001). Clindamycin resistance increased among community-acquired MRSA isolates during 2003 and 2004 compared with previous years (79% vs 13%, P<.001). Genetically, nosocomial MRSA isolates were significantly different than those acquired in the community. Although community-acquired MRSA isolates were initially diverse by 2004, one strain (staphylococcal chromosomal cassette type IV, sequence type 8, Panton-Valentine leukocidin gene positive) became the predominant isolate.

CONCLUSIONS

Community-acquired and intrafamilial MRSA infections have increased rapidly since 2002. Our 15 years of surveillance revealed the emergence of distinct community-acquired MRSA strains that were genetically unrelated to nosocomial MRSA isolates from the same community.

Father-to-infant transmission of community-acquired methicillin-resistant Staphylococcus aureus in a neonatal intensive care unit

Methicillin-resistant Staphylococcus aureus (MRSA) is increasingly being recognized as a cause of community-acquired infection. Its transmission in neonatal intensive care units (NICUs) has reportedly been linked to a few cases of community-acquired MRSA (CA-MRSA) infection. Here, I describe a case of CA-MRSA transmission from a father to his child in a NICU. Recognition that CA-MRSA may be transmitted in a hospital setting raises important issues for MRSA infection control and treatment options.

Family Outbreaks of Invasive Community-Associated Methicillin-Resistant Staphylococcus aureus Infection

Outbreaks of invasive methicillin-resistant Staphylococcus aureus infection within families are unusual. We investigated 2 family clusters of invasive methicillin-resistant Staphylococcus aureus infection, including 1 in which a young mother died of fulminant pneumonia. Although surveillance via culture of family contacts of patients with invasive methicillin-resistant Staphylococcus aureus infection is not currently recommended, such clusters should stimulate reevaluation of preventive measures.

Nasal carriage of methicillin-resistant Staphylococcus aureus in school children without identifiable risk factors in northern taiwan

In a nasal culture survey of school children, 5 (1.9%) of 262 school children and 18 (13%) of 137 health care workers (HCWs) were colonized with methicillin-resistant Staphylococcus aureus (MRSA). One common genotype accounted for most isolates from the school children and from the HCWs. Based on genotyping, MRSA strains circulating in the community in Taiwan were similar to the hospital strains.

Emergence of new strains of methicillin-resistant Staphylococcus aureus in a neonatal intensive care unit

BACKGROUND

Genetically distinct strains of methicillin-resistant Staphylococcus aureus (MRSA) of community rather than hospital origin have emerged in many areas of the United States. We determined if MRSA strains causing bacteremia in infants treated from birth in a neonatal intensive care unit (NICU) demonstrated the genetic traits of community-associated MRSA.

METHODS

A retrospective cohort study was conducted among NICU infants with bacteremia due to MRSA during 2003 in a large tertiary care center NICU in Houston. MRSA isolates were characterized by antimicrobial susceptibility testing and staphylococcal cassette chromosome mec (SCCmec) typing by polymerase chain reaction. All MRSA cases were reviewed for clinical severity of infection and outcome.

RESULTS

During 2003, a total of 8 (47%) of 17 infants with bacteremia due to S. aureus had MRSA infection. Isolates from 6 (75%) of these 8 infants carried the SCCmec genes (class B mec and ccr2) that are characteristic of community MRSA; 4 isolates were type IVa. All 6 isolates were resistant to beta-lactam antibiotics and erythromycin; 1 was also resistant to clindamycin. One isolate was nontypeable, and another carried the SCCmec type II gene (typical of hospital-associated strains) and was susceptible only to vancomycin. Seven (88%) of 8 infants presented in septic shock. Despite initial treatment with vancomycin, 3 (38%) died, and 3 survivors had complications requiring prolonged antimicrobial therapy; these 6 infants had MRSA isolates with genetic characteristics of isolates of community origin.

CONCLUSIONS

Community-associated MRSA strains have emerged as a significant cause of sepsis in neonates hospitalized in NICU since birth and have caused disseminated infection with substantial morbidity and mortality.

Features of invasive staphylococcal disease in neonates

OBJECTIVE

Most clinical descriptions of invasive staphylococcal disease (ISD) in neonates date from before the mid-1980s, when neonatal viability and intensive care differed substantially from current standards. We aimed to describe the contemporary incidence, clinical features, and outcome of infants with ISD in a neonatal intensive care unit.

METHODS

A retrospective cohort study was conducted of infants who had ISD and were in the neonatal intensive care unit of the Woman's Hospital of Texas, Houston, from January 2000 to June 2002. Confirmed ISD was defined as clinical sepsis and Staphylococcus aureus (SA) isolated from > or =1 blood culture (BC) or a sterile body site excluding urine or coagulase-negative staphylococci (CoNS) isolated from > or =2 BC or from 1 BC and a sterile body site. Probable ISD was defined as CoNS isolated from 1 BC or a sterile body site for which clinical and laboratory data review by 3 infectious disease specialists indicated that antimicrobial treatment was appropriate. Confirmed and combined confirmed plus probable cases were analyzed.

RESULTS

A total of 149 episodes (83 confirmed [39 SA, 44 CoNS], 66 probable) in 137 infants (mean gestational age [GA]: 27.6 weeks [22.4-36.4]; mean birth weight: 981 g [350-2995]) were reviewed. Four (3%) infants had early-onset infection (2 SA, 2 CoNS). Median age at infection onset was similar (17 days SA; 18 days CoNS). Intravascular catheters (IVC) were in situ in a minority of infants with ISD episodes (38% SA, 43% CoNS). CoNS more than SA infections were associated with very low birth weight (<1500 g), lower GA, a history of more IVCs and concurrent total parenteral nutrition, but IVC and parenteral nutrition days were similar. By multivariate analysis correcting for birth weight and complications of prematurity, hypoxia at the time of sepsis evaluation was significantly associated with CoNS and hypotension with SA infections; other clinical features were similar. Methicillin-resistant SA caused 8% of SA infections. Among bacteremic infants, SA more frequently than CoNS involved > or =2 sites. Overall, SA had more focal complications (primarily bone and joint) than CoNS, resulting in a 2- to 3-fold higher SA-associated morbidity rate. Mortality directly attributable to either organism was similar (5% SA; 5% confirmed, 3% confirmed/probable CoNS).

CONCLUSION

CoNS ISD occurred in smaller, more premature infants than SA and was IVC associated in a minority of cases. Hypoxia and hypotension were the only presenting features that differentiated CoNS and SA. SA-associated morbidity was substantial, but SA infection carried no greater risk of death (5%) than CoNS.

Nosocomial infection in the NICU: a medical complication or unavoidable problem?

Nosocomial sepsis is a serious problem for neonates who are admitted for intensive care. As it is associated with increases in mortality, morbidity, and prolonged length of hospital stay, both the human and fiscal costs of these infections are high. Although the rate of nosocomial sepsis increases with the degree of both prematurity and low birth weight, no specific lab test has been shown to be very useful in improving our ability to predict who has a "real" blood-stream infection and, therefore, who needs to be treated with a full course of antibiotics. As a result, antibiotic use is double the rate of "proven" sepsis and we are facilitating the growth of resistant organisms in the neonatal intensive care unit. The purpose of this article is to review the topic of nosocomial infections in neonates.

Community-acquired Methicillin-resistant Staphylococcus aureus: Epidemiology and Potential Virulence Factors

Methicillin-resistant Staphylococcus aureus (MRSA) has been isolated from patients in the community. Some of these strains may have origins in the hospital, but others appear to be novel and unrelated to known hospital strains. Community MRSA strains have several distinguishing characteristics that may enable them to more readily colonize and infect otherwise healthy individuals. This article reviews recent publications addressing the epidemiology of MRSA in the community, risk factors associated with carriage, potentially associated virulence factors, and concepts of strain fitness as they pertain to MRSA. MRSA likely will be an increasingly important pathogen in the community.

[Staphylococcal pneumonia in a premature neonate: unusual transmission of nosocomial infection]

Late onset of neonatal infection could have been transmitted in prenatal period, but it is usually secondary to a postnatal transmission.

CASE REPORT

A premature neonate developed staphylococcal pneumonia at 18 days of life. Genomic typing of the strains of Staphylococcus aureus obtained from the patient and from his mother (found in the endocervix culture 48 h before delivery) was identical. These strains were different from those isolated in other neonates colonised by S. aureus in the unit during at that moment.

CONCLUSION

The observed case of staphylococcal pneumonia may correspond to a nosocomial infection secondary to a pre- or postnatal transmission of the agent by the mother.

Prevalence of and risk factors for colonization with methicillin-resistant Staphylococcus aureus in an outpatient clinic population

OBJECTIVES

To determine the prevalence of methicillin-resistant Staphylococcus aureus (MRSA) colonization in an outpatient population and to identify risk factors for MRSA colonization.

DESIGN

Surveillance cultures were performed during outpatient visits to identify S. aureus colonization. A case-control study was performed to identify risk factors for MRSA colonization.

SETTING

Primary care internal medicine clinic.

PATIENTS

Adults presenting for non-acute primary care (N = 494).

RESULTS

S. aureus was isolated from 122 (24.7%) of the patients for whom cultures were performed. Methicillin-susceptible S. aureus was isolated from 107 (21.7%) of the patients, whereas MRSA was isolated from 15 (3.0%) of the patients. All MRSA isolates were resistant to multiple non-beta-lactam antimicrobial agents. In multivariate analyses, MRSA colonization was independently associated with admission to a nursing home (adjusted odds ratio [OR], 103; 95% confidence interval [CI95], 7 to 999) or hospital in the previous year, although the association with hospital admission was observed only among those without chronic illness (adjusted OR, 7.1; CI95, 1.3 to 38.1). In addition, MRSA colonization was associated with the presence of at least one underlying chronic illness, although this association was observed only among those who had not been hospitalized in the previous year (adjusted OR, 5.1; CI95, 1.2 to 21.9).

CONCLUSIONS

We found a low prevalence of MRSA colonization in an adult outpatient population. MRSA carriers most likely acquired the organism through contact with healthcare facilities rather than in the community. These data show that care must be taken when attributing MRSA colonization to the community if detected in outpatients or during the first 24 to 48 hours of hospitalization.

Spread of methicillin-resistant Staphylococcus aureus (MRSA) among household contacts of individuals with nosocomially acquired MRSA

OBJECTIVE

To determine the frequency with which methicillin-resistant Staphylococcus aureus (MRSA) is spread from colonized or infected patients to their household and community contacts.

DESIGN

Retrospective cohort study.

SETTING

University hospital.

PARTICIPANTS

Household and community contacts of MRSA-colonized or -infected patients for whom MRSA screening cultures were performed.

RESULTS

MRSA was isolated from 25 (14.5%) of 172 individuals. Among the contacts of index patients who had at least one MRSA-colonized contact, those with close contact to the index patient were 7.5 times more likely to be colonized (53% vs 7%; 95% confidence interval, 1.1 to 50.3; P = .002). An analysis of antimicrobial susceptibility and DNA fingerprint patterns suggested person-to-person spread.

CONCLUSIONS

MRSA colonization occurs frequently among household and community contacts of patients with nosocomially acquired MRSA, suggesting that transmission of nosocomially acquired MRSA outside of the healthcare setting may be a substantial source of MRSA colonization and infection in the community.

Risk of methicillin-resistant Staphylococcus aureus infection after previous infection or colonization

Studies evaluating the risk of methicillin-resistant Staphylococcus aureus (MRSA)-associated sequelae in colonized or infected inpatients have not extended follow-up into the period after discharge from the hospital. We determined the 18-month risk of MRSA infection among 209 adult patients newly identified as harboring MRSA. Twenty-nine percent of patients (60 patients) developed subsequent MRSA infections (90 infections). These infections were often severe. Twenty-eight percent of infections (25 of 90) involved bacteremia, and 56% (50 of 90) involved pneumonia, soft tissue infection, osteomyelitis, or septic arthritis. Eighty percent of patients (48 of 60) with subsequent MRSA infection developed the infection at a new site, and 49% of new MRSA infections (44 of 90) first became manifest after discharge from the hospital. Accurate assessment of the risk of MRSA-associated sequelae requires prolonged follow-up after discharge.

Asymptomatic nasal carriage of mupirocin-resistant, methicillin-resistant Staphylococcus aureus (MRSA) in a pet dog associated with MRSA infection in household contacts

Recurrent methicillin-resistant Staphylococcus aureus (MRSA) infection in a patient with diabetes and in his wife is described. Culture of nares samples from the family dog grew mupirocin-resistant (minimum inhibitory concentration >1024 microg/mL) MRSA that had a pulsed-field gel electrophoresis chromosomal pattern identical to the MRSA isolated from the patient's nares and his wife's wound. Further recurrence of MRSA infection and nasal colonization in the couple was prevented only after successful eradication of MRSA from the family dog's nares.

Community-acquired methicillin-resistant Staphylococcus aureus: a meta-analysis of prevalence and risk factors

Reports suggest that carriage of methicillin-resistant Staphylococcus aureus (MRSA) among persons without health care-associated risks has increased. A meta-analysis of studies reporting the prevalence of community-acquired MRSA (CA-MRSA) among MRSA isolates from hospitalized patients or the prevalence of MRSA colonization among community members was conducted. The CA-MRSA prevalence among hospital MRSA was 30.2% in 27 retrospective studies and 37.3% in 5 prospective studies; 85% of all patients with CA-MRSA had > or =1 health care-associated risk. The pooled MRSA colonization rate among community members was 1.3% (95% confidence interval [CI], 1.04%-1.53%), but there was significant heterogeneity among study populations. Community members from whom samples were obtained in health care facilities were more likely to be carrying MRSA than were community members from whom samples were obtained outside of the health care setting (relative risk, 2.35; 95% CI, 1.56-3.53). Among studies that excluded persons with health care contacts, the MRSA prevalence was 0.2%. Moreover, most persons with CA-MRSA had > or =1 health care-associated risk, which suggests that the prevalence of MRSA among persons without risks remains low (< or =0.24%). Effective control of dissemination of MRSA throughout the community likely will require effective control of nosocomial MRSA transmission.

Staphylococcus aureus Carriage and Health Care-acquired Infection

Staphylococcus aureus is one of the most common nosocomial pathogens. Its propensity to establish prolonged carriage among hospitalized patients and increasing resistance to antibiotics makes control of this organism within the hospital difficult. High-level vancomycin resistance has now been reported in a single clinical isolate of S. aureus, emphasizing the need to increase efforts to control nosocomial spread. Knowledge of the epidemiology of S. aureus colonization among patients has shed new light on the potential difficulties in interrupting nosocomial transmission. Effective control of S. aureus within the hospital and community will require more aggressive measures that include earlier diagnosis of colonized patients, better handwashing and barrier precaution measures, and renewed efforts to eradicate the carriage state.

Nosocomial transmission of methicillin-resistant Staphylococcus aureus from a mother to her preterm quadruplet infants

BACKGROUND

Patient-to-patient transmission of methicillin-resistant Staphylococcus aureus (MRSA) in neonatal intensive care units (NICUs) has been well described. We report the first documented outbreak of probable transmission of MRSA from a mother to 3 of her preterm quadruplet infants postnatally.

METHODS

Routine surveillance of clinical microbiologic laboratory reports revealed an increased incidence of MRSA infections in our NICU, including 3 of 4 preterm quadruplets. Surveillance cultures of the anterior nares of all patients and the quadruplets' parents were performed to detect MRSA carriage. The isolates were typed by pulsed-field gel electrophoresis with the restriction endonuclease SmaI. Infection control strategies included mupirocin treatment and contact isolation precautions for infected/colonized infants.

RESULTS

Clinical cultures from infants A, C, and D and surveillance cultures of the quadruplets' mother and 2 additional unrelated infants grew the same clone of MRSA. The mother's only identified risk factors for MRSA acquisition were 2 prepartum hospitalizations related to the multiple gestation and previous treatment with antibiotics. All anterior nares cultures were negative for MRSA after mupirocin treatment.

CONCLUSIONS

Use of gowns and gloves by the family members of women with multiple gestations should be recommended to prevent transmission of potential pathogens in the NICU.

Antibiotic resistance patterns of bacterial isolates from blood in San Francisco County, California, 1996-1999

Countywide antibiotic resistance patterns may provide additional information from that obtained from national sampling or individual hospitals. We reviewed susceptibility patterns of selected bacterial strains isolated from blood in San Francisco County from January 1996 to March 1999. We found substantial hospital-to-hospital variability in proportional resistance to antibiotics in multiple organisms. This variability was not correlated with hospital indices such as number of intensive care unit or total beds, annual admissions, or average length of stay. We also found a significant increase in methicillin-resistant Staphylococcus aureus, vancomycin-resistant Enterococcus, and proportional resistance to multiple antipseudomonal antibiotics. We describe the utility, difficulties, and limitations of countywide surveillance.

Prevalence of methicillin-resistant Staphylococcus aureus carriage at the time of admission in two acute geriatric wards

Studies on methicillin-resistant Staphylococcus aureus (MRSA) in the elderly have been concerned with patients hospitalized in nursing homes or long-term care facilities. Our objective was to estimate the prevalence of MRSA at the time of admission in two acute geriatric wards with high endemic MRSA incidence in a French teaching hospital. A prospective screening of MRSA carriers was conducted by swabbing nares and wounds during five weeks for all patients on the day of admission. For each patient demographic, administrative, clinical and therapeutic data were recorded. Their associations with MRSA carriage were studied by logistic regression analysis. On the day of admission, 35 patients (14.6%) were MRSA carriers. Variables independently associated with carriage were hospitalization within the six last months (OR = 4.64; P < 0.001) and the existence of wounds or bedsores (OR = 2.864; P = 0.02). The high prevalence of MRSA carriage at the time of admission could explain in part the high incidence of MRSA in these wards. A systematic selective screening targeted on patients with high risk of carriage should be helpful to implement barrier precautions and reduce cross-transmission.

Duration of colonization by methicillin-resistant Staphylococcus aureus after hospital discharge and risk factors for prolonged carriage

To investigate persistent carriage of methicillin-resistant Staphylococcus aureus (MRSA), we conducted a prospective 10-month study of MRSA carriage in previous carriers who were readmitted to our hospital. Four screening specimens, 2 from the skin and 2 from the nares, were obtained within 3 days after admission, in addition to diagnostic specimens requested by physicians. Of the 78 patients included in our study, 31 (40%) were persistent carriers of MRSA, with an estimated median time of 8.5 months to MRSA clearance. In the multivariate analysis, the only factor significantly associated with persistent carriage was the presence of a break in the skin at readmission (odds ratio, 4.34; P=.004); however, a trend was found for admission from a chronic-care institution (odds ratio, 3.65; P=.06). Our data confirm that prolonged carriage of MRSA can occur after hospital discharge, support routine screening for MRSA at readmission of previously MRSA-positive patients, and suggest that a particularly high index of suspicion for MRSA carriage should be maintained if these patients have a break in the skin.

Breast milk transmission of a Panton-Valentine leukocidin-producing Staphylococcus aureus strain causing infantile pneumonia

We report on a 38-day-old infant who developed pleuropneumonia due to a Staphylococcus aureus strain responsible for familial furunculosis, which was acquired by maternal breast-feeding. All isolates from the infant and parents were genetically related by randomly amplified polymorphic DNA analysis and produced Panton-Valentine leukocidin.

MRSA carriage: the relationship between community and healthcare setting. A study in an Italian hospital

From May 1997 to June 1998, all patients admitted to the study institution were screened at entry for MRSA carriage (both colonization and infection). Eighty-six MRSA carriers were identified; of these, 85 were nasal carriers. Risk factors were compared to those of 86 controls. Although the vast majority of both carriers and controls had at least one previous hospital stay, carriers were less likely than controls to be referred from a community setting, and had resided within the community for a shorter time before the current admission. The number of underlying conditions was comparable in the two groups, but those infected were more likely to have cancer than the controls. While community-acquired MRSA carriage is rare, exposure to a health care setting (particularly if repeated) within six months from the current admission, is a risk factor for MRSA carriage and introduction of the organism into an institution.

Hospital- and community-based surveillance of methicillin-resistant Staphylococcus aureus: previous hospitalization is the major risk factor

OBJECTIVE

The purpose of the study was to determine the incidence and risk factors for the acquisition of methicillin-resistant Staphylococcus aureus (MRSA) in our community.

DESIGN

This study used a cross-sectional design to assess patients colonized or infected with MRSA.

PATIENTS

The study population consisted of residents of London, Ontario, Canada, who were identified as MRSA-positive for the first time in 1997.

SETTING

All acute- and chronic-care hospitals, long-term healthcare facilities, and community physicians' offices in the city of London participated in the study.

MAIN OUTCOME MEASURE

Incidence of MRSA in the community, risk factors for acquisition, especially previous hospitalization over a defined period, and strain type were evaluated.

RESULTS

In 1997, 331 residents of London were newly identified as MRSA-positive, representing an annual incidence of 100/100,000 persons (95% confidence interval, 88.8-110.7). Thirty-one (9.4%) individuals were not healthcare-facility patients in the previous month, and 11 (3.3%), 10 (3.0%), and 6 (1.8%) individuals had no such contact in the previous 3, 6, and 12 months, respectively. One hundred seventy-seven strains, including five of the isolates from patients with no healthcare-facility contact in the previous year, were typed. One hundred sixty (90.3%) of these isolates, including all typed strains from patients with no healthcare facility contact, belonged to a single clone.

CONCLUSION

These findings demonstrate that the incidence of MRSA is higher than previously reported and that hospital contact is the single most important risk factor for the acquisition of MRSA in our community. Screening for MRSA in previously hospitalized patients at the time of hospitalization may reduce nosocomial spread and indirectly reduce the incidence of MRSA in the community.