Pulsed-field Typing Research Articles

Clostridium difficile: changing epidemiology and new treatment options

The review summarizes changes in the epidemiology and treatment of Clostridium difficile-associated disease. Recent outbreaks of Clostridrium difficile-associated diarrhoea with increased severity, high relapse rate and significant mortality, have been related to the emergence of a new, hypervirulent C. difficile strain in north America, Japan and Europe. Definitions have been proposed by the European Centre for Disease Prevention and Control to identify severe cases of Clostridrium difficile-associated diarrhoea and to differentiate community-acquired cases from nosocomial-acquired cases. The emerging strain is referred to as North American pulsed-field type 1 and polymerase chain reaction ribotype 027. The emerging strain has also been detected in calf diarrhoea and ground meat samples in Canada. Attempts to prevent outbreaks caused by type 027 should focus on controlling the overall use of antibiotics, and high-risk antibiotics such as cephalosporins, clindamycin and fluoroquinolones. Several new antibiotic and non-antibiotic alternatives have become available; there is currently no place for probiotic treatments. Patients who suffer multiple relapses of C. difficile-associated diarrhoea present a major therapeutic challenge. The early recognition of Clostridrium difficile-associated diarrhoea caused by NAP1/027 is necessary to start rapid treatment, to prevent complications, and to prevent further spread of the bacterium.

Quinolone Resistance of Salmonella enterica Serovar Virchow Isolates from Humans and Poultry in Israel: Evidence for Clonal Expansion

Salmonella enterica serovar Virchow is highly prevalent in humans and farm animals in Israel. In addition to high rates of resistance to multiple antibiotics, this serovar exhibits a high incidence of resistance to nalidixic acid. More than 90% of Salmonella serovar Virchow isolates of human and poultry origin obtained from 1997 to 2004 were resistant to nalidixic acid (MIC > or = 128 microg/ml), with reduced susceptibility to ciprofloxacin (MIC between 0.125 and 0.250 microg/ml). Most isolates belonged to two predominant, closely related pulsed-field gel electrophoresis image types. Investigation of the mechanisms of quinolone resistance revealed that this pathogen probably emerged from a parental clone that overproduced the AcrAB efflux pump and had a single point mutation in gyrA leading to the Asp87Tyr substitution. The close resemblance between human and poultry isolates points to poultry as a likely source of Salmonella serovar Virchow in the food chain.

Comparative activity of telavancin against isolates of community-associated methicillin-resistant Staphylococcus aureus

This study compared the activity of telavancin, a novel multivalent lipoglycopeptide with rapid bactericidal activity, with those of five standard antibiotics for methicillin-resistant Staphylococcus aureus (MRSA) against isolates of community-associated MRSA (CA-MRSA). Microdilution tests performed according to CLSI guidelines using cation-adjusted Mueller-Hinton broth were used to determine the MIC values of telavancin, quinupristin/dalfopristin, vancomycin, trimethoprim/sulfamethoxazole, linezolid and daptomycin versus 60 CA-MRSA isolates. MBC values of telavancin were determined according to CLSI guidelines and American Society for Microbiology standards. PFGE was performed using the restriction enzyme SmaI. Samples from three predominant pulsed-field types were typed by multilocus sequence typing. Staphylococcal cassette chromosome mec typing was determined by multiplex PCR. The Panton-Valentine leucocidin (PVL) genes (lukS-PV and lukF-PV) were identified by PCR. The telavancin MIC90 and MBC90 values for this collection of 60 CA-MRSA isolates were 0.5 and 1 mg/L, respectively, with MIC and MBC values both ranging from 0.25 to 1 mg/L. Telavancin was found to be bactericidal in this study, as its MBC was no more than 2-fold higher than its MIC for all CA-MRSA isolates tested except one. (A single isolate yielded an MBC/MIC ratio of 4.) PVL- and non-PVL-producing strains demonstrated similar susceptibility to telavancin and comparator agents. Based on in vitro activity, telavancin should be an effective agent against CA-MRSA.

Update of Clostridium difficile-associated disease due to PCR ribotype 027 in Europe

Recent outbreaks of Clostridium difficile-associated diarrhoea (CDAD) with increased severity, high relapse rate and significant mortality have been related to the emergence of a new, hypervirulent C. difficile strain in North America, Japan and Europe. Definitions have been proposed by the European Centre of Disease Prevention and Control (ECDC) to identify severe cases of CDAD and to differentiate community-acquired cases from nosocomial CDAD (http://www.ecdc.europa.eu/documents/pdf/Cl_dif_v2.pdf). CDAD is mainly known as a healthcare-associated disease, but it is also increasingly recognised as a community-associated disease. The emerging strain is referred to as North American pulsed-field type 1 (NAP1) and PCR ribotype 027. Since 2005, individual countries have developed surveillance studies to monitor the spread of this strain. C. difficile type 027 has caused outbreaks in England and Wales, Ireland, the Netherlands, Belgium, Luxembourg, and France, and has also been detected in Austria, Scotland, Switzerland, Poland and Denmark. Preliminary data indicated that type 027 was already present in historical isolates collected in Sweden between 1997 and 2001.

Epidemiology of Methicillin-Resistant Staphylococcus aureus at a Pediatric Healthcare System, 1991–2003

The emergence and epidemiology of methicillin-resistant Staphylococcus aureus (MRSA) at a Minneapolis pediatric healthcare facility was investigated. Children with MRSA infections from January 1991 to December 2003 were classified as community-associated (CA) or healthcare-associated (HA) using established criteria. Isolates were subtyped using pulsed-field gel electrophoresis and grouped into pulsed-field types (PFTs). Case and isolate characteristics were compared and temporal trends were assessed. The first isolate classified as CA-MRSA in this healthcare facility was identified in 1991. CA-MRSA cases (n = 188) were more likely than HA-MRSA cases (n = 83) to have a skin or soft tissue infection (80% versus 59%) and to belong to a racial or ethnic minority group (82% versus 55%), whereas HA-MRSA cases were younger (median age, 3.4 years versus 4.9 years). The proportion of both CA- and HA-MRSA isolates susceptible to clindamycin and erythromycin declined during the study period. Isolates classified as CA-MRSA were more likely than HA-MRSA isolates to be USA300 (21% versus 11%, P = 0.05) and USA400 (62% versus 31%, P < 0.001) PFTs. Associations between case race/ethnicity and isolate PFT were observed independent of case classification. CA-MRSA is well established in this pediatric population. Although no discernable changes in CA- or HA-MRSA case characteristics were documented during the study period, significant changes were observed in CA-MRSA isolate characteristics, indicating that this pathogen continues to evolve.

A Portrait of the Geographic Dissemination of the Clostridium difficile North American Pulsed-Field Type 1 Strain and the Epidemiology of C. difficile-Associated Disease in Quebec

An increase in the incidence and severity of Clostridium difficile-associated disease in Québec and the United States has been associated with a hypervirulent strain referred to as North American pulsed-field type 1 (NAP1)/027. In 2005, a prospective study was conducted in 88 Québec hospitals, and 478 consecutive nosocomial isolates of C. difficile were obtained. The isolates were subjected to pulsed-field gel electrophoresis (PFGE) typing, antimicrobial susceptibility testing, and detection of binary toxin genes and tcdC gene deletion. Data on patient age and occurrence of complications were collected. PFGE typing of 478 isolates of C. difficile yielded 61 PFGE profiles. Pulsovars A (57%), B (10%), and B1 (8%) were predominant. The PFGE profile of pulsovar A was identical to that of strain NAP1. It showed 67% relatedness with 15 other PFGE patterns, among which 11 had both binary toxin genes and a partial tcdC deletion but different antibiotic susceptibility profiles. Pulsovars B and B1 were identical to strain NAP2/ribotype 001. In hospitals showing a predominant clonal A or B-B1 PFGE pattern, incidence of C. difficile-associated disease was 2 and 1.3 times higher, respectively, than in hospitals without any predominant clonal PFGE pattern. Severe disease was twice as frequent among patients with strains possessing binary toxin genes and tcdC deletion than among patients with strains lacking these virulence factors. This study helped to quantify the impact of strain NAP1 on the incidence and severity of C. difficile-associated disease in Québec in 2005. The identification of the geographic dissemination of this predominant strain may help to focus regional infection-control efforts.

Clinical and molecular epidemiology of nursing home–associated Staphylococcus aureus bacteremia

Although nursing home residents who have Staphylococcus aureus bacteremia (SAB) have been included in large studies of this infection, there are no published descriptions of SAB solely in nursing home residents. The objectives were to describe the clinical and molecular epidemiology of SAB in nursing home residents admitted to one hospital. This was a retrospective review of hospital medical records of nursing home residents from 22 separate facilities who had SAB and were admitted to a specialty unit at one hospital from 1997 to 2003. For the seven-year study period, 39 episodes of SAB were identified; 15 were due to methicillin-susceptible S. aureus (MSSA) and 24 were due to methicillin-resistant S. aureus (MRSA). The incidence of SAB among all residents admitted to the specialty unit increased by more than eightfold primarily because of an increased incidence of bacteremia due to MRSA. The most common identified source was the urinary tract (18% of all episodes) but for 17 (44%) episodes, no focus was identified. Hospital mortality was 28% with all deaths occurring within 15 days of admission. Analysis of the MRSA strains by pulsed-field gel electrophoresis revealed that two pulsed-field types predominated when compared with the CDC national database: USA100- (N = 13) and USA 800-like strains (N = 7). In the study population there was a substantial increase in incidence of SAB over a 7-year period due almost exclusively to an increased occurrence of MRSA. Hospital strains of MRSA predominated, as one would expect. Mortality was high but complications were low among survivors. These findings have important implications for choosing empiric antibiotic therapy in nursing home residents who have suspected S. aureus infection.

COMMUNITY-ASSOCIATED METHICILLIN-RESISTANT STAPHYLOCOCCUS AUREUS NECROTIZING FASCIITIS IN A NEONATE

Neonatal necrotizing fasciitis is rare and is predominantly associated with methicillin-susceptible Staphylococcus aureus (MSSA). Necrotizing fasciitis associated with community-associated methicillin-resistant S aureus (CA-MRSA) has only recently been reported in the literature, primarily among adults. We present a case of a previously healthy neonate with necrotizing fasciitis of the back caused by CA-MRSA, pulsed-field type USA-300. We describe a 5-day-old infant with necrotizing fasciitis of the back caused by CA-MRSA. Treatment of necrotizing fasciitis requires prompt medical evaluation, prompt surgical debridement, and appropriate antibiotic selection. The potential involvement of CA-MRSA in necrotizing fasciitis in children needs to be considered before institution of antibiotics.

Molecular epidemiology and household transmission of community-associated methicillin-resistant Staphylococcus aureus in Hong Kong

This study evaluated the clinical and epidemiologic features of individuals with community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) in Hong Kong from January 2004 through December 2005. Twenty-four episodes of skin and soft tissue infections and 1 episode of meningitis due to CA-MRSA were identified. CA-MRSA infections or carriage was found in 6 (13%) of 46 household contacts. A total of 29 isolates were analyzed by the Staphylococcus cassette chromosome mec (SCC mec) typing, pulsed-field gel electrophoresis (PFGE), and multilocus sequence typing. In addition, polymerase chain reaction detection of the genes encoding Panton-Valentine leukocidin was also carried out. It was observed that 24 had SCC mec IV/IVA and 5 had SCC mec V, and 23 were pvl positive. PFGE analysis clustered all except 1 isolate into 3 pulsed-field types (PFTs), HKU100 through HKU300. The HKU100 isolates had genotype ST30-IV identical to the Southwest Pacific clone. The HKU200 isolates belonged to ST59-V and were multiresistant, including an ermB-mediated macrolide resistance trait, which is characteristic of the predominant CA-MRSA clone in Taiwan. The HKU300 isolates had unique features (ST8, Panton–Valentine leukocidin negative, and SCC mec IVA) typical of CA-MRSA in Japan. In conclusion, CA-MRSA has a propensity to spread within families. Our findings showed that CA-MRSA strains in Hong Kong have diverse genetic backgrounds.

Emergence of community-associated methicillin resistant Staphylococcus aureus in Hawaii, 2001–2003

We conducted a retrospective study to determine trends and characteristics of community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) in Hawaii. We reviewed medical records of patients with MRSA infections during July 2001-June 2003 in four healthcare facilities. A case was defined as a patient with MRSA infection (colonization excluded), diagnosed in ambulatory settings or < or = 48 h after hospitalization, without previous MRSA or healthcare risk factors. Pulsed-field gel electrophoresis (PFGE) and typing of resistance and toxin genes was performed in 40 MRSA isolates. CA-MRSA infections increased from 28 (23% of MRSA infections) to 65 (32%) per quarter over the 2-year period (P<0.05). Pacific islanders accounted for 51% of 389 case-patients, but only 24% of the Hawaii population. In the pediatric hospital, Pacific Islanders represented 76% of 90 case-patients versus 35% of the hospital population. Hospital admission, required for 40% (154/389), was associated with prior antimicrobial treatment (P<0.01). The staphylococcal cassette chromosome mec type IV was detected in 38/40 isolates; 31 isolates carried Panton-Valentine leukocidin genes and 22 belonged to the same staphylococcal lineage. In Hawaii, prevention strategies for CA-MRSA infections should focus on Pacific Islanders. CA-MRSA infections in Hawaii appear to be related to strains causing disease throughout the United States.

Methicillin-ResistantS. aureusInfections among Patients in the Emergency Department

Methicillin-resistant Staphylococcus aureus (MRSA) is increasingly recognized in infections among persons in the community without established risk factors for MRSA. We enrolled adult patients with acute, purulent skin and soft-tissue infections presenting to 11 university-affiliated emergency departments during the month of August 2004. Cultures were obtained, and clinical information was collected. Available S. aureus isolates were characterized by antimicrobial-susceptibility testing, pulsed-field gel electrophoresis, and detection of toxin genes. On MRSA isolates, we performed typing of the staphylococcal cassette chromosome mec (SCCmec), the genetic element that carries the mecA gene encoding methicillin resistance. S. aureus was isolated from 320 of 422 patients with skin and soft-tissue infections (76 percent). The prevalence of MRSA was 59 percent overall and ranged from 15 to 74 percent. Pulsed-field type USA300 isolates accounted for 97 percent of MRSA isolates; 74 percent of these were a single strain (USA300-0114). SCCmec type IV and the Panton-Valentine leukocidin toxin gene were detected in 98 percent of MRSA isolates. Other toxin genes were detected rarely. Among the MRSA isolates, 95 percent were susceptible to clindamycin, 6 percent to erythromycin, 60 percent to fluoroquinolones, 100 percent to rifampin and trimethoprim-sulfamethoxazole, and 92 percent to tetracycline. Antibiotic therapy was not concordant with the results of susceptibility testing in 100 of 175 patients with MRSA infection who received antibiotics (57 percent). Among methicillin-susceptible S. aureus isolates, 31 percent were USA300 and 42 percent contained pvl genes. MRSA is the most common identifiable cause of skin and soft-tissue infections among patients presenting to emergency departments in 11 U.S. cities. When antimicrobial therapy is indicated for the treatment of skin and soft-tissue infections, clinicians should consider obtaining cultures and modifying empirical therapy to provide MRSA coverage.

Emergence of community-acquired methicillin-resistant Staphylococcus aureus USA 300 clone as the predominant cause of skin and soft-tissue infections.

Studies have shown that community-acquired methicillin-resistant Staphylococcus aureus (MRSA) causes S. aureus skin and soft-tissue infection in selected populations. To determine the proportion of infections caused by community-acquired MRSA, the clinical characteristics associated with community-acquired MRSA, and the molecular epidemiology of community-acquired MRSA among persons with community-onset S. aureus skin and soft-tissue infection. Active, prospective laboratory surveillance to identify S. aureus recovered from skin and soft-tissue sources. 1000-bed urban hospital and its affiliated outpatient clinics in Atlanta, Georgia. 384 persons with microbiologically confirmed community-onset S. aureus skin and soft-tissue infection. Proportion of infections caused by and clinical factors associated with community-acquired MRSA among persons with community-onset S. aureus skin and soft-tissue infection. Pulsed-field gel electrophoresis and antimicrobial susceptibility patterns were used to epidemiologically classify community-onset S. aureus infections. Community-acquired MRSA was defined by MRSA isolates that either demonstrated a USA 300 or USA 400 pulsed-field type or had a susceptibility pattern showing resistance only to beta-lactams and erythromycin (for isolates not available for pulsed-field gel electrophoresis). Community-onset skin and soft-tissue infection due to S. aureus was identified in 389 episodes, with MRSA accounting for 72% (279 of 389 episodes). Among all S. aureus isolates, 63% (244 of 389 isolates) were community-acquired MRSA. Among MRSA isolates, 87% (244 of 279 isolates) were community-acquired MRSA. When analysis was restricted only to MRSA isolates that were available for pulsed-field gel electrophoresis, 91% (159 of 175 isolates) had a pulsed-field type consistent with community-acquired MRSA; of these, 99% (157 of 159 isolates) were the MRSA USA 300 clone. Factors independently associated with community-acquired MRSA infection were black race (prevalence ratio, 1.53 [95% CI, 1.16 to 2.02]), female sex (prevalence ratio, 1.16 [CI, 1.02 to 1.32]), and hospitalization within the previous 12 months (prevalence ratio, 0.80 [CI, 0.66 to 0.97]). Inadequate initial antibiotic therapy was statistically significantly more common among those with community-acquired MRSA (65%) than among those with methicillin-susceptible S. aureus skin and soft-tissue infection (1%). Some MRSA isolates were not available for molecular typing. The community-acquired MRSA USA 300 clone was the predominant cause of community-onset S. aureus skin and soft-tissue infection. Empirical use of agents active against community-acquired MRSA is warranted for patients presenting with serious skin and soft-tissue infections.

Epidemiological typing of MRSA isolates from blood cultures taken in Irish hospitals participating in the European Antimicrobial Resistance Surveillance System (1999–2003)

Between 1999 and 2003, meticillin-resistant Staphylococcus aureus (MRSA) isolates recovered from blood cultures in Irish hospitals that participate in the European Antimicrobial Resistance Surveillance System were investigated by epidemiological typing using antibiogram-resistogram (AR) typing, biotyping, and DNA macrorestriction digestion using SmaI followed by pulsed-field gel electrophoresis (PFGE). PFGE patterns were assigned five-digit pulsed-field type (PFT) numbers, and PFTs of apparently related patterns were abbreviated to two-digit PFT groups (PFGs). AR and PFGE typing results were combined to produce AR-PFG types. Representative isolates of each AR-PFG type recovered in 2002 were typed by multilocus sequence typing and staphylococcal cassette chromosome (SCC) mec analysis. Isolates from 1999 and 2000 were also typed by phage typing. The extent to which epidemiological types of MRSA from blood cultures could be extrapolated to the total MRSA population was investigated by comparing results obtained with isolates from the total MRSA population versus those obtained with blood cultures during three study periods. Over the 5 years from 1999 to 2003, 1,580 blood culture isolates from 1,495 patients were analysed. Typeability and discriminatory indices were as follows: AR typing, 1 and 0.97; phage typing, 0.29 and 0.89; PFGE, 0.99 and 0.95; AR-PFG typing, 1 and 0.95. The most frequently occurring AR-PFG types were 06-01, 07-02, 13-00, and 14-00 and were exhibited by 57, 7, 14, and 12% of isolates, respectively. During the study period, the distribution of AR-PFG type changed markedly, with the prevalence of one type (AR-PFG 06-01) increasing by 880%, from 22% (39/181) in 1999 to 80% (343/430) in 2003. Investigation of whether epidemiological types among blood culture isolates of MRSA were representative of the total MRSA population showed that there was no significant difference in most instances. MLST and SCCmec typing showed that AR-PFG types 06-01, 07-02, 13-00, and 14-00 were ST22-MRSA-IV, ST36-MRSA-II, ST8-MRSA-IID, and ST8-MRSA-IIE, respectively.

Prevalence ofStaphylococcus aureusNasal Colonization in the United States, 2001–2002

Staphylococcus aureus is a common cause of disease, particularly in colonized persons. Although methicillin-resistant S. aureus (MRSA) infection has become increasingly reported, population-based S. aureus and MRSA colonization estimates are lacking. Nasal samples for S. aureus culture and sociodemographic data were obtained from 9622 persons > or = 1 year old as part of the National Health and Nutrition Examination Survey, 2001-2002. After screening for oxacillin susceptibility, MRSA and selected methicillin-susceptible S. aureus isolates were tested for antimicrobial susceptibility, pulsed-field gel electrophoresis clonal type, toxin genes (e.g., for Panton-Valentine leukocidin [PVL]), and staphylococcal cassette chromosome mec (SCCmec) type I-IV genes. For 2001-2002, national S. aureus and MRSA colonization prevalence estimates were 32.4% (95% confidence interval [CI], 30.7%-34.1%) and 0.8% (95% CI, 0.4%-1.4%), respectively, and population estimates were 89.4 million persons (95% CI, 84.8-94.1 million persons) and 2.3 million persons (95% CI, 1.2-3.8 million persons), respectively. S. aureus colonization prevalence was highest in participants 6-11 years old. MRSA colonization was associated with age > or = 60 years and being female but not with recent health-care exposure. In unweighted analyses, the SCCmec type IV gene was more frequent in isolates from participants of younger age and of non-Hispanic black race/ethnicity; the PVL gene was present in 9 (2.4%) of 372 of isolates tested. Many persons in the United States are colonized with S. aureus; prevalence rates differ demographically. MRSA colonization prevalence, although low nationally in 2001-2002, may vary with demographic and organism characteristics.

Accuracy of antibiotyping using standard antibiograms compared with 16S–23S ribosomal spacer PCR for diagnosis of MRSA

Molecular methods for typing methicillin-resistant Staphylococcus aureus (MRSA) include PCR-based methods, pulsed-field gel electrophoresis (PFGE), spa typing, and multilocus sequence typing (MLST) [1, 2]. These techniques assist in targeted infection control efforts and are, moreover, indispensable for tracking genotypes on a large scale. Nevertheless, in vitro antimicrobial susceptibility patterns are still used in epidemiological investigations since antibiograms are rapidly delivered to infection control specialists without the need for additional investigations. The obvious disadvantage of antibiotyping, however, is the variability of resistance expression, which is also influenced by horizontal transmission and loss of extrachromosomal genetic elements. In addition, selective pressure tends to homogenize the antibiogram pattern over time. Some studies have revealed that by considering the diameters of growth inhibition, it is possible to more accurately type MRSA beyond the categorical classifications of susceptible and resistant [3]. However, the documentation and reporting of inhibition zone diameters is not a standard procedure in most hospitals. The aim of the study presented here was to assess the positive and negative predictive values and the sensitivity and specificity of antibiotyping MRSA as compared with 16S–23S ribosomal spacer PCR. The University Hospital Vienna is a 2,140-bed tertiarycare teaching hospital with an MRSA rate of 12.8% [4]. From January 2000 to December 2001, 268 patient-unique MRSA isolates were collected. The isolates were derived from the following sources: swabs of wounds and screening samples (n=132), respiratory tract (n=50), urine (n=42), intravascular catheter tips (n=17), blood (n=12), and miscellaneous other clinical materials (n=15). Staphylococcus aureus was cultured and identified according to standard procedures. Susceptibility testing for oxacillin was performed with oxacillin disks (1 μg) according to the guidelines of the Clinical and Laboratory Standards Institute (CLSI: formerly NCCLS) [5]. Strains identified as MRSA were confirmed by multiplex PCR amplification of the S. aureus-specific gene-fragment SA442 and fragments of the mecA and femB genes [6, 7]. Antimicrobial susceptibility testing with erythromycin, clindamycin, gentamicin, amikacin, ciprofloxacin, rifampicin, and trimethoprim was performed using the Kirby– Bauer disk diffusion method on Mueller–Hinton agar according to CLSI guidelines [5]. The compounds fosfomycin (120 μg disk) and fusidic acid (10 μg disk), which currently lack CLSI-defined breakpoints for susceptibility, were also included in the study, and the inhibition zones required for susceptibility were ≥10 mm for fosfomycin and ≥14 mm for fusidic acid. For further analysis, intermediate-susceptible and -resistant isolates were uniformly referred to as non-susceptible isolates. Glycopeptide antibiotics were not included in the analysis, because all of the isolates were susceptible to these compounds. F. Daxboeck (*) Clinical Institute for Hygiene and Medical Microbiology, Medical University Vienna, Kinderspitalgasse 15, 1090 Vienna, Austria e-mail: florian.daxboeck@meduniwien.ac.at Tel.: +43-1-404001902 Fax: +43-1-404001907

Survey of Methicillin-Resistant Staphylococcus aureus Strains from Two Hospitals in El Paso, Texas

Seventy-one percent of 76 methicillin-resistant Staphylococcus aureus (MRSA) strains isolated from two medical centers in El Paso, Texas, represent three similar pulsed-field gel electrophoresis types. Overall, six pulsed-field types were identified represented by multilocus sequence/staphylococcal chromosomal cassette DNA mec (SCCmec) types: ST5-MRSA-II; ST36-MRSA-II; ST8 (untypeable SCCmec); and a newly described clonal cluster 8 strain, ST507-MRSA-IV. This study demonstrates the presence of multiple-antibiotic-resistant epidemic MRSA clones in El Paso.

Necrotizing Fasciitis Caused by Community-Associated Methicillin-ResistantStaphylococcus aureusin Los Angeles

Necrotizing fasciitis is a life-threatening infection requiring urgent surgical and medical therapy. Staphylococcus aureus has been a very uncommon cause of necrotizing fasciitis, but we have recently noted an alarming number of these infections caused by community-associated methicillin-resistant S. aureus (MRSA). We reviewed the records of 843 patients whose wound cultures grew MRSA at our center from January 15, 2003, to April 15, 2004. Among this cohort, 14 were identified as patients presenting from the community with clinical and intraoperative findings of necrotizing fasciitis, necrotizing myositis, or both. The median age of the patients was 46 years (range, 28 to 68), and 71 percent were men. Coexisting conditions or risk factors included current or past injection-drug use (43 percent); previous MRSA infection, diabetes, and chronic hepatitis C (21 percent each); and cancer and human immunodeficiency virus infection or the acquired immunodeficiency syndrome (7 percent each). Four patients (29 percent) had no serious coexisting conditions or risk factors. All patients received combined medical and surgical therapy, and none died, but they had serious complications, including the need for reconstructive surgery and prolonged stay in the intensive care unit. Wound cultures were monomicrobial for MRSA in 86 percent, and 40 percent of patients (4 of 10) for whom blood cultures were obtained had positive results. All MRSA isolates were susceptible in vitro to clindamycin, trimethoprim-sulfamethoxazole, and rifampin. All recovered isolates belonged to the same genotype (multilocus sequence type ST8, pulsed-field type USA300, and staphylococcal cassette chromosome mec type IV [SCCmecIV]) and carried the Panton-Valentine leukocidin (pvl), lukD, and lukE genes, but no other toxin genes were detected. Necrotizing fasciitis caused by community-associated MRSA is an emerging clinical entity. In areas in which community-associated MRSA infection is endemic, empirical treatment of suspected necrotizing fasciitis should include antibiotics predictably active against this pathogen.

MRSA outbreak was controlled with daily hexachlorophene showers and hygiene education.

An outbreak of community-associated methicillin-resistant Staphylococcus aureus (MRSA) skin and soft tissue infection (SSTI) occurred in a college football team from August to September 2003. Eleven case-players were identified, and boils were the most common sign. Linemen had the highest attack rate (18%). Among 99 (93% of team) players with cultured specimens, 8 (8%) had positive MRSA nasal cultures. All available case-players' MRSA isolates characterized had the community-associated pulsed-field type USA300. A case-control study found that sharing bars of soap and having preexisting cuts or abrasions were associated with infection. A carrier-control study found that having a locker near a teammate with an SSTI, sharing towels, and living on campus were associated with nasal carriage. Successful outbreak control measures included daily hexachlorophene showers and hygiene education.

Genetic basis of resistance in Propionibacterium acnes strains isolated from diverse types of infection in different European countries

The purpose of the study was to characterize the resistance mechanism of 36 clindamycin (CL) and erythromycin (EM) resistant Propionibacterium acnes strains and 27 tetracycline (TET) resistant P. acnes isolates, collected from nine European countries, both from acne patients and from patients with different infections. PCR and sequencing of the genes encoding domain V of 23S rRNA for CL and EM resistant strains and 16S rRNA for TET resistant strains were performed. Pulsed-field gel electrophoresis was used as a typing method to establish the relationship between resistance genotypes and pulsed-field types. Several unique resistant genotypes were found to be distributed throughout Europe. P. acnes CL and EM resistant strains carrying one of the mutations within the 23S rRNA were predominantly isolated from Swedish acne patients (64%) compared to other infections (43%), OR=2.33 [CI=1.16–4.69]. Of 36 P. acnes isolates tested, none was found to carry the erm(X) resistance gene. Forty-four percent of TET resistant strains were found to carry a G–C transition in the 16S rRNA of the small ribosomal subunit and all these strains were isolated from Swedish acne patients. MIC of TET among all strains carrying this G–C mutation ( n = 12 ) was 32 mg/L and the MIC range for the strains where no mutation was detected ranged from 2 to 8 mg/L. The MIC values of TET were unaffected by the presence of reserpine, a well-known inhibitor of efflux pumps. Those TET resistant strains harbouring the mutation at 16S rRNA were clustered in one pulsotype. For TET resistant strains where no mutation was found, greater variability was noticed. No correlation was noticed between different resistance genotypes of CL and EM resistant strains and pulsed-field types.

A Clone of Methicillin-ResistantStaphylococcus aureusamong Professional Football Players

Methicillin-resistant Staphylococcus aureus (MRSA) is an emerging cause of infections outside of health care settings. We investigated an outbreak of abscesses due to MRSA among members of a professional football team and examined the transmission and microbiologic characteristics of the outbreak strain. We conducted a retrospective cohort study and nasal-swab survey of 84 St. Louis Rams football players and staff members. S. aureus recovered from wound, nasal, and environmental cultures was analyzed by means of pulsed-field gel electrophoresis (PFGE) and typing for resistance and toxin genes. MRSA from the team was compared with other community isolates and hospital isolates. During the 2003 football season, eight MRSA infections occurred among 5 of the 58 Rams players (9 percent); all of the infections developed at turf-abrasion sites. MRSA infection was significantly associated with the lineman or linebacker position and a higher body-mass index. No MRSA was found in nasal or environmental samples; however, methicillin-susceptible S. aureus was recovered from whirlpools and taping gel and from 35 of the 84 nasal swabs from players and staff members (42 percent). MRSA from a competing football team and from other community clusters and sporadic cases had PFGE patterns that were indistinguishable from those of the Rams' MRSA; all carried the gene for Panton-Valentine leukocidin and the gene complex for staphylococcal-cassette-chromosome mec type IVa resistance (clone USA300-0114). We describe a highly conserved, community-associated MRSA clone that caused abscesses among professional football players and that was indistinguishable from isolates from various other regions of the United States.