HA-MRSA Infections Research Articles

Comparison of Epidemiology of Patients Presented with Health Care Associated-Methicillin Resistant Staphylococcus aureus and Community Associated-Methicillin Resistant Staphylococcus aureus Infection attending at a Tertiary Care Hospital

Background: MRSA is an emerging pathogen worldwide and is usually detected in hospitals and other health care facilities. Objective: The purpose of the present study was to compare the epidemiology of patients presented with health care associated-methicillin resistant Staphylococcus aureus and community associated-methicillin resistant Staphylococcus aureus infection. Methodology: This study was designed as descriptive type of cross sectional type study. This study was carried out in the Department of Microbiology at Shaheed Suhrawardy Medical College, Dhaka, Bangladesh. The specimens were collected from indoor as well as OPD of Shaheed Suhrawardy Medical College & Hospital, Dhaka, Bangladesh. This study was conducted from January 2013 to June 2013 for a period of six (06) months. All patients at any age with both sexes presented with skin infection, soft tissue infection, urinary tract infection (UTI), burn wound, surgical site infection, orthopedic wound, puerperal sepsis as well as infection at anybody surface area who were attended at OPD as well as indoor department of hospital were selected as study population. The laboratory diagnosis was confirmed by microbiological test. Results: A total number of 290 patients presented with infections were enrolled for this study of which 145 patients were included in group A designated as CA-MRSA infection and the rest 145 patients were included in group B designated as HA-MRSA infection. Majority of the patients are in the 15 to 30 years’ age group in both group A and group B which were 80(55.2%) cases in each. However less than 15 years’ age group was the next most common in group A which is 22(15.2%) cases. The mean (±SD) age of group A and B was 30.43 (±16.131) and 29.43 (±15.648) years respectively. The difference of mean age between group A and B was not statistically significant (p=0.593). Low socio-economic condition patient was found in 63(43.4%) cases and 48(33.1%) cases in group A and B respectively. History of smoking was present in 29(20.0%) cases and 24(16.6%) cases in group A and B respectively. Urban dwellers were found in 50(34.5%) cases and 46(31.7%) cases in group A and B respectively. Conclusion: In conclusion history of smoking is found more common in group A than group B more urban dwellers in group A than group B. Bangladesh Journal of Medical Microbiology, January 2024;18(1):3-10

Methicillin resistant Staphylococcus aureus infections in children: A prospective study

Community acquired MRSA (CA MRSA) can cause invasive diseases posing a challenge to treating physicians. The knowledge about the disease load, clinical pattern, risk factors, outcome and susceptibility pattern in a given geo demographic context contribute crucially to the treatment outcome of MRSA infections in children. To study the profile, clinical pattern, factors affecting the immediate outcome and antimicrobial susceptibility of MRSA infections in children A prospective observational study was conducted in children between 2 months and 12 years admitted with MRSA infections, from January 2016 to December 2017 in the Institute of Maternal and Child Health, Government Medical College Kozhikode, Kerala state, India. Out of 431 children evaluated 83(19.3%) had MRSA infections with 44(53%) CA MRSA and 39(47%) hospital associated MRSA (HA MRSA). Twenty one (53.8%) of HA MRSA infections were hospital onset MRSA (HAHO MRSA) and 18(46.2%) community onset MRSA (HACO MRSA). There were 37 infants, 16 toddlers, 12 preschool children, 18 school children, 48 males and 35 females in the study population. Blood (50.6%), pus (33.7%), and body fluids (15.7%) were the sites of isolation. Skin and soft tissue infections (SSTI)(30.10%), pneumonia (28.90%), empyema (9.64%), meningitis (7.23%), septicaemia (12.05%), bone and joint infections (9.64%), peritonitis (2.41%) and septic shock (18.1%) were the clinical presentation. Mortality occurred in 9.9% and paediatric intensive care requirement in 45.8% patients. Anaemia and thrombocytopenia were identified as the risk factors for PICU admissions (corrected OR; 95% C I, 3.38; 1.02–11.18 and 8.35; 1.35–45.03 respectively). Thrombocytopenia was associated with mortality (corrected OR 43.74, 95% C I 3.86–495.9). Susceptibility to clindamycin, co-trimoxazole, amikacin and rifampicin were 79.5%, 73.5%, 68.7% and 90.4% respectively. MRSA constituted a significant proportion of bacterial infections in children, the majority being community onset. Pneumonia and empyema predominate over SSTI. Thrombocytopenia was associated with mortality and PICU admission. Clindamycin, co-trimoxazole and amikacin can be utilised in the treatment of less severe MRSA infections

Prevalence and clinical characteristics of methicillin-resistant Staphylococcus aureus infections among dermatology inpatients: A 7-year retrospective study at a tertiary care center in southwest China.

Increased rates of methicillin-resistant Staphylococcus aureus (MRSA) antibiotic resistance and the associated morbidity have increased dermatologists' attention to skin and soft tissue MRSA infections. However, the clinical characterization of MRSA skin and soft tissue infections (SSTIs) in Southwest China is lacking, which precludes optimal prevention and treatment of these infections. This study was conducted to characterize the prevalence, clinical comorbidities and antibiotic susceptibility of MRSA isolates from SSTIs, including community-associated (CA) and healthcare-associated (HA) isolates. In the Dermatology Inpatient Department of the First Affiliated Hospital of Guangxi Medical University, a retrospective study was conducted on data, including patient demographics and clinical information, from culture-confirmed S. aureus isolated from skin and soft tissue between January 1, 2015, and December 31, 2021. Isolate susceptibility to 13 antibiotics was determined using the Vitek 2 system. From among 864 S. aureus strains, we identified 283 MRSA (32.75%) isolates comprising 203 CA-MRSA and 80 HA-MRSA isolates. The average rate of CA-MRSA isolation for MRSA SSTIs was 71.73%. The HA-MRSA isolation rate for MRSA SSTIs increased significantly. HA-MRSA-infected patients were older. The most common dermatological presentation of CA-MRSA infection was staphylococcal scalded skin syndrome, while the comorbidity severe drug eruption was significantly associated with HA-MRSA infection. One CA-MRSA strain was resistant to linezolid, and one HA-MRSA strain had an intermediate phenotype for vancomycin; both strains had low sensitivity to clindamycin and erythromycin (3.70%~19.40%). However, HA-MRSA isolates were more susceptible to trimethoprim/sulfamethoxazole. CA-MRSA is a predominant pathogen causing SSTIs, and HA-MRSA infection incidence is increasing gradually. Both strains showed increasing antibiotic resistance. Our data on MRSA susceptibility may guide dermatologist antibiotic treatment decisions. Dermatologists should consider these identified comorbidities of MRSA SSTIs when patients are admitted and initiate early prevention and treatment of MRSA.

Community- and Health Care-Associated Methicillin-Resistant Staphylococcus aureus Infection in Tehran, Iran: Comparison of Drug Resistance and Virulence Determinants.

Methicillin-resistant Staphylococcus aureus (MRSA) can cause serious infections not only in hospitals but also in the community. The present study was aimed to characterize drug resistance and virulence determinants of community-associated (CA) MRSA isolate compared with healthcare-associated (HA) MRSA. A total of 44 patients with HA-MRSA and 11 patients with CA-MRSA infection (median age, 72 years) were included. The clinical isolates of MRSA were subjected to molecular analysis of virulence genes and drug susceptibility testing. Panton-Valentine leucocidin (PVL) exotoxin and toxic shock syndrome toxin (TSST) genes were disproportionately distributed between CA- and HA-isolates. PVL genes were more likely to be found among CA-isolates (36.4%) than HA-isolates (18.2). TSST genes were identified in only 2 CA-MRSA isolates tested (18.2%) compared with 9 HA-isolates (20.5%). Exfoliative toxin- b gene was negative in all isolates, however, one HA-isolate was positive for exfoliative toxin-a. mec-A gene was present in all clinical isolates. CA-isolates were more likely to be susceptible to trimethoprim-sulfamethoxazole and vancomycin compared with HA-isolates. Vancomycin-intermediate resistance was found in 2 HA-isolates. All clinical isolates were also resistant to clindamycin. CA- and HA- MRSA isolates are epidemiologically and microbiologically distinct. Thus, the strategies to prevent and treat these infections would be different. Patients with CA- and HA-MRSA infections should be treated effectively and receive follow-up evaluation to ensure the resolution of their infection. Surveillance studies should be conducted to determine the extent of CA- and HA-MRSA dissemination in Iran.

A descriptive analysis of PVL-positive multidrug-resistant Staphylococcus aureus in hospital-associated infections in Saudi Arabia.

Methicillin resistant Staphylococcus aureus infections impose a huge risk to public health in healthcare and community settings worldwide. Therefore, it is of interest to document data on the anti-biogramas and genotypes of isolates from Saudi Arabia. We assessed the antimicrobial susceptibility, determined spa (protein A gene) and analyzed multilocus MLST genotypes, and detected PVL gene in these isolates. We collected 28 clinical MRSA isolates, cultured and determined the minimum inhibitory concentrations of 17 antimicrobial agents using Vitek2 system (BioMerieux, USA) from 3 hospitals in Saudi Arabia during the year 2012. Polymorphic region of the spa and seven housekeeping genes were amplified and sequenced. BioNumerics v.5.1 (Applied Maths) was used for spa typing and MLST. Samples were screened for the presence of PVL and mecA genes using polymerase chain reaction (PCR). Analysis shows that all isolates were susceptible to chloramphenicol, rifampicin, nitrofurantoin, teicoplanin, daptomycin and vancomycin. The T4573/ST22 strains are found to be prevalent in the Saudi Arabia (N=6, 21%). We further noted that three isolates (t363/ST240 strain) were resistant to eight antimicrobial agents. Most of t4573/ST22 strains were PVL positive, resistant to ciprofloxacin and linked to HA-MRSA infections. We document data for the presence of emerging multi drug resistant S. aureus strains carrying the PVL gene circulating within hospitals. This highlights the urgent need for continuous active surveillance and implementation of prevention measures.

Healthcare-associated (HA) and community-associated (CA) methicillin resistant Staphylococcus aureus (MRSA) in Bangladesh – Source, diagnosis and treatment

Methicillin-resistant Staphylococcus aureus (MRSA) has long been a common pathogen in healthcare facilities, but now, it has emerged as a problematic pathogen in the community setting as well. This study reported source, diagnosis and treatment of HA-MRSA and CA-MRSA.A total of sixty-five clinical samples (urine, pus, wound swab) were collected from clinical origin of Dhaka city, Bangladesh. All the isolates were tested phenotypically by conventional methods and genotypically by PCR targeting nuc, pvl and mecA genes. Finally sequencing was carried out for pvl gene to know the mutagenic variation or any amino acid changes in pvl gene. Chi square test was employed for statistical analysis. Patients of age group 51–60 years are more susceptible (46.15%) to MRSA, CA-MRSA or HA-MRSA infection. Female are (32.30%) more susceptible to MRSA infection. Among 65 isolates 53 isolates identified phenotypically as S. aureus. These were positive for amplification of nuc (270 bp) gene of S. aureus. Moreover, among 53 isolates 33 phenotypically considered as MRSA and 38 (72%) showed positive amplification for mecA (162 bp) gene. Among 38 MRSA isolates 22 (57.89%) confirmed as CA-MRSA and 16 (42.10%) as HA-MRSA. Finally, sequence analysis for lukS/F-PV genes from 4 representative isolates detected a new single nucleotide polymorphism in comparison with the control sequence. However, no amino acid changes were found. Statistical analysis showed HA-MRSA isolates were more commonly found in urine sample and CA-MRSA in pus and wound swab. CA-MRSA isolates were more resistant to tested antibiotics than HA-MRSA.

Hospital-associated methicillin-resistant Staphylococcus aureus: A cross-sectional analysis of risk factors in South African tertiary public hospitals.

IntroductionHospital-associated methicillin-resistant S. aureus (HA-MRSA) remains a significant cause of morbidity and mortality worldwide. We conducted a study to determine risk factors for HA-MRSA in order to inform control strategies in South Africa.MethodsWe used surveillance data collected from five tertiary hospitals in Gauteng and Western Cape provinces during 2014 for analysis. A case of HA-MRSA was defined as isolation of MRSA from a blood culture 48 hours after admission and/or if the patient was hospitalised in the six months prior to the current culture. Multivariable logistic regression modelling was used to determine risk factors for HA-MRSA.ResultsOf the 9971 patients with positive blood cultures, 7.7% (772) had S. aureus bacteraemia (SAB). The overall prevalence of MRSA among those with SAB was 30.9% (231/747; 95% confidence interval [CI] 27.6%– 34.3%). HA-MRSA infections accounted for 28.3% of patients with SAB (207/731; 95% CI 25.1%– 31.7%). Burns (adjusted odds ratio [aOR] 12.7; 95% CI 4.7–34.4), age ≤1 month (aOR 8.7; 95% CI 3.0–24.6), residency at a long-term care facility (aOR 5.2; 95% CI, 1.5–17.4), antibiotic use within two months of the current SAB episode (aOR 5.1; 95% CI 2.8–9.1), hospital stay of 13 days or more (aOR 2.8; 95% CI 1.3–5.6) and mechanical ventilation (aOR 2.2; 95% CI 1.07–4.6), were independent risk factors for HA-MRSA infection.ConclusionThe prevalence of MRSA remains high in South African tertiary public hospitals. Several identified risk factors of HA-MRSA infections should be considered when instituting infection and prevention strategies in public-sector hospitals, including intensifying the implementation of antimicrobial stewardship programmes. There is an urgent need to strengthen infection prevention and control in burn wards, neonatal wards, and intensive care units which house mechanically ventilated patients.

A small proportion of community-associated methicillin-resistant Staphylococcus aureus bacteraemia, compared to healthcare-associated cases, in two South African provinces.

We compared the proportion of cases of community-associated and healthcare-associated methicillin-resistant Staphylococcus aureus (CA-MRSA and HA-MRSA, respectively) bacteraemia among patients at five hospitals in the Gauteng and Western Cape provinces in South Africa and described the molecular characteristics and antimicrobial susceptibility trends. This was a cross-sectional study using data collected by enhanced surveillance for S. aureus bacteraemia. A total of 2511 cases of S. aureus bacteraemia were identified from January 2013 to January 2016. Among 1914 cases of S. aureus, 557 (29.1%) cases were identified as MRSA infection. Forty-four cases (44/1914 [2.3%] of all S. aureus cases) were considered CA-MRSA infection and 513/1914 (26.8% of all cases) had HA-MRSA infection; the majority were neonates. CA-MRSA constituted 7.9% (44/557) of all cases of MRSA infection. Staphylococcus aureus isolates demonstrated significantly reduced susceptibility to the following classes of antimicrobial agents: macrolides, tetracyclines, aminoglycosides and cotrimoxazole, in 2015 compared to 2013 (p<0.05). Of the 557 MRSA isolates, 484 (87%) were typed for SCCmec elements and spa types: the most common SCCmec type was type III (n=236, 48.76%), followed by type IV (n=144, 29.76%). The most common spa types were t037 (n=229, 47.31%) and t1257 (n=90, 18.60%). Of 28 isolates selected for multilocus sequence typing (MLST), the most common sequence types (STs) were ST239 and ST612 of clonal complex 8 (CC8) (n=8 each) and a novel ST (ST4121) was obtained for one isolate. This study demonstrates that S. aureus bacteraemia is common in South African academic centres and characterised by HA-MRSA SCCmec types III and IV. A small proportion of CA-MRSA cases were caused by a few different sequence types.

Emergence of Community-Genotype Methicillin-Resistant Staphylococcus aureus in Korean Hospitals: Clinical Characteristics of Nosocomial Infections by Community-Genotype Strain.

BackgroundAs community-genotype methicillin-resistant Staphylococcus aureus (MRSA) strains spread into hospitals, the genotypes of the MRSA strains causing hospital-acquired (HA) infections have become more diverse. We describe clinical characteristics of nosocomial MRSA infections by a community-genotype of sequence type (ST) 72.Materials and MethodsA case-control study was designed among patients with HA-MRSA infections. Forty patients with infections caused by ST72-MRSA SCCmec type IV were selected as cases. Cases were matched to the controls with 106 patients infected with ST5/ST239 MRSA, which are representative hospital genotypes in Korea.ResultsPatients infected with ST72 isolates were younger than those with ST5/ST239 isolates. Female gender predominated among ST72 MRSA group compared to ST5/ST239 MRSA group. Solid tumor was a more frequent underlying disease in MRSA infections by ST72 isolates, whereas underlying renal, lung, heart, and neurologic diseases were more frequently found in those by ST5/ST239 isolates. The most common type of infection was pneumonia in both ST72 and ST5/ST239 groups (45.0% vs. 51.9%), followed by skin and soft tissue infection (SSTI). Female gender and underlying solid tumor were identified to be independent predictors for MRSA infections by ST72 isolates. All-cause mortality rates (20.0% vs. 30.2%) were not different between the groups.ConclusionA community-genotype MRSA, ST72 isolate has emerged as a nosocomial pathogen presenting as hospital-acquired pneumonia and SSTI. Although differences in underlying disorders were found, the distribution of infection type and mortality rate did not differ between the groups.

Clinical characteristics, virulence factors and molecular typing of methicillin-resistant Staphylococcus aureus infections in Shenzhen City, China.

Methicillin-resistant Staphylococcus aureus (MRSA) has emerged as a serious hospital and community-acquired infection and some strains are associated with greater severity. We investigated the clinical variability and molecular characteristics of MRSA infections in Shenzhen, China through a study at nine sentinel hospitals from January to December 2014. MRSA infections were classified as community-associated (CA-MRSA), healthcare-associated (HA-MRSA), and healthcare-associated community-onset (HACO-MRSA). In total, 812 MRSA isolates were collected and 183 of these were selected for further study. Patients with HA-MRSA infections were generally of greater age compared to other groups. Distinct body site and clinical presentations were evident in infected patients, e.g. CA-MRSA (skin and soft tissue, 53%), HA-MRSA (respiratory tract, 22%; surgical site, 20%; trauma wounds, 20%) and HACO-MRSA (mastitis, 47%). In contrast to HA-MRSA, other categories of strains were significantly more susceptible to gentamicin, sulfamethoxazole/trimethoprim, and tetracycline. No resistance to vancomycin or linezolid was recorded. The predominant clonal lineage within each strain category was CC59-t437-SCCmec IV/V-agr I (CA, 51·4%; HA, 28·9%; HACO, 52·9%) which exhibited characteristics of a traditional CA clone together with agr I which is more often associated with HA clones. In conclusion, for the three categories of MRSA infections, there were significant differences in clinical characteristics of patients, but the predominant clone in each category shared a similar genetic background which suggests that transmission of MRSA strains has occurred between the community and hospitals in Shenzhen.

Methicillin-Resistant Staphylococcus aureus Ocular Infection in Taiwan: Clinical Features, Genotying, and Antibiotic Susceptibility.

Methicillin-resistant Staphylococcus aureus (MRSA) infection is an important public health issue. This observational study aimed to characterize clinical features, antibiotic susceptibility, and genotypes of ocular infections caused by MRSA based on the clinical and molecular definitions of community-associated (CA) and healthcare-associated (HA) strains.Fifty-nine patients with culture-proven S aureus ocular infection were enrolled from January 1, 2010 to December 31, 2011 at Chang Gung Memorial Hospital, Taiwan. Antibiotic susceptibility was verified using disk diffusion/E test. For characterization, staphylococcal cassette chromosome mec (SCCmec), pulsed-field gel electrophoresis (PFGE), multilocus sequence type (MLST), and Panton–Valentine leukocidin (PVL) gene, were performed. MRSA isolates from the patients with HA factors were classified as clinically defined HA-MRSA, and those carrying SCCmec type I to III as molecularly defined HA-MRSA.Thirty-four patients with MRSA ocular infection were identified. The most common clone of CA-MRSA and HA-MRSA isolates was ST59/PFGE type D/SCCmec IV,VT/PVL (+) (n = 12) and CC 239/PFGE type A/SCCmec III, IIIA/PVL(−) (n = 10), respectively. All the 11 patients with molecularly defined HA-MRSA infections and 50% of the 22 patients with molecularly defined CA-MRSA infections were found to have HA factors (P = .005). CA-MRSA tended to cause lid infections, whereas HA-MRSA tended to cause corneal infections. Contrary to HA-MRSA isolates, nearly all the CA-MRSA isolates were susceptible to trimethoprim/sulfamethoxazole and fluoroquinolones under either clinical or molecular classifications.In Taiwan, CA-MRSA isolates exhibited considerably higher susceptibility to fluoroquinolones when compared with HA-MRSA isolates. A strong correlation was observed between the HA factors and molecularly defined HA-MRSA isolates.

Substantial shifts in ranking of California hospitals by hospital-associated methicillin-resistant Staphylococcus aureus infection following adjustment for hospital characteristics and case mix.

States have established public reporting of hospital-associated (HA) infections-including those of methicillin-resistant Staphylococcus aureus (MRSA)-but do not account for hospital case mix or postdischarge events. Identify facility-level characteristics associated with HA-MRSA infection admissions and create adjusted hospital rankings. A retrospective cohort study of 2009-2010 California acute care hospitals. We defined HA-MRSA admissions as involving MRSA pneumonia or septicemia events arising during hospitalization or within 30 days after discharge. We used mandatory hospitalization and US Census data sets to generate hospital population characteristics by summarizing across admissions. Facility-level factors associated with hospitals' proportions of HA-MRSA infection admissions were identified using generalized linear models. Using state methodology, hospitals were categorized into 3 tiers of HA-MRSA infection prevention performance, using raw and adjusted values. Among 323 hospitals, a median of 16 HA-MRSA infections (range, 0-102) per 10,000 admissions was found. Hospitals serving a greater proportion of patients who had serious comorbidities, were from low-education zip codes, and were discharged to locations other than home were associated with higher HA-MRSA infection risk. Total concordance between all raw and adjusted hospital rankings was 0.45 (95% confidence interval, 0.40-0.51). Among 53 community hospitals in the poor-performance category, more than 20% moved into the average-performance category after adjustment. Similarly, among 71 hospitals in the superior-performance category, half moved into the average-performance category after adjustment. When adjusting for nonmodifiable facility characteristics and case mix, hospital rankings based on HA-MRSA infections substantially changed. Quality indicators for hospitals require adequate adjustment for patient population characteristics for valid interhospital performance comparisons.

Replacement of HA-MRSA by CA-MRSA infections at an academic medical center in the midwestern United States, 2004-5 to 2008.

We noted anecdotally that infections designated as health care-associated (HA-) MRSA by epidemiologic criteria seemed to be decreasing in incidence at the University of Chicago Medical Center (UCMC) after 2004. We compared MRSA patients seen at any site of clinical care at UCMC and the isolates that caused their infections in 2004-5 (n = 545) with those in 2008 (n = 135). The percent of patients with MRSA infections cultured > 2 days after hospital admission decreased from 19.5% in 2004-5 to 7.4% in 2008 (p = 0.001). The percent in 2004-5 compared with 2008 who had a hospitalization (49.1% to 26.7%, p = 0.001) or surgery (43.0% to 14.1%, p<0.001) in the previous year decreased. In 2008 a greater percent of patients was seen in the emergency department (23.1% vs. 39.3%) and a smaller percent both in intensive care units (15.6% vs. 6.7%) and in other inpatient units (40.7% vs. 32.6%) (p<0.001). The percent of patients with CA-MRSA infections by the CDC epidemiologic criteria increased from 36.5% in 2004-5 to 62.2% in 2008 (p<0.001). The percent of MRSA isolates sharing genetic characteristics of USA100 decreased from 27.9% (152/545) to 12.6% (17/135), while the percent with CA-MRSA (USA300) characteristics increased from 53.2% (290/545) to 66.7% (90/135). The percent of infections that were invasive did not change significantly. Our data suggest that HA-MRSA infections, both by epidemiologic and microbiologic criteria, relative to CA-MRSA, decreased between 2004-5 and 2008 at UCMC.

Molecular epidemiology and characterization of virulence genes of community-acquired and hospital-acquired methicillin-resistant Staphylococcus aureus isolates in Colombia

To determine the molecular epidemiology and presence of virulence genes in community-acquired (CA) and hospital-acquired (HA) methicillin-resistant Staphylococcus aureus (MRSA) isolates and their relationship to clinical outcomes. An observational and prospective study of infections caused by MRSA was conducted between June 2006 and December 2007 across seven hospitals in three Colombian cities. MRSA isolates were analyzed for SCCmec. Also, pulsed-field gel electrophoresis and multilocus sequence typing were performed and 25 virulence genes were identified. Two hundred and seventy isolates were collected from 262 adult hospital patients with MRSA infections. Overall, 68% of the isolates were classified as HA-MRSA and 32% as CA-MRSA. We identified differences in the patterns of virulence genes: 85% of HA-MRSA isolates possessed the enterotoxin gene cluster (egc), whereas 92% of CA-MRSA isolates possessed the lukF-PV/lukS-PV genes. Multivariate analysis showed an increased risk of mortality for seg (p=0.001, odds ratio 4.73) and a protective effect for eta (p=0.018, odds ratio 0.33). Our study confirms that three clones of MRSA predominantly circulate in Colombia: a Chilean clone, a pediatric clone that causes HA-MRSA infections, and a USA300-related clone (SCCmec IVc) in CA-MRSA infections, which differ in the content of clinically important virulence genes. This study confirms that PVL is not a determinant of severity or mortality in CA-MRSA infections.

Shift in dominant hospital-associated methicillin-resistant Staphylococcus aureus (HA-MRSA) clones over time

The majority of HA-MRSA infections are caused by endogenous infection and by only a small number of clones. The reasons for the success of some clones over others are unknown. We investigated the evolution of an MRSA population from a large, acute-care teaching hospital in London, UK over a 10 year period. MRSA incidence and antibiotic prescribing were correlated with changes in resistance genes and prevalence of clonal groups. Three clones caused the majority of infections, CC30 SCCmecII (EMRSA-16), CC22 SCCmecIV (EMRSA-15) and ST239 SCCmecIII. Clones that were multidrug resistant were selected for, and CC22 became dominant once it acquired a wide range of extra resistance genes. CC22 MRSA was also the fittest clone in an independent growth assayand a competition assay, and had a greater ability to survive desiccation. No individual isolate was fully drug resistant, and there was evidence of substantial horizontal gene transfer (HGT) as well as resistance gene loss within the clonal groups. The exception was fluoroquinolone resistance, which was rarely lost by any of the dominant hospital clones, suggesting that this resistance contributes to selection and survival of HA-MRSA. In support of this, a decrease in hospital-wide ciprofloxacin (a fluoroquinolone) prescribing was strongly associated with an overall decrease in MRSA infection. Our data suggest successful HA-MRSA clones such as CC22 SCCmecIV are resistant to fluoroquinolones as well as fitter and able to acquire, but not necessarily accumulate, resistance to a wide range of additional antibiotics.

Retrospective study of necrotizing fasciitis and characterization of its associated Methicillin-resistant Staphylococcus aureusin Taiwan

BackgroundMethicillin-resistant Staphylococcus aureus (MRSA) has emerged as a prevalent pathogen of necrotizing fasciitis (NF) in Taiwan. A four-year NF cases and clinical and genetic differences between hospital acquired (HA)- and community-acquired (CA)-MRSA infection and isolates were investigated.MethodsA retrospective study of 247 NF cases in 2004-2008 and antimicrobial susceptibilities, staphylococcal chromosomal cassette mec (SCCmec) types, pulsed field gel electrophoresis (PFGE) patterns, virulence factors, and multilocus sequence typing (MLST) of 16 NF-associated MRSA in 2008 were also evaluated.ResultsIn 247 cases, 42 microbial species were identified. S. aureus was the major prevalent pathogen and MRSA accounted for 19.8% of NF cases. Most patients had many coexisting medical conditions, including diabetes mellitus, followed by hypertension, chronic azotemia and chronic hepatic disease in order of decreasing prevalence. Patients with MRSA infection tended to have more severe clinical outcomes in terms of amputation rate (p < 0.05) and reconstruction rate (p = 0.001) than those with methicillin-sensitive S. aureus or non-S. aureus infection. NF patients infected by HA-MRSA had a significantly higher amputation rate, comorbidity, C-reactive protein level, and involvement of lower extremity than those infected by CA-MRSA. In addition to over 90% of MRSA resistant to erythromycin and clindamycin, HA-MRSA was more resistant than CA-MRSA to trimethoprim-sulfamethoxazole (45.8% vs. 4%). ST59/pulsotype C/SCCmec IV and ST239/pulsotype A/SCCmec III isolates were the most prevalent CA- and HA-MRSA, respectively in 16 isolates obtained in 2008. In contrast to the gene for γ-hemolysin found in all MRSA, the gene for Panton-Valentine leukocidin was only identified in ST59 MRSA isolates. Other three virulence factors TSST-1, ETA, and ETB were occasionally identified in MRSA isolates tested.ConclusionNF patients with MRSA infection, especially HA-MRSA infection, had more severe clinical outcomes than those infected by other microbial. The prevalent NF-associated MRSA clones in Taiwan differed distinctly from the most predominant NF-associated USA300 CA-MRSA clone in the USA. Initial empiric antimicrobials with a broad coverage for MRSA should be considered in the treatment of NF patients in an endemic area.

Risk factors associated with the conversion of meticillin-resistant Staphylococcus aureus colonisation to healthcare-associated infection

The objective of the study was to identify risk factors for healthcare-associated meticillin-resistant Staphylococcus aureus (HA-MRSA) infections in patients with MRSA colonisation over an extended time period. This was a case-control study conducted at a community teaching hospital. Patients included 41 cases and 82 controls, aged ≥18 years, who were nares colonisation culture positive for MRSA and either did or did not develop an HA-MRSA infection within 60 days after index colonisation, respectively. Potential risk factors evaluated included: patient demographics, comorbid conditions, medication use, presence of invasive devices, presence of wounds or other infections, nutritional status, number of hospitalisations and time to infection development. In the univariate analysis, the presence of peripheral vascular disease, three or more comorbidities, a central venous catheter, a Foley catheter, or two or more hospitalisations were significantly associated with increased risk for HA-MRSA infection. Multivariate analysis yielded a model that included presence of a central venous catheter (OR: 8.00; 95% CI: 3.13-20.4) or two or more hospitalisations (OR: 3.37; 95% CI: 1.37-8.26) as independent risk factors for MRSA infection in those with MRSA colonisation. In conclusion, risk factors independently associated with the conversion of MRSA colonisation to HA-MRSA infection include the presence of a central venous catheter or two or more hospitalisations. Strategies involving risk factor minimisation may be helpful in reducing HA-MRSA infections in this patient population.

Seasonality of MRSA Infections

Using MRSA isolates submitted to our hospital microbiology laboratory January 2001–March 2010 and the number of our emergency department (ED) visits, quarterly community-associated (CA) and hospital-associated (HA) MRSA infections were modeled using Poisson regressions. For pediatric patients, approximately 1.85x (95% CI 1.45x–2.36x, adj. p<0.0001) as many CA-MRSA infections per ED visit occurred in the second two quarters as occurred in the first two quarters. For adult patients, 1.14x (95% CI 1.01x–1.29x, adj.p = 0.03) as many infections per ED visit occurred in the second two quarters as in the first two quarters. Approximately 2.94x (95% CI 1.39x–6.21x, adj.p = 0.015) as many HA-MRSA infections per hospital admission occurred in the second two quarters as occurred in the first two quarters for pediatric patients. No seasonal variation was observed among adult HA-MRSA infections per hospital admission. We demonstrated seasonality of MRSA infections and provide a summary table of similar observations in other studies.

Spread of methicillin-resistant Staphylococcus aureus between the community and the hospitals in Asian countries: an ANSORP study

Methicillin-resistant Staphylococcus aureus (MRSA) is highly prevalent in hospitals in many Asian countries. Recent emergence of community-associated (CA) MRSA worldwide has added another serious concern to the epidemiology of S. aureus infections. To understand the changing epidemiology of S. aureus infections in Asian countries, we performed a prospective, multinational surveillance study with molecular typing analysis. We evaluated the prevalence of methicillin resistance in S. aureus isolates in CA and healthcare-associated (HA) infections, and performed molecular characterization and antimicrobial susceptibility tests of MRSA isolates. MRSA accounted for 25.5% of CA S. aureus infections and 67.4% of HA infections. Predominant clones of CA-MRSA isolates were ST59-MRSA-SCCmec type IV-spa type t437, ST30-MRSA-SCCmec type IV-spa type t019 and ST72-MRSA-SCCmec type IV-spa type t324. Previously established nosocomial MRSA strains including sequence type (ST) 239 and ST5 clones were found among CA-MRSA isolates from patients without any risk factors for HA-MRSA infection. CA-MRSA clones such as ST59, ST30 and ST72 were also isolated from patients with HA infections. Our findings confirmed that MRSA infections in the community have been increasing in Asian countries. Data also suggest that various MRSA clones have spread between the community and hospitals as well as between countries.

Dissemination of Community-Associated Methicillin-Resistant Staphylococcus aureus in a Tertiary Care Hospital

The epidemiology of methicillin-resistant Staphylococcus aureus (MRSA) was investigated at a tertiary care hospital, and relationship was made between the clinical and genetic definitions of community- and healthcare-associated MRSA. Nonduplicate isolates of S. aureus were collected during 2004. Isolates were classified clinically as community-associated (CA) or healthcare-associated (HA). Molecular typing studies were performed on the isolates. Four hundred and two S. aureus isolates were collected, of which 281 (70%) were MRSA. By clinical definition, 58 (21%) were classified as CA-MRSA and 215 (77%) as HA-MRSA. Among CA-MRSA, 36 (62%) harbored a SCCmec type IV gene. None of the SCCmec type IV CA-MRSA expressed inducible clindamycin resistance (MLSBi). Among 57 HA-MRSA isolates, 31 (54.4%) harbored a SCCmec type IV gene; MLSBi present in 5 (16%). Type IV SCCmec MRSA were most often associated with skin and soft tissue infections (RR 3.34 95% CI 1.43, 7.8). USA300 was the most common genotype among both CA- and HA-MRSA. Community-associated MRSA is a prominent pathogen with its most common genotype, USA300, representing a significant proportion of CA- and HA-MRSA infections in our institution. Clinical definitions of CA- and HA- status do not correlate well with the genetic definitions, particularly for HA-MRSA.