Clinical features and genotyping analysis of community-acquired methicillin-resistant Staphylococcus aureus infections in Taiwanese children

Bacteremic necrotizing mediastinitis caused by community-associated clonal complex 398 methicillin-resistant Staphylococcus aureus in a baby aged 4 months

Invasive community-associated methicillin-resistant Staphylococcus aureus (MRSA) diseases caused by clonal complex 398 MRSA without animal contact have become a new emerging threat. We report a case of bacteremic mediastinitis caused by a Panton-Valentine leukocidin-positive community-associated sequence type 1232 MRSA in a Taiwanese baby aged 4 months without animal contact.

Is the Oral Cavity of Intensive Care Unit Pediatric Patients More Susceptible to Methicillin-Resistant Staphylococcus aureus Infection?

Objective: The aim of this study was to assess the prevalence of methicillin-resistant Staphylococcus aureus (MRSA) in the oral cavity of pediatric patients hospitalized at an intensive care unit (ICU). Methodology: Thirty ICU patients (group 1) and 30 healthy patients (group 2), between 1 and 12 years of age, matched by sex and age, were selected from a public hospital in Brazil. After oral examinations, biological specimens (nostril swab, oral mucosa, and supragingival biofilm) were collected from both groups to verify the presence of Staphylococcus aureus. Identification occurred after growth in Tryptic Soy Broth with 7.5% of NaCl for 48 hours, growth in Mannitol Salt Agar, gram staining, catalase, and coagulase tests. S. aureus isolates were submitted to antibiotic sensitivity test. Results: Only 36.7% of patients in the ICU perform oral hygiene during the hospitalization period and 41.7% presented high level of dental biofilm accumulation. The presence of S. aureus was similar in patients from group 1 (43.3%, 13) and group 2 (50.0%, 15) (p = 0.60). Both groups presented 18 samples each that tested positive for S. aureus. However, when considering patients infected by MRSA, the prevalence was higher in group 1 (eight; 26.7%) than in group 2 (five; 16.7%) but no statistical difference was observed (p = 0.53). In group 1, nine MRSA samples were resistant to erythromycin and seven to clindamycin. In group 2, two MRSA samples were resistant to erythromycin and two to clindamycin. Conclusions: Although ICU children did not show a significant higher carriage of MRSA when compared with the healthy group in the population studied, the number of highly resistant strains in the oral cavity isolated from ICU patients adds an important risk factor to be considered by the medical team as possible source of systemic infections, extended hospital stay, and poor outcomes.

Nasal Methicillin-Resistant Staphylococcus aureus Colonization in Patients with Type 1 Diabetes in Taiwan

Nasal methicillin-resistant Staphylococcus aureus (MRSA) colonies are an essential reservoir of infection, especially for patients with diabetes. However, data on MRSA colonization in patients with type 1 diabetes are limited. We investigated the epidemiology of MRSA colonization in patients with type 1 diabetes. This prospective cross-sectional study was conducted in a medical center (Chang Gung Memorial Hospital) in Taiwan from 1 July to 31 December 2020. Nasal sampling and MRSA detection were performed. The molecular characteristics of MRSA isolates were tested, and factors associated with MRSA colonization were analyzed. We included 245 patients with type 1 diabetes; nasal MRSA colonization was identified in 13 (5.3%) patients. All isolates belonged to community-associated MRSA genetic strains; the most frequent strain was clonal complex 45 (53.8%), followed by ST59 (30.8%) (a local community strain). MRSA colonization was positively associated with age ≤ 10 years, body mass index < 18 kg/m², and diabetes duration < 10 years; moreover, it was negatively associated with serum low-density lipoprotein cholesterol ≥ 100 mg/dL. No independent factor was reported. The nasal MRSA colonization rate in type 1 diabetes is approximately 5% in Taiwan. Most of these colonizing strains are community strains, namely clonal complex 45 and ST59.

First Case of Staphylococci Carrying Linezolid Resistance Genes from Laryngological Infections in Poland

Linezolid is currently used to treat infections caused by multidrug-resistant Gram-positive cocci. Both linezolid-resistant S. aureus (LRSA) and coagulase-negative staphylococci (CoNS) strains have been collected worldwide. Two isolates carrying linezolid resistance genes were recovered from laryngological patients and characterized by determining their antimicrobial resistance patterns and using molecular methods such as spa typing, MLST, SCCmec typing, detection of virulence genes and ica operon expression, and analysis of antimicrobial resistance determinants. Both isolates were multidrug resistant, including resistance to methicillin. The S. aureus strain was identified as ST-398/t4474/SCCmec IVe, harboring adhesin, hemolysin genes, and the ica operon. The S. haemolyticus strain was identified as ST-42/mecA-positive and harbored hemolysin genes. Linezolid resistance in S. aureus strain was associated with the mutations in the ribosomal proteins L3 and L4, and in S. haemolyticus, resistance was associated with the presence of cfr gene. Moreover, S. aureus strain harbored optrA and poxtA genes. We identified the first case of staphylococci carrying linezolid resistance genes from patients with chronic sinusitis in Poland. Since both S. aureus and CoNS are the most common etiological factors in laryngological infections, monitoring of such infections combined with surveillance and infection prevention programs is important to decrease the number of linezolid-resistant staphylococcal strains.

Microbiological Monitoring in the System of Epidemiological Surveillance of Purulent-Septic Infections in a Multidisciplinary Hospital

The purpose of the research was to study epidemiological manifestations and etiological structure of sepsis in a multidisciplinary hospital for children.Materials and methods. An analysis of cases of 85 patients with a diagnosis of sepsis hospitalized in a multidisciplinary hospital at the regional level (Irkutsk) for the period 2013–2018 was carried out.Results and discussion. The most affected age groups are children under one year old (23.5 %) and from one year to two years (29.4 %). During the study period, 572 bacterial and fungal cultures, represented by 19 types of microorganisms, playing a leading role in the formation of the microbial ecology of the hospital, were isolated from patients with GPSI. In the structure of the GPSI microflora, gram-negative microorganisms are found in 49.8 % of cases, grampositive microbiota – in 30.1 %, fungi account for one fifth of all positive findings. A. baumannii and P. aeruginosa were sown more often from blood, sputum and abdominal cavity, and S. aureus and A. baumannii were the most frequent pathogens from wounds. The largest number of enterococci is isolated from urine.Conclusions. The etiological factor in the development of nosocomial GPSI in most cases is gram-negative microorganisms – A. baumanii (39.9 %), P. aeruginosa (20.7 %), K. pneumoniae (23.1 %). At the same time, in recent years, fungi have become increasingly important in the etiology of septic conditions.

Vascular access infection by Staphylococcus aureus from removed dialysis accesses

Hemodialysis patients are particularly vulnerable to Staphylococcus aureus infection, with the vascular access serving as the site of entry for this formidable pathogen. Patients with arteriovenous grafts (AVGs) and tunneled‐cuffed catheters (TCCs) are at elevated risk of S. aureus infection. In this study, we investigated the correlation between the clinical characteristics of S. aureus vascular access infection (VAI), molecular profiles, and the biofilm formation abilities of clinical isolates of S. aureus. We collected samples of methicillin‐resistant S. aureus (MRSA), methicillin‐sensitive S. aureus (MSSA), and methicillin‐sensitive S. argenteus (MSSAg) from patients with S. aureus VAI and patients with other infections. The molecular profiles of the clinical isolates were determined using disk diffusion testing and molecular typing. The biofilm formation ability was determined by microtiter plate assay. In total, 63 S. aureus and 10 S. argenteus isolates were identified: 40 MRSA, 23 MSSA, and ten MSSAg. MRSA was highly prevalent (77.8%) in TCC isolates and was multidrug resistant. Of the 40 MRSA isolates, ST239‐SCCmec III was the predominant clone. SCCmec type IV was the predominant type (35%) in isolates from AVGs, while SCCmec type III was prevalent in TCC infection and showed significantly higher biofilm formation ability than types IV and V. In dialysis VAI by S. aureus, patients with TCC were more often infected with MRSA than patients with AVG, and MRSA in TCC–VAI was predominantly SCCmec type III, which had the strongest drug resistance and biofilm formation ability.

Nasal methicillin-resistant Staphylococcus aureus colonization among otherwise healthy children aged between 2 months and 5 years in northern Taiwan, 2005-2010

BACKGROUND

Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) infections have been increasingly reported worldwide and are associated with nasal colonization. In Taiwan, available data disclosed a similar trend. We conducted a study for the updated childhood nasal MRSA carriage.

METHODS

From July 2005 to December 2010, children aged between 2 months and 5 years who presented for a well-child health care visit to a medical center or from kindergarten/daycare center were invited and a nasal swab specimen was obtained for the detection of MRSA. All MRSA isolates were characterized.

RESULTS

A total of 3226 children were included and the rate of nasal MRSA carriage was 10.2%. Children aged 2-6 months and >3 years were significantly associated with MRSA carriage, while pneumococcus colonization (p = 0.033) and breastfeeding (p = 0.025) were negatively associated with MRSA carriage. Of the 330 MRSA isolates, a total of 13 pulsotypes with two major patterns (type C, 47.0% and D, 29%) were identified. Most MRSA isolates belonged to two major clones, characterized as sequence type 59 (ST59)/pulsotype C/staphylococcal cassette chromosome (SCCmec) IV/Panton-Valentine leukocidin (PVL)-negative (45.8%) and ST59/pulsotype D/SCCmec V_T/PVL-positive (22.7%). Two new clones as ST 508/SCCmec IV (9.7%) and ST573/SCCmec IV (7.3%) emerged and increased markedly since 2007.

CONCLUSION

Between 2005 and 2010, 10.2% of healthy children in northern Taiwan carried MRSA in anterior nares, with the highest carriage rate for infants aged 2-6 months. Two emerging clones, ST 508 and ST 573, were identified and the clinical significance needs further surveillance.

Prevalence of and risk factors for nasal methicillin-resistant Staphylococcus aureus colonization among children in central Taiwan

BACKGROUND/PURPOSE

Staphylococcus aureus (S. aureus) causes diseases ranging from mild skin infections to invasive diseases. Carriage of S. aureus, including methicillin-resistant S. aureus (MRSA), is a significant risk factor for subsequent staphylococcal infection. Several studies discussed MRSA colonization in Taiwan, but mostly in northern Taiwan. This is the first study that estimates the prevalence of MRSA nasal colonization in healthy children and identifies the potential risk factors in central Taiwan.

METHODS

A total of 3144 healthy children aged 2-60 months who visited Taichung Veterans General Hospital (TCVGH) were screened for nasal S. aureus carriage from July 2005 to December 2010. Questionnaires included demographic information and potential risk factors for carriage of S. aureus were completed by parents/guardians.

RESULTS

Prevalence of MSSA and MRSA were 12.09% and 5.25%, respectively. The youngest group aged 2-6 months had the highest S. aureus carriage rate, and the carriage rate revealed a peak in summer. The nasal colonization of Streptococcus pneumoniae (S. pneumoniae) was a protective factor against S. aureus colonization. 85% of the MRSA colonizing isolates belonged to clonal complex 59/staphylococcal cassette chromosome type IV or V_T, the local community clone in Taiwan.

CONCLUSION

An increasing trend of MRSA nasal carriage rate in Taiwan had been brought forward, however, it was not observed in central Taiwan during the period of 2005-2010. We found a summer peak on both MRSA and MSSA carriages.

An investigation of vancomycin minimum inhibitory concentration creep among methicillin-resistant Staphylococcus aureus strains isolated from pediatric patients and healthy children in Northern Taiwan

BACKGROUND AND PURPOSE

The phenomenon of vancomycin minimum inhibitory concentration (MIC) creep is an increasingly serious problem in the treatment of methicillin-resistant Staphylococcus aureus (MRSA) infections. In this study, we investigated the vancomycin and daptomycin MIC values of MRSA strains isolated from pediatric patients and MRSA colonized healthy children. Then, we assessed whether there was evidence of clonal dissemination for strains with an MIC to vancomycin of ≥ 1.5 μg/mL.

METHODS

We collected clinical MRSA isolates from pediatric patients and from healthy children colonized with MRSA during 2008-2012 at a tertiary medical center in northern Taiwan and obtained vancomycin and daptomycin MIC values using the Etest method. Pulse-field gel electrophoresis (PFGE) and staphylococcal cassette chromosome (SCCmec) typing were used to assess clonal dissemination for strains with an MIC to vancomycin of ≥ 1.5 μg/mL.

RESULTS

A total 195 MRSA strains were included in this study; 87 were isolated patients with a clinical MRSA infection, and the other 108 strains from nasally colonized healthy children. Vancomycin MIC≥1.5 μg/mL was seen in more clinical isolates (60/87, 69%) than colonized isolates (32/108, 29.6%), p < 0.001. The PFGE typing of both strains revealed multiple pulsotypes.

CONCLUSION

Vancomycin MIC creeps existed in both clinical MRSA isolates and colonized MRSA strains. Great diversity of PFGE typing was in both strains collected. There was no association between the clinical and colonized MRSA isolates with vancomycin MIC creep.

Changing epidemiology of community-associated methicillin-resistant Staphylococcus aureus in the Asia-Pacific region

INTRODUCTION

Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) has become an important threat to public health in the Asia-Pacific region, which is characterized by a large population and relatively insufficient resources. Better understanding on the current status of CA-MRSA in the region is of paramount importance. Areas covered: This article reviews the published literatures on the prevalence, molecular epidemiology, colonization, and hospital spread of CA-MRSA. Expert commentary: The burden of CA-MRSA has been increasing in the past two decades. The molecular epidemiology of CA-MRSA in the Asia-Pacific region shows a marked diversity in each country. Still, some strains - multilocus sequence type (MLST) ST59, ST30, ST72, ST8, and ST772 - are unique clones that have successfully established themselves as predominant, often spreading into nosocomial settings. More coordinated and comprehensive surveillance to understand the true epidemiology of CA-MRSA in the Asia-Pacific region is urgently needed.

Antibiotic susceptibility and genomic variations in Staphylococcus aureus associated with Skin and Soft Tissue Infection (SSTI) disease groups

Background

Staphylococcus aureus is associated with human skin and soft tissue infections (SSTIs); however, the involvement of virulence factors in different clinical presentations is unclear.

Methods

We analyzed methicillin-resistant S. aureus (MRSA) and methicillin-sensitive S. aureus (MSSA) strains from Taiwan to determine correlations among the clinical characteristics of SSTIs, antimicrobial susceptibility and virulence factors of S. aureus with specific genetic backgrounds.

Results

We identified 177 MRSA isolates and 130 MSSA isolates among the 307 SSTI-associated S. aureus isolates. Hospital-acquired (HA)- and community-acquired (CA)-MRSA isolates accounted for 61.6 % and 38.4 % of the isolates, respectively. Clinical presentations in SSTI patients differed significantly for the disease groups. Deep-seated MRSA infections presented with higher amputation rate than MSSA infections. MRSA isolates were all susceptible to linezolid, teicoplanin, and vancomycin, and >94 % of isolates were erythromycin- and clindamycin-resistant. Staphylococcal cassette chromosome (SCCmec) types IV, V, and VII were the most frequent in the CA-MRSA group (n = 68); types III, IV and V were the most frequent in the HA-MRSA group (n = 109). Panton-Valentine leukocidin (PVL) genes were significantly more frequent in CA-MRSA strains (75.0 %) than in HA-MRSA (33.0 %) and MSSA (24.6 %) and were found in 66.7 % (74/111) strains isolated from the abscess group. Exfoliatin A genes were more common in catheter-related exit-site MSSA infections (37.5 %) compared with other MSSA disease groups (P < 0.05). Exfoliatin B and superantigen exotoxin genes were uncommon in all SSTI disease types. Pulsotypes A (ST239), C, and D (ST59) were the predominant MRSA genotypes in deep-seated infections.

Conclusions

If not treated appropriately, deep-seated MRSA-associated infections present with higher amputation rates than deep-seated MSSA-associated infections. PVL-positive MRSA strains caused more frequently pus-forming lesions and less bacteremia and invasive diseases. Methods for discriminating CA-MRSA from HA-MRSA strains are now unreliable due to circulation of both ST 239 and ST 59 strains in the community and nosocomial settings. Initial antibiotic treatments should consider MRSA for patients with SSTIs in areas where MRSA is prevalent.

Comparative Molecular Characteristics of Community-Associated and Healthcare-Associated Methicillin-Resistant Staphylococcus aureus Isolates From Adult Patients in Northern Taiwan

Methicillin-resistant Staphylococcus aureus (MRSA) is an important nosocomial pathogen in hospitals, and increases rapidly in the community, named as community-associated MRSA (CA-MRSA). We conducted a prospective/retrospective study to understand the epidemiology, antimicrobial susceptibility, and molecular characteristics of MRSA infections in adult patients in Taiwan.From March to June, 2012, all clinical MRSA isolates were prospectively collected from adult patients in a tertiary hospital in northern Taiwan. Selective isolates were further characterized. We reviewed the detailed medical record of each case retrospectively.A total of 857 clinical isolates were collected from 555 patients. A total of 749 isolates from 453 patients were classified as healthcare-associated (HA)-MRSA and 108 isolates from 102 patients as CA-MRSA by the epidemiologic criteria. Compared to HA-MRSA, CA-MRSA isolates were significantly more frequently identified from pus (78% vs 28%, P < 0.001) and less frequently from sputum (4.6% vs 43.8%, P < 0.001) and blood (3.7% vs 15%, P = 0.002). CA-MRSA isolates were more susceptible to all antibiotics tested. A total of 102 CA-MRSA and 101 HA-MRSA isolates were characterized, showing significantly different molecular characteristics between CA and HA isolates (P < 0.001). The clone of sequence type (ST) 59/t437 complex, with 2 pulsotypes, accounted for 70% of CA isolates. Three major clones were identified from HA-MRSA isolates, namely clonal complex (CC) 59 (32.7%), CC239 (29.7%), and CC5 (24.8%). Among HA isolates, a significant difference was also seen between community-onset and hospital-onset MRSA isolates in terms of the source of specimens, antibiotic susceptibility patterns, and molecular characteristics.CA-MRSA isolates from adults in northern Taiwan were genetically significantly different from HA isolates. The community clones, CC59, spread into hospitals.

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.

Clindamycin versus trimethoprim-sulfamethoxazole for uncomplicated skin infections

BACKGROUND

Skin and skin-structure infections are common in ambulatory settings. However, the efficacy of various antibiotic regimens in the era of community-acquired methicillin-resistant Staphylococcus aureus (MRSA) is unclear.

METHODS

We enrolled outpatients with uncomplicated skin infections who had cellulitis, abscesses larger than 5 cm in diameter (smaller for younger children), or both. Patients were enrolled at four study sites. All abscesses underwent incision and drainage. Patients were randomly assigned in a 1:1 ratio to receive either clindamycin or trimethoprim-sulfamethoxazole (TMP-SMX) for 10 days. Patients and investigators were unaware of the treatment assignments and microbiologic test results. The primary outcome was clinical cure 7 to 10 days after the end of treatment.

RESULTS

A total of 524 patients were enrolled (264 in the clindamycin group and 260 in the TMP-SMX group), including 155 children (29.6%). One hundred sixty patients (30.5%) had an abscess, 280 (53.4%) had cellulitis, and 82 (15.6%) had mixed infection, defined as at least one abscess lesion and one cellulitis lesion. S. aureus was isolated from the lesions of 217 patients (41.4%); the isolates in 167 (77.0%) of these patients were MRSA. The proportion of patients cured was similar in the two treatment groups in the intention-to-treat population (80.3% in the clindamycin group and 77.7% in the TMP-SMX group; difference, -2.6 percentage points; 95% confidence interval [CI], -10.2 to 4.9; P=0.52) and in the populations of patients who could be evaluated (466 patients; 89.5% in the clindamycin group and 88.2% in the TMP-SMX group; difference, -1.2 percentage points; 95% CI, -7.6 to 5.1; P=0.77). Cure rates did not differ significantly between the two treatments in the subgroups of children, adults, and patients with abscess versus cellulitis. The proportion of patients with adverse events was similar in the two groups.

CONCLUSIONS

We found no significant difference between clindamycin and TMP-SMX, with respect to either efficacy or side-effect profile, for the treatment of uncomplicated skin infections, including both cellulitis and abscesses. (Funded by the National Institute of Allergy and Infectious Diseases and the National Center for Advancing Translational Sciences, National Institutes of Health; ClinicalTrials.gov number, NCT00730028.).

A Comparison of Clinical Features between Community-Associated and Healthcare-Associated Methicillin-Resistant Staphylococcus aureus Keratitis

Purpose. To compare the clinical features of community-associated (CA) and healthcare-associated (HA) methicillin-resistant Staphylococcus aureus (MRSA) keratitis. Methods. Patients presenting with culture-proven MRSA keratitis between January 1, 2006, and December 31, 2010, at Chang Gung Memorial Hospital, Taiwan, were included in this study. The patients' demographic and clinical information were reviewed retrospectively. Antibiotic susceptibility was verified using the disk diffusion method. Results. Information on 26 patients with MRSA keratitis was collected, including 12 cases of CA-MRSA and 14 cases of HA-MRSA. All MRSA isolates were susceptible to vancomycin; the only difference in drug susceptibility was that CA-MRSA isolates were more susceptible to trimethoprim/sulfamethoxazole than HA-MRSA (P = .034). The most common risk factor for MRSA keratitis was ocular surface disease. No significant differences were observed between the 2 groups in terms of clinical features, treatments, and visual outcomes. Conclusion. In Taiwan, CA-MRSA rivals HA-MRSA as a critical cause of MRSA keratitis. Furthermore, CA-MRSA isolates are multidrug resistant. CA-MRSA and HA-MRSA keratitis are clinically indistinguishable, although larger studies are warranted to further evaluate this association.

Clinical and molecular characteristics of invasive community-acquired Staphylococcus aureus infections in Chinese children

Background

This study aims to investigate the clinical features of invasive community-acquired Staphylococcus aureus (CA-SA) infection in Chinese children and analyze its molecular features.

Methods

Clinical data and invasive CA-SA isolates were prospectively collected. Pediatric risk of mortality (PRISM) score was used for disease severity measurement. Molecular typing was then performed, followed by expression analysis for virulence genes.

Results

Among 163 invasive CA-SA infection cases, 71 (43.6%) were methicillin-resistant SA (MRSA) infections and 92 (56.4%) were methicillin-susceptible SA (MSSA). A total of 105 (64.4%) children were younger than 1 year old, and 79.7% (129/163) were under 3 years age. Thirteen kinds of diseases were observed, in which bacteremia and pneumonia accounted for 65.6% (107/163) and 52.8% (86/163), respectively. A total of 112 (68.1%) patients had two or more infective sites simultaneously, and four cases (2.5%) died. CA-MSSA more frequently caused multi-sites infections, bacteremia, and musculoskeletal infection than MRSA. A total of 25 sequence types (STs) were detected. MRSA mainly comprised ST59 (49/71, 69%), whereas the most frequent clonotypes were ST88 (15/92, 16.3%), ST25 (13/92, 14.1%), ST7 (13/92, 14.1%), ST2155 (12/92, 13%), and ST188 (9/92, 9.8%) for MSSA. Seven STs were common to both MSSA and MRSA groups. No differences in clinical presentation or PRISM score were found between the two groups or among different ST. The expression levels of the four known virulence genes varied among the six main ST clones.

Conclusions

Invasive CA-SA infections were characterized by high incidence and multi-site infections in young children in China. The clinical manifestations of CA-MSSA were more frequently associated with multi-site infections, bacteremia and musculoskeletal infection than those of CA-MRSA. Isolated genotypes may be relevant to the expressions of virulence genes, but not to clinical manifestations.

Electronic supplementary material

The online version of this article (doi:10.1186/s12879-014-0582-4) contains supplementary material, which is available to authorized users.

Molecular epidemiology and antimicrobial resistance of methicillin-resistant Staphylococcus aureus bloodstream isolates in Taiwan, 2010

The information of molecular characteristics and antimicrobial susceptibility pattern of methicillin-resistant Staphylococcus aureus (MRSA) is essential for control and treatment of diseases caused by this medically important pathogen. A total of 577 clinical MRSA bloodstream isolates from six major hospitals in Taiwan were determined for molecular types, carriage of Panton-Valentine leukocidin (PVL) and sasX genes and susceptibilities to 9 non-beta-lactam antimicrobial agents. A total of 17 genotypes were identified in 577 strains by pulsotyping. Five major pulsotypes, which included type A (26.2%, belonging to sequence type (ST) 239, carrying type III staphylococcal chromosomal cassette mec (SCCmec), type F (18.9%, ST5-SCCmecII), type C (18.5%, ST59-SCCmecIV), type B (12.0%, ST239-SCCmecIII) and type D (10.9%, ST59-SCCmecV_T/IV), prevailed in each of the six sampled hospitals. PVL and sasX genes were respectively carried by ST59-type D strains and ST239 strains with high frequencies (93.7% and 99.1%, respectively) but rarely detected in strains of other genotypes. Isolates of different genotypes and from different hospitals exhibited distinct antibiograms. Multi-resistance to ≥3 non-beta-lactams was more common in ST239 isolates (100%) than in ST5 isolates (97.2%, P = 0.0347) and ST59 isolates (8.2%, P<0.0001). Multivariate analysis further indicated that the genotype, but not the hospital, was an independent factor associated with muti-resistance of the MRSA strains. In conclusion, five common MRSA clones with distinct antibiograms prevailed in the major hospitals in Taiwan in 2010. The antimicrobial susceptibility pattern of invasive MRSA was mainly determined by the clonal distribution.

Molecular epidemiology of community-associated meticillin-resistant Staphylococcus aureus in Asia

In Asia, most reports on the epidemiology of community-associated meticillin-resistant Staphylococcus aureus (CA-MRSA) are from developed countries, with few data from resource-limited countries, not because of low actual prevalence, but probably because of scarce diagnostic facilities. The rate of MRSA in all community-associated S. aureus infections in Asian countries ranges from 2·5% to 39%. Unlike the predominance of USA300-sequence type (ST) 8 staphylococcal cassette chromosome mec (SCCmec) type IV in the USA, the molecular epidemiology of CA-MRSA in Asia is characterised by clonal heterogeneity, similar to that in Europe. The emergence of CA-MRSA is a threat in both community and hospital settings because such strains are now more prevalent than are health-care-associated MRSA (HA-MRSA) strains. Many epidemic clones are in circulation in Asia and with scarce data available, concern has arisen that CA-MRSA could have devastating results if it becomes epidemic in resource-poor regions. The epidemiology of CA-MRSA in Asia is closely linked with the health of both developing and developed countries. The present situation of CA-MRSA in Asia is important not only for local public health, but also to provide a better understanding of the successful epidemic clones of this global pathogen.

Clinical features and risk factors of mortality for bacteremia due to community-onset healthcare-associated methicillin-resistant S. aureus

Studies comparing adult community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) and community-onset healthcare-associated MRSA (COHCA MRSA bacteremia have not been available. From 1 January 2010 through 30 October 2010, a prospective observational program was conducted among all patients aged >16 years with positive Staphylococcus aureus blood cultures within 48 h after their arrival at the emergency department of our hospital. Clinical course of infection and infection foci of bacteremia were evaluated. Resistance to oxacillin was confirmed with the presence of mecA gene examined by polymerase chain reaction. Presence of TSST-1, PVL gene, SCCmec elements (I-V), mecA gene, and multilocus sequence typing were identified through methods described elsewhere. Univariate and multivariate analysis revealed that chronic renal failure was significantly more common in COHCA-MRSA than in CA-MRSA. In addition, APACHE III score was significantly higher in COHCA-MRSA than in CA-MRSA. Both the 7-day and 30-day mortality rates in COHCA-MRSA, 14.6% (7/48) and 29.2% (14/48), respectively, were higher than those in CA-MRSA without a significant difference. SCCmec II was more common in COHCA-MRSA, but SCCmecVT was more common in CA-MRSA. The majority of MRSA isolates belonged to ST59, ST239, and ST5. ST59 was significantly more common in CA-MRSA, while ST239 was nearly equally common in both CA-MRSA and COHCA-MRSA. SCCmec III and II isolates were the first and second most resistant to the antibiotics commonly used for S. aureus, whereas SCCmecVT isolates were the most susceptible to these antibiotics. We conclude that, although both CA-MRSA and COHCA-MRSA bacteremia had community onset, these 2 MRSA infections were different in underlying diseases, risk of mortality, SCCmec types, sequence types, and antimicrobial susceptibility. It is more appropriate to understand the MRSA pathogen and clinical features based on etiology and ST types than based on the location of disease onset. CA-MRSA and HCA-MRSA should be differentiated also based on etiology and ST types, in addition to location of acquisition.

Emergence of methicillin-resistant Staphylococcus aureus in the Maternity Hospital, Kuwait

OBJECTIVE

To establish the relatedness of methicillin-resistant Staphylococcus aureus (MRSA) isolates in the Maternity Hospital, Kuwait.

MATERIALS AND METHODS

A total of 22 MRSA were isolated from 20 neonates and 1 mother in the Special Care Unit, Maternity Hospital, Kuwait. They were characterized using antibiogram, pulsed-field gel electrophoresis (PFGE), SCCmec typing, spa typing and multi locus sequence typing (MLST), and were screened for genes encoding Panton Valentine leukocidin (PVL) and capsular polysaccharide types 5 and 8.

RESULTS

The isolates were resistant to cadmium acetate (n = 22 or 100%), trimethoprim (n = 13 or 59.1%), gentamicin (n = 7 or 31.8%), ciprofloxacin (n = 5 or 22.7%), erythromycin and clindamycin (n = 2 or 9.1%), tetracycline (n = 2 or 9.1%) and fusidic acid (n = 2 or 9.1%). Eight isolates contained genes for PVL while 15 and 6 carried genes for types 5 and 8 capsular polysaccharide, respectively. Molecular typing distinguished 12 clones. Ten of these clones consisted of 20 isolates belonging to ST60-SCCmec-IV-t3935 (5 isolates), ST6-SCCmec-IV-t6269 (4 isolates), ST194-SCCmec-IV-t6892 (3 isolates), ST1-SCCmec-V-t2962 (2 isolates) and 1 isolate each of ST77-SCCmec-IV-t339, ST935-SCCmec-V-t1084, ST1317-SCCmec-V-t1548, ST9-SCCmec-V-t5801, ST627-SCCmec-IV-t1340 and ST2148-SCCmec-IV-t2810.

CONCLUSION

The study demonstrated the emergence of MRSA including novel ST60 and ST194 clones at the Maternity Hospital in Kuwait.

Community-associated methicillin-resistant Staphylococcus aureus necrotizing pneumonia in a healthy neonate

The number of cases of community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) pneumonia has increased since the late 1990s, with skin and soft tissue infections predominant among neonates. Herein, we present a rare case of CA-MRSA necrotizing pneumonia with empyema following respiratory syncytial virus (RSV) infection in a healthy neonate. Despite prompt vancomycin treatment, the disease worsened and finally we had to perform pneumonectomy. This case highlights the possibility of emerging CA-MRSA-related invasive disease among neonates.

Risk factors and molecular analysis of Panton-Valentine leukocidin-positive methicillin-susceptible Staphylococcus aureus colonization and infection in children

BACKGROUND AND PURPOSE

Limited information is available regarding the role Panton-Valentine leukocidin (PVL) plays in methicillin-susceptible Staphylococcus aureus (MSSA). In this study, we compared the frequency of the PVL gene between MSSA strains isolated from patients with MSSA infections and MSSA strains isolated from patients with evidence of MSSA nasal colonization. We also explored the role that the PVL toxin plays in the ability of MSSA to cause disease as well as the phylogenetic relationship between these S aureus strains.

METHODS

The presence of MSSA strains was screened among children aged <18 years during routine health maintenance visits and among children aged <7 years at daycare centers or kindergartens during the 2003 to 2008 period. At the same time, clinical MSSA isolates were recovered from patients with various types of bacterial infections. Polymerase chain reaction was applied to detect the presence of the PVL and SEB genes in these strains. The strains were also subjected to pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST) studies. Clinical features were compared between patients with PVL-positive and those with PVL-negative isolates.

RESULTS

A total of 495 colonizing MSSA and 71 clinical MSSA isolates were used. The prevalence of PVL-positive S aureus was significantly higher among clinical isolates than among colonizing isolates (14/71, 19.7%; 5/495, 1.0%; p < 0.05). In addition, we found that patients with PVL-positive MSSA infections had a significantly longer duration of fever and tended to have higher C-reactive protein levels than patients with PVL-negative MSSA infections. MLST typing of the 19 PVL-positive MSSA isolates revealed ST59, a strain that is similar to the MLST type of community-associated methicillin-resistant Staphylococcus aureus found in Taiwan. The PFGE typing of PVL-positive/ST59 MSSA isolates revealed multiple pulsotypes.

CONCLUSION

The prevalence of the PVL gene was significantly higher among clinical strains of MSSA (19.7%) than among colonizing strains (1.0%). In addition, patients infected with PVL-positive MSSA strains had fever for a significantly longer duration and tended to have higher C-reactive protein levels than patients with PVL-negative MSSA infections. Our findings imply that PVL may play an important role in the pathogenesis of S aureus infection.

Infective endocarditis caused by community-associated methicillin-resistant Staphylococcus aureus in a previously healthy preschool child

Community-associated methicillin resistant Staphylococcus aureus (CA-MRSA) has been increasingly reported recently and has become an emerging pathogen of infective endocarditis (IE) in adults, but still rarely reported in children. A previously healthy preschool child without any heart anomaly developed IE and pneumonia with pleural effusion. Blood cultures repeatedly yielded MRSA and did not become negative until 13 days after a teicoplanin-containing regimen was administered. In total, a 4-week intravenous antibiotic therapy and an additional 8-week oral antibiotic therapy were given. The patient recovered uneventfully. All five MRSA blood isolates were molecularly characterized and shared common characteristics, which were consistent with those of the endemic CA-MRSA clone in Taiwan. This case highlights that physicians should be aware of the growing role of CA-MRSA in childhood IE and should meticulously choose an appropriate empiric antibiotic regimen for such a severe disease.

Methicillin-resistant Staphylococcus aureus ocular infection: a 10-year hospital-based study

PURPOSE

To characterize the patient demographics, clinical features, and antibiotic susceptibility of ocular infections caused by methicillin-resistant Staphylococcus aureus (MRSA), including community-associated (CA) and healthcare-associated (HA) isolates.

DESIGN

Retrospective, observational study.

PARTICIPANTS

Patients (n = 519) with culture-proven S. aureus ocular infections seen between January 1, 1999, and December 31, 2008, in Chang Gung Memorial Hospital.

METHODS

Data collected included patient demographics and clinical information. Antibiotic susceptibility was verified by disc diffusion method.

MAIN OUTCOME MEASURES

Proportion of MRSA in S. aureus ocular infections and the clinical characteristics, diagnoses, and antibiotic susceptibility patterns of CA-MRSA versus HA-MRSA ocular infections.

RESULTS

We identified 274 patients with MRSA ocular infections, which comprised 181 CA-MRSA and 93 HA-MRSA isolates. The average rate of MRSA in S. aureus infections was 52.8% with a stable trend, whereas the annual ratio of CA-MRSA in ocular MRSA infections averaged 66.1% and tended to increase over the 10-year interval. Patients with ocular CA-MRSA were younger. Lid and lacrimal system disorders were more common, but keratitis, endophthalmitis, and wound infection were less common among CA-MRSA cases than HA-MRSA cases. Both CA-MRSA and HA-MRSA isolates were resistant to clindamycin and erythromycin, but CA-MRSA was more susceptible to sulfamethoxazole/trimethoprim.

CONCLUSIONS

Community-associated MRSA is an important pathogen of ocular infections; CA-MRSA and HA-MRSA ocular infections differ demographically and clinically, but both strains were multi-resistant in Chang Gung Memorial Hospital, one of the biggest referral centers in Taiwan. In a country with a high prevalence of MRSA, ophthalmologists should be aware of such epidemiologic information.

Retrospective study of necrotizing fasciitis and characterization of its associated methicillin-resistant Staphylococcus aureus in Taiwan

Background

Methicillin-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.

Methods

A 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.

Results

In 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.

Conclusion

NF 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.

A nosocomial outbreak of community-associated methicillin-resistant Staphylococcus aureus among healthy newborns and postpartum mothers

BACKGROUND

Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) has increasingly been isolated from individuals with no predisposing risk factors; however, such strains have rarely been linked to outbreaks in the hospital setting. The present study describes the investigation of an outbreak of CA-MRSA that occurred in the maternal-newborn unit of a large community teaching hospital in Toronto, Ontario.

METHODS

Screening and clinical specimens collected from mothers and newborns delivered during the outbreak period, as well as from staff on the affected unit, were submitted for microbiological testing. Computerized delivery logs and nursing notes were reviewed, and a case control study was conducted.

RESULTS

Analysis by pulsed-field gel electrophoresis revealed 38 babies and seven mothers with MRSA colonization and/or infection by the same unique strain (Canadian MRSA-10-related) from September to December 2004. Isolates were characterized as having the staphylococcal chromosome cassette mec type IVa and were positive for the Panton-Valentine leukocidin gene. No one health care worker was associated with all cases; however, mothers and newborns exposed to one particular nurse (Nurse A) were almost 23 times (odds ratio 22.7, 95% CI 3.3 to 195.9) more likely to acquire MRSA than those with no such contact. MRSA was successfully isolated from Nurse A and from an environmental swab of a telephone recently used by Nurse A; both isolates matched the pulsed-field gel electrophoresis pattern of the outbreak strain.

CONCLUSION

The first nosocomial outbreak of CA-MRSA among healthy newborns and postpartum mothers in Canada is described. Effective control of sustained MRSA transmission within an institution may require prompt identification, treatment and monitoring of colonized and/or infected staff.

Panton-Valentine leukocidin in the pathogenesis of community-associated methicillin-resistant Staphylococcus aureus infection

Methicillin-resistant Staphylococcus aureus (MRSA) is an important human pathogen that causes serious infectious diseases and was endemic in hospitals by the late 1960s. Beginning with its first report in the late 1990s, the rapid emergence of community-associated MRSA (CA-MRSA) worldwide responsible for a wide spectrum of diseases ranging from minor skin infections to fatal necrotizing pneumonia has been found in previously healthy individuals without established risk factors for MRSA acquisition. Recently, various virulence determinants unique to CA-MRSA have been uncovered, which explain how the pathogen spreads easily and causes severe CA-MRSA infections among humans. However, the role of Panton-Valentine leukocidin (PVL) in the pathogenesis of CA-MRSA infection is currently a matter of much debate because of conflicting data from epidemiologic studies of CA-MRSA infections and various murine disease models. Identifying specialized pathogenic traits of CA-MRSA and the concerted regulation of these factors remains a challenge that will foster development of vaccines and therapies designed to control CA-MRSA infections. This review focuses on the current status of molecular epidemiology associated with CA-MRSA in Taiwan and progresses toward understanding the enhanced virulence properties of CA-MRSA, with an emphasis on the role of Panton-Valentine leukocidin.

Community-associated meticillin-resistant Staphylococcus aureus in children in Taiwan, 2000s

Meticillin-resistant Staphylococcus aureus (MRSA) has been increasingly identified as the major cause of community-associated (CA) infections in previously healthy hosts since the late 1990s. CA-MRSA strains were recognised as a novel pathogen that is genetically different from healthcare-associated MRSA, and five major epidemic clones have been identified worldwide. In Taiwan, a significantly increasing rate of MRSA carriage and infection amongst healthy subjects was observed in the past decade. Up to 9.5% of healthy Taiwanese children carried MRSA in the nares and >50% of paediatric CA S. aureus infections were MRSA. The adult population was also affected, but this was relatively limited. The majority of CA-MRSA isolates in Taiwan belonged to the sequence type (ST) 59 lineage, defined by multilocus sequence typing, and were multiresistant to non-β-lactams. The clone of ST59 lineage can be further classified into at least two major clones by pulsed-field gel electrophoresis (PFGE) typing, staphylococcal chromosomal cassette mec (SCCmec) elements and Panton-Valentine leukocidin (PVL) genes. The clone characterised as ST59/PFGE type C/SCCmec IV/PVL-negative was prevalent amongst the colonising isolates, whereas ST59/PFGE type D/SCCmec V(T)/PVL-positive was prevalent amongst the clinical isolates. Evidence suggested that the ST59 CA-MRSA clone was not only circulating in Taiwan but also in other areas of the world. In this article, the current status of CA-MRSA in Taiwan was extensively reviewed. The information provided here is not only important for local public health but can also enhance a general understanding of the successful epidemic clones of CA-MRSA worldwide.

Changing trends in antimicrobial resistance of major bacterial pathogens, 1985-2005: a study from a medical center in northern Taiwan

BACKGROUND

Antimicrobial resistance is a major health problem worldwide. We evaluated the antimicrobial resistance trends of 16 major bacterial pathogens at a tertiary medical center in northern Taiwan.

METHODS

We conducted a retrospective review of annual summary documents for antimicrobial susceptibility of clinically isolated gram-positive and gram-negative bacteria from 1985 to 2005. The numbers of isolates and susceptibilities were calculated for three 7-year periods: first period, 1985-1991; second period, 1992-1998; and the third period, 1999-2005.

RESULTS

During the 21-year period, 219,715 bacterial pathogens were identified. A significant increase in incidence over time was found for methicillin-resistant Staphylococcus aureus, methicillin-resistant S epidermidis, penicillin-nonsusceptible Streptococcus pneumoniae, erythromycin-resistant S pneumoniae, vancomycin-resistant enterococci, cefotaxime/ceftriaxone-resistant Escherichia coli and Klebsiella pneumoniae, and imipenem-resistant Acinetobacter baumannii. Additionally, a significant increase in ciprofloxacin resistance rates over time from 1996 to 2005 was noted for E coli, Enterobacter cloacae, and A baumannii (through 1997 to 2005). However, a significant decrease in erythromycin resistance rate with time from 1999 to 2005 was found for Groups A and B streptococci, non-A, B, D streptococci, and S pneumoniae.

CONCLUSION

Resistance to antimicrobial agents increased rapidly in the past two decades in Taiwan and has become very common in major bacterial pathogens. Continuous enforcement of policies to limit use of antimicrobial agents and active surveillance of antimicrobial resistance through a nationwide system are both warranted.

Changes in the nasal colonization with methicillin-resistant Staphylococcus aureus in children: 2004-2009

BACKGROUND

Staphylococcus aureus is an important cause of infection, particularly in persons colonized with this organism. This study compared the annual prevalence and microbiological characteristics of methicillin-resistant S. aureus (MRSA) nasal colonization in Taiwanese children from 2004 through 2009. Risk factors for MRSA were determined for the overall study period.

METHODS

Children from birth to ≤14 years of age presenting for health maintenance visits or attending 1 of 57 kindergartens were recruited. Nasal swabs were obtained, and a questionnaire was administered. The prevalence and microbiological characteristics of MRSA colonization were also calculated for two 3-year periods: 2004-2006 and 2007-2009.

RESULTS

Cultures of the anterior nares were positive for S. aureus in 824 (25.8%) of the 3,200 children, and MRSA colonization was found in 371 (11.6%) children. The prevalence of S. aureus colonization decreased from 28.1% in 2004-2006 to 23.3% in 2007-2009 (p<0.01), whereas the prevalence of MRSA colonization increased from 8.1% to 15.1% during this period (p<0.0001). Multivariate analysis revealed that the independent risk factors for MRSA carriage were different for male and female children, and also among age groups. Most MRSA isolates belonged to sequence type 59 (ST59) (86.3%); however, a multiresistant MRSA clone with ST338 background emerged in 2007-2009. Ten (62.5%) of the 16 MRSA isolates expressed the genotypic profile ST338/staphylococcal cassette chromosome mec V(T)/Panton-Valentine leukocidin-positive/staphylococcal enterotoxin B-positive, and differed only in their antimicrobial susceptibility patterns.

CONCLUSION

The prevalence of nasal colonization by MRSA increased among healthy Taiwanese children from 2004-2006 to 2007-2009, despite an overall decrease in the prevalence of nasal colonization by S. aureus. A multiresistant MRSA clone characterized as ST338 was identified from these children.

Epidemiology and molecular characteristics of community-associated methicillin-resistant and methicillin-susceptible Staphylococcus aureus from skin/soft tissue infections in a children's hospital in Beijing, China

To evaluate the epidemiology and molecular features of community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) and methicillin-sensitive S. aureus (MSSA) from children with skin and soft tissue infections (SSTIs) in Beijing, China, prospective community-acquired S. aureus SSTIs surveillance was conducted at the Beijing Children's Hospital, Beijing, China, for a 12-month period from August 1, 2008, to July 30, 2009. Susceptibility to 12 antimicrobials was determined by the agar dilution method. Genotypic characteristics of CA-MRSA isolates were tested by SCCmec typing, spa typing, and multilocus sequence typing. Panton-Valentine leukocidin gene was detected. Of 1104 cases, 31.8% (351) were community-acquired S. aureus. CA-MRSA accounted for 4% (14) of S. aureus. Among 14 CA-MRSA and 120 MSSA isolates tested, 100% and 91.7% were multidrug resistant, respectively. ST59-MRSA-IVa-t437 (42.9%) was the most common form of CA-MRSA. Spa typing analysis of 120 MSSA isolates was performed, followed by pulsed-field gel electrophoresis and multilocus sequence typing of a selected number of isolates. The most common spa types among MSSA were t084 (8.3%), t091 (5.8%), t034 (5%), t127 (4.2%), t002 (4.2%), and t796 (4.2%). No predominant spa type was seen. Of the MSSA isolates that could be classified into spa-CCs, 15.0% had a genetic background observed in CA-MRSA clones (spa-CC437, spa-CC342, and spa-CC377). Panton-Valentine Leukocidin (PVL)-positive community-acquired S. aureus strains were more commonly associated with skin abscesses than other SSTIs (29.4% versus 5.9%, P < 0.01).In conclusion, CA-MRSA infections are not common among Chinese children with SSTIs. Our findings show that MSSA strains in China have diverse genetic backgrounds.

Comparative molecular analysis of meticillin-resistant Staphylococcus aureus isolates from children with atopic dermatitis and healthy subjects in Taiwan

BACKGROUND

Children with atopic dermatitis (AD) are more frequently colonized by Staphylococcus aureus than healthy children.

OBJECTIVES

To assess whether any relationship exists between nasal meticillin-resistant S. aureus (MRSA) colonization and subsequent skin and soft-tissue infections (SSTI).

PATIENTS AND METHODS

From 2005 through 2006, comparative molecular analyses of 23 MRSA-colonizing isolates from 133 children with AD, 44 MRSA-colonizing isolates from 490 healthy controls, and 12 MRSA-infecting isolates from 20 children with AD and concurrent SSTI were conducted.

RESULTS

Nasal MRSA colonization in children with AD was significantly higher compared with normal individuals (17.3% vs. 9.0%; P = 0.01). The molecular characteristics differed significantly between the MRSA isolates from children with AD and the MRSA-colonizing isolates from healthy controls. The clone characterized as sequence type (ST)59 (338)/pulsotype B/staphylococcal cassette chromosome mec (SCCmec) V(T)/Panton-Valentine leucocidin (PVL)-positive/staphylococcal enterotoxin B (SEB)-positive accounted for half of the MRSA isolates from children with AD, and another clone, characterized as ST59/pulsotype A/SCCmec IV/PVL-negative/SEB-positive accounted for 61% of the MRSA-colonizing isolates from healthy controls.

CONCLUSIONS

We found MRSA colonizing the anterior nares of a large number of Taiwanese children, especially among those with AD. Analysis of our data provides evidence that links MRSA-colonizing isolates to MRSA-infecting isolates from concurrent SSTI in children with AD.

Carriage of community-associated methicillin-resistant Staphylococcus aureus in a cohort of infants in southern Israel: risk factors and molecular features

There are few data about the epidemiology of community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) among children in Israel. This study was intended to identify risk factors for CA-MRSA colonization in healthy infants, to characterize the molecular features of colonizing organisms, and to determine whether they are responsible for health care-associated (HA) infections. Nasal cultures and demographic details were collected from a cohort of healthy infants at 5 visits between the ages of 2 and 12 months. Clinical characteristics of pediatric MRSA bloodstream infections (2001 to 2006) and wound cultures collected over 6 months were also studied. Clonal structure was evaluated by multilocus sequence typing. Isolates were studied for the staphylococcal cassette chromosome mec (SCCmec) type and for the presence of Panton-Valentine leukocidin (PVL) genes. MRSA was cultured at least once from 45 of 659 infants (346 Jewish and 313 Bedouin infants). Forty of 45 (89%) isolates were from Bedouin infants. Twenty-nine of 45 (64.4%) belonged to a new clonal complex, designated CC913, that carries SCCmec IV but not the PVL genes. CC913 was also isolated from 9/14 blood cultures and 7/8 wounds. All CC913 infections occurred in Bedouin children, and all but two were HA. In conclusion, Bedouin origin was the main risk factor for carriage of CA-MRSA. CC913 was dominant both in healthy carriers and as a cause of pediatric HA-MRSA bloodstream infections.

Clinical and molecular epidemiology of infective endocarditis in intravenous drug users

BACKGROUND

Infective endocarditis (IE) in intravenous drug users has been increasing in incidence. The major pathogen used to be methicillin-susceptible Staphylococcus aureus, but resistant isolates have also been increasing. This study aimed to investigate the clinical characteristics of IE in intravenous drug users and to evaluate the molecular patterns of methicillin-resistant S. aureus (MRSA) that cause IE in these drug users.

METHODS

A total of 37 episodes of IE in intravenous drug users hospitalized from 1980 to 2006 at a 1,250-bed teaching hospital in Southern Taiwan were evaluated retrospectively. The genetic relatedness of S. aureus strains was assessed using pulsed-field gel electrophoresis. Polymerase chain reaction was used to detect Panton-Valentine leukocidin (PVL) and staphylococcal gamma-hemolysin (Hlg), and to determine the staphylococcal chromosomal cassette carrying the mecA methicillin-resistant gene (SCCmec) type.

RESULTS

The patients had a mean +/- standard deviation age of 31.5 +/- 9.25 years, with a male predominance of 76%. Hepatitis C was present in all patients. Methicillin-susceptible S. aureus accounted for 76% of infections, and the most common clinical symptoms were fever (97%) and embolic phenomenon (68%). There were 4 MRSA isolates, 3 of which were SCCmec type III. PVL and Hlg genes were found in 2 and 3 MRSA isolates, respectively. Eighty percent similarity was found among the MRSA isolates by pulsed-field gel electrophoresis.

CONCLUSION

Our results suggest that coinfection with hepatitis C was common in intravenous drug users with IE, and that molecular patterns of MRSA isolates had high similarity. SCCmec type III, which is usually hospital-acquired, could have caused the community-associated MRSA endocarditis in our patients.

Trimethoprim-sulfamethoxazole for methicillin-resistant Staphylococcus aureus: a forgotten alternative?

Methicillin-resistant Staphylococcus aureus (MRSA) is a growing infectious concern, mainly in the context of its rapid adaptation to novel antibiotic options for its treatment and the growing morbidity, mortality, and healthcare costs associated with its emergence. the authors sought to investigate whether an older antibiotic, such as trimethoprim-sulfamethoxazole (SXT), may have a role in treating MRSA-related infections, according to the available literature on the subject. The authors reviewed literature data on: resistance of MRSA to SXT worldwide in recent years, efficacy of SXT for MRSA decolonization or prophylaxis from MRSA infections, and clinical therapeutic efficacy of SXT in treating mild or severe community-acquired or hospital-acquired MRSA infections. Resistance varies worldwide, in general being low in the industrialized world and higher in developing countries. SXT is one of the numerous understudied options for MRSA decolonization and is growingly recognized as potentially effective in preventing MRSA infections in certain settings. Limited data on its therapeutic efficacy are encouraging, at least for mild, community-acquired infections. SXT may represent a cost-effective alternative weapon against MRSA. Its utility against this increasingly threatening pathogen need clarification through further clinical trials.

Comparative molecular analysis of community-associated and healthcare-associated methicillin-resistant Staphylococcus aureus isolates from children in northern Taiwan

From August 2004 to July 2005, 210 clinical methicillin-resistant Staphylococcus aureus (MRSA) isolates were collected prospectively from 173 children admitted to Chang Gung Children's Hospital in Taiwan. A comparative molecular analysis of the 111 community-associated (CA) isolates from 102 children and the 99 healthcare-associated (HA) isolates from 71 children was conducted. In comparison to the HA isolates (31%), the CA isolates (90%) were more likely to have been isolated from pus (p <5 x 10(-8)). For each patient with MRSA infection, only the first isolate was selected for molecular analysis. The molecular characteristics differed significantly between the CA and the HA isolates (p <5 x 10(-8)). The clone characterized as sequence type (ST)59/pulsotype D (similar to USA1000)/staphylococcal chromosomal cassette (SCC)mec V(T)/Panton-Valentine leukocidin (PVL)-positive accounted for 69% of the CA isolates, and another clone, characterized as ST239/pulsotype A (Hungary clone)/SCCmec III/PVL-negative, accounted for 45% of the 71 HA isolates. The CA clone of ST59 also accounted for 20% of the HA isolates, including 47% of the 17 community-onset isolates. It was concluded that the molecular characteristics of clinical MRSA isolates from children differed significantly between the CA and the HA isolates in northern Taiwan. However, the CA clone of ST59 was also identified in a substantial proportion of HA isolates.

Risk factors and molecular analysis of panton-valentine leukocidin-positive methicillin-resistant Staphylococcus aureus colonization in healthy children

BACKGROUND

Nasal carriage of Panton-Valentine leukocidin (PVL)-positive methicillin-resistant Staphylococcus aureus (MRSA) is associated with community associated disease. The risk factors for and characteristics of PVL-positive MRSA colonization in the healthy pediatric population are not well understood.

METHODS

Anterior nares cultures were obtained from healthy children < or =14 years of age presenting for health maintenance visits or attending 1 of 8 kindergartens during a 3-year period. A case-control study and molecular typing studies were performed.

RESULTS

A total of 131 (8.1%) of 1615 children had nares cultures positive for MRSA, and 25 (1.5%) were colonized with PVL-positive MRSA. Nasal colonization of PVL-positive MRSA was significantly higher in 2006 than in 2004 (2.8% versus 0.7%; P = 0.006). By multivariate analysis, antibiotic use during the past 12 months (odds ratio, 29.37; 95% confidence interval, 10.72-80.50; P < 0.001) was the major risk factor associated with PVL-positive MRSA colonization in healthy children. Comparison of hospital MRSA strains with the community colonization strains by antimicrobial susceptibility testing, macrolide-lincosamide-streptogramin resistance gene testing, staphylococcal cassette chromosome mec typing, exotoxin profiling, and pulsed-field gel electrophoresis typing revealed that clonal spread of PVL-positive MRSA distinct from clinical hospital strains contributed to the high PVL-positive MRSA burden in the community.

CONCLUSIONS

Nasal PVL-positive MRSA colonization in healthy children with no relationship to the hospital setting has increased significantly in the past 3 years, suggesting that it may be a major factor in the emergence of community-acquired MRSA disease in Taiwan. Previous antibiotic use was associated with PVL-positive MRSA colonization.

Unusually high prevalence of panton-valentine leukocidin genes among methicillin-sensitive Staphylococcus aureus strains carried in the Indonesian population

Few data on the molecular characteristics and epidemiology of Staphylococcus aureus from Indonesia are available. The purpose of the present study was to define S. aureus reservoirs in both the Indonesian community and hospital using a collection of 329 nasal carriage isolates obtained during a survey of 3,995 healthy individuals and patients from Java, Indonesia. Only one strain (0.3%) was identified as methicillin-resistant S. aureus by mecA gene PCR. The Panton-Valentine leukocidin (PVL) genes were detected in 35 methicillin-sensitive S. aureus strains (10.6%). Molecular typing by pulsed-field gel electrophoresis of the 329 isolates showed extensive genetic diversity among both PVL-positive and PVL-negative strains. In Surabaya, Indonesia, however, a cluster was identified that was strongly associated with the presence of the PVL locus (P < 0.0001). As determined by high-throughput amplified fragment length polymorphism, PVL-positive strains occurred throughout all major AFLP clusters (I to IV). Multilocus sequence typing of a subset of isolates showed that most PVL-positive strains belonged to sequence type (ST) 188, while most PVL-negative isolates belonged to ST45. The high prevalence of PVL-positive S. aureus strains in certain regions of Indonesia is of concern since these strains may cause severe infections in the community and in hospitals.

Community-associated methicillin-resistant Staphylococcus aureus infective endocarditis with Panton-Valentine leukocidin gene in an injection drug user with HIV infection

Reports of community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) isolates carrying Panton-Valentine leukocidin (PVL) gene that causes infective endocarditis in injection drug users (IDUs) with human immunodeficiency virus (HIV) infection are rare in the English language literature. We present a case of CA-MRSA infective endocarditis with bilateral septic lung emboli in a previously healthy 45-year-old IDU. This case suggests that PVL gene-positive CA-MRSA should be considered as a potential pathogen in IDUs with infective endocarditis.

Nasal carriage of methicillin-resistant Staphylococcus aureus in household contacts of children with community-acquired diseases in Taiwan

Nasal carriage of methicillin-resistant Staphylococcus aureus was detected in 18 (32%) of 57 children with community-acquired methicillin-resistant S. aureus infection and 30 (25%) of 121 household contacts. By genotyping comparison, 94% and 64% of the colonization isolates from the patients and the contacts, respectively, were indistinguishable from the clinical isolates.

Clinical features and molecular characteristics of invasive community-acquired methicillin-resistant Staphylococcus aureus infections in Taiwanese children

Highly virulent community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) has been associated with morbidity and mortality in various countries of the world. We characterized the clinical and molecular features of pediatric invasive CA-MRSA infections in Taiwan. Between July 2000 and June 2005, 31 previously healthy children with invasive CA-MRSA infections were identified from 423 children with community-onset methicillin-resistant S. aureus infections. The medical records were reviewed. The clinical isolates, if available, were collected for molecular characterization. Sixteen (51.6%) patients were male, and the mean age was 5.7 years. Adolescents accounted for 9 (29%) cases. Eighteen children had bone and/or joint infections, 14 had deep-seated soft tissue infections, 11 had pneumonia, and 2 had central nervous system infections. Multiorgan involvement was identified in 8 of 20 bacteremic cases. Twenty-two patients (71%) required surgical interventions. The mean hospital stay was 27.4 days. All of the 15 available isolates were classified as sequence type (ST) 59 or its single locus variant and belonged to 2 previously reported community-associated clones containing staphylococcal cassette chromosome mec (SCCmec) type IV or type V(T) in Taiwan. Most of the isolates were multiresistant to clindamycin (94%) and erythromycin (97%). Eleven (73.3%) isolates carried pvl genes, and the strains harboring pvl genes were significantly associated with lung involvement. In conclusion, invasive CA-MRSA infections in pediatric population were not limited to young children. Surgical interventions were often required, and a prolonged course of antibiotic therapy was needed. A multiresistant CA-MRSA clone characterized as ST59 was identified from these children in Taiwan.

Experience with linezolid therapy in children with osteoarticular infections

BACKGROUND

The excellent oral bioavailability and the Gram-positive antimicrobial spectrum make linezolid an attractive antibiotic for treatment of osteoarticular infections. The clinical efficacy of this drug has not been previously evaluated for Gram-positive osteoarticular infections in children.

METHODS

Between July 2003 and June 2006, 13 children who received a linezolid-containing regimen for osteoarticular infections were identified from a hospital pharmacy database. The medical records were reviewed and outcomes with regard to clinical efficacy and safety were analyzed.

RESULTS

Eight (61.5%) children were male. Ages ranged from 3 months to 14 years. Nine previously healthy children had acute hematogenous osteoarticular infections involving the pelvis (n = 1) or lower limbs (n = 8). The remaining 4 children had postoperative infections of sternal wounds (n = 2) and fractured lower limbs (n = 2). Causative pathogens included methicillin-resistant Staphylococcus aureus in 11 children, methicillin-susceptible S. aureus in one, and Enterococcus faecium and coagulase-negative staphylococci in one. Surgical debridement was attempted in 9 children and effective antistaphylococcal antibiotics were used in all 13 patients for a median duration of 23 days (range, 5-41 days) before the use of linezolid. Linezolid was administered orally to 10 children as step-down therapy and by the parenteral followed by oral route to 3 children who were intolerant of glycopeptide for a median duration of 20 days (range, 9-36 days). Eleven of the 13 children were cured after management. Two children developed anemia during linezolid therapy. There was no premature cessation of linezolid because of severe adverse effects.

CONCLUSION

Linezolid appears to be useful and well tolerated in step-down therapy or compassionate use for pediatric Gram-positive orthopedic infections. A well-designed prospective comparative study is needed to confirm this observation.