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Background: This study was conducted to investigate the clinical features of hospital-associated infections (HAIs) caused by methicillin-resistant Staphylococcus aureus (MRSA) in Chinese children, and the molecular characteristics of the bacteria., Methods: Patients with HAIs caused by MRSA were identified retrospectively. All isolates were analyzed using molecular typing and antimicrobial susceptibility tests., Results: In total, 150 patients were identified, with a median age of 18 months. The most common infection was pneumonia (55.3%), followed by skin and soft tissue infections (46%). Invasive infections were observed in 52 patients (34.7%), and their hospital stay was longer compared with non-invasive cases (21 vs 12 days, p = 0.047). A total of 16 sequence types (STs) were identified. ST239 and ST59 were common clones, accounting for 46% and 28% of cases, respectively. Compared with cases caused by ST239-SCCmecI-III, patients infected by ST59-SCCmecIV-V had a lower median age (11 vs 41 months, p = 0.047) and more commonly developed invasive infection (50% vs 18.8%, p = 0.006)., Conclusions: Invasive infections accounted for a large proportion of HAIs caused by MRSA. ST59-SCCmecIV/V, a common clone in the community, caused HAIs in Chinese children, more often infected younger children and caused invasive infections.

This study aims to characterize the clinical features of community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) infections in Chinese neonates, as well as the molecular characteristics and expression of key virulence genes of isolates. Clinical information and molecular characteristics of 130 cases were analyzed. Up to 83.8% patients were affected with late-onset infection. Cesarean delivery was the main delivery route, accounting for 74.6% of the total deliveries. Pneumonia (69, 53.1%) was the most common infection. A total of 38 patients (29.2%) suffered from complications. Moreover, 35 cases (26.9%) were invasive infections, among which 88.6% involved multiple organs and 45.7% suffered from complications. Cesarean section and premature birth were the risk factors for invasive CA-MRSA infection. ST59-MRSA-SCCmecIVa-t437 (54, 41.5%) was the most predominant CA-MRSA clone. The hla expression in the ST59 isolates was higher than that in ST910 (p = 0.02) and the hla expression in ST59-SCCmecV-t437 was higher than that in ST59-SCCmecIVa-t437. Approximately, 46.4% (13/28) of the infections caused by ST59-SCCmecV were invasive. This value is higher than that of ST59-SCCmecVa caused infections (14/59, 23.7%) (p = 0.03). This study showed that neonatal CA-MRSA infections in China readily become invasive, involve multiple organs, and are often accompanied by complications. The SCCmec V clone may be more pathogenic than the SCCmecVIa clone., (© 2014 APMIS. Published by John Wiley & Sons Ltd.)

This study aims to investigate the prevalence of a novel cell wall-anchored protein gene, sasX, and to obtain information on the genetic basis for the pathogenic potential of the MRSA strains isolated from Chinese children. The molecular and virulence characteristics of the clinical strains were analyzed. Twenty-two sequence types (STs) were obtained, with six epidemic clones ST59, ST239, ST1, ST910, ST88, and ST338 accounting for 35.8, 22, 6.6, 6.6, 5.3, and 4.1% respectively. The expression levels of hla, psmα, and RNAIII were higher in ST59 than in other STs (p < 0.05). The sasX gene was detected in 26 (10.7%) MRSA isolates. ST239-MRSA-SCCmecIII-t037 (61.5%) was the predominant sasX-positive MRSA clone. The expressions of PSMα and RNAIII were higher in sasX-positive ST239 isolates than in sasX-negative ST239 ones (p < 0.01). Notably, the percentage of invasive infection in infections caused by sasX-positive ST239 MRSA was higher than that by sasX-negative ST239 MRSA (p = 0.008). This study indicated that ST59 was the predominant clone in the MRSA isolates obtained from Chinese children and might have stronger pathogenic potential. The prevalence of the sasX gene in the MRSA isolates from children was relatively low. Furthermore, the sasX gene might be related to the expressions of PSMα and RNAIII and infection invasiveness., (© 2013 APMIS Published by John Wiley & Sons Ltd.)

Aim: To investigate and compare the characteristics of invasive hospital-associated (HA) and community-associated (CA) methicillin-resistant Staphylococcus aureus (MRSA) infections in Chinese children., Methods: Clinical data on 59 paediatric patients with invasive MRSA isolated from the normally sterile sites between 2006 and 2011 were obtained from the clinical MRSA surveillance database of Beijing Children's Hospital. The molecular characteristics of the invasive MRSA strains were then analysed., Results: Invasive MRSA infections rose from 0.89 per 10 000 admissions in 2006 to 3.75 in 2011, with a notable increase in invasive CA-MRSA infections from 0 to 2.43 over the same period. The median age of the CA patients (n = 29) was 0.33 years, compared with 1.17 years for the HA patients (n = 30). Multisite infection, severe pneumonia and empyema were found in 55.2%, 73.1% and 61.5% of CA children and in 30%, 32% and 24% of HA patients, respectively. ST59-MRSA-IVa accounted for 40.7% of all isolates and the Panton-Valentine leukocidin (PVL) gene carriage rate was significantly higher in patients with necrotizing pneumonia and osteoarthritis than in those with other diseases., Conclusion: The incidence of paediatric invasive MRSA infection, particularly CA-MRSA infection, increased in Chinese children between 2006 and 2011. The invasive infections caused by CA-MRSA occurred more frequently in younger children with more severe pneumonia or empyema., (©2013 Foundation Acta Paediatrica. Published by John Wiley & Sons Ltd.)

Detailed molecular analyses of Clonal Complex 59 (CC59) methicillin-resistant Staphylococcus aureus (MRSA) isolates from children in seven major cities across Mainland China were examined. A total of 110 CC59 isolates from invasive and non-invasive diseases were analyzed by multilocus sequence typing (MLST), Staphylococcus cassette chromosome mec (SCCmec) typing, staphylococcal protein A (spa) typing and pulsed-field gel electrophoresis (PFGE). Antibiotics susceptibilities, carriage of plasmids and 42 virulence genes and the expression of virulence factors were examined. ST59 (101/110, 91.8%) was the predominant sequence type (ST), while single locus variants (SLVs) belonging to ST338 (8/110, 7.3%) and ST375 (1/110, 0.9%) were obtained. Three SCCmec types were found, namely type III (2.7%), type IV (74.5%) and type V (22.7%). Seven spa types including t437, which accounted for 87.3%, were determined. Thirteen PFGE types were obtained. PFGE types A and B were the major types totally accounting for 81.8%. The dominant clone was ST59-t437-IVa (65.5%), followed by ST59-t437-V (14.5%). The positive rate of luks-PV and lukF-PV PVL encoding (pvl) gene was 55.5%. Plasmids were detected in 83.6% (92/110) of the strains. The plasmid size ranging from 23.4 kb to 50 kb was most prevalent which accounted for 83.7% (77/92). A significantly lower expression of hla was found in ST59-t437-IVa compared with ST59-t437-V. Among the 110 cases, 61.8% of the patients were less than 1 year old. A total of 90 cases (81.8%) were community-associated (CA) infections whereas 20 cases (18.2%) were hospital-associated (HA) infections. Out of the 110 patients, 36.4% (40/110) were diagnosed with invasive infectious diseases in which ST59-t437-IVa accounted for 67.5% (27/40). In brief, ST59-t437-IVa was proved as the dominant clone in CC59 MRSA strains. The carriage rate of pvl gene was high. CC59 MRSA could result in CA and HA infections. The majortiy of MRSA infection children were in young age.

This study aimed to correlate the multidrug resistance (MDR) and sequence type (ST) clones of community-associated (CA) meticillin-resistant Staphylococcus aureus (MRSA) to identify the genes responsible for clindamycin and mupirocin resistance in S. aureus isolates from paediatric hospitals in mainland China. A total of 435 S. aureus isolates were collected. Compared with CA meticillin-susceptible S. aureus (MSSA), the resistance rates of CA-MRSA to ciprofloxacin, chloramphenicol, gentamicin and tetracycline were higher (19.0 vs 2.6 %, P<0.001; 14.7 vs 3.1 %, P<0.001; 14.7 vs 3.1 %, P<0.01; and 46.0 vs 13.3 %, P<0.001, respectively). Compared with hospital-associated (HA)-MRSA, the resistance rates of CA-MRSA to ciprofloxacin, gentamicin, rifampicin, tetracycline and trimethoprim-sulfamethoxazole were lower (19 vs 94.8 %, P<0.001; 14.7 vs 84.4 %, P<0.001; 5.5 vs 88.3 %, P<0.001; 46 vs 94.8 %, P<0.001; and 1.8 vs 9.1 %, P<0.01, respectively). The resistance rates of CA-MRSA, HA-MRSA and CA-MSSA to clindamycin (92.0, 77.9 and 64.1 %, respectively) and erythromycin (85.9, 77.9 and 63.1 %, respectively) were high. The MDR rates (resistance to three or more non-β-lactams) were 49.6, 100 and 14 % in the CA-MRSA, HA-MRSA and CA-MSSA isolates, respectively. Five of seven ST clones in the CA-MRSA isolates, namely ST59, ST338, ST45, ST910 and ST965, had MDR rates of >50 % (67.9, 87.5, 100, 50 and 83.3 %, respectively). The constitutive phenotype of macrolide-lincosamide-streptogramin B (MLS(B)) resistance (69 %) and the ermB gene (38.1 %) predominated among the MLS(B)-resistant CA S. aureus strains. The resistance rate to mupirocin was 2.3 % and plasmids carrying the mupA gene varied in size between 23 and 54.2 kb in six strains with high-level resistance as determined by Southern blot analysis. The present study showed that resistance to non-β-lactams, especially to clindamycin, is high in CA-MRSA isolates from Chinese children and that the profile of resistance is related to clonal type. This study revealed distinctive patterns of MLS(B)-resistant genes among CA S. aureus isolates.

Objectives: 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., Methods: 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., Results: 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., Conclusions: 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.

This study aimed to evaluate the distribution of superantigen gene profiles and the presence of exfoliative toxin genes in community-acquired meticillin-resistant Staphylococcus aureus (CA-MRSA) isolated from Chinese children, and simultaneously to assess virulence gene profiles and genetic background. Of the CA-MRSA isolates, 88.9 % (88/99) harboured toxin genes, with sek as the most frequent toxin gene (62.6  %), followed by seq (61.6  %), seb (60.6  %) and sea (35.4  %). The eta gene was detected only in one ST398-IVa-spa t034 strain. The sed and etd genes were not found in any of the isolates tested. A total of 38 virulence genotypes were observed, of which the genotype seb-sek-seq (27.3  %, 24/88) comprised the majority, followed by sea-seb-sek-seq (18.2  %, 16/88). The enterotoxin gene cluster including seg-sei-sem-sen-seo-seu predominated at a rate of 15.1  %. The relationship among toxin genotypes, toxin genes encoding profiles of mobile genetic elements and genetic background was analysed. Among 66 clonal complex (CC) 59 isolates, 87.9 % (58/66) were positive for toxin genes, and 75.8  % (50/66) harboured the toxin gene combination seb-sek-seq. Among seb-sek-seq-positive CC59 strains, 42.0  % (21/50) also carried the sea gene. CC59 corresponded exclusively to accessory gene regulator 1 (agr-1). The data presented here enhance our current knowledge on the virulence determinants of CA-MRSA.

Objective: This study was conducted to identify the predictors of mortality and to evaluate the impact of methicillin resistance on outcome in patients with Staphylococcus aureus infection according to underlying conditions and type of infection., Methods: An observational cohort study including 4949 patients with S. aureus infection was conducted. We compared data from patients with MRSA infection with those with MSSA infection., Results: The 30-day mortality rate of MRSA group was significantly higher than that of MSSA group (15.6% vs. 6.2%, P < 0.001). However, MRSA infection was not found to be independent risk factor for mortality after adjusting for other variables (OR = 1.03, 95% CI = 0.80-1.32). When we analyzed patients with S. aureus bacteremia (n = 709), MRSA infection was found to be significantly associated with mortality in multivariate analysis (Adjusted OR = 1.69, 95% CI = 1.15-2.49). When the 30-day mortality rates were compared according to underlying diseases, the 30-day mortality rate of MRSA group was significantly higher than that of MSSA group in patients with malignancy or renal diseases. MRSA infection was also found to be one of the independent risk factors for mortality in patients with malignancy (adjusted OR = 1.69, 95% CI = 1.06-2.70) and in those with renal disease (adjusted OR = 1.70, 95% CI = 1.0-2.89), after adjustment for host variables., Conclusions: Methicillin resistance adversely affected the outcome of patients with S. aureus infection, in patients with cancer or renal disease and in those with S. aureus bacteremia, although MRSA infection was not found to be significantly associated with higher mortality in overall patient population., (Copyright © 2010 The British Infection Society. Published by Elsevier Ltd. All rights reserved.)

Community-acquired, methicillin-resistant Staphylococcus aureus (CA-MRSA) has been associated with morbidity and mortality in various countries. In this study, we characterized the molecular and clinical features of pediatric CA-MRSA pneumonia in China. Between June 2006 and February 2008, 55 previously healthy children confined in eight hospitals countrywide were found to be afflicted with CA-MRSA pneumonia. A total of 55 strains collected from these children were analyzed by multilocus sequence typing (MLST), Staphylococcus cassette chromosome mec (SCCmec) typing, and spa typing. The Panton-Valentine leukocidin (PVL) gene was also detected. Overall, nine STs were obtained, with ST59 (40.4%) established to be the most prevalent type. We first registered the new ST1409 from a child with necrotizing pneumonia. SCCmecIVa was the most predominant type, followed by SCCmec type V. Twelve spa types were identified, of which one new spa type, t5348, was first detected and registered. One typical livestock-associated spa type, t034, was found in a 4-month-old girl living in the countryside. We also found that 40% of those isolates were PVL-positive. In addition, the median age of the children in this study was 10 months. A total of 69% (38/55) of the children with community-acquired pneumonia (CAP) had preceding influenza or influenza-like illness, and three ST910-MRSA-IV strains (PVL gene-positive) were associated with severe necrosis. The results indicated that the recent CA-MRSA found in Chinese children with CAP was largely associated with the spread of the ST59-MRSA-IV clone, and most of the PVL-positive strains in this study did not cause necrotic cases.

The aim of this study was to investigate the molecular characteristics of community-acquired, methicillin-resistant Staphylococcus aureus (CA-MRSA) isolates from Chinese children. Ninety-nine isolates were collected from eight hospitals, and analyzed by multilocus sequence typing, staphylococcal chromosomal cassette mec (SCCmec) type, and spa typing. The Panton-Valentine leukocidin (PVL) gene was also detected. Overall, 14 sequence types (STs) were obtained, and ST59 (58.6%) was found to be the most prevalent, followed by ST1 (8%) and ST338 (8%). We also first registered the new ST1409. SCCmec type IV was the most predominant type at 67.7%, followed by SCCmec type V at 32.3%. SCCmec subtypes IVa, IVc, and IVg were found among the SCCmec type IV strains. Twenty-one spa types were also identified. Four new spa types were found by synchronization with the Ridom SpaServer and referring to the website (http://www.SeqNet.org). ST59-MRSA-IVa with t437 accounted for 40.4% of occurrences, making it the most prevalent clone. The prevalence of PVL genes was 58.6%, and multidrug resistance was observed in 95% of all isolates. This result indicates that CA-MRSA isolates in Chinese children are largely associated with the ST59-MRSA-IV clone, and that the predominant clones of CA-MRSA are spread all over the country.

Detailed molecular analyses of Clonal Complex 59 (CC59) methicillin-resistant Staphylococcus aureus (MRSA) isolates from children in seven major cities across Mainland China were examined. A total of 110 CC59 isolates from invasive and non-invasive diseases were analyzed by multilocus sequence typing (MLST), Staphylococcus cassette chromosome mec (SCCmec) typing, staphylococcal protein A (spa) typing and pulsed-field gel electrophoresis (PFGE). Antibiotics susceptibilities, carriage of plasmids and 42 virulence genes and the expression of virulence factors were examined. ST59 (101/110, 91.8%) was the predominant sequence type (ST), while single locus variants (SLVs) belonging to ST338 (8/110, 7.3%) and ST375 (1/110, 0.9%) were obtained. Three SCCmec types were found, namely type III (2.7%), type IV (74.5%) and type V (22.7%). Seven spa types including t437, which accounted for 87.3%, were determined. Thirteen PFGE types were obtained. PFGE types A and B were the major types totally accounting for 81.8%. The dominant clone was ST59-t437-IVa (65.5%), followed by ST59-t437-V (14.5%). The positive rate of luks-PV and lukF-PV PVL encoding (pvl) gene was 55.5%. Plasmids were detected in 83.6% (92/110) of the strains. The plasmid size ranging from 23.4 kb to 50 kb was most prevalent which accounted for 83.7% (77/92). A significantly lower expression of hla was found in ST59-t437-IVa compared with ST59-t437-V. Among the 110 cases, 61.8% of the patients were less than 1 year old. A total of 90 cases (81.8%) were community-associated (CA) infections whereas 20 cases (18.2%) were hospital-associated (HA) infections. Out of the 110 patients, 36.4% (40/110) were diagnosed with invasive infectious diseases in which ST59-t437-IVa accounted for 67.5% (27/40). In brief, ST59-t437-IVa was proved as the dominant clone in CC59 MRSA strains. The carriage rate of pvl gene was high. CC59 MRSA could result in CA and HA infections. The majortiy of MRSA infection children were in young age. [ABSTRACT FROM AUTHOR]

ABSTRACT To determine the variation in the Panton-Valentine leukocidin (PVL) gene sequences and different PVL-encoding phages of Staphylococcus aureus strains collected from children in mainland China, fifty-eight strains with PVL collected from 2007 to 2009 were used. Their molecular characteristics were examined. Primers were designed to sequence the PVL genes. Six PVL-encoding phages (ϕPVL, ϕ108PVL, ϕSLT, ϕSa2MW, ϕSa2958, and ϕSa2USA) were identified by PCR. Eleven sequence types (ST) were detected with ST59 (39.7%, 23/58) the most frequent ST, followed by 910 (22.4%, 13/58), and 338 (12.1%, 7/58). Single nucleotide polymorphisms (SNP) were identified at 11 locations in the PVL genes. SNP (nucleotide 1396, A→G) and SNP (nucleotide 1546, A→G) were observed in >10 sequences. Four additional SNP were non-synonymous. Both SNP (nucleotide 16, C→A) and SNP (nucleotide 62, C→T) were present in the same ST59 strain. SNP (nucleotide 527, A→G) was present in five strains belonging to ST30, 121, 1, and 93. SNP (nucleotide 1436, A→C) was present in one ST30 strain. Fifteen strains belonging to ST910, ST217, and ST30 carried a PVL phage that had an icosahedral head morphology. Nine ST59 strains carried ϕ108PVL. Three ST88 strains carried a PVL phage that had an elongated head morphology. Twenty-seven strains, including 60.9% (14/23) of ST59 and all ST338 strains, had no detectable phage. In conclusion, sequence variation in PVL genes and PVL-encoding phages was generally related to the lineage. ST59 strains may indeed carry novel PVL phages. [ABSTRACT FROM AUTHOR]

Abstract: 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. [Copyright &y& Elsevier]