OBJECTIVES: To explore the molecular characteristics of Staphylococcus aureus (S. aureus) in children, and to compare the molecular characteristics of different types of strains (infection and colonization strains) so as to reveal pathogenic molecular markers of S. aureus. METHODS: A cross-sectional study design was used to conduct nasopharyngeal swab sampling from healthy children in the community and clinical samples from infected children in the hospital. Whole genome sequencing was used to detect antibiotic resistance genes and virulence genes. A random forest method to used to screen pathogenic markers. RESULTS: A total of 512 S. aureus strains were detected, including 272 infection strains and 240 colonization strains. For virulence genes, the carrying rates of enterotoxin genes (seb and sep), extracellular enzyme coding genes (splA, splB, splE and edinC), leukocytotoxin genes (lukD, lukE, lukF-PV and lukS-PV) and epidermal exfoliating genes (eta and etb) in infection strains were higher than those in colonization strains. But the carrying rates of enterotoxin genes (sec, sec3, seg, seh, sei, sel, sem, sen, seo and seu) were lower in infection strains than in colonization strains (P<0.05). For antibiotic resistance genes, the carrying rates of lnuA, lnuG, aadD, tetK and dfrG were significantly higher in infection strains than in colonization strains (P<0.05). The accuracy of cross-validation of the random forest model for screening pathogenic markers of S. aureus before and after screening was 69% and 68%, respectively, and the area under the curve was 0.75 and 0.70, respectively. The random forest model finally screened out 16 pathogenic markers (sem, etb, splE, sep, ser, mecA, lnuA, sea, blaZ, cat(pC233), blaTEm-1A, aph(3')-III, ermB, ermA, ant(9)-Ia and ant(6)-Ia). The top five variables in the variable importance ranking were sem (OR=0.40), etb (OR=3.95), splE (OR=1.68), sep (OR=3.97), and ser (OR=1.68). CONCLUSIONS The random forest model can screen out pathogenic markers of S. aureus and exhibits a superior predictive performance, providing genetic evidence for tracing highly pathogenic S. aureus and conducting precise targeted interventions.
Child ; Humans ; Staphylococcus aureus/genetics* ; Cross-Sectional Studies ; Enterotoxins/genetics* ; Staphylococcal Infections ; Whole Genome Sequencing

Humans ; Staphylococcus lugdunensis/genetics* ; Peptides, Cyclic ; Chromosomes ; Operon/genetics* ; Staphylococcal Infections/genetics* ; Bacterial Proteins/genetics* ; Anti-Bacterial Agents

OBJECTIVETo detect the enterotoxin genes of Staphylococcus aureus (SA) isolated from clinical specimens and analyze the correlation between enterotoxin genes and drug resistance of SA.

METHODSThe mecA gene and enterotoxin genes A-F of clinical SA isolates were identified by polymerase chain reaction (PCR), and the genes were sequenced to investigate the correlation of these genes to drug resistance.

RESULTSThe detection rate of enterotoxin genes was 100% in 67 methicillin- resistant SA (MRSA), showing no significant difference from the rate in 57 methicillin-sensitive SA (MSSA) (83.5%, χ(2)=0.203, P>0.05). Of the 116 strains carrying enterotoxin genes (93.5%), the detection rates of SEA, SEB, SEC, SED and SEF were 90.5%, 6.9%, 61.3%, 5.2%, 25.9% and 93.5%, respectively, and none of the strains were positive for SEE gene. In these strains, 78 (67.2%) carried 2 or more enterotoxin genes, and the main genotypes were SEA and SEC (33.6%), SEA and SEF (7.8%), and SEA and SEC and SEF (13.8%). Compared with the strains carrying a single enterotoxin gene, those with multiple enterotoxin genes showed a higher drug resistance rate, among which 75% of the SA strains carrying SEA+SEC+SEF were resistant to SXT, significantly higher than the rates of SA carrying SEA (28.6%) and SEA+SEC (38.7%) (P<0.05). The SA strains carrying SEA+SEC+SEF and SEA+SEF showed significantly higher amikacin resistance rates than SA strain carrying SEA (75.0%, 77.0%, 21.5%, respectively, P<0.05).

CONCLUSIONClinical isolates of SA carrying multiple enterotoxin genes have a higher drug resistance rate than those with a single enterotoxin gene, suggesting the the important role of enterotoxin in multidrug resistance.

Drug Resistance, Multiple, Bacterial ; genetics ; Enterotoxins ; genetics ; Humans ; Staphylococcal Infections ; microbiology ; Staphylococcus aureus ; drug effects ; genetics ; isolation & purification

OBJECTIVETo investigate the pathogen causing soft-tissue pyogenic infection in neonate.

METHODSThe isolates of Staphylococcus aureus were obtained from liquor puris and blood by routine method. The Automated Microbiology Analyzer was used for identification and antimicrobial susceptibility test of the isolates. Panton-Valentine leukocidin (PVL) genes were determined by multiplex PCR in the isolates of Staphylococcus aureus. Multilocus sequence typing (MLST) was used to determine the sequence types (STs) of the isolates. The genotypes of SCCmec were also determined by another multiplex PCR in the isolates of methicillin-resistant Staphylococcus aureus (MRSA).

RESULTSIn 3 cases of neonate with soft-tissue pyogenic infection, 2 strains of Staphylococcus aureus isolated from liquor puris in 2 cases. 2 strains of Staphylococcus aureus were isolated from liquor puris and blood from another case. All 4 isolates were methicillin-resistant Staphylococcus aureus (MRSA) strains carrying PVL genes. Their SCCmec types were SCCmec IIIA. The STs of 4 isolates were ST88. The antimicrobial-resistance profile of the isolates were the same except erythromycin.

CONCLUSIONSoft-tissue pyogenic infection in the 3 neonates was caused by the same clone of MRSA carrying PVL genes.

Bacterial Toxins ; genetics ; Exotoxins ; genetics ; Humans ; Infant, Newborn ; Leukocidins ; genetics ; Male ; Methicillin-Resistant Staphylococcus aureus ; genetics ; Multilocus Sequence Typing ; Soft Tissue Infections ; microbiology ; Staphylococcal Infections ; microbiology

Objective: To understand the population structure of food-borne Staphylococcus (S.) aureus in China. Methods: Whole genome sequencing was used to analyze 763 food-borne S. aureus strains from 16 provinces in China from 2006 to 2020. Multilocus sequence typing (MLST), staphylococcal protein A gene (spa) typing, and staphylococcal chromosome cassettemec (SCCmec) typing were conducted, and minimum spanning tree based on ST types (STs) was constructed by BioNumerics 7.5 software. Thirty-one S. aureus strains isolated from imported food products were also included in constructing the genome phylogenetic tree. Results: A total of 90 STs (20 novel types) and 160 spa types were detected in the 763 S. aureus isolates. The 72 STs (72/90, 80.0%) were related to 22 clone complexes. The predominant clone complexes were CC7, CC1, CC5, CC398, CC188, CC59, CC6, CC88, CC15, and CC25, accounting for 82.44% (629/763) of the total. The STs and spa types in the predominant clone complexes changed over the years. The methicillin-resistant S. aureus (MRSA) detection rate was 7.60%, and 7 SCCmec types were identified. The ST59-t437-Ⅳa (17.24%, 10/58), ST239-t030-Ⅲ (12.07%, 7/58), ST59-t437-Ⅴb (8.62%, 5/58), ST338-t437-Ⅴb (6.90%, 4/58) and ST338-t441-Ⅴb (6.90%, 4/58) were the main types in MRSA strains. The genome phylogenetic tree had two clades, and the strains with the same CC, ST, and spa types clustered together. All CC7 methicillin sensitive S. aureus strains were included in Clade1, while 21 clone complexes and all MRSA strains were in Clade2. The MRSA strains clustered according to the SCCmec and STs. The strains from imported food products in CC398, CC7, CC30, CC12, and CC188 had far distances from Chinese strains in the tree. Conclusions: In this study, the predominant clone complexes of food-borne strains were CC7, CC1, CC5, CC398, CC188, CC59, CC6, CC88, CC15, and CC25, which overlapped with the previously reported clone complexes of hospital and community-associated strains in China, suggesting that close attention needs to be paid to food, a vehicle of pathogen transmission in community and food poisoning.
Humans ; Staphylococcus aureus/genetics* ; Methicillin-Resistant Staphylococcus aureus/genetics* ; Multilocus Sequence Typing ; Phylogeny ; Staphylococcal Infections/epidemiology* ; China/epidemiology*

OBJECTIVETo genotypically characterize methicillin-resistant Staphylococcus aureus (MRSA) strains isolated from medical and surgical wards in Universiti Kebangsaan Malaysia Medical Centre (UKMMC) in 2009.

METHODSMRSA strains were collected and molecularly typed by pulsed-field gel electrophoresis (PFGE).

RESULTSPFGE typing on 180 MRSA isolated in UKMMC identified 5 pulsotypes (A-E) and 6 singletons, where pulsotypes B and C were suspected to be divergent clones originating from a single ancestor. This study also showed that most MRSA strains were isolated from swab (119 isolates), followed by blood (22 isolates), tracheal aspirate (11 isolates) and sputum (10 isolates). On the other hand, urine and bone isolates were less, which were 4 and 1 isolates, respectively. The distribution of different pulsotypes of MRSA among wards suggested that MRSA was communicated in surgical and medical wards in UKMMC, with pulsotype B MRSA as the dominant strain. Besides, it was found that most deceased patients were infected by pulsotype B MRSA, however, no particular pulsotype could be associated with patient age, underlying disease, or ward of admittance.

CONCLUSIONSFive pulsotypes of MRSA and 6 singletons were identified, with pulsotype B MRSA as the endemic strains circulating in these wards, which is useful in establishment of preventive measures against MRSA transmission.

Electrophoresis, Gel, Pulsed-Field ; Evolution, Molecular ; Hospitals ; Malaysia ; epidemiology ; Methicillin-Resistant Staphylococcus aureus ; genetics ; isolation & purification ; Staphylococcal Infections ; epidemiology ; microbiology

Community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) is an increasingly common worldwide and colonizing S. aureus strains may serve as the causative pathogen for overt clinical infections. This study was performed to determine whether the pathogenic CA-MRSA isolate in clinical infections was genetically related to the MRSA isolates in community carriers. We prospectively collected a total of 42 CA-MRSA isolates (23 clinical infection isolates and 19 colonization isolates) in a local region of Korea. Antimicrobial susceptibility tests, staphylococcal toxin assays, SCCmec typing, multilocus sequence typing (MLST), and spa (staphylococcal protein A) typing were performed with all isolates. Thirty-four (81%) of 42 CA-MRSA isolates belonged to sequence type (ST) 72 in the MLST analysis. The distribution of STs did not differ significantly between colonization and clinical infection isolates (89.5% [17/19] vs. 73.9% [17/23], P=0.26). Among the ST72-MRSA isolates, spa type t664 (18, 52.9%) and t324 (8, 23.5%) were common in both groups. This study demonstrates that the community-associated MRSA strains from patients with clinical infections are closely related to the strains found in carriers from one local community.
Community-Acquired Infections/microbiology ; Genotype ; Humans ; Methicillin-Resistant Staphylococcus aureus/*genetics/isolation & purification ; Microbial Sensitivity Tests ; Prospective Studies ; Republic of Korea ; Staphylococcal Infections/*microbiology

Healthcare-associated infections caused by methicillin-resistant Staphylococcus aureus (MRSA) have recently become an important issue for healthcare facilities due to high rates of infection, mortality, and high treatment costs. We investigated the frequency of MRSA in healthcare workers (HCWs) via nasal carriage and assessed the performance of the LightCycler(R) MRSA Advanced test. We tested nasal swabs from the anterior nares of participating HCWs at an intensive care unit. Nasal swabs were identified as S. aureus, methicillin-sensitive or methicillin-resistant coagulase-negative staphylococci (MSCoNS or MRCoNS), or MRSA by using conventional culture and the LightCycler(R) MRSA Advanced test. Of the 142 HCWs who participated in this study, only 11 participants (7.8%) were MRSA-positive by conventional culture and MRSA ID, and 24 (16.9%) were positive for mecA by real time polymerase chain reaction (PCR). In terms of diagnostic performance, the LightCycler(R) MRSA Advanced test had a sensitivity of 100%, a specificity of 90.1%, a positive predictive value of 45.8%, and a negative predictive value of 100% compared with conventional culture method. The detection limit of the LightCycler(R) MRSA Advanced test was 103 colony/mL. We concluded that real-time PCR was able to rapidly and sensitively detect MRSA in HCWs. However, MRSA must be confirmed by culture due to false positivity.
Bacterial Proteins/genetics ; False Positive Reactions ; Humans ; Methicillin-Resistant Staphylococcus aureus/genetics/*isolation & purification ; Nurses ; Physicians ; Real-Time Polymerase Chain Reaction/methods ; Sensitivity and Specificity ; Staphylococcal Infections/*diagnosis

The most important factor in the pathogenesis of biomaterial-associated Staphylococcal infections is the formation of bacterial biofilms. Biofilm formation was regulated or influenced by quorum sensing. One of the quorum sensing systems agr is genus specific which controls the expression of a series of toxins and virulence factors and the interaction with the innate immune system. New research indicates that the role of agr during infection is controversial. The research progress will play an important role in the development of novel antibacterial agents and management of device-related infection of Staphylococci.
Bacterial Proteins ; physiology ; Biocompatible Materials ; Biofilms ; growth & development ; Gene Expression Regulation, Bacterial ; Humans ; Signal Transduction ; genetics ; Staphylococcal Infections ; microbiology ; Staphylococcus ; genetics ; physiology ; Trans-Activators ; physiology

BACKGROUND: The BD GeneOhm MRSA PCR assay (Becton Dickinson, USA) is a qualitative real-time PCR test for rapid detection of nasal colonization of methicillin-resistant Staphylococcus aureus (MRSA). We evaluated the performance of BD GeneOhm MRSA PCR assay versus MRSASelect (Bio-Rad, France) and broth enrichment cultures for detection of MRSA from nasal swabs. METHODS: From August 2008 to January 2009, 295 nasal swabs were taken from patients in intensive care units and transported to the laboratory with BD CultureSwab Liquid Stuart Single Swab (Becton Dickinson, USA). The swabs were inoculated onto MRSASelect first and then suspended into GeneOhm sample buffer: 100 microliter of the suspension was inoculated into 6.5% NaCl-tryptic soy broth (Becton Dickinson, USA), which was subcultured on MRSASelect after overnight incubation (TSBS). Performances of GeneOhm MRSA and MRSASelect were compared to TSBS. RESULTS: With GeneOhm MRSA, 125 swabs (44.6%) were positive for MRSA, 13 (4.4%) were unresolved, and 2 were not determined. With MRSASelect and TSBS 86 (29.4%) and 106 swabs (36.2%), respectively, were positive. The sensitivity, specificity, and positive and negative predictive value of GeneOhm MRSA were 85.8%, 77.5%, and 72.8% and 93.5%, respectively, and corresponding values for MRSASelect were 78.3%, 94.8%, and 96.5% and 88.9%. Of the 33 patients whose 34 specimens were found false positive in GeneOhm MRSA, 23 patients were MRSA-positive either previously or subsequently to this study. All of the 10 patients with false-negative specimens in GeneOhm MRSA PCR assay were previously MRSA or methicilln-resistant coagulase negative staphylococci (MRCNS)-positive and were treated for MRSA, but they became MRSA-positive after 1 to 4 negative surveillance cultures. CONCLUSIONS: GeneOhm MRSA PCR assay showed a relatively high negative predictive value. However, its low specificity and frequent occurrence of unresolved results would be problematic in the endemic areas with a high prevalence of MRSA.
Endemic Diseases ; Humans ; Intensive Care Units ; Methicillin-Resistant Staphylococcus aureus/genetics/*isolation & purification ; Nose/*microbiology ; Polymerase Chain Reaction/*methods ; Reagent Kits, Diagnostic ; Sensitivity and Specificity ; Staphylococcal Infections/*diagnosis/epidemiology