Screening of pathogenic molecular markers of Staphylococcus aureus in children based on whole genome sequencing technology / 中国当代儿科杂志

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.

Dose-response relationship between age and Streptococcus pneumoniae vaccination coverage in kindergarten children / 中国当代儿科杂志

OBJECTIVES@#To investigate the potential relationship between age and Streptococcus pneumoniae vaccination coverage in kindergarten children, and to provide a basis for guiding vaccination and developing new protein vaccines.@*METHODS@#The stratified cluster random sampling method was used to select 1 830 healthy children from six kindergartens in Shunde District, Foshan City, China, and nasopharyngeal swabs were collected for the isolation and identification of Streptococcus pneumoniae. The logistic regression model based on restricted cubic spline was used to analyze the dose-response relationship between age and Streptococcus pneumoniae vaccination coverage.@*RESULTS@#The rate of nasal Streptococcus pneumoniae carriage was 22.46% (411/1 830) among the kindergarten children, with the predominant serotypes of 6B, 19F, 15A, 23A, 34, and 23F. The coverage rates of 10-valent pneumococcal conjugate vaccine (PCV10) and 13-valent pneumococcal conjugate vaccine (PCV13) were 53.0% and 57.9%, respectively, and there was a significant non-linear dose-response relationship between age and the coverage rates of PCV10 and PCV13 (P<0.05), with a higher coverage rate of PCV10 (88.0%) and PCV13 (91.1%) in the children aged 2 years. There was a significant non-linear dose-response relationship between age and the coverage rates of pilus islet 1 (PI-1) and pilus islet 2 (PI-2) (P<0.05), with a lower vaccination coverage rate for PI-1 (37.7%) and PI-2 (16.1%). The coverage rates of PI-1 (13.0%-58.5%) and PI-2 (6.0%-29.4%) were lower in all age groups. The virulence genes lytA (99.5%) and ply (99.0%) associated with candidate protein vaccines showed higher vaccination coverage rates.@*CONCLUSIONS@#There is a significant non-linear dose-response relationship between the age of kindergarten children and the coverage rates of PCV10 and PCV13 serotypes, and kindergarten children aged 2 years have a relatively high coverage rate of PCV. The high prevalence of the virulence genes lytA and ply shows that they are expected to become candidate virulence factors for the development of a new generation of recombinant protein vaccines.

Comparison of antibiotic resistance spectrum between methicillin-resistant and methicillin-susceptible coagulase-negative staphylococci nasal isolates among 1 001 HIV infectors / 中华疾病控制杂志

Objective We aimed to elucidate the prevalence and the antibiotic resistance spectrum of nasal coagulase-negative staphylococci (CoNS) colonization among HIV infectors in Guangzhou. Method After isolation and identification, all CoNS isolates were tested for the antibiotic susceptibility, and the antibiotic resistance genes. Result Among the 1 001 HIV infectors, the prevalence of CoNS and MRCoNS were 57.44% and 48.15%, respectively. The three predominant resistant antibiotics of MRCoNS isolates were penicillin, erythromycin and trimethoprim-sulfame thoxazole, while predominant detection rates of genes were Aac(6’)-aph(2’)、ermC and linA genes. The multidrug resistance rate of MRCoNS isolates were significantly higher than methicillin-susceptible coagulase-negative staphylococci (MSCoNS) isolates (80.69% versus 39.66%, P<0.001, OR=6.36). Conclusions The prevalence and multidrug resistant rates of nasal colonization CoNS and MRCoNS are high among HIV infectors in Guangzhou. MRCoNS isolates were 6.36 times more likely to be of multidrug resistance than MSCoNS isolates.

Carriage prevalence and drug resistance profile of MRSA and MSSA strains isolated from newborns / 中华疾病控制杂志

Objective To determine the carriage prevalence and antibiotics resistance profile of methicillin-resistant staphylococcus aureus(MRSA) and methicillin-sensitive staphylococcus aureus(MSSA) strains isolated from newborns. Methods A cross-sectional study was conducted in two hospitals in Shenzhen from August to November 2015. Cotton swab samples were collected from 1834 newborns. Staphylococcus aureus was identified by general laboratory tests, and antimicrobial-susceptibility profiles was tested. Results In total, 3.27% (60/1 834) Staphylococcus aureus (SA) strains were isolated, including 0.82% (15/1 834) MRSA and 2.45% (45/1 834) MSSA. Most MRSA and MSSA strains were resistant to penicillin and erythromycin but less than 10% strains resistant to linezolid. Drugs resistance rates of MRSA to erythromycin, moxifloxacin and clindamycin were all higher than that of MSSA (all P<0.05). The multidrug-resistant risk of MRSA (80.00%) was 12.36 times higher than that of MSSA (24.44%). Conclusions Multidrug-resistant SA especially MRSA strains isolated from newborns had the higher prevalence, the drugs resistance rate of MRSA strains was more serious than that of MSSA.