Nasopharyngeal carriage of Streptococcus pneumoniae among children aged 30 days to <60 months in Beijing and Shenzhen, China (2018-2021) during pneumococcal conjugate vaccine introduction and the coronavirus disease (COVID-19) pandemic.

Objectives: To describe the carriage rate, serotype distribution, and antimicrobial susceptibility patterns of Streptococcus pneumoniae (S. pneumoniae) nasopharyngeal (NP) isolates among healthy children aged 30 days to <60 months in the cities of Beijing and Shenzhen during 2018-2021. Methods: A NP swab sample was collected among four annual cohorts of healthy children at routine well-child visits. S. pneumoniae was identified by culture, optochin sensitivity and bile solubility, serotypes determined by latex agglutination and Quellung, and antimicrobial susceptibility testing performed using E-test strips. Results: S. pneumoniae NP carriage was 13.1% (645/4,911), with the highest S. pneumoniae carriage prevalence (15.3%) observed in 25 to <60 months. The carriage prevalence was 15.1% in children 13-24 months, 13.2% in children 7-12 months, and 8.2% in children 30 days to 6 months (P < 0.01). Living with siblings [20.0% vs. 9.4%: OR: 2.42 (95% CI: 2.05-2.87)] or attending day-care [31.8% vs. 11.3%: OR: 3.67 (95% CI: 2.94-4.57)] increased the risk (P < 0.01). During the period (January 2020-April 2021) of strict non-pharmaceutical interventions to prevent and control the COVID-19 pandemic, the proportion of children with S. pneumoniae colonization declined from 16.0% (94/587) to 5.8% (108/1,848) in Beijing while increasing from 14.5% (64/443) to 18.6% (379/2,033) in Shenzhen. Among S. pneumoniae isolates, 36.7% (237/645) belonged to 13-valent pneumococcal conjugate vaccine (PCV13) serotypes, 64.3% (408/645) were non-PCV13 serotypes, including 20.8% (134/645) non-serotypeable S. pneumoniae (NST). A total of 158/644 isolates (24.5%) were MDR. For the PCV13 isolates, MDR was detected in 36.3% (86/237) of isolates; in comparison, 17.6% (72/407) of non-PCV13 serotypes, including NST, were MDR (P < 0.01). S. pneumoniae NP carriage was detected in 10.7% of children with previous pneumococcal vaccination (PCV7 or PCV13 only) compared with 14.9% in children without previous pneumococcal vaccination. Conclusions: The highest S. pneumoniae carriage prevalence were found in the oldest age group (25 to <60 months) and in children living with siblings or attending day-care. Vaccination with PCV7 or PCV13 was associated with lower PCV13-serotype colonization. In Beijing, S. pneumoniae carriage significantly declined during the COVID-19 pandemic.

Serotype distribution, antimicrobial resistance, and molecular characterization of invasive group B Streptococcus isolates recovered from Chinese neonates.

BACKGROUND: Group B Streptococcus (GBS) is an important neonatal pathogen associated with high morbidity and mortality in developed countries. However, data describing neonatal GBS disease in developing countries, particularly in Asia, are largely incomplete. The aim of this study was to determine the serotype distribution, antimicrobial resistance, and molecular characteristics of invasive GBS isolates recovered from Chinese neonates. METHODS: From 2008 to 2013, 40 GBS isolates were recovered from infected neonates less than 3 months of age. All isolates were identified with the CAMP test and commercially available techniques. Serotyping was performed by latex agglutination. Antibiotic susceptibility was tested with Etest strips and the disk diffusion method. Multilocus sequence typing and erythromycin resistance gene detection (ermB and mefA) were performed by PCR. RESULTS: Four serotypes were identified. Serotype III (85%) was the most prevalent, followed by Ia (7.5%), Ib (5%), and V (2.5%). All isolates were sensitive to penicillin, ceftriaxone, and levofloxacin. However, resistance to erythromycin (92.5%), clindamycin (87.5%), and tetracycline (100%) was observed. Among erythromycin-resistant isolates, 73.0% carried the ermB gene alone, 5.4% carried the mefA gene alone, and 21.6% expressed both ermB and mefA genes. A total of seven sequence types (STs) were identified; the most prevalent was ST17, accounting for 80% of all isolates. Further, serotype III isolates contained ST17 (94.2%), ST19 (2.9%), and ST650 (2.9%). CONCLUSION: Serotype distribution, antimicrobial susceptibility, and sequence type characterization in Asia and in other global regions may contribute to improve the prevention and treatment of neonatal GBS infections.

Dynamics of serotype 14 Streptococcus pneumoniae population causing acute respiratory infections among children in China (1997-2012).

BACKGROUND: In the last decade, the Streptococcus pneumoniae population has changed, mainly due to the abuse of antibiotics. The aim of this study was to determine the genetic structure of 144 S. pneumonia serotype 14 isolates collected from children with acute respiratory infections during 1997-2012 in China. METHODS: All isolated pneumococci were tested for their sensitivity to 11 kinds of antibiotics with the E-test method or disc diffusion. The macrolides resistance genes ermB and mefA, as well as the sulfamethoxazole-trimethoprim resistance gene dihydrofolate reductase (DHFR) were detected by polymerase chain reaction (PCR). The sequence types (STs) were analyzed with multilocus sequence typing (MLST). RESULTS: From 1997 to 2012, the percentage of serotype 14 S. pneumonia isolates in the whole isolates increased. All of the 144 serotype 14 S. pneumonia isolates were susceptible to amoxicillin-clavulanic acid, vancomycin and levofloxacin. No penicillin resistant isolate was found, and the intermediate rate was as low as 0.7 %. Erythromycin resistance was confirmed among 143 isolates. The ermB gene was determined in all erythromycin resistant isolates, and the mefA gene was positive additionally in 13 of them. The non-susceptibility rate to the tested cephalosporins increased from 1997-2012. All trimethoprim-resistant isolates contained the Ile100-Leu mutation. Overall, 30 STs were identified, among which ST876 was the most prevalent, followed by ST875. During the study period, the percentage of CC876 increased from 0 % in 1997-2000 to 96.4 % in 2010-2012, whereas CC875 decreased from 84.2 to 0 %. CC876 showed higher non-susceptibility rates to ß-lactam antibiotics than CC875. CONCLUSION: The percentage of serotype 14 S. pneumonia isolates increased over time in China. The increase of resistance to ß-lactam antibiotics in this serotype isolates was associated with the spread of CC876.

Serotypes, antibiotic susceptibilities, and multi-locus sequence type profiles of Streptococcus agalactiae isolates circulating in Beijing, China.

BACKGROUND: To investigate the serotypes, antibiotic susceptibilities, and multi-locus sequence type (MLST) profiles of Streptococcus agalactiae (S. agalactiae) in Beijing to provide references for the prevention and treatment of S. agalactiae infections. METHODS: All isolates were identified using the CAMP test and the latex-agglutination assay and serotyped using a Strep-B-Latex kit, after which they were assessed for antibiotic susceptibility, macrolide-resistance genes, and MLST profiles. RESULTS: In total, 56 S. agalactiae isolates were identified in 863 pregnant women (6.5%). Serotypes Ia, Ib, II, III, and V were identified, among which types III (32.1%), Ia (17.9%), Ib (16.1%), and V (14.3%) were the predominant serotypes. All isolates were susceptible to penicillin and ceftriaxone. The nonsusceptiblity rates measured for erythromycin, clarithromycin, azithromycin, telithromycin, clindamycin, tetracycline, and levofloxacin were 85.7%, 92.9%, 98.2%, 30.4%, 73.2%, 91%, and 39.3%, respectively. We identified 14 sequence types (STs) for the 56 isolates, among which ST19 (30.4%) was predominant. The rate of fluoroquinolone resistance was higher in serotype III than in the other serotypes. Among the 44 erythromycin-resistant isolates, 32 (72.7%) carried ermB. CONCLUSION: S. agalactiae isolates of the serotypes Ia, Ib, III, and V are common in Beijing. Among the S. agalactiae isolates, the macrolide and clindamycin resistance rates are extremely high. Most of the erythromycin-resistant isolates carry ermB.

Nasopharyngeal carriage and antimicrobial susceptibility of Haemophilus influenzae among children younger than 5 years of age in Beijing, China.

BACKGROUND: Haemophilus influenzae is one of the main pathogens that cause community-acquired respiratory infections in children. Our previous study showed that H. influenzae is the second most common pathogen causing pneumonia and accounts for 30-50% of bacterial meningitis among Chinese children. H. influenzae carriage in children and its resistance to commonly used antimicrobials varies widely both geographically and over time. RESULTS: Surveys of the nasopharyngeal carriage of H. influenzae in children younger than 5 years of age with acute respiratory tract infection (ARI) were conducted in Beijing Children's Hospital, China in 2000, 2002, 2010, and 2012. The overall annual carriage rates of H. influenzae among children younger than 5 years of age with ARI were 35.5%, 20.6%, 14.4%, and 18.7%, and the percentages of H. influenzae isolates producing ß-lactamase were 4%, 13%, 27.1%, and 31%, respectively. The percentages of susceptibility to ampicillin progressively decreased from 96% (2000) to 87% (2002) to 63% (2010) to 61% (2012). All of the ampicillin-resistant isolates were found to be beta-lactamase producers. The susceptibility to tetracycline increased from 54% (2000) to 60% (2002) to 91.5% (2010) to 94.5% (2012). No statistically significant differences were observed in the susceptibility to cefaclor, cefuroxime, sulfamethoxazole, and chloramphenicol. Amoxicillin/clavulanic acid and ceftriaxone were the most effective antimicrobials for the isolates of H. influenzae across the 10-year period. CONCLUSIONS: This report on the H. influenzae carriage rates in children and the susceptibility of these bacteria to commonly used antibiotics showed that H. influenzae carriage decreased from 2000 to 2012. Additionally, the percentage of ß-lactamase-producing isolates increased while their susceptibility to ampicillin progressively decreased during this time. These results indicate that the appropriate empirical antimicrobial therapy should be changed for pediatric patients in China.

Clinical and molecular characteristics of community-acquired methicillin-resistant Staphylococcus aureus infections in Chinese neonates.

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.

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.

[Nasopharyngeal carriage rate, antimicrobial resistance and serotype distribution of Streptococcus pneumoniae among children with upper respiratory infection].

OBJECTIVE: To investigate nasopharyngeal carriage rate, antimicrobial resistance and serotype distribution of Streptococcus pneumoniae among children with upper respiratory infection. METHODS: Nasopharygeal swabs were collected from children with upper respiratory infection visiting the outpatient department of Beijing Children's Hospital between March 2013 and February 2014. The antibiotic susceptibility was tested by Etest method, and the serotype was determined by Quellung reaction. RESULTS: The nasopharyngeal carriage rate for Streptococcus pneumoniae was 23.8% (699/2 941). One hundred isolates were randomly chosen for antimicrobial susceptiblity test and serotyping. Up to 98.0% isolates were susceptible to parenteral penicillin. The susceptible rate against oral penicillin, however, was 33.0%. The non-susceptible rate to erythromycin and azithromycin was 97.0%. The multi-drug resistance rate was up to 86.0%. The common serotypes were 6A(12.0%), 19F(12.0%), 6B(10.0%), 23F(9.0%) and 14(8.0%). The coverage rates of 7-, 10- and 13-valent pneumococcal conjugate vaccine were 41.0%, 42.0% and 59.0% respectively. CONCLUSIONS: About 25% of children with upper respiratory infection are nasopharyngeal colonized by Streptococcus pneumoniae. The isolates show a high antimicrobial resistance. The 13-valent pneumococcal conjugate vaccine covers about 60.0% of the isolates.

Population biology of 225 serogroup 6 Streptococcus pneumoniae isolates collected in China.

BACKGROUND: In this study, we defined the population biology of serogroup 6 Streptococcus pneumoniae collected in China and their antibiotic resistance profiles. METHODS: The serotypes of 225 S. pneumoniae strains isolated between 1997 and 2011 were identified with the Quellung reaction and serotype-specific PCR. All isolated pneumococci were tested for their sensitivity to 11 kinds of antibiotics with the E-test method or disc diffusion. The sequence types (STs) were analyzed with multilocus sequence typing (MLST). RESULTS: The frequencies of serotypes and subtypes 6A, 6B-I, 6B-II, 6C, and 6D among the 225 isolates were 46.7% (105/225), 19.6% (44/225), 25.8% (58/225), 6.2% (14/225), and 1.8% (4/225), respectively. Serotype 6E was not found in the serotype 6A isolates, and neither serotype 6F nor 6G was identified in any isolate. MLST analysis revealed 58 STs. The most common STs were ST982 (23.1%), ST90 (14.7%), ST4542 (7.6%), and ST2912 (4.9%). The rates of clonal complex 90 (CC90) and CC386 among the oral-penicillin-nonsusceptible isolates decreased over the years, whereas the rates of CC855 and CC3173 increased. The four CCs had similar penicillin MIC distributions, with a maximum MIC of 2 µg/ml. CONCLUSIONS: This study identified the serotypes/subtypes and CCs/STs of group 6 S. pneumoniae present in China. No salient antibiotic-resistant clones were isolated among the serogroup 6 S. pneumoniae.

Comparative analysis of the virulence characteristics of epidemic methicillin-resistant Staphylococcus aureus (MRSA) strains isolated from Chinese children: ST59 MRSA highly expresses core gene-encoded toxin.

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.

Molecular and clinical characteristics of clonal complex 59 methicillin-resistant Staphylococcus aureus infections in Mainland China.

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.

Serotype distribution and antimicrobial resistance of Streptococcus pneumoniae isolates causing invasive diseases from Shenzhen Children's Hospital.

OBJECTIVE: To provide guidance for clinical disease prevention and treatment, this study examined the epidemiology, antibiotic susceptibility, and serotype distribution of Streptococcus pneumoniae (S. pneumoniae) associated with invasive pneumococcal diseases (IPDs) among children less than 14 years of age in Shenzhen, China. MATERIALS AND METHODS: All the clinical strains were isolated from children less than 14 years old from January 2009 to August 2012. The serotypes and antibiotic resistance of strains of S. pneumoniae were determined using the capsular swelling method and the E-test. RESULTS: A total of 89 strains were isolated and 87 isolates were included. The five prevailing serotypes were 19F (28.7%), 14 (16.1%), 23F (11.5%), 19A (9.2%) and 6B (6.9%). The most common sequence types (ST) were ST271 (21.8%), ST876 (18.4%), ST320 (8.0%) and ST81 (6.9%) which were mainly related to 19F, 14, 19A and 23F, respectively. The potential coverage by 7-, 10-, and 13-valent pneumococcal conjugate vaccine were 77.0%, 77.0%, and 89.7%, respectively. Among the 87 isolates investigated, 11.5% were resistant to penicillin, and for meningitis isolates, the resistance rate was 100%. Multi-drug resistance (MDR) was exhibited by 49 (56.3%) isolates. Eighty-four isolates were resistance to erythromycin, among which, 56 (66.7%) carried the ermB gene alone and 28 (33.3%) expressed both the ermB and mefA/E genes. CONCLUSIONS: The potential coverage of PCV13 is higher than PCV7 and PCV10 because high rates of serotypes 19A and 6A in Shenzhen. The clinical treatment of IPD needs a higher drug concentration of antibiotics. Continued surveillance of the antimicrobial susceptibility and serotypes distribution of IPD isolates may be necessary.

Characterization of erythromycin-resistant Streptococcus pneumoniae isolates causing invasive diseases in Chinese children.

BACKGROUND: Erythromycin-resistant Streptococcus pneumoniae isolates that causing invasive pneumococcal diseases (IPD) in Chinese children remain uncharacterized. This study aims to identify the resistance genes associated with erythromycin resistance and to determine the genetic relationships of IPD isolates in Chinese children. METHODS: A total of 171 S. pneumoniae strains were isolated from 11 medical centers in China from 2006 to 2008. All the isolates were characterized via serotyping and antibiotic susceptibility determination. The erythromycin-resistant isolates were further characterized via ermB and mefA gene detection, multi-locus sequence typing analysis, and pulsed-field gel electrophoresis. RESULTS: A total of 164 (95.9%) isolates showed resistance to erythromycin, of which 162 strains with high high-level resistance (MIC ≥ 256 µg/ml). A total of 104 (63.4%) isolates carry the ermB gene alone, whereas 59 (36.0%) harbor both ermB and mefA genes. Of the 59 strains, 54 were of serotypes 19A and 19F and were identified as highly clonal and related to the Taiwan(19F)-14 clone. CONCLUSIONS: The erythromycin resistance rate in IPD isolates is significantly high and is predominantly mediated by the ermB gene. Isolates that carry both ermB and mefA genes are predominantly of serotypes 19A and 19F.

Molecular characteristics of erythromycin-resistant Streptococcus pneumoniae from pediatric patients younger than five years in Beijing, 2010.

BACKGROUND: Streptococcus pneumoniae is the main pathogen that causes respiratory infections in children younger than five years. The increasing incidence of macrolide- and tetracycline-resistant pneumococci among children has been a serious problem in China for many years. The molecular characteristics of erythromycin-resistant pneumococcal isolates that were collected from pediatric patients younger than five years in Beijing in 2010 were analyzed in this study. RESULTS: A total of 140 pneumococcal isolates were collected. The resistance rates of all isolates to erythromycin and tetracycline were 96.4% and 79.3%, respectively. Of the 135 erythromycin-resistant pneumococci, 91.1% were non-susceptible to tetracycline. In addition, 30.4% of the erythromycin-resistant isolates expressed both the ermB and mef genes, whereas 69.6% expressed the ermB gene but not the mef gene. Up to 98.5% of the resistant isolates exhibited the cMLSB phenotype, and Tn6002 was the most common transposon present in approximately 56.3% of the resistant isolates, followed by Tn2010, with a proportion of 28.9%. The dominant sequence types (STs) in all erythromycin-resistant S. pneumoniae were ST271 (11.9%), ST81 (8.9%), ST876 (8.9%), and ST320 (6.7%), whereas the prevailing serotypes were 19F (19.3%), 23F (9.6%), 14 (9.6%), 15 (8.9%), and 6A (7.4%). The 7-valent pneumococcal conjugate vaccine (PCV7) and 13-valent pneumococcal conjugate vaccine (PCV13) coverage of the erythromycin-resistant pneumococci among the children younger than five years were 45.2% and 62.2%, respectively. ST320 and serotype 19A pneumococci were common in children aged 0 to 2 years. CC271 was the most frequent clonal complex (CC), which accounts for 24.4% of all erythromycin-resistant isolates. CONCLUSIONS: The non-invasive S. pneumoniae in children younger than five years in Beijing presented high and significant resistance rates to erythromycin and tetracycline. The expressions of ermB and tetM genes were the main factors that influence pneumococcal resistance to erythromycin and tetracycline, respectively. Majority of the erythromycin-resistant non-invasive isolates exhibited the cMLSB phenotype and carried the ermB, tetM, xis, and int genes, suggesting the spread of the transposons of the Tn916 family. PCV13 provided higher serotype coverage in the childhood pneumococcal diseases caused by the erythromycin-resistant isolates better than PCV7. Further long-term surveys are required to monitor the molecular characteristics of the erythromycin-resistant S. pneumoniae in children.

Multidrug-resistant clones of community-associated meticillin-resistant Staphylococcus aureus isolated from Chinese children and the resistance genes to clindamycin and mupirocin.

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-ß-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-ß-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.

Panton-Valentine leukocidin gene sequence variation and phage in methicillin-resistant and methicillin-susceptible Staphylococcus aureus from children in mainland China.

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.

Epidemiological and molecular characteristics of clinical isolates of Streptococcus pyogenes collected between 2005 and 2008 from Chinese children.

The aim of this study was to explore the epidemiological and molecular characteristics of Streptococcus pyogenes in children from different cities in mainland China who were diagnosed with scarlet fever, impetigo and pharyngitis, as well as to detect asymptomatic carriers, between 2005 and 2008, and to compare the results with isolates from rural Chinese children with acute glomerulonephritis in 2005 and in the 1990s. Susceptibility tests to determine MICs and analysis of the presence of erythromycin-resistant genes (mefA, ermB and ermA) and emm gene typing were performed on 466 S. pyogenes isolates from Beijing, Shanghai, Chongqing and Shenzhen. Superantigen genes (speA and speC) were examined by performing PCR on isolates with the most prevalent emm genotype. All isolates were sensitive to penicillin, cefradine and ofloxacin. The highest rate of resistance was against clarithromycin (98.1 %), followed by erythromycin (97.6 %), azithromycin and clindamycin (both 97.2 %), and tetracycline (94.0 %). Among the 466 isolates, 421 (90.3 %) harboured the ermB gene, 145 (31.1 %) were speA-positive and 273 (58.6 %) were speC-positive. The speA gene was common in emm1.0 (88.8 %) and emm6.5 (83.3 %) genotypes. The speC gene was frequently observed in emm4.0 (90.0 %), emm12.0 (69.6 %), emm18.0 (66.7 %), emm22.0 (75.9 %) and emm80.0 (80.0 %) genotypes. The most prevalent emm genotypes in mainland China in recent years were emm1.0 and emm12.0. All isolates remained sensitive to ß-lactams and quinolone.

Susceptibility to and resistance determinants of fusidic acid in Staphylococcus aureus isolated from Chinese children with skin and soft tissue infections.

This study aims to determine the resistance rates and determinants of fusidic acid among Staphylococcus aureus isolates collected from Chinese pediatric patients with skin and soft tissue infections (SSTIs). Between 2008 and 2009, a total of 186 clinical S. aureus isolates were collected from the pediatric patients with SSTIs, abscess (44.6%) was the most common SSTI in children 0-16 years old. Four clinical isolates (4/186, 2.2%) were resistant to fusidic acid. Two of these isolates were methicillin-resistant S. aureus (MRSA) that carry the fusC gene. The other two isolates were methicillin-sensitive S. aureus (MSSA) that carry the fusB gene. In the two fusB-positive clinical isolates, the fusB gene was located in a transposon-like element that has 99% identity with a pUB101 fragment from S. aureus. The four fusidic acid-resistant clinical isolates were ST1-MRSA-SCCmecV-t127, ST93-MRSA-SCCmecIII-t202, ST680-MSSA-t5415, and ST680-MSSA-t377. The fusidic acid resistance rate of S. aureus isolated from Chinese pediatric patients with SSTIs was low, and the genes fusB and fusC were the main resistance determinants. The transposon-like element that contains the fusB gene might participate in the transmission of fusidic acid resistance genes. This is the first report regarding the emergence of fusidic acid-resistant clinical S. aureus isolates in mainland China.

Molecular characterization of group G Streptococcus dysgalactiae subsp. equisimilis recovered from patients and healthy people in China.

Beta-Hemolytic group G streptococci cause a considerable invasive disease burden and sometimes disease outbreaks. Little is known about the critical epidemiologic parameter of genetic relatedness between isolates. We determined the emm types of 65 Streptococcus dysgalactiae subsp. equisimilis isolates. We formulated multilocus sequence typing (MLST) primers with 6 of the 7 loci corresponding to the Streptococcus pyogenes MLST scheme. We performed MLST with 69 S. dysgalactiae subsp. equisimilis isolates to represent each emm type identified. These strains were further analyzed by pulsed-field gel electrophoresis (PFGE) typing. Sixteen emm types were observed. Eighteen unique combinations of allelic profiles (sequence types [STs]) were obtained with 12 profiles each accounting for multiple isolates. Forty-one MLST STs were observed. Analysis of the PFGE patterns generated revealed 10 clones. Over 80% of the isolates were distributed in 3 large clones. Isolates within 16 redundantly represented S. dysgalactiae subsp. equisimilis emm types shared identical or nearly identical STs and subtypes of PFGE, demonstrating concordance between the emm type and genetic relatedness. It is conceivable that some particular characteristics in the genomes of these strains are responsible for their predominance in different regions.

Serotype distribution and antibiotic resistance of 140 pneumococcal isolates from pediatric patients with upper respiratory infections in Beijing, 2010.

In the present study, the serotype distribution and antibiotic resistance of S. pneumoniae from pediatric patients with upper respiratory infections in Beijing, 2010 were described. 140 pneumococcal isolates were obtained, and the prevailing five serotypes were 19F (18.6%), 23F (9.3%), 14 (9.3%), 15 (9.3%), and 6A (7.1%). The vaccine coverage of PCV7, PCV10, and PCV13 were 43.6%, 43.6%, and 60.0%, respectively. According to the CLSI 2010 criteria, 99.3% of the S. pneumoniae isolates were susceptible to penicillin. The resistance rates to erythromycin and azithromycin were 96.4% and 97.1%, respectively. Meanwhile, 64.3% (90/140) of all pneumococcal isolates were multidrug-resistant S. pneumoniae (MDRSP). PCV13 covered 68.9% (62/90) of MDRSP strains, whereas it was 47.8% (43/90) for PCV7. ErmB was the dominant macrolide-resistance gene, whereas 30.4% pneumococcal isolates expressed both ermB and mefA. No isolate expressed ermTR. The potential coverage of PCV13 is higher than PCV7 and PCV10 because high rates of serotypes 6A and 19A, and the conjugate vaccines could prevent the spread of MDRSP. S. pneumoniae is still sensitive to penicillin. The resistance rate of S. pneumoniae to macrolides is high and ermB is the dominant macrolide-resistance gene in China, so continued surveillance of the antimicrobial susceptibility of S. pneumoniae may be necessary.