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.

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.

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.

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.

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.

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.

Prevalence and mechanism of resistance to antimicrobial agents in group G streptococcal isolates from China.

Eighty group G streptococcal stains were collected from Chinese children. Susceptibility testing was done by a double-dilution and a disk diffusion method. PCR was used to test drug-resistant genes, and the χ(2) test and definite probability methods were used to test for statistically significant differences among the three groups. Thirty-four isolates (42.5%) showed resistance to erythromycin. There are differences between the resistance characteristics of group G streptococci from different regions of China.

Serotype distribution and antimicrobial resistance of Streptococcus pneumoniae isolates that cause invasive disease among Chinese children.

A total of 171 Streptococcus pneumoniae isolates causing invasive disease were isolated from Chinese children. The serotype distribution and antimicrobial resistance were tested. The results suggested that the 7-valent pneumococcal conjugate vaccine has a preventive effect among children and that there should be long-term surveillance for serotype 19A.

Antibiotic resistance and molecular analysis of Streptococcus pyogenes isolated from healthy schoolchildren in China.

Streptococcus pyogenes are highly prevalent bacterial pathogens, especially in school-aged children. However, the characteristics of asymptomatic carriers vary geographically in different countries. We aimed to investigate S. pyogenes isolated from healthy schoolchildren in China. From 2007 to 2008, a total of 94 S. pyogenes isolates were obtained from healthy schoolchildren in Beijing and Chongqing, China. Antimicrobial susceptibility testing, determination of macrolide resistance genes (ermB, ermA and mefA), emm genotyping, pulsed-field gel electrophoresis (PFGE), and multilocus sequence typing (MLST) were performed. The resistance rate to macrolides was 96.8% and to tetracycline was 92.6%. All macrolide-resistant isolates exhibited constitutive resistance; 77 isolates (84.6%) had the ermB gene, while 14 isolates (15.4%) had the ermA gene. Among the macrolide-resistant isolates, the most frequent emm type was emm12 (51.6%), followed by emm22 (14.3%) and ST1815 (8.8%). PFGE analysis revealed 12 different patterns, with a given pattern having the same sequence type (ST) by MLST and the same emm type. In conclusion, the rate of macrolide resistance to S. pyogenes is currently very high in China. This is due primarily to the dissemination of a limited number of clones.

Genetic analysis of group A streptococcus isolates recovered during acute glomerulonephritis outbreaks in Guizhou Province of China.

In this study, 68 group A streptococcus (GAS) isolates associated with two outbreaks of acute glomerulonephritis (AGN) in China were analyzed by emm typing. A total of 11 different emm types were identified. Analysis of emm type distribution suggested that AGN outbreaks in two counties were caused by emm60.1- and emm63.0-type GAS. These two types were further characterized by pulsed-field gel electrophoresis, multilocus sequence typing, sof sequence typing, and PCR-based identification of streptococcal pyrogenic exotoxin A, B, and C (speA, speB, and speC) genes. In antimicrobial susceptibility tests, all outbreak strains were resistant to erythromycin and tetracycline, and the rates of resistance of nonoutbreak strains to the two antibiotics were 63.6% and 90.9%. This study is also the first to report a nephritogenic M63 GAS strain.

Drug utilisation 90% (DU90%) profiles of antibiotics in five Chinese children's hospitals (2002-2006).

This study surveyed the pattern of inpatient antibiotic use in five Chinese children's hospitals between 2002 and 2006, focusing on the antibiotics accounting for 90% of the volume utilised as well as the level of adherence to guidelines. The Anatomical Therapeutical Chemical Classification/Defined Daily Doses (ATC/DDD) and the drug utilisation 90% (DU90%) methodologies were used. In October 2004, national antibiotic guidelines were issued that divided antibiotics into non-restricted, restricted and special use grades. In five children's hospitals, a total of 56 different systemic antibiotics were used during the study period. Antibiotics that could be injected accounted for 59.0-99.8%. beta-Lactam antibacterials (ATC codes J01C and J01D) were the most used subgroups. The numbers of antimicrobial agents and non-restricted antibiotics within the DU90% segment were 11-20 and 5-9, respectively. The proportion of non-restricted antibiotic consumption was ca. 40% in 2006 in four hospitals, which varied among hospitals during the period 2002-2005. There was considerable variation both in the pattern and amount of antibiotics used in the five hospitals, with amoxicillin/clavulanic acid, cefuroxime and cefazolin being the most commonly used substances. We also observed a decrease in the ranks of some restricted and special use antibiotics after the guidelines were issued in one hospital. The DU90% profiles were proven to be useful in studying the pattern of antibiotic use in hospitals. Finally, the study observed the effectiveness of guidelines for antibiotic use in some hospitals, although injectable antibiotics were widely used in children's hospitals in China.

Antibiotic use in five children's hospitals during 2002-2006: the impact of antibiotic guidelines issued by the Chinese Ministry of Health.

PURPOSE: To investigate the pattern of antibiotic use in five Chinese children's hospitals from 2002 to 2006. To see if the Guidelines to encourage rational use of antibiotics issued by the Ministry of Health in October 2004 have any impact on the use. METHODS: The Anatomical Therapeutic Chemical Classification/Defined Daily Doses (ATC/DDD) methodology was used. Aggregate data on antibiotic use (ATC code-J01) were expressed in numbers of DDD/100 bed-days for inpatients. RESULTS: Total 56 different substances of systemic antibiotics were used. The overall consumption of antibiotic drugs was 68.2, 58.4, 65.8, 65.6 and 49.9 DDD/100 bed-days for the years 2002-2006, respectively. The top antibiotics used were third-generation cephalosporins. There was considerable variation in both type and amount of antibiotics used in the five hospitals. In 2002, some hospitals had twice the antibiotic use compared to others. While the overall antibiotic use in 2005 was largely unchanged compared with previous years, by 2006 antibiotic use had decreased by 22.6% and the variation in use between hospitals was also reduced. CONCLUSIONS: The ATC/DDD methodology proved useful for studying overall antibiotic usage in children's hospitals. The decline in antibiotic usage found in 2006 (and the reduced variation between hospitals) may be attributed to the impact of the Ministry of Health guidelines which took some time to be promulgated to individual staff members. Further research will focus on compliance of antibiotic use in these five hospitals with particular guideline recommendations for specific clinical problems such as bacterial resistance and surgical antibiotic prophylaxis.

Characterization of multidrug-resistant and metallo-beta-lactamase-producing Pseudomonas aeruginosa isolates from a paediatric clinic in China.

BACKGROUND: In the present study, we characterized multidrug-resistant Pseudomonas aeruginosa (MDRP) clinical isolates from a paediatric facility and investigated the types and features of the metallo-beta-lactamases (MBLs) produced by carbapenem-resistant strains. METHODS: Four hundred and ninety-eight strains of Pseudomonas aeruginosa were isolated from patients at Beijing Children's Hospital between January 2005 and December 2006. The minimal inhibition concentrations (MICs) of the strains for 13 antibiotics were measured. A combination of the E test and PCR amplification/DNA sequencing was used to define the carbapenem-resistant strains. RESULTS: We found that 24.1% (120/498) of the isolates were MDRP. The frequencies of resistance to imipenem and meropenem were 34.2% and 35.8%, respectively, and the MIC50 and MIC90 values for the two antibiotics were identical at 4 microg/ml and 32 microg/ml, respectively. The detection rate for carbapenem resistance was 49.2% (59/120). Among the 59 carbapenem-resistant Pseudomonas aeruginosa strains, 39 (66.1%) were positive for the MBL genotype; 35 (89.7%) strains carried the bla(IMP) gene and 4 (10.3%) strains carried the bla(VIM) gene. Neither bla(SPM) nor bla(GIM) was amplified from any of the 59 isolates. DNA sequencing revealed that IMP-1 was present in 35 IMP-producing isolates and VIM-2 was detected in four VIM-producing isolates. CONCLUSIONS: These MDRP isolates exhibited high frequencies of resistance to carbapenems among clinical isolates from a paediatric facility in Beijing, China. The production of MBL appears to be an important mechanism for carbapenem resistance in Pseudomonas aeruginosa.

[Surveillance of antibiotic resistance of Streptococcus pneumoniae isolated from hospitalized patients with pneumonia in four children's hospitals in China].

OBJECTIVE: To investigate the antimicrobial resistance of Streptococcus pneumoniae (S.pneumoniae) isolated from Chinese children with pneumonia. METHODS: Hypopharyngeal aspirate specimens were collected from hospitalized children with pneumonia who were admitted to the children's hospital located in Beijing, Shanghai, Guangzhou or Shanghai from February 16, 2006 to February 16, 2007. The minimum inhibitory concentration (MIC) of S.pneumoniae isolates against penicillin, amoxicillin, cefuroxime (sodium), ceftriaxone, erythromycin, vancomycin, ofloxacin and imipenem was determined by E-test method. RESULTS: A total of 279 S.pneumoniae isolates were obtained. Eighty-six percent of the isolates were not susceptive to penicillin, and 23.3% was resistant to penicillin. The rate of susceptibility of the isolates to amoxicillin was 92.1%, and to cefuroxime and ceftriaxone was 19.0% and 75.3%, respectively. The isolates also showed a high susceptibility to vancomycin (99.6%) and ofloxacin (97.8%). Seventeen point six percent of the isolates were not susceptive to imipenem, and most of those were intermediate. Almost of all isolates were resistant to erythromycin. There were some distinct regional differences in the susceptibility to antimicrobials tested except for erythromycin, vancomycin and ofloxacin. CONCLUSIONS: The S.pneumoniae isolates from Chinese children with pneumonia were susceptive to amoxicillin, vancomycin and ofloxacin, but were not susceptive or resistant to penicillin, cefuroxime and erythromycin. The isolates kept susceptibility to ceftriaxone and imipenem to a certain extent.

[Transfer of erythromycin-resistance among strains and species of bacteria: plasmid conjugation method in enterococcal isolates].

OBJECTIVE: To study if the resistance to macrolide in Enterococcus can be transferred between strains, and species of the same and different genera. METHODS: Agar dilution was used to screen 30 enterococcal isolates that were resistant to erythromycin. Conjugation was performed by filter mating method. The 30 donor bacteria included 13 strains of Enterococcus faecalis, 16 strains of E. faecium, and 1 strain of E. hirae. The recipient bacteria included 1 strain of E. faecalis sensitive to erythromycin and resistant to tetracycline, and 1 strain of Staphylococcus aureus with the MIC against erythromycin of 0.25 approximately 1 microg/ml. Polymerase chain reaction was used to test the existence of ermB gene and the tranposons Tn1545 and Tn917 in the enterococcal isolates before and after filter mating. RESULTS: The transfer rate between different strains and species of the same genus were all 100%. The MIC(50) and MIC(90) against erythromycin of 13 conjugates were both 512 microg/ml, and Tn1545 and Tn917 were found in the ermB gene of 12 conjugates. 17 conjugates were obtained from 16 strains of donor E. faecium and 1 strain of E. hirae with the MIC(50) and MIC(90) both of 512 microg/ml. The ermB gene was found in 16 of the 17 conjugates, and 11 of the 16 conjugates showed the existence of Tn1545 and Tn917, Tn1545 existed in the ermB gene of 4 conjugates, and Tn917 existed in the ermB gene of 1 conjugate. 30 conjugates of Staphylococcus aureus were obtained by plasmid conjugation and transfer with a transfer rate of 100% and the MIC(50) and MIC(90) both of 512 microg/ml. The ermB gene was found in 28 of the 30 conjugates. Both Tn1545 and Tn917 were found in the ermB gene of 23 of the 28 conjugates, Tn1545 was found in the ermB gene of 4 conjugates, and Tn917 was found in the ermB gene of 1 conjugate. CONCLUSION: The resistance to macrolide of Enterococcus, related with the existence of ermB gene and transposons Tn1545 and Tn917, can be transferred between strains and species of same and different genera.

[Carrier rate of Streptococcus pneumoniae and susceptibility thereof to antimicrobial drugs among children in China: a surveillance study in Beijing, Shanghai, and Guangzhou 2000-2002].

OBJECTIVE: To investigate the carrier rate of Streptococcus pneumoniae and the susceptibility of S. pneumoniae to 10 different antimicrobial drugs among children in China. METHODS: Nasopharageal swab specimens were collected from randomly selected 3578 out-patients with upper respiratory infection aged 1 month to 5 years in Beijing, Shanghai, and Guangzhou 2000-2002 so as to isolate S. pneumoniae. The susceptibility of these strains to erythromycin and beta-lactam antibiotics (penicillin, amoxicillin/clavulanic acid, cefaclor, cefuroxime and ceftriaxone) was determinated by E-test MIC method, and the susceptibility to chloramphenicol, tetracycline, sulfamethoxazole/trimethoprim and ciprofloxacin was determinated by disk diffusion method. RESULTS: A total of 892 strains of S. pneumoniae were isolate from the 3578 children with a carrier rate of 24.9% (9.0%-36.0%). 634 isolates of S. pneumoniae were tested to examine their susceptibility to chloramphenicol, 199 to ciprofloxacin, and 887 to the other 8 antimicrobial drugs. The insusceptibility rate of S. pneumoniae to penicillin was 39.9%, and the resistance rate was 6.4%. The resistance rate to cefaclor was 20.4%. The insusceptibility rate to cefuroxime was 19.0%. The susceptibility rate to amoxicillin/clavulanic acid was 98.5% and that to ceftriaxone was 97.2%. More than 80% of the isolates were resistant to erythromycin, tetracycline, and sulphamethoxazole/trimethoprim. Chloramphenicol resistance was less common (32.3%) than the resistance to other non-beta-lactam antibiotics, except for ciprofloxacin to which the resistance rate was 2.0%. The national insusceptibility rates for beta-lactam antibiotics did not vary significantly during the three years with the widest varying range of 5.1% for penicillin (38.1%-43.2%). Each of the three cities had their different varying patterns of antimicrobial susceptibility, especially for beta-lactam antibiotics. Multi-drug resistance was common (88.7%). Strains of S. pneumoniae insusceptible to penicillin were significantly more common than those susceptible to penicillin (99.1% vs. 78.8%, chi(2) = 50.36, P < 0.001), and strains of S. pneumoniae insusceptible to erythromycin were significantly more common than those susceptible to erythromycin too (95.8% vs. 17.1%, chi(2) = 360.26, P < 0.001). CONCLUSION: Antimicrobial resistant S. pneumoniae has already become a serious problem in China. Ongoing surveillance study on the antimicrobial resistance of S. pneumoniae is necessary for appropriate antimicrobial use in clinical work and modification of medical strategies for people's health.

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.

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.

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.