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 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.

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.

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.

Molecular epidemiology of serotype 19A Streptococcus pneumoniae isolated from children in Beijing, 1997-2006.

BACKGROUND: Despite the prevalence of Streptococcus pneumoniae serotype 19A, the molecular characteristics of this serotype are yet to be fully elucidated. The aim of this study was therefore to determine the homology of the serotype 19A in China. METHODS: Pulsed-field gel electrophoresis and multilocus sequence typing were done to these forty-nine serotype 19A isolates to investigate the relationship between the strains prevalent in Beijing and other regions. RESULTS: From 1997 to 2006, the percentage of serotype 19A isolates increased. The susceptibility rate to penicillin and amoxicillin decreased and the resistance rate to cefuroxime increased. ST320 was the most prevalent ST, followed by ST3546. There were six new STs identified in our study. The serotype 19A strains were classified into six different pulsed-field gel electrophoresis (PFGE) patterns. ST320, which was associated with two different PFGE patterns (A and D), accounted for 32 isolates, and ST3546, which was associated with two PFGE patterns (B and E), accounted for eight isolates. CONCLUSIONS: From 2003 onwards, ST320 was the most common ST and the rate of resistance to cefuroxime increased significantly. Further long-term surveys of Streptococcus pneumoniae serotype 19A are required to monitor ST prevalence and antimicrobial resistance in this important human pathogen.

Type distribution of serogroup 6 Streptococcus pneumoniae and molecular epidemiology of newly identified serotypes 6C and 6D in China.

The recently determined serotypes 6C and 6D Streptococcus pneumoniae, as well as subtypes 6B-I and 6B-II, were not reported in China. Among the 171 invasive isolates, 19 were identified as serogroup 6. There were equal distribution (42.1%) of 6B-I and 6B-II, 15.8% of 6A and lack of 6C and 6D. Among 1662 noninvasive isolates, 210 were identified as serogroup 6. The rates of types 6A, 6B-I, 6B-II, 6C, and 6D were 42.4%, 21.0%, 29.1%, 4.8%, and 2.9%, respectively. Subtype 6B-II was more resistant to antibiotics than others. The main sequence types (STs) of serotype 6C and 6D isolates were ST2912 and ST982, respectively. These results suggested that all recognized types of serogroup 6 can be found in China and that subtype 6B-II was more drug resistant. The epidemic STs of serotype 6C and 6D did not show genetic association with the STs spreading in other countries.

Pneumococcal serotype distribution and antimicrobial resistance in Chinese children hospitalized for pneumonia.

A prospective study was performed to determine serotype distribution and antimicrobial resistance in Streptococcus pneumoniae (S. pneumoniae) from Chinese children <5 years old meeting pneumonia criteria. A total of 3865 children were enrolled and 338 S. pneumoniae isolates were obtained. The most frequent serotypes were 19F (55.6%), 19A (13.9%), 23F (10.1%), 6B (4.7%), and 14 (3.6%). The 7-, 10- and 13-valent conjugate vaccines, respectively, covered 76.3%, 76.9%, and 92.3% of isolates. Out of the isolates, six (1.8%) were penicillin resistant. All except 1 of the isolates were resistant to erythromycin. Serotype 19A showed the highest drug resistance. The use of PCV7 has the potential to prevent a substantial number of pneumococcal infections. However, PCV13 is likely to prevent more episodes of pneumococcal disease in China because of the high rates of 19A.

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.

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.

[Serotype distribution and resistance to beta-lactams of Streptococcus pneumoniae isolated from children in Beijing, Shanghai and Guangzhou, 2000 - 2002].

OBJECTIVE: The present study was designed to investigate the situation of serotype distribution and beta-lactam antibiotics resistance of Streptococcus pneumoniae (S. pneumoniae) isolated from Chinese children, and to further understand the significance of vaccine for preventing infection caused by the bactria and controlling the resistance to antibiotics. METHODS: Nasopharageal swab specimens were collected from randomly selected less than 5-year-old out-patients with upper respiratory infection in Beijing, Shanghai and Guangzhou, 2000 - 2002. Capsular typing was performed by the Quellung reaction tested using a simplified chessboard system for typing of S. pneumoniae. The coverage rate of the 7-valent pneumococcal conjugate vaccine (4, 6B, 9V, 14, 18C, 19F and 23F) was calculated. Antibiotic susceptibility was determined by E-test MIC method for beta-lactam antibiotics (penicillin, amoxicillin/clavulanic acid, cefaclor, cefuroxime and ceftriaxone). RESULTS: Totally 625 pneumococcal strains were typed. Serogroup 19, including 121 strains, was the most frequent serogroup observed (19.4%). Other frequently observed serotypes/serogroups in decreasing order of frequency were serotype/serogroups 23 (15.4%), 6 (13.3%), 14 (6.6%) and 15 (4.3%). Of all these isolates, about 57.6% (360/625) were in the 7-valent conjugate vaccine. Only 1, 6 and 12 strains were serotypes/serogroups 4, 9 and 18, respectively. The coverage rate for the 7-valent vaccine of penicillin nonsusceptible S. pneumoniae (PNSP) was higher than penicillin susceptible S. pneumoniae (PSSP) (73.2% and 46.1%). Serogroups 19 and 23, without other serotypes/serogroups, were significantly associated with PNSP (serogroup 19 accounted for 29.1% of PNSP and 12.2% of PSSP; serogroup 23 accounted for 23.8% of PNSP to 9.2% of PSSP). Overall, 140 strains (22.4%) could not be typed by using the chessboard system, and 117 strains (18.7%) were identified as other 28 kinds of serotype/serogroup. The strains showed different resistance change for beta-lactam antibiotics according to different serotype/serogroup during the three years. CONCLUSIONS: Serotype/Serogroup 19, 23, 6, 14 and 15 were the common types among the pneumococcal strains isolated from Chinese children. Serogroups 19 and 23 were significantly associated with PNSP. The 7-valent pneumococcal conjugate vaccine could cover most of the islotes.

[Detection of group B streptococcus in the cases died of neonatal pneumonia].

OBJECTIVE: From the 1970s, group B streptococci (GBS) have been widely recognized as an important pathogen in neonatal infectious disease, and it emerged as the leading cause of neonatal morbidity and mortality in the Western world. However, there are few data on the prevalence of neonatal GBS infections in China. The aim of this retrospective study was to estimate whether GBS is an important pathogen in severe neonatal pneumonia, and to develop a method for detection of GBS infections in fatal neonatal pneumonia. METHODS: A total of 234 neonatal cases (0 - 28 days) died in Beijing Children's Hospital from 1953 to 2004 were enrolled in this study. They were divided into two groups. Two hundred cases diagnosed as neonatal pneumonia were assigned to study group and the remaining 34 cases died of neonatal hemolysis or surgical operation without any confirmed infectious diseases were designated as control group. Formalin-fixed, paraffin-embedded lung tissues were used as source for total genomic DNA extraction. PCR and Southern blot analyses were applied to detect GBS specific cfb gene target sequence. And the clinical data of these cases were reviewed as well. RESULTS: In the study group, 52 cases were detected positive for GBS DNA by PCR (26%), 130 cases were positive by Southern blot (65%). In the control group, 1 case was detected positive GBS DNA by PCR (3%), and 6 cases were positive by Southern blot (18%). The positive rate was significantly lower in the control group than that in the study group (PCR, chi(2) = 8.82, P < 0.01; Southern blot, chi(2) = 26.77, P < 0.01). The positive rate in the neonates younger than 7 days (early-onset) was significantly higher than that in neonates older than 7 days (late-onset) (PCR: 37% vs. 13%, chi(2) = 15.537, P < 0.01; Southern blot: 72% vs. 52%, chi(2) = 4.37, P < 0.05). In the positive early-onset cases, 39% of whom were born prematurely (29/74). Out of the 200 cases, 75 had complete clinical data. Neither blood nor lung culture for GBS was performed in any of these cases. But risk factors were identified for 35 cases, such as premature delivery, low birth weight, premature rupture of the membrane and abnormal amniotic fluid. GBS was positive in all these cases. Severe apnea appeared to be a common symptom and was present in most of the early-onset GBS-positive cases, while cough and wheezing were found in most of the late-onset GBS-positive cases. In the control group, one PCR positive case was suffered from malignant teratoma. The other 5 positive cases confirmed by Southern blot were diagnosed as kernicterus, hepatoma, aproctia complicating with cysti-urethral fistula, neonatal physio logical bleeding and aproctia complicated with archo-perineal fistula. CONCLUSION: Group B Streptococcus is an important pathogen in fatal neonatal pneumonia, especially in early-onset cases. southern blot may be a sensitive method to detect GBS infection in archival tissues. In the clinical work, more attention should be paid to the neonates with GBS risk factors. And GBS detection and prevention in neonates should be put into clinical practice.

[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.

[Molecular epidemiology of penicillin-nonsusceptible Streptococcus pneumoniae in Beijing, China, 2000-2002].

OBJECTIVE: To investigate the molecular epidemiology of the penicillin-nonsusceptible Streptococcus pneumoniae (PNSP) in Beijing, China. METHODS: The resistant profile of 63 PNSP strains isolated from children with upper respiratory infection in the outpatient department from 2000 to 2002 was analyzed. The isolates were compared by detecting restriction fragment length polymorphism (RFLP) of the penicillin-binding protein (PBP) genes pbp1a, pbp2b and pbp2x and by applying chromosomal macrorestriction patterns detected by pulsed-field gel electrophoresis (PFGE). RESULTS: Sixty-one (96.8%) out of the 63 PNSP strains were multidrug-resistant Streptococcus pneumoniae (Sp). Overall, 16 resistance profiles were found, 14 of which were multidrug resistant profiles. Seven (33.3%), 6 (24.0%) and 8 (47.1%) strains resistant to one of cephalosporins were respectively isolated in 2000, 2001 and 2002, indicating an increasing trend but without any statistical significance (chi(2) = 2.42, P > 0.05). The RFLP results showed 8, 9 and 18 genotypes of pbp1a, pbp2b and pbp2x, respectively. A total of 30 patterns were found according to the three pbps types. And clearly, the most common 5 patterns had main resistant profiles. In the mean time, 35 different PFGE types were elucidated and the 9 PFGE types, with each consisting of more than 2 strains, covered 59% (37/63) of all isolates. One of the 9 PFGE type included 2 strains, both possibly related to each other, but one of them was detected to be the same PFGE pattern with clones prevalent in Asia, Vietnam-19 serogroup, Singapore-19 serogroup, Taiwan-19 serogroup, and the other was the same as that in Korea-19 serogroup. CONCLUSION: Multidrug resistance is very common among PNSP isolates in Beijing. The spread of a few multidrug resistant clones is an important factor for the prevalence of PNSP. It deserves the concern that the resistant clones spread in Asia have been found in Beijing.

[Genotyping of ampicillin-resistant Haemophilus influenzae].

OBJECTIVE: Haemophilus (H.) influenzae is a gram-negative bacillus that is a common commensal organism of the human upper respiratory tract and an important cause of human diseases such as pneumonia, meningitis, septicemia, epiglottitis and cellulitis. Strains of H. influenzae are classified according to their capsular polysaccharide. There are six serotypes, designated as a through f. In addition, there are nonencapsulated strains. Although the type of infectious diseases caused by H. influenzae has changed considerably in recent years because of the widespread and routine immunization of children against type b H. influenzae (Hib), Hib remains an important pathogen. Ampicillin is the drug of choice for treating many infections caused by H. influenzae, but its usefulness has been compromised by the increasing prevalence of ampicillin-resistant strains. The continued monitoring of resistant strains by using genotyping methods may provide insights into the epidemiology of transmission. A molecular epidemiological study of ampicillin-resistant H. influenzae derived from nasopharyngeal swabs specimens of children less than 5 years of age with respiratory tract infection were investigated in this study. METHODS: A total of 899 isolates were collected from Beijing, Shanghai, and Guangzhou during 2000-2003. Susceptibility to ampicillin was determined by using E-test. Ampicillin-resistant H. influenzae strains were selected according to National Committee for Clinical Laboratory Standards (NCCLS) 2002 breakpoints. Nested PCR method with primers specific for bexA gene and b capsulate type-specific gene was established. Genotyping by pulsed-field gel electrophoresis (PFGE) and multiplex PCR assay was performed for all ampicillin-resistant H. influenzae strains. RESULTS: Seventy-four ampicillin-resistant H. influenzae strains were obtained. Two strains were positive by nested PCR, characterized as b genotype. The incidence of Hib in ampicillin-resistant H. influenzae strains was 2.7%; 38 genotypes were detected by PFGE. Detection of five types strains of clonal dissemination by PFGE accounted for 55.4% in all ampicillin-resistant H. influenzae strains. Among them eighteen H. influenzae strains belonged to one type, accounted for 24.3% in all ampicillin-resistant H. influenzae strains. Thirty one genotypes were identified by multiplex PCR assay for ampicillin-resistant H. influenzae. The identity ratio of PFGE and multiplex PCR was 63.5%. CONCLUSION: In Beijing, Shanghai and Guangzhou areas 55.4% of ampicillin-resistant H. influenzae strains had clonal dissemination during the 4 years.

[Study on Haemophilus influenzae type b: data from autopsy of community acquired pneumonia among children].

OBJECTIVE: To evaluate the status of Haemophilus influenza type b(Hib) on death cases of children from community-acquired pneumonia (CAP) and to estimate the value of direct in-situ polymerase chain reaction (ISPCR) on diagnosis of children CAP, pathogenically. METHODS: Ordinary PCR, Southern blot and direct ISPCR were applied and compared in detecting Hib in 100 paraffin-embedded lung tissues of autopsy children died of CAP. RESULTS: No major difference on the detection rate of Hib between 50-60s and 80s-2002 was found. The detection rate of Hib by direct ISPCR was higher than the other two methods. By Southern blot, Hib was identified from 8 out of 100 samples (8%), including 4 out of 56 in 1950-60s (7.1%) and 4 out of 44 (9.1%) (chi2 = 0.084, P>0.05) in 1980s-2002. By ISPCR, Hib was identified from 17 out of 100 samples (17%), including 8 out of 56 in 1950-60s (14.3%) and 9 out of 44 (20.5%) with chi2 = 0.665, P > 0.05, in 1980s-2002. Positive cases diagnosed by both Southern blot and ISPCR were 7%. CONCLUSION: Hib was one of the main bacterial pathogens causing CAP and deaths among children. Direct ISPCR was prefertable to be used in pathogenic diagnosis on children pneumonia, in terms of its sensitivity, specificity and localization.

[Surveillance of antimicrobial susceptibility of Haemophilus influenzae isolates from children in Beijing, Shanghai, and Guangzhou 2000 - 2002].

OBJECTIVE: To investigate the situation of antibiotic resistance of Haemophilus influenzae isolates from Chinese children. METHODS: Eight hundred and ninety-eight strains of H. influenzae isolated from randomly selected pediatric out-patients in Beijing, Shanghai and Guangzhou 2000 approximately 2002 underwent determination of antibiotic susceptibility by E test MIC method for beta-lactam antibiotics (ampicillin, amoxicillin/clavulanic acid, ceftriaxone, cefuroxime, and cefaclor) and KB disc diffusion method for chloramphenicol, tetracycline, sulfamethoxazole/trimethoprim (SMZ/TMP), azithromycin, and ciprofloxacin. RESULTS: The average rate of beta-lactamase production among these isolates was 12%. The MIC50 and MIC90 of ampicillin were 0.25 microg/ml and 4 microg/ml respectively for the 898 isolates, 88% of the isolates were susceptible to ampicillin and 10.6% was resistant. There was no beta-lactamase negative strains among the ampicillin intermediately-susceptible and resistant strains. All the isolates were susceptible to amoxicillin/clavulanic acid, ceftriaxone, cefuroxime and azithromycin. 96.1% of the H. influenzae isolates generally remained susceptible to cefaclor with a MIC50 of 1.5 microg/ml and a MIC90 of 3 microg/ml, and 99% of the isolates were susceptible to ciprofloxacin. The susceptibility rate to tetracycline of the isolates from Beijing and Shanghai areas were 57% and 61% respectively, both lower than the susceptibility rates of the isolates from Guangzhou (81%), while the resistant rate to SMZ/TMP of the isolates from Beijing was 35%, lower than those of the isolates from Guangzhou (47%) and Shanghai (54%). The resistant rate to ampicillin was 7.7% in 2000 and was increased to 14.5% in 2002. 34.5% of all the isolates were susceptible to 8 antimicrobial agents while 12.8% was multi-drug resistant. 58.5% of the isolates were distributed in five major antimicrobial resistance profiles in which SMZ/TMP resistance (29.8%) was the most prevalent, followed by SMZ/TMP and tetracycline combined resistance (12.5%) and tetracycline resistance (9.4). The ampicillin non-susceptible isolates had higher resistant rates to cefaclor (23.5%), tetracycline (63.3%), SMZ/TMP (74.5%) and chloramphenicol (63.3%) than the ampicillin susceptible strains (1.6%, 51.4%, 11.1% and 4.9% respectively). CONCLUSION: Beta-lactamase production and ampicillin resistance among the isolates from Chinese children are increasing generally during the period 2000 approximately 2002. There is variation of resistance among different regions. There are strong correlations between ampicillin resistance and resistance to cefaclor, chloramphenicol, and tetracycline among the H. Influenzae isolates.

[Macrolide-resistant Streptococcus pneumoniae in the pediatric population in Beijing].

OBJECTIVE: To analyze the mechanisms of macrolide resistance in Streptococcus pneumoniae from children in Beijing. METHODS: The MICs of penicillin and erythromycin were determined by the E-test methods for 200 Streptococcus pneumoniae isolates collected from 2002 to 2003 at Beijing Children's Hospital. MICs of azithrhomycin, clarithromycin, acetylspiramycin and clindamycin for 147 erythromycin-resistant isolates were detected by the agar dilution methods. For phenotyping, macrolide resistance induction tests were used in erythromycin-resistant isolates. PCR was used to determine the presence of the erythromycin-resistant genes. RESULTS: Of 200 Streptococcus pneumoniae isolates, 89.5% were resistant to erythromycin. In 147 erythromycin-resistant isolates, resistance rates were as follows: azithromycin, 100%; clarithromycin, 100%; acetylspiramycin, 95.2%; and clindamycin, 95.9%. The most common macrolide resistance phenotype was the cMIS phenotype (95.9%), 1.4% had the iMLS phenotype and 2.7% the M phenotype. Erythromycin-resistant isolates were characterized for the underlying resistance genotype, with 79.6% having the ermB genotypes, 17.7% having both ermB and mefA, 2.7% having the mefA, and none having neither ermB nor mefA genotypes. CONCLUSIONS: The rates of carriage of macrolide-resistant Streptococcus pneumoniae by children were high in Beijing during 2002 - 2003. cMLS was the most prevalent phenotype among erythromycin-resistant Streptococcus pneumoniae isolates, and ribosomal modification (ermB gene coded) was the main resistance mechanism against macrolides in Beijing region.