Penicillin-binding proteins (PBPs) are the target of β-lactam antibiotics (the major treatment for Streptococcus pneumoniae infections), and mutations in PBPs are considered as a primary mechanism for the development of β-lactam resistance in S. pneumoniae. This study was conducted to investigate the mutations in the PBPs of clinical S. pneumoniae isolates in Hangzhou, China, in correlation with β-lactam resistance. Results showed that 19F was the predominant serotype (7/27) and 14 of the S. pneumoniae isolates were resistant to both penicillin G and cephalosporin. Genotyping results suggested that β-lactam-resistant isolates primarily exhibited single-site mutations in both the STMK and SRNVP motifs of pbp1a in combination with double-site mutations in the STMK motif of pbp2x, which might be the primary mechanisms underlying the β-lactam resistance of the isolates in this study.
Anti-Bacterial Agents ; pharmacology ; China ; epidemiology ; Drug Resistance, Bacterial ; Humans ; Pneumococcal Infections ; epidemiology ; microbiology ; Streptococcus pneumoniae ; drug effects ; genetics ; beta-Lactams ; pharmacology

Bacterial Vaccines ; biosynthesis ; Drug Resistance, Bacterial ; genetics ; Genetic Engineering ; Humans ; Leptospira interrogans ; genetics ; immunology ; pathogenicity ; Leptospirosis ; prevention & control ; Mycobacterium tuberculosis ; drug effects ; genetics ; Streptococcus pneumoniae ; drug effects ; genetics ; Vaccines, Synthetic ; biosynthesis

OBJECTIVETo investigate the relation of pbp2B, ermB, ermA/B and mefA genes to penicillin and erythromycin resistance among isolated Streptococcus pneumoniae (Sp) in children.

METHODSTwenty-six strains of Sp were collected from September 2002 to April 2003 at the Children Hospital of Suzhou University. (1) Twenty-six pneumococcal isolates were obtained from respiratory tract secretions of children with respiratory diseases. (2) Susceptibility of the isolates to penicillin, cefuroxime, ceftriaxone, cefotaxime and erythromycin was determined by E-test. (3) The genes pbp2B, ermB, ermA/B and mefA of the isolates were detected with PCR. (4) The PCR product of pbp2B gene was sequenced. (5) DNA sequences of pbp2B of pneumococcal isolates were compared with those of SpR6 [penicillin sensitive (www.ncbi.nlm.gov/nucleotide, NC-003098)].

RESULTSAmong the 26 isolates studied, pbp2B gene mutation was found in 15(58%) isolates, all were point mutation of A, B, C and D genotypes which were seen in 11(73%), 2(13%), 1(7%) and 1(7%), respectively. The numbers of isolates susceptible to penicillin, cefuroxime, ceftriaxone and cefotaxime were 9(82%), 10(91%), 11(100%) and 11(100%), of 11 non-mutation isolates;numbers of isolates resistant to penicillin, cefuroxime, ceftriaxone, and cefotaxime were 13(87%), 11(73%), 1(7%) and 1(7%) out of 15 isolates with mutation.ErmB, ermA/B, mefA and erm/mef genes were positive in 9(35%), 16(62%), 7(27%) and 21(81%)isolates. MIC of erythromycin was 2 to > 256 mg/L among pneumococcal isolates with erm/mef genes.

CONCLUSIONAmong antibiotic resistant pneumococcal isolates in the area, the main basis of penicillin resistance was the mutation of pbp2B genes. Genotype A mutation had the highest rate among the isolates with mutation and manifested as resistance to penicillin and cefuroxime. Expression of either all or any of the ermA, ermB and mef genes led to erythromycin resistance. Antibiotics resistant Sp strains in this area are forming a challenge to efficacy of penicillin and erythromycin.

Aminoacyltransferases ; genetics ; Anti-Bacterial Agents ; pharmacology ; Bacterial Proteins ; genetics ; Child ; Drug Resistance, Bacterial ; Erythromycin ; pharmacology ; Humans ; Membrane Proteins ; genetics ; Methyltransferases ; genetics ; Penicillin Resistance ; Penicillin-Binding Proteins ; genetics ; Streptococcus pneumoniae ; drug effects ; genetics

OBJECTIVETo investigate the antimicrobial resistance and penicillin resistance-associated genes (TEM and pbp2B) of Streptococcus pneumoniae (S. pneumoniae) isolated from sputum specimens of Guangzhou children with respiratory tract infection.

METHODSE-test and Kirby-Bauer methods were applied to detect the antibiotic susceptibility of 44 strains of S. pneumoniae. PCR was used to detect resistance genes pbp2B and TEM, followed by DNA sequence analysis of pbp2B gene. The sequence results were compared to those of penicillin-susceptible S. pneumoniae R6.

RESULTSOf the 44 isolates of S. pneumoniae, only 5 (11.4%) were susceptible to penicillin. All strains were resistant to erythromycin but susceptible to ofloxacin and vancomycin. The resistance rate of the isolates to clindamycin and trimoxazole was more than 90%. The S. pneumoniae isolates showed a high susceptibility to amoxicillin, imipenem and ceftriaxone, with a resistance rate of 0, 2.6% and 3.9%, respectively. The sequence analysis showed that more than 99% nucleotide sequence of pbp2B gene of five penicillin-susceptible isolates was the same as penicillin-susceptible S. pneumoniae R6, without any amino acid replacement. Site mutation was found in the remaining 39 penicillin-nonsusceptible isolates with a nucleotide mutation rate ranging from 13.2% to 23.1% and amino acid replacement rate from 6.5% to 10.9%. The 39 penicillin-nonsusceptible isolates were classified into 4 types according to the mutation site between Ser391 and Thr492 of pbp2B: type I (n=30), type II (n=7), type III (n=1) and type IV (n=1). No TEM gene was detected in all the 44 S. pneumoniae isolates.

CONCLUSIONSThe S.pneumoniae isolates from Guangzhou children with respiratory tract infection are resistant to penicillin and erythromycin. Amoxicillin and the third generation cephalosporin may be recommended for treating S. pneumoniae infection. The mutation of pbp2B gene plays an important role in the development of S. pneumoniae resistance to penicillin.

Aminoacyltransferases ; genetics ; Child, Preschool ; Drug Resistance, Bacterial ; genetics ; Female ; Humans ; Infant ; Male ; Microbial Sensitivity Tests ; Penicillin Resistance ; genetics ; Penicillin-Binding Proteins ; genetics ; Respiratory Tract Infections ; microbiology ; Streptococcus pneumoniae ; drug effects ; genetics ; beta-Lactamases ; genetics

OBJECTIVETo observe the effect of amino acid substitution in conserved sequence of penicillin-binding protein (PBP) 1A, 2B, 2X on antimicrobial activity of beta-lactams against Streptococcus pneumoniae (SP).

METHODMinimal inhibitory concentration (MIC) of 6 beta-lactams was determined by the E-test in 59 SP strains. The penicillin-binding protein genes pbp1a, 2b, 2x in every SP strain were amplified by nested-polymerase chain reaction (nPCR), then the PCR products were sequenced using automatic genetic analyzer directly. To analyze the amino acid substitutions, the DNA sequences were converted to protein sequences and aligned by Clustalx software. According to amino acid substitution in conserved sequence of PBP2B, 3 phenotypes were observed, including: PBP2B phenotype I (no amino acid substitution); PBP2B phenotype II (Glutamine 432-->Leucine and/or Threonine 445/451-->Alanine/Serine, Glutamic 481-->Glycine, 1 strain had proline insertion between residues 431/432); PBP2B phenotype III (Alanine 624-->Glycine with the addition of phenotype II). According to amino acid substitution in conserved sequence of PBP1A, 3 phenotypes were observed, including: PBP1A phenotype I (no amino acid substitution); PBP1A phenotype II (Threonine 574-->Asparagine, Serine 575-->Threonine, Glutamine 576-->Glycine, Phenylalanine 577-->Tyrosine, 574TSQF-->NTGY); PBP1A III (Threonine 371-->Alanine/Serine, Proline 432-->Threonine with the addition of 574TSQF-->NTGY). According to amino acid substitution in conserved sequence of PBP2X, 4 phenotypes were observed, including: PBP2X phenotype I (no amino acid substitution); PBP2X phenotype II (Histidine 394-->Leucine or Threonine 338-->Alanine); PBP2X phenotype III (Threonine 338-->Alanine, Isoleucine 371-->Threonine, Arginine 384-->Glycine and Leucine 546-->Valine); PBP2X phenotype IV (Methionine 339-->Phenylalanine, Methionine 400-->Threonine with the addition of PBP2X phenotype III).

RESULTAmong 59 SP strains antibacterial activities distribution (sensitive strains, intermediate strains and resistant strains) of 6 beta-lactams were penicillin (12, 29, 18); amoxicillin(49, 9, 1); cefuroxime (16, 16, 27); ceftriaxone (47, 1, 11); cefotaxime (47, 3, 9); imipenem (49, 10, 0). beta-lactam antibiotics insensitive strains (intermediate + resistant strain) in PBP2B phenotype III, PBP1A phenotype III, PBP2X phenotype III and IV were significantly increased, the MIC(50) of these strains were significantly higher than that of the others.

CONCLUSIONThe amino acid substitutions in or vicinal conserved sequence of PBP of SP increase MIC for beta-lactam antibiotics.

Amino Acid Substitution ; Aminoacyltransferases ; genetics ; Anti-Bacterial Agents ; pharmacology ; Bacterial Proteins ; genetics ; Microbial Sensitivity Tests ; Penicillin-Binding Proteins ; genetics ; Peptidyl Transferases ; genetics ; Streptococcus pneumoniae ; drug effects ; beta-Lactam Resistance ; genetics ; beta-Lactams ; pharmacology

OBJECTIVETo construct prokaryotic expression systems of TCS genes comD/comE/comC of Streptococcus pneumoniae, and to determine the correlation of ComD and ComC with the drug resistance.

METHODSThe entire comD, comE and comC genes were amplified by PCR and their prokaryotic expression systems were established by routine genetic engineering technique. SDS-PAGE and Bio-Rad Agarose Image Analyzor was applied to measure the outputs of target recombinant proteins rComD, rComE and rComC. Rabbits were immunized with these recombinant proteins to prepare antisera. The resistance of S.pneumoniae strains to penicillin and cefotaxime was examined after ComD and ComC were blocked by antisera.

RESULTCompared with the reported sequences, similarities of nucleotide and amino acid sequences of the cloned comD, comE and comC genes were 98.4% approximately 99.3% and 99.1% approximately 100%, respectively. The constructed engineering bacteria E.coli BL21DE3(pET42a-comD), E.coli BL21DE3(pET42a-comE) and E.coli BL21DE3(pET42a-comC) were able to efficiently express the target recombinant proteins and the outputs of rComD, rComE and rComC were 28%, 25% and 35% of the total bacterial proteins, respectively. The double immunodiffusion titers of rabbit antisera against rComD, rComE or rComC were 1:4, 1:4 and 1:8, respectively. After the ComD and/or ComC were blocked by the antisera, the cefotaxime-sensitive S. pneumoniae strains became to resistant to antibiotics but there were no changes for cefotaxime-resistant strains and resistance to penicillin for all tested strains.

CONCLUSIONThe prokaryotic expression systems of S.pneumoniae comD/come/comC genes have been successfully constructed, and the study also indicates that both the ComD and ComC are involved in the drug resistance of S. pneumoniae to cefotaxime.

Animals ; Bacterial Proteins ; biosynthesis ; genetics ; Cefotaxime ; pharmacology ; Escherichia coli ; genetics ; metabolism ; Rabbits ; Recombinant Proteins ; biosynthesis ; genetics ; Recombination, Genetic ; Signal Transduction ; Streptococcus pneumoniae ; drug effects ; genetics ; beta-Lactam Resistance ; genetics

OBJECTIVETo investigate the prevalence and drug resistance of Streptococcus (S.) pneumoniae in patients infected in communities and molecular epidemiology with BOX-polymerase chain reaction (PCR) in Chongqing areas.

METHODSA total of 680 clinical specimens from sputum and throat/nasal swabs were collected from patients seen from September 2000 to March 2001. Antibiotic susceptibility was determined by agar dilution test. BOX-PCR was used for molecular typing of S. pneumoniae.

RESULTSA total of 39 isolates of S. pneumoniae were collected with the isolation rate of 5.7%. Of the 34 S. pneumoniae strains, two showed low-level resistance to penicillin (MIC 0.125 mg/L), one to levofloxacin, but many to macrolide and clindamycin (nearly 70%). All the strains were susceptible to beta-lactams and vancomycin. BOX-PCR typing demonstrated a high discriminatory potential and easy to be accurately analysed. 35 S. pneumoniae strains (include ATCC49619) were divided into 25 distinct types, representing 29 subtypes with A (n = 3) as the predominant type. 2 penicillin-resistant strains were shown to be different types.

CONCLUSIONPenicillin resistant rate of S. pneumoniae was low in Chongqing, but macrolide and clindamycin resistant strains were common while BOX-PCR typing was a suitable technique to type S. pneumoniae. No dominant antibiotic resistant strains were found in Chongqing.

China ; epidemiology ; Clindamycin ; pharmacology ; DNA, Bacterial ; genetics ; Drug Resistance, Bacterial ; genetics ; Humans ; Macrolides ; pharmacology ; Microbial Sensitivity Tests ; Molecular Epidemiology ; Pneumococcal Infections ; epidemiology ; microbiology ; Prevalence ; Streptococcus pneumoniae ; drug effects ; genetics

BACKGROUND: The present analysis focuses on phenotypic and genotypic characterizations of efflux-mediated erythromycin resistance in Streptococcus pneumoniae due to an increase in macrolide resistance in S. pneumoniae worldwide. METHODS: We investigated the prevalence of efflux-mediated erythromycin resistance and its relevant genetic elements from 186 specimens of S. pneumonia isolated from clinical and normal flora from Tehran, Iran. The presence of erythromycin resistance genes was tested by PCR with two sets of primers, specific for erm(B) and mef(A/E), and their genetic elements with tetM, xis, and int genes. Isolates were typed with the BOX PCR method and tested for resistance to six antibiotics. RESULTS: Antibiotic susceptibility tests revealed that 100% and 47% isolates were resistant to tetracycline and erythromycin, respectively. The erythromycin and clindamycin double-disc diffusion test for macrolide-lincosamide-streptograminB (MLSB) resistance phenotype showed 74 (84%) isolates with the constitutive MLSB phenotype and the remaining with the M phenotype. BOX PCR demonstrated the presence of 7 types in pneumococci with the M phenotype. Fourteen (16%) isolates with the M phenotype harbored mef(A/E), tetM, xis, and int genes. CONCLUSIONS: The present results suggest dissemination of polyclonal groups of S. pneumoniae with the M phenotype carrying resistance genes attributed to transposon 2009.
Anti-Bacterial Agents/*pharmacology ; Bacterial Proteins/genetics ; DNA, Bacterial/metabolism ; Drug Resistance, Multiple, Bacterial/*genetics ; Erythromycin/*pharmacology ; Genotype ; Humans ; Microbial Sensitivity Tests ; Phenotype ; Pneumococcal Infections/microbiology/pathology ; Polymerase Chain Reaction ; Streptococcus pneumoniae/*drug effects/*genetics/isolation & purification ; Tetracycline/pharmacology

BACKGROUNDDespite 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.

METHODSPulsed-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.

RESULTSFrom 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.

CONCLUSIONSFrom 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.

Child, Preschool ; China ; Drug Resistance, Bacterial ; Electrophoresis, Gel, Pulsed-Field ; Humans ; Infant ; Infant, Newborn ; Molecular Epidemiology ; Pneumococcal Infections ; drug therapy ; microbiology ; Serotyping ; Streptococcus pneumoniae ; classification ; drug effects ; genetics ; isolation & purification ; Time Factors

BACKGROUNDErythromycin-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.

METHODSA 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.

RESULTSA 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.

CONCLUSIONSThe 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.

Adolescent ; Anti-Bacterial Agents ; pharmacology ; Child ; Child, Preschool ; Drug Resistance, Bacterial ; Electrophoresis, Gel, Pulsed-Field ; Erythromycin ; pharmacology ; Humans ; Infant ; Multilocus Sequence Typing ; Pneumococcal Infections ; microbiology ; Serotyping ; Streptococcus pneumoniae ; classification ; drug effects ; genetics ; isolation & purification