Susceptibility of Streptococcus pyogenes to two macrolides in northern Israel

In the present study, the minimal inhibitory concentration (MIC) of azithromycin and roxithromycin for 200 Streptococcus pyogenes isolates from outpatients with tonsillopharyngitis were determined using Etest. All but one (99.5%) of the isolates were sensitive to both antibiotics; the MIC of the resistant isolate being 12 mg/l to azithromycin and 32 mg/l to roxithromycin. In this region, macrolides remain the drug of choice for the treatment of patients with S. pyogenes tonsillitis who present allergy to penicillin. The routine testing of susceptibility of S. pyogenes to macrolides in northern Israel is not justified.     

Macrolide resistance can be transferred by conjugation from viridans streptococci to Streptococcus pyogenes

Efflux pumps encoded by mef genes are among the most common mechanisms of resistance to macrolides. These genes are often located on horizontally transferable elements such as transposons. We present data indicating conjugative transfer of the mef(E) gene from viridans streptococci to the pathogen Streptococcus pyogenes. The mef(E) gene is located on the previously described MEGA (macrolide efflux genetic assembly) element. Of 110 isolates tested, 85% of those that carried the mef(A/E) gene carried it on MEGA, and in all cases of conjugal transfer of the mef(E) gene it was carried on MEGA. It therefore appears reasonable to draw the conclusion that this element is important in the lateral transfer of macrolide resistance between streptococci.     

Resistance to macrolides in Group A streptococci from the European section of Turkey: genetic and phenotypic characterization

The aim of this study was to determine the susceptibilities to macrolides of Group A streptococcal isolates from the European section of Turkey. In the case of resistant isolates, the patterns and genetic mechanisms of erythromycin resistance were studied. Seven (2.7%) of the 260 isolates were resistant to erythromycin. Four of them showed the M phenotype and harboured mefA genes whereas three isolates showed the inducible macrolide, lincosamide and streptogramin B resistance phenotype and harboured ermTR genes. In the European section of Turkey, the current resistance rate of Group A streptococci to macrolides remains low.     

化脓性链球菌耐药与毒力基因研究

目的 调查一组70株化脓性链球菌耐药与毒力基因存在状况，以及菌株间的亲缘关系。方法 70株化脓性链球菌分离自日照市中心医院2012-2017年急性扁桃体炎、急性咽炎患者的咽拭子标本。5种抗菌药物敏感性试验为Kirby-Bauer法。采用聚合酶链反应(PCR)及序列分析的方法分析8种耐药基因和3种毒力基因。检测结果作样本聚类分析(UPGMA法)。结果 70株化脓性链球菌对青霉素、苯唑西林、万古霉素敏感性均达100.00%，对红霉素耐药率较高(94.29%)。青霉素耐药基因均为阴性，大环内酯类耐药基因检出ermB和mefA基因，其中ermB和/或mefA阳性66株(94.29%)。可移动遗传元件标志基因intTN916检出率高(94.29%)。3种毒力基因均有较高的检出率：spyA58株(82.86%)、sagA68株(97.14%)、slo64株(91.43%)。样本聚类分析可见，70株化脓性链球菌分为A~N共14个分类单元，根据是否携带ermB基因，可分为Ⅰ、Ⅱ二个群，Ⅰ群9个分类单元均携带ermB基因，Ⅱ群5个分类单元均不携带ermB基因。结论 70株化脓性链球菌携带的大环内酯类耐药基因ermB和mefA，以及可移动遗传元件标志基因intTN916是对红霉素产生耐药的重要原因。spyA、sagA、slo等3种毒力基因是化脓性链球菌常见的毒力基因,推测它们是化脓性链球菌感染导致感染灶局部炎症和坏死的原因。     

Macrolide resistance phenotypes and mechanisms of resistance in Streptococcus pyogenes in La Rioja, Spain

One hundred and thirty seven consecutive clinical Streptococcus pyogenes isolates were evaluated for macrolide-lincosamide-streptogramin resistance (MLS). Forty of these isolates were resistant to erythromycin (29.2%), 36 of them showed the new M resistance phenotype (erythromycin resistant and clindamycin susceptible) and four isolates had the MLS(B) resistance phenotype (erythromycin and clindamycin resistant). In all 36 isolates with the M resistance phenotype, the mef gene was identified by polymerase chain reaction (PCR). In two of the four S. pyogenes isolates with the MLS(B) phenotype, both ermB and ermTR genes were found; negative results were obtained with the other two isolates which might possess a new mechanism of high level resistance against erythromycin not previously described. In summary, a high rate of erythromycin resistance was found in S. pyogenes isolates and the active efflux pump mediated by the mef gene was the mechanism most frequently involved.     

The epidemiology of antibiotic resistance in Streptococcus pneumoniae and the clinical relevance of resistance to cephalosporins, macrolides and quinolones

Invasive non-meningeal pneumococcal infections remain a major cause of morbidity and mortality worldwide. The factors affecting the epidemiology and mortality of pneumococcal infections are discussed. The increase and spread of resistance to antimicrobial agents among pneumococci is a cause of concern to the clinician. There are links between the usage of antibacterial agents and the development of resistance. Resistance to penicillin and other beta-lactams has become widespread but this does not appear to have decreased the efficacy of some of these agents against non-meningeal infections. There is evidence that the good pharmacokinetic and pharmacodynamic features of the third generation cephalosporins (cefotaxime and ceftriaxone) contribute to their efficacy in vivo. New breakpoints for cefotaxime and ceftriaxone against non-meningeal pneumococcal isolates were proposed by the National Committee for Clinical Laboratory Standard (NCCLS, US), based on the clinical evidence of the efficacy of these drugs. In contrast there is increasing evidence that resistance to macrolides can lead to a poor clinical response. Fluoroquinolones have been widely used to treat respiratory tract infections among others, and pneumococcal resistance to these agents in vitro, although currently low, is increasing. There are reports that resistance to fluoroquinolones can develop during treatment and may be reflected in a lack of clinical response. Several clinical and epidemiological variables (e.g. prior antibiotic use) can be useful to identify patients at risk from infections with antibiotic-resistant pneumococci. These patients would be those who would benefit the most from a pneumococcal vaccination programme.     

Genotype and phenotype relationship in MLSb resistance in Streptococcus pyogenes and Streptococcus agalactiae isolated in central Italy

The aim of this work is to study a correlation between phenotype and genotype in clinical isolates of erythromycin-resistant Streptococcus spp. Among the 25 erythromycin-resistant S. pyogenes, we detected six strains with iMLSB, nine with cMLSB and two with M phenotypes. Among 14 erythromycin-resistant S. agalactiae, we detected five strains with iMLSB, seven with cMLSB and none with an M phenotype. Moreover, 8 S. pyogenes and 2 S. agalactiae showed a phenotype not matching the known ones described in literature, defining an unknown phenotype. Upon examination, the genetic profiles, erm(A), erm(B) and mef(A), of the clinical isolates did not easily correlate with a specific phenotype. Our findings highlighted that the whole matter of phenotypic diversity in macrolide-resistant S. pyogenes and S. agalactiae strains and the correlation with their genetic profiles should be submitted to a more careful analysis of phenotypic and genotypic characterization.     

Antimicrobial susceptibility and macrolide resistance genes in Streptococcus pyogenes collected in Austria and Hungary

A total of 341 clinical isolates of Streptococcus pyogenes from Vienna, Austria and three Hungarian cities were tested for susceptibility to four macrolides and 12 other antibiotics. All isolates were fully susceptible to penicillin and the other beta-lactams tested. A high level of tetracycline resistance was found in Austria (26.7%) and in Hungary (30.5%). The rate of resistance to erythromycin, clarithromycin and azithromycin was 4.7% in Vienna and 3.7% in the Hungarian communities. In both countries, the MIC(90) values of erythromycin and clarithromycin were 0.12 mg/L and the MIC(90) of josamycin was 0.5mg/L. The M phenotype of resistance conferred by the mefA genes was predominant (n = 9) among the macrolide-resistant isolates (n = 14).     

mef(A) is the predominant macrolide resistance determinant in Streptococcus pneumoniae and Streptococcus pyogenes in Germany

In this study, macrolide-resistant Streptococcus pneumoniae and Streptococcus pyogenes isolates from Germany were carefully characterised by susceptibility testing, phenotyping, polymerase chain reaction (PCR) and sequencing of macrolides resistance genes, and multilocus sequence typing (MLST). Of 2045 S. pneumoniae and 352 S. pyogenes isolates, 437 (21.4%) and 29 (8.2%), respectively, were found to be macrolide-resistant. Amongst the S. pneumoniae isolates, the most prevalent resistance marker was mef(A) (57.7%) followed by erm(B) (27.0%) and mef(E) (11.2%). Of note, the dual resistance mechanism mef(E)+erm(B) was found in a relatively high proportion (4.1%) of pneumococcal isolates. Amongst the S. pyogenes isolates, 31.0% carried mef(A), 34.5% erm(B) and 13.8% erm(A). Dissemination of a single clone [mef(A)-positive England(14)-9] has significantly contributed to the emergence of macrolide resistance amongst pneumococci in Germany.     

Molecular characterisation of macrolide resistance mechanisms of Streptococcus pneumoniae and Streptococcus pyogenes isolated in Germany, 2002-2003

In the present study, a real-time PCR protocol was developed for the detection of macrolide resistance determinants and was validated in a nationwide study in Germany covering a total of 236 Streptococcus pyogenes and 241 Streptococcus pneumoniae strains collected from children < or = 16 years of age with community-acquired infections. Macrolide resistance was observed in 19.9% of pneumococcal strains and 14% of S. pyogenes isolates. Of the erythromycin A-resistant S. pyogenes strains, 93.9% showed the efflux type mef(A); 62.5% of the S. pneumoniae strains were mef(A)- and 37.5% erm(B)-positive. The correlation of the results of real-time PCR assay genotyping in the present study compared with those of conventional PCR genotyping and resistance phenotyping was 100%. Macrolide resistance is of growing concern in Germany. This highly sensitive and specific PCR assay to detect macrolide resistance has the potential to provide sufficiently rapid results to improve antibiotic treatment of streptococcal infections.     

肺炎链球菌流行基因型的细菌毒力及大环内酯类的耐药机制

目的研究分离的侵袭性肺炎链球菌(IPD)的流行血清基因型、致病毒力基因、大环内酯类耐药机制及与细菌毒力的关系。方法收集2013年6月~2016年6月分离鉴定的侵袭性肺炎链球菌共12株(观察组),同时收集10株携带肺炎链球菌(对照组);采用多重PCR扩增法进行血清基因型分型,PCR扩增6个致病毒力基因,包括荚膜(cps2A)、细菌素(bacteriocin)、表面黏附素A(psa A)、B组链球菌细胞壁分离蛋白(pcs B)、溶血素(ply)和酪蛋白水解蛋白酶P(clp P),分析其碱基序列的突变情况;采用MIC法测定青霉素、头孢吡肟、左氧氟沙星、红霉素和美罗培南的耐药性和最低抑菌浓度(MIC)值。结果基因型14、6A/6B和19F在2组中检出率比较差异无统计学意义(P>0.05),19A、6C和17F在观察组中检出率显著高于对照组(P<0.05)。2组对头孢吡肟、左氧氟沙星和美罗培南的敏感率比较差异无统计学意义(P>0.05)。观察组对青霉素和红霉素不敏感率和MIC值显著高于对照组(P<0.05)。结论分离的IPD血清型主要有19A、6C和17F,共有6种致病毒力基因,对青霉素和红霉素耐药。     

幽门螺杆菌对大环内酯类抗生素的耐药机制及耐药性检测

幽门螺杆菌是慢性活动性胃炎、消化性溃疡的主要病因，近年来幽门螺杆菌对大环内酯类抗生索的耐药率不断上升。关于幽门螺杆菌耐药机制的问题，目前还存在许多争议。随着检测技术的不断进步，现已发展了多种检测幽门螺杆菌耐药的分子生物学方法，本文就幽门螺杆菌对大环内酯类抗生素的耐药机制及耐药性检测方面作一综述。     

酿脓链球菌对大环内酯类抗菌药物耐药表型与基因型研究

目的 研究酿脓链球菌对大环内酯类抗菌药物的耐药表型与基因型。方法 采用琼脂平板稀释法测定97株酿脓链球菌对红霉素、克林霉素、麦迪霉素、阿奇霉素、克拉霉素和青霉素的敏感性；用双纸片法检测酿脓链球菌耐药表型；用PCR方法检测耐大环内酯的酿脓链球菌携带的耐药基因。结果 97株酿脓链球菌中82株表现为对大环内酯类抗菌药物不敏感，其中42株表现为eMLS型耐药，37株为iMLS型耐药，3株细菌为主动外排M型耐药；82株对大环内酯不敏感的酿脓链球菌中77株检测到耐药基因，其中12株具有ermB基因，25株具有ermTR基因，2株具有mefA基因，21株同时具有ermB／ermTR基因，5株同时具有ermB／mefA基因，3株同时具有ermTR／mefA基因，9株同时具有ermB／ermTR／mefA基因，5株未能检测到三种耐药基因。结论 酿脓链球菌对大环内酯类抗菌药物的耐药率较高，耐药表型以cMLS和iMLS为主，耐药基因以ermB和ermTR多见。     

Prevalence of antimicrobial resistance in Haemophilus influenzae, Streptococcus pneumoniae, Moraxella catarrhalis and Streptococcus pyogenes: results of a multicentre study in Turkey

The in vitro activities of several antimicrobial agents against clinical isolates of Streptococcus pneumoniae (283), Haemophilus influenzae (272), Moraxella catarrhalis (179) and Streptococcus pyogenes (256) were determined in a multicentre study with the participation of five hospitals from four cities in Turkey. Penicillin resistance in S. pneumoniae was evaluated using the E-test and the remaining agents by disk diffusion. For S. pneumoniae overall 25.8% of the isolates were intermediately and 3.9% were highly resistant to penicillin and resistance to chloramphenicol, azithromycin and trimethoprim/sulphamethoxazole (TMP/SMX) was 3.8, 2.1 and 55.4%, respectively. Seven percent of H. influenzae produced beta-lactamase and all were susceptible to cefotaxime and azithromycin; the highest rate of resistance, 23.5%, was for TMP/SMX. Eighty-one percent of M. catarrhalis isolates produced beta-lactamase, 18.4% were resistant to TMP/SMX and all were susceptible to sulbactam/ampicillin combination. Resistance to chloramphenicol and azithromycin of S. pyogenes was 2.2 and 1.9%, respectively.     

Antimicrobial susceptibilities and distribution of resistance genes for beta-lactams and macrolides in Streptococcus pneumoniae isolated between 2002 and 2004 in Tokyo

Antimicrobial susceptibilities of 205 Streptococcus pneumoniae strains isolated between 2002 and 2004 in Japan were examined and the distribution of genes for resistance to penicillins and macrolides were investigated by polymerase chain reaction. The molecular epidemiology of 92 randomly selected isolates was also examined by pulsed-field gel electrophoresis (PFGE). The numbers of S. pneumoniae isolates resistant to benzylpenicillin, clarithromycin and tetracycline were, respectively, 39 (19%), 111 (54%) and 155 (76%), and the numbers increased annually. All isolates were susceptible to amoxicillin, fluoroquinolones, vancomycin and linezolid. Analysis of mutations in the genes for penicillin-binding protein showed that 92% of isolates had mutations in pbp1a, pbp2b and/or pbp2x. Susceptibility to benzylpenicillin decreased with increasing number of mutated pbp genes. The macrolide resistance genes ermB and mefA were found in 99 (48%) and 76 (37%) isolates, respectively. The presence of ermB was associated with high-level resistance to macrolides, and the percentage of isolates with ermB increased annually. The presence of mefA also increased with increasing number of mutated pbp genes. Although the 92 isolates belonged to 74 PFGE types, three groups with an 80% similarity in their PFGE patterns were found at high frequency. Two of the three groups contained no isolates susceptible to penicillin and/or tetracycline, and their percentages increased annually. Our results suggest that the number of S. pneumoniae isolates with reduced susceptibility due to accumulation of resistance genes has been increasing.     

Clinical isolates of macrolide-resistant Streptococcus pyogenes in Central Greece

A total of 300 Streptococcus pyogenes isolates, collected during 2001 from five hospitals in the Thessalia district (Central Greece), were examined for their resistance to macrolides. Resistance to erythromycin was detected in 58 isolates (19.3%). Of these, 68.9% were susceptible to clindamycin (M-phenotype) and carried the mefA gene. Of the remaining isolates, 18 expressed the MLS(B) phenotype: 12 and six exhibited inducible and constitutive resistance to clindamycin, respectively. All of these strains were found to be ermA(TR) positive, except for four that had the ermB gene. Of the erythromycin-resistant strains, none was found to be resistant to penicillin, tetracycline or quinupristin-dalfopristin. Molecular typing by PFGE showed the presence of a limited number of clones.     

Susceptibility and resistance emergence studies with macrolides

An extended elimination half-life and good tissue penetration enable oral azithromycin to attain high and prolonged concentrations in infected tissues, yielding high antibacterial activity in vivo. It has been suggested, however, that prolonged subinhibitory concentrations of azithromycin from 2 to 4 weeks after therapy may lead to the emergence of azithromycin resistance in vivo, compared with other macrolide antibiotics. Data from two types of in vitro susceptibility studies, an animal tissue infection model, and a clinical pediatric study demonstrate that prolonged tissue concentrations of azithromycin are unlikely to lead to the emergence of resistance in the clinical setting. Further, data from in vitro susceptibility studies indicate that resistance to macrolides, and azithromycin in particular, is significantly over-estimated for bacterial strains incubated in the presence of CO2.