Antimicrobial susceptibilities and analysis of genes related to penicillin or macrolide resistance in Streptococcus pneumoniae

One hundred and seventy-seven strains of Streptococcus pneumoniae derived from respiratory specimens between 1987 and 2001 were evaluated for their antimicrobial susceptibilities and distribution of genes related to penicillin and macrolide resistance. Resistance rates tended to be higher for the 1996-2001 isolates than for the 1987-1995 isolates for all beta-lactams tested. For benzylpenicillin the MIC(90) value of the isolates derived between 1996 and 2001 was 1.56 mg/L, while that of strains isolated between 1987 and 1990 was 0.05 mg/L. Furthermore, the number of strains susceptible to macrolides also decreased, but only two strains isolated in 1993 were resistant to levofloxacin of the 177 S. pneumoniae strains tested. When of genes relating to penicillin resistance were analysed using PCR with primers specific to susceptible alleles, although more than 50% of strains from 1987 to 1990 and 1991 to 1995 revealed no mutations in the pbp 1a, 2x and 2b genes, only 30.0% of strains derived between 1996 and 2001 showed no mutations in the pbp gene. Strains having mutations in all three pbp genes (1a, 2x and 2b) by the PCR method increased from only 2.2% in the 1987-1990 derived strains to 27.5% in the 1996-2001 strains. Furthermore, 64.1 and 60.0% of the isolates from 1987 to 1990 and 1991 to 1995, respectively, did not possess either the mefA or ermB by PCR analysis. Conversely, 75.0% of isolates from 1996 to 2001 possessed mefA and/or ermB. These genetic changes may explain the increase in the number of penicillin and macrolide resistant strains. We believe that it is important to evaluate changes in MIC as well as genetic mutations in order to select the most appropriate therapy for S. pneumoniae infections.     

Antimicrobial resistance and serotype distribution of Streptococcus pneumoniae isolates from Crete, Greece

Susceptibility to 14 antibiotics was determined for 125 clinical isolates of Streptococcus pneumoniae collected over a 3-year period in Crete, Greece. Twenty-three isolates (18.4%) showed intermediate resistance and 15 (12%) high-level resistance to penicillin. Erythromycin, chloramphenicol, tetracycline, trimethoprim-sulphamethoxazole and sparfloxacin resistance rates were 16.8, 10.4, 19.2, 24.8 and 9.6%, respectively. Multiple resistance was observed in 22 strains. Vancomycin and levofloxacin were the most active agents tested. The most prevalent serotype among penicillin-susceptible pneumococci was 14, followed by 9, 7 and 1, while among penicillin-intermediate or -resistant strains serotype 23 was predominant followed by 19 and 9. These results show that as well as a high level of penicillin resistance in this region, some strains are also resistant to other antibiotics and may show multi-drug resistance.     

Antimicrobial susceptibilities of Streptococcus pneumoniae,Haemophilus influenzae and Moraxella catarrhalis isolated in two successive respiratory seasons in the US

Antimicrobial susceptibilities of clinical isolates of Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis were determined in two consecutive respiratory seasons in the US and suggested that national susceptibilities to commonly tested antimicrobials changed only slightly from the 1999-2000 to the 2000-2001 respiratory season. However, a significant regional variation in S. pneumoniae susceptibilities was observed, as was a decrease in beta-lactamase rates among H. influenzae from the 1999-2000 to 2000-2001 respiratory seasons.     

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。     

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.     

Antimicrobial susceptibilities of organisms isolated from patients with urinary tract infections in 2002

Using the agar dilution method, the antibacterial activity of 18 antibiotics inclusive of 4 carbapenems were investigated against 101 strains of urinary pathogens isolated from patients with urinary tract infections who visited the Department of Urology at Kagoshima University Hospital, between January and December 2002. 4 strains of Staphylococcus aureus, 3 strains of Staphylococcus spp. (exclusive of S. aureus), 14 strains of Enterococcus faecalis, 3 strains of Enterococcus spp. (exclusive of E. faecalis), 41 strains of Escherichia coli, 21 strains of Enterobacteriaceae (exclusive of E. coli), 12 strains of Pseudomonas aeruginosa and 3 strains of glucose-nonfermentative Gram-negative rods (exclusive of P. aeruginosa) were examined. 1. Against clinical isolates of Gram-positive bacteria, vancomycin and teicoplanin were active. Additionally, arbekacin was active against S. aureus clinical isolates and ampicillin was active against E. faecalis clinical isolates. Carbapenems were active against clinical isolates of Gram-positive bacteria, except for multi-drug resistant strains of Gram-positive bacteria, such as methicillin-resistant S. aureus. 2. As for clinical isolates of Gram-negative bacteria, meropenem was most active against Enterobacteriaceae among 13 antibiotics tested. Against P. aeruginosa clinical isolates, MIC90 of meropenem was the lowest among 13 antibiotics tested. In addition, resistant rate of meropenem and biapenem against P. aeruginosa clinical isolates was lower than those of the other carbapenems tested. 3. As main urinary pathogens showed no remarkable increase in resistance to carbapenems, it can be stated that carbapenems retain their position as the drug of first choice for severe infection.     

Antimicrobial resistance of Streptococcus pneumoniae and Haemophilus influenzae isolated from children with community-acquired respiratory tract infections in Central Poland

Resistance to commonly used antimicrobial agents among the key respiratory pathogens is increasing worldwide and therefore a rational choice of an empirical treatment requires knowledge of both global and local resistance patterns. The susceptibility of 185 Streptococcus pneumoniae and 169 Haemophilus influenzae isolates collected from January 1999 to May 2002 at the Children's Memorial Health Institute, Warsaw, Poland, from 351 children with community-acquired respiratory tract infections (RTIs) has been determined. Of S. pneumoniae isolates, 84% were susceptible to penicillin, 91% to cefaclor, 95% to cefuroxime, 98% to cefotaxime, 79% to erythromycin, 46% to co-trimoxazole, 82% to clindamycin and 59% to tetracycline. The majority (83%) of erythromycin-resistant isolates tested carried the erm(B) gene, conferring the MLS(B) phenotype. All tetracycline-resistant S. pneumoniae strains analysed were tet(M) positive and tet(O) negative. A total of 24% of H. influenzae isolates were beta-lactamase-positive. H. influenzae susceptibility to amoxicillin/clavulanate, cefaclor, cefuroxime, azithromycin, tetracycline and co-trimoxazole was 100, 89, 94, 96, 96 and 43%, respectively.     

呼和浩特市89株肺炎链球菌携带耐药及毒力基因特征分析

目的 探究呼和浩特地区住院患者分离肺炎链球菌抗生素耐药基因及携带毒力基因分布情况,了解儿童株和成人株之间的差异。方法 收集内蒙古医科大学附属医院2010年10月-2016年4月临床患者分离89株肺炎链球菌,采用PCR技术检测其携带耐药和毒力基因表达情况,分别统计分析其在儿童及成人分布不同。结果 89株肺炎链球菌耐药基因pbp2a、pacE阳性率为100%;pbp2b、pbp3、teM、ermB、gyrB和parC阳性率在90%以上;tetM、teO基因阳性率分别为51.7%、36.0%。pbp1a和tet基因在儿童分离株和成人分离株之间有差异(χ2=5.107和22.984, P=0.01)。毒力基因stkP、nanA和piaA阳性率为100%;pcsB、phtD、pneumolysin、lytA、pspA和psaA基因阳性率均在90%以上;bacteriocin和clpP基因检测率较低,分别为79.8%和68.5%;cps2A基因在儿童株和成人株之间有差异(P=0.031)。结论 肺炎链球菌儿童分离株耐药基因携带率低于成人分离株,但毒力基因携带率明显高于成人分离株,不同人群肺炎链球菌菌分离株的生物学特征差异及其机制有待进一步研究。     

Antimicrobial susceptibility and molecular epidemiology of Streptococcus pneumoniae isolated from Shanghai, China

In this study, the antimicrobial resistance profiles of pneumococci isolated from respiratory specimens of patients from Shanghai, China, in 2004 and 2005 are described. Non-susceptible rates to penicillin and erythromycin among paediatric isolates (n=122) were 63.1% and 94.3%, respectively, whilst those of adult isolates (n=39) were 20.5% and 69.2%, respectively (P<0.0001 and P<0.0002). Nineteen serotypes were identified among 103 tested strains, 73.8% of which belonged to 19F, 14, 23F, 6B and 19A. The erm(B) gene was detected in 51 erythromycin-resistant strains (52.6%), the mef(E) gene in 5 strains (5.2%) and both erm(B) and mef(E) in 41 strains (42.3%). Among 45 sequence types (STs) determined by multilocus sequence typing (MLST) in these 103 isolates, 25 STs were new assignments and 9 STs contained 10 new alleles. On the other hand, 46 (68.7%) of 67 penicillin-non-susceptible S. pneumoniae and 51 (52.6%) of 97 macrolide-resistant S. pneumoniae were characterised as belonging to four international resistant clonal complexes, Taiwan(19F)-14, Spain(23F)-1, Spain(6B)-2 and Taiwan(23F)-15. Our findings indicate that the spread of international resistant clones played a predominant role in the emergence and increase of resistance in Shanghai. Conjugate vaccination may be a promising method to prevent the increase in pneumococcal resistance.     

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.     

Stabilization of penicillin resistance among Streptococcus pneumoniae isolated in Eastern Tennessee

Penicillin resistance among Eastern Tennessee isolates of Streptococcus pneumoniae has been increasing since the early 1990s. To maintain active surveillance of the prevalence of penicillin resistance among pneumococci isolated at our institution, antibiotic susceptibility testing was performed for 95 consecutive isolates and results were compared with those of strains examined 2 years earlier. The prevalence of penicillin resistance among local pneumococcal isolates may have stabilized in recent years.     

2004～2009年临床分离肺炎链球菌的血清型/群分布及耐药性监测

目的：了解当前本院临床分离肺炎链球菌的血清型/群分布及耐药趋势,为临床合理使用抗生素提供参考。方法：以2004～2009年临床分离的822株肺炎链球菌为研究对象,采用荚膜肿胀试验进行血清分型/群,E-test检测菌种对青霉素、头孢呋辛、头孢地尼、头孢克罗、红霉素、四环素、左氧氟沙星、万古霉素等8种抗生素的敏感性。结果：2004年青霉素不敏感肺炎链球菌（PNSP）的分离率为49.4%,并呈逐年上升趋势,至2006年PNSP分离率高达67.8%,2009年下降至51.0%。822株肺炎链球菌最常见的型/群是19群,其次是23、6、14、3、其他。PNSP在6种血清型/群中所占的比例在2004～2009年期间无显著性变化（P〉0.05）。肺炎链球菌对其他β内酰胺类抗生素的非敏感趋势类似青霉素,对红霉素、四环素的非敏感率始终在60%以上,其中青霉素耐药肺炎链球菌（PRSP）对红霉素和四环素几乎100%耐药,对左氧氟沙星、万古霉素的非敏感率均〈3%。结论：临床分离肺炎链球菌以19群、23群、6群、14群、3群常见;对β内酰胺类抗生素的非敏感率自2007年呈下降趋势,且对左氧氟沙星、万古霉素始终具有较高的敏感性。     

Antimicrobial susceptibility of Streptococcus pneumoniae and Haemophilus influenzae isolated in major hospitals in Nagano Prefecture

We determined the minimum inhibitory concentration (MIC) of various antimicrobial agents against 108 strains of Streptococcus pneumoniae and 144 strains of Haemophilus influenzae isolated from respiratory organs in the First Department of Internal Medicine, Shinshu University, and affiliated hospitals between January 2000 and February 2001. The following results were obtained. 1. Fifty-one (47.2%), 56 (51.9%), and 1 (0.9%) of 108 strains of S. pneumoniae were classified as penicillin-susceptible S. pneumoniae (PSSP), penicillin-intermediate S. pneumoniae (PISP), and penicillin-resistant S. pneumoniae (PRSP), respectively. 2. Three carbapenems had potent antimicrobial activity against PISP and PRSP. Furthermore, none of the strains were highly resistant (MIC > 2 micrograms/ml) to benzylpenicillin, ampicillin (ABPC), sulbactam/ampicillin (SBT/ABPC), cefotaxime (CTX), or cefepime (CFPM). 3. Eleven (7.6%) and 6 (4.2%) of 144 strains of H. influenzae were classified as beta-lactamase-producing ABPC-resistant strains and beta-lactamase negative ABPC-resistant H. influenzae (BLNAR), respectively. Levofloxacin, sulfamethoxazole/trimethoprim, and meropenem had potent antimicrobial activity against these resistant strains. 4. BLNAR strains were more highly resistant to CTX, CFPM, SBT/ABPC, and cefaclor than beta-lactamaseproducing strains. 5. In our surveillance study regarding clinical isolates of S. pneumoniae and H. influenzae from respiratory organs in Nagano prefecture, there were regional differences in the isolation rate and antimicrobial susceptibility. The isolation rates of resistant strains were lower than those reported in a nationwide survey.     

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).     

Antibacterial resistance patterns in Streptococcus pneumoniae isolated from elderly patients: PROTEKT years 1-5 (1999-2004)

The antibacterial susceptibilities of 6646 Streptococcus pneumoniae isolates collected in 38 countries from patients ≥65 years of age with community-acquired respiratory tract infections (RTIs) during years 1–5 of the PROTEKT study (1999–2004) were analysed. Rates of erythromycin resistance (36.0%), penicillin non-susceptibility (31.3%; 20.2% resistant plus 11.1% intermediately susceptible) and resistance to multiple antibacterials (37.2%) were stable over the 5 years. The most common macrolide resistance mechanism was erm(B) (61.4%); erm(B) + mef(A) strains increased from 5.4% (year 1) to 7.4% (year 5) (P = 0.037). Overall, 37.2% of isolates exhibited resistance to two or more antibacterials, including 15.9% resistant to both penicillin and erythromycin. Antibacterial resistance was highest in the Far East. Telithromycin resistance was rare (0.12%). Appropriate alternative empirical first-line therapies may be required for treating community-acquired RTIs in the elderly.     

肺炎链球菌的耐药性监测

肺炎链球菌耐药率不断上升,监测其耐药性并掌握耐药特征,有助于指导临床合理选药及控制肺炎链球菌耐药株流行.本文综述肺炎链球菌的耐药现状、相关机制及监测方法.     

Susceptibility and resistance genes to fluoroquinolones in methicillin-resistant Staphylococcus aureus isolated in 2002

The activity of six fluoroquinolones (FQs) was determined against 100 methicillin-resistant Staphylococcus aureus (MRSA) isolated in 2002 along with mutations in the grlA and gyrA genes and in the norA promoter of these isolates. Of the isolates tested, 97% had mutations in grlA and gyrA. A single mutation in grlA and gyrA resulted in a decrease of susceptibility to old generation FQs (norfloxacin, enoxacin, ciprofloxacin, fleroxacin, sparfloxacin and levofloxacin) but not to new generation FQs (gatifloxacin and moxifloxacin). Double mutations of both grlA and gyrA resulted in high-level resistance to all FQs tested. All norA mutants (15%) contained double mutations in grlA and gyrA and showed no decrease of MIC in the presence of reserpine, which is known to inhibit the drug-efflux pump. Our results showed that double mutations in grlA and gyrA were necessary for the expression of high-level resistance to new generation FQs. As different FQ-resistant mutants occur in the same PFGE type, FQ-resistant MRSA may well develop individually.