Evolution of antibiotic resistance and serogroups of Streptococcus pneumoniae over the 1997-2003 period in Brittany

At this time, many antibiotics have decreased activity against Streptococcus pneumoniae, a major agent of infectious disease. In this study, we evaluated antibiotic susceptibility and serogroups of strains isolated from bacteraemia, meningitis and acute otitis media in adults and children over the 1997-2003 period in Brittany, France. In 2003, 62% of the isolates were not susceptible to penicillin and 11% were fully resistant. The prevalence of erythromycin resistance was 63%. Resistance rates were higher among isolates recovered from children than adults. Serogroups 19 and 14 were the most frequently isolated, especially the 19 one among children. The emergence of this serogroup might be a consequence of the use of heptavalent conjugate vaccine introduced in 2001 in France. Future surveillance after vaccination will be needed to detect emerging serogroups and resistance among S. pneumoniae.     

Evolution of Streptococcus pneumoniae serotypes and antibiotic resistance in Belgium—update (1994–98)

Objective To follow the evolution of capsular types and resistance of Streptococcus pneumoniae , isolated from deep sites.
Methods More than 100 Belgian laboratories permanently collect S. pneumoniae strains isolated from puncture specimens (blood, cerebrospinal fluid, middle ear fluid, etc.) and forward them to the reference center in Leuven, in order to determine the capsular serogroups and types (SGTs) and their resistance.
Results From 1994 to 1998, the 5486 S. pneumoniae strains examined belonged to 39 of the 46 currently identified SGTs. The 10 most frequent SGTs accounted for 78.9% of the isolates, and 97% of all isolates belonged to SGTs included in the 23-valent vaccine. Overall mortality of patients with pneumococcal bacteremia or meningitis was 9.7%, and 23.8% in patients over 80 years. From 1994 to 1998, resistance to penicillin (P) increased from 7.6% to 14.2%, to tetracycline (T) from 14.9% to 28.0%, and to erythromycin (E) from 22.9% to 31%. Triple resistance (PTE) increased from 0.9% in 1994 to 6.6% in 1998. Five SGTs (6, 9, 14, 19 and 23) accounted for 50% of the isolates, but for > 90% of the penicillin-resistant or erythromycin-resistant isolates.
Conclusions Resistance of S. pneumoniae to penicillin, erythromycin and tetracycline is steadily increasing and is concentrated in five serotypes included in the 23-valent pneumococcal vaccine. Increasing resistance and high mortality of invasive infections are an incentive to vaccinate vulnerable groups.     

The role of murMN operon in penicillin resistance and antibiotic tolerance of Streptococcus pneumoniae

The recently identified murMN operon is essential for the production of branched-structured muropeptides in the cell wall and also for the expression of the resistant phenotype in penicillin-resistant strains of Streptococcus pneumoniae. The purpose of studies described in this communication was to understand better the role of murMN in penicillin resistance. Deletion of murM in the penicillin-resistant strain Pen6, which causes reduction in the penicillin MIC from 6.0 to 0.03 microg/ml, was successfully complemented to recover the original high level of penicillin resistance in transformants that received functional murM alleles cloned in plasmid pLS578. Inactivation of penicillin resistance was not accompanied by any detectable change in the low affinity or abnormal molecular size pattern of the penicillin-binding proteins (PBPs) nor in the mosaic sequence of PBP2X typical of resistant strain Pen6. Exposure of strain Pen6 with inactivated murM to 0.05 microg/ml of penicillin (i.e., a concentration more than 100 times below the MIC of the parental strain) initiated a phenotypic response typical of penicillin-susceptible strains of pneumococci: inhibition of growth followed by rapid and extensive loss of viability and lysis. Unexpectedly, inactivation of murMN also caused hypersensitivity to lysis by low concentrations of a variety of cell wall active antibiotics such as fosfomycin, D-cycloserine, and nisin, suggesting that the murMN operon may perform an important regulatory role in the control of the irreversible antimicrobial effects of cell wall inhibitors.     

Drawbacks of antibiotic susceptibility of Streptococcus pneumoniae

During 10 years penicillin resistance among clinical isolates of S. pneumoniae was more or less stable. The cumulative proportion of penicillin non susceptible S. pneumoniae (PNSP) was 13.0%; 7.2% when isolates with MIC = 2 mg/l were considered. Among PNSP only 2 strains were isolated from sterile body fluids, one having MIC >3.84 mg/l. Lack of susceptibility to cotrimoxazole was 38.4%. All isolates were susceptible to ceftriaxone, levofloxacin, moxifloxacin, and quinupristin-dalfopristin.     

Serotyping and antibiotic resistance of Streptococcus pneumoniae isolated from pediatric infections in central Greece

Objective: To determine the distribution of serogroups/serotypes and antibiotic resistance pattern of Streptococcus pneumoniae isolated from pediatric infections in central Greece.
Methods: In total, 306 S. pneumoniae strains isolated from children, aged from 18 days to 14 years (median 18 months), during a 21-month period, from different specimen sources, were studied. Susceptibility testing was carried out by the Kirby-Bauer method and by the Etest, and serotyping by the Quellung reaction.
Results: Of the S. pneumoniae isolates, 3.9% were highly resistant to penicillin (PR), while 17.6% were intermediately resistant (IPR). PR and IPR isolates were found to be, in general, more resistant to other antibiotics than penicillin-susceptible isolates. The PR and IPR isolates belonged to the serogroup/serotypes 19, 23, 9, 6 and 14 (in descending order of frequency). The penicillin-susceptible isolates belonged to 20 different groups/serotypes, the most common being 19, 6, 14, 9, 3, 23 and 1 (in descending order of frequency). Serogroup 23 was often found to be multiresistant.
Conclusions: Resistance to penicillin in S. pneumoniae isolates is relatively low and differs according to the specimen type. All the pneumococcal serogroups/serotypes isolated from the children were found to be included in the 23-valent polysaccharide vaccine. Most of the children with a pneumococcal infection, however, were less than 2 years old and could not be protected by the existing vaccine.     

青岛地区部分医院2005-2008年肺炎链球菌的耐药性分析

目的 监测青岛地区肺炎链球菌的耐药性,为临床合理应用抗菌药物提供依据.方法 采集青岛地区部分医院2005年1月到2008年12月门诊与住院感染患者呼吸道、血液、脑脊液等标本,培养、分离和鉴定肺炎链球菌.根据NCCLS的推荐,采用琼脂微茸稀释法测定分离出的231株肺炎链球菌对11种常用抗菌药物的耐药性,分析耐药趋势及年龄差异.结果 231株肺炎链球菌对青霉素不敏感率为23.38%[耐青霉素肺炎链球菌(PRSP):9.52%;低耐青霉素肺炎链球菌(PISP):13.85%].对头孢噻肟耐药率最低为9.96%(23/231),其次阿莫西林为12.55%(29/231).对红霉素耐药率最高为90.48%(209/231).14岁以下患者PRSP检出率为27.91%(12/43),明显高于成人的PRSP检出率5.38%(10/186).结论 本地区PRSP检出率较2004年前明显增加,并有逐年增加的趋势,肺炎链球菌的耐药性也有逐年上升的趋势.本地区对感染低耐青霉素肺炎链球菌的患者头孢噻肟、阿莫西林可为首选药物.     

Plasmid mediated antibiotic resistance in Klebsiella pneumoniae

Klebsiella pneumoniae species (108) isolated from tertiary care hospitalized patients were investigated for antibiotic resistance patter. 74% isolates were from urine, 13.5% from pus, 4.5% from blood and 8% from sputum. The resistance pattern of the organisms to various antibiotics were as follows: ampicillin 93.3%, cefotaxime 70%, ceftazidime 81%, gentamicin 68.5%, amikacin 63.75%, netilmicin 74%, norfloxacin 55%, ofloxacin 53%, chloramphenicol 82%, tetracycline 85%, sulphamethoxazole 96%, trimethoprim 94%. 2-4 drug resistance was found in 34.5%, 5-8 drug resistance was in 25.1% and 9-12 drug resistance was found in 40.4% of strains. Out of 65 strains, 25 strains could be successfully conjugated. Common drugs which were transferred to transconjugants were sulphamethoxazole, trimethoprim, gentamicin, netilmicin, amikacin, chloramphenicol, tetracycline, ampicillin, cefotaxime and ceftazidime. A large plasmid of 98.7% kb could be demonstrated in these strains by alkali denaturation method and agarose gel electrophoresis.     

转座子介导的肺炎链球菌耐药水平传播机制

目的 探索转座子介导的耐药基因水平转移在肺炎链球菌(Streptococcus pneumoniae,Sp)耐药传播中的作用.方法 采用长片段聚合酶链反应(long and accurate PCR,LA-PCR)、DNA序列分析、Southern blot、脉冲场凝胶电泳(PFGE)等方法 分析3株不同遗传背景的Sp中转座子的种类、结构,用转化实验分析不同菌株之间耐药性转移方式.结果 (1)Sp中携带mefE的mega元件插入到接合转座子Tn916上形成复合转座子Tn2009-like,其序列与Tn2009具有99%同源性,染色体插入位点完全不同.(2)临床分离的多重耐药Sp(ET86)染色体184 kb和155 kb片段上同时携带Tn1545、Tn917和Tn2009-like,体现出携带耐药决定子的遗传元件集中分布的趋势.另外2株不同耐药表型的Sp分别携带1或2种转座子.(3)转座子上耐药基因可通过转化转移.结论 Sp染色体上转座子可捕获其他耐药元件形成复合转座子,且不同的转座子可在染色体上集中分布、协同作用,促进耐药性的传播和进化.     

Detection of tetracycline resistance in Streptococcus pneumoniae.

Bacteriological details are given of a patient with chronic purulent bronchitis, who was being followed up during a survey of relapse in chronic bronchitis. A strain of Streptococcus pneumoniae, serotype 10, was isolated from the sputum over a period of six months, followed by a type 47A strain and later a type 28 strain. The patient was receiving prophylactic treatment with tetracycline throughout. The type 10 strain was sensitive to tetracycline in vitro by both the disc diffusion and doubling dilution sensitivity tests and mice infected with this strain were protected by tetracycline. In contrast, both the type 47A and type 28 strains were sensitive by the disc diffusion technique, but showed a low degree of tetracycline resistance by the doubling dilution method; mice infected with both these strains were not protected by tetracycline.     

Streptococcus pneumoniae endophthalmitis: a study of 36 cases with special reference to antibiotic resistance and treatment options

Patients (n = 36) diagnosed with pneumococcal endophthalmitis from six Spanish hospitals between 1986 and 2004 were studied retrospectively. The diagnosis was based on clinical findings, ophthalmological examination, and isolation of Streptococcus pneumoniae from vitreous and/or aqueous humours of 19 patients (definite diagnosis), and from other ocular specimens of 17 patients (probable diagnosis). The mean (+/- SD) age was 69.3 (+/- 16.5) years (range 1.5-89 years), and 20 (55.5%) patients were male. The origin of endophthalmitis was considered exogenous for 34 (94.5%) patients. The most common predisposing factors were previous ocular surgery (n = 25, 69.4%), ocular trauma (n = 5, 13.9%), and close-to-eye radiotherapy (n = 3, 8.3%). Eleven (30.5%) patients underwent evisceration as the first therapeutic measure (primary evisceration), and evisceration was performed after antibiotic treatment failure (secondary evisceration) for six (16.7%) patients. Primary evisceration was performed more commonly (63.6%) during 1998-2004, while secondary evisceration was only performed during 1986-1997. Eighteen (50%) patients received intra-vitreous antibiotics (mainly vancomycin), and 31 (86.1%) patients were given systemic antibiotic therapy. The most frequent pneumococcal serogroups isolated were 6, 19, 9, 15 and 23. Pulsed-field gel electrophoresis analysis of 23 isolates revealed that four belonged to the international clones Spain(23F)-1, Spain(6B)-2, Spain(9V)-3 and Sweden(15A)-25. Non-susceptibility rates (i.e., intermediately-resistant and resistant) were: co-trimoxazole, 44.8%; penicillin, 33.3%; tetracycline, 31.0%; erythromycin, 21.9%; chloramphenicol, 17.9%; rifampicin, 7.4%; cefotaxime, 5.9%; and levofloxacin, 0%. Although uncommon, pneumococcal endophthalmitis is a medical emergency because of the often aggressive clinical course, poor visual outcome and need for evisceration in a large proportion of patients.     

The antimicrobial resistance profile of Streptococcus pneumoniae

Antibacterial resistance in pneumococci is increasing worldwide, primarily against β -lactams and macrolides. Understanding the role played by molecular determinants of resistance, transformation and competence in the evolution of Streptococcus pneumoniae is important in addressing this trend. Data from the Prospective Resistant Organism Tracking and Epidemiology for the Ketolide Telithromycin (PROTEKT) study indicate that about 40% of pneumococci display multidrug-resistant phenotypes (resistance to three or more antibiotics), with highly variable prevalence rates observed in different countries. Alterations in the structure of six penicillin-binding proteins (PBPs) have been described in S. pneumoniae (1a, 1b, 2x, 2a, 2b and 3), enabling resistance to β -lactam antibiotics. Mechanisms conferring macrolide resistance include resistance mediated through the erm (B) gene, which results in macrolide–lincosamide–streptogramin B resistance, or through the mef (A) gene, which encodes an antibiotic efflux pump. Another variant, mef (E), is also expressed in S. pneumoniae ; both mef (A) and mef (E) variants are associated with strains belonging to serotype 14. In addition to the selection pressure resulting from misuse of antibiotics, widespread vaccination programmes may contribute to changing pneumococcal epidemiology. Since the introduction of the seven-valent pneumococcal conjugate vaccine (PCV7), the rate of invasive pneumococcal disease due to PCV7 serotypes has declined significantly in many countries, but some countries have reported an increase in non-PCV7 serotypes. This phenomenon, termed 'replacement', is associated with certain pneumococcal serotypes or clones (e.g. serotype 19A). Whether novel 'vaccine escape recombinant' pneumococcal strains are emerging or changes in distribution are part of a secular cycle remains to be determined.     

Streptococcus pneumoniae: lack of emergence of pristinamycin resistance]

Since 1997, a few studies have been published suggesting the emergence of clinical isolates of Streptococcus pneumoniae resistant to pristinamycin. Such results were not confirmed by recent studies from different investigators using reference techniques for the determination of susceptibilities, which is in accordance with the low probability of emergence of resistance to this antibiotic in vitro. Discrepancies are encountered with macrolide-resistant strains and may be due to the type of method used for susceptibility testing (agar-diffusion test), the final inoculum used in this technique, or the recent lowering of breakpoint for susceptibility. On the contrary, correlation between reference techniques and commercial galleries using liquid medium is excellent. Despite 35 years of exerting selective pressure, the in vitro activity of pristinamycin remains constant against clinical isolates of S. pneumoniae.     

Evolutionary barriers to quinolone resistance in Streptococcus pneumoniae

It is assumed that bacteria always pay a significant physiological price for the acquisition of resistance to antibiotics. To test whether this was the case for a strain of Streptococcus pneumoniae that develops resistance to fluoroquinolone antibiotics, we selected resistance to these agents in a wild-type strain and measured their fitness in comparative growth experiments. The relative growth rate of a mutant strain selected on ciprofloxacin (parC Serine 79 to Tyrosine) was compared with its susceptible isogenic parent and no significant deficit was found (relative fitness 1.15 95% C.I. +/- 0.2.). A double mutant, however, had a relative fitness of 0.81 (parC Serine 79 to Tyrosine gyrA Serine 81 to Tyrosine). Mutant strains selected on gemifloxacin had only a modest increase in minimum inhibitory concentration; thus, second-round mutants were competed with a first-round gyrA Serine 81 to Tyrosine or the susceptible isogenic parent. The growth rate of three double-mutant strains parC Serine 79 to Tyrosine gyrA Serine 81 to Phenylanine, parC Serine 79 to Tyrosine, and Asparagine 83 to Phenylalanine were similar to the isogenic susceptible parent 1.16 (95% C.I. +/- 0.17), 0.99 (95% C.I. +/- 0.05), and 0.95 (95% C.I. +/- 0.05), respectively. These data suggest that mutation in the parC and gyrA genes may, on some occasions, not be associated with a physiological deficit.     

Mechanisms and spread of fluoroquinolone resistance in Streptococcus pneumoniae

The development of fluoroquinolones (FQs) with enhanced activity against Streptococcus pneumoniae is a potential advance in the treatment of pneumococcal infections, particularly those due to beta-lactam-resistant pneumococci. However, FQ-resistant clinical isolates selected by the older FQs have already been reported, with mutation(s) in both FQ targets conferring cross-resistance to newer FQs. It is likely that recombinational events between topoisomerase genes from related species of streptococci contribute to the spread of FQ resistance in S. pneumoniae. A scenario resembling that of the worldwide spread of resistance to beta lactams should be anticipated.     

Antimicrobial resistance in Streptococcus pneumoniae: a growing universal concern.

Streptococcus pneumoniae is the most common cause of bacterial pneumonia, otitis media, bacteremia, and meningitis in infants, children, and immunocompromised and splenectomized patients. After the introduction of penicillin in 1940, pneumococci were regarded as uniformly sensitive to minimal inhibitory concentrations (less than or equal to 0.05 microgram/mL). This idea persisted until 1967, when the first strain showing increased resistance to penicillin was isolated. Pneumococci with intermediate penicillin resistance recovered from different geographic areas have minimum inhibitory concentrations of 0.1 to 1.0 microgram/mL. In 1977, however, resistant strains were isolated with minimum inhibitory concentrations of 2 to 10 micrograms/mL; subsequently, strains resistant to other antibiotics including tetracycline, sulfonamides, erythromycin, lincomycin, chloramphenicol, clindamycin, streptomycin, and rifampin have also been reported. The authors emphasize the need for continued surveillance of pneumococcal isolates and recommend sensitivity testing of all isolates to penicillin.     

Emergence of optochin resistance among Streptococcus pneumoniae in Portugal

In most clinical microbiology laboratories optochin susceptibility is used in the screening and identification of Streptococcus pneumoniae. We report the characterization of 32 optochin-resistant S. pneumoniae strains from 10 laboratories that constituted 3.2% of all isolates recovered in 2005 in 30 laboratories in Portugal. Resistant isolates consisted of bile-soluble optochin-susceptible and optochin-resistant subpopulations with identical antimicrobial susceptibility patterns, capsular types and pulsed-field gel electrophoresis (PFGE) profiles. The most frequent serotypes--1, 19A, 11A, 3, 8, and 15A--were all common serotypes present in infection and colonization isolates in the country. The PFGE profiles of the 32 isolates corresponded to those of previously identified clones and confirmed that the emergence of these strains could not be attributed to clonal expansion. Clinical laboratories must be aware that optochin-resistant pneumococci are presently circulating in the community. Because accurate identification of S. pneumoniae is essential for correct diagnosis and adequate therapy of patients, we recommend that at least the bile solubility test should be routinely performed in cases of suspected pneumococcal etiology, even if the isolates are optochin-resistant.     

Inferring the potential success of pneumococcal vaccination in Italy: serotypes and antibiotic resistance of Streptococcus pneumoniae isolates from invasive diseases

To evaluate the potential impact of antipneumococcal vaccination in Italy, Streptococcus pneumoniae isolates from invasive disease were collected from 65 laboratories in the years 1997-2000. Of the 503 isolates examined, 15% were from children <5 years and 34% from adults > or = 65 years. The most frequent serogroups were, in ranking order, 14, 19, 6, and 23. Overall, 93.8% of the isolates belonged to serogroups enclosed in the 23-valent polysaccharide vaccine. Among children isolates, serotypes 14, 6B, and 23F comprised 60% of the isolates; overall, 72% of the isolates belonged to serotypes included in the heptavalent conjugate vaccine. Penicillin nonsusceptible isolates (10%) belonged to a limited number of serogroups, being more common in serogroups 19 and 9 and in the nonvaccine serogroups 24 and 35. Erythromycin-resistant isolates (29%) belonged to several serogroups, more frequently to serogroups 14, 6, and 19. Both vaccines are potentially able to prevent the majority of resistant infections in the respective age groups in Italy.