Antimicrobial susceptibility patterns and genomic diversity in strains of Streptococcus pyogenes isolated in 1978-1997 in different Brazilian cities

Cellular Growth Arrest and Efflux Pumps Are Associated With Antibiotic Persisters in Streptococcus pyogenes Induced in Biofilm-Like Environments

Streptococcus pyogenes (group A Streptococcus-GAS) is an important pathogen for humans. GAS has been associated with severe and invasive diseases. Despite the fact that these bacteria remain universally susceptible to penicillin, therapeutic failures have been reported in some GAS infections. Many hypotheses have been proposed to explain these antibiotic-unresponsive infections; however, none of them have fully elucidated this phenomenon. In this study, we show that GAS strains have the ability to form antimicrobial persisters when inoculated on abiotic surfaces to form a film of bacterial agglomerates (biofilm-like environment). Our data suggest that efflux pumps were possibly involved in this phenomenon. In fact, gene expression assays by real-time qRT-PCR showed upregulation of some genes associated with efflux pumps in persisters arising in the presence of penicillin. Phenotypic reversion assay and whole-genome sequencing indicated that this event was due to non-inherited resistance mechanisms. The persister cells showed downregulation of genes associated with protein biosynthesis and cell growth, as demonstrated by gene expression assays. Moreover, the proteomic analysis revealed that susceptible cells express higher levels of ribosome proteins. It is remarkable that previous studies have reported the recovery of S. pyogenes viable cells from tissue biopsies of patients presented with GAS invasive infections and submitted to therapy with antibiotics. The persistence phenomenon described herein brings new insights into the origin of therapeutic failures in S. pyogenes infections. Multifactorial mechanisms involving protein synthesis inhibition, cell growth impairment and efflux pumps seem to play roles in the formation of antimicrobial persisters in S. pyogenes.

Prevalence and Characterization ofStreptococcus pyogenesClinical Isolates from Different Hospitals and Clinics in Mansoura

Streptococcus pyogenesare associated with many bacterial diseases in both humans and animals and are capable of causing a multitude of human diseases.S. pyogenesisolates were identified by their bacitracin sensitivity, positivespy1258detection, and positive GAS latex agglutination. Different isolates were typed serotypically and genotypically by BOX-PCR. Different virulence factors were identified inS. pyogenesisolates. In addition, antimicrobial resistance was tested to eleven different antibiotics. Furthermore, the resistance mechanisms were determined phenotypically by the disc diffusion method. Finally, the correlation between both molecular and serotypes identified and the profile of virulence factors and clinical and geographical sources was determined for all isolates. Thirty-eightS. pyogenesisolates were collected from different clinical sources. Resistance testing indicated high resistance to mostly used antibiotics except amoxicillin/clavulanic acid, amoxicillin, and ampicillin. Serotyping results indicated five different serotypes, M1, M2, M3, M4, and M6, inS. pyogenesisolates, while six isolates were identified as untypeable. In addition, positive PCR results identified most of the tested SAgs genes in whichspeJgene was mostly identified followed byspeI, speC,andssagenes being identified in 81.6%, 63.3%, 60.5%, and 60.5%, respectively. However,speHwas the least detected. In contrast,speL, speM, andsmeZgenes could not be detected in all tested isolates. Finally, BOX-PCR molecular typing was a more effective clustering method when compared to the serotyping method in allS. pyogenes.In conclusion, the isolates in this study were highly resistant to mostly used antibiotics. M1 was the most identified serotype. No significant association was found between serotypes, BOX-PCR cluster groups, and SAgs genes profiles. However, by the application of BOX-PCR, effective molecular typing was obtained.

Low lineage diversity and increased virulence of group C Streptococcus dysgalactiae subsp. equisimilis

Introduction. In some species, the population structure of pathogenic bacteria is clonal. However, the mechanisms that determine the predominance and persistence of specific bacterial lineages of group C Streptococcus remain poorly understood. In Brazil, a previous study revealed the predominance of two main lineages of Streptococcus dysgalactiae subsp. equisimilis (SDSE).Aim. The aim of this study was to assess the virulence and fitness advantages that might explain the predominance of these SDSE lineages for a long period of time.Methodology. emm typing was determined by DNA sequencing. Adhesion and invasion tests were performed using human bronchial epithelial cells (16HBE14o-). Biofilm formation was tested on glass surfaces and the presence of virulence genes was assessed by PCR. Additionally, virulence was studied using Caenorhabditis elegans models and competitive fitness was analysed in murine models.Results. The predominant lineages A and B were mostly typed as emm stC839 and stC6979, respectively. Notably, these lineages exhibited a superior ability to adhere and invade airway cells. Furthermore, the dominant lineages were more prone to induce aversive olfactory learning and more likely to kill C. elegans. In the competitive fitness assays, they also showed increased adaptability. Consistent with the increased virulence observed in the ex vivo and in vivo models, the predominant lineages A and B showed a higher number of virulence-associated genes and a superior ability to accumulate biofilm.Conclusion. These results suggest strongly that this predominance did not occur randomly but rather was due to adaptive mechanisms that culminated in increased colonization and other bacterial properties that might confer increased bacteria-host adaptability to cause disease.

Prevalence of Beta-Hemolytic Streptococci Groups A, C, and G in Patients with Acute Pharyngitis

Context:

Group A beta-hemolytic streptococci (GAS) is the most frequently isolated pathogen in acute pharyngitis. However, the role of Group C (GCS) and Group G (GGS) streptococci in disease burden is under recognized. The present study is carried out to find out the prevalence of acute pharyngitis caused by the different serogroups of streptococci and antibiotic susceptibility pattern of these streptococcal isolates.

Study and Design:

A cross sectional study.

Materials and Methods:

A total of 218 throat swabs from patients with acute pharyngitis and 82 from healthy controls were collected and processed as per standard protocol. Samples were inoculated on blood agar and Streptococcus selective agar. Isolates were identified by the conventional method and serogrouped by latex agglutination test using Remel Streptex kit.

Results:

Beta-hemolytic streptococci (BHS) were isolated from 34 (15.59%) of pharyngitis patients and 11 (13.41%) of the healthy carrier. Among pharyngitis, GAS was isolated from 20 (9.17%), GCS 7 (3.21%), and GGS 7 (3.21%) patients. Carriage rate of GAS was 6 (7.31%) and GCS, 5 (6.09%). Vancomycin (100%), amoxyclavulanic acid (90%), levofloxacin (85%), and cephotaxime (80%) were found to be most effective antibiotics. Comparatively, higher drug resistance was observed among GCS and GGS to all the drugs used in the study except for levofloxacin.

Conclusions:

Although rate of pharyngitis associated with GCS and GGS is marginally lower than GAS, their carriage rate among healthy and relative higher drug resistance emphasizes the need for periodic surveillance of infection by the different serogroups of BHS.

Disease manifestations and pathogenic mechanisms of Group A Streptococcus

Streptococcus pyogenes, also known as group A Streptococcus (GAS), causes mild human infections such as pharyngitis and impetigo and serious infections such as necrotizing fasciitis and streptococcal toxic shock syndrome. Furthermore, repeated GAS infections may trigger autoimmune diseases, including acute poststreptococcal glomerulonephritis, acute rheumatic fever, and rheumatic heart disease. Combined, these diseases account for over half a million deaths per year globally. Genomic and molecular analyses have now characterized a large number of GAS virulence determinants, many of which exhibit overlap and redundancy in the processes of adhesion and colonization, innate immune resistance, and the capacity to facilitate tissue barrier degradation and spread within the human host. This improved understanding of the contribution of individual virulence determinants to the disease process has led to the formulation of models of GAS disease progression, which may lead to better treatment and intervention strategies. While GAS remains sensitive to all penicillins and cephalosporins, rising resistance to other antibiotics used in disease treatment is an increasing worldwide concern. Several GAS vaccine formulations that elicit protective immunity in animal models have shown promise in nonhuman primate and early-stage human trials. The development of a safe and efficacious commercial human vaccine for the prophylaxis of GAS disease remains a high priority.

Disease manifestations and pathogenic mechanisms of Group A Streptococcus

Streptococcus pyogenes, also known as group A Streptococcus (GAS), causes mild human infections such as pharyngitis and impetigo and serious infections such as necrotizing fasciitis and streptococcal toxic shock syndrome. Furthermore, repeated GAS infections may trigger autoimmune diseases, including acute poststreptococcal glomerulonephritis, acute rheumatic fever, and rheumatic heart disease. Combined, these diseases account for over half a million deaths per year globally. Genomic and molecular analyses have now characterized a large number of GAS virulence determinants, many of which exhibit overlap and redundancy in the processes of adhesion and colonization, innate immune resistance, and the capacity to facilitate tissue barrier degradation and spread within the human host. This improved understanding of the contribution of individual virulence determinants to the disease process has led to the formulation of models of GAS disease progression, which may lead to better treatment and intervention strategies. While GAS remains sensitive to all penicillins and cephalosporins, rising resistance to other antibiotics used in disease treatment is an increasing worldwide concern. Several GAS vaccine formulations that elicit protective immunity in animal models have shown promise in nonhuman primate and early-stage human trials. The development of a safe and efficacious commercial human vaccine for the prophylaxis of GAS disease remains a high priority.

Streptococcus pyogenes biofilm growth in vitro and in vivo and its role in colonization, virulence, and genetic exchange

BACKGROUND

Group A streptococcus (GAS) commonly colonizes the oropharynx and nonintact skin. However, colonization has been little studied and the role of biofilm formation is unclear, as biofilm experiments to date have not been conducted under conditions that mimic the host environment.

METHODS

In this study we grew GAS biofilms on human keratinocytes under various environmental conditions and used this model to evaluate colonization, invasive disease and natural transformation.

RESULTS

GAS grown on epithelial cells, but not biofilms grown on abiotic surfaces, produced biofilms with characteristics similar to in vivo colonization. These biofilm bacteria showed a 100-fold higher bacterial burden of nasal-associated lymphoid tissue in mice than broth-grown bacteria, and were not virulent during septic infection, which was attributed in part to down-regulation of genes typically involved in localized and invasive disease. We also showed for the first time that GAS were naturally transformable when grown in biofilms and during colonization of NALT in vivo.

CONCLUSIONS

These findings provide novel model systems to study biofilm formation of GAS in vitro and in vivo, suggest an important role for biofilm formation during GAS colonization, and provide an explanation for the known genome diversity within the GAS population.

Description of macrolide-resistant and potential virulent clones of Streptococcus pyogenes causing asymptomatic colonization during 2000-2006 in the Lisbon area

The asymptomatic oropharyngeal colonization rate by Streptococcus pyogenes was 10.7% in children (901 among 8,405 children 0-16 years old) and 3.3% in adults (37 among 1,126 households of children) in the Lisbon area during 2000-2006. Macrolide-resistant S. pyogenes from children (n = 149) was variable with time: 9.8-10.7% in 2000-2002, 28.1% in 2003, 19.6-2.7% in 2004-2005 and 14.6% in 2006. Eight lineages (97.3% of isolates) were identified based on at least 80% similarity of PFGE patterns, T types, emm types and multilocus sequence types (ST). The elevated frequency of macrolide resistance was associated with M phenotype lineages I (emm12/ST36) and V (emm4, emm75/ST39 and a novel emmstMrp6 type) and with one cMLS(B) lineage IV (emm28/ST52) known to be associated with upper respiratory tract and invasive infections. Significant associations (p < 0.05) between emm type/virulence genotype were found, such as emm1/speA (+) ssa (-), emm4/ssa (+) prtF1 (+), emm12/speA (-) ssa (-). The high prevalence (>20%) of speC, prtF1 or ssa was probably caused either by clonal dissemination (speC), or to horizontal gene transfer events (prtF1 and ssa). This report contributes to a better understanding of the molecular epidemiology and evolution of macrolide-resistant S. pyogenes causing symptom-free oropharyngeal colonization. These colonizing strains carry macrolide resistance and virulence genes capable of being transferred to other bacterial species sharing the same niche.

Epidemiological markers of Streptococcus pyogenes strains in Tunisia

To further understand the epidemiology of Streptococcus pyogenes or group A streptococcus (GAS) infections in Tunisia, phenotypic and genomic markers of GAS isolates, including antibiotic susceptibility, biotypes, T and emm types and toxin gene profiles, have been characterized. A total of 103 isolates, collected between 2000 and 2006, were investigated; 47 were recovered from invasive infections, and 56 from non-invasive infections. Rates of resistance to tetracycline, erythromycin, clindamycin and rifampin were 70.8%, 4.8%, 4.8% and 0.9%, respectively. High levels of resistance to streptomycin and kanamycin were observed in 1.9% and 4.8% of isolates, respectively. Biotype 3 was most common. Twenty different T patterns were observed, with a predominance of T3/13/B3264, and 38 different emm types. In both invasive and non-invasive isolates, emm118 (9.7%), emm42 (8.7%), emm1 (7.8%), st432 (6.8%), emm28 (5.8%) and emm76 (5.8%) were the most prevalent types; emm1, emm76 and emm18 were mainly observed among invasive infections, whereas emm118 (12.5%), emm42 (10.7%) and emm28 (8.9%) were predominant among non-invasive infections. The speB gene was detected in all isolates, but there were variable frequencies of speA, speC and ssa (20.3%, 32% and 25.2% respectively). Significant associations of emm1, emm18 and emm3 with speA and of emm4 and st432 with ssa were found. This first report from Tunisia revealed a unique emm distribution of GAS that differs from those of other regions. This information on the distribution of such emm types will be useful for the development of an appropriate vaccine in a country where the incidence of rheumatic fever remains high.

Antibiotic resistance and molecular analysis of Streptococcus pyogenes isolated from healthy schoolchildren in China

Streptococcus pyogenes are highly prevalent bacterial pathogens, especially in school-aged children. However, the characteristics of asymptomatic carriers vary geographically in different countries. We aimed to investigate S. pyogenes isolated from healthy schoolchildren in China. From 2007 to 2008, a total of 94 S. pyogenes isolates were obtained from healthy schoolchildren in Beijing and Chongqing, China. Antimicrobial susceptibility testing, determination of macrolide resistance genes (ermB, ermA and mefA), emm genotyping, pulsed-field gel electrophoresis (PFGE), and multilocus sequence typing (MLST) were performed. The resistance rate to macrolides was 96.8% and to tetracycline was 92.6%. All macrolide-resistant isolates exhibited constitutive resistance; 77 isolates (84.6%) had the ermB gene, while 14 isolates (15.4%) had the ermA gene. Among the macrolide-resistant isolates, the most frequent emm type was emm12 (51.6%), followed by emm22 (14.3%) and ST1815 (8.8%). PFGE analysis revealed 12 different patterns, with a given pattern having the same sequence type (ST) by MLST and the same emm type. In conclusion, the rate of macrolide resistance to S. pyogenes is currently very high in China. This is due primarily to the dissemination of a limited number of clones.

Otimizando o diagnóstico para o tratamento adequado das principais infecções agudas em otorrinopediatria: tonsilite, sinusite e otite média

As sinusites, otites médias agudas e tonsilites são muito freqüentes em crianças. A maioria dessas infecções é causada por vírus, mas em geral, elas são tratadas com antibióticos. O uso inapropriado de antibióticos favorece a seleção, crescimento e disseminação de bactérias resistentes que colonizam as vias respiratórias, atingindo toda a comunidade. A emergência de bactérias resistentes dificulta os tratamentos das infecções respiratórias, sendo essencial desenvolver estratégias efetivas para restringir o uso de antibióticos sem prejudicar as crianças que realmente precisam desses medicamentos. OBJETIVO: Analisar os resultados de estudos randomizados e controlados sobre critérios clínicos e laboratoriais utilizados para diagnóstico e tratamento das tonsilites, sinusites e otites. MÉTODOS: Levantamento dos estudos randomizados e controlados sobre o tema, publicados no MEDLINE e SCIELO, de 2000 a 2006. CONCLUSÕES: Como a maioria dessas infecções evolui bem sem antibióticos, deve-se evitar o uso desses medicamentos a menos que a criança pertença aos grupos de alto risco para complicações ou apresente persistência ou piora dos sintomas com tratamento sintomático. É necessário que os médicos e leigos conheçam melhor a evolução natural das infecções respiratórias agudas e que seja garantido o acesso das crianças a serviços médicos de boa qualidade para orientação e reavaliação, quando necessária.

Optimizing the Management of the Main Acute Infections in Pediatric ORL: Tonsillitis, Sinusitis, Otitis media

Sinusitis, acute otitis media and tonsillitis are very frequent in children. Most of these infections are caused by viruses, but are generally treated with antibiotics. Inappropriate use of antibiotics favors the selection, growth and spread of resistant bacteria; these bacteria colonize the airways and affect the entire community. With the emergence of antibiotic-resistant bacteria, respiratory infections have become more difficult to treat. Effective strategies are needed to restrict the use of antibiotics without harming children that truly need these drugs.

Aim

to present a critical analysis of the results of randomized and controlled studies on clinical and laboratory criteria used in diagnosing and treating tonsillitis, sinusitis and otitis.

Methods

a review of randomized and controlled studies about these conditions published in MEDLINE and SCIELO from 2000 to 2006.

Conclusions

Given that most of these infections progress favorably without antibiotics, the use of these drugs should be avoided unless the child belongs to a high risk group for complications, or symptoms persist or worsen with despite symptomatic treatment. Physicians and laypersons should have better knowledge about the natural evolution of acute respiratory infections.

Antibiotic resistant beta-hemolytic streptococci

OBJECTIVE

An antibiotic-sensitivity study was conducted on 117 strains of group A streptococcus (GAS), 60 strains of group G streptococcus (GGS) and 20 strains of group C streptococcus (GCS) in order to understand current resistance trends.

METHODS

All strains were tested by the Kirby Bauer disc diffusion method to 15 antibiotics. Resistant strains were confirmed by testing the minimum inhibitory concentration (MIC) of antibiotics by broth dilution technique.

RESULTS

Among GAS, highest resistance was observed to tetracycline (27.4%) and erythromycin (16.2%). The GGS and GCS tested, showed similar resistance patterns.

CONCLUSION

All beta-hemolytic streptococci were susceptible to penicillin, amoxycillin, cephalosporins and linezolid. Resistance to erythromycin, tetracycline, clindamycin, chloramphenicol, and quinolones is emerging.

Promoter and transcription analysis of penicillin-binding protein genes in Streptococcus gordonii

An optimally cross-linked peptidoglycan requires both transglycosylation and transpeptidation, provided by class A and class B penicillin-binding proteins (PBPs). Streptococcus gordonii possesses three class A PBPs (PBPs 1A, 1B, and 2A) and two class B PBPs (PBPs 2B and 2X) that are important for penicillin resistance. High-level resistance (MIC, > or =2 microg/ml) requires mutations in class B PBPs. However, although unmutated, class A PBPs are critical to facilitate resistance development (M. Haenni and P. Moreillon, Antimicrob. Agents Chemother. 50:4053-4061, 2006). Thus, their overexpression might be important to sustain the drug. Here, we determined the promoter regions of the S. gordonii PBPs and compared them to those of other streptococci. The extended -10 box was highly conserved and complied with a sigma(A)-type promoter consensus sequence. In contrast, the -35 box was poorly conserved, leaving the possibility of differential PBP regulation. Gene expression in a penicillin-susceptible parent (MIC, 0.008 microg/ml) and a high-level-resistant mutant (MIC, 2 microg/ml) was monitored using luciferase fusions. In the absence of penicillin, all PBPs were constitutively expressed, but their expression was globally increased (1.5 to 2 times) in the resistant mutant. In the presence of penicillin, class A PBPs were specifically overexpressed both in the parent (PBP 2A) and in the resistant mutant (PBPs 1A and 2A). By increasing transglycosylation, class A PBPs could promote peptidoglycan stability when transpeptidase is inhibited by penicillin. Since penicillin-related induction of class A PBPs occurred in both susceptible and resistant cells, such a mutation-independent facilitating mechanism could be operative at each step of resistance development.

Superantigen gene profile, emm type and antibiotic resistance genes among group A streptococcal isolates from Barcelona, Spain

Group A streptococcus (GAS) has been described as an emerging cause of severe invasive infections. A retrospective hospital-based study was conducted, including GAS isolates causing invasive or non-invasive infections from January 1999 to June 2003 in Barcelona. Demographic and clinical information on the invasive cases was obtained from medical files. GAS isolates collected from 27 patients with invasive infections and 99 patients with non-invasive infections were characterized by emm type and subtype, superantigen (SAg) gene profile (speA–C, speF–J, speL, speM, ssa and smeZ), allelic variants of speA and smeZ genes, antibiotic susceptibility and genetic resistance determinants. The most prevalent emm type was emm1 (17.5 %), followed by emm3 (8.7 %), emm4 (8.7 %), emm12 (7.1 %) and emm28 (7.1 %). The smeZ allele and SAg gene profiles were closely associated with the emm type. The speA2, speA3 and speA4 alleles were found in emm1, emm3 and emm6 isolates, respectively. Overall, 27.8, 25.4 and 11.9 % of isolates were resistant to erythromycin, tetracycline or both agents, respectively. Reduced susceptibility to ciprofloxacin and levofloxacin (MIC 2–4 μg ml−1) was found in 3.2 % of isolates. mef(A)-positive emm types 4, 12 and 75, and erm(B)-positive emm types 11 and 25 were responsible for up to 80 % of the erythromycin-resistant isolates. No significant differences in emm-type distribution, SAg gene profile or resistance rates were found between invasive and non-invasive isolates. The SAg and antibiotic resistance genes appeared to be associated with the emm type and were independent of the disease type.

Group A Streptococci from carriage and disease in Portugal: evolution of antimicrobial resistance and T antigenic types during 2000-2002

In this study, we analyzed the antimicrobial resistance properties and T antigenic types of 511 isolates collected in Lisbon district, Portugal, from throat swabs of healthy subjects (n=341), during 2000-2002 and from diverse infection sites (n=170) of outpatients and inpatients, during 1999-2002. Erythromycin resistance was higher in tonsillitis/pharyngitis (27.4%) and skin infection isolates (21.1%), than in carriage and invasive isolates (<or=10%). Differences in erythromycin resistance among children and adults were noticed only for carriage isolates (9.3% in children and 21.1% in adults). Most erythromycin-resistant isolates from carriage (82.4%) and tonsillitis/pharyngitis (71.9%) showed the M phenotype. All M phenotype isolates (n=53) carried mef(A), whereas all MLS(B) phenotype isolates (n=19) carried erm(B) and not erm(A). Resistance to tetracycline [mediated by tet(M) in most isolates] was <or=6% in tonsillitis/pharyngitis and carriage isolates, 36.8% in skin infection isolates, and 44.1% in invasive isolates. The M phenotype increased since 2000, linked to a decrease of tetracycline resistance, and was predominantly associated with T1 in 2000-2001 and T12 in 2002 among carriage isolates, and with T8/25/Imp19 through 2000-2002 among tonsillitis/pharyngitis isolates. The majority (53%) of the tetracycline-resistant invasive isolates were nontypable. All isolates were susceptible to penicillin and chloramphenicol. This study showed that tetracycline and macrolide resistance frequency and phenotypes differ among GAS from various origins and changed over time. Moreover, T typing suggested that most drug-resistant isolates causing oropharyngeal carriage are distinct from the majority of isolates causing noninvasive and invasive infection.

Survey of phenotypic and genetic features of streptococcus pyogenes strains isolated in Northwest Italy

Streptococcus pyogenes (group A Streptococcus [GAS]) is an important pathogen whose virulence is related to the production of exotoxins and the presence of particular surface components. One hundred eighty-two GAS strains were collected in northwestern Italy between 1994 and 2002 and analyzed for phenotypic characteristics (opacity factor, proteolyic activity, and antimicrobial susceptibility) and by polymerase chain reaction for the presence of genes responsible for the production of exotoxins implicated in pathogenesis speA and speF and of prtF(1) (encoding fibronectin-binding protein F1). All strains were speF positive and 19.2% were speA positive and prtF(1) negative, whereas the prtF(1) gene was identified in 39.5% of the other strains. Of these, approximately half revealed the same pulse-field gel electrophoresis (PFGE) pattern but differed in both speA gene and macrolide resistance.

Increased serum resistance in Klebsiella pneumoniae strains producing extended-spectrum beta-lactamases

The aim of this study was to determine whether there is an association between serum resistance, O serotypes, and the production of extended-spectrum beta-lactamases (ESBLs) in Klebsiella pneumoniae. Ninety ESBL-producing and 178 non-ESBL-producing K. pneumoniae isolates gathered in five European countries were O serotyped and tested for sensitivity to the serum's bactericidal effect. The frequency of serum-resistant isolates was higher among ESBL-producing strains (30%; 27/90 isolates) than among non-ESBL-producing strains (17.9%; 32/178 isolates) (P = 0.037; odds ratio [OR] = 1.96; 95% confidence interval [95% CI] = 1.08 to 3.53). Although O1 was the most common O serotype in both Klebsiella groups, its frequency among ESBL-producing strains was significantly higher (59%; 53/90 isolates) than among non-ESBL producers (36%; 64/178 isolates) (P = 0.0006; OR = 2.5; 95% CI = 1.52 to 4.29). Furthermore, the prevalence of the O1 serotype was higher among serum-resistant strains of both ESBL-producing (74%; 20/27isolates) and non-ESBL producers (75%; 24/32 isolates) than among serum-sensitive ESBL producers (52.4%; 33/63 isolates) and non-ESBL producers (27.4%; 40/146 isolates). Serum resistance among ESBL-producing strains (36%; 17/47 isolates) versus non-ESBL-producing strains (16%; 27/166 isolates) was also significantly higher after the exclusion of clonal strains (P = 0.0056; OR = 2.9; 95% CI = 1.41 to 6.01). Sixteen ESBL types were detected, among which the frequency of serum resistance was significantly lower among the SHV-producing strains (9/48 isolates) than among the TEM producers (16/35 isolates) (P = 0.016; OR = 3.65; CI = 1.3 to 9.7). Curing ESBL-coding plasmids did not influence the serum resistance of the bacteria; all six plasmid-cured derivatives maintained serum resistance. The present findings suggest that ESBL-producing strains have a greater pathogenic potential than non-ESBL-producing strains, but the linkage between O serotypes, serum resistance, and ESBL production remains unclear at this stage.

Prevalence of group A streptococcal carriers in asymptomatic children and clonal relatedness among isolates in Malatya, Turkey

In our study, the prevalence of nasopharyngeal Streptococcus pyogenes was 130 (14.3%) of 909 healthy children. Isolates were found to be susceptible to all antibiotics tested. Pulsed-field gel electrophoresis and arbitrarily primed PCR revealed that 34 (32.4%) of the 105 isolates and 41 (40.6%) of the 101 isolates typed, respectively, were clonally indistinguishable.

Impairment of respiratory burst in polymorphonuclear leukocytes by extended-spectrum beta-lactamase-producing strains of Klebsiella pneumoniae

The ability of extended-spectrum beta-lactamase (ESBL)-producing and non-ESBL-producing Klebsiella pneumoniae strains to induce a respiratory burst in polymorphonuclear leukocytes (PMNLs) was investigated. Ninety ESBL-producing and 178 non-ESBL-producing Klebsiella pneumoniae isolates were serotyped and their ability to induce a respiratory burst in PMNLs tested by monitoring the cells' chemiluminescence (CL) response. The percentage of isolates inducing high levels of CL response (CL>75%) was significantly higher among non-ESBL producers (52%) than among ESBL producers (32.2%) ( P<0.0001; OR=3.396; 95%CI=2.036-5.664). The median CL response was significantly higher among the non-ESBL producers (76.9%) than among the ESBL producers (52.6%) ( P=0.034). The two groups did not differ in their ability to resist intracellular killing by PMNLs ( P>0.05), with strains inducing high levels of CL response having significantly lower survival rates (31.8% vs. 42.4%) than strains inducing low levels of CL response (164% vs. 200%) ( P<0.01). The frequencies of the K2 and the K25 serotypes were significantly higher among ESBL-producing strains (17.8% and 22.2%, respectively) than among the non-ESBL producers (6.2% and 1.7%, respectively) ( P=0.0057 and P<0.0001). Of the 77 Klebsiella K serotypes, 71 were detectable among the non-ESBL producers, but only 24 were detectable among the ESBL producers. ESBL-producing Klebsiella pneumoniae strains might have a greater pathogenic potential by virtue of their ability to escape the phagocytic activity of PMNLs.