MLS resistance phenotypes and mechanisms in beta-haemolytic group B, C and G Streptococcus isolates in La Rioja, Spain

Genome analysis of Streptococcus spp. isolates from animals in pre-antibiotic era with respect to antibiotic susceptibility and virulence gene profiles

Lyophilized Streptococcus spp. isolates (n = 50) from animal samples submitted to the diagnostic laboratory at the University of Connecticut in the 1940s were revivified to investigate the genetic characteristics using whole-genome sequencing (WGS). The Streptococcus spp. isolates were identified as follows; S. agalactiae (n = 14), S. dysgalactiae subsp. dysgalactiae (n = 10), S. dysgalactiae subsp. equisimils (n = 5), S. uberis (n = 8), S. pyogenes (n = 7), S. equi subsp. zooepidemicus (n = 4), S. oralis (n = 1), and S. pseudoporcinus (n = 1). We identified sequence types (ST) of S. agalactiae, S. dysgalactiae, S. uberis, S. pyogenes, and S. equi subsp. zooepidemicus and reported ten novel sequence types of those species. WGS analysis revealed that none of Streptococcus spp. carried antibiotic resistance genes. However, tetracycline resistance was observed in four out of 15 S. dysgalactiae isolates and in one out of four S. equi subsp. zooepidemicus isolate. This data highlights that antimicrobial resistance is pre-existed in nature before the use of antibiotics. The draft genome sequences of isolates from this study and 426 complete genome sequences of Streptococcus spp. downloaded from BV-BRC and NCBI GenBank database were analyzed for virulence gene profiles and phylogenetic relationships. Different Streptococcus species demonstrated distinct virulence gene profiles, with no time-related variations observed. Phylogenetic analysis revealed high genetic diversity of Streptococcus spp. isolates from the 1940s, and no clear spatio-temporal clustering patterns were observed among Streptococcus spp. analyzed in this study. This study provides an invaluable resource for studying the evolutionary aspects of antibiotic resistance acquisition and virulence in Streptococcus spp.

Genomic Traits Associated with Virulence and Antimicrobial Resistance of Invasive Group B Streptococcus Isolates with Reduced Penicillin Susceptibility from Elderly Adults

This study aimed to investigate genomic traits underlying the antimicrobial resistance and virulence of multidrug-resistant (MDR) group B streptococci with reduced penicillin susceptibility (PRGBS) recovered from elderly patients with bloodstream infections, which remain poorly characterized. The pangenome was found to be open, with the predicted pan- and core genome sizes being 3,531 and 1,694 genes, respectively. Accessory and unique genes were enriched for the Clusters of Orthologous Groups (COG) categories L, Replication, recombination, and repair, and K, Transcription. All MDR PRGBS isolates retained a core virulence gene repertoire (bibA, fbsA/-B/-C, cspA, cfb, hylB, scpB, lmb, and the cyl operon), supporting an invasive ability similar to that of the other invasive GBS, penicillin-susceptible GBS (PSGBS), and noninvasive PRGBS isolates. The putative sequence type 1 (ST1)-specific AlpST-1 virulence gene was also retained among the serotype Ia/ST1 PRGBS isolates. In addition to tet(M) and erm(B), mef(A)-msr(D) elements or the high-level gentamicin resistance gene aac(6′)-aph(2″), which are both rare in PSGBS, were detected among those MDR PRGBS isolates. In the core single-nucleotide polymorphism (SNP) phylogenetic tree, all invasive ST1 PRGBS isolates with serotypes Ia and III were placed together in a clade with a recombination rate of 3.97, which was 36 times higher than the value found for a clade formed by serotype V/ST1 PSGBS isolates derived mostly from human blood. ST1 has been the predominant sequence type among the PRGBS isolates in Japan, and serotypes Ia and III have been very rare among the ST1 PSGBS isolates. Thus, these lineages that mostly consisted of serotypes Ia/ST1 and III/ST1 PRGBS could possibly emerge through recombination within the ST1 populations.

IMPORTANCEStreptococcus agalactiae, or group B Streptococcus (GBS), is recognized as the leading cause of neonatal invasive infections. However, an increasing incidence of invasive GBS infections among nonpregnant adults, particularly the elderly and those with underlying diseases, has been observed. There is a trend toward the increasing occurrence of penicillin nonsusceptibility among GBS clinical isolates, from 4.8% in 2008 to 5.8% in 2020 in Japan. Also, in the United States, the frequency of adult invasive GBS isolates suggestive of β-lactam nonsusceptibility increased from 0.7% in 2015 to 1.0% in 2016. In adults, mortality has been significantly higher among patients with bacteremia than among those without bacteremia. Our study revealed that invasive GBS with reduced penicillin susceptibility (PRGBS) isolates harbor major virulence and resistance genes known among GBS, highlighting the need for large population-based genomic surveillance studies to better understand the clinical relevance of invasive PRGBS isolates.

Multiple-locus variable-number tandem repeat analysis for genotyping of erythromycin-resistant group B streptococci in Iran

Background

Group B Streptococcus (GBS or S. agalactiae) is an important pathogen causing severe invasive diseases in neonates, pregnant women, and adults with underlying medical conditions.

Methods

To investigate the incidence of resistance to macrolide, lincosamide and streptogramin type B (MLS_B) antibiotics, macrolide and tetracycline resistance determinants and genetic relationships, a total of 146 clinical isolates of GBS were collected from Tehran, Iran. The genetic relationships between erythromycin-resistant strains were determined by multilocus variable tandem repeat analysis (MLVA).

Results

All isolates were susceptible to penicillin, vancomycin, linezolid, and quinupristin–dalfopristin, but were resistant to tetracycline (96.6%, 141/146), erythromycin (28.1%, 41/146) and clindamycin (16.4%, 24/146). Among the 41 erythromycin-resistant GBS (ERGBS), the most common antimicrobial resistance gene was tetM detected in 92.7% (38/41) of the isolates followed by ermTR and ermB found in 65.8% (27/41) and 29.3% (12/41) of isolates, respectively. Of the 41 ERGBS, 95% (39/41) exhibited the constitutive MLS_B phenotype, 2.4% (1/41) displayed inducible MLS_B and 2.4% (1/41) had M phenotype. The erm methylase genes were widely related to MLS_B phenotype isolates, while the mefA gene was associated with M phenotype. MLVA analysis performed on the 41 ERGBS revealed that 34 MLVA types (MTs). MLVA analysis showed that infections due to ERGBS have been caused by a variety of genotypes, suggesting that ERGBS were clonally unrelated and dissemination of these isolates was not due to a clonal outbreak.

Conclusion

Careful usage of macrolide antibiotics in therapy, continued surveillance of resistance rate and appropriate infection control measures can help to reduce spreading of resistance isolates.

Phenotypic and Genotypic Characterization of Resistance to Macrolides and Lincosamides in Streptococcus agalactiae Isolated from Pregnant Women in Misiones, Argentina

The aim of this work was to determine the susceptibility, molecular profile, and clonal relationship in Streptococcus agalactiae (group B Streptococcus [GBS]) isolated from vaginal-rectal swab samples. We worked with 200 isolates collected from pregnant women between 35 and 37 weeks of gestation. The macrolide-lincosamide-streptogramin B (MLS_B) resistance phenotypes were determined using the double-disc assay. Susceptibility to erythromycin (ERI) and clindamycin (CLI) was performed with the E-test. Resistance genes ermB and ermTR were detected by polymerase chain reaction. Clonal studies were performed using the random amplification of polymorphic DNA. Twelve (6%) of the isolates were resistant to ERI and 10 (5%) of them to CLI. Fifty percent of the resistant strains corresponded to serotype III, 25% to serotype V, and the remaining 25% to serotype Ia, II, and nontypeable strains. The cMLS_B phenotype was detected in eight strains (66.67%) and the iMLS_B phenotype in four (33.33%). The minimum inhibitory concentration values were between 1.5 and 16 μg/mL for ERI, and between 1 and 32 μg/mL for CLI. Out of the 25 strains susceptible to ERI and CLI, the presence of the ermB gene was detected in eight of them and the ermTR gene in one strain. The ermB gene was detected in the 12 strains that initially had some macrolide resistance phenotype. The ermTR gene was detected in three out of the four strains with the iMLS_B phenotype. The resistance to macrolides in the province of Misiones is due to multiclonal spread. The phenotypic and genotypic characterization of macrolide resistance in GBS strains are crucial to contribute to the correct intrapartum prophylactic antibiotic therapy of allergic pregnant women and the epidemiological surveillance of these strains.

Antibiotic Resistance of Non-pneumococcal Streptococci and Its Clinical Impact

The taxonomy of streptococci has undergone major changes during the last two decades. The present classification is based on both phenotypic and genotypic data. Phylogenetic classification of streptococci is based on 16S rRNA sequences [1], and it forms the backbone of the overall classification system of streptococci. Phenotypic properties are also important, especially for clinical microbiologists. The type of hemolysis on blood agar, reaction with Lancefield grouping antisera, resistance to optochin, and bile solubility remain important for grouping of clinical Streptococcus isolates and therefore treatment options [2]. In the following chapter, two phenotypic classification groups, viridans group streptococci (VGS) and beta-hemolytic streptococci, will be discussed.

Failure of clindamycin to eradicate infection with beta-hemolytic streptococci inducibly resistant to clindamycin in an animal model and in human infections

Inducible clindamycin resistance in beta-hemolytic streptococci remains an underrecognized phenomenon of unknown clinical significance. We performed an evaluation of inducible clindamycin resistance using an animal model as well as retrospectively reviewing the charts of patients treated with clindamycin monotherapy who were infected with beta-hemolytic streptococci inducibly resistant to clindamycin. The neutropenic mouse thigh model of infection was used to evaluate the in vivo activity of clindamycin against beta-hemolytic streptococci, including isolates susceptible, inducibly resistant, or constitutively resistant to clindamycin. The clinical microbiology laboratory information system and pharmacy databases were cross-referenced to identify patients with infections due to inducibly clindamycin-resistant beta-hemolytic streptococci who were treated with clindamycin monotherapy. Medical records of these patients were reviewed to evaluate microbiologic and clinical outcomes. Inducible clindamycin resistance resulted in impaired killing of beta-hemolytic streptococci in the animal model. Though suppressed initially, compared to those with constitutive resistance (P=0.0429), by 48 h, colony counts of inducibly clindamycin-resistant organisms were similar to those of constitutively resistant isolates (P=0.1142). In addition, we identified 8 patients infected with inducibly clindamycin-resistant beta-hemolytic streptococci who experienced clinical and microbiologic failure when treated with clindamycin monotherapy. These patients either improved initially and subsequently failed or never responded to clindamycin therapy. We have demonstrated in a murine model of infection and from human cases that inducible clindamycin resistance in beta-hemolytic streptococci is clinically significant. Routine testing and reporting by clinical laboratories should be encouraged and alternative antimicrobial agents considered when these organisms are encountered in clinical care.

Macrolide and tetracycline resistance in clinical strains of Streptococcus agalactiae isolated in Tunisia

Between 2007 and 2009, 226 clinical strains of Streptococcus agalactiae, recovered from female genital specimens and from gastric fluid or ear specimens from infected newborns, were isolated at the Laboratory of Microbiology of Charles Nicolle Hospital of Tunis. They were investigated to determine the prevalence of antibiotic resistance and to characterize the mechanisms of resistance to macrolide and tetracycline. All strains were susceptible to penicillin, ampicillin and quinupristin-dalfopristin. They were resistant to chloramphenicol (3.1%), rifampicin (19.1%), erythromycin (40%) and tetracycline (97.3%); 3.1% were highly resistant to streptomycin and 1.3% to gentamicin. Among the erythromycin-resistant isolates, 78.7% showed a constitutive macrolide-lincosamide-streptogramin B (MLS(B)) phenotype with high-level resistance to macrolides and clindamycin (MIC(50) >256 µg ml(-1)), 10% showed an inducible MLS(B) phenotype with high MICs of macrolides (MIC(50) >256 µg ml(-1)) and low MICs of clindamycin (MIC(50)=8 µg ml(-1)) and 2.2% showed an M phenotype with a low erythromycin-resistance level (MIC range=12-32 µg ml(-1)) and low MICs of clindamycin (MIC range: 0.75-1 µg ml(-1)). All strains were susceptible to quinupristin-dalfopristin and linezolid (MIC(90): 0.75 µg ml(-1) for each). MLS(B) phenotypes were genotypically confirmed by the presence of the erm(B) gene and the M phenotype by the mef(A) gene. Resistance to tetracycline was mainly due to the tet(M) gene (93.1%) encoding a ribosome protection mechanism. This determinant is commonly associated with the conjugative transposon Tn916 (P≤0.0002). tet(O) and tet(T) existed in a minority (2.2% and 0.4%, respectively). The efflux mechanism presented by tet(L) was less frequently present (4.5%). No significant association was found between erm(B) and tet(M) genes.

Macrolides: from in vitro anti-inflammatory and immunomodulatory properties to clinical practice in respiratory diseases

BACKGROUND

Macrolides have long been recognised to exert immunomodulary and anti-inflammatory actions. They are able to suppress the "cytokine storm" of inflammation and to confer an additional clinical benefit through their immunomodulatory properties.

METHODS

A search of electronic journal articles was performed using combinations of the following keywords: macrolides, COPD, asthma, bronchitis, bronchiolitis obliterans, cystic fibrosis, immunomodulation, anti-inflammatory effect, diabetes, side effects and systemic diseases.

RESULTS

Macrolide effects are time- and dose-dependent, and the mechanisms underlying these effects remain incompletely understood. Both in vitro and in vivo studies have provided ample evidence of their immunomodulary and anti-inflammatory actions. Importantly, this class of antibiotics is efficacious with respect to controlling exacerbations of underlying respiratory problems, such as cystic fibrosis, asthma, bronchiectasis, panbrochiolitis and cryptogenic organising pneumonia. Macrolides have also been reported to reduce airway hyper-responsiveness and improve pulmonary function.

CONCLUSION

This review provides an overview on the properties of macrolides (erythromycin, clarithromycin, roxithromycin, azithromycin), their efficacy in various respiratory diseases and their adverse effects.

Detection of inducible clindamycin resistance in beta-hemolytic streptococci by using the CLSI broth microdilution test and erythromycin-clindamycin combinations

This study assessed an erythromycin-clindamycin (ERY-CC) broth test for inducible CC resistance in beta-hemolytic streptococci. One hundred one isolates of groups A, B, C, F, and G were tested by the CLSI broth microdilution method. Combinations of 1 and 0.25 microg/ml or 0.5 and 0.25 microg/ml of ERY and CC, respectively, detected all inducible isolates.

Antibiotic Resistance of Non-Pneumococcal Streptococci and Its Clinical Impact

Viridans streptococci (VGS) form a phylogenetically heterogeneous group of species belonging to the genus Streptococcus (1). However, they have some common phenotypic properties. They are alfa- or non-haemolytic. They can be differentiated from S. pneumoniae by resistance to optochin and the lack of bile solubility (2). They can be differentiated from the Enterococcus species by their inability to grow in a medium containing 6.5% sodium chloride (2). Earlier, so-called nutritionally variant streptococci were included in the VGS but based on the molecular data they have now been removed to a new genus Abiotrophia (3) and are not included in the discussion below. VGS belong to the normal microbiota of the oral cavities and upper respiratory tracts of humans and animals. They can also be isolated from the female genital tract and all regions of the gastrointestinal tract (2, 3). Several species are included in VGS and are listed elsewhere (2, 3). Clinically the most important species belonging to the VGS are S. mitis, S. sanguis and S. oralis.

Antibiotic susceptibility patterns and prevalence of group B Streptococcus isolated from pregnant women in Misiones, Argentina

This study was performed to determine the susceptibility patterns and the colonization rate of Group B Streptococcus (GBS) in a population of pregnant women. From January 2004 to December 2006, vaginal-rectal swabs were obtained from 1105 women attending Dr. Ramón Madariaga Hospital, in Posadas, Misiones, Argentina. The carriage rate of GBS among pregnant women was 7.6%. A total of 62 GBS strains were randomly selected for in vitro susceptibility testing to penicillin G, ampicillin, tetracycline, levofloxacin, gatifloxacin, ciprofloxacin, quinupristin-dalfopristin, linezolid, vancomycin, rifampicin, trimethoprim- sulfametoxazol, nitrofurantoin, gentamicin, clindamycin and erythromycin, and determination of resistance phenotypes. No resistance to penicillin, ampicillin, quinupristin-dalfopristin, linezolid, and vancomycin was found. Of the isolates examined 96.8%, 98.3%, 46.8%, and 29.0% were susceptible to rifampicin, nitrofurantoin, trimethoprim-sulfametoxazol and tetracycline, respectively. Rank order of susceptibility for the quinolones was: gatifloxacin (98.4%) > levofloxacin (93.5%) > ciprofloxacin (64.5%). The rate of resistance to erythromycin (9.7%) was higher than that of other reports from Argentina. High-level resistance to gentamicin was not detected in any of the isolates. Based on our finding of 50% of GBS isolates with MIC to gentamicin equal o lower than 8 μg/ml, a concentration used in one of the selective media recommended for GBS isolation, we suggested, at least in our population, the use of nalidixic acid and colistin in selective media with the aim to improve the sensitivity of screening cultures for GBS carriage in women.

High rates of erythromycin and clindamycin resistance among OBGYN isolates of group B Streptococcus

In vitro susceptibility testing on 200 Streptococcus agalactiae strains isolated during a 4-year period from vaginal/rectal specimens demonstrated a very high resistance rate for both erythromycin (54%) and clindamycin (33%). Methylase genes erm(B) and erm(TR) and efflux genes mef(E) and mef(A) were detected. Pulsed-field gel electrophoresis showed evidence of both clonal spread and multiclonal dissemination of resistant strains. All but 3 of 200 isolates were susceptible to telithromycin.

Erythromycin resistance in the commensal throat flora of patients visiting the general practitioner: a reservoir for resistance genes for potential pathogenic bacteria

The prevalence and mechanism of erythromycin resistance in commensal throat streptococci was determined from October 2000 until December 2002 as part of an ongoing study of the NIVEL in general practice patients (N=678). Resistance prevalence for 1mg/L and 16 mg/L erythromycin was 57% and 20%, respectively. The percentage of total commensal flora resistant within each patient ranged from 1% to 100% (median, 1%). mefA was predominantly found among isolates on the 1mg/L plates, and ermB was found in 64% of the isolates on the 16 mg/L plates. Erythromycin resistance was transferred from a commensal isolate to Streptococcus pneumoniae with a frequency of 1 x 10(-9). Commensal streptococci of general practice patients in The Netherlands form a large reservoir of transferable erythromycin resistance (genes) for potential pathogenic microorganisms.

Distribution of antimicrobial resistance and virulence-related genes among Brazilian group B streptococci recovered from bovine and human sources

In the present report we describe the characteristics of 189 antimicrobial-resistant Streptococcus agalactiae isolates from bovine (38 isolates) and human (151 isolates) sources. All the strains were resistant to tetracycline (TET), and 16 (8.5%) were also resistant to erythromycin, corresponding to 23.7% of the TET-resistant bovine isolates and 4.6% of the TET-resistant human isolates. The tet(O), erm(B), and mreA resistance-related genes, as well as the bca and scpB virulence-related genes, were the most frequent among the bovine isolates, while the tet(M), erm(A), mreA, bca, lmb, and scpB genes were the most prevalent among the isolates from humans. Although a few major clusters were observed, pulsed-field gel electrophoresis results revealed a variety of profiles, reflecting the substantial genetic diversity among strains of this species isolated from either humans or bovines.

Macrolide resistance determinants of invasive and noninvasive group B streptococci in a Turkish hospital

Macrolide resistance in 156 consecutive group B streptococcal isolates was investigated. Thirty-five isolates (22.4%) had inducible (80%) or constitutive (20%) erythromycin resistance. The genes responsible were erm(B), erm(A) subclass erm(TR), and erm(B) plus erm(TR) in 62.9, 2.9, and 8.6% of isolates, respectively. Nine isolates (25.7%) harbored neither mef nor detectable erm genes.

Six-month multicenter study on invasive infections due to group B streptococci in Argentina

There is little information about invasive infections by group B streptococci (GBS) and their antimicrobial susceptibilities in Latin America. We performed a prospective multicenter study to determine the serotype distribution and the antimicrobial susceptibility of GBS in Argentina. We identified 58 cases, but only 44 had sufficient data to be evaluated. Eight early-, four late-, and one fatal late, late-onset neonatal infections due to GBS were found. A total of 31 patients were adults with bacteremia, skin and soft tissue infections, osteomyelitis, arthritis, meningitis, abdominal infections, and renal abscess. Serotype III was prevalent in late-onset neonatal disease, and several serotypes (Ia/c, III, Ia, and II) were involved in early-onset neonatal infections. Serotypes II, Ia/c, III, and IV were commonly found in adults, with serotype II prevalent in younger adults (18 to 69 years old) and serotype Ia/c prevalent in elderly adults (>70 years old). The mortality rate attributable to GBS infections was 10.8%. All GBS were susceptible to penicillin and ceftriaxone. Resistance to clindamycin (1.7%), erythromycin (5.2%), azithromycin (5.2%), minocycline (69%), and tetracycline (72.4%), to high levels of kanamycin and amikacin (1.7%), and to intermediately high levels of gentamicin (1.7%) was observed. The bifunctional enzyme AAC6'-APH2" was detected in the isolate resistant to aminoglycosides, and other genetic determinants were identified in other resistant isolates: tetM and tetO in tetracycline-resistant streptococci and mefA and ermTR for efflux-mediated and inducible macrolide-lincosamide-streptogramin B-resistant streptococci, respectively. For clinical purposes and rapid and easy detection of high-level aminoglycoside-resistant GBS, a screening method that used 1,000- micro g kanamycin disks is proposed.

[Interpretative reading of the antibiogram in gram-positive cocci]

Resistance to methicillin in Staphylococcus is related to expression of the gene mecA, and implies resistance to all beta-lactams. Breakpoints for interpretation of this mechanism differ in S. aureus and in coagulase-negative species. In relation to macrolides-lincosamides-streptograminsB, the most frequent mechanism among resistant strains is expression of methylases (erm genes). Topoisomerase changes caused by point mutations and expression of the efflux pump NorA determine resistance to quinolones, but there are great differences on the activity of different compounds, which makes interpretative reading difficult. Strains of S. aureus with intermediate susceptibility to glycopeptides (GISA strains) have been recently described. In Spain, there is a high percentage of S. pneumoniae strains intermediate or resistant to penicillin, and a low percentage of strains intermediate or resistant to third generation cephalosporins, because of mutations in genes encoding penicillin-binding proteins. The most frequent phenotype of resistance to macrolides in this species is caused by methylase production. Resistance to quinolones is still uncommon, and is related to the mechanisms previously indicated for Staphylococcus, but clinical interpretation of the antibiograma for this organism is even more complex. No strains of S. pyogenes resistant to penicillin have yet been described. In Spain the most common phenotype of resistance to macrolides in S. pyogenes is determined by efflux pumps (mef genes), affecting 14- and 15-membered macrolides. E. faecalis is usually susceptible to ampicillin, in contrast to E. faecium. Enterococci show intrinsic resistance to aminoglycosides, but still remain susceptible to the combination of these antimicrobials and cell-wall active agents. Strains expressing different aminoglycoside-modifying enzymes became resistant to the combination. Glycopeptide-resistant strains of enterococci are uncommon in our country, but several genotypes, of which vanA is the most relevant from a clinical point of view, have been described in other regions.

Antimicrobial susceptibility patterns of beta-hemolytic and viridans group streptococci: report from the SENTRY Antimicrobial Surveillance Program (1997-2000)

Susceptibility patterns of 15 antimicrobial agents were assessed for 3,400 isolates of beta-hemolytic (betahS) and viridans group (VgS) streptococci in the four regions of the SENTRY Antimicrobial Surveillance Program: Asia-Pacific (APAC), Europe (EU), Latin America (LA) and North America (NA). In 1997 through 2000, SENTRY Program monitors tested strains by reference broth microdilution methods and results were interpreted using National Committee for Clinical Laboratory Standards criteria. Among the betahS processed, 81.9% of strains were either Streptococcus pyogenes (n = 650) or S. agalactiae (n = 1,190). The VgS were generally classified as unspeciated alpha-hemolytic streptococci (n = 512; 44%) or S. mitis (n = 254; 22%). Seven quinolones, two beta-lactams, erythromycin (ER), clindamycin (CM), quinupristin/dalfopristin (Q/D), vancomycin (VA), teicoplanin (TP) and linezolid (LZ) were tested. Rank order of susceptibility for betahS isolates was: ceftriaxone (CTX) = Q/D = VA = TP = LZ (100.0%) > gatifloxacin (GATI) = trovafloxacin (TROV, 99.8%) > levofloxacin (LEVO; 99.7%) > penicillin (PEN; 99.3%) > grepafloxacin (GREPA; 97.4%) > CM (94.4%) > ER (85.5%). ER versus betahS had the highest MIC(90) values (2 microg/ml) and the lowest susceptibility rates across all regions (range, 81.4% in NA to 97.3% in LA). Among the VgS, susceptibility rank order was: VA = TP = LZ (100.0%) > Q/D (99.1%) > GATI = LEVO = TROVA (98.0%) > GREPA (96.5%) > CTX (92.8%) > CM (90.3%) > PEN (68.6%) > ER (64.5%). Macrolide resistance in both streptococcal species groups of the M-phenotype was highest in the Americas, with erm-patterns predominating in EU and APAC regions. BMS284756 among the monitored new agents showed a four- to eight-fold greater potency versus these streptococcal isolates when compared to the other six tested quinolones. Like Streptococcus pneumoniae, these other streptococci appear to have acquired numerous resistances and require continued surveillance to direct adequate therapies.

Macrolide and tetracycline resistance and molecular relationships of clinical strains of Streptococcus agalactiae

Mechanisms for tetracycline and macrolide resistance in 54 isolates of erythromycin-resistant Streptococcus agalactiae were analyzed by PCR. The erm(B), erm(A), and mef(A) genes, either alone or in combination, were detected in all the erythromycin-resistant isolates. The tet(M) and tet(O) genes were responsible for tetracycline resistance. Random amplification of polymorphic DNA indicated different clonal origins of the isolates.

Antibiotic susceptibility and mechanisms of erythromycin resistance in clinical isolates of Streptococcus agalactiae: French multicenter study

Among 126 Streptococcus agalactiae isolates collected in 10 French laboratories in 1999, 27 (21.4%) had macrolide resistance related to the presence of erm(B) (11 strains), erm(A) subclass erm(TR) (10 strains), and mef(A) genes (2 strains) and the presence of combinations of erm(B) and erm(A) genes or mef(A) genes (3 strains).