Mechanisms of macrolide resistance among Streptococcus pneumoniae isolates from Russia

Phenotypic Adaptation to Antiseptics and Effects on Biofilm Formation Capacity and Antibiotic Resistance in Clinical Isolates of Early Colonizers in Dental Plaque

Despite the wide-spread use of antiseptics in dental practice and oral care products, there is little public awareness of potential risks associated with antiseptic resistance and potentially concomitant cross-resistance. Therefore, the aim of this study was to investigate potential phenotypic adaptation in 177 clinical isolates of early colonizers of dental plaque (Streptococcus, Actinomyces, Rothia and Veillonella spp.) upon repeated exposure to subinhibitory concentrations of chlorhexidine digluconate (CHX) or cetylpyridinium chloride (CPC) over 10 passages using a modified microdilution method. Stability of phenotypic adaptation was re-evaluated after culture in antiseptic-free nutrient broth for 24 or 72 h. Strains showing 8-fold minimal inhibitory concentration (MIC)-increase were further examined regarding their biofilm formation capacity, phenotypic antibiotic resistance and presence of antibiotic resistance genes (ARGs). Eight-fold MIC-increases to CHX were detected in four Streptococcus isolates. These strains mostly exhibited significantly increased biofilm formation capacity compared to their respective wild-type strains. Phenotypic antibiotic resistance was detected to tetracycline and erythromycin, consistent with the detected ARGs. In conclusion, this study shows that clinical isolates of early colonizers of dental plaque can phenotypically adapt toward antiseptics such as CHX upon repeated exposure. The underlying mechanisms at genomic and transcriptomic levels need to be investigated in future studies.

Differences in distribution of MLS antibiotics resistance genes in clinical isolates of staphylococci belonging to species: S. epidermidis, S. hominis, S. haemolyticus, S. simulans and S. warneri

Background

Macrolides and lincosamides are two leading types of antibiotics commonly used in therapies. The study examines the differences in resistance to these antibiotics and their molecular bases in S. epidermidis as well as in rarely isolated species of coagulase-negative staphylococci such as S. hominis, S. haemolyticus, S. warneri and S. simulans. The isolates were tested for the presence of the erm(A), erm(B), erm(C), lnu(A), msr(A), msr(B), mph(C), ere(A) and ere(B) genes. Phenotypic resistance to methicillin and mecA presence were also determined.

Results

The MLS_B resistance mechanism was phenotypically found in isolates of species included in the study. The most prevalent MLS_B resistance mechanism was observed in S. hominis, S. haemolyticus and S. epidermidis isolates mainly of the MLS_B resistance constitutive type. Macrolide, lincosamide and streptogramin B resistance genes were rarely detected in isolates individually. The erm(B), ere(A) and ere(B) genes were not found in any of the strains. The erm(A) gene was determined only in four strains of S. epidermidis and S. hominis while lnu(A) was seen in eight strains (mainly in S. hominis). The erm(C) gene was present in most of S. epidermidis strains and predominant in S. hominis and S. simulans isolates. The examined species clearly differed between one another in the repertoire of accumulated genes.

Conclusions

The presence of genes encoding the MLS_B resistance among CoNS strains demonstrates these genes’ widespread prevalence and accumulation in opportunistic pathogens that might become gene reservoir for bacteria with superior pathogenic potential.

Antimicrobial Resistance Among Streptococcus pneumoniae

Antibiotic resistance in Streptococcus pneumoniae (pneumococcus), the main pathogen responsible for community-acquired pneumonia (CAP), meningitis, bacteremia, and otitis media, is a major concern for clinicians. This pathogen is associated with high rates of morbidity and mortality, especially among children under 2 years old, immunocompromised persons, and the elderly population. The major anti-pneumococcus agents are β-lactams and macrolides, with fluoroquinolones ranking third. The emergence of antibiotic-resistant pneumococcus due to overuse of antibiotics is a global concern. While the discovery of novel classes of antibiotics for the pneumococcus is at a standstill, significant progress in reducing the problem of resistance is associated with antibacterial vaccines. Nevertheless, the World Health Organization recently considered drug-resistant S. pneumoniae as ranking among the 12 bacteria, for which there is an urgent need for new treatments. A challenge is to slow the evolution of new strains that are resistant to the vaccines.

Anti Pneumococcal Activity of Azithromycin-Eudragit RS100 Nano-Formulations

Purpose: Bacterial pneumonia is a common lung infection caused by different types of bacteria. Azithromycin (AZI), an azalide antibiotic, is widely used to manage pneumococcal infections. Studies have shown that antibiotics in nanocarriers may lead to increased antibacterial activity and reduced toxicity. The aim of this work was to valuate in vitro antibacterial performance azithromycin-Eudragit RS100 nano-formulations against Streptococcus pneumoniae and Staphylococcus aureus. Methods: AZI-Eudragit RS100 nanoparticles were prepared via electrospinning technique and the in vitro antibacterial performance against S. pneumoniae and S. aureus were assessed using agar dilution method. Results: Nanofibers in the sizes about 100-300 nm in diameter and micro scale in length and nanobeads in the range of 100-500 nm were achieved. The Minimum Inhibitory Concentrations (MIC) showed an enhancement in the antimicrobial effect of AZI-Eudragit RS100 nanofibers (40 µg/ml) compare to untreated AZI solution (>160 µg/ml) against S. pneumonia. The MIC value for AZI-Eudragit RS100 nanofibers against S. aureus was >128 µg/ml, same as that of the untreated AZI solution. Conclusion: The enhanced efficiency of AZI in nanofibers could be related to the more adsorption opportunity of nanofibers to S. pneumonia capsulated cell wall which provides an antibiotic depot on the bacterial surface compared to S. aureus. AZI-Eudragit RS100 nanofibers with enhanced antimicrobial effect against S. pneumonia can be considered as a candidate for in vivo evaluations in antibiotic therapy of Pneumococcal infections.

Antibiotic susceptibility and molecular mechanisms of macrolide resistance in streptococci isolated from adult cystic fibrosis patients

The cystic fibrosis (CF) airways are colonized by polymicrobial communities with high bacterial load and are influenced by frequent antibiotic exposures. This community includes diverse streptococci, some of which have been directly or indirectly associated with pulmonary exacerbations. As many streptococci are naturally competent, horizontal transfer of antibiotic-resistant determinants coupled with frequent and/or chronic antibiotic exposure may contribute to high resistance rates. In this study, we assessed antibiotic resistance in 413 streptococcal isolates from adult CF patients against nine antibiotics relevant in CF treatment. We observed very low rates of cephalosporin resistance [cefepime and ceftriaxone ( < 2%)], and higher rates of resistance to tetracycline (∼34%) and sulfamethoxazole/trimethoprim (∼45%). The highest rate of antibiotic resistance was to the macrolides [azithromycin (56.4%) and erythromycin (51.6%)]. We also investigated the molecular mechanisms of macrolide resistance and found that only half of our macrolide-resistant streptococci isolates contained the mef (efflux pump) or erm (methylation of 23S ribosomal target site) genes. The majority of isolates were, however, found to have point mutations at position 2058 or 2059 of the 23S ribosomal subunit - a molecular mechanism of resistance not commonly reported in the non-pyogenic and non-pneumococcal streptococci, and unique in comparison with previous studies. The high rates of resistance observed here may result in poor outcomes where specific streptococci are contributing to CF airway disease and serve as a reservoir of resistance genes within the CF airway microbiome.

Bacterial etiology of acute otitis media and characterization of pneumococcal serotypes and genotypes among children in Moscow, Russia

BACKGROUND

We aimed to describe bacterial etiology of acute otitis media (AOM) and characterize resistance, serotypes and genotype profiles of AOM-causing pneumococci recovered in Moscow children.

METHODS

Children with AOM and an available middle ear fluid specimen were prospectively enrolled in this study. Streptococcus pneumoniae, Streptococcus pyogenes, Haemophilus influenzae and Moraxella catarrhalis were considered as true otopathogens. All pneumococcal isolates were serotyped using the Quellung reaction; multidrug-resistant (MDR) pneumococci underwent multilocus sequence typing.

RESULTS

In 172 of 541 enrolled AOM patients (32%) at least 1 otopathogen was recovered, with S. pneumoniae having the highest rate of 63% (109/172). When adjusted for antibiotic treatment before sampling, in untreated patients the rate of culture-positive AOM was 35% (124/352), S. pneumoniae had a prevalence of 69% (86/124), S. pyogenes 19% (24/124), H. influenzae 13% (16/124) and M. catarrhalis 9% (11/124). Among 107 examined pneumococci, 45% were penicillin-nonsusceptible, 34 and 30% were resistant to erythromycin and clindamycin, respectively; 30% had an MDR phenotype, but no amoxicillin-resistant isolates were found. Ten of 32 (31%) MDR pneumococci related to clonal complex 320, the remaining isolates belonged to 7 different clonal complex. Six leading serotypes were 19F (27%), 3 (12%), 6B (11%), 14 (11%), 19A (9%) and 23F (8%); overall polysaccharide conjugate vaccine13 coverage was 93%.

CONCLUSIONS

S. pneumoniae, the leading bacterial AOM pathogen in Moscow children, is characterized by a substantial rate of antibiotic nonsusceptibility and clonality. A polysaccharide conjugate vaccine with expanded coverage seems to fit the current AOM pneumococcal serotype distribution in Russia better.

Genetic basis of the association of resistance genes mef(I) (macrolides) and catQ (chloramphenicol) in streptococci

In streptococci mef(I) and catQ, two relatively uncommon macrolide and chloramphenicol resistance genes, respectively, are typically linked in a genetic module designated IQ module. Though variable, the module consistently encompasses, and is sometimes reduced to, a conserved ∼5.8-kb mef(I)-catQ fragment. The prototype IQ module was described in Streptococcus pneumoniae. IQ-like modules have subsequently been detected in Streptococcus pyogenes and in different species of viridans group streptococci, where mef(E) may be found instead of mef(I). Three genetic elements, one carrying the prototype IQ module from S. pneumoniae and two carrying different, defective IQ modules from S. pyogenes, have recently been characterized. All are integrative and conjugative elements (ICEs) belonging to the Tn5253 family, and have been designated ICESpn529IQ, ICESpy029IQ and ICESpy005IQ, respectively. ICESpy029IQ and ICESpy005IQ were the first Tn5253 family ICEs to be described in S. pyogenes. A wealth of new information has been obtained by comparing their genetic organization, chromosomal integration, and transferability. The origin of the IQ module is unknown. The mechanism by which it spreads in streptococci is discussed.

Phenotypes and genotypes of macrolide-resistant streptococcus pneumoniae

BACKGROUND

Macrolide resistance in Streptococcus pneumoniae (S. pneumoniae) is a worldwide problem.

AIMS

The aim of this work was to analyze the phenotypes, genotypes, and clonal relatedness among macrolide-resistant S. pneumoniae strains isolated from various clinical specimens in our hospital.

STUDY DESIGN

Cross-sectional study.

METHODS

80 non-duplicate S. pneumoniae strains were analyzed by polymerase chain reaction for both the erm (B) and mef (A) genes.

RESULTS

Macrolide resistance was observed in 22.5% (18 strains) of strains. Two (11.2%) isolates possessed mef (A), eight possessed erm (B) (44.4%) and eight strains (44.4%) were positive for both erm (B) and mef (A) genes. Although BOX-PCR of 18 macrolide-resistant strains revealed 11 band patterns, they clustered as seven clones with a genetic distance >10% to each other. Eight isolates possessed both erm (B) and mef (A) genes and belonged to a single clone (44.44% of all macrolide-resistant strains).

CONCLUSION

Increased positivity rates for both resistance genes have also been reported from other hospitals in Turkey, but this is the first study from Turkey showing the clonal dissemination of both resistance genes.

Tn5253 family integrative and conjugative elements carrying mef(I) and catQ determinants in Streptococcus pneumoniae and Streptococcus pyogenes

The linkage between the macrolide efflux gene mef(I) and the chloramphenicol inactivation gene catQ was first described in Streptococcus pneumoniae (strain Spn529), where the two genes are located in a module designated IQ element. Subsequently, two different defective IQ elements were detected in Streptococcus pyogenes (strains Spy029 and Spy005). The genetic elements carrying the three IQ elements were characterized, and all were found to be Tn5253 family integrative and conjugative elements (ICEs). The ICE from S. pneumoniae (ICESpn529IQ) was sequenced, whereas the ICEs from S. pyogenes (ICESpy029IQ and ICESpy005IQ, the first Tn5253-like ICEs reported in this species) were characterized by PCR mapping, partial sequencing, and restriction analysis. ICESpn529IQ and ICESpy029IQ were found to share the intSp 23FST81 integrase gene and an identical Tn916 fragment, whereas ICESpy005IQ has int5252 and lacks Tn916. All three ICEs were found to lack the linearized pC194 plasmid that is usually associated with Tn5253-like ICEs, and all displayed a single copy of a toxin-antitoxin operon that is typically contained in the direct repeats flanking the excisable pC194 region when this region is present. Two different insertion sites of the IQ elements were detected, one in ICESpn529IQ and ICESpy029IQ, and another in ICESpy005IQ. The chromosomal integration of the three ICEs was site specific, depending on the integrase (intSp 23FST81 or int5252). Only ICESpy005IQ was excised in circular form and transferred by conjugation. By transformation, mef(I) and catQ were cotransferred at a high frequency from S. pyogenes Spy005 and at very low frequencies from S. pneumoniae Spn529 and S. pyogenes Spy029.

Serotypes and antibiotic resistance of non-invasive Streptococcus pneumoniae circulating in pediatric hospitals in Moscow, Russia

BACKGROUND

Pneumococcal infections remain a major medical problem associated with high morbidity and mortality. Moreover, the resistance of Streptococcus pneumoniae to conventional antibiotics is constantly growing. The implementation of pneumococcal conjugate vaccines (PCVs) in the last decade has dramatically reduced the incidence of the vaccine type-associated invasive pneumococcal diseases in many countries. However, information on the seroepidemiology of S. pneumoniae in Russia is limited.

METHODS

We report the results of serotyping and antibiotic susceptibility testing performed on 863 non-invasive pneumococcal isolates collected prospectively in 2009-2013 from children (median age 3.5 years) who sought medical care at five pediatric hospitals in Moscow. The isolates were recovered from the nasopharynx (71.2%), middle ear fluid (14.3%), and lower respiratory tract specimens (13.6%).

RESULTS

In total, we identified 45 different serotypes. The six leading serotypes (prevalence >5%) included 19F (21.7%), 6B (12.8%), 23F (10.1%), 14 (9.0%), 6A (8.4%), and 3 (7.5%). Serotype 19A isolates had a prevalence of 2.3%. The proportion of PCV-13 serotypes was 78%; the coverage by PCV-7 was 58.2% and was similar to that of PCV-10 (59.8%). The rate of multidrug-resistant pneumococci (i.e., resistant to ≥3 antimicrobials) was 22%. The majority of the multidrug-resistant isolates were serotype 6B, 14, 19A, and 19F. Penicillin non-susceptibility was displayed by 28% of the isolates. The resistance rate to erythromycin was 26%. Among the examined erythromycin-resistant strains, 54% had the erm(B) gene and 13% had the mef gene as a single resistance determinant, whereas both determinants were found in 31% of these strains.

CONCLUSIONS

Our data predict a good coverage of the circulating S. pneumoniae by the PCVs and could be useful for evaluating the serotype distribution in support of the introduction of PCV in Russia. In addition, the antimicrobial resistance rate of S. pneumoniae in Russia is substantial, and the emergence of pneumococcal strains with a dual macrolide resistance mechanism is alarming.

Dominance of multidrug resistant CC271 clones in macrolide-resistant streptococcus pneumoniae in Arizona

BACKGROUND

Rates of resistance to macrolide antibiotics in Streptococcus pneumoniae are rising around the world due to the spread of mobile genetic elements harboring mef(E) and erm(B) genes and post-vaccine clonal expansion of strains that carry them.

RESULTS

Characterization of 592 clinical isolates collected in Arizona over a 10 year period shows 23.6% are macrolide resistant. The largest portion of the macrolide-resistant population, 52%, is dual mef(E)/erm(B)-positive. All dual-positive isolates are multidrug-resistant clonal lineages of Taiwan19F-14, mostly multilocus sequence type 320, carrying the recently described transposon Tn2010. The remainder of the macrolide resistant S. pneumoniae collection includes 31% mef(E)-positive, and 9% erm(B)-positive strains.

CONCLUSIONS

The dual-positive, multidrug-resistant S. pneumoniae clones have likely expanded by switching to non-vaccine serotypes after the heptavalent pneumococcal conjugate vaccine release, and their success limits therapy options. This upsurge could have a considerable clinical impact in Arizona.

Molecular investigation of macrolide and Tetracycline resistances in oral bacteria isolated from Tunisian children

OBJECTIVE

This study aims to investigate the antibiotic susceptibility of strains isolated from the oral cavity of Tunisian children.

DESIGN

Strains were isolated from the oral cavity of Tunisian children (60 caries-actives and 30 caries-free). Molecular characterization was assessed by PCR assay to detect erythromycin methylase gene (ermB), macrolide efflux (mefI) and tetracycline resistance genes (tetM and tetO).

RESULTS

A total of 21 species were isolated and identified. Antimicrobial susceptibility revealed that the resistance rate to antibiotics was as follow: erythromycin (22%), tetracycline (15.6%), cefotaxim, (7.3%), trimethoprim-sulfamethoxazol (37.6%), nitrofurantoine (2.8%), pristinamycin (17.4%), quinupristin-dalfopristin (15.6%), and rifampicin (3.7%). The majority of mefI positive strains (31.2%) were isolated from the carious children (n=34) in comparison with 8.25% from the control group (n=9). In addition, frequency of strains caring resistance genes were as follow: 12.84% for ermB, 9.17% for tetM and 27.52% for tetO from the carious children in comparison to 0.092%, 3.67% and 3.67% from the caries free group respectively.

CONCLUSION

Multi-resistance strains towards macrolides and tetracycline were recorded. The majority of strains carrying antibiotics resistance genes were isolated from the caries active children. The presence of multi-resistant bacteria in the oral cavity can be the major cause of antibiotic prophylaxis failure in dental practise.