Macrolide resistance determinants among Streptococcus pneumoniae isolates from carriers in Central Greece

Increase of Macrolide-Resistance in Streptococcus pneumoniae Strains After the Introduction of the 13-Valent Pneumococcal Conjugate Vaccine in Lima, Peru

Streptococcus pneumoniae upper respiratory infections and pneumonia are often treated with macrolides, but recently macrolide resistance is becoming an increasingly important problem. The 13-valent pneumococcal conjugate vaccine (PCV13) was introduced in the National Immunization Program of Peru in 2015. This study aimed to evaluate the temporal evolution of macrolide resistance in S. pneumoniae isolates collected in five cross-sectional studies conducted before and after this vaccine introduction, from 2006 to 2019 in Lima, Peru. A total of 521 and 242 S. pneumoniae isolates recovered from nasopharyngeal swabs from healthy carrier children < 2 years old (2 carriage studies) and samples from normally sterile body areas from pediatric patients with invasive pneumococcal disease (IPD) (3 IPD studies), respectively, were included in this study. Phenotypic macrolide resistance was detected using the Kirby-Bauer method and/or MIC test. We found a significant increase in macrolide resistance over time, from 33.5% to 50.0% in carriage studies, and from 24.8% to 37.5% and 70.8% in IPD studies. Macrolide resistance genes [erm(B) and mef(A/E)] were screened using PCR. In carriage studies, we detected a significant decrease in the frequency of mef(A/E) genes among macrolide-resistant S. pneumoniae strains (from 66.7% to 50.0%) after introduction of PCV13. The most common mechanism of macrolide-resistant among IPD strains was the presence of erm(B) (96.0%, 95.2% and 85.1% in the 3 IPD studies respectively). Macrolide resistance was more common in serotype 19A strains (80% and 90% among carriage and IPD strains, respectively) vs. non-serotype 19A (35.5% and 34.4% among carriage and IPD strains, respectively). In conclusion, S. pneumoniae macrolide resistance rates are very high among Peruvian children. Future studies are needed in order to evaluate macrolide resistance trends among pneumococcal strains, especially now after the COVID-19 pandemic, since azithromycin was vastly used as empiric treatment of COVID-19 in Peru.

Characterization of macrolide resistance in bacteria isolated from macrolide-polluted and unpolluted river sediments and clinical sources in Croatia

Environments polluted with excessively high levels of antibiotics released from manufacturing sites can act as a source of transferable antibiotic resistance (AR) genes to human commensal and pathogenic bacteria. The aim of this study was to evaluate AR of bacteria isolated from the Sava river sediments (Croatia) at the discharge site of effluents from azithromycin production compared to those from the upstream site and isolates collected in Croatian hospitals. A total of 228 environmental strains of azithromycin-resistant bacteria were isolated and identified, with 124 from the discharge site and 104 from the upstream site. In addition, a total of 90 clinical, azithromycin-resistant streptococcal and staphylococcal isolates obtained from the Croatian Reference Center for Antibiotic Resistance Surveillance were analyzed. PCR screening of isolates on 11 relevant macrolide-resistance genes (MRGs) showed that discharge isolates had greater detection frequencies for 4 gene targets (ermB, msrE, mphE and ermF) compared to upstream isolates. Among clinical isolates, the most frequently detected gene was ermB, followed by msrD, mefE and mefC. The discharge site demonstrated a greater abundance of isolates with co-occurrence of two different MRGs (predominantly msrE-mphE) than the upstream site, but a lower abundance than the clinical sources (most commonly msrD-mefE). The simultaneous presence of three or even four MRGs was specific for the discharge and clinical isolates, but not for the upstream isolates. When MRG results were sorted by gene mechanism, the ribosomal methylation (erm) and protection genes (msr) were the most frequently detected among both the discharge and the clinical isolates. Following sequencing, high nucleotide sequence similarity was observed between ermB in the discharge isolates and the clinical streptococcal isolates, suggesting a possible transfer of the ermB gene between bacteria of clinical and environmental origin. Our study highlights the importance of environmental bacterial populations as reservoirs for clinically relevant macrolide-resistance genes.

Results from the Survey of Antibiotic Resistance (SOAR) 2014-16 in Greece

Objectives

To determine antimicrobial susceptibility in isolates of Streptococcus pneumoniae and Haemophilus influenzae collected in 2014-16 from patients with community-acquired respiratory tract infections in Greece.

Methods

MICs were determined by CLSI broth microdilution and susceptibility assessed using CLSI, EUCAST and pharmacokinetic/pharmacodynamic (PK/PD) breakpoints.

Results

A total of 99 S. pneumoniae and 52 H. influenzae isolates were collected. Overall, 36.4% of S. pneumoniae were penicillin susceptible by CLSI oral/EUCAST and 88.9% by CLSI intravenous (iv) breakpoints. All were fluoroquinolone susceptible with ≥94% of isolates also susceptible to amoxicillin, amoxicillin/clavulanic acid and ceftriaxone by CLSI and PK/PD breakpoints. Trimethoprim/sulfamethoxazole, cefuroxime, cefaclor and macrolides were less active, with rates of susceptibility of 83.8%, 69.7%, 50.5% and 49.5%, respectively, by CLSI. Generally susceptibility was the same or slightly lower by EUCAST, but the cefaclor difference was much greater. Among H. influenzae, 15.4% of isolates were β-lactamase positive. Susceptibility to amoxicillin/clavulanic acid, ceftriaxone, cefuroxime and the fluoroquinolones was seen in >95% of isolates by CLSI criteria. Susceptibility to azithromycin was seen in 94.2% of isolates using CLSI breakpoints, but clarithromycin susceptibility was lower (61.5%). However, susceptibility to both macrolides was seen in <5% of isolates by PK/PD and EUCAST criteria. Susceptibility to trimethoprim/sulfamethoxazole was seen in 71.2% of isolates.

Conclusions

Owing to the high prevalence of macrolide resistance among S. pneumoniae and the reduced activity of clarithromycin against H. influenzae, it appears that these agents are not appropriate as monotherapy for community-acquired pneumonia in Greece. Amoxicillin/clavulanic acid, on the other hand, maintained excellent in vitro activity and, as opposed to the similarly effective fluoroquinolones, is safe to use in paediatric patients.

High Frequency of Macrolide-Resistant Streptococcus pneumoniae Colonization in Respiratory Tract of Healthy Children in Ardabil, Iran

BACKGROUND

Streptococcus pneumoniae (S. pneumoniae) is one of the most common causes of human diseases in young children. Macrolides are commonly antibiotics used for empirical treatment of community-acquired respiratory infections. The purpose of this study was to determine antibiotic resistance pattern as well as the relationship between macrolide resistance and the major mechanisms of resistance in pneumococci isolated from healthy children.

MATERIALS AND METHODS

In this cross-sectional study, 43 isolates of S. pneumoniae were collected from healthy children in Ardabil. Resistance pattern against tested antibiotics was determined using the disk diffusion method. The Minimum Inhibitory Concentration (MIC) of erythromycin was determined using the E-test strips. The mefA/E and ermB gene were detected in erythromycin-resistant isolates using the specific primers and Polymerase Chain Reaction (PCR) technique.

RESULTS

According to antimicrobial susceptibility testing, 74.4 % of the isolates were resistant to erythromycin, 95.3 % to penicillin, 81.3 % to co-trimoxazole, 72 % to azithromycin, 41.8 % to tetracycline, 27.9 % to clindamycin, and 16.2 % to chloramphenicol. All isolates were susceptible to levofloxacin and vancomycin. In the case of rifampin, 95.3% of the isolates were sensitive and 4.6% semi-sensitive. The MIC of erythromycin for resistant isolates was between 1.5 and ≥ 256 μg/ml. PCR results revealed that 100% of erythromycin-resistant isolates contained mefA/E gene and 81.25 % contained both the ermB and mefA/E genes.

CONCLUSION

The prevalence of antibiotic-resistant strains of S. pneumoniae, especially resistance to macrolides, was high among healthy children in Ardabil. According to the results of this study, we suggest using levofloxacin, rifampin and vancomycin antibiotics as an appropriate prophylactic regimen in pneumococcal infections.

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.

Macrolide Resistance in Streptococcus pneumoniae

Streptococcus pneumoniae is a common commensal and an opportunistic pathogen. Suspected pneumococcal upper respiratory infections and pneumonia are often treated with macrolide antibiotics. Macrolides are bacteriostatic antibiotics and inhibit protein synthesis by binding to the 50S ribosomal subunit. The widespread use of macrolides is associated with increased macrolide resistance in S. pneumoniae, and the treatment of pneumococcal infections with macrolides may be associated with clinical failures. In S. pneumoniae, macrolide resistance is due to ribosomal dimethylation by an enzyme encoded by erm(B), efflux by a two-component efflux pump encoded by mef (E)/mel(msr(D)) and, less commonly, mutations of the ribosomal target site of macrolides. A wide array of genetic elements have emerged that facilitate macrolide resistance in S. pneumoniae; for example erm(B) is found on Tn917, while the mef (E)/mel operon is carried on the 5.4- or 5.5-kb Mega element. The macrolide resistance determinants, erm(B) and mef (E)/mel, are also found on large composite Tn916-like elements most notably Tn6002, Tn2009, and Tn2010. Introductions of 7-valent and 13-valent pneumococcal conjugate vaccines (PCV-7 and PCV-13) have decreased the incidence of macrolide-resistant invasive pneumococcal disease, but serotype replacement and emergence of macrolide resistance remain an important concern.

Phenotypic and genotypic characterization of Streptococcus pneumoniae resistant to macrolide in Casablanca, Morocco

In Morocco, the 13-valent pneumococcal conjugate vaccine (PCV-13) was introduced in the national immunization program (NIP) in October 2010 and replaced by the PCV-10 in July 2012. The present study aimed to determine the prevalence of erythromycin-resistant Streptococcus pneumoniae (ERSP) and to analyze the phenotypic and genotypic characteristics of these isolates in Casablanca, Morocco from January 2007 to December 2014. Isolates were obtained from the Microbiology Laboratory of Ibn Rochd University Hospital Centre of Casablanca. Serogrouping was done using Pneumotest Kit and serotyping by the Quellung capsular swelling. Antibiotic susceptibility pattern was determined by disk diffusion and Etest methods. A total of 655S. pneumoniae isolates were collected from 2007 to 2014 from pediatric and adult patients. Fifty-five percent of these isolates were from invasive pneumococcal diseases. Of the 655 isolates, 92 (14%) were ERSP. Globally, the proportion of ERSP from 2007 to 2010 (before vaccination) and from 2011 to 2014 (after vaccination) were 11.6% and 17.2% (p=0.04), respectively. Of the 92 ERSP, 89%, 4% and 7% displayed constitutive MLSB (resistance to macrolide, lincosamide and streptogramin B), inducible MLSB, and M phenotype (resistance to macrolide only), respectively. ERSP genotypic analysis showed that 90.2% carried the ermB gene, 6.5% the mefE gene, and 3.3% both the genes (ermB+mefE). The most prevalent ERSP serotypes were 6B, 19F and 23F before vaccination and 19F, 6B, 6A and 23F after vaccination. Erythromycin resistance among S. pneumoniae is relatively high in Casablanca. The contribution of PCVs to the reduction in antibiotic use is encouraging but this should be accompanied by a rational use of antibiotic.

Pneumococcal Mastoiditis in Children Before and After the Introduction of Conjugate Pneumococcal Vaccines

OBJECTIVES

To determine whether serotype distribution and antibiotic resistance of Streptococcus pneumoniae acute mastoiditis (AM) in children have changed in the post pneumococcal conjugate vaccines (PCVs) era.

METHODS

Medical records of pneumococcal AM cases, in a tertiary pediatric hospital were reviewed from January 1999 to December 2014. S. pneumoniae isolates were serotyped using the quellung reaction and tested for antibiotic susceptibility by E-test and for macrolide resistance genes by polymerase chain reaction.

RESULTS

Among 334 children with AM, S. pneumoniae was isolated from 89 (26.6%) with median age 22 months (interquartile range: 12-30 months). S. pneumoniae was recovered from ear fluid (58%), mastoid specimens (35.2%) and blood (6.8%). Resistance to penicillin, erythromycin and clindamycin was 12.4%, 49.4% and 18%, respectively. Distribution of pneumococcal serotypes before (1999-2005), after the introduction of PCV7 (2006-2010) and after PCV13 (2011-2014) was found: for the PCV7 serotypes 81%, 25% and 0% (P < 0.0001), for PCV13 additional serotypes 16.3%, 70.8% and 63.6% (P < 0.0001) and for non-PCV serotypes 2.3%, 4.1% and 36.3% (P = 0.0002), respectively. Significant increase was detected for the serotype 19A after PCV7, and this trend was not changed after PCV13 (2.3%, 50% and 50%, respectively; P < 0.0001). A significant proportion of resistant isolates to penicillin (54.5%) and erythromycin (34.8%) was identified as 19A.

CONCLUSIONS

After the introduction of PCV7, a significant increase of serotype 19A and replacement of PCVs serotypes was identified. After PCV13, the overall proportion of pneumococcal mastoiditis and the incidence of serotype 19A were not significantly declined. A significant proportion of resistant isolates to penicillin and erythromycin is attributed to serotype 19A.

Representation of Streptococcus Pneumoniae in Outpatient Population of Sarajevo Canton

Introduction:

Streptococcus pneumoniae in asymptomatic manner colonize the mucous membranes of the nasopharynx of children and adults, but can cause serious illness in the media which are naturally sterile. In 5-40% of healthy population this bacteria colonize the nasopharyngeal mucosa thanks to the surface adhesin protein, which allow the bacteria to attach to the epithelial cells. The normal nasopharyngeal microflora retains pneumococcus in a small number and does not allow it to express its pathogenic potential and cause disease. If this dominance of the normal microflora is violated, after adherence and local duplication, pneumococcus can spread to the middle ear, sinuses or lungs. Colonization is more common in children than in adults.

Goal:

The goal of this study was to determine the prevalence of the carrier state and susceptibility of pneumococcal strains that circulate in the outpatient population of Sarajevo Canton as a potential source of infection.

Material and methods:

In the microbiological laboratory of the Institute of Public Health of Canton Sarajevo in the period from July 1, 2013 until April 15, 2014 were analyzed swabs of the nose and nasopharynx, eye and ear from a total of 4109 outpatients. Swabs were inoculated on blood agar nutrient medium. Then was performed catalase test, preparation by Gram and susceptibility test on Optochin. Isolates positive for S. pneumoniae were subjected to in vitro assays to investigate the antimicrobial susceptibility/resistance.

Results:

Out of 4109 analyzed swabs the pneumococcus positive was 180 (4.38%). Of these, 137 (76.11%) nasal and nasopharyngeal swabs, 33 (18.33%) of the eyes and 10 (5.56%) ear. The highest number of positive swabs were isolated in children aged 6 years and less, a total of 168 (93.33%), in children aged 7-13 years were positive 7 (3.89%), while among respondents aged 14-20 years only 5 (2.78%).

Conclusions:

The most common site for isolation of pneumococci is the nose and throat, and the most common carriers of these bacteria are children under 6 years of age. Determining the prevalence of the carrier state contributes to the improvement of preventive measures to reduce the risk of infection and possible sequels.

Nasopharyngeal carriage of Streptococcus pneumoniae in Romanian children before the introduction of the pneumococcal conjugated vaccination into the national immunization programme: a national, multi-centre, cross-sectional observational study

OBJECTIVES

We analysed the distribution of vaccine and non-vaccine Streptococcus pneumoniae serotypes and the antimicrobial susceptibility of pneumococcal strains isolated from healthy Romanian children.

METHODS

A multi-centre cross-sectional study was performed in four counties to evaluate carried strains of S. pneumoniae isolated from 2000 children aged 0-5 years.

RESULTS

S. pneumoniae carriage was detected in 25.25% of the tested children. Carriage increased from 16.7% among infants to 29.4% in 3-5-year-old children (p<0.0001). The proportions of the serotypes included in pneumococcal conjugate vaccines PCV7, PCV10, and PCV13 among our isolates were 39.9%, 40.1%, and 58.7%, respectively. Erythromycin resistance was 72.5%, and it was significantly lower in non-vaccine serotypes compared with PCV13 serotypes: 57.3% versus 83.6% (p<10(-7)). Penicillin minimum inhibitory concentrations (MICs) >0.064mg/l were recorded in 71.6%, but the penicillin MIC was >2mg/l for only 8.4% of tested isolates.

CONCLUSIONS

In Romanian children, the majority of carried S. pneumoniae isolates are vaccine serotypes. The isolates with MICs defining macrolide resistance were very frequent, as well as the isolates with MICs defining penicillin resistance in the case of meningitis or penicillin dose-dependent susceptibility for other infections, mainly for the strains belonging to PCV13 serotypes. The implementation of PCV13 within the Romanian national immunization programme could reduce the circulation of these strains with higher macrolide and/or penicillin MICs.

Evolving role of 13-valent pneumococcal conjugate vaccine in clinical practice

Since the introduction of 7-valent pneumococcal conjugate vaccine (PCV7), PCVs with extended coverage have become available, and there is emerging global evidence that these vaccines, in particular PCV13, have further reduced rates of invasive pneumococcal disease compared with PCV7. The present article aims to address emerging topics related to PCV13 use in routine clinical practice; specifically: (1) the potential role of high-valent PCVs in reducing pneumococcal disease burden; (2) the impact of PCVs on nasopharyngeal carriage and how this may contribute to reductions in otitis media and pneumonia, as well as the prevalence of resistant pneumococcal strains; (3) new PCV13 indications and (4) importance of schedule adherence for PCV in the prevention of cases of vaccine serotype-specific invasive pneumococcal disease. The beneficial effects of PCVs in protecting individuals from a wide spectrum of pneumococcal diseases can be increased by improving the vaccine coverage and adhering to the recommended vaccination schedules. There is increasing evidence that PCV13 has reduced much of the post-PCV7 burden of pneumococcal diseases in the pediatric community, including reducing pneumococcal colonization and the incidence of invasive pneumococcal disease and mucosal diseases. This has also led to a reduction in antibiotic-resistant pneumococcal diseases. The role of PCV13 in clinical practice is evolving, with PCV13 now available for children and adolescents between the ages of 6 weeks and 17 years, thus ensuring that children in all age groups can be protected against vaccine-serotype pneumococcal diseases. Continued surveillance is warranted to monitor the impact of PCV13 on disease burden.

Non-invasive pneumococcal serotypes and antimicrobial susceptibilities in a paediatric hospital in the era of conjugate vaccines

To evaluate the effects of 7-valent pneumococcal conjugate vaccine (PCV7) introduction to the routine childhood immunisation schedule in 2008 and its replacement by PCV13 in 2010 in Ireland, we surveyed the serotypes and antimicrobial susceptibilities of 339 pneumococci associated with carriage and non-invasive infection (NII) in a Dublin paediatric hospital from 2009 to 2012. Furthermore, we compared the distribution of pneumococcal serotypes collected from 2009 to 2012 to 105 NII pneumococci isolated in 2007, the year before conjugate vaccine introduction. PCV7 serotypes declined from 2007 to 2012 as follows: carriage, 67-23% (p=0.0004); conjunctivitis, 58-0% (p<0.0001); non-bacteraemic lower respiratory tract infection, 50-19% (p=0.0363) and otitis media 54-27%. Notably, antimicrobial resistant (AMR) PCV7 serotypes showed a significant decrease by the end of the study period (i.e. 2012) (p<0.0001). Compared with 2007 the overall occurrence of serotype 19A increased from 1.9 to 10% in 2010 (p=0.0132) and to 15% in 2011 (p=0.0005). Importantly, serotype 19A declined significantly from 2011 levels to an overall prevalence of 4.8% in 2012 (p=0.0243). Most striking was the significant reduction of AMR 19A (p=0.0195). Conversely, increases were observed in non-vaccine type (NVT) pneumococci in 2009-2012, of which serotypes 11A (n=30), 15B/C (n=17), 22F (n=14), 35Bn=13), non-typeable pneumococci (n=13) and 23A (n=12) were the most prevalent. Moreover, an increase in NVT non-susceptible to at least one antimicrobial in 2009-2012 was noted, attributable to serotypes 35B (n=10) and 15A (n=7). In summary, this study has shown that PCV7 and PCV13 introduction has had a positive impact on their target serotypes and antimicrobial resistance amongst pneumococci within a paediatric hospital within a short time period. However, the increase in NVT prevalence highlights the need for continued surveillance.