Serotypes and antimicrobial susceptibilities of 1033 pneumococci isolated from children in Greece during 2001–2004

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.

The serotype distribution among healthy carriers before vaccination is essential for predicting the impact of pneumococcal conjugate vaccine on invasive disease

Pneumococcal conjugate vaccines (PCVs) have substantially reduced morbidity and mortality of pneumococcal disease. The impact of the 7-valent PCV on all-serotype invasive pneumococcal disease (IPD) among children was reported to vary between high-income countries. We investigate the ability to predict this heterogeneity from pre-vaccination data. We propose a parsimonious model that predicts the impact of PCVs from the odds of vaccine serotype (VT) among carriers and IPD cases in the pre-PCV period, assuming that VT are eliminated in a mature PCV programme, that full serotype replacement occurs in carriage and that invasiveness of the NVT group is unchanged. We test model performance against the reported impact of PCV7 on childhood IPD in high-income countries from a recent meta-analysis. The odds of pre-PCV7 VT IPD, PCV schedule, PCV coverage and whether a catch up campaign was used for introduction was gathered from the same analysis. We conducted a literature review and meta-analysis to obtain the odds of pre-PCV7 VT carriage in the respective settings. The model predicted the reported impact on childhood IPD of mature PCV programmes; the ratio of predicted and observed incidence risk ratios was close to 1 in all settings. In the high income settings studied differences in schedule, coverage, and catch up campaigns were not associated with the observed heterogeneity in impact of PCV7 on childhood all-serotype IPD. The pre-PCV7 proportion of VT IPD alone also had limited predictive value. The pre-PCV7 proportion of VT carriage and IPD are the main determinants for the impact of PCV7 on childhood IPD and can be combined in a simple model to provide predictions of the vaccine preventable burden of IPD.

Pneumococcal vaccines (PCVs) that protect children against 7, 10 and 13 of the most pathogenic pneumococcal serotypes have substantially reduced childhood morbidity and mortality. A recent analysis that evaluated the impact of the 7 valent PCV in multiple high income settings in North America, Europe and Oceania found that the magnitude of all-serotype invasive pneumococcal disease reduction varied greatly between settings (24%-83%). We explored potential sources for that variation, including differences in disease epidemiology before vaccination, vaccine coverage, vaccine schedules and the use of catch-up campaigns for introduction. We find that differences in reported disease impact among mature PCV programmes are likely to be unrelated to the differences in the vaccine programme but can be predicted from a simple model based on pre-vaccination epidemiology, in particular the proportion of vaccine serotypes detected among patients with invasive pneumococcal disease and the proportion of vaccine serotypes that are found in the nasopharynx of healthy individuals. This model presents a useful tool to estimate the potential impact of PCVs (as a relative rate reduction), highlights the essential role of pre-vaccination carriage in healthy individuals for disease impact of PCVs and can estimate the prevented burden of disease where disease surveillance is unavailable.

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

Background

We sought to characterize the temporal trends in nasopharyngeal carriage of macrolide-resistant pneumococci during a period with increased heptavalent pneumococcal conjugate vaccine (PCV7) coverage in Central Greece.

Methods

Streptococcus pneumoniae isolates were recovered from 2649 nasopharyngeal samples obtained from day-care center attendees in Central Greece during 2005–2009. A phenotypic and genotypic analysis of the isolates was performed, including the identification of macrolide resistance genes mef(A), subclasses mef(A) and mef(E), as well as erm(B).

Results

Of the 1105 typeable S. pneumoniae isolates, 265 (24%) were macrolide-resistant; 22% in 2005, 33.3% in 2006, 23.7% in 2007, and 20.5% in 2009 (P=0.398). Among these macrolide-resistant pneumococci, 28.5% possessed erm(B), 24.3% erm(B)+mef(E), 41.8% mef(E), and 5.3% mef(A). A mef gene as the sole resistance determinant was carried by 31% of macrolide-resistant isolates belonging to PCV7 serotypes and 75.8% of the non-PCV7 serotypes. Across the 4 annual surveillances, pneumococci carrying mef(A) gradually disappeared, whereas serotype 19F isolates carrying both erm(B) and mef(E) persisted without significant yearly fluctuations. Among isolates belonging to non-PCV7 serotypes, macrolide-resistance was observed in those of serotypes 6A, 19A, 10A, 15A, 15B/C, 35F, 35A, and 24F. In 2009, ie 5 years after the introduction of PCV7 in our country, 59% of macrolide-resistant pneumococci belonged to non-PCV7 serotypes.

Conclusions

Across the study period, the annual frequency of macrolide-resistant isolates did not change significantly, but in 2009 a marked shift to non-PCV7 serotypes occurred. Overall, more than half of the macrolide-resistant isolates possessed erm(B) either alone or in combination with mef(E). erm(B) dominated among isolates belonging to PCV7 serotypes, but not among those of non-PCV7 serotypes.

Community-acquired upper respiratory tract infections and the role of third-generation oral cephalosporins

Common community-acquired infections include those of the upper respiratory tract. In the 1990s, the antimicrobial treatment of upper respiratory tract infections focused on penicillin-resistant Streptococcus pneumoniae. However, following the introduction of a pneumococcal conjugate vaccine, a decrease in invasive pneumococcal disease occurred, and in the case of otitis media a shift towards Haemophilus influenzae as the predominant causative pathogen was observed. Future antimicrobial therapy for outpatient upper respiratory tract infections may need to focus on pathogens such as penicillin-susceptible S. pneumoniae, beta-lactamase-producing H. influenzae, beta-lactamase-negative amoxicillin-resistant H. influenzae and Moraxella catarrhalis. In these circumstances, third-generation oral cephalosporins, such as cefixime and cefdinir, could be increasingly used as an optional first-line therapy in community practice for upper respiratory tract infections suspected to be caused by these key pathogens, as an alternative to amoxicillin-clavulanate.

Nationwide surveillance of Streptococcus pneumoniae in Greece: patterns of resistance and serotype epidemiology

This nationwide study assessed the antimicrobial susceptibility and seroprevalence of Streptococcus pneumoniae in paediatric carriage isolates and in clinical isolates from adult pneumococcal disease in Greece during the years 2004-2006. Among 780 isolates recovered from the nasopharynx of children <6 years old attending day-care centres, non-susceptibility rates to penicillin, cefuroxime, ceftriaxone, erythromycin, tetracycline and trimethoprim/sulfamethoxazole were 34.7%, 25.1%, 1.0%, 33.5%, 26.4% and 44.2%, respectively. Among 89 adult clinical isolates, the respective rates were 48.3%, 46.1%, 5.6%, 48.3%, 32.6% and 40.4%. High-level resistance to penicillin, cefuroxime and ceftriaxone was recorded for 14.4%, 23.3% and 0.1% of paediatric carriage isolates, whereas for clinical adult isolates the respective rates were 25.8%, 38.2% and 2.2%. No resistance to levofloxacin and moxifloxacin was recorded, although 3.5% of paediatric carriage isolates and 23.2% of adult clinical isolates had minimum inhibitory concentrations of ciprofloxacin >2mg/L. Serotypes 19F, 14, 23F and 6B were the most prevalent among carriage and clinical isolates. The 7-valent pneumococcal conjugate vaccine was estimated to provide coverage against 71.7% of paediatric carriage isolates and 51.3% of adult clinical isolates. Resistance rates among clinical isolates from adult sources were higher than those recorded among paediatric carriage S. pneumoniae isolates and displayed an increasingly resistant profile compared with previous reports from our country, warranting continuous vigilance.

Aetiology of bacterial meningitis and resistance to antibiotics of causative pathogens in Europe and in the Mediterranean region

Neisseria meningitidis, Streptococcus pneumoniae and Haemophilus influenzae type b are most commonly associated with bacterial meningitis accounting for almost 90% of reported cases of acute bacterial meningitis in infants over 60 days of age and young children. This work reviews the epidemiology of bacterial meningitis in Europe and in the Mediterranean region as well as the antimicrobial susceptibility of the etiological agents.