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.

Interaction of the heptavalent pneumococcal conjugate vaccine and the use of individual antibiotics among children on nasopharyngeal colonization with erythromycin-resistant Streptococcus pneumoniae.

The purpose of this study was to assess the complex interaction of the heptavalent pneumococcal conjugate vaccine (PCV7) and individual classes of antimicrobial agents on the nasopharyngeal carriage of erythromycin-resistant pneumococci within the day-care center population. Between February 2005 and May 2007, nasopharyngeal cultures for Streptococcus pneumoniae were obtained from 1,829 day-care center attendees in Central Greece. Thirty-one percent of the pneumococci were erythromycin-resistant; 85.2% of these isolates were also penicillin-nonsusceptible. PCV7 immunization was associated with decreased carriage of erythromycin-resistant PCV7 serotypes but not with an overall decrease in erythromycin-resistant S. pneumoniae colonization. The largest decline in the carriage of erythromycin-resistant pneumococci, particularly of PCV7 serotypes, was observed among vaccinated attendees who had not been exposed to antimicrobials within the preceding 3 months. Exposure to macrolides, 90% clarithromycin, significantly correlated with erythromycin resistance (adjusted odds ratio [AOR] = 2.08, 95% confidence interval [CI] = 1.38-3.12). There was a trend toward an association between the use of oral cephalosporins, other than cefprozil and cefaclor, and colonization with erythromycin-resistant pneumococci (AOR = 1.91, 95% CI = 0.92-3.96). Penicillins had a nonsignificant correlation with the carriage of erythromycin-resistant pneumococci (AOR = 1.17, 95% CI = 0.80-1.71). Despite the widespread PCV7 immunization, the antibiotic pressure, particularly of macrolides, continues to cause dissemination of erythromycin-resistant, commonly multidrug-resistant, pneumococci within the day-care center population.

Pneumonia with empyema among children in the first five years of high coverage with 13-valent pneumococcal conjugate vaccine.

BACKGROUND: Parapneumonic effusions in children are usually associated with pneumococcal infections. In Greece, the 7-valent pneumococcal conjugate vaccine was replaced by higher-valent pneumococcal conjugate vaccines (PCVs); 10-valent was introduced in May 2009 and 13-valent (PCV13) in June 2010. Since July 2010, PCV13 has been the most commonly used PCV. In a study conducted at the University General Hospital of Larissa, Central Greece, from January 2012 to January 2016, 85.7% of children born after the implementation of PCV13 and aged 24-59 months had received the complete series (3 + 1 immunization schedule) of PCV13. METHODS: We studied all paediatric community-acquired pneumonia cases with empyema hospitalized at the University General Hospital of Larissa from January 2008 to January 2016. RESULTS: There were 30 cases of parapneumonic empyema. Among 27 empyema cases of known aetiology, 19 (70.4%) were due to Streptococcus pneumoniae (identifiable serotypes 3, 19A, 7F, and 9N/L). After September 2011, no more cases caused by serotypes 7F and 19A were observed, whereas serotype 3 emerged as the predominant pathogen of pneumococcal empyema (9 of 11 cases). Serotype 3 continued to cause empyema despite vaccination with PCV13 either fully with a 3 + 1 schedule (n = 3) or with one booster dose at the age of 21 months (n = 1). CONCLUSION: In Central Greece during the first five years of high coverage with PCV13, serotype 3 was the only PCV13 serotype that clearly persisted in children with empyema.