Serotypes and antimicrobial resistance of S. pneumoniae nasopharyngeal carriage in children from Cyprus: A country with relatively low coverage with the seven-valent pneumococcal conjugate vaccine

Abstract

S. pneumoniae may cause serious invasive infections mainly in children and elderly adults leading to significant morbidity and mortality. This report describes the circulating serotypes and antimicrobial resistance of S. pneumoniae colonizing the nasopharynx of Cypriot children in 2007-2008 when the immunization coverage of children was still relatively low. The study focused on children between 6 months to 5 years of age in the Nicosia district. A nasopharyngeal specimen was obtained from 402 children who visited public immunization centers, public outpatient departments and the offices of private sector practicing pediatricians. The percentage of carriage was 35.3%. Intermediate and full resistance to penicillin was estimated at 39.4% and 1.4%, respectively. Intermediate and full resistance to erythromycin was estimated at 1.4% and 39.6%, respectively. Resistance to clindamycin was found to be 30.8%. MLSb was the dominant phenotype of resistance (77.2%). Multi-resistance was found amongst 24.1% of strains. Most frequent colonizing serotypes were 15B, 6B, 23A, 23B, 19F. The two vaccine serotypes 6B and 19F were highly resistant to both penicillin and erythromycin and were also multi-resistant at 27% and 50%, respectively. The percentages of fully immunized, partially immunized and non immunized children with the PCV7 were 24.6%, 14.3%, and 61.1%, respectively. Fully immunized children carried fewer vaccine serotypes in comparison with the non immunized children (p = .05). Some vaccine serotypes were among those more frequently colonizing children and exhibit significant resistance. An increase in vaccination coverage and prudent use of antimicrobials could have a significant impact on resistance.

Risk factors for carriage of Streptococcus pneumoniae in children

“…This phenomenon is attributed to the significant decrease in the presence of pneumococcal serotypes included in the vaccine as many of these serotypes are characterized by significant resistance to antimicrobials [ 6 ]. As it has been shown in our published study, two of the most frequent serotypes colonizing Cypriot children, specifically 6B and 19F, are vaccine serotypes and demonstrated a high percentage of resistance to both penicillin and erythromycin [ 13 ]. In Cyprus, coverage with the PCV7 vaccine at the time of the study was relatively low [ 12 ].…”

“…Data from the tri-annual survey performed in Cyprus by the Ministry of Health among children 17–24 months old in 2009, revealed full coverage by the PCV7 vaccine only in 37.5%, partial coverage in 42% and no vaccine coverage in 20.5% of children [ 12 ]. The susceptibility pattern and the circulating serotypes of S. pneumoniae isolated in Cypriot children have been reported elsewhere [ 13 ]. So far, no previous studies have been reported in Cyprus examining potential risk factors for colonization by pneumococcus in Cypriot children.…”