Carriage prevalence, serotype distribution, antimicrobial resistance, pspA typing and pilus islets of Streptococcus pneumoniae isolated from adults living in a Brazilian urban slum.

Abstract

For Brazilian adults, pneumococcal vaccines have been usually taken only by those who are at higher risk for development of pneumococcal diseases. Since populations from lower socioeconomic status are at high risk of acquiring pneumococcal infections, we investigated the carriage prevalence, colonization risk factors, capsular and surface protein types, and antimicrobial resistance among pneumococcal isolates recovered from adults living in a Brazilian urban slum. Between September-December 2016, we conducted a cross-sectional study among individuals aged≥18years who attended a public primary clinic in Niterói/RJ, Brazil. Pneumococci were isolated by culture on sheep blood agar plates with and without gentamicin. Antimicrobial susceptibility was determined for all isolates. We used PCR to determine capsular types, PspA families (Fam) and pilus islets (PI). Of 385 adults, 32 (8.3%) were pneumococcal carriers. Three carriers had two different pneumococci, totaling 35 isolates. After multivariate analysis, smoking, previous hospitalization, alcohol consumption and co-habitation with children aged<6years increased the odds of pneumococcal carriage, but antibiotic use in the previous 2weeks was found to be a protective factor. Fourteen different serogroups/serotypes were detected and the prevalent ones were 9N/L, 10A, 15B/C and 35F/47F (n=3; 8.6% each). Non-typeable (NT) isolates made up 31.4%. All isolates were susceptible to chloramphenicol, levofloxacin and vancomycin. We found eight (22.9%) penicillin non-susceptible pneumococci (PNSP) with minimum inhibitory concentrations (MICs) of 0.38-1.5μg/mL. The two (5.7%) erythromycin-resistant isolates had MIC>256μg/mL, cMLSB phenotype and the erm(B) gene. Twelve (34.3%) and 17 (48.6%) isolates had PspA Fam1 and Fam2, respectively. Three (8.6%) isolates had genes for pilitwo PI-1 and one PI-2. We detected a low frequency of pneumococcal carriage among the adult population, but a high diversity of serotypes. Frequencies of PNSP and NT isolates resistant to antimicrobial agents are concerning.