Nasopharyngeal carriage, serotype distribution and antimicrobial resistance of Streptococcus pneumoniae among children from Brazil before the introduction of the 10-valent conjugate vaccine

Abstract

BackgroundStreptococcus pneumoniae remains a major cause of childhood morbidity and mortality worldwide. Nasopharyngeal colonization plays an important role in the development and transmission of pneumococcal diseases, and infants and young children are considered to be the main reservoir of this pathogen. The aim of this study was to evaluate the rates and characteristics associated with nasopharyngeal carriage, the distribution of serotypes and the antimicrobial resistance profiles of Streptococcus pneumoniae among children in a large metropolitan area in Brazil before the introduction of the 10-valent pneumococcal conjugate vaccine.MethodsBetween March and June 2010, nasopharyngeal swabs were collected from 242 children aged <6 years attending one day care center and the emergency room of a pediatric hospital. Pneumococcal isolates were identified by conventional methods and serotypes were determined by a sequential multiplex PCR assay and/or the Quellung reaction. The antimicrobial susceptibilities of the pneumococci were assessed by the disk diffusion method. MICs for erythromycin and penicillin were also performed. Erythromycin resistance genes were investigated by PCR.ResultsThe overall colonization rate was 49.2% and it was considerably higher among children in the day care center. Pneumococcal carriage was more common among day care attenders and cohabitants with young siblings. The most prevalent serotypes were 6B, 19F, 6A, 14, 15C and 23F, which accounted for 61.2% of the isolates. All isolates were susceptible to clindamycin, levofloxacin, rifampicin and vancomycin. The highest rate of non-susceptibility was observed for sulphamethoxazole-trimethoprim (51.2%). Penicillin non-susceptible pneumococci (PNSP) accounted for 27.3% of the isolates (MICs of 0.12-4 μg/ml). Penicillin non-susceptibility was strongly associated with serotypes 14 and 23F. Hospital attendance and the presence of respiratory or general symptoms were frequently associated with PNSP carriage. The two erythromycin-resistant isolates (MICs of 2 and 4 μg/ml) belonged to serotype 6A, presented the M phenotype and harbored the mef(A/E) gene.ConclusionsCorrelations between serotypes, settings and penicillin non-susceptibility were observed. Serotypes coverage projected for the 10-valent pneumococcal conjugate vaccine was low (45.5%), but pointed out the potential reduction of PNSP nasopharyngeal colonization by nearly 20%.

Nasopharyngeal carriage of Streptococcus pneumoniae among children in an urban setting in Brazil prior to PCV10 introduction

“…The younger the patient, the greater the chance of pneumococcal colonization [22]. Although, variability in carriage rates were not observed in different age groups from this study population, in general, the observed carriage rate is in agreement with previous studies conducted in others Brazilian cities [7, 23]. …”

“…The serotype distribution among nasopharyngeal isolates in the present study was similar to that found in previous studies in Brazil [7–9, 23] and other countries in Latin America and Europe [28, 29]. Overall, the serotypes isolated from the nasopharynx included the most common serotypes causing invasive disease [30] and represented in the PCV-10 vaccine (~ 52%).…”

“…Likewise, increasing resistance has already been documented in invasive disease in Salvador, with rates growing from 15% (1999) to 22.2% (2007) [30, 34]. Geographical variations in the frequency of antibiotic resistance have been observed in different regions of Brazil and others countries [7, 23, 35, 36], and these differences may reflect, in part, true geographical differences in antibiotic resistance rate, but most likely reflect differences due to investigation methodology and populations sampled.…”

Potential of MALDI-TOF MS as an alternative approach for capsular typing Streptococcus pneumoniae isolates

“…On the other hand, serotypes 6C and 9N are not present in any of the available conjugate vaccines and, thus, have the potential to emerge in this scenario2. Indeed, the emergence of serotype 6C has been detected in the USA after PCV7 implementation1415.…”

“…The isolates were previously identified by phenotypic tests, including observation of colony morphology and type of hemolysis on blood agar plates; cellular characteristics after Gram stain; optochin susceptibility and bile-solubility11. The capsular types were previously determined for all 416 strains by the Quellung reaction with antisera kindly provided by the Streptococcus Laboratory at the Centers for Disease Control and Prevention (CDC, GA, USA), and also by multiplex PCR for a fraction of the isolates121314151617.…”