Streptococcus pneumoniae: Low frequency of penicillin resistance and high resistance to trimethoprim-sulfamethoxazole in nasopharyngeal isolates from children in a rural area in Mexico

RESUMO

Due to the changes in the frequency of penicillin resistant strains of S. pneumoniae, it is necessary to perform suveillance stuies of bacterial resistance. Isolates from the upper respiratory tract of asymptomatic children have been useful. There is no information about the difference between isolates from children with and without upper respiratory tract infection (URTI). The objective of the authors in this paper is to establish the prevalence of carrier state, serotype and antimicrobial resistance of S pneumoniae isolates from children with and without acute upper respiratory tract infection (URTI) in a rural area in Mexico. A cross-sectional comparative study was performed in Tlaxcal, Mexico. Children from one month 5 years of age were included. Nasopharyngeal swabs were obtained. Identification was done by international microbiology standards. Serotyping was done by the capsular Quellung test. The susceptibility testing was performed by the agar dilution mehtod. Four-hundred and fifty patients were included. S pneumoniae was isolated in 134 children (29.7 percent). Frequency of carriers was greater in patients with URTI (107/323) than without URTI (27/127) (33.1 percent vs.21.1 percent p=0.012, OR 1.84, IC 95 percent 1.1 - 3.08). The six most frequent serotypes were: 6B (16.4 percent); 19F (11.9 percent); 19A (6.7 percent)Ñ 14, 23 F, and 35 (5.2 percent each), with no difference among the groups. Only 3 percent of the strains had high level resistance to penicillin, and 12.6 percent had intermediate resistance, and for ampicillin 4 percent, amoxicillin 4 percent, amoxicillin/clavulanate 4 percent, ceftriaxone 3 percent, cefotaxime 1.5 percent, erythromycin 6 percent, miocamycin 0 percent. trimethoprim/sulfamethoxazole resitance was very high (42 percent). In conclusion, colonization is higher in children with URTI. Five of the most frequent serotypes identified in this study were the same as those identified in patients with S. pneumoniae invasive diseases in mexico City. In Tlaxcala, Mexico, betalactams could be the drug of choice for the treatment of S. pneumoniae lower respiratory tract infections. It is necessary to perform clinical assays to evaluate the efficacy of trimethoprim-sulfamethoxazole due to the high resitance in vitro