Antibiotic resistance and serotype distribution of Streptococcus pneumoniae colonizing rural Malawian children

• DOI: 10.1097/01.inf.0000069787.33960.d6
• Publication Date: 2011-04-11T07:54:05Z
• Authors: Daniel R. Feikin; Mollie Davis; Okey C. Nwanyanwu; Peter N. Kazembe; Lawrence M. Barat; Avril Wasas; Peter B. Bloland; Charles Ziba; Thora Capper; Robin E. Huebner; Ben Schwartz; Keith P. Klugman; Scott F. Dowell
• Keywords: Pneumococcal Conjugate Vaccine; Pneumococcal infections; Trimethoprim; Sulfamethoxazole

Nasopharyngeal swabs were taken from 906 Malawian children <5 years old visiting rural health clinics. Pneumococcal colonization was high, 84% among all children, and occurred early, 65% of it in <3 months old. Among pneumococcal isolates 46% nonsusceptible to trimethoprim-sulfamethoxazole, 21% penicillin. Trimethoprim-sulfamethoxazole use the previous month a risk factor for trimethoprim-sulfamethoxazole penicillin nonsusceptibility. Forty-three percent serotypes included 7-valent conjugate vaccine, 37% vaccine-related serotypes, particularly 6A 19A. In US >80% invasive disease is accounted by licensed vaccine (PCV7). 1 Because these seven also account >85% antibiotic resistance pneumococci PCV7 has been shown be highly efficacious against caused potential greatly decrease antibiotic-resistant US. 1, 2 However, Africa, where rates severe are much higher than US, lower proportion pediatric disease. As vaccines considered becomes important understand local patterns serotype distribution. Here we report on prevalence distribution colonizing nasopharynges children. Methods. The study took place town Dwanga, Malawi June October 1997. Children age weeks 59 who visited outpatient clinics eligible participation study. After their mother's informed consent obtained, nasopharyngeal initial visit week later as part prospective looking at after antimicrobial treatment. 3 only, before treatment given. protocol form approved Human Research Committees Centers Disease Control Prevention, Atlanta, GA; University Witwatersrand, Johannesburg, South Africa; Ministry Health. read language child's caretaker, written obtained enrollment. immediately inoculated onto horse blood agar plates containing 5 μg/ml gentamicin. Pneumococci identified alpha-hemolysis typical morphology confirmed optochin susceptibility. stored transported Africa Dorset egg media, they tested susceptibility broth microdilution. Standard National Committee Clinical Laboratory Standards cutoffs used define susceptible, intermediate resistant isolates. 4 Nonsusceptible defined those with or MIC values. Serotyping performed quellung reaction serotype-specific antisera (Statens Seruminstitut, Copenhagen, Denmark). completed 421 (61%) 694 majority (89%) isolates; remaining 11% nonviable unavailable serotyping Africa. addition convenience sample 25% susceptible serotyped. For statistical analysis, chi square test Fisher's exact compare proportions. greater percentage serotyped isolates, calculation total each adjusted weighting according (Table 1).TABLE 1: Percent trimethoprim-sulfamethoxazole-susceptible Streptococcus pneumoniae (CSSP), trimethoprim-sulfamethoxazole-nonsusceptible S. (CNSP), penicillin-susceptible (PSSP) penicillin-nonsusceptible (PNSP)Results. Of swabbed 761 (84%) colonized pneumococcus. Colonization began very early age; 15 (65%) 23 infants colonized. Subsequently percentages pneumococcus were: age, 58 69; 6 11 167 (87%) 192; 12 months, 256 (88%) 291; 24 265 (80%) 331. not significantly different age. that underwent testing, 322 (46%) (117 intermediate, 205 resistant), 146 (21%) (139 7 resistant) 150 (22%) tetracycline. Fewer 2% chloramphenicol erythromycin, rifampin clindamycin. Fifty-four more, 28% antibiotics more. both (35 57 vs. 287 637 did not; relative risk, 1.4, 95% confidence intervals, 1.1 1.7) (17 129 1.5; 1.0 2.3). Beta-lactam resistance. most commonly isolated (15%), 19A 23F (13%) 19F (12%) 1). Thirty-eight 48% least one covered PCV7. adjustment uneven sampling serotyping, 43% when including 80% Most this increase coverage because Forty-eight PCV7, which increased 83% serotypes. Discussion. This revealed several characteristics epidemiology first acquisition younger developed countries, other studies 5–7 pressure within year life great, likely Gambia. 8 Moreover occurs Malawi, young high. presents particular challenges prevention would given 6, 10 14 Expanded Program Immunization immunization schedule developing countries; delays timing childhood further group protected high occurring almost one-half finding line respiratory diarrheal infections recommended Although one-fifth penicillin-nonsusceptible, Recent pneumococci. latter Europe reflects occurrence multiply 9 such demonstration however, bacterial often still treated concern prophylaxis HIV-infected persons. contrast 19A, common accounting If efficacy extends types shown, confined handful serogroups (6, 14, 19 23). A limitation colonize nasopharynx might differ somewhat cause example rarely carried. two significant Another no information HIV status available. infection may alter suggest introduction could have impact colonization, population. Acknowledgments. We thank staff Matiki Health Clinic, Dwangwa; Community Science Unit, Health, Lilongwe; Lilongwe Central Hospital, Marshagne Smith, Cristel Graf Susanna Gomes dedicated field work. paper Charles Ziba.