RESUMEN
A polymerase chain reaction (PCR) assay with primers from 'bexA' gene was compared with culture for the detection of Haemophilus influenzae type b (Hib) in clinical samples from children with pneumonia and meningitis. Of 200 sera (180 from pneumonia, 20 from non-pneumonia patients) tested by PCR (serum-PCR), Hib was detected in 15 of 16 blood culture-positive and in 6 blood culture-negative pneumonia cases. When compared with the results of blood culture, serum-PCR had sensitivity, specificity, and accuracy index of 93.7%, 96.7%, and 96.5% respectively. Of 120 cerebrospinal fluid (CSF) samples from meningitis patients tested by culture and PCR (CSF-PCR), the latter method could detect Hib in all 15 culture-positive and in 8 of 105 culture-negative cases, showing sensitivity, specificity, and accuracy index of 100%, 92.4%, and 94.4% respectively. The PCR result was available within a day. Antimicrobial susceptibility of Hib was determined by the disc-diffusion method. High rate of resistance to ampicillin (54.8%), chloramphenicol (48.4%), and co-trimoxazole (80.6%) was observed among 31 invasive Hib isolates with resistance to all 3 drugs (multiresistance) in 48.4% of the isolates. All the Hib isolates were susceptible to ceftriaxone. The study has shown that PCR is a rapid, sensitive and specific diagnostic test for Hib from clinical samples, and a combination of culture and PCR is necessary for the detection of Hib infections to the maximum extent for case management to reduce morbidity, mortality, and complications of the invasive Hib infections. A high prevalence of multiresistant Hib strains is a matter of concern.