Caracterizacion y resistencia de las cepas de H. influenzae y H. parainfluenzae aisladas de la nasofaringe de portadores

Introduction. H. influenzae (Hi) and H. parainfluenzae (Hp) are part of the normal flora of the respiratory tract. Hi carriage rate is largely variable (10-60%) and detection depends on the methodology, age group and size of the studied universe. Children under five years of age are colonized by this species (10-50%). Serotype b is associated to different syndromes, and in Mexico it causes 20 to 45% of all bacterial meningoencefalitis and in respiratory infections it causes high infant morbidity and mortality. Hp has been found associated to meningitis, arthritis, epiglottitis and pneumonia. Objective. To characterize Hi and Hp, isolated from children under five years age, through biochemical serological, antimicrobial disk susceptibility and beta lactamase tests. Material and methods. Nasopharyngeal carriage (770) from children under five years of age were cultured in chocolate bacitracin agar. Biotype differentiation, through biochemical tests, was performed. Confirmation coagglutination (Phadebact test) was used to serotype Hi from culture. Beta lactamase testing through three different methods and antibiotic susceptibility (modified Kirby-Bauer) was performed. Results and discussion. The incidence of nasopharyngeal carriage of Hi and Hp were 23.7% and 16.5% respectively; out of the 159 strains isolated 93 were Hi and 66 Hp. Biotypes V (22.6%) and II (22.4%) of Hi were the most frequently found; of serotypes b, 30.1%; a, 8.6% and the of other (c,d,e,f), 1.82 were recovered. The nontypeable strains were the highest in percentage (43.0%). Beta lactamase activity was also tested: 27.0% for Hi and for Hp 18.0%. A 14.0% resistance to penicillin in strains isolated from children was reported by Guiscafre et al vs 16.0% found in the present study; also, 5% of Hi was resistant to cloramphenicol vs the 52% informed, in Spain, by Campos et al. Ticarciline/clavulanic acid sensitive was 100.0%; to second and third generation cephalosporins it was 97% and 95% respectively. Hp proved to be the more resistance to all antibiotics tested. Hi type b is one of the main causes of invasive disease, 3.0% to 10% prevalence was reported; in contacts of patients with this illness and in Hi b carriers it was higher. In Mexico, 32.0% of intrafamily contacts of a single meningitis case were infected. Pediatric nasopharyngeal carriage of Hi b and nontypeable Hi (NT Hi) varying from 3.0 to 10.0% and of 15.0% to 85.0% respectively were reported by Villasenor. In this study, NT Hi was found very frequently (43.0%). Beta lactamase detection is of great clinical helps since it can be performed either through cultures of directly from body fluids (like cerebrospinal fluid), and this allows the physician to apply appropriate therapeutic methods even before receiving the culture results. Conclusions. H. influenzae is an etiological agent of severe infections in children, and day-care- centers are risky areas due to the high possibility of bacterial spreading among the susceptible population,, it therefore evident that more epidemiological studies are required to avoid lethal consequences.