Aim: To study the resistance to strains of H. influenzae simultaneously isolated during 1990 in 10 Spanish cities with this being the second multicentric study carried out in Spain.
Methods: Three hundred eight strains of H. influenzae were consecutively isolated with less than 50% being from the respiratory tract. The sensitivity by microdilution in supplement Isosensitest was studied.
Results: Thirty-five percent of the strains were producers of beta-lactamase which predominate among those isolated in systemic infections and specially among those from Madrid (58.78%) and Barcelona (61.8%). The strains producing beta-lactamase were more resistant to all the antimicrobials than the non producers. Five point two percent of the strains were resistant to ampicillin by non enzymatic mechanisms. Resistance to chloramphenicol is frequent (28.6%) especially among strains producing beta-lactamase, strains of ocular origin and ORL (46%) and systemic infections (74.3%). The distribution is irregular, being more frequent in Seville (66.7%) and not detectable in Barcelona. Resistance to tetracycline is also usually linked to the production of beta-lactamase and not necessarily to that of chloramphenicol. Resistance to cotrimoxazole is the most frequent (67.5%) specially in Valladolid (87.5%). Resistance to cefaclor is of 60.7% being the most frequent among those isolated from ocular processes and ORL. Only 28 strains (9.1%) were sensitive to all the antimicrobials tested. Thirty-nine percent were multiresistant.
Conclusions: The authors found a slight increase in the high resistance detected in 1986. This increase was not uniform in all of Spain being significant in Madrid with producers of beta-lactamase, in Seville to chloramphenicol, to tetracycline in Bilbao and cotrimoxazole in Valencia.