Antibiotic resistance and clinical significance of Haemophilus influenzae type

Objectives: Little is known about the antibiotic susceptibility and clinical significance of non-type b capsu-lated Haemophilus influenzae. We studied the antibiotic resistance patterns, plasmid carriage and clinical features of H. influenzae type f infections in Spain during 1996–2002. Patients and methods: Forty-nine H. influenzae type f recovered from Spanish hospitals were analysed at a central laboratory where full microbiological and molecular epidemiological studies were carried out. Anti-microbial susceptibility testing was performed in accordance with NCCLS guidelines. Results: Twelve strains (24.5%) were resistant to ampicillin and 22 (44.9%) to co-trimoxazole. Decreased susceptibility to clarithromycin, tetracycline, chloramphenicol and rifampicin was found in 16.3%, 12.2%, 14.3 % and 2 % of strains, respectively. Multidrug resistance was present in nine (18.4%) of the 49 isolates. The most prevalent resistance phenotype was ampicillin/tetracycline/co-trimoxazole/chloramphenicol, which was detected in five isolates. All six strains that were simultaneously resistant to ampicillin, tetracy-cline and chloramphenicol had conjugative plasmids. The main clinical diagnoses were pneumonia (32.6%)