ANTIBIOTIC SUSCEPTIBILITY AND BIOTYPES OF CLINICAL ISOLATES OF HAEMOPHILUS-INFLUENZAE

The susceptibility of 200 strains of Haemophilus influenzae isolated from patients seen in the Riyadh University Hospitals to various antibiotics was determined using the agar dilution method. The antibiotics tested included ampicillin, chloramphenicol, tetracycline, cotrimoxazole, cephamandole, cefotaxime, ceftazidime, moxalactam and ceftriaxone. Ampicillin resistance was seen in 15% of the strains, 80% of which were found to be beta-lactamase producers. Resistance to other antibiotics was as follows: chloramphenicol 5.5%, tetracycline 10.5% and cotrimoxazole 1.5%. All the strains were susceptible to the second and third generation cephalosporins. Biotyping of the strains showed biotype II H. influenzae to be the most common biotype isolated and biotype Ill to be the most resistant to antibiotics.