Present Status of Antimicrobial Susceptibility of Haemophilus influenzae Isolates in Kuwait as Determined by E-Test

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Abstract
Objective: To study antimicrobial susceptibility pattern of clinical isolates of Haemophilus influenzae using E-test and compare the results with those of a study done in 1983. Methods: The antimicrobial susceptibility of 196 isolates of H. influenzae against nine antimicrobial agents (amoxicillin-clavulanic acid, ampicillin, cefaclor, cefotaxime, ceftriaxone, chloramphenicol, ciprofloxacin, clarithromycin, and trimethoprim-sulfamethoxazole) was performed by E-test on Haemophilus test medium. The results obtained were compared with those from an earlier study conducted here on 108 strains collected between October and December 1983. Results: Except for cefotaxime, which consistently showed an excellent in vitro activity (MIC90 = 0.047 mg/l), other antimicrobial agents presented a decline in their effectiveness. Among the newer antibiotics tested, all the strains were found to be sensitive to ciprofloxacin (MIC range = 0.004–0.0094 mg/l) whereas clarithromycin showed high MIC of 12 mg/l for 90% of the strains. There was a marked increase in the number of beta-lactamase-producing isolates from 4.6% in 1983 to 31.6% in the present study. Amongst 62 beta-lactamase-producing strains 14.5% exhibited resistance to amoxicillin-clavulanic acid (MIC >8 mg/l). Only 3.1% isolates were found to be of capsular type b in 1998 compared to 9.2% in 1983. No beta-lactamase-negative ampicillin-resistant (BLNAR) strain was isolated during the present study whereas only one strain (0.9%) was isolated in 1983. Conclusion: This study shows that despite a decrease in the number of type b and BLNAR H. influenzae isolates, there is an apparent increase in the trend to acquire resistance to several antimicrobial agents.

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