[Haemophilus spp. antimicrobial susceptibility in Health Area 6 in Madrid, Spain (2000-2004)]

The aim of this study was to assess the antimicrobial susceptibility of 1370 Haemophilus spp. (1051 H. influenzae and 319 H. parainfluenzae) isolated during a 4-year period (July 2000 to June 2004) and to compare the results with other nationwide Spanish surveillance studies. The rate of isolation of H. parainfluenzae was significantly higher in clinical samples from the genitourinary tract (p <0.00001) and skin and soft tissues (p <0.00001), whereas H. influenzae was significantly more frequent in clinical respiratory tract samples (p <0.00001). A total of 46.2% and 31.8% of H. influenzae were isolated in infants and children of 2-6 years old, respectively; whereas 73.3% of H. parainfluenzae was isolated in patients older than age 14. Overall, 22.2% and 18.5% of the H. influenzae and H. parainfluenzae, respectively, were found to produce betalactamase. A total of 1.9% of betalactamase-negative H. influenzae were found to be resistant to ampicillin. Four strains (0.4%) of betalactamase-producing H. influenzae were resistant to amoxicillin-clavulanic acid, all isolated from infants. The rate of ampicillin susceptibility was significantly higher (p <0.01) in H. parainfluenzae than in H. influenzae. All of the 1370 strains of Haemophilus spp. were susceptible to cefotaxime and ciprofloxacin. The susceptibility to clarithromycin, trimethoprim-sulfamethoxazole, tetracycline, chloramphenicol and rifampin were 86.9%, 61.5%, 96.7%, 99.1% and 95.2% for H. influenzae versus 81.2%, 55.8%, 76.5%, 90,9% and 733% for H. parainfluenzae. In conclusion, H. influenzae is more resistant to ampicillin and H. parainfluenzae to non-betalactam antimicrobials. All isolates were susceptible to cefotaxime and ciprofloxacin.