Multiple Antimicrobial Resistance inHaemophilus InfluenzaeIsolates from Invasive Infections in Belgium (1983–1987)

SummaryBetween February 1983 and December 1987, 262 invasive isolates of Haemophilus influenzae were sent to the national reference laboratory in Belgium. Type b strains were more commonly isolated from children (95 %) than from adults (55%) (p < 0.0001). The prevalence of (lactamase production significantly increased from 18.5 % in 1983 to 35 % for the period 1986–1987 (p < 0.05) and was somewhat higher among type b strains (29.5 %) than among other isolates (22.5 %). A strong correlation was found between resistance to ampicillin, chloramphenicol and tetracycline. Eleven B-lactamasc producing strains (17%) were resistant to chloramphenicol (p < 0.001); all 13-lactamase negative strains were susceptible to chloramphenicol. Ampicillin resistant strains lacking 6-lactamase activity were not found. Monitoring the antimicrobial susceptibility of H. influenzae is an important component of a surveillance system for H. influenzae infections.