Susceptibility and genetic relatedness of invasive Haemophilus influenzae type b in Italy.
Haemophilus influenzae type b (Hib) still causes a large portion of meningitis in children less than 5 year old in Italy because vaccination against this agent has not been fully implemented in the country. We have studied 78 Hib strains and 4 nontypable H. influenzae (NTHi) isolated from the cerebrospinal fluid of subjects with meningitis for susceptibility to ampicillin, chloramphenicol, and ceftriaxone. The macrorestriction profiles of chromosomal DNA obtained by pulsed-field gel electrophoresis (PFGE) following digestion with SmaI and ApaI were also determined. All strains except one were equally susceptible to the antibiotics tested. One Hib strain, the only beta-lactamase producer, showed an intermediate susceptibility to ampicillin (MIC = 2 microg/ml), while maintaining full susceptibility to chloramphenicol and ceftriaxone. The analysis of the PFGE patterns showed that most of the Hib isolates, including the beta-lactamase-positive Hib strain, belonged to the same clone or to closely related subclones. For three PCR-confirmed NTHi isolates, we obtained completely different PFGE profiles. In conclusion, resistance to ampicillin still appears to be a rare finding in Hib strains causing meningitis in Italy; moreover, PFGE showed that the population structure of invasive Hib is essentially clonal.
Tarasi
A
A
Istituto Superiore di Sanità, and Divisione di Clinica Medica III, Università La Sapienza, Rome, Italy.
D'Ambrosio
F
F
Perrone
G
G
Pantosti
A
A
D000328:Adult; D000667:Ampicillin / Q000494:pharmacology; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002443:Ceftriaxone / Q000494:pharmacology; D002648:Child; D002675:Child, Preschool; D002701:Chloramphenicol / Q000494:pharmacology; D004269:DNA, Bacterial / Q000032:analysis; D004352:Drug Resistance, Microbial; D004587:Electrophoresis, Agar Gel; D019741:Haemophilus influenzae type b / Q000187:drug effects / Q000201:enzymology / Q000235:genetics* / Q000302:isolation & purification; D006801:Humans; D007223:Infant; D007558:Italy; D016920:Meningitis, Bacterial / Q000201:enzymology / Q000235:genetics / Q000382:microbiology; D008826:Microbial Sensitivity Tests; D008875:Middle Aged; D001618:beta-Lactamases / Q000032:analysis