Antibiotic susceptibility of 206 Haemophilus influenzae isolates collected from children in central Italy

Isolation of antimicrobial resistant bacteria in upper respiratory tract infections of patients

Haemophilus influenzae, Streptococcus pyogenes, Moraxella catarrhalis, Staphylococcus aureus, and Streptococcus pneumoniae are usual cause of upper respiratory tract infection cases. The present study aims the isolation of bacterial strains which are resistant to the commonly prescribed antibiotics. In total, 900 throat swabs were obtained from the patients suffering from upper respiratory tract infections residing in three different localities. The maximum number of isolates (64 %) were obtained from locality-1 (L-1), whereas lowest isolates were found in second locality (L-2). H. influenzae was found to be the most dominant bacterial pathogen in upper respiratory tract infections in patients with 42 % of the total isolates. H. influenzae and Chlamydia pneumoniae were resistant to β-lactam antibiotics but susceptible to fluroquinolones and aminoglycosides, whereas S. aureus and S. pneumoniae were found to be highly resistant to β-lactam, aminoglycosides and fluroquinolones. S. aureus was also moderately resistant to fluroquinolones and aminoglycosides with percent resistance of 26, 33 and 18 %, respectively. 56 % S. pneumoniae isolates were resistant against erythromycin, 27 % against chloramphenicol and 23 % against cefuroxime. The studies revealed that S. aureus and S. pneumoniae strains were high producer of biofilms which could be one of the reasons for their high pathogenicity.

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.