Surveillance based on molecular epidemiology for Haemophilus influenzae Isolates in Gifu Prefecture

Abstract

We analyzed Haemophilus influenzae isolates in Gifu prefecture between May 2003 and August 2003. We conducted molecular-level epidemiological studies for 313 strains using PCR to identify resistant genes in H. influenzae. Our four sets of primers are as follows: (i) p6 gene of P6 membrane protein, (ii) TEM-1 type beta-lactamase gene (bla), (iii) normal PBP 3 gene (ftsl), and (iv) mutational ftsl gene detected in beta-lactamase-nonproducing ampicillin (ABPC) resistant H. influenzae (BLNAR). H. influenzae strains were classified into 6 types based on PCR: (i) beta-lactamase-nonproducing ABPC-susceptible strains (BLNAS; n = 85) with no any resistant genes, (ii) TEM-1 type beta-lactamase-producing ABPC resistant strains (BLPAR; n = 6), (iii) beta-lactamase-nonproducing and low-level ABPC-resistant strains (Low-BLNAR; n = 77) possessing Asn-526 --> Lys-526 amino acid substitution, (iv) BLNAR strains (n = 138) possessing Asn-526 --> Lys-526 and 3 amino acids substitutions detected around the Ser-Ser-Asn conserved motif, (v) beta-lactamase-producing amoxicillin-clavulanate resistant strains (BLPACR-I; n = 3) possessing TEM-1 and Low-BLNAR resistant genes, and (vi) beta-lactamase-producing amoxicillin-clavulanate resistant strains (BLPACR-II; n = 4) possessing TEM-1 and BLNAR resistant genes. Amoxicillin (AMPC) MIC90s in Low-BLNAR was 4 microg/mL and in BLNAR was 16 microg/mL. In oral cephalosporins, cefditoren MIC90 was the most excellent with 0.5 microg/mL against BLNAR. The prevalence of H. influenzae type b isolates in Matsubara Otorhinolaryngology Clinic was 66.7%. Selection of appropriate antimicrobial agents should be performed to prevent resistant microorganisms. Also, the vaccination for H. influenzae type b would be strongly recommended in near future.