[The antibacterial activity of fluoroquinolones against gram-negative bacteria isolated from Gifu Prefecture (2005)].

We investigated the susceptibility to 6 fluoroquinolones against 433 strains of Gram-negative bacteria isolated from 6 medical facilities in Gifu prefecture between January and September in 2005, determined by the agar dilution methods in according with the Japan Society of Chemotherapy. We also investigated the correlation between the degree of resistance to fluoroquinolones and the amino acid substitutions in the quinolone resistance-determining region (QRDR). The tested clinical isolates were as follows, Salmonella spp.; 17 strains, Escherichia coli; 112 strains Citrobacter freundii; 35 strains, Enterobacter cloacae; 31 strains, Klebsiella pneumoniae; 73 strains, Proteus spp.; 18 strains, Providencia spp.; 3 strains, Morganella morganii; 14 strains, Serratia marcescens; 27 strains and Pseudomonas aeruginosa; 103 strains. The number of the strains resistant to ciprofloxacin (CPFX) (MIC > or = 6.25 microg/mL) was twenty (E. coli; 14 strains, E. cloacae; I strain, Proteus spp.; 2 strains and P. aeruginosa; 3 strains). Among these strains, 12 strain (E. coli; 11 strains and E. cloacae; 1 strain) were highly resistant to CPFX (MIC > or =25 microg/mL). The E. coli strains highly resistant to CPFX had the multiple amino acid mutations in QRDR of ParC an GyrA. However in other strains, there was no strains possessing multiple mutations in both ParC and GyrA.

[Surveillance on Pseudomonas aeruginosa isolated in Gifu prefecture (2004)].

We analyzed Pseudomonas aeruginosa isolates in Gifu prefecture between September and October 2004. We conducted antimicrobial susceptibility test for 266 strains isolated from 8 medical institutes and 1 clinical laboratory, based on broth microdilution method. The MIC50 and MIC90 of piperacillin, amikacin, imipenem, and ciprofloxacin were 4 and 64, 4 and 8, 1 and 16, 0.25 and 8 microg/mL, respectively. The strains isolated from urine had higher MIC level in comparison with from sputum, which was remarkable in penicillins, cephalosporins and fluoroquinolones. We isolated 7 strains of multi-drug resistant Pseudomonas aeruginosa (MDRP), in which 3 strains showed under 16 microg/mL in MIC against anti-MRSA (methicillin-resistant Staphylococcus aureus) drug arbekacin. Continuous surveillance would be needed for antimicrobial resistance on P. aeruginosa in Gifu prefecture.

[Sensitivity surveillance of Streptococcus pneumoniae isolates for several antibiotics in Gifu prefecture (2004)].

We analyzed Streptococcus pneumoniae isolates in Gifu prefecture between November 2004 and December 2004. We analyzed isolates of 160 strains from 8 medical facilities to determine antibiotic susceptibility, genotype of penicillin-binding protein (PBP) genes and macrolide resistant genes, and the serotypes of penicillin-resistant S. pneumoniae (PRSP). When referred to the classification in CLSI (formerly NCCLS), the overall incidence of penicillin-susceptible (PSSP), penicillin-intermediate (PISP) and penicillin-resistant (PRSP) were 48 (30.0%), 81 (50.6%) and 31 (19.4%) strains, respectively, and the susceptibility distribution to benzylpenicillin showed triplet peaks. The incidence of PISP and PRSP was higher in the material of throat and nasal cavity, and area of Chuno and Gifu district. The sum of the incidence of PISP and PRSP was slightly higher in inpatient-derived stains than outpatient-derived strains. The incidence that didn't possess mutations in PBP genes and macrolide-resistant genes was 6 (3.75%) and the others 154 strain (96.25%) had abnormal PBP genes or macrolide-resistant genes. The 90% of pneumococcal serotypes of PRSP 31 strains were serotype 6 (14 strains, 45.2%), 19 (7 strains, 22.6%) and 23 (7 strains, 22.6%). The MIC90 of each antibiotics was as follows; 0.1 microg/mL for panipenem, 0.2 microg/mL for imipenem and tosufloxacin, 0.39 microg/mL for meropenem and gatifloxacin, 0.78 microg/mL for amoxicillin, cefteram and cefditoren, 1.56 microg/mL for piperacillin, cefcapene and levofloxacin, 3.13 microg/mL for flomoxef, 6.25 microg/mL for cefdinir and cefotiam, 12.5 microg/mL for norfloxacin and minocycline, 25 microg/mL for cefixime, and 100 microg/mL for clarithromycin.

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

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.