狩山 玲子

In 2000, chlamydial strains OK133 and OK135 were isolated from 2 female patients with cervicitis. These strains were unresponsive to commercially available PCR and LCR test kits for the diagnosis of Chlamydia trachomatis infection, and their phenotypic characteristics were very similar. The OK135 nucleotide sequence in MOMP-VD2 gene closely resembled that of Chlamydophila caviae GPIC. A similar strain was isolated in 2003 from a male patient OKM2 with urethritis, from which the strain SC10-6 was cloned by the plaque purification method. The nucleotide sequence of the entire MOMP gene of SC10-6 was exactly the same as that of OK135. Thus, the strains OK135 and SC10-6, together with OK133, have been called C. caviae-like Chlamydia. We designed primers for nested PCR assay, the product of which showed a single-band 311-bp fragment, to detect C. caviae-like Chlamydia. Of swab specimens obtained from 202 patients from 2003 to 2006 (119 male and 83 female patients), 18 specimens (8.9%) from 14 male and 4 female patients were positive, suggesting that C. caviae-like Chlamydia infection is rather common. Thus far, it has not been determined whether C. caviae-like Chlamydia is pathogenic for humans.

Staphylococci have been confirmed to form biofilms on various biomaterials. The purpose of this study was to investigate biofilm formation among methicillin-resistant Staphylococcus aureus (MRSA) isolates from patients with urinary tract infection (UTI) and to assess the relationship between biofilm-forming capacities and virulence determinants/clinical background. Over a 12-year period from 1990 through 2001, a total of 109 MRSA isolates were collected from patients (one isolate per patient) with UTI at the urology ward of Okayama University Hospital. We used the in vitro microtiter plate assay to quantify biofilm formation. We then investigated the presence of several virulence determinants by polymerase chain reaction assay and found eight determinants (tst, sec, hla, hlb, fnbA, clfA, icaA, and agrII) to be predominant among these isolates. Enhanced biofilm formation was confirmed in hla-, hlb-, and fnbA-positive MRSA isolates, both individually and in combination. Upon review of the associated medical records, we concluded that the biofilm-forming capacities of MRSA isolates from catheter-related cases were significantly greater than those from catheter-unrelated cases. The percentage of hla-, hlb-, and fnbA-positive isolates was higher among MRSA isolates from catheter-related cases than those from catheter-unrelated cases. Our studies suggest that MRSA colonization and infection of the urinary tract may be promoted by hla, hlb, and fnbA gene products.

The potential relationships between biofilm formation and pathogenicity of Enterococcus faecalis in urinary tract infections (UTI) were investigated. Over a 12-year period from 1991 through 2002, a total of 352 E.faecalis isolates were collected from patients with complicated UTI (one isolate per patient) at the urology ward of Okayama University Hospital. We analyzed the prevalence and transferability of genes encoding virulence factors(asa1, esp, cylA, gelE /sprE )and antimicrobial resistance(aac(6') /aph(2'')). The production of biofilm, hemolysin and gelatinase by these isolates was also examined and the associated medical records of patients were retrospectively reviewed. Of 352 E. faecalis isolates, 315 possessed and/or genes. Of the 63 hemolysin- and 167 gelatinase-producing isolates, 59 and 94 isolates, respectively, possessed both asa1 and esp genes. E. faecalis isolates with both asa1 and esp genes formed biofilms at significantly higher rates than those with neither gene (P=0.038). The genes encoding asa1, cylA , and aac(6') /(aph(2'') were transferable and appeared to have accumulated in these isolates. The E. faecalis isolates possessing asa1 and/or esp genes were found from both catheter-related or -unrelated UTI. Our study indicates that E. faecalis isolates that have accumulated virulence genes are apt to form persistent biofilms in the urinary tracts.

Ulifloxacin is the active form of the prodrug prulifloxacin and shows a highly potent antipseudomonal activity. In this study, we examined the combined effect of fosfomycin and ulifloxacin against Pseudomonas aeruginosa (P. aeruginosa) growing in a biofilm using a modified Robbins device with artificial urine, and compared it to that of the combination of fosfomycin and ciprofloxacin or levofloxacin. An ATP bioluminescence assay was used to evaluate the antibacterial activity of the agents against sessile cells in a mature biofilm developed on a silicon disk. The total bioactivity of P. aeruginosa growing in a biofilm that had not been fully eradicated by fosfomycin or any of the fluoroquinolones alone at 10 times the MIC decreased after combination treatment with fosfomycin and fluoroquinolones. Morphological changes occurred in a time-dependent fashion; namely, swollen and/or rounding cells emerged within a couple of hours after combination treatment, marking the initial stage in the process leading to the destruction of the biofilms. We could not find any difference among the 3 fluoroquinolones with regard to their synergistic effects when administered with fosfomycin. The combination treatment of fosfomycin and fluoroquinolones with highly potent antipseudomonal activities was effective in eradicating sessile cells of P. aeruginosa in the biofilm and promises to be beneficial against biofilm-associated infectious diseases.

Urinary tract infections (UTIs) due to fluoroquinolone-insusceptible Escherichia coli have become increasingly common in recent years. We investigated the potential relationships between clinical measures to combat fluoroquinolone-insusceptible E. coli and experimental analyses on E. coli isolates. Over a 14-year period from 1994 through 2007, a total of 828 E. coli isolates were collected from patients (one isolate per patient) with UTI at the urology ward of Okayama University Hospital. We analyzed the mutations in quinolone resistance-determining regions of DNA gyrase (gyrA) and topoisomerase IV (parC). The production of biofilm by these isolates was also examined and the associated medical records were retrospectively reviewed. Seven of 189 (3.7%) strains from uncomplicated UTIs and 82 of 639 (12.8%) strains from complicated UTIs were insusceptible to fluoroquinolones. Amino acid replacements of type II topoisomerases were frequently observed at positions 83 and 87 in GyrA and at positions 80 and 84 in ParC. No significant difference in the biofilm-forming capabilities was observed between fluoroquinolone-susceptible and -insusceptible E. coli. Our study suggests that biofilm formation of fluoroquinolone-insusceptible E. coli isolates is not a major mechanism of resistance in patients with UTI.