[Multicenter surveillance of Pseudomonas aeruginosa strains for antimicrobials in Aichi prefecture in 2009].

We investigated the susceptibility to antimicrobials of 204 Pseudomonas aeruginosa strains isolated from 21 hospitals in Aichi prefecture from September to November 2009. MIC distributions of various antimicrobials were analyzed in terms of geographic region of isolation, patient status (outpatient or inpatient), and type of specimens that the strain was isolated from. The results were as follows. 1. Although more than 90% of strains were susceptible to all aminoglycosides and colistin, 80-90% of them were susceptible to beta-lactams and fluoroquinolones. MIC distributions of all antimicrobials measured were not significantly different between regions. 2. Only 1 strain (0.5%) was multi-drug resistant Pseudomonas aeruginosa (MDRP). Thirteen strains (6.4%) showed imipenem MIC > or = 16 microg/mL, and 16 strains (7.8%) showed ciprofloxacin MIC > or = 4 microg/mL. These strains tended to be more isolated from urine, respiratory tract specimens, or surgical specimens. 3. The MICs of tazobactam/piperacillin, panipenem, meropenem, doripenem, biapenem, sulbactam/cefoperazone, cefepime, and aztreonam were significantly higher in strains isolated from inpatients than in those from outpatients. MIC distributions of antimicrobials other than beta-lactams were not significantly different between situations where strains were isolated. 4. MIC distributions of piperacillin, all carbapenems, cefepime, gentamicin, and all fluoroquinolones were significantly different among samples from which strains were isolated. The strains isolated from blood showed lower MICs against all antimicrobials than those from other samples. No difference was found in MIC distributions when categorized according to bacteremic origin. The MICs were apparently elevated against beta-lactams, fluoroquinolones, and gentamicin in strains isolated from respiratory tract specimens, and against beta-lactams, and fluoroquinolones in strains isolated from urine. It was suggested that in P. aeruginosa surveillance, the results should be reported by stratifying with patient status, and type of specimens that the strain was isolated from and that regional surveillance should be useful with such stratification to establish antibiograms for empirical antimicrobial choice.

[Etiological bacterial level in enterohemorrhagic Escherichia coli infection feces and chromogenic culture medium CHROMagar STEC usefulness].

We report a case of enterohemorrhagic Escherichia coli (EHEC) infection in which EHEC was not detected by culture on DHL agar medium. The proportion of EHEC bacterial count to enterobacterial count in feces was 1.7%, and the detection probability by 5-colony angling was low (8.1%). The probability of angling detection using CHROMagar STEC, a chromogenic medium for detecting EHEC, was high (100%). An additional and collection test was done using E. coli bacterial solutions to which two main sera groups--O157 and O26 were added. The maximum detectable level in the bacterial solution with O157 was 10(3)-10(4) CFU/mL in DHL and 10(2) CFU/mL in CHROMagar STEC. Bacterial solution levels with O26 were 10(3) CFU/mL in DHL and 10(2) CFU/mL in CHROMagar STEC. Assuming that the EHEC bacterial amount in feces of those with EHEC infection is low, we speculated that CHROMagar STEC may be useful as on EHEC screening medium.

Evaluation of selection media for the detection of borderline MRSA.

Recently, hospital-associated as well as community-acquired methicillin-resistant Staphylococcus aureus (MRSA) strains showing a low level of resistance to oxacillin have emerged worldwide, and as a result, a highly sensitive method to detect MRSA has become more important. To prevent MRSA being overlooked, some selection agar media have recently been developed. We evaluated six commercially available selection agar media in regard to the detection of 35 borderline MRSA (BOMRSA) strains which were mecA-positive but showed low resistance to oxacillin. The MIC values of oxacillin differed between the broth dilution method and the agar dilution method, and 11 of the 35 BOMRSA strains were judged as sensitive by the broth dilution method and 14 of the 35 strains were judged as sensitive by the agar dilution method. Thirty-two of the 35 strains were also judged as sensitive by an oxacillin disk diffusion test. Moreover, there was no consistent pattern of resistance to the tested beta-lactams among the BOMRSA strains. Some commercially available selection media designed for the detection of MRSA contain a beta-lactam antibiotic; oxacillin, ceftizoxime, or cefoxitin, and we evaluated media containing each of these agents. The detection sensitivities of cefoxitin-based agar media, such as CHROMagar MRSA and MRSA ID, for BOMRSA were 100% at 24-h culture. On the other hand, the media containing oxacillin or ceftizoxime gave lower results at 24 h, suggesting that, possibly, BOMRSA strains may not to be able to grow on these media. These results suggest that cefoxitin-based agar media should be recommended for the first-round screening of BOMRSA.

[Susceptibility surveillance of clinical isolates to fluoroquinolone antimicrobial agents from 2003 to 2008: post-marketing study of prulifloxacin].

Yearly changes in the susceptibility of clinical isolates to ulifloxacin (UFX) and other fluoroquinolones were examined through surveys over 3 periods. In the first survey, 534 strains derived from 19 species were collected from clinical specimens during 6 months from December 2003 to May 2004. In the same way, 805 strains were collected from December 2005 to May 2006 in the second survey, and 863 strains were from December 2007 to May 2008 in the third survey. Over these 3 study periods, the susceptibilities of fluoroquinolones against methicillin-susceptible Staphylococcus aureus and Escherichia coli were decreased. The isolation frequency of levofloxacin-nonsusceptible strain was increased from 0% to 11.8% and from 14.6% to 20.8%, respectively. MIC90s of UFX against these pathogens were also increased, but its MIC90 for E. coli was 2 to 4 times lower than that of levofloxacin. On the other hand, the susceptibility of strains of Klebsiella pneumoniae to UFX was increased. Among the fluoroquinolones tested, UFX showed the most potent activity against Pseudomonas aeruginosa, and no changes in the MIC90s occurred during the surveillance. Although one strain of Streptococcus pneumoniae isolated in the third study period showed levofloxacin-resistance (MIC, 8 microg/mL), there were nearly no changes in the MIC90s of any agents tested including UFX against S. pneumoniae during the surveillance. As for other bacterial species, a tendency to increase in resistance to UFX was not observed. The activity of UFX against Salmonella spp. and Shigella spp. was superior/equal to those of fluoroquinolones tested.

[Proposal for improving EQA programs in clinical microbiology by the Japanese Association of Medical Technologists].

External quality assessment (EQA) programs have been conducted by the Japanese Association of Medical Technologists (JAMT) since 1989. The nationwide EQA programs have provided feedback for improving clinical tests quality in individual laboratories. The participating laboratories have been expected to process the survey samples according to their usual practice for patient specimens. However, many problems relating to the EQA programs in clinical microbiology have been raised. Dishonesty in the responses, survey samples being handled in a manner that improves assessment results, surveys depending on volunteers because of time and cost limitations were some of the initial problems. In addition, the criteria used to evaluate the results were poorly understood, so that neither examiners not participants were clear as to how the evaluation worked. And finally, the nationwide EQA programs can detect only gross errors and use invalid methods for evaluating routine performances. They have been measuring only a few steps in specimens processing. To assess overall laboratory competence, other methods are needed. It is time to reform the JAMT nationwide EQA program to initiate real proficiency testing and to this end it is necessary to increase collaboration between JAMT and the regional associations of medical technologists, so that the improved testing program can be properly administered.

[Epidemiological study of outbreaks and sporadic cases due to Vibrio parahaemolyticus--serotype O3:K6 in Aichi Prefecture, Japan, during 1988 and 2001].

Percentage of the outbreaks by O3:K6 Vibrio parahaemolyticus (V. p) in Aichi Prefecture Japan increased from 3% (3/86) for 1988-95 to 75% (33/44) for 1996-2001. The percentage of the sporadic diarrhea cases caused by O3:K6 V. p in a general hospital in Aichi Prefecture also increased from 0% (0/253) to 61% (135/221) during the same periods. Thermostable direct hemolysin (TDH)-positive O3:K6 were isolated from 95% (19/20) of the outbreak incidents and 100% (135/135) of the sporadic cases. Only one TRH (TDH-related hemolysin)-positive O3:K6 was isolated from one outbreak incident. Percentage of the outbreaks by O3:K6 V. p associated with the consumption of boiled shellfishes increased from 5% (6/117) for 1988-95 to 25% (15/59) for 1996-2001, in particular, boiled crabs and squillas associated outbreaks increased from 2% (2/117) to 17% (10/59) and from 2% (2/117) to 10% (6/59), respectively. From 1,548 raw sea foods sampled in the Nagoya Central Wholesale Market in Aichi Prefecture in 1995-99, one TDH-positive O3:K6 was isolated from one live squilla (1/30). Increase in the percentage of outbreaks associated with TDH-positive O3:K6 V. p after 1996 in Aichi Prefecture was revealed to correlate with the increase in the outbreaks associated with consumption of boiled sea foods, especially boiled crabs as well as squillas. Accordingly, it becomes clear that sanitary handling of these boiled foods is important to prevent outbreaks and sporadic cases of diarrhea caused by O3:K6 V. p infection.