No abstract

Raw vegetables cut for salad, cooked salad, cooked rice, boiled noodles, bean curd, and cooked Japanese foods were purchased in 27 retail shops in Tokyo. Intact vegetables before being processed and ready-to-eat fresh salad products were obtained from two food factories located in the suburbs of Tokyo. Two hundred thirty-eight retail samples, 137 samples of intact vegetables, and 159 samples of fresh products were examined for aerobic plate count (APC), coliforms, Escherichia coli, Listeria spp., Staphylococcus aureus, and Bacillus cereus. The APC of retail foods were 2.1 to 5.7 log CFU/g, and the range for the coliforms was 0.1 to 2.3 log CFU/g. The APC and coliform values showed that the raw vegetables cut for salad were the most heavily contaminated among the six kinds of ready-to-eat foods examined. Although L. monocytogenes was not detected, two samples of raw vegetables and five kinds of cooked foods yielded Listeria spp. S. aureus was detected in one sample of Japanese cooked food. The APC of the intact vegetables were 2.9 to 7.3 log CFU/g upon arrival and 2.2 to 7.2 log CFU/g after 3 days storage at 10 degrees C. The APC of the fresh products were 3.4 to 7.6 log CFU/g upon arrival and 4.7 to 8.7 log CFU/g after 3 days storage at 10 degrees C. The isolation rates for coliforms were 6.1 to 50% for intact vegetables and 50 to 66.7% for fresh products. E. coli was detected only in the fresh products. B. cereus was isolated from 20.1% (17 of 81) of the intact vegetables and 9.2% (8 of 87) of the fresh products.

AmpC regulatory genes in 21 ceftazidime-resistant clinical isolates of Enterobacter cloacae (MICs of ≥16 μg/ml) were characterized. All isolates exhibited AmpC overproduction due to AmpD mutation. Additionally, we found two AmpR mutants among the isolates. This is the first report of chromosomal ampR mutation in clinical isolates of E. cloacae .

Campylobacter jejuni was isolated from 44 of 313 free-living birds from Japan. The highest isolation rate was found in 30 of 87 (34%) crows (Corvus levaillanti and Corvus corone), followed by 2 of 10 (20%) blue magpies (Cyanopica cyanus), 5 of 35 (14%) gray starlings (Sturnus cineraceus), 2 of 16 (13%) domestic pigeons (Columbia livia domestica), 4 of 36 (11%) bulbuls (Hypsipetes amaurotis), and 1 of 62 (2%) eastern turtledoves (Streptopelia orientalis). One-fourth of the contents of the crop and stomach of the crows was human refuse. One-third of the crop and stomach contents of gray starlings and blue magpies consisted of insects. More than one-half of the contents of bulbuls and eastern turtledoves were seeds and plant material. These differences in food habits may be a primary factor in the varying prevalence of C. jejuni in these respective avian species.

A clinical isolate of Escherichia coli from a patient in Japan, isolate KU6400, was found to produce a plasmid-encoded ␤-lactamase that conferred resistance to extended-spectrum cephalosporins and cephamycins. Resistance arising from production of a ␤-lactamase could be transferred by either conjugation or transformation with plasmid pKU601 into E. coli ML4947. The substrate and inhibition profiles of this enzyme resembled those of the AmpC ␤-lactamase. The resistance gene of pKU601, which was cloned and expressed in E. coli, proved to contain an open reading frame showing 99.8% DNA sequence identity with the ampC gene of Citrobacter freundii GC3. DNA sequence analysis also identified a gene upstream of ampC whose sequence was 99.0% identical to the ampR gene from C. freundii GC3. In addition, a fumarate operon (frdABCD) and an outer membrane lipoprotein (blc) surrounding the ampR-ampC genes in C. freundii were identified, and insertion sequence (IS26) elements were observed on both sides of the sequences identified (forming an IS26 composite transposon); these results confirm the evidence of the translocation of a ␤-lactamase-associated gene region from the chromosome to a plasmid. Finally, we describe a novel plasmid-encoded AmpC ␤-lactamase, CFE-1, with an ampR gene derived from C. freundii.