Ken-ichi Kaneko

Bacterial contamination of ready-to-eat foods and fresh products in retail shops and food factories

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.

Significant increase in antibiotic resistance of Salmonella isolates from human beings and chicken meat in Thailand

A total of 1715 Salmonella strains, including 600 S. enteritidis, 290 S.derby, 257 S. Weltevreden, 122 S. 1,4,5,12:i:-, 235 S. anatum, and 211 S. typhimurium, originating from 1308 human beings and 407 frozen chicken meat specimens collected in 1993 and 1994 were tested for antibiotic resistance. The disk diffusion method was used with nine disks of chloramphenicol, ceftriaxone, amikacin, kanamycin, ampicillin, sulfamethoxazole plus trimethoprim, nalidixic acid, gentamicin and ofloxacin. The resistance rates of human beings isolates in 1994 to ceftriaxone, amikacin and kanamycin were, respectively, 10.7%, 8.6%, 17.8% in S. enteritidis; 23.1%, 17.3% 33.0% in S. derby; 30.9%, 40.2%, 60.4% in S. weltevreden; 16.1%, 17.7%, 70.9% in S.1, 4, 5, 12:i:-; 25.7%, 21.6%, 24.7% in S. anatum; 18.9%, 15.7%, 37.8% in S. typhimurium, while those isolates in 1993 to the same three antibiotics were, respectively, 1.8%, 0.6%, 3.7% in S. enteritidis; 0.8%, 0%, 9.1% in S.derby; 1.8%, 2.7%, 10.8% in S. weltevreden; 3.8%, 0%, 23.0% in S.1, 4, 5, 12:i:-; 2.2%, 2.2%, 6.7% in S. anatum; 4.5%, 1.5%, 10.6% in S. typhimurium. It was shown that the resistance rates in 1994 were significantly higher than those in 1993. All isolates were susceptible to ofloxacin with the exception of one isolate.

Bacterial contamination in the environment of food factories processing ready-to-eat fresh vegetables.

A total of 196 samples were collected from equipment for trimming, washing, slicing, soaking, dehydrating, blending, and packaging and from the floor and air of operation rooms before and after operation in two food factories processing ready-to-eat fresh vegetables located in the suburbs of Tokyo. Heavy contamination determined by an aerobic plate count of >5.0 log CFU/cm2 or ml was observed after operation in most of the samples examined, as were samples taken before operation on the interior surfaces of equipment for washing, slicing, dehydrating, and blending, the surfaces of blades for slicing, and the floor surfaces of operation rooms. From these environmental samples, the coliform group was detected before operation. Although 67 strains of 70 coliforms isolated were nonfecal, three Escherichia coli strains were detected in the surface of the operation room floors and the gloves of employees. Bacillus cereus was isolated from 9 of 86 and 17 of 85 samples examined before and after operation with the number of 2.0 to 3.0 log CFU/cm2 or ml. Listeria spp. were not detected in the environment of the food factories.

Gene Mutations Responsible for Overexpression of AmpC β-Lactamase in Some Clinical Isolates of Enterobacter cloacae

ABSTRACT 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.

Occurrence of Yersiniosis and Listeriosis in wild boars in Japan

From December 1994 to February 1995, 131 wild boars (Sus scrofa leucomysta) living in a mountainous area in Japan were examined for yersiniosis and listeriosis. Of 131 wild boars, 76 (58%) were males and 55 (42%) were females. Four Yersiniaspp. including Y. pseudotuberculosis, Y. enterocolitica, Y. frederiksenii,and Y. aldovei,were isolated from 49 (37%) of 131 wild boars. Yersinia pseudotuberculosiswas isolated from five (4%) of 131 wild boars. All Y. pseudotuberculosisisolates were serotype 4b and harbored virulence plasmids. Yersinia pseudotuberculosiswas isolated only from boars under 2-yr-old. No human pathogenic Y. enterocoliticawas isolated. Listeria monocytogeneswas isolated from two (1%) of the wild boars and both isolates were serotype 4b. These findings indicated that wild boar could be a reservoir of Y. pseudotuberculosisand L. monocytogenesin Japan.

OCCURRENCE OF CAMPYLOBACTER JEJUNI IN FREE-LIVING WILD BIRDS FROM JAPAN

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 (Columba 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.

Effects of orally administered Clostridium butyricum MIYAIRI 588 on mucosal immunity in mice

The activation of local mucosal immunity by Clostridium butyricum MIYAIRI 588 (CBM588) was investigated in germ-free mice. An increase of polyclonal IgA production in the small intestine or secretion into the intestinal lumen was observed in mice mono-associated with CBM588 and fed a diet containing killed vegetative cells of CBM588 (VCBM). However, fecal IgA of anti-CBM588 was rarely formed in mice administered CBM588 during 6 weeks from administration. Cholera toxin was administered orally to SPF mice fed a diet containing CBM588, and IgA secretion of anti-cholera toxin was enhanced in mice fed a VCBM diet. In addition, the production of IgA, IgM and IgG in Peyers patch cell culture was increased in the presence of VCBM. These results suggest that oral administration of CBM588 stimulates polyclonal mucosal immune activity and shows adjuvant activity for anti-cholera toxin.

Pulsed-Field Gel Electrophoresis in Differentiation of Erysipelothrix Species Strains

ABSTRACT We report here the first analysis of Erysipelothrixspp. using pulsed-field gel electrophoresis (PFGE). Seventy strains of Erysipelothrix spp. were analyzed.SmaI, AscI, and NotI were tested for the ability to cleave the DNA extracted from those strains, and among them, SmaI was the most reliable enzyme. Sixty-three distinct PFGE patterns were produced, and no DNA degradation was observed, allowing the identification of all of the strains. Based on these results and on those of a previous analysis using randomly amplified polymorphic DNA and ribotyping, PFGE withSmaI might be considered to be more sensitive than those methods and to be the best method for epidemiological studies of strains of this genus.

A Survey for Yersinia pseudotuberculosis in Migratory Birds in Coastal Japan

Yersinia pseudotuberculosis was isolated from three specimens of two species of birds, the black-faced bunting (Emberiza spodocephala) and pied wagtail (Motacilla alba), of 528 specimens of birds examined from coastal regions in Japan. The two isolated strains of Y. pseudotuberculosis were identified as serovar 4b and serovar 3. This is the first isolation of Y. pseudotuberculosis from birds in Japan. Yersinia enterocolitica was isolated from three specimens of the pied wagtail, one specimen of the reed bunting (Emberiza schoeniclus) and one specimen of the rustic bunting (Emberiza rustica). Yersinia frederiksenii was isolated from two specimens of the gray-rumped sandpiper (Heteroscelus brevipes). Yersinia intermedia was isolated from one specimen of the pied wagtail.

Occurrence of Zoonotic Bacteria in Retail Game Meat in Japan with Special Reference to Erysipelothrix

From December 1993 to March 1994, a total of 93 wild boar and 30 deer meat samples were purchased from 13 retail shops and examined for the presence of species of Erysipelothrix , Yersinia , Listeria , Salmonella and Campylobacter . Erysipelothrix spp. were isolated from 41 wild boar and 15 deer samples. These isolates were identified as 13 serotypes. Serotypes 6 and 2 were the most predominant. Of 17 isolates examined, 14 isolates were highly virulent for mice. The bacteria of the same serotype were isolated repeatedly from the samples purchased in 4 of the shops. Yersinia enterocolitica was isolated from 36 wild boar and 10 deer samples; however, all isolates of Y. enterocolitica did not have pathogenic properties. Listeria monocytogenes was isolated from 5 wild boar samples. The isolates were identified as serotype 1/2c and 4b. Salmonella spp. were isolated from 2 wild boar samples; one isolate was identified as S. typhimurium and the other was untypable. Campylobacter spp. were not detected.