Swine as a potential reservoir of Shiga toxin-producing Escherichia coli 0157:H7 in Japan.To the Editor: Shiga toxin-producing Escherichia coli (STEC STEC
shiga toxin-producing Escherichia coli. ) O157:H7 has become a major meat safety issue worldwide. Cattle, an important reservoir of human infection (1), may not be the only source of this organism (2,3). In a survey of pigs in England (4), non-STEC O157 was isolated from four (0.4%) fecal samples collected (after slaughter) from 1,000 pigs. We found that, although an unlikely source of infection for humans, pigs are a potential reservoir of STEC O157:H7 in Japan.
In 1997, there were 14,400 pig farms and 9,823,000 pigs (average 682 per farm) in Japan. Thirty-five (0.24%) of these farms were randomly selected for study, and rectal swabs were taken from 221 healthy pigs during May and June 1997. The average number of animals examined on each farm was 6.3.
Fecal samples were dipped into test tubes containing Cary-Blair transport medium (Nissui, Japan) and kept refrigerated until processing (usually within 48 hours). Swabs were then incubated overnight at 42 [degrees] C in 10 ml of mEC broth (Kyokuto, Japan) containing 20 [micro]g/ml of novobiocin no·vo·bi·o·cin
An antibiotic produced by the actinomycete Streptomyces nivens and used to treat infections by gram-positive bacteria. (Sigma, USA), after which one loop of the broth was spread onto MacConkey sorbitol sorbitol /sor·bi·tol/ (sor´bi-tol) a six-carbon sugar alcohol from a variety of fruits, found in lens deposits in diabetes mellitus. agar medium (Difco, USA). After overnight incubation at 37 [degrees] C, sorbitol-negative colonies from the agar plates were tested by slide agglutination agglutination, in biochemistry
agglutination, in biochemistry: see immunity.
agglutination, in linguistics
agglutination, in linguistics: see inflection. with E. coli O157-1atex test (Oxoid, UK). Strains that agglutinated were confirmed as E. coli by using the API 20E system (BioMerieux, France). Strains confirmed as E. coli O157 were subcultured in a motility motility /mo·til·i·ty/ (mo-til´ite) the ability to move spontaneously.mo´tile
Motility is spontaneous movement. medium for 3 to 4 days to enhance development of flagella flagella /fla·gel·la/ (flah-jel´ah) [L.] plural of flagellum.
(fl , then they were tested by tube agglutination with E. coli H7 antiserum antiserum /an·ti·se·rum/ (an´ti-se?rum) a serum containing antibody(ies), obtained from an animal immunized either by injection of antigen or by infection with microorganisms containing antigen. (Denkaseiken, Japan). The swine E. coli O157:H7 isolates were examined by polymerase chain reaction polymerase chain reaction (pŏl`ĭmərās') (PCR), laboratory process in which a particular DNA segment from a mixture of DNA chains is rapidly replicated, producing a large, readily analyzed sample of a piece of DNA; the process is for the presence of Shiga-toxin genes stx1 and stx2 and to elucidate intimin (eaeA) DNA sequences (5), for a plasmid of 92 kb (pO157) by agarose gel electrophoresis Agarose gel electrophoresis is a method used in biochemistry and molecular biology to separate DNA, RNA, or protein molecules by size. This is achieved by moving negatively charged nucleic acid molecules through an agarose matrix with an electric field (electrophoresis). (6), and for phage phage: see bacteriophage.
phage - A program that modifies other programs or databases in unauthorised ways; especially one that propagates a virus or Trojan horse. See also worm, mockingbird. The analogy, of course, is with phage viruses in biology. type by the previously described method (7).
Although the numbers sampled were too small to allow comparisons between farms, samples from three (1.4%) apparently healthy pigs (ages: 2, 6, and 9 months) from three farms (8.6%) were positive for STEC O157:H7. The three strains from the pigs were biochemically typical of STEC O157:H7 that did not ferment sorbitol and lacked [Beta]-glucuronidase; agglutinated with E. coli O157-latex and with H7 antiserum; possessed stx1, stx2, and eaeA genes; and harbored pO157 plasmid characteristic of STEC O157:H7. The strains belonged to phage type 21, 37, or 43.
The 1.4% carriage rate of STEC O157:H7 in pigs in this investigation is almost the same as that in cattle in Japan (8), which suggests that STEC O157:H7 strains are probably widespread in Japanese pig populations. The STEC 0157-positive pigs were each housed in a concrete-floored pen and kept separate from cattle. Whether these pig isolates are the same as cattle or human isolates needs to be clarified; however, they had the same biochemical and genetic markers as STEC O157:H7 isolated from cattle and humans (6,9). The phage type 21 that we found among pig isolates was also observed in bovine and human STEC O157:H7 isolates in Japan (17). These results suggest that common vehicles for dissemination of the organism may exist.
So far, pork has not been identified as a source of human STEC O157:H7 illness in industrialized in·dus·tri·al·ize
v. in·dus·tri·al·ized, in·dus·tri·al·iz·ing, in·dus·tri·al·iz·es
1. To develop industry in (a country or society, for example).
2. countries, but our results indicate that eating pork, contact with pigs, and contamination with pig feces should be considered potential sources of this pathogen. This is the first isolation of naturally occurring STEC O157:H7 in pigs in Japan.
This work was supported by a grant from the Ministry of Agriculture, Forestry, and Fisheries of Japan.
Muneo Nakazawa, Masato Akiba, Toshiya Sameshima
National Institute of Animal Health, Tsukuba, Ibaraki, Japan
(1.) Wells JG, Shipman LD, Greene KD, Sowers EG, Green JH, Cameron DN, et al. Isolation of Escherichia coli serotype serotype /se·ro·type/ (ser´o-tip) the type of a microorganism determined by its constituent antigens; a taxonomic subdivision based thereon.
v. O157:H7 and other shiga-like-toxin-producing E. coli from dairy cattle. J Clin Microbiol 1991;29:985-9.
(2.) Chapman PA, Siddons CA, Harkin MA. Sheep as a potential source of verocytotoxin-producing Escherichia coli O157. Vet Rec 1996;138:23-4.
(3.) Chalmers RM, Salmon RL, Willshaw GA, Cheasty T, Looker N, Davies I, et al. Vero-cytotoxin-producing Escherichia coli O157 in a farmer handling horses. Lancet 1997;349:1816.
(4.) Chapman PA, Siddons CA, Cerdan Malo AT, Harkin MA. A 1-year study of Escherichia coli O157 in cattle, sheep, pigs and poultry. Epidemiol Infect 1997; 119:245-50.
(5.) Sueyoshi M, Fukui H, Tanaka S, Nakazawa M, Ito K. A new adherent adherent /ad·her·ent/ (-ent) sticking or holding fast, or having such qualities. form of an attaching and effacing Escherichia coli (eaeA+,bfp-) to the intestinal epithelial cells of chicks. J Vet Med Sci 1996;58:1145-7.
(6.) Chapman PA, Siddons CA, Wright DJ, Norman P, Fox J, Crick Crick , Francis Henry Compton 1916-2004.
British biologist who with James D. Watson proposed a spiral model, the double helix, for the molecular structure of DNA. He shared a 1962 Nobel Prize for advances in the study of genetics. E. Cattle as a possible source of verocytotoxin-producing Escherichia coli O157 infections in man. Epidemiol Infect 1993; 111:439-47.
(7.) Akiba M, Masuda T, Sameshima T, Katsuda K, Nakazawa M. Molecular typing of Escherichia coli O157:H7(H-) isolates from cattle in Japan. Epidemiol Infect 1999;122:337-41.
(8.) Sekiya J. Escherichia coli O157:H7 in livestock in Japan. Revue Scientifique et Technique Office International des Epizooties 1997;16:391-4.
(9.) Ratnam S. March SB, Ahmed R, Bezanson GS, Kasatiya S. Characterization of Escherichia coli serotype O157:H7. J Clin Microbiol 1988;26:2006-12.
Munro Nakazawa, Masato Akiba, Toshiya Sameshima
National Institute of Animal Health, Tsukuba, Ibaraki, Japan