Salmonella | Salmonella in Meat !!
Dot Nepal presents an informative article on “Salmonella”. Most of us have heard from our ancestors who are basically religious that killing is distasteful. Today we present that Salmonella (a type of bacteria found in meat) might affect our health if we do not take precaution.
What is Salmonella
Salmonella is one of the important pathogenic members of family “Enterobacteriaceae” responsible for causing various infections and food poisoning in human and animals. Salmonella species are gram negative rods with size of 2-4×6µm. they are non-acid fast, non capsulated and non spore forming. Most serotypes are motile with peritrichous flagella. These non-motile bacteria are susceptible to cause infection in poultry birds with high mortality rate. Salmonella species are aerogenic, non lactose fermenter, urease negative, indole negative, methyl red positive, Voges-Proskauer negative and citrate variable (Mackie and Mc Cartney 1989).
Several species of Salmonella are pathogenic, some producing mild gastroenteritis, other producing a severe and often fatal food poisoning, which is called Salmonellosis. Salmonella grow between 15-45oC, and at pH range of 4 to 8. with the exception of limited number of human host adapted serotypes (also referred to as the typhoidal Salmonellae), the members of the genus Salmonella are regarded as zoonotic or potentially zoonotic (Acha and Szyfres, 2001).
History of Salmonella
The Salmonella group previously was also called the TPE group, the so called typhus-paratyphus enteritis group. It comprises the typhus bacillus, Salmonella typhi, previously called Eberth- Gaffkey bacillus or Eberthela typhi after the name of two scientists Eberth (1880) observed into the mesenteric lymph node and spleen of typhoid patient, and Gaffkey (1884) isolated the organism (Shrestha K, 2008). In 1896, it was demonstrated that the serum from an animal immunized with the typhoid bacillus agglutinated (clumped) the typhoid bacterial cells, and it was shown that the serum of patients afflicted with typhoid likewise agglutinated the typhoid bacillus. Sero diagnosis of typhoid was thus made possible by 1896 (Shrestha K, 2008).
In general, Salmonella is catalase +ve, oxidase –ve, produce gas from glucose at 37oC. produce acid from carbohydrate breakdown ie sugars like Dulcitol, Arabinose, Maltose, Trehalose, Xylose, etc. with variation in reaction according to different types, use citrate as carbon sources, MR +ve, Vp –ve. Protein reactions shown by are –ve gelatin hydrolysis, -ve indole reaction, -ve urea hydrolyzation, production of H2S from TSI etc. (Joshi V, 2003).
Few biochemical characteristics are different between S. pullorum and S. gallinarum (Christensen et al, 1992). Both of them ferment arabinose, dextrose, galactose, mannitol, mannose, rhamnose and xylose to produce acid with or without gas. S. gallinarum decarboxylates ornithine, whereas S. gallinarum does not (Shiva Prasad, 1997). S. pullorum and S. gallinarum produce a red slant with a yellow butt and shows delayed blackening from H2S production. S. gallinarum does not form gas in triple sugar iron agar, but S. pullorum may show weak gas production (Doughlas et al, 1998).
How do we get affected by Salmonella
Salmonellosis in humans is generally contracted through the consumption of contaminated food of animal origin (mainly meat, poultry, egg & milk), although many other foods, including green vegetables contaminated from manure, have been implicated in its transmission. The causative organisms pass through the food chain from primary production to households or food-service establishments and institutions. In additional to acquiring infection from contaminated food, human cases have also occurred where individuals have had contact with infected animals, including domestic animals such as cats & dogs. Domestic animals probably acquire the infection in the same ways as humans, i.e through consumption of contaminated raw meat, poultry or poultry-derived products. The evolution of specific Salmonella serotypes in intensive animal husbandry and subsequently in humans has been observed over the past three decades. S. enteritidis caused the most recent epidemic, which peaked in humans in 1992 in many European countries. Its current slight decline sets the scene for re-emergence of S. typhimurim as the most important serotype in human Salmonellosis. Another possible scenario is that these two particular strains with epidemic potential will dominated in many countries in the Foreseeable Future (WHO, 2004).
SALMONELLOSIS IN NEPAL
In Nepal, Salmonellosis has caused a burning problem for poultry raiser as well as for consumers. More than 2,200 serovar of Salmonella has been identified so far all over the world and few of them cause disease in poultry e.g. S. pullorum, S. gallinarum, S. enteritidis, S. typhimurium, S. typhi, S. arizone, S. anatis, & S. Virchow, etc and some cause food poisoning in human eg. S.enteritidis, S. typhimurium, S. Virchow etc. Salmonellosis, a zoonotic and egg born disease has great importance as most of the chickens are distributed from recent established hatcheries or brought from neighbouring countries which play significant role in disease transmission in the country. (Prasai 2000).
In a study conducted at CVL and ADCC(central veterinary laboratory and animal disease control section) out of 268 post-mortem chicken samples cultic 259 samples were found to be infected E-coli was made predominant isolates (73.13%), followed by Salmonella spp, Streptococcus spp (7.08%) and S, aureus (2.61%). Among Salmonella spp, S. gallinarum and S. pullorlun were identified, 95.34% of Salmonella spp were sersifise to chleramphenicol while Ampicillin and cloxacillin were found to be least effective drugs (Shrestha k,2008).