Most Probable Number Of Coliforms Research Articles

Validity of Members of the Total Coliform and Fecal Coliform Groups for Indicating the Presence of Salmonella in the Quahaug, Mercenaria mercenaria

To determine the relationship of most probable number (MPN) of the total and fecal coliform groups in shellfish and shellfish-growing waters to the presence of Salmonella in quahaugs (Mercenaria mercenaria), a microbiological survey of 214 samples of the quahaug, or hard-shell clam, was done over 24 months. For purposes of this study, waters were classified as safe for shellfish harvesting by one of two criteria: (a) a total coliform MPN of ≤ 70/100 ml of water or (b) a fecal coliform MPN value of ⩽ 14/100 ml of water. None of the quahaug samples harvested from waters meeting these standards contained Salmonella. Additionally, Salmonella was not detected in any of the quahaug samples meeting the wholesale market quality standard of 230 fecal coliforms per 100 g of shellfish as specified by the National Shellfish Sanitation Program. An increase in the total coliform and fecal coliform MPN of the waters more closely paralleled an increase in the fecal coliform MPN, as compared to the total coliform MPN of the quahaug meats. Five Salmonella serotypes, including Salmonella parathyphi B, were found singly and in combination in five (2.3%) of the quahaug samples in this survey.

Comparative Validity of Members of the Total Coliform and Fecal Coliform Groups for Indicating the Presence of Salmonella in the Eastern Oyster, Crassostrea virginica

During a 24-month survey, 539 samples each of the Eastern oyster, Crassostrea virginica, and the overlying water were collected to determine the relation of most probable number (MPN) of the total and fecal coliform groups in shellfish and water to the presence of Salmonella in the shellfish themselves. Occurrence of Salmonella in the shellfish more closely paralleled a progressive increase in the fecal coliform MPN as compared to the total coliform MPN in the water and shellfish meat. The percentage of Salmonella-positive shellfish samples was somewhat higher in oysters harvested from waters conforming to the present bacteriological approved growing area standard of ≤70 total coliforms per 100 ml water as compared to these same waters meeting a recently proposed fecal coliform standard of ≤14 organisms per 100 ml. In no instance was Salmonella detected in oysters from growing areas officially approved for harvesting on the basis of both a bacteriological and sanitary survey. Of a variety of enrichment broths and plating media used for recovery of Salmonella from oysters, direct enrichment in tetrathionate broth with added brilliant green followed by streaking on bismuth sulfite agar was the most productive combination of media for recovering a large variety of Salmonella serotypes.

Bacteriological Quality of Delicatessen Foods: Are Standards Needed?

Surveillance of seven types of delicatessen salads (chicken, egg, ham, macaroni, American potato, shrimp, and tuna) was conducted from March through July, 1974. Liver spread and sandwich spread were included in the sampling. Products were obtained from approximately 150 retail establishments. A separate surveillance of one central production unit and approximately 18 retail establishments, which it supplied, was also conducted. Twenty six percent to 85% of samples of products obtained from general retail outlets had aerobic plate count (APC) values of less than 100,000 per gram. Thirty six percent to 79% had coliform Most Probable Number (MPN) levels of less than 100 per gram, while 83 to 100% contained less than 10 Escherichia coli per gram. Some samples of each of the products contained low numbers of coagulase-positive staphylococci. Seventy one per cent to 96% of samples of various products, obtained from a central production unit, yielded APC values of less than 100,000 per gram. Forty five percent to 94% had coliform MPN values of less than 100 per gram. Two of six products contained low levels of coagulase-positive staphylococci in 9% and 2% of the samples examined.

Microbiological Methods for Examination of Frozen and/or Prepared Foods

Abstract A method for the microbiological examination of frozen and/or prepared foods as an index to the sanitary conditions under which the food was produced and/or stored was subjected to collaborative study. The method encompasses four determinations: aerobic plate count, the MPN (most probable number) of coliforms, the MPN of E. coli, and the numbers of S. aureus. Subdivisions of custard pie filling, some inoculated with E. coli, A. aerogenes, or S. aureus, were examined by four laboratories. Statistical evaluation of the results indicated that the method gives essentially equivalent results from laboratory to laboratory. It is recommended that the method be adopted as official, first action.