Coliform Plate Research Articles

Microbiological quality of bottled water in Saudi Arabia

Abstract The microbiological quality of sixty six bottled water samples representing 14 locally produced and six imported brands in Saudi Arabia have been examined for total coliform and heterotrophic plate count using membrane filtration method. Three local brands of large capacity (10–20 liters) were also used to observe the storage effect for 75 days. No coliform was detected in any of the samples. Very low plate counts (0–1/ml) were found in small bottles (0.5 ‐ 1.5 liters capacity) whereas comparatively high plate counts (3–276/ml) were found in large bottles. It was also observed that storing the large bottles for certain time causes an increase in bacterial count.

Efficacy of Petrifilm™ E. coli Count Plates for E. coli and Coliform Enumeration

The Petrifilm E. coli Count plate (PEC) method was compared to the AOAC MPN method to determine the efficacy of the PEC method to detect E. coli and coliforms in 115 inoculated cheese samples, 94 vegetables samples, and in 100 naturally contaminated poultry samples. The PEC method was compared to two other coliform plate count methods. The 24 h PEC method is as good as or better than the AOAC MPN method for the detection of E. coli. In addition, qualitative results suggest that the PEC method may be more sensitive than the 9 tube MPN method for the detection of very low numbers of E. coli. Comparable coliform results were obtained.

A Survey of Coliforms and Staphylococcus aureus in Cheese Using Impedimetric and Plate Count Methods

A total of 256 cheese samples were analyzed for coliform plate count using violet red bile agar and for an impedance count using BactometerR Coliform Medium with a correlation coefficient between methods of R=−.91. Fifty-four percent of the samples contained 102 to 107 colony forming units/gram (CFU/g). The highest counts were in cream and fresh cheese products. When 27 Cheddar cheese samples were inoculated with from 102 to 107 CFU of Escherichia coli/g a correlation of R=−.97 was found between methods. Two hundred of the cheese samples were analyzed for Staphylococcus aureus using Baird-Parker medium and impedance count using BactometerRS.aureus Medium. Five samples (2%) contained over 103 CFU/g. The strains isolated were coagulase-positive. When 34 samples of cheese were inoculated with 102 to 107 CFU of staphylococci/g, the correlation between the plate and impedance method was R=0.98.

Variation in Food Microbiological Tests Used to Evaluate Analyst Performance

Procedures for evaluating analyst performance in state and federal milk and food laboratory quality assurance programs depend on the estimates of variation for the methods used. The total components of variance for a method consist of replicate error, among-analysts variance, and analyst-sample interaction components. Eleven methods were evaluated in this study. Total variance estimates of milk analytical procedures for the Standard Plate Count, plate loop count, coliform plate count, direct microscopic somatic cell count, electronic somatic cell count and Wisconsin mastitis test were 0.01045, 0.01371, 0.01590, 0.01265, 0.00504 and 4.06, respectively. Estimates of the logarithmic total variance of food analytical procedures for the aerobic plate count, coliform most probable number (MPN), Escherichia coli MPN, fecal coliform MPN and Staphylococcus aureus MPN were 0.00853, 0.10205, 0.14705, 0.14780 and 0.24245, respectively. The study showed that current analyst performance levels used by state and federal laboratory quality assurance programs are satisfactory.

MICROBIAL QUALITY OF FROZEN COMMINUTED TURKEY MEAT

ABSTRACTAn evaluation of the microbial quality of 50 samples of frozen comminuted turkey meat purchased at retail markets revealed the following mean levels of contamination per gram; standard plate count, 9.4 × 107; psychrotrophic plate count, 2.4 × 107; coliform plate and MPN counts, 47 and 110, respectively; Escherichia coli plate and MPN counts, 32 and 93, respectively; Staphylococcus aureus MPN, 6; and fecal streptococci, 180. Sulrnonella sp. were isolated from 38% of samples while Clostridium perfringens was isolated from 20%. Various species of primarily mesophilic aerobic gram‐positive and gram‐negative organisms were isolated and identified. The results of this study indicate that this product carries a dense and diverse microbial load.

Microbial Flora of Preseasoned Comminuted Turkey Meat

Preseasoned comminuted turkey meat, prepared at the retail level, was examined and revealed the following levels of microbial contamination per gram: mean standard plate count 2.2 × 108, mean coliform plate count 2.0 × 105, Escherichia coli count 8.7. Gram-positive and gram-negative microbial flora were isolated and identified.

Microbiology of Fresh Comminuted Turkey Meat

Standard plate counts, coliform plate and most probable number (MPN) counts, Escherichia coli plate and MPN counts, Staphylococcus aureus MPN counts, and fecal streptococcus counts were determined for 75 samples of fresh ground turkey meat purchased from retail markets in the San Francisco Bay Area. The presence of Clostridium perfringens was determined by both direct plate count and enrichment techniques. Salmonellae were isolated using selective enrichment procedures. Samples were screened for presence of enteroviruses. Aerobic gram-positive and gram-negative organisms were isolated and identified. Clostridium perfringens and Salmonella sp. were isolated from 52% and 28% of the samples, respectively. The mean standard plate count was 84,000,000 per gram. The mean count for E. coli determined by the MPN method was 19 per gram. Fecal streptococci were isolated from 95% of the samples with a mean count of 18,000 per gram. Staphylococcus aureus was isolated from 80% of samples analyzed with a mean count of 34 per gram.

TESTING THE PERFORMANCE OF MILK LABORATORIES BY MEANS OF LIQUID SPLIT-SAMPLES

In recent years state laboratory agencies have shown greater interest in the accuracy of results of laboratories performing official quality tests of milk. Visits to laboratories for purposes of evaluation may be supplemented by use of split-samples shipped from the central laboratory twice each year. The details of a method for shipping liquid split-samples are described.Liquid split-samples may be examined by procedures such as standard plate count, coliform plate count and the phosphatase test. A thermal sensitive organism proved to be useful in detecting laboratories using excessive incubation temperatures.

INFLUENCE OF PENICILLIN IN MILK ON TOTAL AND COLIFORM BACTERIA PLATE COUNTS

Storage of milk at 10° C for 72 hours that contained 1.0 unit of penicillin per milliliter of milk resulted in no significant increases in total plate counts while the counts increased considerably in control samples under similar conditions. Although this would indicate a preservative property of penicillin it is recommended that penicillin not be added to market milk for reasons which are discussed. Coliform plate counts were not affected by as much as 10 units of penicillin per milliliter of milk. A decrease in penicillin concentration in milk indicated possible production of a “penicillinase” by the coliform organisms.