Coliform Plate Count Research Articles

The microbial content of unexpired pasteurized milk from selected supermarkets in a developing country

Objective To determine the presence and levels of microbes in unexpired pasteurized milk from randomly selected supermarkets in Kingston, Jamaica. Methods The quantitative study used a stratified random sampling technique in the selection of the 20 representative milk samples from six (6) supermarkets. Microbiological tests such as methylene blue reduction, standard plate count (SPC), coliform plate count (CPC), purity plate culture, gram staining and biochemical tests were performed to examine the microbes in purchased unexpired pasteurized milk. Results One sample (BCr016) had a pH of 4.0, a rancid odour and curdled appearance. It decolourized within one hour during the methylene blue reduction test and was classified as class 4 milk. Seven of the samples were sterile with no microbe growth on the plate count agar and violet red bile salt agar (VRBA). The milk samples that appeared to be safe for consumption were all 10, 11, 12 and 13 days before expiration. The VRBA sample BCr016, had a colony count of 13 400 CFU/mL. There was the presence of Escherichia coli in sample LCr021 which had a standard plate count of 1 580 SPC/mL and a coliform count of 500 CFU/mL. Enterobacter sp. was present in colonies from BCr016 and all the other milk samples. Conclusions Unacceptable levels of Enterobacter spp. and Escherichia coli were found in most of the samples. Effective measures to ensure safe milk for human consumption such as the phosphatase test and methylene blue reduction test should be routinely performed on each batch of milk processed by dairy plants.

Microbial quality and associated health risks of raw milk marketed in the Tanga region of Tanzania

Objective To evaluate microbial quality and associated health risks of raw milk marketed in the Tanga region of Tanzania. Methods A microbial quality assessment of marketed raw milk was undertaken by evaluating 59 samples of milk from selling points (collecting centres =15), bicycle boys (12) and kiosks/restaurants (32) in Tanga city during April-May 2005. Quality and milk-borne hazards were assessed using a combination of tests in order to quantify the occurrence of Brucellosis (milk ring test), Escherichia coli ( E. coli) O157:H7 (culture), the coliform bacteria as well as standard plate count (SPC). Specific gravity (SG) determination was used as an indicator of adulteration. Results The mean coliform plate count (c.f.u/mL) of milk handled by bicycle boys (4.2 × 10 6) was significantly higher than that handled by collecting centres (3.0 × 10 6) and kiosk/restaurants (1.4 × 10 6), respectively ( P < 0.05). Of the 59 milk samples collected, 33 (56%) were Brucella milk ring test (MRT)-positive and 78% and 17% of the samples graded satisfactorily based on SG and coliform plate counts as prescribed by East African Community standards for raw milk. There was no verocytotoxigenic E. coli (VTEC) O157: H7 in any of the milk samples collected and analysed during the present study. Conclusions It can be concluded that raw market milk in the study area is of poor bacteriological quality and hazardous for human consumption. This highlights the need to implement good hygiene practices and effective monitoring from production through the delivery chain to the consumer. Further studies are needed for detection of toxins that are produced by E. coli, other pathogenic spore forming bacteria ( Bacillus spp. and Clostridium spp.) and other harmful microorganisms.

Factors associated with coliform count in unpasteurized bulk milk

The objective of this study was to identify factors associated with bulk milk coliform count (CC). Dairy farms (n=10) were visited once weekly on sequential weekdays over a period of 10 wk. During each visit, in-line drip samplers were used to collect 1 milk sample from 2 points of the milk line (between the receiver jar and milk filters, and after the plate cooler). During the same period that in-line milk samples were collected, university personnel observed milking performance and hygiene and collected liner (n=40) and teat skin swabs (n=40). Coliform counts were determined for milk samples and swabs using Petrifilm CC plates (3M, St. Paul, MN). A mixed model was used to assess the association between in-line milk CC (ILCC) and several potential predictor variables. The mean duration of each visit was 73min and the time between start of milking and beginning of milk sampling was 154min. The mean number of cows milked during each visit was 236. For all milk samples (n=181), geometric mean ILCC was 37cfu/mL. In-line milk CC varied by farm, ranging from 5 to 1,198cfu/mL. Rate of fall-offs, rate of cluster washes, outdoor and indoor temperature, indoor humidity, sampling duration, and parity group were unconditionally associated with ILCC but did not enter the final multivariate model. In-line milk CC was 4 times greater (115cfu/mL) when milking machine wash failures occurred compared with ILCC after normal washes (26cfu/mL). Pre-filter and post-cooler ILCC were not different when milk samples were collected at the beginning (<33% of herd milked) or at mid-milking (33 to 66% of the herd milked), whereas pre-filter ILCC was less than post-cooler for samples collected at the end of milking (>67% of the herd milked). Geometric mean ILCC (cfu/mL) increased 6.3% for every 10% increase in in-line milk SCC (cells/mL). Geometric mean ILCC increased 2.3% for every 10% increase in liner CC (cfu/mL). Results of this study provide novel information about farm factors associated with CC, as estimated in milk before storage in tankers or bulk tanks, and highlight the importance of proper and consistent milking machine washes in minimizing bulk milk coliform contamination. The nature of the associations between liner CC, rate of cluster washes, rate of milking units fall-offs, and ILCC indicates that managing and monitoring such events has the potential for improving bacteriological quality of farm bulk milk.

Effects of time of meat purchase on the level of microbial contamination of beef from retail points in Samaru market, Zaria-Nigeria.

The meat retail selling points are the major places where people usually purchase meat from morning through to evening at retail points in Samaru, Zaria. A total of 100 meat samples were collected from five different retail meat selling points in Samaru market Zaria, Kaduna state. Twenty samples were obtained from each retail point (10 samples in the morning and 10 in the evening). The meat samples were tested for total aerobic and coliform plate counts to determine the effect of time on the level of microbial contamination. The result of the study shows that there was a statistically significant difference (P

Microbial Quality and Safety of Fresh-cut Broccoli with Different Sanitizers and Contact Times

This study was conducted to investigate the effect of different sanitizers and contact times on storage quality and microbial growth in fresh-cut broccoli. Fresh broccoli samples were cut into small pieces, washed each for 90 seconds and 180 seconds in normal tap water (TW), 100 microl/l chlorinated water (CL, pH 7), electrolyzed water (EW, pH 7.2) containing 100 microl/l free chlorine or 2 microl/l ozonated water (O(3)) separately and respectively. Then, samples were packaged in 30 microm polyethylene bags and stored at 5 degrees Celsius for 9 days. No significant differences were observed in gas composition and color parameters (L*, a*, b* and hue angle) among different sanitizers with contact times. No off-odor was detected during the storage. Longer contact time was not effective in reducing microbial population except O(3) washing. O(3) with 90 seconds was not much effective in reducing microbial population compared to Cl or EW. However, samples washed with O(3) for 180 seconds observed the lowest numbers of total aerobic and coliform plate counts. The result suggested that, longer contact time of ozone can be used as a potential sanitizer to maintain the microbial quality and safety of fresh-cut broccoli.

단감분말을 함유한 저지방 돈육 미트패티의 냉동 저장 중 품질 변화

열풍건조 단감분말과 동결건조 단감분말을 각각 0%, 3%, 6%을 첨가하여 미트 패티를 제조한 후 <TEX>$-18^{\circ}C$</TEX>에 40일간 저장하면서 품질특성을 평가하였다. 저장기간이 경과함에 따라 모든 제품의 pH는 30일까지 유의적으로 낮았으나(p<0.05) 40일차에는 약간 증가하였다. 보수력은 대조구와 처리구 간에 유의적인 차이가 없었다(p>0.05). 가열감량은 저장기간이 경과함에 따라 유의적으로 증가하였으며(p<0.05), 단감분말이 첨가된 처리구들이 대조구보다 유의적으로 낮았다(p<0.05). 육색 측정결과, 저장기간이 경과함에 따라 명도(L), 적색도(a), 황색도(b) 모두 유의적으로 낮아졌다(p<0.05). 처리구와 비교 시 대조구의 명도가 유의적으로 높았고(p<0.05), 적색도와 황색도는 처리구들이 다소 높은 값을 보였다. 직경감소율은 저장기간이 길어질수록 증가하였다(p<0.05). 미생물 분석결과 저장 40일차까지 총균수는 4.20 log CFU/g를 유지하여 양호하였으나, T3 및 T4는 대조구보다 총균수와 대장균수가 높게 나타났다(p<0.05). VBN 분석결과 T4가 저장 15일차부터 40일까지 다른 제품들에 비해 유의적으로 높았고(p<0.05), TBARS는 대조구에 비해 처리구들이 모두 유의적으로 높게 나타났다(p<0.05). 관능평가에서 전체적인 기호도는 처리구가 대조구에 비해서 다소 높게 평가받았다. 이상의 결과로서 다양한 생리활성물질을 가지는 열풍 또는 동결건조 단감분말은 기능성 식품의 소재로서 미트패티류 제품에 적용할 수 있음을 확인하였다. Pork patties were made containing hot air dried sweet persimmon powder (T1: 3%, T2: 6%) and freezer dried sweet persimmon powder (T3: 3%, T4: 6%). The control (C: no addition) and each treatment were stored for 40 days at <TEX>$-18^{\circ}C$</TEX>. The pH value decreased (p<0.05) in all products over 30 days of storage but slightly increased thereafter. There was no significant difference in WHC between the control and treatment groups. Cooking loss and meat color (CIE L, a, b) increased significantly (p<0.05) as storage increased. The cooking loss of meat patties containing sweet persimmon powder were significantly (p<0.05) higher than the control. The L value of the control increased significantly (p<0.05) relative to the treatment groups, however the a and b values were slightly higher in meat patties containing sweet persimmon powder. In all products, the reduction ratio of diameter increased (p<0.05) with storage time. With regard to microorganisms, all samples were in good condition, containing below 4.20 log CFU/g based on total plate counts through 40 days, though total plate counts and coliform plate counts of the control were lower (p<0.05) than T3 and T4. The VBN values of T4 was significantly higher than those of other products at 15, 30, and 40 days of storage. The TBARS values of meat patties containing sweet persimmon powder were significantly (p<0.05) higher than those of the conlIol. Sensory panels determined that meat patties containing sweet persimmon powder had a higher (p>0.05) preference score for overall acceptability.

Risk Factors in the Hygienic Quality of Milk in Ghana

The study was carried out to identify risk factors associated with bacterial contamination of locally produced raw milk and its adulteration with water. A total of 419 respondents of different categories of milk agents in the study sites were sampled for data and milk collection in the dry and wet seasons. The data collected focused on milk marketing factors and handling practices likely to affect milk quality, while the milk samples were analysed to determine the extent of bacterial contamination and adulteration with water. The proportion of milk samples adulterated was 18%. While 23.5% of the milk samples had unacceptably high total plate count (>6.3 log10 cfu/ml), all the samples had unacceptably high coliform plate count (>0.7 log10 cfu/ml). Risk factors associated with high bacterial counts were related to milk mar- keting channels (p<0.05), milk market agents (p<0.01), and milk containers (p=0.06) as well as their mode of cleaning (p=0.06). The only risk factor identified for adulteration of milk was related to season (p=0.04). associated with poor hygienic quality. The findings would help in the formulation of appropriate recommendations to improve the hygienic quality of informally marketed milk in Ghana, which could go along way to stimulate growth of the dairy industry.

Comparison of 3M Petrifilm Staph Express Count Plates, and 3M Petrifilm Rapid Coliform Count Plates with Standard Bacteriology of Bovine Milk

Isolation and identification of mastitis pathogens is a fundamental step in milk quality control programs. There is a need for an inexpensive and rapid bacteriologic test that allows veterinarians as well as dairy producers to make real-time decisions to better manage udder health in their herds. Petrifilm plates may fill this gap. Petrifilm plates are ready-to-use culture media that are used primarily in the food industry. The objectives were 1) Evaluate the test characteristics of the Petrifilm Staph express Count Plates (STX) for identification of S. aureus from milk. Milk samples were taken from cows a) in the first 30 days in milk, b) with high somatic cell count (SCC) during lactation, c) with clinical mastitis. 2) Evaluate the test characteristics of the Petrifilm Rapid Coliform Count Plates (RCC) for identification of coliforms from cases of clinical mastitis.

Evaluation of the Petrifilm™ Culture System for the Identification of Mastitis Bacteria as Compared to Standard Bacteriological Methods

The largest cost associated with treating clinical mastitis during lactation is the discarded milk during and after therapy. To justify this cost, one should ensure that the present infection will respond to antibiotic therapy. Most intramammary antibiotics target gram-positive cocci organisms, and are not particularly effective against Mycoplasma spp, yeasts and mild infections caused by gram-negative pathogens. Similarly, research has demonstrated that other organisms, such as Streptococcus uberis, are highly responsive to intramammary antibiotics, or that the cure rates achieved by various intramammary treatments are not significantly better than no treatment. Thus, there has been an increasing demand for research towards the development of on-farm mastitis culturing media for early identification and accurate classification of bacterial species. Petrifilm™ plates are selective culture media products, which are used for rapid bacteriological isolation and enumeration from food products. The 3M Petrifilm™ products are small, playing card size, sample-ready plates that will allow users to easily and efficiently perform on-site microbial identification. Petriflim™ plates that are potentially useful for mastitis diagnoses are the Aerobic Count Plates, Coliform Count Plates, and Staph Express Count Plates, due to their ease of use, and the ability to reach a diagnosis in as little as 24 hours. The usefulness of the Petrifilm™ culture system for the diagnosis of mastitis has been previously reported.1 The objective of the current project was to determine the test characteristics of Petrifilm™ to characterize the causative organism in producer-defined cases of clinical mastitis.

Cleaning frequency and the microbial load in ice-cream

This study investigates the efficacy of a 62 h cleaning frequency in the manufacturing of ice-cream. Various product and product contact surfaces were sampled progressively throughout the time period between cleaning cycles, and analyzed for microbial growth. The coliform and standard plate counts (SPC) of these samples did not vary significantly over time after 0, 24, 48, or 62 h from Cleaning in Place (CiP). Data for product contact surfaces were significant for the SPC representing sample locations. Some of the variables in cleaning practices had significant influence on microbial loads. An increase in the number of flavors manufactured caused a decrease in SPC within the 24 h interval, but by the 48 h interval the SPC increased. More washouts within the first 24 h interval were favorable, as indicated by decreased SPC. The more frequently the liquifier was sanitized within the 62 h interval, the lower the SPC. This study indicates that food safety was not compromised and safety practices were effectively implemented throughout the process.

Dry Rehydratable Film Method for Rapid Enumeration of Coliforms in Foods (3M™ Petrifilm™ Rapid Coliform Count Plate): Collaborative Study

A rehydratable dry-film plating method for coliforms in foods, the 3M Petrifilm Rapid Coliform Count plate method, was compared with the U.S. Food and Drug Administration's Bacteriological Analytical Manual method for nondairy foods and the American Public Health Association's Standard Methods for the Examination of Dairy Products (SMEDP) method for dairy foods. Six food types, vanilla ice cream, cheddar cheese, fresh refrigerated uncooked pasta, wheat flour, prepared frozen macaroni and cheese, and frozen hash browns, were analyzed for coliforms by 11 collaborating laboratories. For each food product tested, the collaborators received 8 blind samples consisting of a control sample and 3 levels of inoculated sample, each in duplicate. The mean log counts for the methods were comparable. The repeatability and reproducibility variances of the Petrifilm Rapid Coliform Count method at 14 and 24 h were not significantly different from those of the standard methods.

Microbial and color quality of fillets obtained from steam-pasteurized deheaded and eviscerated whole catfish

The present study reports on the microbiological quality and surface color of skinless catfish fillets obtained from steam-treated catfish. Total aerobic (APC), psychrotrophic (PPC), coliform (CPC) plate counts, and Hunter color analysis of fillets were performed after treatment and during 14 days of storage at 4°C. Results indicated that as steam treatment duration increased (15–120 s), greater reduction of fillet microflora population was achieved. Microbial counts on fillets obtained from steam-treated catfish were lower than controls at all sample times. Steam treatment for 120 s produced fillets with APC, PPC, and CPC that were 1·6, 1·7, and 1·9 log10cfu g−1lower than control fillets after 4 days at 4°C. Hunter color analysis of fillets revealed no color differences (L, a, b, and Whiteness) between steam-treated and control fillets. The reduction of skin microbial loads by steam prior to skinning of catfish resulted in fillets with superior microbiological quality and no Hunter surface color changes.

Steam treatment reduces the skin microflora population on deheaded and eviscerated whole catfish

This study tested the efficacy of steam exposures for 0, 30, 60, 90 and 120 s on reducing skin microflora of whole deheaded and eviscerated catfish. Microbiological analyses of skin were performed after treatment and on days 2, 4, 6, 8, 10 and 14 days of storage at 4°C. Catfish skin samples were examined for total (APC), coliform (CPC), and psychrotrophic (PPC) plate counts. Results indicated that as steam treatment duration increased greater reduction of catfish skin microflora was achieved. Mean bacterial counts determined on steam-treated catfish skins were significantly (P<0·05) lower than controls at all sample times. Steam treatment for 120 s was the most effective treatment modality, with APC, PPC and CPC lower than control by 2·3, 3·5 and 3·4 log cfu cm−2after 4 days of storage at 4°C. Skin APC and CPC were reduced below the limit of detection (1·8 log cfu cm−2) following a 30-s exposure, and remained at this level until day 4 of storage at 4°C. Skin PPC were reduced by 2 log cfu cm−2following 120-s steam exposure. Steam application to whole deheaded eviscerated catfish may prove useful to sanitize catfish skin prior to further processing into valuable consumer products.

Thermal inactivation of Escherichia coli O157:H7, Salmonella senftenberg, and Enzymes with Potential as Time-Temperature Indicators in Ground Turkey Thigh Meat

The USDA Food Safety and Inspection Service has proposed to amend cooking regulations to require that any thermal process used for poultry products be sufficient to cause a 7 D reduction in salmonellae. Several enzymes have been suggested as potential indicators of heat processing in poultry, yet no relationship between the inactivation rates of these enzymes and salmonellae has been determined. The thermal inactivation kinetics of endogenous muscle proteins, Escherichia coli O157:H7 and Salmonella senftenberg were compared in ground turkey thigh meat in thermal death time studies. Bacteria counts were determined and muscle extracts were assayed for residual enzyme activity or protein concentration. D and z values were calculated using regression analysis. S. senftenberg had higher D values at all temperatures and was more heat resistant than E. coli. The z values of E. coli on Petrifilm Coliform Count plates and phenol red sorbitol agar plates were 6.0 and 5.7°C, respectively. The z values of S. senftenberg were 5.6 and 5.4°C on Petrifilm and agar, respectively. Lactate dehydrogenase (LDH) was the most heat stable protein at 64°C. LDH, glyceraldehyde-3-phosphate dehydrogenase, creatine kinase, triose phosphate isomerase (TPI), acid phosphatase, serum albumin, and immunoglobulin G had z values of 3.8, 4.3, 4.8, 5.8, 6.3, 6.7, and 8.6°C, respectively, in turkey containing 4.3% fat. The z values for TPI decreased to 5.4°C in thigh meat containing 9.8% fat. Temperature dependence of TPI was most similar to that of S. senftenberg, suggesting it might function as an endogenous time-temperature integrator to monitor adequacy of processing when a performance standard based on this pathogen is implemented.

Comparison of Methods for Determining Coliform and Escherichia coli Levels in Apple Cider

The main objective of this research was to determine the easiest and most reliable media for enumerating coliform bacteria and Escherichia coli levels in apple cider. During the autumn of 1994 a total of 59 apple cider samples were collected directly from 12 cider producers and were assessed for bacterial levels and pH. Plate count agar was used to determine heterotrophic bacteria levels. Coliform levels were determined using three different media: violet red bile agar (VRBA), Petrifilm High Sensitivity Coliform Count Plates (PHSCCP), and Trypticase soy agar with a VRBA overlay (TSA/VRBA) for attempted recovery of coliforms injured by the low pH of the apple cider. Eosin methylene blue agar (EMBA) and Petrifilm E. coli Count Plates were used to screen cider samples for E. coli. Apple cider had an average pH of 3.34 ± 0.08. Heterotrophic bacterial levels ranged from 2.30 to 7.11 log CFU/ml. All cider samples contained coliform bacteria with levels varying greatly; on the different media, we found the following: on VRBA, <1.00 to 4.37 log CFU/ml; on TSA/VRBA, 1.20 to 4.40 log CFU/ml; and on PHSCCP, < 1.00 to 4.56 log CFU/ml. Coliform levels were most easily determined in apple cider by using PHSCCP. However TSA/VRBA proved to be more reliable; coliform detection was significantly (P < 0.05) increased. EMBA was ineffective for screening apple cider for E. coli, with the low pH of the cider producing many false-positive results. E. coli was only recovered by using Petrifilm E. coli Count Plates with one of the 59 samples positive for E. coli (non-O157:H7) at a level of 10 CFU/ml.

High-Sensitivity Dry Rehydratable Film Method for Enumeration of Coliforms in Dairy Products: Collaborative Study

A dry-film coliform count plate that is inoculated with 5 mL sample was compared with the Violet Red Bile Agar plate method in a collaborative study by 18 laboratories. Products analyzed were 2% milk, chocolate milk, cream, vanilla ice cream, cottage cheese, and cheese. Collaborators tested blind duplicate uninoculated samples and samples inoculated at low, medium, and high level. Significantly (P < 0.05) higher numbers of coliforms were recovered by the dry-film method from 2% milk samples at the 3 inoculum levels, the chocolate milk at the low- and high-inoculum levels, and the cream at the high-inoculum level. Significantly higher counts were obtained by the agar method for cottage cheese samples at the low-inoculum level. The repeatability standard deviation for the dry-film method was significantly higher for the high-inoculum level chocolate milk sample and the medium-inoculum level cottage cheese. The same statistic was significantly higher for the agar method at all 3 inoculum levels in the 2% milk and the medium-inoculum level cream. The high-sensitivity dry rehydratable film method for enumeration of coliforms in dairy products has been adopted first action by AOAC INTERNATIONAL.

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.

Dry Rehydratable Films for Enumeration of Coliforms and Aerobic Bacteria in Dairy Products: Collaborative Study

A collaborative study was conducted to compare proposed dry-film plating methods, using aerobic count plates and coliform count plates, to standard agar plating methods for quantifying aerobic bacteria and coliforms in dairy products. In this study, 5 food products (chocolate milk, pasteurized cheese, nonfat dry milk, evaporated milk, and vanilla ice cream), selected as representative dairy products, were analyzed by 11 collaborating laboratories. The results indicate that the dry-film plating methods are equivalent to or better than the agar plating methods. The aerobic count and coliform count dry-film plating methods have been adopted official first action.

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.