Prevalence of Staphylococcus aureus in Raw and Pasteurized Milk Used for Commercial Manufacturing of Brazilian Minas Cheese

1981 ◽  
Vol 44 (3) ◽  
pp. 172-176 ◽  
Author(s):  
EDSON CLEMENTE dos SANTOS ◽  
CONSTANTIN GENIGEORGIS ◽  
THOMAS B. FARVER
Keyword(s):  
Agar Plate ◽  
Raw Milk ◽  
Plate Count ◽  
Pasteurized Milk ◽  
Milk Samples ◽  
Plate Count Agar ◽  
Three Samples ◽  
Dairy Plant ◽  
Cap Method ◽  
Ml Detection

Raw and pasteurized milks used for cheesemaking were surveyed in a dairy plant, Juiz de Fora, MG, Brazil from 1978 to 1979. Raw milk samples were collected from 78 of 127 milk producers supplying 12,000–15,000 liters of milk daily to the plant. The TPC ranged from (log10) 4 CFU/ml to 7.17 CFU/ml with a (log10) mean of 5.59 CFU/ml. S. aureus cells were present in 46.9% of the samples. Mean number of S. aureus was (log10) 4.69 ± 0.54 CFU/ml; the highest number was (log10) 5.99 CFU/ml. Counts based on isolation on TPEY medium and confirmation on coagulase agar plate (CAP) did not differ significantly (P >0.05) from counts based on isolation on Plate Count Agar/DNA agar and confirmation of nuclease-positive colonies on CAP. Fifty bulk pasteurized milk samples were collected from five milk collection systems. TPC had a mean (log10) of 4.02 ± 0.62 CFU/ml with the highest count being (log10) 5.6 CFU/ml. The pH of the milk ranged from 6.55 to 6.89. Type of collection system did not affect the pH of the milk or the TPC (P >0.05). Three samples contained S. aureus at levels of (log10) 3, 2.3 and 4.43 CFU/ml. Detection of S. aureus was based on methods used for raw milk plus use of Baird-Parker/CAP method.

COMPARISON OF PLATE LOOP AND AGAR PLATE METHODS FOR BACTERIOLOGICAL EXAMINATION OF MANUFACTURING GRADE RAW MILK1,2

1967 ◽  
Vol 30 (4) ◽  
pp. 112-115 ◽  
Author(s):  
Sita Ramayya Tatini ◽  
Roger Dabbah ◽  
J. C. Olson
Keyword(s):  
Agar Plate ◽  
Bacterial Count ◽  
Raw Milk ◽  
Substantial Improvement ◽  
Plate Count ◽  
Bacteriological Examination ◽  
Standard Plate Count ◽  
Milk Samples ◽  
Standard Plate ◽  
Bulk Tank

Summary Plate loop counts and standard plate counts on each of several manufacturing grade raw milk samples (handled in cans or in farm bulk tanks) have been compared. On the average, the plate loop count (PLC) was lower than the standard plate count (SPC) regardless of the type of handling of milk on the farm, can or bulk tank. Agreement between the SPC and PLC seemed to depend upon the bacterial-count levels present in milk. Statistical analyses indicated significant differences, at 1% level of probability, between the average bacterial count by SPC and PLC methods regardless of count level (≤100,000/ml or >100,000/ml) in case of can milk samples. On the other hand, in case of farm bulk tank milk samples, no significant differences, at the 1% level of probability, between the average bacterial count by SPC and PLC methods were obtained, when the counts were equal to or less than 100,000 per ml; when the counts exceeded 100,000 per ml, significant differences were present. Since the bacterial counts of manufacturing grade raw milk samples are likely to exceed 100,000/ml, the data presented in this investigation indicate that, until the bacteriological quality of manufacturing grade milk supplies undergoes substantial improvement, the PLC method does not appear to be a suitable substitute for the SPC method for routine bacteriological examination of such milk supplies.

Temperature Equilibration Times of Plate Count Agar and a Comparison of 50 Versus 45 C for Recovery of Raw-Milk Bacteria1

1975 ◽  
Vol 38 (6) ◽  
pp. 319-322 ◽  
Author(s):  
C. N. HUHTANEN ◽  
A. R. BRAZIS ◽  
W. L. ARLEDGE ◽  
C. B. DONNELLY ◽  
R. E. GINN ◽  
...  
Keyword(s):  
Raw Milk ◽  
Plate Count ◽  
Equilibration Time ◽  
Standard Methods ◽  
Standard Plate Count ◽  
Milk Samples ◽  
Plate Count Agar ◽  
Standard Plate ◽  
Time Required ◽  
Tempering Time

Sixty raw milk samples were plated using “Standard Methods” agar tempered to 45 or 50 ± 1 C. The standard plate count was significantly lower with the agar at 50 C. Tempering time (to 44–46 C) of a flask of agar in a water bath was about 5–10 min longer than that of a comparable flask of water. Time required to reach the desired temperature depended upon the volume of agar in the flasks, the number of flasks, and the volume of the water in the bath. Up to an hour of equilibration time may be necessary for newly autoclaved agar to reach the recommended temperature (44–46 C). Insufficient tempering time might cause an excessively high plating agar temperature which might cause a reduction in bacterial counts, especially of a heat sensitive psychrotrophic bacterium.

EFFECT OF PIPETTE TYPE AND SAMPLE SIZE ON PLATE COUNT RESULTS

1965 ◽  
Vol 28 (10) ◽  
pp. 314-319 ◽  
Author(s):  
E. H. Marth ◽  
J. F. Proctor ◽  
R. V. Hussong
Keyword(s):  
Statistical Analysis ◽  
Standard Deviation ◽  
Sample Size ◽  
Raw Milk ◽  
Plate Count ◽  
Test Results ◽  
Pasteurized Milk ◽  
Milk Samples ◽  
Large Numbers ◽  
Points Of View

Summary Raw and pasteurized milk samples were plated by seven analysts using 0.1- and 1.0-ml quantities (of appropriate dilutions) dispensed by 0.1-ml glass, 1.1-ml plastic and 1.1- and 2.2-ml glass pipettes. Incubation was at 32 C for 48 hr. Data were subjected to an analysis of variance and the standard deviation as a ratio was calculated. The procedures were compared from two points of view, first to determine if biases existed between the different methods and second if the techniques differed in their random error. No appreciable differences were found between types of pipettes when pasteurized milk was plated. The quantity used, however, was important. Use of a 0.1-ml sample size was associated with more variable results which averaged 10% higher than when a 1.0-ml quantity was plated. Statistical analysis of test results obtained with pasteurized milk suggests: (a) when 0.1-ml samples were used least variation was encountered with the 0.1-ml glass pipette and most variation with the 1.1-ml glass pipette, and (b) when 1.0-ml samples were used very little difference appeared between pipettes although the 1.1-ml plastic pipette tended toward less variation. When raw milk contained large numbers of bacteria, the plastic pipette tended to give higher results than glass pipettes when the 1.0-ml quantity was used; however, these differences with raw milk were not found to be statistically significant. Standard deviations as a ratio revealed: (a) greatest variation with the 2.2-ml glass pipette and least with a 0.1-ml glass or 1.1-ml plastic pipette when a 0.1-ml quantity was used, and (b) greatest variation with a 1.1-ml plastic pipette and least with a 2.2-ml glass pipette when a 1.0-ml sample size was used.

Sanitary Evaluation of Target Flowmeter Used in a Dairy Processing Plant

1991 ◽  
Vol 54 (12) ◽  
pp. 966-968 ◽  
Author(s):  
ANNEL K. GREENE ◽  
THOMAS G. REYNOLDS ◽  
EMILY M. SOUTHERLAND
Keyword(s):  
Raw Milk ◽  
Plate Count ◽  
Processing Plant ◽  
Standard Plate Count ◽  
Plate Count Agar ◽  
Dairy Processing ◽  
Milk Flow ◽  
Standard Plate ◽  
Dairy Plant ◽  
Sanitary Conditions

A target flowmeter, used to measure raw milk flow, was examined for sanitary conditions in a university dairy plant 10 times over a period of eight weeks. The flowmeter connection was swabbed at four different locations along the dairy plant connection at four different times during the work day: i) after chlorine sanitization, before product; ii) after product, before cleaning in place (CIP); iii) after CIP, before acid sanitization; and iv) after acid sanitization, at end of day. Samples were plated in duplicate on standard plate count agar and on violet red bile agar. After routine CIP cleaning and sanitization procedures, bacterial counts were low. Additionally, no finished product contamination problems were detected over the 7 months of flowmeter use as shown by routine quality control tests on pasteurized milk which had flowed past the in-line meter as raw milk. These results indicate that normal cleaning and sanitization procedures were adequate for the in-line flowmeter.

THE INFLUENCE OF TIME AND TEMPERATURE OF INCUBATION ON THE PLATE COUNT OF MILK1

1974 ◽  
Vol 37 (4) ◽  
pp. 209-212 ◽  
Author(s):  
F. R. Roughley ◽  
C. K. Johns ◽  
K. L. Smith
Keyword(s):  
Incubation Temperature ◽  
Geometric Mean ◽  
Bacterial Count ◽  
Raw Milk ◽  
Plate Count ◽  
Geometric Means ◽  
Pasteurized Milk ◽  
Milk Samples ◽  
Significant Difference ◽  
The Mean

The geometric mean bacterial count of 131 raw milk samples, using plates incubated 48 h at 30 C, was 15% higher than the geometric mean when the bacterial counts were determined at 32 C incubation. When 72 h of incubation were used, the geometric mean of samples using the lower incubation temperature was 20% higher. The mean for all 72-h raw milk counts was 31% higher than that for 48 h counts. There was no significant difference between geometric means of 51 pasteurized milk samples using plates incubated at 30 or 32 C after 48 h incubation. After 72 h of incubation, the geometric mean obtained at 30 C was 10% higher. For all 72-h counts on pasteurized milk the mean was 55% higher than for 48 h. A number of both raw and pasteurized samples showed little or no increase in count following Preliminary Incubation at 12.8 C for 18 h while others “blew up” to high levels, suggesting undesirable contamination. The International Dairy Federation procedures tended to reflect the latter better than the SPC.

scholarly journals Frequency of 2,3,5-triphenyltetrazolium chloride (TTC) non-reducing bacteria in pasteurized milk

1999 ◽  
Vol 30 (2) ◽  
pp. 137-140 ◽  
Author(s):  
Vanerli Beloti ◽  
Márcia A.F. Barros ◽  
Júlio C. de Freitas ◽  
Luís A. Nero ◽  
Juliana A. de Souza ◽  
...  
Keyword(s):  
Culture Media ◽  
Plate Count ◽  
Microbiological Analysis ◽  
Triphenyltetrazolium Chloride ◽  
Pasteurized Milk ◽  
Milk Samples ◽  
Plate Count Agar ◽  
Laboratory Procedures ◽  
Reducing Bacteria ◽  
Gram Positive Cocci

2,3,5-triphenyltetrazolium chloride (TTC) is a dye largely used for enumeration of microbial colonies in solid culture media, being a key component of the dry rehydratable film system used for microbiological analysis of food. This dye is colorless in the oxidized form and red when reduced by microorganisms, due to formation of formazan. In this study, TTC was added to Plate Count Agar (PCA) for enumeration of microorganisms in thirty four pasteurized milk samples, with the aim to verify the frequency of microorganisms that are unable to reduce TTC. Milk samples were decimally diluted in saline and pour-plated in PCA plus 0.015% TTC. Colonies were counted after 24h and 48 h of incubation at 35oC. From a total of 50,574 colonies, 19,665 (38.88%) did not reduce TTC in 48h. It was observed that 571 (6.36%) colonies that were colorless in 24h became red in 48h. From those that didn't reduce TTC in 48h, 233 were purified and Gram stained. 229 (98.71%) of them were Gram positive cocci and bacilli. The results show that there is a high percentage of microorganisms unable to reduce TTC in pasteurized milk, which cannot be detected by laboratory procedures based on the formation of red colonies.

Correlation between mastitis occurrence and the count of microorganisms in bulk raw milk of bovine dairy herds in four selective culture media

2009 ◽  
Vol 77 (1) ◽  
pp. 63-70 ◽  
Author(s):  
Luís I M Souto ◽  
Clarice Y Minagawa ◽  
Evelise O Telles ◽  
Márcio A Garbuglio ◽  
Marcos Amaku ◽  
...  
Keyword(s):  
Mammary Gland ◽  
Negative Correlation ◽  
Culture Media ◽  
Agar Plate ◽  
Raw Milk ◽  
Blood Agar ◽  
Plate Count ◽  
Dairy Herds ◽  
Potassium Tellurite ◽  
Positive Correlations

Milk is the normal secretion of the mammary gland, practically free of colostrum and obtained by the complete milking of one or more healthy animals. Mastitis is an inflammatory process of the mammary gland and it may cause alterations in the milk. The present work aimed to verify whether it is possible, by means of the counts of microorganism in the bulk raw milk in four selective culture media, to establish a correlation with the occurrence of mastitis and therefore, to monitor this disease in bovine dairy herds. The following selective culture media were used: KF Streptococcus Agar, Edwards Agar, Baird-Parker Agar, Blood Agar plus potassium tellurite. Spearman's correlation coefficient was calculated in order to compare the occurrence of mastitis (percentage) in each herd with respective selective culture media counts of microorganisms in bulk raw milk. Thirty-six possibilities were analysed (Tamis and CMT-positive rates were compared with the log-transformed count in four selective culture media) and there was a negative correlation between Tamis 3 and the Baird-Parker Agar plate count. The total results of microbiological tests showed that there were three correlations of the counts in selective culture media. Fifty-two possibilities were analysed and there was a negative correlation between no-bacterial-growth mastitis rates and log10 of KF Streptoccocus Agar plate count and there were two positive correlations between coagulase-positive staphylococci and log10 of Baird-Parker Agar plate count and Blood Agar plus potassium tellurite plate count.

Determination of Viable Bacterial Populations in Raw Milk within 20 Minutes by Using a Direct Epifluorescent Filter Technique

1997 ◽  
Vol 60 (7) ◽  
pp. 874-876 ◽  
Author(s):  
CLAUDE P. CHAMPAGNE ◽  
NANCY J. GARDNER ◽  
JULIE FONTAINE ◽  
JACQUES RICHARD
Keyword(s):  
Raw Milk ◽  
Plate Count ◽  
Bacterial Populations ◽  
Filter Technique ◽  
Milk Samples ◽  
Standard Plate ◽  
Plate Counts ◽  
Direct Epifluorescent Filter Technique ◽  
Triton X

The results from a shortened procedure for the direct epifluorescent filter technique (DEFT) determination of viable bacterial populations in raw milk were compared to standard plate counts. Shortening the prefiltration trypsin-Triton X-100 incubation period from 10 to 3 min enabled the completion of the analysis within 20 min. The short DEFT method results had a correlation coefficient (r) of 0.81 with plate counts. With respect to precision, the average difference between values of duplicate plate count analyses was 0.16 log units; that of the short DEFT was 0.14 log units. The slopes of the regressions equations were less than 1, indicating that a direct correlation is not achieved. Short DEFT values were 0.17 log units higher than those of plate counts on milk samples containing less than 10,000 CFU/ml. For milk samples containing counts over 10,000 CFU/ml, short DEFT values averaged only 0.05 log units above plate count readings. Daily preparation of the stain appears unnecessary since acridine orange solutions stored for up to 2 days at 4°C did not produce results significantly (P > 0.05) different from those obtained with fresh solutions. The short DEFT method has potential for the assessment of the bacteriological quality of raw milk in tanker deliveries.

Low Incidence of Foodborne Pathogens of Concern in Raw Milk Utilized for Farmstead Cheese Production

2008 ◽  
Vol 71 (8) ◽  
pp. 1580-1589 ◽  
Author(s):  
DENNIS J. D'AMICO ◽  
ERROL GROVES ◽  
CATHERINE W. DONNELLY
Keyword(s):  
Foodborne Pathogens ◽  
Microbiological Quality ◽  
Goat Milk ◽  
Raw Milk ◽  
Pasteurized Milk ◽  
Milk Samples ◽  
Cell Counts ◽  
Standard Plate ◽  
Low Incidence ◽  
Raw Milk Cheese

Overall milk quality and prevalence of four target pathogens in raw milk destined for farmstead cheesemaking was examined. Raw milk samples were collected weekly from June to September 2006 from 11 farmstead cheese operations manufacturing raw milk cheese from cow's, goat's, and sheep's milk. Samples were screened for Listeria monocytogenes, Staphylococcus aureus, Salmonella, and Escherichia coli O157:H7 both quantitatively (direct plating) and qualitatively (PCR). Overall, 96.8% of samples had standard plate counts of <100,000 CFU/ml, 42.7% of which were <1,000 CFU/ml. Although no federal standards exist for coliforms in raw milk, 61% of samples tested conformed to pasteurized milk standards under the U.S. Pasteurized Milk Ordinance (PMO) at <10 CFU/ml. All cow and sheep milk samples and 93.8% of goat milk samples were within the limits dictated by the PMO for somatic cell counts. Of the 11 farms, 8 (73%) produced samples that were positive for S. aureus, which was detected in 34.6% (46 of 133) of milk samples. L. monocytogenes was isolated from three milk samples (2.3%), two of which were from the same farm. E. coli O157:H7 was recovered from one sample of goat's milk for an overall incidence of 0.75%. Salmonella was not recovered from any of the 133 samples. The findings of this study suggest that most raw milk intended for farmstead cheesemaking is of high microbiological quality with a low incidence of pathogens. These data will help inform risk assessments associated with the microbiological safety of farmstead cheeses, particularly those manufactured from raw milk.

Rapid Detection of Psychrotrophic Bacteria In Manufacturing Grade Raw Milks

1991 ◽  
Vol 54 (11) ◽  
pp. 861-867 ◽  
Author(s):  
S. R. TATINI ◽  
P. MEKALA ◽  
A. EL-HABAZ ◽  
M. W. GRIFFITHS
Keyword(s):  
Rapid Detection ◽  
Bacterial Count ◽  
Raw Milk ◽  
Plate Count ◽  
Psychrotrophic Bacteria ◽  
Milk Samples ◽  
Microscopic Count ◽  
Direct Epifluorescent Filter Technique ◽  
Native Microflora

Methods to rapidly assess the bacteriological quality of raw milk were investigated. Whereas direct microscopic count, modified psychrotrophic plate count, and direct epifluorescent filter technique (DEFT) did not correlate well with initial psychrotrophic bacterial count of raw milk, improvements were obtained after preincubation of the milk samples. The best preincubation conditions were identified as 30°C for 6 h, 21°C for 10 h, 13°C for 15 h, 13°C for 20 h, or 7°C for 37 h. The “square root” equation was applied to the data, and a model was produced for predicting growth of the native microflora of raw milk. Using this equation, a DEFT count after preincubation of the milk at 21°C for 10 h could accurately predict the initial psychrotroph count and the count after storage of the milk at 6°C for 48 h.

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