Microbiological Quality of Raw Cow's Milk at Collection Centers in Trinidad

Abstract

The microbial quality, pH and presence of selected pathogens in milk at eight collection centers in Trinidad were determined. The enterotoxigenicity and susceptibility of Staphylococcus aureus strains to antimicrobial agents and bacteriophages were investigated while the antibiograms and ability of Escherichia coli isolates to agglutinate O157 antiserum were also assessed. Of the 287 milk samples tested, the mean pH was 6.80 ± 0.10 and 207 (72.1%) were California mastitis test (CMT) positive. All (100.0%) milk samples contained S. aureus, and 217 (75.6%) were positive for E. coli. The ranges of mean counts per ml for total aerobic bacteria, S. aureus and E. coli were 3.3 ¥ 106 to 9.8 ¥ 107, 1.4 ¥ 104 to 1.2 ¥ 105 and 4.2 ¥ 104 to 1.6 ¥ 106, respectively. Ninety-three (40.4%) of 230 strains of S. aureus tested were enterotoxigenic producing staphylococcal enterotoxins A, B, C, D or a combination with SEC being predominantly elaborated. Of the 245 strains of S. aureus phage-typed, 123 (50.2%) were susceptible to international phage set (IPS) of bacteriophages. Overall, 49 (49.0%) of 100 strains of S. aureus tested were resistant to 1 or more of the 8 antimicrobial agents with resistance high to penicillin (48.0%), ampicillin (45.0%) and methicillin (21.0%). Among 100 strains of E. coli tested, 98 (98.0%) exhibited resistance to antimicrobial agents with high prevalence of resistance detected for cephalothin (79.0%), ampicillin (73.0%) and streptomycin (47.0%). Thirteen (6.9%) of 188 strains of E. coli agglutinated with O157 antiserum. It was concluded that the presence of some pathogens in milk in fairly high counts coupled with toxigenicity of some strains pose a health hazard to consumers.

Bacteriological quality and safety of raw cow milk in Madurai (South India)

“…However, the rate of isolation of the organism was very much lower than (40%) reported from other tropical countries (Umoh et. al., 1990 andAdesiyun et. al., 1995).…”

Development of Kinetic Models Describing Kinetic Behavior of Bacillus cereus and Staphylococcus aureus in Milk

“…The modified Gompertz model is expressed as (1) where N t is the bacterial cell number at time t(h), A is the initial cell number of the pathogens, C is the difference between the upper asymptotic line of the growth curve and the lower asymptotic line, B is the relative growth rate at time M, and M is the time at which the growth rate is maximum (h). Maximum specific growth rate (µ max ; Log CFU/ml/h), lag phage duration (LPD; h), and N max (Log CFU/mL) were calculated by following equations (2) where e is 2.7182, and…”

“…For this reason, milk has received much attention, because it may serve as a vehicle for disease agents (Klein, 1901). In fact, raw milk often contains microorganisms that may cause food-borne diseases (Adesiyun et al, 1995;Headrick et al, 1998;Steele et al, 1997). Therefore, in most countries, restrictions and legislation regulating the marketing of unpasteurized milk have been introduced to minimize health risks associated with milk products (European Commission, 2000).…”

A comparison of selected public health criteria in milk from milk-shops and from a national distributor

“…Unless data were to become available to prove to the contrary, it seems realistic to assume that milkborne diseases are probably at least as prevalent in South Africa as in other countries under conditions of industrialised mass production and distribution of raw and pasteurised dairy products. Surveys conducted on raw milk samples in other developing countries showed that on the whole the quality was bad [1][2][3][4]26,28,29 . As a result of the deregulation of the South African dairy industry in the early 1990's, 'milk-shops' have become a common retail outlet for milk which would not qualify for sale to large national distributors, especially in the lower socio-economic areas.…”