Bacteria and food poisoning organisms in milk

Abstract

Individual milk samples of 50 goats, 50 ewes and 50 cows were examined for the total viable count, coliform bacteria, staphylococci and salmonellae. Growth of enterotoxin A producing Staphylococcus aureus NCTC 10652 in the milk of the three animal species was also studied. The average total count was 1.9 X 10(7) cells/ml for cow's, 7.7 X 10(6) for goat's and 2.7 X 10(6) for ewe's milk with micrococci staphylococci, rods and streptococci being the predominant organisms in the three milks, respectively. Goat's milk contained the lowest numbers of coliforms and ewe's milk the highest numbers. Staphylococcus aureus could not be detected in goat's milk, whilst 16 and 26% of the ewe's and cow's milk samples contained 100 and 80 cells/ml, respectively. Out of 39 coagulase positive staphylococci, 27 were thermonuclease positive, 18 produced lecithinase and 15 fermented mannitol. Red blood cells of sheep origin were much more resistant to lysis by ewe's strains compared to bovine strains. Growth curves of Staphylococcus aureus were nearly linear at 17 degrees C but exponential at 31 degrees C without lag phase. Hazardous numbers of about 10(6) cells/ml were readily reached at 31 degrees C after 6 h and at 17 degrees C after 18 h. Salmonellae could not be detected in any of the samples examined. Out of 19 enterobacteria suspected to be salmonellae 11 proved to be Proteus and 8 Citrobacter.

Culture versus PCR forSalmonellaSpecies Identification in Some Dairy Products and Dairy Handlers with Special Concern to Its Zoonotic Importance

“…Salmonella species were not detected in any of the examined bulk tank milk samples by conventional culture methods. This result is in agreement with some researchers [25, 26] who failed to isolate Salmonella from their examined milk samples. On the contrary, high isolation rate (2.7%) was previously obtained by other researchers [27].…”

Bacteriological quality of raw ewe’s and goat’s milk, with special references to foodborne pathogens

“…The results listed in Table (6) revealed that the Clostridium perfringens, Campylobacter jejuni, Corynebacterium bovis and Salmonellae failed to be detected in any of examined samples of ewe's and goat's milk. Similar finding were reported by ( Abo-Elnaga et al, 1985;Faschino et al, 2002;Muehlherr et al, 2003). While, Roberts, (1985) could detect Campylobacter jejuni in only one samples.…”

“…Results listed in Table (1) revealed that the total bacterial counts/L of examined ewe's and goat's milk samples were ranged from 1.0 x10 2 to 1.5 x10 4 and 2.0 x10 2 to 9.0 x10 3 with mean values of 1.9 x10 3 and 1.4 x10 3 , respectively. Higher total bacterial count in ewe's milk was obtained by (Abo-Elnaga et al, 1985) while, higher total bacterial counts in both types were reported in goat's milk (Roberts, 1985;Faschino et al, 2002;Muehlherr et al, 2003;Zweifel et al, 2005). The lower value of total bacterial count in goat's milk was obtained by (Zeng and Escobar 1996).…”

“…could be detected in 52.0 and 84.0 % of examined ewe's and goat's milk samples with mean values of 7.2 x10 and 6.1 x10, respectively. Lower percentages and lower counts/ml were reported (Abo-Elnaga et al, 1985;Roberts, 1985;Little and De Louvois, 1999;Muehlherr et al, 2003) while, higher counts were reported by (Faschino et al, 2002;Holeckova et al, 2004) Deinhofer and Pernthaner, 1993 because one of the important causes of mastitis either in ewes or goats is staphylococci (Smith and Roguinsky, 1977). The results tabulated in Table (4) revealed that the enterococci could be detected in 44.0 and 36.0 % of examined ewe's and goat's milk samples with mean values of 2.5 x10 and 2.4 x10, respectively.…”

The Staphylococcal Enterotoxins

“…Staph. aureushzs been shown to produce enterotoxins A, B, C and/or D in the milk of sheep (Bautista et al, 1988), goats (Valle et al, 1990;Adesiyun, 1994Adesiyun, , 1995Adesiyun et al, 1998) and catde (Tatini et al, 1971a;Olsvik et al, 1982;Abo-Elnaga et al, 1985;Kayihura etal., 1987;Umoh et al, 1990). Dairy products may also contain toxins and/or toxin-producing Staph.…”