Microbiological quality and antibiotic residues in informally marketed raw cow milk within the coastal savannah zone of Ghana.

OBJECTIVES: To investigate the microbiological quality and the presence of antibiotic residues in raw cow milk and in some indigenous milk products produced and marketed by the informal sector in the coastal savannah zone of Ghana. METHODS: Milk samples were aseptically collected from 224 kraals and samples of 26 indigenous milk products were purchased from processors and retailers. Total plate counts, total coliform counts and the presence of Escherichia coli and E. coli O157:H7 were determined in all 250 samples. Milk samples were also tested for antibiotic residues. RESULTS: Total plate counts exceeded 105 CFU/ml in 45.2% of the samples while coliforms exceeded 10³ CFU/ml in 66.0% and E. coli was detected in 11.2%. E. coli was present in raw cow milk but not in the indigenous products and all E. coli isolates were negative for E. coli O157:H7. Antibiotic residues were detected in 3.1% of the raw cow milk samples. CONCLUSION: Bulk milk contains unacceptable levels of hygiene indicators and antibiotic residues and is a potential source of milk-borne infections. The detection of E. coli and antibiotic residues raises public health concerns about the safety of fresh unpasteurized cow milk in the coastal savannah zone of Ghana and calls for improved farm hygiene, the need for milk pasteurization and the sensible use of antibiotics in the milk industry.

Reproduction and mortality in a colony of captive greater cane rats, Thryonomys swinderianus, Temminck.

The reproductive performance and mortalities in a colony of captive greater cane rats, Thryonomys swinderianus, were monitored from 1992 to 1998 at the Grasscutter Domestication Centre, Achimota, Ghana. The animals were kept in cages and exposed to constant lighting from a 100 W electric light bulb during the night. The diet consisted mainly of freshly cut Panicum maximum (guinea grass) fed ad libitum, with occasional supplements of cassava and cane sugar. The results indicate that the mean litter size and litter weight were 2.9 +/- 0.51 and 439.4 +/- 81.23 g, respectively. These figures are low compared to those reported elsewhere. However, the mean birth weight was 151.2 +/- 11.08 g, higher by 12% than previously reported values. It is considered that poor nutrition, excessive exposure to light and stress were responsible for the relatively poor reproductive performance reported in these animals. The main causes of death were traumatic injuries (32%) and pulmonary congestion (16%).

Chemotherapy of dermatophilosis--a preliminary study.

In view of the unpredictability of results of antibiotic therapy of bovine dermatophilosis and following the report of successful use of 10% formalin administered intravenously at the dosage of 20 ml per 100 kg body weight, a trial was undertaken to evaluate the latter treatment in naturally-occurring dermatophilosis in a group of Friesian crossbred cattle. Group 1 animals were given only 10% formalin. Group 2 received 10% formalin and long-acting oxytetracycline (L/AO) at a dosage of 20 mg per kg body weight and Group 3 animals were given only L/AO. Treatments were repeated at intervals of four days. All animals recovered fully, the formalin only-treated ones after three treatments the L/AO-treated ones after a mean of 2.7 treatments and the combination-treated animals after a mean of 1.5 treatments. One LA/O-treated animal showed relapse after four months. This study is continuing.

Effects of exogenous amino acids on the multiplication of porcine Escherichia coli.

The multiplication rates of 70 porcine Escherichia coli strains were compared in minimal medium and in medium supplemented with aspartic acid, lysine, serine and threonine, which were the amino acids taken up during multiplication of porcine E. coli in a complex medium. The effects of these amino acids singly or in combinations and the amino acids norleucine and norvaline on the growth of porcine E. coli were studied. Together, aspartic acid, threonine, serine and lysine increased the multiplication rates of 42.9% of the strains, an effect traced to aspartic acid, but they had no effect on an equal number of strains. The rest were inhibited, and this effect was traced to serine. Cysteine, threonine, leucine and phenylalanine singly inhibited some or all of the strains tested. Norleucine and to a lesser extent, norvaline greatly prolonged the lag phase of culture in minimal medium. The inhibitory effect of norleucine was reversed by only methionine, although isoleucine, leucine and valine which were more effective in norvaline inhibition, also showed limited antagonism to norleucine inhibition.