Occurrence, antimicrobial susceptibility, and resistance genes of Staphylococcus aureus in milk and milk products in the Arsi highlands of Ethiopia

BACKGROUND

In Ethiopia, milk production and handling practices often lack proper hygiene measures, leading to the potential contamination of milk and milk products with Staphylococcus aureus (S. aureus), including methicillin-resistant strains, posing significant public health concerns. This study aimed to investigate the occurrence, antimicrobial susceptibility profiles and presence of resistance genes in S. aureus strains isolated from milk and milk products.

METHODS

A cross-sectional study was conducted in the Arsi highlands, Oromia, Ethiopia from March 2022 to February 2023. A total of 503 milk and milk product samples were collected, comprising 259 raw milk, 219 cottage cheese, and 25 traditional yogurt samples. S. aureus isolation and coagulase-positive staphylococci enumeration were performed using Baird-Parker agar supplemented with tellurite and egg yolk. S. aureus was further characterized based on colony morphology, Gram stain, mannitol fermentation, catalase test, and coagulase test. Phenotypic antimicrobial resistance was assessed using the Kirby-Bauer disc diffusion method, while the polymerase chain reaction (PCR) was employed for confirming the presence of S. aureus and detecting antimicrobial resistance genes.

RESULTS

S. aureus was detected in 24.9% of the milk and milk products, with the highest occurrence in raw milk (40.9%), followed by yogurt (20%), and cottage cheese (6.4%). The geometric mean for coagulase-positive staphylococci counts in raw milk, yogurt, and cottage cheese was 4.6, 3.8, and 3.2 log10 CFU/mL, respectively. Antimicrobial resistance analysis revealed high levels of resistance to ampicillin (89.7%) and penicillin G (87.2%), with 71.8% of the isolates demonstrating multidrug resistance. Of the 16 S. aureus isolates analyzed using PCR, all were found to carry the nuc gene, with the mecA and blaZ genes detected in 50% of these isolates each.

CONCLUSION

This study revealed the widespread distribution of S. aureus in milk and milk products in the Arsi highlands of Ethiopia. The isolates displayed high resistance to ampicillin and penicillin, with a concerning level of multidrug resistance. The detection of the mecA and blaZ genes in selected isolates is of particular concern, highlighting a potential public health hazard and posing a challenge to effective antimicrobial treatment. These findings highlight the urgent need to enhance hygiene standards in milk and milk product handling and promote the rational use of antimicrobial drugs. Provision of adequate training for all individuals involved in the dairy sector can help minimize contamination. These measures are crucial in addressing the threats posed by S. aureus, including methicillin-resistant strains, and ensuring the safety of milk and its products for consumers.

Factors affecting the microbiological quality and contamination of farm bulk milk by Staphylococcus aureus in dairy farms in Asella, Ethiopia

BACKGROUND

The determination of the microbiological quality and safety of raw milk and the associated influencing factors at the farm level is very critical given that the quality or safety of subsequent products that are further produced depends on this. Therefore, this study aimed to determine the microbiological quality and safety of bulk milk and identify associated risk factors, and assess the presence/absence of S. aureus in bulk milk with potential contaminating sources in dairy farms in Asella, Ethiopia.

RESULTS

The geometric means of bacterial counts in farm bulk milk were 5.25 log cfu/ml, 3.1 log cfu/ml and 2.97 log cfu/ml for total bacterial count (TBC), coliform count (CC) and coagulase-positive staphylococci count (CPS), respectively. Of the 50 dairy farms, 66, 88, and 32% had TBC, CC and CPS counts, respectively, that exceeded the standard international limits for raw cow's milk intended for direct human consumption. TBC tended to increase as CC increased in bulk milk (r = 0.5). In the final regression model, increased TBC, CC and the contamination of farm bulk milk by S. aureus were significantly associated with dirty barns, dirty cows and soiled udder and teats. TBC was higher during the rainy season than during the dry season. The reported practice of washing teats with warm water significantly decreased CC and CPS. The occurrence of S. aureus was significantly (p < 0.05) higher in bulk farm milk (42%) than in pooled udder milk (37.3%), teat swabs (22.5%), milkers' hand swabs (18%), bulking bucket swabs (16.7%), milking container swabs (14%), and water for cleaning of udder and milkers' hands (10%). The questionnaire survey result showed widespred raw milk consumption habits, low level of training and poor hygienic milking practices.

CONCLUSIONS

This study revealed low-quality bulk farm milk with high bacterial counts and a high occurrence of S. aureus. This indicates the potential food safety risks due to consumption of raw milk or its products. This study suggests awareness creation to dairy farmers and the public on hygienic milk production and heat treatment of milk before consumption.

Knowledge and practice of mothers/care-takers towards diarrhoea and its treatment in rural communities in Ethiopia

Diarrhoeal diseases are major causes of childhood morbidity and mortality in developing countries. Knowledge and practices of mothers or other care-takers of children are important determinants of the occurrence or outcome of diarrhoeal diseases. Base-line information on these variables is also needed for developing health education programmes and for formulating national policy on home fluid therapy. This study was conducted with the objectives of assessing the knowledge and practice of mothers and other caretakers of children towards diarrhoeal diseases and the sociodemographic correlates of adequate knowledge and practice. A study was conducted in the rural North, South, East and West Shewa Administrative Regions in April, 1990. A two-stage cluster sampling proportionate to size was used to select a total of 750 mothers or other caretakers. These were interviewed by trained and supervised health workers who used a pretested questionnaire. The three major ethnic groups were Oromo, Guragie and Hadya. Of the total respondents, 79.3% were illiterate, 78.5% got their water from unprotected sources, 88.9% had no latrines, 80.4% had no access to mass media and 7.1% spent more than 2 hours to reach to the nearest health facilities. Only 2.6% and 5.7% of mothers had adequate knowledge and practice on diarrhoea or its treatment, respectively. Age and educational level of mothers or other caretakers were found to be positively associated with adequate knowledge and practice towards diarrhoea and its treatment. The study clearly indicated that health education messages have not been effectively disseminated to the rural population. It is, therefore, strongly recommended that the Diarrhoeal Diseases Control Programme strengthens its communication activities through increasing persuasion of health workers who could serve as effective means of reaching the population who have access to health services.

Patterns of breast feeding in western Ethiopia and their relationship to acute diarrhoea in infants

To determine the extent of protection from breast feeding against acute diarrhoea, a cross-sectional study was conducted in rural areas in a western region of Ethiopia, Gamo-Gofa. The standard cluster sampling technique promoted by WHO/CDD Program was used. We employed trained and supervised health workers (physicians nurses, and sanitarians) as interviewers, and a pretested questionnaire was utilized for the purpose. Among a total of 3002 children under the age of 5 years surveyed for diarrhoeal disease morbidity, mortality, and treatment rates, all those 6 months of age and less (n = 331) were taken as subjects to examine the trends of breast feeding and their association with the occurrence of acute diarrhoeal diseases. It was found that out of these 331 infants, 217 (66 per cent) were exclusively breast-fed and 114 (34 per cent) were partially breast-fed. No one in the study group was fully weaned. Out of those who were exclusively breast-fed (n = 217), 25 (12 per cent) had diarrhoea which started within the past 2 weeks of the survey. Among those partially breast-fed (n = 114), 46 (40 per cent) had diarrhoea. The difference in the occurrence of diarrhoea among exclusively and partially breast-fed infants was statistically significant (P less than 0.0001). When infants with partial breast feeding were contrasted with those on exclusive breast feeding, a relative risk of developing diarrhoea of 5.2 (95 per cent confidence interval 3.00, 9.10) was obtained. It is recommended that breast feeding which tends to diminish with urbanization be promoted as one important intervention of the control of diarrhoeal diseases.