PREVALENCE, RISK FACTORS, ANTIBIOGRAM AND IN VITRO ACTIVITY OF NANOENCAPSULATED BROMELAIN AGAINST BACTERIA ISOLATED FROM MILK OF DAIRY GOATS WITH SUB-CLINICAL MASTITIS IN THIKA EAST SUB-COUNTY, KENYA

Abstract

Mastitis causes the greatest losses in dairy goat production. There is insufficient information on the prevalence and risk factors of sub-clinical mastitis and current antibiotic sensitivity in many counties in Kenya. The objectives of the study were to determine the prevalence and risk factors of subclinical mastitis in dairy goats, Thika East Sub-county, Kenya and thereafter, the associated bacterial pathogens, their antibiogram and sensitivity to nanoencapsulated bromelain. The mecA gene is responsible for resistance to beta-lactam antibiotics and its presence was determined in the S. aureus isolates. Goat level data was obtained for 110 lactating dairy goats of different breeds, parity and lactation stages. Farm level data on risk factors was obtained from 41 small-scale farmers using questionnaires. Milk was obtained from 110 lactating dairy goats and tested for mastitis using California Mastitis Test (CMT). The prevalence of subclinical mastitis at goat level was estimated to be at 50.9% using CMT out of which 86.5% yielded bacteria on culture. The significant risk factors associated with the occurrence of subclinical mastitis were cleaning schedule (p=0.022, OR=1.047) and parity of the goat (p=0.048, OR=1.37). A higher prevalence of sub clinical mastitis was observed for goats residing in houses cleaned at least once a fortnight. Does in the fourth and higher parity were most affected by subclinical mastitis. Milk samples from goats were cultured and bacteria identified using culture and standard identification methods. One hundred and sixty nine (169) bacterial isolates were obtained from culture of which 52 isolates from 7 major classes of isolated bacteria were tested for antibiotic sensitivity to six common antibiotics namely Penicillin G, Tetracycline, Norfloxacin, Chloramphenicol, Gentamycin and Streptomycin. Bromelain, chitosan and nanoencapsulated bromelain xv were also tested for antibacterial activity against the major isolated bacterial groups. The Minimum inhibitory concentration was also determined. Fourteen different bacteria including; Coagulase Negative Staphylococci (20.7%), Serratia spp. (19.5%), Citrobacter spp. (16%), Klebsiella spp. (11%), Staphylococcus aureus (10.7%), Enterobacter spp. (6.5%), Escherichia. coli (5.9%), Proteus spp. (3%), Corynebacterium spp. (1.8%), Morganella spp. (1.8%), Streptococcus spp. (1.2%), Providencia spp. (0.6%), Micrococcus spp. (0.6%), Staphylococcus intermidius (0.6%) were isolated and identified from the milk samples. The identity of Staphylococcus aureus isolates was confirmed by the polymerase chain reaction using S. aureus specific 16S rRNA primers. All (100%) of isolates that had been identified as S. aureus using biochemical tests were confirmed by PCR. All (100%) the tested isolates were resistant to Penicillin G while 98% of the isolates were sensitive to Streptomycin. Bromelain and nanoencapsulated bromelain showed antibacterial activity against tested isolates. Nanoencapsulated bromelain was more effective against the tested isolates than bromelain. Due to lack of a positive control, the absence of the mecA gene in the S. aureus isolates was not definitive. In conclusion, the study showed that a large proportion (50.9%) of goats in the study area was affected by subclinical mastitis, the main bacteria being Staphylococci spp and coliforms. Most of the tested antibiotics can be used in the treatment of mastitis although resistance to Penicillin G and Tetracycline was noted in large number of isolates. Citrobacter spp was found to be the most resistant bacterial species. Bromelain, nanoencapsulated bromelain and chitosan were found to be effective broad spectrum antibacterial agents against bacteria causing sub-clinical mastitis in dairy goats. The low Minimum Inhibitory Concentration obtained for xvi nanoencapsulated bromelain warrants further testing in vivo. Farmers need to be trained on improved control of mastitis through adoption of good dairy husbandry and milking practices.