Prevalencel of Imstitic Staphylococci Str eptococci and coliflorm (Escherichia Coli) in Threee Dairy Farhs in and Around Addis Ababa

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Addis Ababa University


Prevalence of mastitic staphylococci, streptococci & coliform species in foremilk samples of apparently healthy lactating cows was studied in 3 dairy farms. One hundred & twenty apparently healthy lactating cows were randomly selected on the basis of lactation numbers. These were 40 from Debre Zeit, 40 from Repi & 40 from Kumbi dairy farms. Pooled foremilk samples \~ere co11ected from the teats of each lactating cO\~ & totally 120 foremilk samples were collected & analysed from the 3 farms. The total mesophilic aerobic bacterial, streptococcal & staphylococcal counts & the bacterial counts of Staphylococcus & Streptococcus species were estimated using different kinds of media. The susceptibilities of 55 isolates of mastitic staphylococcal & streptococcal strains to 11 antibiotics was determined using the standard agar disc diffusion technique. The total mesophilic aerobic bacterial counts was highly variable & ranged from hundreds to mi11ions in a11 of the dairy farms. The high total mesophilic aerobic bacterial counts greater than or equal to 1 x 105 colony forming units I mi11iliter were mainly associated with high numbers of streptococcal counts. Staphylococci were regularly isolated in all foremilk samples, however, their contribution to increases in the total mesophilic aerobic bacterial count was not as significant as that of rd ' streptococci. At the 3 & subsequent lactations, the number of co\~s that had total mesophilic aerobic bacterial counts'greater than or equal to 2xl04 colony forming units/milliliter increased at Kumbi & Repi farms. At the Debre Zeit farm, with increases in lactation numbers the number of cows that had greater than or equal to lxlO 5 colony forming units/milliliter was high.Five hundred & thirty five isolates were biochemically tested from the 120 samples. Of these 312 belonged to Staphylococcus, 215 belonged to Streptococcus, 6 belonged to Micrococcus & 2 belonged to coliform. Five species & 2 subspecies of staphylococci, 7 species of streptococci & 1 coliform species were identified. Among mastitic staphylococci, Staphylococcus epidermidis was the most prevalent and was isolated from 80.8% of the foremilk samples, followed by Staphylococcus aureu~ (20%), Staphylococcus hyi~ subsp. chromogenes (12.5%), Staphylococcus hyicus subsp. hyicus (5.8%). Similarly, other Staphylococcus species were also isolated in different proportions: Staphylococcus simulans (6.7%), Staphylococcus xylosus (4.2%), Staphllococcus intermedius (0.83%) & Staphylococcus hominis/Staphylococcus w~rneri / Staphylococcus haemolyticus group (6.7%). Of the mastitic streptococcal strains, Streptococcus bovis was the most prevalent &was isolated from 40.8% of the lactating cows sampled, followed·by Streptococcus uberis (15.8%), Streptococcus dysagalactiae (14.2%), Streptococcus agalactiae (9.2%), Streptococcus faecalis (5%), Streptococcus sp. G (5.8%) & Streptococcus infrequens (0.8%). Other streptococcal strains were also isolated. Streptococcus lactis lias detected in 0.8% of the samples. Generally the frequency of isolation for Streptococcus uberis, Streptococcus dysagalactiae, Streptococcus agalactiae & Staphylococcus aureus was high during the latter lactation numbers (3, 4 & 5). Escherichia coli was not common in the herds & was detected in 1.7% of the foremilk samples from one herd only. Among 30 isolates of staphylococcal strains tested, 26.7% lIere resistant to penicillin & tetracycline. All the staphylococcal strainsliere sensitive to erythromycin, oxacillin, cephalothin, chloramphenicol, kanamycin, gentamycin, streptomycin, clindamycin & vancomycin. Of 25 isolates of streptococcal strains, resistance to oxacillin, tetracycline, kanamycin, gentamycin, streptomycin was sholin by 8, 23, 8 16 & 40% of the iso1ate~. respectively. All the streptococcal strains were sensitive to penicillin, erythromycin, cephalothin, c1indamycin, vancomycin & chloramphenicol.