Nocardia Isolated From Soil and its Potential to Induce Mastitis in Goats

Abstract

This Study was conducted to isolate and identify nocardiae from soil samples collected from different sites of Sudan and to use these isolates to experimentally induce mastitis in Nubian goats. Eight soil samples were collected from the following sites in Sudan, Hag A bdalla, Rehaid Elbridy, Elgadareif, Eldalanj, Kassala, Shambat. The samples were cultured on tryptic soy agar (T. S. A) and incubated aerobically at 37°C for up to 5 days. Nine nocardia isolates were recovered from the cultured samples. The isolated strains were phenotypically characterized using morphological, cultural, biochemical and mycolic acid analysis. The phenotypic characterization of the isolates classified them into 3clusters: Cluster 1 was typically N. brasilliensis, Cluster 2, was characteristically N. asteroides and Cluster 3 was identified as N. farcinica. Two of the isolates were not identified as typical nocardia although they were morphologically resemble nocardia. The test for viability of N. farcinica in contaminated fence soil established that, under natural conditions, N. farcinica could remain viable in soil for 30 months. From the isolated Nocardiae N. farcinica AB14, N. farcinica AB15, and a control strain N. farcinica SD1800 were used for experimental induction of mastitis in two Nubian goats. The two strains caused mild mastitis associated with high leukocytes count with no systemic reactions. The organisms were constantly execreted in the milk and were demonstrated in smears and cultures. The two infected goats were treated with broad spectrum antibiotics Neomastipra intramammary infusion but did the infection did not respond to it. After the end of the withdrawal period of Neomastipra, treatment of mastitis was tried using Gentamast but also failed to get rid of infection. After the withdrawal period of both drugs, nocardiae were recovered in pure cultures on T.S.A. The study concluded that Nocardiae are readily available in soil samples and could cause mastitis in goats. Further, the finding showed that Tryptic Soy Agar medium with combination of 5μg /ml tetracycline, 50μg /ml nystatine and 5%NaCl was the best medium for isolation of nocardiae from soil.