A novel bacterial infection in cultured Nile tilapia, Oreochromis niloticus in New Valley, Egypt

Abstract

Micrococcus luteus (M. luteus) is an emerging opportunistic fish pathogen that results in considerable economic losses among the infected fish. In the present study, a total number of 300 cultured Nile tilapia, Oreochromis niloticus were collected from concrete ponds farms in Alkharga and Aldakhla oases, New Valley governorate during the period from March to July 2019 and subject to clinical and bacteriological examination. The infected fish exhibited excessive skin pigmentation or depigmentation, scales loss, skin hemorrhages, body ulcers, fins congestion and rot, corneal opacity, and exophthalmia. Internally, congested enlarged liver, spleen, and kidney were observed., The prevalence of M. luteus infection was 10.3% and a total number of 31 isolates were recovered from infected fish. These isolates were biochemically similar except for Arginine hydrolysis, Vogus-Proskauer and Urease tests. The isolation and biochemical characterizations suggested that the isolates belong to the genus Micrococcus. The recovered M. luteus isolates were pathogenic to O. niloticus, this is the first report of M. luteus infection in O. niloticus in Egypt.