Abstract:
A cross-sectional study was conducted to estimate the prevalence, serotypes, antimicrobial
resistance and plasmids profiles of Salmonella spp. in Nile perch of Lake Victoria, Tanzania.
Salmonella spp. and Escherichia coli in water and fish samples were investigated by the
bacteriological methods. Antimicrobial resistance profiles of Salmonella spp. were
determined using the minimum inhibitory concentration (MIC) method. A total of 324
samples were analysed including Nile perch, water and swabs from surfaces of facilities used
for fish transport. The finding showed the prevalence of Salmonella spp. in fish at fishing
ground were 16/60 (26.7%), landing sites and markets were 9/60 (15%) and 18/60 (30%)
respectively. A significant difference (p<0.05) was observed between the prevalence of
Salmonella spp. in fish from fishing ground and those at landing sites, but not with those
from markets (p>0.05). The main serotypes recovered were Salmonella ser. Waycross (41:
z4z23 :-) and Salmonella enterica ssp. salamae (42: r :-). Most Salmonella serotypes showed
the low resistance profiles against most of antimicrobials, but few isolates were resistant to
Nalidixic acid 3/64 (4.7%), ampicillin 5/64 (7.8%), azithromycin 14/64 (21.9%) and
sulfamethoxazole 22/64 (34.4%). Plasmids were detected in few Salmonella ser. Waycross
compared to none of Salmonella ssp. salamae. Escherichia coli count ranged 0.77 to 2.44
log 10 cfu/g in fish and 0.44 to 1.71 log 10 cfu/ml in water. Contaminated fish with different
Salmonella serovars imply pollution of the lake attributable to waste from point and nonpoint
sources that may contain antibiotic residues accounting for resistant bacteria in aquatic
environment. Un-hygienic fish handling and poor conditions of markets account for the high
prevalence of Salmonella spp. in Nile perch at markets.
