Although normally regarded harmless commensals, enterococci may cause a range of
different infections in humans, including urinary tract infections, sepsis, and endocarditis.
The acquisition of vancomycin resistance by enterococci (VRE) has seriously affected
the treatment and infection control of these organisms. VRE are frequently resistant
to all antibiotics that are effective treatment for vancomycin-susceptible enterococci,
which leaves clinicians treating VRE infections with limited therapeutic options. With VRE
emerging as a global threat to public health, we aimed to isolate, identify enterococci
species from tilapia and their resistance to van-mediated glycopeptide (vanA and
vanC) as well as the presence of enterococcal surface protein (esp) using conventional
and molecular methods. The cultural, biochemical (Vitek 2 system) and polymerase
chain reaction results revealed eight Enterococcus isolates from the 80 fish samples
(10%) to be further identified as E. faecalis (6/8, 75%) and E gallinarum (2/8, 25%).
Intraperitoneal injection of healthy Nile tilapia with the eight Enterococcus isolates
caused significant morbidity (70%) within 3 days and 100% mortality at 6 days postinjection
with general signs of septicemia. All of the eight Enterococcus isolates were
found to be resistant to tetracycline. The 6/6 E. faecalis isolates were susceptible for
penicillin, nitrofurantoin, gentamicin, and streptomycin. On the other hand 5/6 were
susceptible for ampicillin, vancomycin, chloramphenicol, and ciprofloxacin. The two
isolates of E. gallinarum were sensitive to rifampicin and ciprofloxacin and resistant
to vancomycin, chloramphenicol, and erythromycin. Molecular characterization proved
that they all presented the prototypic vanC element. On the whole, one of the two
vancomycin resistance gene was present in 3/8 of the enterococci isolates, while
the esp virulence gene was present in 1/8 of the enterococci isolates. The results
in this study emphasize the potential role that aquatic environments are correlated to
proximity to anthropogenic activities in determining the antimicrobial resistance patterns
of Enterococcus spp. recovered from fish in the river Nile in Giza, Elmounib, Egypt
as a continuation of our larger study on the reservoirs of antibiotic resistance in the
environment. |
