Characterization of multidrug-resistant strains
Multidrug-resistant strains accounted for 71.4% of all the different
isolated E. coli strains. Ampicillin resistance was observed in
95.7% of the isolates; however, eight strains were classified as
intermediate. Only three strains isolated from the rats were found to be
susceptible to this antibiotic. More than half of the isolates showed
resistance to tetracycline (64.3%) or streptomycin (51.4%). We also
found that 45.7% of the isolates were resistant to sulfamethoxazole.
Kanamycin resistance was observed in 19 strains, and only one strain was
resistant to gentamicin (from the squirrel). In total, 38.6% of the
isolates had a chloramphenicol resistant profile, but eight of them were
classified as intermediately resistant. Nitrofurantoin resistance was
noted in 31.4% of the strains, but most (n=16) were intermediately
resistant isolates. The nalidixic acid-resistant isolates accounted for
24.3%, and those with resistance to ciprofloxacin represented 12.9%
(Table S3; Fig. 1).
Among isolates obtained from the squirrels, 70.8% of the strains (n=17)
had a multidrug-resistant profile. In this group of samples, we also
detected one E. coli ESBL producer. In addition to resistance to
ampicillin and tetracycline, a high proportion (from 37.5 to 45.8%) of
strains resistant to sulfamethoxazole, chloramphenicol, nalidixic acid,
and streptomycin were observed as well.
The multidrug-resistant profile in samples isolated from the rats was
observed in 57.1% of the strains. High aminoglycoside resistance was
noted, i.e. 35.7% for streptomycin and 42.9% for kanamycin. Almost
half of the strains were resistant to nitrofurantoin. Resistance to
tetracycline and sulfamethoxazole remained at a high level, as in the
case of isolates obtained from the squirrels.
All E. coli strains isolated from the hedgehogs showed a
multidrug-resistant profile. In this group, the highest resistance was
observed for ampicillin (100%) and nitrofurantoin (75%). Moreover,
half of the strains were resistant to tetracycline and/or
sulfamethoxazole.
The isolates obtained from the ungulates were characterized by high
resistance to ampicillin, streptomycin, sulfamethoxazole, and
tetracycline. All E. coli strains isolated from roe deer had a
multidrug-resistance profile and resistance to five groups of
antimicrobials predominated. However, in the case of the red-deer
isolates, 53.3% (n=8) showed multidrug resistance. Similarly, the
analysis of the diversity of resistance depending on the source of the
strain (host species) showed statistically significantly higher
resistance to tetracycline, streptomycin, sulphametoxazole, and
ciprofloxacin among strains isolated from the roe deer. Statistically,
resistance to chloramphenicol, kanamycin, nalidixic acid, and
nitrofurantoin was most frequently reported in the isolates from the red
deer, rats, squirrels, and hedgehog, respectively (Fig 1).
We also examined the single strain obtained from the beaver. It showed a
multidrug-resistance profile as well (Table 1).