Bacterial species
A total of 1,829 Staphylococcus spp., Enterobacteriaceae, and Enterococcus spp. isolates were recovered (281 from stray cats, 978 from hospital-admitted cats, and 570 from veterinary staff). Table 1 shows the bacterial species isolated based on their origin (stray cats, hospital visiting cats, and veterinary staff). The most frequently isolated pathogens were E. coli in case of stray cats and hospital-admitted cats (n=31, 11% and n=161, 16.5%, respectively) and S. epidermidis in case of the veterinary staff (n=89, 15.6%). Coagulase-negative Staphylococci (CNS) were isolated at a significantly higher (P < 0.05) rate from stray cats (64/78, 82.1%) than from hospital-admitted cats (230/350, 65.7%) and veterinary staff (160/294, 54.4%). Among the staphylococcal isolates, S. felis was isolated at a significantly higher frequency (P < 0.05) from stray cats and hospital-admitted cats (29/74, 39.2% and 60/264, 22.7%, respectively) than from veterinary staff (6/176, 3.4%). On the contrary, the isolation frequency of S. epidermidis from veterinary staff (89/176, 50.6%) was significantly higher (P < 0.05) than that from stray cats (6/74, 8.1%) and hospital-admitted cats (39/264, 14.8%).
Antimicrobial susceptibility of Staphylococcus spp.
In case of the isolates of CNS from stray cats, the rates of resistance to ampicillin, penicillin, and oxacillin varied between 20 and 34%, and the rates of resistance to amox/clav, gentamicin, and tetracycline were 6–9%. Resistance to clindamycin, enrofloxacin, marbofloxacin, and chloramphenicol was absent or low (0–3%) (Table 3 and Fig. S1). For cephalexin, no CLSI breakpoints are available. The number of isolates of Coagulase-positive Staphylococci (CPS) from stray cats was too small; hence, the resistance rates of these isolates is not being presented.
More than half of the isolates of CPS from hospital-admitted cats showed resistance to ampicillin, penicillin, and amox/clav (59–82%) (Table 2 and Fig. S1). The rates of resistance to oxacillin, enrofloxacin, marbofloxacin, and tetracycline varied between 12 and 29%, and the rates of resistance to gentamicin, clindamycin, and chloramphenicol were lower (6–9%). For the isolates of CNS from hospital-admitted cats, the rates of resistance to ampicillin, penicillin, and oxacillin were between 35 and 60%, and the rates of resistance to amox/clav, gentamicin, and tetracycline were 11–24% (Table 3 and Fig. S1). The rates of resistance to clindamycin, enrofloxacin, marbofloxacin, and chloramphenicol were low (4–7%) (Table 3 and Fig. S1). In case of cephalexin, for which no breakpoints were available, the MIC distributions suggest the presence of acquired resistance for some isolates. The rates of resistance to ampicillin, penicillin, and tetracycline for isolates from hospital-admitted cats were significantly higher (P < 0.05) than those for the isolates from stray cats.
In case of the CNS isolates from the veterinary staff, the rates of resistance to ampicillin, penicillin, oxacillin, and tetracycline varied between 59 and 80%, and the rates of resistance to amox/clav and gentamicin were 38%. The rates of resistance to clindamycin, enrofloxacin, marbofloxacin, and chloramphenicol was low (3–11%) (Table 3 and Fig. S1). In case of cephalexin, for which no breakpoints were available, the MIC distributions suggest the presence of acquired resistance for some isolates, like the case for the isolates of CPS from the hospital-admitted cats. The rates of resistance to ampicillin, penicillin, oxacillin, amox/clav, gentamicin, enrofloxacin, marbofloxacin, and tetracycline for isolates from the veterinary staff were significantly higher (P < 0.05) than those for the isolates from stray cats or hospital-admitted cats.
Antimicrobial susceptibility of Enterobacteriaceae
For Enterobacteriaceae isolates from stray cats, resistance to ceftiofur, ceftriaxone, gentamicin, imipenem, meropenem, enrofloxacin, marbofloxacin, and tetracycline was absent or low (0–5%). The rate of resistance to cefoxitin was shown to be 13%. The rates of resistance to ampicillin, amox/clav, and cephalothin varied between 72 and 100% (Table 4 and Fig. S1).
For Enterobacteriaceae isolates from hospital-admitted cats, resistance to gentamicin, imipenem, meropenem, enrofloxacin, and marbofloxacin was absent or low (0–6%). The rates of resistance to cefoxitin, ceftiofur, ceftriaxone, and tetracycline ranged from 10 to 22%. The rates of resistance to ampicillin, amox/clav, and cephalothin varied between 76 and 99% (Table 4 and Fig. S1). Tetracycline resistance in isolates from hospital-admitted cats was significantly higher (P < 0.05) than that in isolates from stray cats.
For Enterobacteriaceae isolates from veterinary staff, resistance to ceftiofur, ceftriaxone, gentamicin, imipenem, meropenem, enrofloxacin, and marbofloxacin was absent or low (0–8%). The rates of resistance to cefoxitin and tetracycline were between 36 and 44%, and were significantly higher (P < 0.05) than those of isolates from stray cats or hospital-admitted cats. The rates of resistance to ampicillin, amox/clav, and cephalothin varied between 88–98% (Table 4 and Fig. S1).
Antimicrobial susceptibility of Enterococcus spp.
For Enterococcus spp. isolates from stray cats, rates of resistance to erythromycin, tetracycline, and minocycline were between 51 and 68%; however, resistance to ampicillin, vancomycin and high levels of resistance to streptomycin was absent or low (0–9%) (Table 5 and Fig. S1). The rates of resistance to penicillin, chloramphenicol, and ciprofloxacin, and high levels of resistance to gentamicin were between 16 and 21%.
For Enterococcus spp. from hospital-admitted cats, rates of resistance to erythromycin, tetracycline, and minocycline were between 39 and 62%; however, resistance to vancomycin and high levels of resistance to streptomycin were absent or low (0–9%) (Table 5 and Fig. S1). The rates of resistance to ampicillin, penicillin, chloramphenicol, and ciprofloxacin, and high levels of resistance to gentamicin were between 11 and 20%.
For Enterococcus spp. from veterinary staff, rates of resistance to erythromycin, tetracycline, and minocycline were between 25 and 50%; however, resistance to ampicillin, penicillin, vancomycin, chloramphenicol, ciprofloxacin and high levels of resistance to both streptomycin and gentamicin were absent or low (0–10%) (Table 5 and Fig. S1).
mecA gene detection
In total, 110 (21.4%) Staphylococcus spp. isolates harbored the mecA gene: 7 (9.5%) from stray cats, 32 (12.1%) from hospital-admitted cats, and 71 (40.3%) from veterinary staff. The rates of mecA among the staphylococcal isolates from the veterinary staff were higher than those among the staphylococcal isolates from the stray cats or hospital-admitted cats (P < 0.05). S. epidermidis was the most prevalent bacterium among the isolates from both the hospital-admitted cats and veterinary staff (15/46.9% and 53/74.7%, respectively) (data not shown). The oxacillin-resistance rates among the isolates of CNS were higher than those among the isolates of CPS from the hospital-admitted cats and veterinary staff (P < 0.05). Generally, the susceptibility ranges of the mecA-containing staphylococci isolated from the stray cats, hospital-admitted cats, and veterinary staff were similar. The rates of resistance to ampicillin and penicillin were between 84.4 and 98.6%, and the rates of resistance to amox/clav, gentamicin, and tetracycline were between 28.6 and 88.7%. Resistance to clindamycin, enrofloxacin, marbofloxacin, and chloramphenicol was absent or low (0–15.5 %) (Table 6).
Extended spectrum β-lactamases (ESBL) and carbapenemase detection
Among the 278 Enterobacteriaceae isolates, 1 K. pneumoniae isolate from a stray cat and 1 K. pneumoniae, 1 Enterobacter asburiae, 1 Enterobacter cloacae, and 11 E. coli isolates from hospital-admitted cats fulfilled the selection criteria for being termed as ESBL-producing bacteria. Among them, five E. coli isolates from hospital-admitted cats were confirmed to possess both blaTEM and blaCTX-M, while one K. pneumoniae isolate from a stray cat and one K. pneumoniae isolate from a hospital-admitted cat possessed only blaTEM. None of the isolates possessed blaSHV. A total of eight isolates that satisfied the ESBL-producing bacteria selection criteria were negative for all resistance genes tested.
None of the Enterobacteriaceae isolates that were not susceptible to imipenem or meropenem showed enhanced growth in the modified Hodge test.
Phenotypic resistance patterns derived from human clinical breakpoints
Overall, 15% (9/60) of the isolates of CPS, 25.3% (115/454) of the isolates of CNS, 48.6% (135/278) of the Enterobacteriaceae isolates, and 27.9% (63/226) of the Enterococcus spp. isolates were susceptible to all antimicrobial agents tested. Additionally, 30% (18/60) of the isolates of CPS, 33% (150/454) of the isolates of CNS, 25.5% (71/278) of the Enterobacteriaceae isolates, and 29.2% (66/226) of the Enterococcus spp. isolates showed MDR. The MDR rates of the isolates of CNS obtained from the veterinary staff (92/160, 57.5%) were significantly higher (P < 0.05) than those of the isolates of CNS obtained from the stray cats (7/64, 10.9%) or hospital-admitted cats (51/230, 22.2%) (Table 7). The MDR rates of the isolates of CNS obtained from the hospital-admitted cats were also significantly higher (P < 0.05) than those of the isolates of CNS obtained from the stray cats. The MDR rates of Enterobacteriaceae isolates obtained from veterinary staff (22/50, 44%) were significantly higher (P < 0.05) than those of Enterobacteriaceae isolates obtained from the stray cats (4/39, 10.3%) or hospital-admitted cats (45/189, 23.8%) (Table 8). On the contrary, the MDR rates of Enterococcus spp. isolates obtained from the veterinary staff (1/20, 5.0%) were significantly lower (P < 0.05) than those of Enterococcus spp. isolates obtained from the stray cats (18/57, 31.6%) or hospital-admitted cats (47/149, 31.5%) (Table 9).
The most common resistance profile among the CNS isolates was BLA-OXA, which was detected in 57 isolates of CNS, while the most common MDR profile was AMG-BLA-BLI-OXA-TET, which was observed in 4 isolates of CNS obtained from the hospital-admitted cats and 24 isolates of CNS obtained from the veterinary staff. Among the Enterobacteriaceae isolates, the most common resistance profile was BLA-BLI-GC, which was detected in 1 isolates of Enterobacteriaceae obtained from the stray cats, 11 isolates from hospital-admitted cats, and 9 isolates from the veterinary staff. In the Enterococcus spp. isolates, the most common resistance profile was MAC-TET, which was detected in 29 isolates of Enterococcus spp., while the most common MDR profile was MAC-PNC-TET, which was observed in 5 isolates of Enterococcus spp. obtained from the stray cats, and 8 isolates from the hospital-admitted cats.