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Highest priority critically important antimicrobial-resistant Escherichia coli and Salmonella spp. isolated from pork and chicken meat from Argentina
* 1 , 1 , 1 , 2 , 1 , 1 , 3 , 4 , 1
1  Bacteriology and Antimicrobials Laboratory. Faculty of Veterinary Sciences. National University of La Plata
2  Immunoparasitology Laboratory. Faculty of Veterinary Sciences. National University of La Plata
3  Experimental Animal Laboratory.Faculty of Veterinary Sciences. National University of La Plata
4  IGEVET-Institute of Veterinary Genetics “Eng. Fernando N.Dulout” (UNLP-CONICET LA PLATA), Faculty of Veterinary Sciences UNLP, Buenos Aires, Argentina.
Academic Editor: Marc Maresca


Between June and September 2023, a total of 80 meat samples (48 and 32 from pork and
chicken, respectively) were collected from 16 retail markets in La Plata, Argentina.
Antimicrobial susceptibility was evaluated by agar diffusion, and PCR was used to identify
resistance genes. All markets were positive for at least one resistant E. coli. Eighty-four
resistant E. coli and two Salmonella spp. were isolated. Resistance to ciprofloxacin was
observed in 65 E. coli, 25 from pork, and 40 from chicken meat. Resistance to cefotaxime
was observed in 49 E. coli isolates, 14 from pork, and 35 from chicken meat. Seventy-five E.
coli isolates were multidrug resistant; twenty-four isolates showed resistance to four
antibiotic classes; and 20 strains were resistant to five antibiotic classes. Resistance was
most common to ampicillin (91.7%), tetracycline (78.6%), ciprofloxacin (77.4%), cefotaxime
(58.3%), chloramphenicol (48.8%), amoxicillin/clavulanic acid (47.6%), sulfamethoxazole-
trimethoprim (45.2%), fosfomycin (32.1%), gentamicin (22.6%), ceftazidime (8.3%), and
cefoxitin (4.8%). Fourteen E. coli isolated from chicken meat showed resistance to three of
the HPCIA cefotaxime/cefepime, ciprofloxacin, and fosfomycin. Resistance to 3rd and 4th
generation cephalosporin was associated with bla CTX-M genes; 12 E. coli were isolated from
pork and 33 from chicken meat. bla CTX-M alleles were grouped by specific PCR as follows: 1
bla CTX-M-1/15 ; 17 bla CTX-M-2 ; 5 bla CTX-M-9/14 ; and 5 bla CTX-M-8/25 . The results prove that the presence of resistant E. coli in pork and chicken meat can be a source of multiple resistance genes.

Keywords: E.coli, meat sample, antimicrobial-resistant, Argentina