Identification and Antibiotic Resistance of Isolates from Poultry Meat and Poultry Meat By-Products Exhibiting Characteristic Salmonella Morphology on Chromogenic Agar

<b>Background/Objectives</b>: The main objective of this research work was to identify and determine the antibiotic resistance of the false-positive isolates on chromogenic agar when analyzing <i>Salmonella</i> in chicken meat. <b>Methods</b>: A total of 234 samples of chicken meat (carcasses, cuts and preparations) were studied using buffered peptone water for primary enrichment, Rappaport-Vassiliadis soy broth for secondary enrichment and <i>Salmonella</i> Chromogen Agar Set as a selective solid medium. Colonies with a morphology characteristic of <i>Salmonella</i> (one isolate per sample) were identified by matrix-assisted laser desorption ionization and time-of-flight mass spectrometry (MALDI-TOF). <b>Results</b>: Colonies with a characteristic morphology of <i>Salmonella</i> were detected in 71 samples. Only five isolates (7.0% of the total) corresponded to the genus <i>Salmonella</i>. Other genera detected were <i>Hafnia</i> (three isolates; 4.2% of the total), <i>Escherichia</i> (22; 31.0%), <i>Klebsiella</i> (19; 26.8%), <i>Proteus</i> (6; 8.5%) and <i>Pseudomonas</i> (16; 22.5%). The 66 isolates of these last five genera were tested for susceptibility to a panel of 42 antibiotics of clinical importance by disc diffusion. All isolates presented multiple resistances, to between 4 and 29 antibiotics, all of them having a multi drug-resistant (MDR) phenotype except for one <i>Pseudomonas</i> strain, with an extensively drug-resistant (XDR) phenotype. <b>Conclusions</b>: These results highlight the low selectivity of this method, with the specific culture media under test, for the detection of <i>Salmonella</i> in poultry meat. The considerable prevalence of antibiotic resistance observed suggests a need to improve control measures throughout the poultry meat production chain to prevent this food from becoming a reservoir of bacteria with resistance to multiple antibiotics.