The primary goals of this cross-sectional study were to screen various food/water, and
human samples for the presence of Salmonella species, and to assess the phenotypic
and genetic relationship between resistances found in food and human Salmonella isolates to critically important antibiotics. Between November 2019 and May 2021, 501
samples were randomly collected for Salmonella isolation and identification using standard culturing methods, biochemical, matrix-assisted laser desorption ionization-time
of flight mass spectrometry (MALDI-TOF MS) and PCR techniques. Antimicrobial susceptibility testing was performed on confirmed Salmonella species, and PCR was used
to investigate the genetic components that confer these resistance traits. Salmonella
enterica subspecies enterica was confirmed in 35 (6.99%) of the samples (raw food = 23,
ready-to-eat food/drink [REF/D] = 5, human = 7). Seventeen of them were antibioticresistant to at least one class, and eight were multidrug-resistant (MDR) isolates (raw
food = 7, human = 1). All Salmonella isolates were susceptible to carbapenems, thirdand fourth-generation cephalosporins and monobactam antibiotics. Resistance phenotypes to aminoglycosides (48.57%), β-lactams (20%) and tetracycline (17.14%), as well
as associated genes such as aadA, blaTEM, blaZ and tetA, as well as dfrA and sul1, were
prevalent in Salmonella isolates. Colistin resistance genotype (mcr1) was detected in
three (8.57%) isolates recovered from egg, cattle mince and rabbit meat, and the total
incidence was 14.29% when two isolates exhibited resistance phenotypes were considered. Furthermore, four (11.43%) MDR isolates shared the blaTEM and blaZ genes,
and one (2.86%) isolate contained three extended spectrum β-lactams producing genes
(ESBL), namely blaCTX, blaTEM and blaZ. The gyrA gene was expressed by one of three
foodborne Salmonella isolates (8.57%) with ciprofloxacin resistance phenotypes. To the
best of our knowledge, this is the first report from Egypt identifying colistin resistance in Salmonella enterica recovered from cattle minced meat and rabbit meat. Overall, the highest incidence rate of Salmonella enterica was found in cattle-derived products, and it was slightly more prevalent in RTE/D foods than in raw foods. Resistance to
critical and clinically important antibiotics, particularly in Salmonella from RTE/D food,suggests that these antibiotics are being abused in the investigated area’s veterinary
field, and raises the potential of these isolates being transmitted to high-risk humans,
which would be a serious problem. Future research using whole-genome sequencing is
needed to clarify Salmonella resistance mechanisms to critically important antimicrobial agents or those exhibiting multidrug resistance.
|
