Antibiotic resistance in foodborne pathogens. Teagasc Final Report Project RMIS No. 5036

https://arrow.tudublin.ie/cgi/viewcontent.cgi?article=1006&context=schfsehrep

Wide-spread antibiotic resistance among bacterial pathogens is now a serious
public health issue and multi-antibiotic resistance has been reported in many
foodborne pathogens including Salmonella and E. coli.
A study to determine antibiotic resistance profiles of a range of Salmonella and
Verocytotoxigenic E.coli (VTEC) isolated from Irish foods revealed significant
levels of antibiotic resistance in the strains. S. typhimurium DT104 were multi-
antibiotic resistant with 97% resistant to 7 antibiotics. S. Dublin and S. Agona
showed lower levels of antibiotic resistance.Antibiotic resistance among VTEC
isolates was generally low but two isolates of E. coli O157:H7 from minced
beef were shown to be multi-antibiotic resistant (8 to 10 antibiotics).
Studies to determine the relationship between antibiotic resistance and tolerance
to heat were conducted. The survival of Salmonella spp. with different antibiotic
profiles (antibiotic sensitive, laboratory-developed antibiotic resistant mutants or
multi-antibiotic resistant) on chicken heated to 55ºC with or without a prior heat
shock at 48ºC was established. The D value (time in minutes to achieve a 90%
or 1 log reduction in the Salmonella population) recorded for a multi-antibiotic
resistant S. Typhimurium DT104 was significantly higher (P<0.05) than for all
other strains tested (antibiotic sensitive or with laboratory-acquired antibiotic
resistance). These results suggest that the presence of multi-antibiotic resistance
genes increased the heat tolerance of Salmonella.
The survival of VTEC, E. coli O157:H7 and E. coli O26 (antibiotic sensitive,
laboratory-developed antibiotic resistant mutants or multi-antibiotic
resistant) in minced beef heated to 55ºC with or without a prior heat shock
at 48ºC was established. The D value recorded for multi-antibiotic resistant E.
coli O157:H7 was significantly lower than for the other strains tested. These
results indicate that the presence of multi-antibiotic resistant genes rendered
the pathogens more sensitive to heat.
Studies to determine whether antibiotic resistance could be transferred within
species (Salmonella Typhimurium to Salmonella Agona) and between species
1
(Salmonella to E. coli) when co-inoculated into laboratory media, milk or minced
beef at different storage temperatures (37, 25, 15 and 4ºC) showed that horizontal
antibiotic resistance gene transfer occurred in all substrates at temperatures of 37
and 25ºC. At 15ºC, transfer of resistance occurred only in minced meat. Similar
results were reported for transfer of antibiotic resistance both within the
Salmonella spp. and between different species (Salmonella to E. coli).