Determine the disinfectant (biocide) and antibiotic susceptibility profiles of 363 E. coli O157:H7 cattle feces, hide, carcass, and ground meat isolates from different parts of the United States, and statistically correlate this data with the PCR detection of the quaternary ammonium chloride resistance genes, incompatibility typing method, and PFGE analysis to describe these pathogenic bacteria.
Approach: The antimicrobial and disinfectant resistant profiles of a representative sampling of E. coli O157:H7 isolates from cattle will be defined by disinfectant and antibiotic susceptibility testing, by PCR testing, and by PFGE analysis. Minimum efficacious dose concentrations of commonly used disinfectants will be determined. <P>
The disinfectant and antibiotic susceptibility profiles of 344 E. coli O157:H7 cattle feces,
hide, carcass, and ground meat isolates from different parts of the United States were
determined. A low incidence of antibiotic resistance was observed (14%, Table 1). The highest
incidence of resistance was observed to FIS (10.5%), TET (9.9%), STR (7%), and CHL (4.9%).
Two ground meat, one cull cow hide and previseration isolate were resistant to 8 antibiotics.
Table 2 shows the overall disinfectant MICs. There were 69 (20%) of the isolates resistant to
chlorhexidine, benzalkonium chloride, or had elevated MICs to
benzyldimethyldodecylammonium chloride. All isolates were pansusceptible to triclosan. All
344 isolates were positive for the sugE gene, and sugE did not appear to correlate with the
quarternary ammonium chlorides tested. There was spontaneous resistance (SR) at elevated
levels of antibiotics (1.4%) and disinfectants (6.1%). The highest rate of SR was observed in
OdoBan, ammonium chloride components, and the surface disinfectants F25, FS512, and MG
used in dairies, restaurants, and food processing plants. SR could allow the presence of bacteria
where they should have been removed by disinfection. High MICs (1024ï¿½4096 µg/mL) were
found for the acids, acetic, lactic, and citric. The decreasing order of acid potency based on
was acetic, citric, and lactic acid. PFGE analysis was performed using XbaI digests of
the E. coli O157:H7, and clusters 1A, 1B, 1C, and 1H were associated with high multi-drug
resistance (MDR), but little disinfectant resistance. PFGE cluster 1C was associated with
resistance to 8 antibiotics in two ground meat isolates. Similar resistance traits were observed in
a cull cow hide and previseration isolate with PFGE cluster designation 1H. There was no correlation between disinfectant resistance and antibiotic resistance in the E. coli O157:H7
isolates tested. <P>