Enhancing the antimicrobial effects of bovine lactoferrin against Escherichia coli O157:H7 by cation chelation, NaCl and temperature.
OBJECTIVE
To evaluate the effect of NaCl, growth medium and temperature on the antimicrobial activity of bovine lactoferrin (LF) against Escherichia coli O157:H7 in the presence of different chelating agents.


RESULTS
LF (32 mg ml(-1)) was tested against E. coli O157:H7 strain 3081 in Luria broth (LB) and All Purpose Tween (APT) broth with metal ion chelators sodium bicarbonate (SB), sodium lactate (SL), sodium hexametaphosphate (SHMP), ethylene diamine tetraacetic acid (EDTA) or quercetin at 0.5 and 2.5% NaCl at 10 and 37 degrees C. LF and the chelators were tested against four other E. coli O157:H7 strains in LB at 2.5% NaCl and 10 degrees C. LF alone was bacteriostatic against strains 3081 and LCDC 7283 but other strains grew. Antimicrobial effectiveness of LF was reduced in APT broth but enhanced by SB at 2.5% NaCl and 10 degrees C where 4.0 log(10) CFU ml(-1) inoculated cells were killed. EDTA enhanced antimicrobial action of the LF-SB combination. SL alone was effective against E. coli O157:H7 but a reduction in its activity at 2.5% NaCl and 10 degrees C was reversed by LF. The combinations LF-SHMP and LF-quercetin were more effective at 37 degrees C and NaCl effects varied.


CONCLUSIONS
LF plus SB or SL were bactericidal toward the same 3/5 E. coli O157:H7 strains and inhibited growth of the others at 2.5% NaCl and 10 degrees C.


CONCLUSIONS
The combination of LF with either SL or SB shows potential for reducing viability of E. coli O157:H7 in food systems containing NaCl at reduced, but growth permissive temperature.
Al-Nabulsi
A A
AA
Department of Food Science, University of Manitoba, Winnipeg, Manitoba, Canada.
Holley
R A
RA
D000818:Animals; D000975:Antioxidants / Q000494:pharmacology; D002417:Cattle; D002614:Chelating Agents / Q000494:pharmacology*; D015169:Colony Count, Microbial; D003470:Culture Media; D004492:Edetic Acid / Q000494:pharmacology; D019453:Escherichia coli O157 / Q000187:drug effects*; D005516:Food Microbiology; D005519:Food Preservation / Q000379:methods; D006863:Hydrogen-Ion Concentration; D007781:Lactoferrin / Q000494:pharmacology*; D010710:Phosphates / Q000494:pharmacology; D011794:Quercetin / Q000494:pharmacology; D017693:Sodium Bicarbonate / Q000494:pharmacology; D012965:Sodium Chloride / Q000494:pharmacology*; D019354:Sodium Lactate / Q000494:pharmacology; D013696:Temperature
D000975:Antioxidants; D002614:Chelating Agents; D003470:Culture Media; D010710:Phosphates; D012965:Sodium Chloride; D017693:Sodium Bicarbonate; D004492:Edetic Acid; D011794:Quercetin; D007781:Lactoferrin; C009285:sodium polymetaphosphate; D019354:Sodium Lactate