Little work has been reported on the use of commercial antimicrobials against foodborne pathogens on duck meat. We investigated the effectiveness of trisodium phosphate (TSP) and sodium hypochlorite (SH) as antimicrobial treatments against Campylobacter and Salmonella on duck meat under simulated commercial water chilling conditions. The results were compared to the same treatments on well-studied chicken meat. A six strain Campylobacter or Salmonella cocktail was inoculated (5 ml) at two dilution levels (10(4) and 10(8) cfu/ml) onto 25 g duck or chicken meat with skin and allowed to attach for 10 min. The meat was exposed to three concentrations of pH adjusted TSP (8, 10 and 12% (w/v), pH 11.5) or SH (40, 50 and 60 ppm, pH 5.5) in 30 ml water under simulated spin chiller conditions (4 °C, agitation) for 10 min. In a parallel experiment the meat was placed in the antimicrobial treatments before inoculation and bacterial cocktails were added to the meat after the antimicrobial solution was removed while all other parameters were maintained. Untreated controls and controls using water were included in all experiments. Bacterial numbers were determined on Campylobacter blood-free selective agar and Mueller Hinton agar or xylose deoxycholate agar and tryptone soya agar using the thin agar layer method for Campylobacter and Salmonella, respectively. All TSP concentrations significantly (p<0.05) reduced numbers of Campylobacter (~1.2-6.4 log cfu/cm(2)) and Salmonella (~0.4-6.6 log cfu/cm(2)) on both duck and chicken meat. On duck meat, numbers of Campylobacter were less than the limit of detection at higher concentrations of TSP and numbers of Salmonella were less than the limit of detection at all concentrations of TSP except one. On chicken meat, numbers of Campylobacter and Salmonella were less than the limit of detection only at the lower inoculum level and higher TSP concentrations. By contrast only some of the concentrations of SH significantly (p<0.05) reduced numbers of Campylobacter and Salmonella (~0.2-1.5 log cfu/cm(2)) on both duck and chicken meats. None of the SH treatments resulted in numbers of either pathogen being less than limit of detection. Results indicate that chicken meat has the ability to effectively protect Campylobacter and Salmonella against the impact of trisodium phosphate and sodium hypochlorite while duck meat does not. This study suggests that trisodium phosphate has a strong potential for application in a commercial poultry processing to reduce Campylobacter and Salmonella specifically on duck meat.
Thermophilic Campylobacter and Salmonella enterica are major causes of gastrointestinal foodborne infection. Survival of these pathogens on food-associated surfaces is a risk contributing to their spread through the food system. This study examined the transfer of two strains each of C. jejuni, C. coli, Salmonella Enteritidis, and Salmonella Typhimurium from chicken meat to a knife or scissors used on either a plastic or wooden cutting board. Each strain of Campylobacter and Salmonella at ∼108 CFU mL-1 was inoculated (5 mL) onto 25 g of chicken meat with skin and allowed to attach (for 10 min). The meat was then cut (20 times per implement) into 1-cm2 pieces with either a knife or scissors on either a plastic or wooden cutting board. The numbers of pathogens transferred from meat onto cutting implements and cutting board surfaces were enumerated. The surfaces were subsequently either rinsed with water or rinsed with water and wiped with a kitchen towel to mimic commonly used superficial cleaning practices for these implements, and the numbers of pathogens were enumerated again. The bacterial numbers for both pathogens were determined on thin-layer agar. The attachment of the Salmonella strains to chicken meat (∼7.0 to 7.8 log CFU cm-2) was higher than the attachment of the Campylobacter strains (∼4.6 to 6.6 log CFU cm-2). All four Salmonella strains transferred in higher numbers (∼1.9 to 6.3 log CFU cm-2) to all surfaces than did the Campylobacter strains (∼1.1 to 3.9 log CFU cm-2). The transfer rates of both pathogens from the chicken meat to all the surfaces examined varied substantially between ∼0 and 21.1%. The highest rate of transfer (∼21.1%) observed was for C. coli 2875 when transferred from the chicken meat to the scissors. Most cleaning treatments reduced the numbers of both pathogens (∼0.3 to 4.1 log CFU cm-2) transferred to all the surfaces. Our study gives insights into the risks associated with the transfer of Campylobacter and Salmonella from poultry to the surfaces used in poultry preparation.
Gallic acid has been suggested as a potential antimicrobial for the control of Campylobacter but its effectiveness is poorly studied. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of gallic acid against Campylobacter jejuni (n = 8) and Campylobacter coli (n = 4) strains was determined. Gallic acid inhibited the growth of five C. jejuni strains and three C. coli strains (MIC: 15.63-250 μg mL(-1)). Gallic acid was only bactericidal to two C. coli strains (MBC: 125 and 62.5 μg mL(-1)). The mechanism of the bactericidal effect against these two strains (and selected non-susceptible controls) was investigated by determining decimal reduction times and by monitoring the loss of cellular content and calcium ions, and changes in cell morphology. Gallic acid did not result in a loss of cellular content or morphological changes in the susceptible strains as compared to the controls. Gallic acid resulted in a loss of calcium ions (0.58-1.53 μg mL(-1) and 0.54-1.17 μg mL(-1), respectively, over a 180 min period) from the susceptible strains but not the controls. Gallic acid is unlikely to be an effective antimicrobial against Campylobacter in a practical sense unless further interventions to ensure an effective bactericidal mode of action against all strains are developed.