Pressure resistance of cold-shocked Escherichia coli O157:H7 in ground beef, beef gravy and peptone water.

Abstract

AIMS:

(i) To study the effects of cold shock on Escherichia coli O157:H7 cells. (ii) To determine if cold-shocked E. coli O157:H7 cells at stationary and exponential phases are more pressure-resistant than their non-cold-shocked counterparts. (iii) To investigate the baro-protective role of growth media (0·1% peptone water, beef gravy and ground beef).

METHODS AND RESULTS:

Quantitative estimates of lethality and sublethal injury were made using the differential plating method. There were no significant differences (P > 0·05) in the number of cells killed; cold-shocked or non-cold-shocked. Cells grown in ground beef (stationary and exponential phases) experienced lowest death compared with peptone water and beef gravy. Cold-shock treatment increased the sublethal injury to cells cultured in peptone water (stationary and exponential phases) and ground beef (exponential phase), but decreased the sublethal injury to cells in beef gravy (stationary phase).

CONCLUSIONS:

Cold shock did not confer greater resistance to stationary or exponential phase cells pressurized in peptone water, beef gravy or ground beef. Ground beef had the greatest baro-protective effect.

SIGNIFICANCE AND IMPACT OF THE STUDY:

Real food systems should be used in establishing food safety parameters for high-pressure treatments; micro-organisms are less resistant in model food systems, the use of which may underestimate the organisms' resistance.

• Authors: G S H Baccus-Taylor, O C Falloon, N Henry
• Journal: Journal of applied microbiology (J Appl Microbiol) Vol. 118 Issue 6 Pg. 1521-9 (Jun 2015) ISSN: 1365-2672 [Electronic] England
• PMID: 25766637 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: © 2015 The Society for Applied Microbiology.

Chemical References

• Culture Media
• Peptones

Topics

• Animals
• Cattle
• Cold Temperature
• Colony Count, Microbial
• Culture Media (pharmacology)
• Escherichia coli O157 (chemistry, classification, genetics, growth & development, isolation & purification)
• Food Contamination (analysis)
• Fresh Water (microbiology)
• Meat (microbiology)
• Meat Products (microbiology)
• Peptones (analysis)
• Pressure
• Time Factors