Inactivation of Escherichia coli O157

H7 in biofilm on stainless steel by treatment with an alkaline cleaner and a bacteriophage

M. Sharma, Jee-Hoon Ryu, L. R. Beuchat

Research output: Contribution to journalArticle

83 Citations (Scopus)

Abstract

Aims: To determine the effectiveness of an alkaline cleaner used in food-processing plants and a lytic bacteriophage specific for Escherichia coli O157:H7 in killing wild type and rpoS-deficient cells of the pathogen in a biofilm. Methods and Results: Wild type and rpoS-deficient cells were attached to stainless steel coupons (c. 7-8 log CFU per coupon) on which biofilms were developed during incubation at 22°C for 96 h in M9 minimal salts media (MSM) with one transfer to fresh medium. Coupons were treated with 100 and 25% working concentrations of a commercial alkaline cleaner (pH 11.9, with 100 μg ml-1 free chlorine) used in the food industry, chlorine solutions (50 and 100 μg ml-1 free chlorine), or sterile deionized water (control) at 4°C for 1 and 3 min. Treatment with 100% alkaline cleaners reduced populations by 5-6 log CFU per coupon, a significant (P ≤ 0.05) reduction compared with treatment with water. Initial populations (2-6 log CFU per coupon) of attached cells of both strains were reduced by 1-2 log CFU per coupon when treated with bacteriophage KH1 (7.7 log PFU ml-1) for up to 4 days at 4°C. Biofilms containing low populations (2.7-2.8 log CFU per coupon) of wild type and rpoS-deficient cells that had developed for 24 h at 22°C were not decreased by more than 1 log CFU per coupon when treated with KH1 (7.5 log PFU ml-1) at 4°C. Conclusions: Higher numbers of cells of E. coli O157:H7 in biofilms are killed by treatment with an alkaline cleaner than with hypochlorite alone, possibly through a synergistic mechanism of alkaline pH and hypochlorite. Populations of cells attached on coupons were reduced by treating with bacteriophage but cells enmeshed in biofilms were protected. Significance and Impact of the Study: The alkaline pH, in combination with hypochlorite, in a commercial cleaner is responsible for killing E. coli O157:H7 in biofilms. Treatment with bacteriophage KH1 reduces populations of cells attached to coupon surfaces but not cells in biofilms.

Original languageEnglish
Pages (from-to)449-459
Number of pages11
JournalJournal of Applied Microbiology
Volume99
Issue number3
DOIs
Publication statusPublished - 2005 Sep 6
Externally publishedYes

Fingerprint

Escherichia coli O157
cleaners
Stainless Steel
stainless steel
Biofilms
bacteriophages
Bacteriophages
biofilm
inactivation
Hypochlorous Acid
hypochlorites
Chlorine
cells
chlorine
Population
Edible Plants
Food Handling
food processing plants
Water Purification
Food Industry

Keywords

  • Alkaline cleaner
  • Bacteriophage
  • Biofilm
  • Escherichia coli O157:H7
  • rpoS gene

ASJC Scopus subject areas

  • Agricultural and Biological Sciences(all)
  • Biotechnology
  • Applied Microbiology and Biotechnology
  • Microbiology

Cite this

Inactivation of Escherichia coli O157 : H7 in biofilm on stainless steel by treatment with an alkaline cleaner and a bacteriophage. / Sharma, M.; Ryu, Jee-Hoon; Beuchat, L. R.

In: Journal of Applied Microbiology, Vol. 99, No. 3, 06.09.2005, p. 449-459.

Research output: Contribution to journalArticle

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abstract = "Aims: To determine the effectiveness of an alkaline cleaner used in food-processing plants and a lytic bacteriophage specific for Escherichia coli O157:H7 in killing wild type and rpoS-deficient cells of the pathogen in a biofilm. Methods and Results: Wild type and rpoS-deficient cells were attached to stainless steel coupons (c. 7-8 log CFU per coupon) on which biofilms were developed during incubation at 22°C for 96 h in M9 minimal salts media (MSM) with one transfer to fresh medium. Coupons were treated with 100 and 25{\%} working concentrations of a commercial alkaline cleaner (pH 11.9, with 100 μg ml-1 free chlorine) used in the food industry, chlorine solutions (50 and 100 μg ml-1 free chlorine), or sterile deionized water (control) at 4°C for 1 and 3 min. Treatment with 100{\%} alkaline cleaners reduced populations by 5-6 log CFU per coupon, a significant (P ≤ 0.05) reduction compared with treatment with water. Initial populations (2-6 log CFU per coupon) of attached cells of both strains were reduced by 1-2 log CFU per coupon when treated with bacteriophage KH1 (7.7 log PFU ml-1) for up to 4 days at 4°C. Biofilms containing low populations (2.7-2.8 log CFU per coupon) of wild type and rpoS-deficient cells that had developed for 24 h at 22°C were not decreased by more than 1 log CFU per coupon when treated with KH1 (7.5 log PFU ml-1) at 4°C. Conclusions: Higher numbers of cells of E. coli O157:H7 in biofilms are killed by treatment with an alkaline cleaner than with hypochlorite alone, possibly through a synergistic mechanism of alkaline pH and hypochlorite. Populations of cells attached on coupons were reduced by treating with bacteriophage but cells enmeshed in biofilms were protected. Significance and Impact of the Study: The alkaline pH, in combination with hypochlorite, in a commercial cleaner is responsible for killing E. coli O157:H7 in biofilms. Treatment with bacteriophage KH1 reduces populations of cells attached to coupon surfaces but not cells in biofilms.",
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T2 - H7 in biofilm on stainless steel by treatment with an alkaline cleaner and a bacteriophage

AU - Sharma, M.

AU - Ryu, Jee-Hoon

AU - Beuchat, L. R.

PY - 2005/9/6

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N2 - Aims: To determine the effectiveness of an alkaline cleaner used in food-processing plants and a lytic bacteriophage specific for Escherichia coli O157:H7 in killing wild type and rpoS-deficient cells of the pathogen in a biofilm. Methods and Results: Wild type and rpoS-deficient cells were attached to stainless steel coupons (c. 7-8 log CFU per coupon) on which biofilms were developed during incubation at 22°C for 96 h in M9 minimal salts media (MSM) with one transfer to fresh medium. Coupons were treated with 100 and 25% working concentrations of a commercial alkaline cleaner (pH 11.9, with 100 μg ml-1 free chlorine) used in the food industry, chlorine solutions (50 and 100 μg ml-1 free chlorine), or sterile deionized water (control) at 4°C for 1 and 3 min. Treatment with 100% alkaline cleaners reduced populations by 5-6 log CFU per coupon, a significant (P ≤ 0.05) reduction compared with treatment with water. Initial populations (2-6 log CFU per coupon) of attached cells of both strains were reduced by 1-2 log CFU per coupon when treated with bacteriophage KH1 (7.7 log PFU ml-1) for up to 4 days at 4°C. Biofilms containing low populations (2.7-2.8 log CFU per coupon) of wild type and rpoS-deficient cells that had developed for 24 h at 22°C were not decreased by more than 1 log CFU per coupon when treated with KH1 (7.5 log PFU ml-1) at 4°C. Conclusions: Higher numbers of cells of E. coli O157:H7 in biofilms are killed by treatment with an alkaline cleaner than with hypochlorite alone, possibly through a synergistic mechanism of alkaline pH and hypochlorite. Populations of cells attached on coupons were reduced by treating with bacteriophage but cells enmeshed in biofilms were protected. Significance and Impact of the Study: The alkaline pH, in combination with hypochlorite, in a commercial cleaner is responsible for killing E. coli O157:H7 in biofilms. Treatment with bacteriophage KH1 reduces populations of cells attached to coupon surfaces but not cells in biofilms.

AB - Aims: To determine the effectiveness of an alkaline cleaner used in food-processing plants and a lytic bacteriophage specific for Escherichia coli O157:H7 in killing wild type and rpoS-deficient cells of the pathogen in a biofilm. Methods and Results: Wild type and rpoS-deficient cells were attached to stainless steel coupons (c. 7-8 log CFU per coupon) on which biofilms were developed during incubation at 22°C for 96 h in M9 minimal salts media (MSM) with one transfer to fresh medium. Coupons were treated with 100 and 25% working concentrations of a commercial alkaline cleaner (pH 11.9, with 100 μg ml-1 free chlorine) used in the food industry, chlorine solutions (50 and 100 μg ml-1 free chlorine), or sterile deionized water (control) at 4°C for 1 and 3 min. Treatment with 100% alkaline cleaners reduced populations by 5-6 log CFU per coupon, a significant (P ≤ 0.05) reduction compared with treatment with water. Initial populations (2-6 log CFU per coupon) of attached cells of both strains were reduced by 1-2 log CFU per coupon when treated with bacteriophage KH1 (7.7 log PFU ml-1) for up to 4 days at 4°C. Biofilms containing low populations (2.7-2.8 log CFU per coupon) of wild type and rpoS-deficient cells that had developed for 24 h at 22°C were not decreased by more than 1 log CFU per coupon when treated with KH1 (7.5 log PFU ml-1) at 4°C. Conclusions: Higher numbers of cells of E. coli O157:H7 in biofilms are killed by treatment with an alkaline cleaner than with hypochlorite alone, possibly through a synergistic mechanism of alkaline pH and hypochlorite. Populations of cells attached on coupons were reduced by treating with bacteriophage but cells enmeshed in biofilms were protected. Significance and Impact of the Study: The alkaline pH, in combination with hypochlorite, in a commercial cleaner is responsible for killing E. coli O157:H7 in biofilms. Treatment with bacteriophage KH1 reduces populations of cells attached to coupon surfaces but not cells in biofilms.

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