EFFECT OF STRESSED ENVIRONMENTAL CONDITIONS ON THE VIABILITY OF ESCHERICHIA COLI AND ENTEROCOCCUS FAECAL/S
HABIBA MOSTAFA AHMED;
Abstract
Effect of stressed environmental conditions on the viability of Escl1ericl1ia coli and E11terococcus faeca/ls:
Coliform bacteria and fecal enterococci have been used as bioindicators for determination of the microbial quality of water or food stuffs. However, the stressed environmental conditions usually practised for water treatment or food processing, such as exposure to heating, freezing, high osmotic pressure, chemicals ... etc., leave some of surviving bacterial cells damaged. These injured cells arc still viable, though their recovery by normal enumeration procedures is negatively affected, due to their extended lag phase, long generation period and failure of growth on selective media. Therefore, bacterial populations may be seriously underestimated when a selective medium is used for the enumeration of specific bioindicators such as Eschen'chia coli and Enterococcus faecalis, causing an error in the interpretation of data and consequently health hazard. Thus, present standards and guidelines should be re-evaluated.
The aim of the present work is to study the effect of some stressed environmental conditions on the death and injury of two universal bioindicators; Escherichia coli and Enterococcus faecalis, and recovery of the injured cells by different methods.
The plan of study includes the following main topics:-
1. Determination of the lethality and i•tiury rates of E: coli and Enterococcus faeca/is exposed to different stressed conditions.
2. Effect of exposing E. coli and Entcrococcusjaecalis to sublethal stress on some metabolic nllributes.
Coliform bacteria and fecal enterococci have been used as bioindicators for determination of the microbial quality of water or food stuffs. However, the stressed environmental conditions usually practised for water treatment or food processing, such as exposure to heating, freezing, high osmotic pressure, chemicals ... etc., leave some of surviving bacterial cells damaged. These injured cells arc still viable, though their recovery by normal enumeration procedures is negatively affected, due to their extended lag phase, long generation period and failure of growth on selective media. Therefore, bacterial populations may be seriously underestimated when a selective medium is used for the enumeration of specific bioindicators such as Eschen'chia coli and Enterococcus faecalis, causing an error in the interpretation of data and consequently health hazard. Thus, present standards and guidelines should be re-evaluated.
The aim of the present work is to study the effect of some stressed environmental conditions on the death and injury of two universal bioindicators; Escherichia coli and Enterococcus faecalis, and recovery of the injured cells by different methods.
The plan of study includes the following main topics:-
1. Determination of the lethality and i•tiury rates of E: coli and Enterococcus faeca/is exposed to different stressed conditions.
2. Effect of exposing E. coli and Entcrococcusjaecalis to sublethal stress on some metabolic nllributes.
Other data
| Title | EFFECT OF STRESSED ENVIRONMENTAL CONDITIONS ON THE VIABILITY OF ESCHERICHIA COLI AND ENTEROCOCCUS FAECAL/S | Other Titles | تأثير الظروف البيئية الصعبة على حيوية بكتريا القولون والسبحيات المعوية | Authors | HABIBA MOSTAFA AHMED | Issue Date | 1997 |
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