Bioassay activity of crude bacteriocin produced by Lactobacillus acidophilus isolate against cold stressed E.coli O157:H7

The laboratory studies of the cultural isolation revealed that two isolates of Lactobacillus acidophilus were isolated from five soft cheese samples that were manufactured locally according to the farmers production procedure .Colonies of E.coli O157:H7 were isolated from raw milk samples by a conventional direct plating on selective enrichment CT-SMAC agar and tested serologically for the presence of O157 and H7 antigens using the commercial available latex agglutination kits .The results revealed that E.coli O157:H7 was resist to the crude bacteriocin that was extracted from L .acidophilus isolate NO.1 due to the nature of their cell wall, while when the outer membrane of E.coli O157:H7 was injured by cooling at 4°C for 6 hours , the permeation of bacteriocin to the cytoplasmic membrane was facilitated and caused inactivation and death of such pathogenic organism .The results revealed that no growth of E.coli O157:H7 with no visible turbidity in the nutrient broth with bacteriocin that diluted to 1\2 ,1\4 ,1\8 were observed .Bacteriocin that diluted to 1\8 had been recognized as the minimum inhibitory concentration of the bacteriocin.Both the dilution factor of bacteriocin and time exposure to bacteriocin at refrigeration storage temperature of milk had a significant (P˂0.05) influence on its antimicrobial potency against the viability of stressed E.coli O157:H7 from minutes 30 to 120 .The viability of E.coli O157:H7 subjected to bacteriocin that diluted 10 times(1:10) in both raw and sterile milk was efficiently eliminated after 90 minutes and 60 minutes of exposure at refrigeration temperature respectively.

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The combined effect of bacteriocin-producing Lactobacillus rhamnosus GG-ATCC and Lactoperoxidase system activation on microbiological quality of raw milk with special emphasis against E.coli O157:H7 in milk

The Iraqi Journal of Veterinary Medicine ◽

10.30539/iraqijvm.v40i2.114 ◽

2017 ◽

Vol 40 (2) ◽

pp. 66-72

Author(s):

Najim Hadi Najim

Keyword(s):

Storage Temperature ◽

Lactobacillus Rhamnosus ◽

Microbiological Quality ◽

Raw Milk ◽

Latex Agglutination ◽

Bacterial Cells ◽

Lactobacillus Rhamnosus Gg ◽

Time Period ◽

Soft Cheese ◽

Chromogenic Agar

Isolates of Enterohaemorrhagic E.coli O157:H7 were isolated from 51 and 41 of locally produced bovine and ovine soft cheese samples. Their identification were confirmed based on the biochemical reactions and both the morphological cultural and serological properties. Presumptive E.coli O157:H7 isolates obtained by using the conventional selective plating on the chromogenic agar were tested further for the presence of both O157 and H7 antigenes using the latex agglutination test antisera. The current microbiological studies revealed that 31 (33.70 %) out of 92 bovine and ovine soft cheese samples were positive for E.coli O157:H7. The highest non significant (P>0.05) prevalence level of E.coli O157:H7 was found in the ewe᾿s soft cheese samples (36.59 %) followed by cow᾿s soft cheese samples (31.37 %). Agar well diffusion bioassay method was used for measuring the antibacterial activity of the crude bacteriocin that was produced by Lactobacillus rhamnosus GG-ATCC against Escherichia coli and the closely related sensitive strains such as L.acidophilus LA-K and L.acidophilus ROO52. The crude bacteriocin that was produced by the L.rhamnosus GG-TACC exhibited significantly (P<0.05) the highest antibacterial potency (100 %) against both the closely related strains of lactobacilli and the stressed E.coli O157:H7 by the activation of the LPS. The activation of the natural LPS of inoculated pasteurized milk had significantly (P<0.05) influenced the inactivation degree of the crude bacteriocin against E.coli O157:H7. There was a significant (P<0.05) reduction in the viable counts of stressed E.coli O157:H7 after each exposure time period (6, 24 and 48 hrs.) to the crude bacteriocin at room storage temperature. An overall conclusion on the basis of the current results pointed out that complete elimination of viable bacterial cells was not achieved neither in the stabilized milk (Activation of LPS) nor after subjecting the stabilized milk to the action of the crude bacteriocin produced by L.rhamnosus GG-ATCC at room storage temperature.

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The synergistic effects of Lactobacillus acidophillus ROO52 and Lactobacillus bulgaricus LB-12 bacteriocins against E.coli O157 :H7 in milk

The Iraqi Journal of Veterinary Medicine ◽

10.30539/iraqijvm.v38i2.220 ◽

2014 ◽

Vol 38 (2) ◽

pp. 35-40

Author(s):

Zina Saab Khudhir

Keyword(s):

Lactobacillus Acidophilus ◽

Synergistic Effects ◽

Antimicrobial Effect ◽

Average Diameter ◽

Raw Milk ◽

Inhibition Zone ◽

Latex Agglutination ◽

Lactobacillus Bulgaricus ◽

Milk Samples ◽

Test Kit

The aims of this study to evaluate the antibacterial potential of standard strains (Lactobacillus acidophilus ROO52 and Lactobacillus bulgaricus LB-12) that produce bacteriocins against E.coli O157:H7 in raw milk. Thirty raw milk samples randomly were collected weekly different markets of Baghdad city in order to investigate the prevalence of E.coli O157:H7 in milk. The prevalence of E.coli O157:H7 in raw milk samples was 6 out 30 (20%) by using the modern chromogenic media with serological latex agglutination test kit. The average diameter of the inhibition zone of crude bacteriocin against E .coli O157:H7 by using combination of 1:1 (v/v) of the Lactobacillus acidophillus ROO52 and Lactobacillus bulgaricus LB-12was (14mm) ,while that produced by bacteriocins of Lactobacillus acidophillus ROO52 and Lactobacillus bulgaricus LB-12 independently were 16 and 12mm respectively .L. delbrucekii ssp bulgaricus showed significantly (P<0.05) low antimicrobial effect against E.coli O157 :H7 .While the strongest antimicrobial effect was shown by Lactobacillus acidophilus ROO52. The bacteriocins of the reference strains used in this study did not result in an increase in inhibition when used in combination of 1:1 (v/v).

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Survival Enterohaemorrhagic E.coli O157in locally produce soft cheese in Baghdad city and studying the effect of some physical factors on its viability

The Iraqi Journal of Veterinary Medicine ◽

10.30539/iraqijvm.v32i2.744 ◽

2008 ◽

Vol 32 (2) ◽

pp. 108-119

Author(s):

Najim Hadi Najim

Keyword(s):

Statistical Analysis ◽

Salt Concentration ◽

Storage Temperature ◽

Raw Milk ◽

Physical Factors ◽

High Concentration ◽

Soft Cheese ◽

Nonsignificant Effect

A total of 24 samples of three different kinds of locally produced softcheese manufactured from raw milk of Cows , Buffaloes and Ewes( 8 samples of each) were collected at weekly intervals from differentareas of Baghdad city in the period from the beginning of December2007 till the end of January 2008.The main objective of this study was to isolats , identify andenumerate Enterohaemorrhagic E.coli O157from locally produced softcheese , besides that , to study the effect of cheese storage temperature(4 C) and different salt concentration solutions on the viability andsurvival of E.coli O157 in stored cheese .Data demonstrate that 11 out 24 of samples 45.84% were found tohave Enterohaemorrhagic E.coli O157 and their average counts were1.6× 104 CFU/gm.The result of statistical analysis demonstrate that cheese samplesmanufactured from cows raw milk had significantly ( P> 0.05) higherE.coli O157 counts and isolation rates over both cheese samples thatwere manufactured from Ewes and buffaloes raw milk .the average count of Enterohaemorrhagic E.coli O157 in cheesemanufactured from cows milk were 3.8× 104 CFU/gm and the isolationpercentage was 75% while their average counts in cheese manufacturedfrom Ewes and buffaloes milk were 7.3 ×103 & 2.4 ×103 CFU/gmrespectively and the isolation percentages were 37.5 % & 12.5%respectively.Data revealed that all soft cheese samples that were found to haveEnterohaemorrhagic E.coli O157 and stored at refrigeration temperature(4 C) had non significant ( P<0.05) reduction in the average counts ofE.coli O157after 3 weeks of storage and this indicate that the refrigerationstorage temperature (4 C) had no significant effect on the viabilityand survival of E.col O157 .All soft cheese samples that were found tohave Enterohaemorrhagic E.coli O157 were stored in brinesolutions at different salt concentrations such as 2.5%, 5%,7% and10% for 24 hr,1 week, 2weeks & 3weeks . Data revealed that brinesolution at high concentration of salt such as 10% had nonsignificant effect on the viability and survival of E.coli O157after 3weeks of storage.

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The combined action of the Nisin and Lactoperoxidase system activation on the microbiological quality of raw milk with special emphasis against E.coli O157H7 in milk

The Iraqi Journal of Veterinary Medicine ◽

10.30539/iraqijvm.v40i2.113 ◽

2017 ◽

Vol 40 (2) ◽

pp. 61-65

Author(s):

Zina Saab Khudhir

Keyword(s):

Microbiological Quality ◽

Storage Period ◽

Raw Milk ◽

Lactobacillus Strain ◽

Lactoperoxidase System ◽

Test Kit ◽

Soft Cheese ◽

C 30 ◽

Refrigeration Storage ◽

Antimicrobial Potency

Escherichia coli O157:H7 were isolated from 90 bovine and ovine locally produced soft cheese samples and their identification were confirmed based on the cultural, biochemical reactions and serological properties, E.coli O157:H7 isolates obtained by plating on the Chromogenic agars. They were further tested serologically for the presence of both O157 and H7 antigenes using the agglutination test kit. The highest non-significant prevalence (P>0.05) level of E.coli O157:H7 was found in the ewe’s soft cheese samples (37.77%) followed by the cow’s soft cheese samples (31.11%). The antimicrobial potency of the Nisin against the sensitive Lactobacillus strain was lost after (10) minutes of heating at (80°C) while retaining (100%) of its antimicrobial potency after its exposure to the pasteurization time and temperature (63°C/ 30 min.). The highest antimicrobial potency of Nisin was achieved at neutral pH (100%) while 90% and 45% of its potency were retained under acidic (pH=3) and alkaline (pH=9) conditions respectively. Nisin had short bacteriocidal incubation period against the sensitive lactobacillus strain where its antimicrobial potency reduced after 48 hours and lost after 120 hours of refrigeration storage period. E.coli O157:H7 was insensitive to the action of Nisin while stressed E.coli O157:H7 by activation of lactoperoxidase system in pasteurized milk was susceptible to its action and such result gave an indication of the synergistic effect of Nisin with activated lactoperoxidase system.

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Efficacy of Bacteriocin Extracted from Lactobacillus acidophilus (LAK) against Bacillus cereus in cow raw milk

The Iraqi Journal of Veterinary Medicine ◽

10.30539/iraqijvm.v39i2.184 ◽

2015 ◽

Vol 39 (2) ◽

pp. 91-97

Author(s):

Thikra M. Ali

Keyword(s):

Bacillus Cereus ◽

Lactobacillus Acidophilus ◽

Pathogenic Bacteria ◽

Inhibitory Concentration ◽

Bovine Milk ◽

Raw Milk ◽

Bactericidal Effect ◽

Gram Stain ◽

Zone Of Inhibition ◽

High Potency

Fifty seven out of ninety bovine milk samples were collected from different areas inside and nearby Baghdad which were positive for Bacillus cereus. The isolates were checked on chromogenic Bacillus cereus agar which was specific for detection of B. cereus colonies. The colony appearance, gram stain, spore stain and oxidase lipase monitol catalase tests were carried out to identify this bacterium. Bacteriocin extracted from Lactobacillus acidophilus was used as a tool to control the growth of undesirable B. cereus growth as spoilage and pathogenic bacteria as well as to keep the food more acceptable and safe to consumer. The results of this study showed that bacteriocin (LAK) had 8 a bactericidal effect against B. cereus in refrigeration and room temperatures at pH 4, 7 and 9, respectively. High potency of bacteriocin (LAK) was confirmed by minimum inhibitory concentration at 30, 60 and 120 minutes. It was found that the zone of inhibition of B. cereus by bacteriocin at 4°C and pH 7 was 26 mm. The present study revealed that bacteriocin was highly effective against locally isolated B. cereus.

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The antibacterial activity of bacteriocin produced by Lactobacillus acidophilus isolates against sensitive reference strain Lactobacillus acidophilus R0052 and its stability to different pH, heating and storage temperatures

The Iraqi Journal of Veterinary Medicine ◽

10.30539/iraqijvm.v36i0e.428 ◽

2012 ◽

Vol 36 (0E) ◽

pp. 274-279

Author(s):

Najim Hadi Najim

Keyword(s):

Antimicrobial Activity ◽

Lactobacillus Acidophilus ◽

Storage Temperature ◽

Inhibition Zone ◽

Antimicrobial Activities ◽

Sensitive Strain ◽

Heat Stable ◽

Soft Cheese ◽

And Storage ◽

Antimicrobial Effectiveness

Two isolates of Lactobacillus acidophilus were isolated from locally homemade soft cheese and identified in accordance with their main features as described by bergeys manual of determinative bacteriology .Agar well diffusion bioassay was used for the evaluation of antimicrobial activity of cell free supernatant (culture filtrates) of Lactobacillus acidophilus isolates against the sensitive strain Lactobacillus acidophilus R0052 and the diameter of the inhibition zone was proportional to the bacteriocin concentration. The antimicrobial activity of the bacteriocin was proportional to the reciprocal of the highest dilution factor producing a detectable zone of inhibition . The storage temperature of the crude bacteriocin had a significant(P˂ 0.01) effect on its potency against the sensitive strain .The potential of the antimicrobial activities of the crude bacteriocin that was stored for 10 days at refrigeration temperature (4°C) was significantly (P˂ 0.01) higher than that stored at room temperature. The antimicrobial effectiveness of the crude bacteriocin was heat stable and retaining 100% of its activity after its exposure to 60 °C & 80°C for 10 minutes .Boiling of the crude bacteriocin for 30 minutes had significantly (P˂ 0.01) decreased its potency to 0% .The potency of the crude bacteriocin was stable after four hours of exposure to both neutral (pH7) and acidic (pH4) conditions but was inactivated at alkaline (pH9) condition.

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Prevalence of Listeria species in raw milk, ice cream and yogurt and effect of selected natural herbal extract on its survival

Mansoura Veterinary Medical Journal ◽

10.35943/mvmj.2020.21.317 ◽

2020 ◽

Vol 21 (3) ◽

pp. 99-106

Author(s):

Mona Yousef ◽

Hazem Ramadan ◽

Maha Al-Ashmawy

Keyword(s):

Plant Extract ◽

Reduction Rate ◽

Ice Cream ◽

Raw Milk ◽

Inhibitory Effect ◽

Food Preservation ◽

Herbal Extract ◽

Listeria Species ◽

Soft Cheese ◽

High Reduction

Objective: This study aimed to detect the prevalence of Listeria species in raw milk, ice cream and yogurt, and to evaluate the effect of extract of clove, thyme and pomegranate peel on such organism. Design: Descriptive study. Procedures: One hundred and fifty samples of milk, ice cream and yogurt were examined for isolation, identification and molecular identification of Listeria spp. Extraction of natural plant extract as clove, thyme and pomegranate peels and detection of their inhibitory effect on Listeria spp. Results: The prevalence of Listeria spp. in milk was 36% where 14% as L. monocytogenes, 6% L. innocua and 16% and other Listeria spp. was 16%. In yogurt, Listeria spp. was 6% as L. innocua was 2% and other Listeria spp. was 4%, while no L. monocytogenes was detected. In ice cream, Listeria spp. was 8% where L. monocytogenes was 2% and other Listeria spp. was 6% while no L. innocua was detected. The concentration of plant extract was 2.5% which showed high reduction rate on L. innocua and L. monocytogenes during shelf life of soft cheese. Conclusion and clinical relevance: Listeria is widely isolated from milk than from ice cream and yogurt. Plant extracts play role in food preservation and consider as a natural antimicrobial agent where most effective one was clove extract.

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