Escherichia coli and Enterococcus spp. Indigenous to Wastewater Have Slower Free Chlorine Disinfection Rates than Their Laboratory-Cultured Counterparts

To the best of our knowledge, there was little information available on pathogen removal using low level disinfectant followed by free chlorine in sequential disinfection (SD). This study investigated Escherichia coli inactivation by four types of disinfection: single step disinfection (SSD), SD, traditional sequential disinfection (TSD) and mixed disinfectant disinfection (MDD). Results indicated that SD had higher ability to inactivate E. coli than the others, indicating there was a positive synergistic effect on chlorine disinfection by prior dosing with a low level of chlorine dioxide (ClO2). The ONPG assay suggested that the permeability of cell wall rather than the viability of E. coli were changed under 0.02 mg/l ClO2 treatment. The coexistence of residual ClO2 and free chlorine also plays an active synergistic effect. Additionally, temperature had a positive effect on E. coli inactivation in SD, while inactivation was reduced in alkaline compared to neutral and acidic conditions.

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Free Chlorine Disinfection of Full-Scale MBR Effluent to Achieve 5-Log Virus Inactivation

Water Environment Research ◽

10.2175/106143017x15131012153103 ◽

2018 ◽

Vol 90 (7) ◽

pp. 623-633 ◽

Cited By ~ 3

Author(s):

Keisuke Ikehata ◽

Yuan Li ◽

Andrew T. Komor ◽

Gregory W. Gibson

Keyword(s):

Full Scale ◽

Free Chlorine ◽

Virus Inactivation ◽

Chlorine Disinfection

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Quantitative Determination of the Role of Lettuce Leaf Structures in Protecting Escherichia coli O157:H7 from Chlorine Disinfection

Journal of Food Protection ◽

10.4315/0362-028x-64.2.147 ◽

2001 ◽

Vol 64 (2) ◽

pp. 147-151 ◽

Cited By ~ 89

Author(s):

KAZUE TAKEUCHI ◽

JOSEPH F. FRANK

Keyword(s):

Escherichia Coli ◽

Leaf Surface ◽

Dead Cell ◽

Escherichia Coli O157 ◽

E Coli ◽

Chlorine Disinfection ◽

Sytox Green ◽

Tissue Surface ◽

Confocal Scanning

Viability of Escherichia coli O157:H7 cells on lettuce leaves after 200 mg/liter (200 ppm) chlorine treatment and the role of lettuce leaf structures in protecting cells from chlorine inactivation were evaluated by confocal scanning microscopy (CSLM). Lettuce samples (2 by 2 cm) were inoculated by immersing in a suspension containing 109 CFU/ml of E. coli O157: H7 for 24 ± 1 h at 4°C. Rinsed samples were treated with 200 mg/liter (200 ppm) chlorine for 5 min at 22°C. Viability of E. coli O157:H7 cells was evaluated by CSLM observation of samples stained with Sytox green (dead cell stain) and Alexa 594 conjugated antibody against E. coli O157:H7. Quantitative microscopic observations of viability were made at intact leaf surface, stomata, and damaged tissue. Most E. coli O157:H7 cells (68.3 ± 16.2%) that had penetrated 30 to 40 μm from the damaged tissue surface remained viable after chlorine treatment. Cells on the surface survived least (25.2 ± 15.8% survival), while cells that penetrated 0 to 10 μm from the damaged tissue surface or entered stomata showed intermediate survival (50.8 ± 13.5 and 45.6 ± 9.7% survival, respectively). Viability was associated with the depth at which E. coli O157:H7 cells were in the stomata. Although cells on the leaf surface were mostly inactivated, some viable cells were observed in cracks of cuticle and on the trichome. These results demonstrate the importance of lettuce leaf structures in the protection of E. coli O157:H7 cells from chlorine inactivation.

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Effect of Heat Treatment on the Activity of the Enterococcus spp. and Escherichia coli Nissle 1917 in the Presence of Lactulose and Apple and Orange Extracts

Journal of Food and Dairy Sciences ◽

10.21608/jfds.2020.78885 ◽

2020 ◽

Vol 11 (2) ◽

pp. 59-63

Author(s):

T. Nassib ◽

Esraa El-Amir

Keyword(s):

Escherichia Coli ◽

Heat Treatment ◽

Escherichia Coli Nissle 1917 ◽

Enterococcus Spp ◽

Escherichia Coli Nissle

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Evaluation of sanitary quality of goat milk in dairy industries from the Cariri region, state of Paraíba

Research Society and Development ◽

10.33448/rsd-v10i12.20735 ◽

2021 ◽

Vol 10 (12) ◽

pp. e596101220735

Author(s):

Iara Nunes de Siqueira ◽

Aline Antas Cordeiro Cavalcanti ◽

Joyce Galvão de Souza ◽

Filipe Jordão Pereira de Medeiros ◽

João Carlos Taveira ◽

...

Keyword(s):

Escherichia Coli ◽

Listeria Monocytogenes ◽

Pathogenic Bacteria ◽

Goat Milk ◽

Salmonella Spp ◽

Pasteurized Milk ◽

Enterococcus Spp ◽

Bacillus Spp ◽

Thermotolerant Coliforms ◽

Staphylococcus Spp

The sanitary evaluation of equipment and hands is fundamental to investigate the presence of pathogens in the dairy industry. Then, this study aims to evaluate the sanitization of equipment, workers’ hands, raw and pasteurized milk in goat milk dairies in the Cariri region, state of Paraíba. Collected 32 samples of four dairies represented by letters A, B, C, and D. The followings contents were analyzed: mesophiles, total and thermotolerant coliforms, Escherichia coli, Staphylococcus aureus, Samonella spp. and Listeria monocytogenes in the reception tank, pasteurization tank, packing machine, package, wall, workers’ hand, and each dairy’s raw and pasteurized milk. After isolation, 84 colonies were confirmed by MALDI TOF. The indicator microorganisms presented variations for the workers’ hands, while A and B stayed within the patterns. For the equipment, only dairy B was within limits. They were out of the standard for mesophiles, total coliforms, and thermotolerant regarding raw and pasteurized milk. The microorganisms, the Enterobacteriaceae family presented a higher frequency, with 77.38%, and within this family, Escherichia coli, Klebsiella spp., and Enterobacter spp. were the most prevalent. Gram-positive corresponded to 22.62%, Bacillus spp., Staphylococcus spp., Enterococcus spp., and Macrococcus caseolyticus. Listeria monocytogenes and Salmonella spp. were not isolated. These demonstrate failures in goat milk processing with pathogenic bacteria in several dairy plants, indicating the need to adjust the product’s quality control.

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Development of an Algorithm for Feed-Forward Chlorine Dosing of Lettuce Wash Operations and Correlation of Chlorine Profile with Escherichia coli O157:H7 Inactivation

Journal of Food Protection ◽

10.4315/0362-028x.jfp-13-352 ◽

2014 ◽

Vol 77 (4) ◽

pp. 558-566 ◽

Cited By ~ 19

Author(s):

BIN ZHOU ◽

YAGUANG LUO ◽

XIANGWU NOU ◽

PATRICIA MILLNER

Keyword(s):

Escherichia Coli ◽

Reduction Potential ◽

Free Chlorine ◽

Organic Load ◽

Escherichia Coli O157 ◽

Feed Forward ◽

E Coli ◽

Wash Solution ◽

Oxidation Reduction ◽

Oxidation Reduction Potential

The dynamic interactions of chlorine and organic matter during a simulated fresh-cut produce wash process and the consequences for Escherichia coli O157:H7 inactivation were investigated. An algorithm for a chlorine feed-forward dosing scheme to maintain a stable chlorine level was further developed and validated. Organic loads with chemical oxygen demand of 300 to 800 mg/liter were modeled using iceberg lettuce. Sodium hypochlorite (NaOCl) was added to the simulated wash solution incrementally. The solution pH, free and total chlorine, and oxidation-reduction potential were monitored, and chlorination breakpoint and chloramine humps determined. The results indicated that the E. coli O157:H7 inactivation curve mirrored that of the free chlorine during the chlorine replenishment process: a slight reduction in E. coli O157:H7 was observed as the combined chlorine hump was approached, while the E. coli O157:H7 cell populations declined sharply after chlorination passed the chlorine hump and decreased to below the detection limit (<0.75 most probable number per ml) after the chlorination breakpoint was reached. While the amounts of NaOCl required for reaching the chloramine humps and chlorination breakpoints depended on the organic loads, there was a linear correlation between NaOCl input and free chlorine in the wash solution once NaOCl dosing passed the chlorination breakpoint, regardless of organic load. The data obtained were further exploited to develop a NaOCl dosing algorithm for maintaining a stable chlorine concentration in the presence of an increasing organic load. The validation tests results indicated that free chlorine could be maintained at target levels using such an algorithm, while the pH and oxidation-reduction potential were also stably maintained using this system.

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