Comparative evaluation of methods for counting surviving biofilm cells adhering to a polyvinyl chloride surface exposed to chlorine or drying

Asséré, Adrien; Oulahal, Nadia; Carpentier, Brigitte

doi:10.1111/j.1365-2672.2007.03711.x

Cited by 63 publications

(23 citation statements)

References 26 publications

(62 reference statements)

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“…We hypothesized that increase in k w observed at higher velocity could be attributed to organic matter release from pipe wall which accelerated the rate of chlorine consumption. This hypothesis is supported by other studies that reported higher cell counts in the biofilm formed on PVC as compared to copper or polyethylene pipe surfaces [12][13][14] . Another study reported that the organic matter released is directly proportional to the shear stress exerted on the walls as water flows in the pipe which become constant after attaining a certain velocity 15 .…”

Section: Wall Reaction Ratesupporting

confidence: 84%

Effect of Flow Velocity on Chlorine Decay in Water Distribution Network:A Pilot Loop Study

Jamwal¹,

Kumar²

2016

Current Science

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Experiments were run in the pipe loop setup to estimate bulk and wall chlorine decay rates under varying flow and chlorine levels for groundwater. A recirculating loop of 50 mm inner diameter polyvinyl chloride pipe and a variable flow pump with feed and recirculation tank were used to design a pipe loop. Sodium hypochlorite was introduced as free chlorine into the test water. The study came up with three important findings: (a) bulk chlorine decay rate in test water decreased with increase in chlorine levels, which is attributed to the type and level of organic matter present in test water. (b) Chlorine decay rate in pilot loop setup increased with increase in flow velocity. The result showed that under turbulent conditions, in addition to chlorine, mass flux transfer from bulk to wall and biofilm removal from pipe surface contributed to chlorine decay. We also noted that with increase in flow velocity the contribution of bulk reaction to total chlorine decay in pipe loop decreased. (c) ANOVA test on experimental dataset showed that as compared to initial chlorine levels, flow velocity has statistically significant effect on chlorine dissipation in a pipe loop. We also found that after turbulent flow is achieved, the effect of flow velocity on the wall decay is negligible.

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Section: Wall Reaction Ratesupporting

confidence: 84%

Effect of Flow Velocity on Chlorine Decay in Water Distribution Network:A Pilot Loop Study

Jamwal¹,

Kumar²

2016

Current Science

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“…4). This observation suggests that the bead vortexing procedure and/or the conventional plating technique used in this study could underestimate the attached microbial population on SS coupons and thus the actual risk of contaminated surfaces (1). It has also been suggested that in order to survive under adverse environmental conditions, many food-borne pathogens enter a viable but nonculturable state (i.e., a dormant state) (51) in which they maintain metabolic activity and pathogenicity but cannot be cultured by common laboratory methods (39).…”

Section: Discussionmentioning

confidence: 93%

Listeria monocytogenes Attachment to and Detachment from Stainless Steel Surfaces in a Simulated Dairy Processing Environment

Poimenidou¹,

Belessi²,

Giaouris

et al. 2009

Appl Environ Microbiol

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The presence of pathogens in dairy products is often associated with contamination via bacteria attached to food-processing equipment, especially from areas where cleaning/sanitation is difficult. In this study, the attachment of Listeria monocytogenes on stainless steel (SS), followed by detachment and growth in foods, was evaluated under conditions simulating a dairy processing environment. Initially, SS coupons were immersed in milk, vanilla custard, and yogurt inoculated with the pathogen (10 7 CFU/ml or CFU/g) and incubated at two temperatures (5 and 20°C) for 7 days. By the end of incubation, cells were mechanically detached from coupons and used to inoculate freshly pasteurized milk which was subsequently stored at 5°C for 20 days. The suspended cells in all three products in which SS coupons were immersed were also used to inoculate freshly pasteurized milk (5°C for 20 days). When SS coupons were immersed in milk, shorter lag phases were obtained for detached than for planktonically grown cells, regardless of the preincubation temperature (5 or 20°C). The opposite was observed when custard incubated at 20°C was used to prepare the two types of inocula. However, in this case, a significant increase in growth rate was also evident when the inoculum was derived from detached cells. In another parallel study, while L. monocytogenes was not detectable on SS coupons after 7 days of incubation (at 5°C) in inoculated yogurt, marked detachment and growth were observed when these coupons were subsequently transferred and incubated at 5°C in fresh milk or/and custard. Overall, the results obtained extend our knowledge on the risk related to contamination of dairy products with detached L. monocytogenes cells.

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“…Sonication is well established as a method to clean surfaces and aid in the removal of biofilms from many types of material surfaces (17)(18)(19). Sonication can be applied to remove adhered biofilms while maintaining cell viability, if employed properly (14,20,21). Biofilm-associated bacteria grown on polyvinyl chloride and stainless steel slides had higher recovery rates when placed in a sonication bath, in comparison with sampling with cotton swabs (21).…”

Section: Importancementioning

confidence: 99%

“…Sonication can be applied to remove adhered biofilms while maintaining cell viability, if employed properly (14,20,21). Biofilm-associated bacteria grown on polyvinyl chloride and stainless steel slides had higher recovery rates when placed in a sonication bath, in comparison with sampling with cotton swabs (21). Direct and indirect contact of stainless steel coupons (SSCs), inoculated with Listeria monocytogenes, with a sonicating toothbrush yielded significantly higher recovery rates (59% and 61%, respectively) than did the Dacron-tipped swab tested (21%) (20).…”

Section: Importancementioning

confidence: 99%

Efficacy of a Sonicating Swab for Removal and Capture of Listeria monocytogenes in Biofilms on Stainless Steel

Branck

Hurley

Prata

et al. 2017

Appl Environ Microbiol

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Listeria monocytogenes is of great concern in food processing facilities because it persists in biofilms, facilitating biotransfer. Stainless steel is commonly used for food contact surfaces and transport containers. L. monocytogenes biofilms on stainless steel served as a model system for surface sampling, to test the performance of a sonicating swab in comparison with a standard cotton swab. Swab performance and consistency were determined using total viable counts. Stainless steel coupons sampled with both types of swabs were examined using scanning electron microscopy, to visualize biofilms and surface structures (i.e., polishing grooves and scratches). Laser scanning confocal microscopy was used to image and to quantitate the biofilms remaining after sampling with each swab type. The total viable counts were significantly higher (P Յ 0.05) with the sonicating swab than with the standard swab in each trial. The sonicating swab was more consistent in cell recovery than was the standard swab, with coefficients of variation ranging from 8.9% to 12.3% and from 7.1% to 37.6%, respectively. Scanning electron microscopic imaging showed that biofilms remained in the polished grooves of the coupons sampled with the standard swab but were noticeably absent with the sonicating swab. Percent area measurements of biofilms remaining on the stainless steel coupons showed significantly (P Յ 0.05) less biofilm remaining when the sonicating swab was used (median, 1.1%), compared with the standard swab (median, 70.4%). The sonicating swab provided greater recovery of cells, with more consistency, than did the standard swab, and it is employs sonication, suction, and scrubbing.IMPORTANCE Inadequate surface sampling can result in foodborne illness outbreaks from biotransfer, since verification of sanitization protocols relies on surface sampling and recovery of microorganisms for detection and enumeration. Swabbing is a standard method for microbiological sampling of surfaces. Although swabbing offers portability and ease of use, there are limitations, such as high user variability and low recovery rates, which can be attributed to many different causes. This study demonstrates some benefits that a sonicating swab has over a standard swab for removal and collection of microbiological samples from a surface, to provide better verification of surface cleanliness and to help decrease the potential for biotransfer of pathogens into foods.KEYWORDS biofilm, capture, removal, sonicating, swab I n 2011 to 2014, the Centers for Disease Control and Prevention reported a total of 87 foodborne disease outbreaks in which cross contamination of ingredients was determined to be a contributing factor (1-4). Many of the reports likely involve cross

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Comparative evaluation of methods for counting surviving biofilm cells adhering to a polyvinyl chloride surface exposed to chlorine or drying

Cited by 63 publications

References 26 publications

Effect of Flow Velocity on Chlorine Decay in Water Distribution Network:A Pilot Loop Study

Effect of Flow Velocity on Chlorine Decay in Water Distribution Network:A Pilot Loop Study

Listeria monocytogenes Attachment to and Detachment from Stainless Steel Surfaces in a Simulated Dairy Processing Environment

Efficacy of a Sonicating Swab for Removal and Capture of Listeria monocytogenes in Biofilms on Stainless Steel

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