Efficacy of a Sonicating Swab for Removal and Capture of Listeria monocytogenes in Biofilms on Stainless Steel.
Listeria monocytogenesis 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. monocytogenesbiofilms 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≤ 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≤ 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.IMPORTANCEInadequate 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.
Biological Science and Technology Team, Natick Soldier Research, Development and Engineering Center, Natick, Massachusetts, USA.
Tobyn A
TA
Branck
Design, Engineering, and Fabrication Team, Engineering Cell, Natick Soldier Research, Development and Engineering Center, Natick, Massachusetts, USA.
Matthew J
MJ
Hurley
Food Protection and Innovative Packaging Team, Natick Soldier Research, Development and Engineering Center, Natick, Massachusetts, USA.
Gianna N
GN
Prata
Food Protection and Innovative Packaging Team, Natick Soldier Research, Development and Engineering Center, Natick, Massachusetts, USA.
Christina A
CA
Crivello
Food Protection and Innovative Packaging Team, Natick Soldier Research, Development and Engineering Center, Natick, Massachusetts, USA patrick.j.marek4.civ@mail.mil.
Patrick J
PJ
Marek
D001422:Bacterial Adhesion; D018441:Biofilms; D005516:Food Microbiology; D008089:Listeria monocytogenes / Q000145:classification / Q000235:genetics / Q000302:isolation & purification* / Q000502:physiology; D008828:Microbiological Techniques / Q000295:instrumentation / Q000379:methods*; D013193:Stainless Steel / Q000032:analysis*
D013193:Stainless Steel
biofilm; capture; removal; sonicating; swab