Comparative evaluation of methods for counting surviving biofilm cells adhering to a polyvinyl chloride surface exposed to chlorine or drying.
OBJECTIVE
To compare techniques for assessing biofilm populations previously subjected, or not, to inimical treatment by chlorine or drying.


RESULTS
Four sonication treatments and swabbing were compared on Salmonella Typhimurium or Pseudomonas fluorescens biofilms grown on polyvinyl chloride (PVC). The apparatuses emitting the highest ultrasound energy were the most efficient except on Salm. Typhimurium biofilms subjected to drying: a lethal effect, leading to an underestimation of at least 1.5 log (CFU cm(-2)) was observed with the more aggressive treatment. The differences between the highest count and the swabbing counts ranged from 0.3 log (CFU cm(-2)) (untreated Salm. Typhimurium) to 1.7 log (CFU cm(-2)) (chlorine treated Ps. fluorescens). Impedance measurements, used to assess populations without detaching any cells showed that the calibration curves that were built up from data obtained with suspended cells plus PVC slides were not appropriate.


CONCLUSIONS
High energy ultrasound techniques designed either for in vitro or in situ studies proved efficient in assessing the number of attached CFU. However, the right treatment duration has to be carefully established before using high energy ultrasound techniques.


CONCLUSIONS
The effectiveness of a cleaning and disinfection regime inferred from data obtained after swabbing may be greatly underestimated.
Asséré
A
A
Agence Française de Sécurité Sanitaire des Aliments, Laboratoire d'études et de recherches sur la qualité des aliments et sur les procédés agroalimentaires, Maisons-Alfort, France.
Oulahal
N
N
Carpentier
B
B
D001422:Bacterial Adhesion / Q000187:drug effects; D001431:Bacteriological Techniques; D018441:Biofilms / Q000187:drug effects / Q000254:growth & development; D002713:Chlorine / Q000494:pharmacology; D015169:Colony Count, Microbial / Q000379:methods; D003890:Desiccation; D004202:Disinfectants / Q000494:pharmacology; D004203:Disinfection / Q000379:methods*; D005516:Food Microbiology; D005525:Food-Processing Industry; D011143:Polyvinyl Chloride; D011551:Pseudomonas fluorescens / Q000187:drug effects / Q000254:growth & development; D012486:Salmonella typhimurium / Q000187:drug effects / Q000254:growth & development
D004202:Disinfectants; D002713:Chlorine; D011143:Polyvinyl Chloride