Subject(s)
Coccidiosis/diagnosis , Diarrhea/diagnosis , Diarrhea/parasitology , Eucoccidiida/isolation & purification , Animals , Coccidiosis/epidemiology , DNA Probes , Disease Outbreaks , Eucoccidiida/genetics , Feces/parasitology , Food Parasitology , Humans , Polymerase Chain Reaction/methods , Sensitivity and SpecificityABSTRACT
Pseudomonas aeruginosa ATCC 15442 is a required organism in the Association of Official Analytical Chemists use-dilution method for disinfectant efficacy testing. When grown in a liquid medium, P. aeruginosa produces a dense mat or pellicle at the broth/air interface. The purpose of this investigation was to examine the pellicle by scanning electron microscopy, to evaluate three pellicle removal methods, and to determine the effect of pellicle fragments on disinfectant efficacy test results. The efficacies of three methods of pellicle removal (decanting, vacuum suction, and filtration) were assessed by quantifying cell numbers on penicylinders. The Association of Official Analytical Chemists use-dilution method was used to determine whether pellicle fragments in the tubes used to inoculate penicylinders affected test results. Scanning electron micrographs showed the pellicle to be a dense mass of intact, interlacing cells at least 10 microns thick. No significant differences in pellicle removal methods were observed, and the presence of pellicle fragments usually increased the number of positive tubes in the use-dilution method significantly.
Subject(s)
Disinfectants/pharmacology , Pseudomonas aeruginosa/drug effects , Drug Evaluation, Preclinical/methods , Microscopy, Electron, Scanning/methods , Pseudomonas aeruginosa/ultrastructureABSTRACT
Stainless steel penicylinders inoculated separately with test bacteria (Salmonella choleraesuis, Pseudomonas aeruginosa, or Staphylococcus aureus) are used in the AOAC use-dilution method (UDM) for disinfectant efficacy testing. Numbers of bacteria remaining on penicylinders were quantitatively assessed to determine if cells are washed from the penicylinders after a 10 min exposure to phosphate buffer dilution water (PBDW). Inoculated penicylinders were also examined by scanning electron microscopy (SEM) to determine the presence of cells remaining attached to the penicylinders after a 10 min exposure to a quaternary ammonium disinfectant and separately to PBDW. The percentage of cells washed from inoculated penicylinders exposed to PBDW was 89.9 for Salmonella choleraesuis, 48.8 for Pseudomonas aeruginosa, and 38.8 for Staphylococcus aureus. Qualitative examination of penicylinders by scanning electron microscopy confirmed the attachment of S. aureus and P. aeruginosa cells to penicylinders exposed separately to PBDW and a quaternary ammonium disinfectant. Few S. choleraesuis cells were observed on penicylinders exposed to PBDW and no cells were observed after disinfectant exposure. The variability of the numbers of viable cells entering the recovery media among the 3 UDM test bacteria due to cell detachment could be a significant factor in the recognized variability of the use-dilution method.
Subject(s)
Bacteriological Techniques/instrumentation , Culture Media , Microscopy, Electron, Scanning , Pseudomonas aeruginosa/isolation & purification , Salmonella/isolation & purification , Staphylococcus aureus/isolation & purificationABSTRACT
Two brands of stainless steel penicylinders, S&L Metal Products and Fisher Scientific, were simultaneously tested to determine if they provide comparable results when used in the AOAC use-dilution method of disinfectant testing. Results showed consistently more positive tubes for the Fisher brand of penicylinders than for the S&L, regardless of the surface finish of the test cylinders.