PubMed Health⌕ Search

Biomedical subjects

E C Cole

Publications and source records attributed to E C Cole.

11 recordsLinked to original sources
PubMed1991

Inactivation of Mycobacterium tuberculosis and Mycobacterium bovis by 14 hospital disinfectants.

Epidemics of mycobacteria due to contamination of medical devices continue to occur. For this reason, we assessed the ability of disinfectants, generally used in hospitals for disinfecting noncritical and semicritical patient care items, to inactivate mycobacteria. A modified Association of Official Analytical Chemists' (AOAC) Tuberculocidal Activity Test, using Middlebrook 7H9 broth as the primary subculture medium and neutralization by dilution, was used to assess the ability of 14 hospital disinfectants to inactivate about 10(6) Mycobacterium tuberculosis and about 10(5) Mycobacterium bovis at 20 degrees C using 10- or 20-minute exposure. All products were tested for each organism using 10 penicylinders (P) and were prepared at the manufacturers' recommended use-dilution. Chlorine dioxide, 0.80% hydrogen peroxide plus 0.06% peroxyacetic acid, and an iodophor achieved complete inactivation (0 + P) of both M. tuberculosis and M. bovis. One quaternary ammonium compound with a tuberculocidal label claim, a quaternary ammonium compound without a tuberculocidal label claim, chlorine (approximately 100 ppm) and 0.13% glutaraldehyde/0.44% phenol/0.08% phenate were not effective (10 + P) against both M. tuberculosis and M. bovis. Another quaternary ammonium compound with a tuberculocidal label claim was tested against only M. bovis and found ineffective (10 + P). Glutaraldehydes (2% alkaline and 2% acid), a phenolic and chlorine (approximately 1,000 ppm) demonstrated complete inactivation of M. tuberculosis (0 + P) and good inactivation of M. bovis (1-3 + P). Two disinfectants, hydrogen peroxide and ethyl alcohol, provided differing results against M. tuberculosis and M. bovis. These studies have important implications for disinfecting semicritical patient care items.

Chlorine↗
PubMed1990

Effect of methodology, dilution, and exposure time on the tuberculocidal activity of glutaraldehyde-based disinfectants.

The Association of Official Analytical Chemists (AOAC) test for assessing the tuberculocidal activity of disinfectants has been shown to be variable. A modified AOAC test, which substituted Middlebrook 7H9 broth as the primary subculture medium and used neutralization by dilution, was compared with the standard AOAC method to assess the mycobactericidal activity of three glutaraldehyde-based disinfectants at 20 degrees C and various exposure times. These changes had a marked effect on results, with the modified AOAC test providing more positive penicylinders per 10 replicates in 12 of the 13 comparisons that provided positive results. These differences were observed with both Mycobacterium bovis (ATCC 35743) and a clinical isolate of Mycobacterium tuberculosis. The effects of various exposure times to and dilutions of the glutaraldehyde-based disinfectants were also examined. The minimum exposure time needed to inactivate reliably M. bovis or M. tuberculosis with 2% glutaraldehyde was 20 min at 20 degrees C. Diluting 2% glutaraldehyde caused a significant decline in mycobactericidal activity. Modification of the standard AOAC test to improve its sensitivity in detecting the failure of disinfectants to inactivate mycobacteria is indicated.

Aldehydes↗
PubMed1989

Pseudomonas pellicle in disinfectant testing: electron microscopy, pellicle removal, and effect on test results.

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.

Disinfectants↗
PubMed1987

Ineffectiveness of hospital disinfectants against bacteria: a collaborative study.

A collaborative study was undertaken to assess the degree of variability in disinfectant efficacy test results among laboratories that routinely perform the Association of Official Analytical Chemists (AOAC) Use-Dilution Method. Eighteen laboratories tested identical samples of six EPA-registered, hospital-grade disinfectants (three phenolics and three quaternaries) at the manufacturers' recommended use-dilution using only those modifications of the method approved by the AOAC Use-Dilution Task Force. Each laboratory processed 60 penicylinders for each of the 6 randomly selected disinfectants and 3 test organisms. The current EPA pass criterion for a disinfectant requires a test result of less than or equal to 1 positive penicylinder/60 replicates tested When compared with the 1 positive/60 replicate criterion, the test results of the 6 disinfectants were: 86 trials (80%) passed and 22 trials (20%) failed against Salmonella choleraesuis ATCC 10708; 71 (66%) passed and 37 (34%) failed against Staphylococcus aureus ATCC 6538; and 41 (38%) passed while 67 (62%) failed against Pseudomonas aeruginosa ATCC 15442. Four laboratories unknowingly tested their own product, and three of the four failed their product against one or more of the test organisms. These results show the inability to reproduce the manufacturers' bactericidal label claims for 6 disinfectants against the 3 AOAC test bacteria. In addition, extreme variability of test results among laboratories testing identical products questions the use of the AOAC Use-Dilution Method for enforcement action.

Disinfectants↗
PubMedDate not supplied

Evaluation of penicylinders used in disinfectant testing: bacterial attachment and surface texture.

Two possible deficiencies in the AOAC use-dilution method for registration of chemical disinfectants by the Environmental Protection Agency are examined: (1) the physical disparities among brands of penicylinders and (2) the variability of bacterial numbers on penicylinders depending upon test strain and penicylinder surface texture. Textural differences of 2 brands of stainless steel penicylinders, one brand of porcelain, and one brand of glass were assessed by scanning electron microscopy. A considerable variation in smoothness of both inner and outer surfaces of stainless steel and porcelain penicylinders was observed. Glass penicylinders were very smooth. Numbers of bacteria attached to a penicylinder were assessed by vortexing the penicylinders 30 s at No. 4 after using the AOAC method of bacterial inoculation and drying 40 min at 37 degrees C. With this methodology, stainless steel carriers retained the 3 AOAC-recommended bacterial test strains differentially: ca 10(7) for Pseudomonas aeruginosa, 5 X 10(6) for Staphylococcus aureus, and 10(6) for Salmonella choleraesuis; glass retained 10(6)-10(7) organisms of all 3 test strains; porcelain retained about that amount of S. aureus but 10(5)-10(6) P. aeruginosa and 10(3)-10(4) S. choleraesuis. These data suggest that disinfectants are not similarly challenged with the AOAC-recommended test bacteria and that an alternative method should be considered to ensure comparable numbers of bacteria on penicylinders.

Bacteria↗
PubMedDate not supplied

Bacterial numbers on penicylinders used in disinfectant testing: use of 24 hour adjusted broth cultures.

The current AOAC use-dilution methods of disinfectant efficacy testing require the use of 48-54 h unadjusted broth cultures of Salmonella choleraesuis, Staphylococcus aureus, and Pseudomonas aeruginosa for the inoculation of stainless steel penicylinders. The use of unadjusted broth cultures contributes to noncomparable numbers of organisms on penicylinders among the test strains due to relative efficacy of bacterial attachment to penicylinders and to bacterial numbers in broth. To achieve comparable numbers of cells on the penicylinders among the 3 test strains, the cell densities of S. aureus and P. aeruginosa in broth culture were visually adjusted. Growth studies were conducted using S. choleraesuis and P. aeruginosa to determine the numbers of cells in broth at timed intervals and the corresponding numbers of cells attaching to the penicylinders. Results showed that the use of the 24 h broth cultures for all 3 test strains, with adjustment of S. aureus and P. aeruginosa broths, contributes to more comparable numbers of organisms attached to the penicylinders used in disinfectant testing.

Bacteria↗
PubMedDate not supplied

Comparison of stainless steel penicylinders used in disinfectant testing.

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.

Culture Media↗
PubMedDate not supplied

Quantitative evaluation of bacteria washed from stainless steel penicylinders during AOAC use-dilution method.

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.

Bacteriological Techniques↗
PubMedDate not supplied

Disinfectant testing using a modified use-dilution method: collaborative study.

An initial collaborative study of the AOAC use-dilution method (UDM), used for bactericidal disinfectant efficacy testing, demonstrated extreme variability of test results among the 18 laboratories testing identical hospital disinfectants. In an effort to improve the method, 32 changes were made by the UDM Task Force. These changes represented improvements in quality assurance practices and elimination of method variability; however, the basic framework of the method was retained. A second collaborative trial was conducted to determine if the interlaboratory variability of test results could be reduced to an acceptable level using the modified UDM. Twelve of the original 18 laboratories participated in the second study. Each laboratory processed 60 penicylinders (P) for each of the 6 randomly selected, federally registered disinfectants and 3 test organisms (Staphylococcus aureus, Salmonella choleraesuis, Pseudomonas aeruginosa). The number of positive penicylinders (greater than 1 positive P/60 replicates = failure) for the 6 products when P. aeruginosa was used as the challenge organism ranged 1-30, 0-36, 0-15, 0-5, 0-3, and 0-60 for the 3 quaternaries and 3 phenolics, respectively. The results of the variance components analysis for P. aeruginosa and the other 2 organisms showed that the variance components for laboratories were not significantly reduced for any organism in this study. Such interlaboratory variability of results questions the use of the original or the modified UDM for registration purposes.

Bacteriological Techniques↗
PubMedDate not supplied

Standardization of bacterial numbers of penicylinders used in disinfectant testing: interlaboratory study.

An interlaboratory study was conducted to evaluate a method of standardizing bacterial numbers on penicylinders used in the AOAC use-dilution method (4.007-4.015) of disinfectant testing. Eight participating laboratories followed a broth adjustment method using their media and stock cultures of Staphylococcus aureus ATCC 6538, Salmonella choleraesuis ATCC 10708, and Pseudomonas aeruginosa ATCC 15442. The culture broths that were used to inoculate the penicylinders were incubated for 48 h at 37 degrees C after several (4-6) 24 h passages. McFarland turbidity standards of 1.0 and 0.5 were used to adjust visually the cultures of S. aureus and P. aeruginosa, respectively. S. choleraesuis was used undiluted. The results showed significant variability in numbers of test bacteria which adhered to the penicylinders, with mean values of 1.6 X 10(6) for S. choleraesuis, 3.5 X 10(6) for S. aureus, and 8.2 X 10(6) for P. aeruginosa. The results from collaborating laboratories attempting standardization of bacterial numbers on penicylinders demonstrated significant interlaboratory and cylinder variation for all 3 test organisms.

Bacteria↗