Excretion of mutagens following chemotherapy.

The mutagenic activity of urine was evaluated in children receiving single and multiple agent chemotherapy to determine the duration of carcinogenic risk to health care personnel and family contacts. Urine samples from 21 children were evaluated before and daily for 5 days after chemotherapy administration. Mutagenic activity, a sensitive though not specific indicator of carcinogenic risk, was assayed using mutant strains of Salmonella typhimurium (the "Ames test"). Validity of the assay was confirmed by demonstrating mutagenic activity in urine samples from 17 adult cigarette smokers but not from 21 adult nonsmokers (24/24 versus 0/37, p less than 0.001). None of the 21 children tested demonstrated mutagenic activity before chemotherapy administration. Following single agent dactinomycin, cyclophosphamide, daunorubicin, doxorubicin, methotrexate, or vincristine, mutagenic activity was demonstrated for 2 days (5/5 at 1 and 2 days and 0/5 at 3 days). Following multiple agent chemotherapy using two or three of the latter drugs on a single day, mutagenic activity was demonstrated for 4 or 5 days (16/16 at 1, 2, 3, and 4 days, and 4/16 at 5 days). Based on these observations with urine, and presumably other body fluids, precautions are recommended for 2 days following single agent and at least 5 days following multiple agent chemotherapy.

Detection of verotoxin in stool specimens.

A total of 132 fecal specimens containing verotoxin (VT) were subjected to counter-current immunoelectrophoresis (CIE). Of these, 113 (85.6%) were found to be positive by CIE. Another 71 stool specimens containing E. coli serogroup O157 but with flagellar antigens other than H7 were tested for verotoxin by CIE. These stool specimens were negative for VT on Vero cell monolayers. Of these 71 stool specimens, 6 (8.5%) gave positive tests for verotoxin by CIE. Forty stool specimen filtrates which were negative for VT (negative controls) were also subjected to CIE. One of these stool specimen filtrates gave a line of precipitation by CIE. The specificity of the CIE test was 93.7%, and the sensitivity was 85.6%. False-positive results may have been due to an antibody component against the somatic antigen (O157) in the antitoxin used; this is a limitation of the CIE test. In a related evaluation, 302 stool specimen filtrates containing VT were retested with Vero cell suspension cultures in microdilution plates. Of these, 281 stool specimen filtrates showed cytotoxic effects within 24 h, while the remaining 21 filtrates showed the effects within 48 h. The use of Vero cell suspension culture is as reliable as the use of Vero cell monolayers and provides detection of verotoxin 24 to 48 h sooner.

Detection of Clostridium difficile toxin in various tissue culture monolayers.

Thirty stool filtrates known to contain Clostridium difficile toxin based on previous testing on McCoy cells were tested for toxicity on primary African green monkey kidney (AGMK), McCoy, MRC-5, primary rhesus monkey kidney (RMK), and Vero cells. All 30 filtrates showed cytotoxic effect at greater than or equal to 1:100 dilution on McCoy and Vero cells. A total of 22 filtrates were positive on MRC-5 monolayers, while only 16 and 10 filtrates showed positive cytotoxic effect on AGMK and RMK cells, respectively. Another 630 stool specimens were tested on McCoy and Vero cells only. Of these stool filtrates, 70 were positive and 560 were negative with both cell lines, which thus gave 100% agreement. Vero cells can be used interchangeably with McCoy cells for the detection of C. difficile toxin in stool filtrates.

Identification of Chlamydia trachomatis by direct immunofluorescence applied in specimens originating in remote areas.

The efficacy of the MicroTrak (Syva Co., Palo Alto, Calif.) direct immunofluorescence test for the detection of Chlamydia trachomatis was compared with cell culturing of fresh specimens obtained from patients attending a clinic on sexually transmitted disease and of frozen specimens delayed in transit from urban or remote physicians' offices and clinics. Direct immunofluorescence testing detected C. trachomatis more frequently than culturing of the same specimens when transit caused a delay in culturing.

Detection of Clostridium difficile toxin with McCoy cell monolayers and cell suspensions and comparison with HeLa cell assay.

McCoy cell monolayers were compared with HeLa cell monolayers for the detection of Clostridium difficile toxin in 301 stool samples. Tests were positive (greater than or equal to 1/100 dilution) in 83 and 81 specimens tested with McCoy and HeLa cell monolayers, respectively. McCoy cell suspensions were compared with HeLa cell monolayers in 532 stool filtrates. Overall, 90 positive specimens were within one dilution and 432 filtrates were negative with either test, giving a correlation coefficient of r = 0.98. McCoy cell monolayers or suspensions may be a satisfactory substitute for the detection of C. difficile toxin in clinical specimens.

Radioimmunodiffusion technique for determining diphtheria antitoxin.

A radioimmunodiffusion technique for detecting low levels of diphtheria antitoxin was developed. Diphtheria toxoid was labelled with 125I to facilitate detection of lines of precipitation by the use of X-ray film, the lower limit of detection being 0.001 unit per millilitre of diphtheria antitoxin.

Neisseria gonorrhoeae identification in carbohydrate medium containing guinea pig serum.

Clinical isolates of Neisseria gonorrhoeae from Manitoba were tested for their carbohydrate degradation activity in Cystine Trypticase Agar (C.T.A) medium, Mueller-Hinton Agar and guinea pig serum agar. Each isolate was tested using 2 carbohydrates (e.g. glucose and maltose) in the above three media. Out of 661 isolates tested, only 80% were positively identified in C.T.A. medium. Mueller-Hinton agar allowed 88% identification while guinea pig serum agar yielded 100% identification. In a second series of experiments, 102 cultures of N. gonorrhoeae were used to compare Flynn & Waitkins medium with guinea pig serum agar. Only 91 of these were identified with Flynn and Waitkins medium while guinea pig serum agar identified all the 102 isolates. Guinea pig serum provides adequate growth of fastidious N. gonorrhoeae essential for detecting specific enzymes. Since guinea pig serum does not contain maltase activity, it does not interfere with the biochemical activities tested. Guinea pig serum agar is easy to prepare, does not require a heavy inoculum and gives definite color change in the medium.