A study of 78 patients with cystic fibrosis of the pancreas was carried out to determine whether gelatin-liquefying bacteria may be responsible for gelatin liquefaction of gelatin film by feces and duodenal juice. In addition, the records of 254 children with cystic fibrosis of the pancreas were reviewed relative to the incidence of apparently false positive gelatin film tests. The following data were obtained:

1. Fecal specimens of 48 out of 78 patients yielded positive gelatin film tests. Only 9 of these 48 specimens were positive in a dilution of 1:25 or higher, but 33 gave positive tests in a dilution of 1:10. Likewise, a review of 254 charts of proved cases of cystic fibrosis revealed that of 131 tests on 59 patients, 71 or 54% were positive.

2. Gelatin-liquefying bacteria were present in the feces of 44 out of 45 patients whose stool specimens gave a positive gelatin film test and which also were examined bacteriologically, but in only 2 out of 28 whose feces gave negative gelatin film tests.

3. Treatment with penicillin may be associated with an increase in the percentage of positive gelatin film tests. Of 42 patients whose feces were obtained prior to or without penicillin therapy only 4 gave positive gelatin film tests, whereas the feces of 55 of 80 patients who had received treatment with penicillin did so.

4. Soy bean trypsin inhibitor partially or completely prevented gelatin liquefaction by fecal specimens of patients with cystic fibrosis of the pancreas only if the latter were diluted to 1:5 or less, possibly indicating the presence of small amounts of trypsin. This titer of soy bean trypsin inhibitor-neutralizable enzyme is far below normal.

5. Gelatin-liquefying bacteria were found in all 10 of the cultured duodenal juice specimens which gave apparently false positive gelatin film tests in a dilution of 1:10 or higher.

6. The incidence of gelatin-liquefying bacteria in the throat and feces of patients giving apparently false positive fecal gelatin film test was far greater in the penicillin-treated patients than in untreated patients.

7. The importance of the apparently false positive gelatin film test is discussed and modifications of this test are outlined which make for greater reliability.

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