Comparison between moist swab and tissue biopsy methods for quantitation of bacteria in experimental incisional wounds.

The relationship between tissue-associated and wound fluid-associated levels of bacteria in closed, healing experimental incisional wounds seeded with Escherichia coli was examined in 200 rats. Tissue specimens and moist swab specimens were taken simultaneously and cultured by a single plate serial dilution method. Colony counts of approximately 10(5) bacteria/gm of tissue were found to be equivalent to colony counts of 10(3) bacteria/ml of specimen obtained on a moist swab. Moist swab sampling of an incisional wound therefore offers a direct and simple method of ascertaining infection (defined by others as greater than 10(5) bacteria/gm of tissue). Moist swab sampling obviates the necessity of surgical manipulation of the patient and subsequent weighing and grinding of tissue in the laboratory.

Microbial flora of the diseased stomach at resection.

The relation of microbial flora in stomach contents and stomach wall was examined in paired specimens from 10 surgical patients and in specimens of wall from 10 additional patients. The flora of both contents and wall were similar. Paired specimens from five patients contained the same kinds of bacteria. Paired specimens from these patients were sterile. Contents from two patients contained bacteria, but the wall was sterile. Microorganisms isolated were streptococci, lactobacilli, bifidobacteria, bacteroides, staphylococci yeast, and coliforms. Bacterial counts ranged from 0 to 10(7.5) per ml or g in both contents and tissue. Survey of the literature shows that most specimens from patients with gastric ulcers or gastric malignancies are positive for bacteria, while only about 60% of specimens from patients with duodenal ulcers are positive.

Development of tetracycline-resistant Staphylococcus aureus in gnotobiotic mice.

Germ-free mice were colonized with a pigmented, tetracycline-sensitive strain of Staphylococcus aureus and maintained in flexible plastic isolators. Treatment of the gnotobiotic mice with oral tetracycline (20 mg/ml) resulted in the development of staphylococci resistant to tetracycline (5 mug/ml or higher). Resistant staphylococci did not appear in feces until several days after exposure of mice to the antibiotic and persisted for as long as specimens were collected (64 days subsequently). Resistance developed after a single exposure of gnotobiotes to antibiotic. Resistant staphylococci were present in the intestinal tracts of mice at counts of 10(3) per g of contents, whereas sensitive organisms coexisted at counts of 10(5) to 10(11) per g. Resistant staphylococci were isolated only from treated mice and not from untreated mice in adjacent cages. Initial colonization of germ-free mice with sensitive staphylococci interfered with subsequent colonization by resistant staphylococci and provided an example of bacterial interference. Resistance to tetracycline was not associated with resistance to chloramphenicol, penicillin, ampicillin, erythromycin, streptomycin, or kanamycin. Hydrolysis of gelatin was the only biochemical characteristic in which isolates varied but was not correlated with resistance to tetracycline or pigmentation of colonies. A nonpigmented, gray variant of S. aureus appeared in all specimens after colonization with the original, pigmented strain. Only the nonpigmented strain was obtained from gnotobiotes colonized with the nonpigmented variant. Contact between bacteria and antibiotic in the intestinal tract of gnotobiotes was considered to be essential for the development of tetracycline-resistant staphylococci.

Ultaviolet red fluorescence of Bacteroides melaninogenicus.

Under longwave ultraviolet light, Bacteroides melaninogenicus fluoresced vivid red on blood-agar plates as well as in chronic cutaneous ulcers and purulent drainage.