The Fate Of Ingested Pseudomonas Aeruginosa In Normal Persons

Abstract

It is possible that pseudomonas in the bowel come from ingested food, but it is not known whether ingested pseudomonas will establish themselves in the bowel of normal people, what numbers if ingested will be detectable in the faeces and for how long they will remain in the bowel. The experiments described here were performed in an attempt to answer these questions. METHODS Volunteers. These were two men and one woman who were members of the laboratory staff. Their ages were between 29 and 35 and they had no known abnormality of the gastrointestinal tract. During the period of the investigation the volunteers ate no cold food at midday and all cold food and drinks taken at home were sampled for the presence of pseudomonas. On three occasions one of the volunteers had a 4-day course of oral ampicillin, 250 mg being taken 4 times a day, commencing 5 hr before the ingestion of the organisms. Strains. The doses of pseudomonas to be ingested were prepared from either laboratory strains or fresh isolates. The sources, the phage-types and serotypes of the seven strains used are shown in table I. Preparation of strains of pseudomonas for ingestion. The strains were grown in nutrient broth (Oxoid) at 37°C for 5 hr and then either this culture or dilutions of it were added to approximately 200 ml of milk containing 4 ml of aluminium hydroxide gel. The numbers of organisms ingested ranged from 5 x 102 to 2 x 108, determined from surface viable counts of the broth cultures on cetrimide-chloramphenicol plates. The organisms were ingested in the late afternoon approximately 4 hr after the last meal. Composition of the media used. Cetrimide broth: Oxoid nutrient broth no. 2 containing 0.2 mg cetrimide per ml. Cetrimide agar: Oxoid nutrient agar containing 0.3 mg cetrimide per ml. Cetrimide-chloramphenicol agar: as for cetrimide agar but with the addition of 2.5 ,ug chloramphenicol per ml. Examination of food. A few grammes of each type of cold food or cold drink eaten during a 24-hr period were pooled and emulsified. The mixture was used to inoculate a cetrimide agar plate and also a tube of cetrimide broth, which was subcultured to cetrimide agar after

Effect of broad-spectrum parenteral antibiotics on "colonization resistance" of intestinal microflora of humans

“…The antibiotics had no apparent influence on the ability of the fed E. coli and P. aeruginosa strains to colonize the intestinal tract ( Table 1). The E. coli strain was detectable in the stools of 14 of 16 antibiotictreated subjects and all 4 of the controls; the duration of elimination was brief, generally 3 to 5 days, but exceeded 1 week in one instance. Similarly, the P. aeruginosa strain was found in the stools of 12 of 16 subjects receiving an antibiotic and 3 of 4 controls; the duration of elimination was quite variable but exceeded 1 week in six instances.…”

“…The E. coli strain was a K-12 C600 nalidixic acid-resistant mutant. The MICs of the drugs in the study for this strain were as follows: aztreonam, 0.5 ,ug/ml; cefoperazone, 0.5 jig/ml; piperacillin, 4 ,ug/ml; and cefoxitin, 8 ,g/ml. The ability of this strain to grow on a medium containing 100 ,ug of nalidixic acid per ml was used for its detection in stools.…”

The Comparative Pathology ofClostridium difficile-associated Disease

“…96,133 The inability of nonindigenous microbes to colonize a host with a fully established flora (colonization resistance) has been well documented by controlled experiments with multiple host and pathogen species. 20,43 The antagonism of normal flora to C. difficile was documented by the suppression of C. difficile infection in vancomycin-treated hamsters when reconstituted with cecal homogenates from conventional animals. 168 A variety of mechanisms may be used by indigenous flora in the exclusion of nonindigenous bacteria, including: elaboration of bacteriocins; depletion of essential nutrients; production of toxic metabolic end products, such as volatile fatty acids (VFAs); competition for adhesion sites; stimulation of peristalsis; induction of immunologic responses; and production of H 2 S and secondary bile acids.…”

Antibiotic treatment and intestinal colonization by Pseudomonas aeruginosa in cancer patients

“…Whether the resistance of the intestine to colonization is due mainly to anaerobes and their products (9) remains controversial (3). In normal subjects, ingestion of lower counts of P. aeruginosa, such as those found in food (13), can, however, result in colonization after treatment with ampicillin (6). It has also been shown in experimental animal models that resistance to colonization by P. aeruginosa can be modified to various extents by erythromycin (1), streptomycin (10), or norfloxacin (11).…”

“…The mortality associated with P. aeruginosa infections in neutropenic patients is high (4) and is higher when initiation of appropriate therapy is delayed (4). P. aeruginosa is detected in the indigenous intestinal floras of only 10% of normal humans (8), and the intestinal floras of healthy noncolonized subjects resist colonization by exogenous strains of P. aeruginosa when the inoculum is lower than 106 living organisms (6). Whether the resistance of the intestine to colonization is due mainly to anaerobes and their products (9) remains controversial (3).…”