Antacid, sucralfate, and prostaglandin e₂ effects on the growth and potential for translocation of pseudomonas aeruginosa, escherichia coli, and staphylococcus aureus in an in vitro gastric simulation

Viable bacteria in the gut of thermally injured patients may be translocated through the gut mucosa, causing widespread infection. Increased flora from optimization of bacterial growth by pH elevation, coupled with the decreased intestinal motility common among patients whose mucosal integrity has been compromised, may increase the incidence of translocation. Gastric pH in these patients is monitored and maintained around pH 6 by various agents to reduce susceptibility to stress ulceration. Whole milk, given as a nutrient source, also raises pH. An in vitro trial simulating gastric fluid under conditions found in patients with burns was conducted to evaluate the growth of commonly ingested bacteria. Bicarbonate buffer containing pepsin and adjusted to pH 2, 4, or 7 with HC1 was dosed with magnesium and aluminum hydroxide antacid (Maalox) (10 ml), sucralfate (Carafate) (0.4 gm), or prostaglandin E₂ (PGE₂) (10 ng) before inoculation with Escherichia coli (3 × 10²organisms), Pseudomonas aeruginosa (3 × 10² organisms), or Staphylococcus aureus (2 × 10¹organisms). Bacterial growth and pH were determined periodically over the 24-hour trial. Milk was added at intervals in half the samples to simulate patient feeding. Maalox increased pH in all samples containing milk (initially pH 2, 4, or 7) to over 7.0 in 2 hours, and increased pH more slowly without milk. Carafate had a moderating effect, increasing pH 2 and pH 4 and decreasing pH 7, with a narrower pH range found in the milk groups. PGE₂ treatments combined with milk also increased pH 2 and pH 4, but slightly elevated pH 7 within 24 hours. Without milk, PGE₂ did not alter pH from initial values. Bacterial growth did not occur during the first 4 hours. At 24 hours, Maalox and Carafate groups without milk still showed no response, whereas bacteria in PGE₂-treated groups had multiplied except in pH 2. Overall, groups with milk were capable of supporting growth, likely a result of both higher pH values and presence of substrate. Both S. aureus and P. aeruginosa responses were limited by Maalox and milk alone and enhanced by Carafate and PGE₂. E. coli, however, grew in all treatments. This observation confirms that seen in cases of translocation, where most bacteria found systemically outside the gut are E. coli.