Antibacterial activity of sucralfate and bismuth subsalicylate in simulated gastric fluid

Inhibition of bacterial adherence on the surface of stents and bacterial growth in bile by bismuth dimercaprol

Bacterial infection and biofilm formation on the surface of biliary stents is believed to be one of the main factors in stent occlusion. This study explored the role of the new reagent, bismuth dimercaprol, in preventing bacterial adherence and bacterial biofilm formation on the surface of biliary stents. Sterile porcine bile preparations, infected separately with Escherichia coli, Klebsiella pneumoniae, Enterobacter, and Enterococcus, were used as the perfusion media in an in vitro perfusion system. The bacterial growth in the media and the bacterial adherence on the surface of stents were tested when different concentrations of bismuth dimercaprol were used in the perfusion media. BisBAL (5 microM) did not inhibit the growth of any of the tested bacterial species. It did, however, significantly decrease the amount of bacteria adhering to the surface of stents for all bacterial strains except Escherichia coli. Bismuth dimercaprol (20 microM) significantly inhibited the growth of Escherichia coli, Klebsiella pneumoniae, and Enterobacter and, thereby, significantly decreased the amount of these bacteria adhering to the surface of stents. The unique bactericidal and anitbiofilm activities of bismuth thiols might contribute to delaying the process of biliary stent occlusion if the effective concentrations of bismuth thiols could be delivered to the target sites. The feasibility of this application of bismuth thiols deserves further investigation.

Influence of intravenously administered ciprofloxacin on aerobic intestinal microflora and fecal drug levels when administered simultaneously with sucralfate

Ciprofloxacin, when given intravenously (i.v.), is secreted in significant amounts via the mucosa into the intestinal lumen. Sucralfate inhibits the antimicrobial activity of ciprofloxacin. The effect of combined therapy on the intestinal flora was investigated in 16 healthy volunteers. They were randomly assigned to two groups. Group A received 2 g of sucralfate orally three times a day for 7 days and 400 mg of ciprofloxacin i.v. twice a day (b.i.d.) starting 3 days after the sucralfate administration began. Group B was given only 400 mg of ciprofloxacin i.v. b.i.d. for 4 days. A total of 9 stool samples were collected from each subject beginning the week before ciprofloxacin was administered and on days -1, 1, 2, 3, 4, 7, 9, and 10 or 11 after commencement of the infusion period. The aerobic fecal flora was determined by standard microbiological methods. Measurements of fecal ciprofloxacin levels were based on high-performance liquid chromatography. Counts of bacteria of the family Enterobacteriaceae decreased in all subjects and were below 10(2) CFU/g in eight of eight subjects (group A) and six of eight subjects (group B) on day 4, but they returned to normal in all but one subject (group A) 10 days after the last infusion. The decreases in levels of bacteria of the family Enterobacteriaceae were not significantly different in groups A and B (Kaplan-Meier test). Staphylococci and nonfermenters responded variably, enterococci and lactobacilli remained unchanged, and candida levels increased transiently in four subjects (two in each group). Maximum fecal drug levels ranged from 251 to 811 microg/g. No significant difference could be found between the two groups. The i.v. application of ciprofloxacin eliminates intestinal bacteria of the family Enterobacteriaceae in a rapid and selective manner. This effect is not affected by simultaneous oral application of sucralfate.

Antibacterial activity of sucralfate versus aluminum chloride in simulated gastric fluid

Studies have previously demonstrated that sucralfate possesses intrinsic antibacterial activity. This study was designed to indirectly assess whether aluminum is the active antibacterial component of sucralfate and to further evaluate factors that may influence this agent's antibacterial activity. Utilizing an in vitro model, the antibacterial activity of sucralfate, an equivalent quantity of aluminum in the form of aluminum chloride, and a control were compared. In addition, the influences of bacterial species (Enterobacter cloacae and Pseudomonas aeruginosa), time (0-24 h) and environmental pH (3,5,7) on the agents' antibacterial activities were evaluated. Equivalent quantities of aluminum, as either sucralfate or aluminum chloride, were added to two of three flasks containing approximately 10(5) cfu/ml of bacteria in pH-adjusted simulated gastric fluid. The third flask served as a control. Samples were obtained over 24 h, diluted and subcultured onto agar plates. The experiments demonstrated that bacterial growth was influenced by pH, time and treatment (aluminum chloride or sucralfate). Regardless of pH or bacterial species, bacterial death occurred within 20 min following the addition of aluminum chloride. In contrast, bacterial death following the addition of sucralfate was more variable and appeared to be pH dependent. In conclusion, sucralfate and aluminum chloride both possess antibacterial activity, even at pH values that normally support bacterial growth in gastric fluid. Although differences in the antibacterial activity of the two agents may in part be related to drug-induced changes in pH, these differences also support data suggesting that aluminum release from sucralfate is incomplete and is dependent on pH.

Antibacterial activity of sucralfate against Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa in batch and continuous culture

The antibacterial effect of varying concentrations of sucralfate was studied on Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus grown in both agitated batch and continuous culture. The minimum inhibitory concentrations estimated with the two methods were in close agreement, ranging from 5 to 15 mg sucralfate/ml, concentrations easily attainable in gastric juice after a standard adult dose. Batch culture results indicated a dose-dependent effect. This study provides further evidence for an antibacterial effect by sucralfate against a range of species associated with respiratory tract infection in ventilated patients.

Incidence of pneumonia in mechanically ventilated patients treated with sucralfate or cimetidine as prophylaxis for stress bleeding: bacterial colonization of the stomach

Retrograde colonization of the oropharynx from the stomach by microaspiration of gastric fluid is a recently recognized phenomenon associated with increased gastric pH that may result in pneumonia during ventilation therapy. In a prospective study we investigated 104 mechanically ventilated patients in the intensive care unit who were receiving sucralfate (n = 49) or cimetidine (n = 55) for stress ulcer prophylaxis. The incidence of pneumonia was 45.5% (25 patients) in the cimetidine group and 26.5% (13 patients) in the sucralfate group (95% confidence interval 0.98 to 6.97; odds ratio 2.61; p = 0.0549). Mortality rates were 18.4% (9 patients) in the sucralfate group versus 25.5% (14 patients) in the cimetidine group (p = 0.48). The mean pH values of gastric aspirates were significantly lower in patients treated with sucralfate than in patients receiving cimetidine (p = 0.044). The number of colony-forming units of Enterobacteriaceae in gastric aspirates was also significantly lower in the sucralfate group (p = 0.0037).

Binding and killing of bacteria by bismuth subsalicylate

Bismuth subsalicylate (BSS) is a compound without significant aqueous solubility that is widely used for the treatment of gastrointestinal disorders. BSS was able to bind bacteria of diverse species, and these bound bacteria were subsequently killed. A 4-log10 reduction of viable bacteria occurred within 4 h after a 10 mM aqueous suspension of BSS was inoculated with 2 x 10(6) Escherichia coli cells per ml. Binding and killing were dependent on the levels of inoculated bacteria, and significant binding but little killing of the exposed bacteria occurred at an inoculum level of 2 x 10(9) E. coli per ml. Intracellular ATP decreased rapidly after exposure of E. coli to 10 mM BSS and, after 30 min, was only 1% of the original level. Extracellular ATP increased after exposure to BSS, but the accumulation of extracellular ATP was not sufficient to account for the loss of intracellular ATP. The killing of bacteria exposed to BSS may have been due to cessation of ATP synthesis or a loss of membrane integrity. Bactericidal activity of BSS was also investigated in a simulated gastric juice at pH 3. Killing of E. coli at this pH was much more rapid than at pH 7 and was apparently due to salicylate released by the conversion of BSS to bismuth oxychloride. It is proposed that the binding and killing observed for BSS contribute to the efficacy of this compound against gastrointestinal infections such as traveler's diarrhea.

Hospital-acquired pneumonia: overview of the current state of the art for prevention and control

Hospital-acquired pneumonia affects at least 250,000 patients in U.S. acute care institutions each year and is associated with a crude mortality of approximately 30%. Cases occur at a rate of 0.5-1 per 100 admissions, constituting 10-15% of all nosocomial infections and directly accounting for approximately one-third (10%) of the total mortality. It is likely, therefore, that nosocomial pneumonia represents an important cause of death. No recent large-scale study has systematically examined the true bacterial etiology of hospital-acquired pneumonia utilizing reliable techniques that bypass the oral flora. In the absence of such data, the current approach to therapy based on the examination of sputum is not optimal. Studies that focus on pathogenesis point to the stomach as an important reservoir of infecting organisms. Recent studies suggest that rates of pneumonia can be reduced either by selective decontamination of the digestive tract with antibiotic prophylaxis or by utilizing stress ulcer prophylaxis, which maintains normally low gastric pH. It seems that the time is propitious to examine prehospital determinants of nosocomial infection, with the goal of further preventing these life-threatening events in the hospital.