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Oral dose and faecal concentration of antibiotics during antibiotic decontamination in mice and in a patient.

In both mice and one patient, a similar correlation was found between the oral dose of a ;nonabsorbable' aminoglycoside antibiotic selected for antibiotic decontamination of the digestive tract and the resultant faecal concentration. In mice, absorption of the orally-given antibiotics could only be demonstrated in animals treated with extremely high doses of 1440 mg. per kg. body weight per day. Evidence of absorption of gentamycin was found to occur in a patient after doses as low as 70 mg. per kg. per day.

Administration, Oral↗

Investigation of the immune status of mice during and following selective decontamination of the digestive tract.

Selective decontamination of the digestive tract (SDD) employs oral antibiotics to eliminate aerobic Gram-negative bacilli while retaining the anaerobic flora. A combination of SDD and parenteral cefotaxime has recently been reported to strikingly reduce the incidence of infection in patients treated in an intensive therapy unit. The present study describes the effects of SDD and of cefotaxime on the immune response of mice to protein antigens. The in vivo cellular response to ovalbumin and sheep red blood cells was unchanged. However, SDD appeared to decrease the in vitro mitogenic response of spleen cells to phytohaemagglutinin, and cefotaxime similarly affected the response to Concanavalin A. The antibody response to sheep red blood cells was increased in the period after discontinuation of SDD. The antibody response was otherwise not affected. These results indicate that SDD is unlikely to have adverse effects on the immune response to protein antigens.

Amphotericin B↗

Selective decontamination of the digestive tract in intensive care.

Nosocomial infection in intensive care unit (ICU) practice is a common problem and is associated with abnormal carriage of Gram-negative aerobic bacilli in the gastrointestinal tract, resulting in endogenous infections. Selective decontamination of the digestive tract (SDD) is a regimen aimed at preventing or eradicating this abnormal carriage. A large number of trials examining SDD in ICU practice have been published, the vast majority showing a significant reduction in the incidence of nosocomial, Gram-negative infection. However, the impact on morbidity and mortality is much less certain. A recent meta-analysis has suggested a 10-20% reduction in mortality (3-6% absolute difference) with SDD. A discussion of these results is presented together with potential criticisms of SDD.

Anti-Bacterial Agents↗

Selective decontamination in bone marrow transplant recipients.

Patients undergoing bone marrow transplantation become immunocompromised for various reasons. Deep granulocytopenia, induced by conditioning (chemotherapy and total body irradiation), renders the patient at risk for serious bacterial and fungal infections. Our strategy for prevention of these infections by selective decontamination (SD) is the result of more than 15 years of clinical experience and research. The combination of antibiotics, used as standard SD (neomycin, polymyxin B, pipemidic acid and amphotericin B), with the application of local antimicrobial agents eliminates aerobic Gram-negative rods, Staphylococcus aureus and Candida spp. from the mucosal surfaces of the digestive tract, while the majority of the anaerobic flora persist and support colonization resistance (CR). The antibiotics used either are not resorbed or do not yield therapeutic serum concentrations. Antibiotics which induce therapeutic serum concentrations, such as ciprofloxacin and cotrimoxazole, are only used for SD on a limited scale. When Gram-negative rods persist despite intake of the standard regimen, ciprofloxacin is given until these persisting rods are eliminated. If the patients cannot swallow the oral regimen, i.v. cotrimoxazole is given temporarily. Streptococcal infections are prevented by the i.v. administration of penicillin for 14 days starting on the first day after cytotoxic treatment (conditioning for bone marrow transplantation). The combination of SD and systemic prophylaxis has been shown to be adequate; the major problem then remaining is a relatively mild catheter-associated infection with coagulase-negative staphylococci.

Animals↗

The effect of selective decontamination of the digestive tract with the addition of systemic cefotaxime on the aerobic faecal flora of mice.

The administration per-orally to mice of the non-absorbable antibiotics polymyxin E, tobramycin and amphotericin B resulted in the elimination of detectable aerobic gram-negative rods from the faecal flora without affecting the total viable aerobic count. The addition of parental cefotaxime to the regime caused a fall in the number of aerobic lactobacilli and an increase in the number of enterococci. The rise was associated with the translocation of viable enterococci to the mesenteric lymph nodes and the spleen. The changes induced by cefotaxime were reversed when the antibiotic was withdrawn. Following withdrawal of all antibiotics the total aerobic faecal flora increased to above normal levels, but there was no associated diarrhoea. Attempts to implant exogenous enterobacteria into the digestive tract resulted in only low level colonization both in treated mice and in control mice. These results may have implications for the use of this antibiotic regime for selective decontamination of the digestive tract in humans, particularly those who are immunocompromised.

Animals↗

Decontamination of Bacillus anthracis on Gruinard Island?

In experiments on Gruinard Island 40 years ago small bombs containing spores of Bacillus anthracis were suspended from a gantry and detonated, producing widespread contamination of the island's surface. Recently, analysis of soil samples has shown that the area where the spores can now be detected is small enough to be considered for decontamination. We investigated the effect of treating the soil with sporicidal chemicals, namely, potassium permanganate, formaldehyde, glutaraldehyde, Cidex ('activated' glutaraldehyde, Surgikos), dodecylamine and peracetic acid.

Bacillus anthracis↗

A comparison of decontamination methods used for dental burs.

OBJECTIVES: This study investigated the bacterial and fungal contamination of used dental burs. A novel assay system for comparison of efficacy of pre-sterilisation cleaning techniques for dental burs was used to evaluate manual scrubbing, enzymic agents and washer-disinfectors. METHODS: Thirty dental burs contaminated during cavity preparation were analysed for micro-biological total viable counts and species of bacteria and fungi present. To simulate clinically contaminated burs, a culture of Streptococcus sanguis NCTC 7863 was used to inoculate unused dental burs, alone and combined with blood, saliva or a mixture of blood and saliva. Contaminated burs were subjected to six pre-sterilisation cleaning techniques and the log reduction in contamination achieved by each method was assessed. RESULTS: The microbial count from used dental burs ranged from 0 to 6.92 x 10(4) CFU ml(-1). Many potentially pathogenic species were identified. The decontamination assay demonstrated that autoclaving alone was not sufficient to sterilise dental burs. Manual scrubbing in air was less efficacious than manual scrubbing under water (p<0.001). The most effective method of pre-sterilisation cleaning for dental burs was a washer-disinfector. CONCLUSIONS: Enzymic agents are suitable for soaking contaminated dental burs immediately after use. Washer-disinfectors are recommended as the method of choice for pre-sterilisation cleaning of contaminated dental burs.

Air↗

Nitric oxide and the hyperdynamic circulation in cirrhosis: is there a role for selective intestinal decontamination?

Abnormal vascular tone is responsible for many of the complications seen in cirrhosis making the identification of the pathophysiology of abnormal dilatation a major focus in hepatology research. The study of abnormal vascular tone is complicated by the multiple vascular beds involved (hepatic, splanchnic, peripheral, renal and pulmonary), the differences in the underlying cause of portal hypertension (hepatic versus pre-hepatic) and the slow evolution of the hyperdynamic state. The autonomic nervous system, circulating vasodilators and abnormalities in vascular smooth muscle cells (receptors, ion channels, signalling systems and contraction) have all been implicated. There is overwhelming evidence for an overproduction of NO (nitric oxide) contributing to the peripheral dilatation in both animal models of, and in humans with, cirrhosis and portal hypertension. This review focuses on the proposal that endotoxaemia, possibly from gut-derived bacterial translocation, causes induction of NOS (NO synthase) leading to increased vascular NO production, which is the primary stimulus for the development of vasodilatation in cirrhosis and its accompanying clinical manifestations. The current controversy lies not in whether NO production is elevated, but in which isoform of NOS is responsible. We review the evidence for endotoxaemia in cirrhosis and the factors contributing to gut-derived bacterial translocation, including intestinal motility and permeability, and finally discuss the possible role of selective intestinal decontamination in the management of circulatory abnormalities in cirrhosis.

Anti-Bacterial Agents↗

Investigations into possible alternative decontamination methods for Salmonella enteritidis on the surface of table eggs.

Investigations into various alternative techniques for decontamination of the surfaces of artificially contaminated shell eggs were carried out. Ionized air, exposure to ozone in a dry atmosphere and use of a commercial herbal antibacterial product were not effective. Application of ozone in a humid environment was only partially effective but a commercial ionized water anolyte was highly effective in eliminating Salmonella from egg surfaces.

Animals↗

Selective decontamination of the digestive tract: a life saver.

Selective decontamination of the digestive tract (SDD), a strategy designed to prevent or minimize the impact of infection by potentially pathogenic micro-organisms in critically ill patients requiring long-term mechanical ventilation, comprises four component protocols, aiming to control the three types of infection occurring in such cases: (i) a parenteral antibiotic, cefotaxime, administered for a few days to prevent primary endogenous infections typically occurring 'early'; (ii) the topical antimicrobials polymyxin E, tobramycin and amphotericin B employed throughout the stay in the intensive care unit to prevent secondary endogenous infections tending to develop 'late'; (iii) a high standard of hygiene to prevent exogenous infections that may occur throughout the stay in the intensive care unit; (iv) surveillance samples of throat and rectum to distinguish between these three types of infection, to monitor the compliance and the efficacy of the treatment, and to detect the emergence of resistance at an early stage. A recent, rigorous, meta-analysis examining 33 randomized SDD trials involving 5727 patients demonstrated a significant reduction in overall mortality (20%) and in the incidence of respiratory tract infections (65%); conclusive evidence that SDD saves the lives of critically ill patients and confirmation that SDD is now an evidence based medicine manoeuvre. This same meta-analysis found no instance of the emergence of resistance or of associated superinfections and/or outbreaks in any of the 33 studies during a period extending upwards of 10 years. By the criterion of cost-per-survivor, four recent randomized trials showed that patient survival is improved more cheaply by employing SDD than by the traditional approaches.

Antibiotic Prophylaxis↗

Gut decontamination of critically ill patients reduces Helicobacter pylori acquisition by intensive care nurses.

The prevalence of Helicobacter pylori is increased in healthcare workers and in intensive care nurses. Exposure to H. pylori from gastric secretions and faeces are probably the main sources of transmission to healthcare workers. Routine use of selective decontamination of digestive tract (SDD) in an intensive care unit suppresses H. pylori in critically ill patients. It was questioned whether this suppression and the subsequent decreased exposure to H. pylori for intensive care nurses would lead to a lower prevalence of H. pylori infection. Helicobacter pylori infection prevalence in intensive care nurses from a unit routinely using SDD (group I) was compared to that of nurses from a unit not using SDD (group II). Heathcare workers from other departments of the hospital where no SDD was used (group III) served as a control group. Persons using proton pump inhibitors were excluded. Helicobacter pylori was detected by Laser Assisted Ratio Analyser(13)C-urea breath test (UBT) and serology. This could not be performed in three out of 64 in group I, five out of 55 in group II and five out of 55 in group III (total UBTs = 169). The prevalence of H. pylori infection was 11% (7/61) in group I and 25.5% (14/50) in group II (P= 0.027). In group III, the prevalence of H. pylori infection was 16% (8/45), which was not significantly different from both group I and II. Sero-prevalence in group I was 18.6%, 27% in group II (ns) and 24% in group III. Mean age in the three groups was 35.9, 37.8 and 36.6 years, respectively (ns). In conclusion, the prevalence of H. pylori infection among intensive care nurses is lower in nurses from a unit using SDD compared to a non SDD-using unit. Acquisition of H. pylori by transmission from critically ill patients appears to be diminished through SDD use.

Adult↗

The effect of selective bowel decontamination on the pharmacokinetics of mycophenolate mofetil in liver transplant recipients.

Mycophenolate mofetil (MMF) is a prodrug immunosuppressant with a high oral bioavailability. Enterohepatic cycling of a glucuronide derivative of MMF contributes substantially to the bioavailability, but is dependent on bacterial deglucuronidation by intestinal flora. This study aims to determine whether an antibiotic regimen with activity against such organisms reduces the bioavailability of MMF by impairing enterohepatic cycling. In a prospective trial, 6 liver transplant recipients were administered MMF and a 21-day antibiotic regimen for selective bowel decontamination (SBD). Time-concentration profiles of the pharmacologically active metabolite, mycophenolic acid (MPA), were obtained during and after the SBD regimen. The bioavailability of MPA was reduced during compared with after the regimen (14.5 +/- 3.5 v 21.1 +/- 9.8 mg. h/mL; P =.07). The most pronounced contribution to this reduction was observed from 6 hours onward (2.4 +/- 1.4 v 5.6 +/- 4.4 mg. h/mL; P <.05). The presence of secondary maxima in the time-concentration profiles of MPA after, but not during, SBD indicates that enterohepatic cycling may be inhibited during SBD and restored afterward. Enterohepatic cycling may contribute 7% to 54% (mean, 29%) of the bioavailability of MPA. We conclude that the bioavailability of MMF may be reduced when SBD is used, and the reduction is likely to result from the interruption of enterohepatic cycling. This mechanism should be taken into consideration not only during SBD, but in any clinical setting combining MMF and broad-spectrum antibiotics.

Adult↗

[Pneumonia prevention in long-term mechanically ventilated patients: selective skin decontamination according to Stoutenbeek or prevention of colonization according to Unertl? A prospective randomized comparison of both treatments].

In a prospective randomised study, the effects of two different colonisation prophylaxis techniques on colonisation and pulmonary infection were investigated in 40 critically ill patients with long-term ventilatory support (greater than or equal to 4 days). 20 patients were selectively decontaminated with 4 x 100 g polymyxin E, 4 x 80 mg tobramycin and 4 x 500 mg amphotericin B, administered through the gastric tube and with an antimicrobial sticky paste in the oropharynx (group I). 20 patients received 50 mg of polymyxin B and 80 mg of gentamicin dissolved in 10 ml of 0.9% saline at 6 h intervals into nose, oropharynx and stomach as well as 300 mg of amphotericin B in the oropharynx only (group II). All patients received cefotaxime systemically in the first 3 days. In group I gram-negative aerobic bacteria in the pharynx decreased from 35% to 0%, in group II from 40% to 10% and in the rectum from 80% to 61% (10% in the second week) in Group I and from 100% to 73% (33% in the second week) in group II. The decrease in gram-negative microorganisms was accompanied by an increase in the frequency of Staphylococcus epidermidis. In group I, two patients developed pneumonia and two patients urinary tract infections, in group II two patients suffered from pneumonia and 3 patients urinary tract infections. Both regimes are effective methods of prophylaxis for lowering colonisation with gram-negative aerobic bacteria and the frequency of pneumonia in patients requiring long-term mechanical ventilation. A possible selection of gram-positive bacteria must be appropriately monitored.

Adult↗

Acute poisoning emergencies. Resolving the gastric decontamination controversy.

As in all medical emergencies, in acute poisoning the cornerstone of management is good supportive care. Aggressive support of the cardiovascular, respiratory, and central nervous systems, along with appropriate gastric decontamination, greatly reduces morbidity and mortality and improves patient outcome. Ipecac is generally reserved for home use, where it can be given to induce emesis immediately after ingestion of toxins, and it is given only in cases of mild or moderate toxicity. Activated charcoal should replace ipecac in the emergency department for cases of mild or moderate toxicity. Gastric lavage and administration of activated charcoal should be considered in cases with life-threatening potential. A cathartic should be considered after activated charcoal has been administered, but only in cases where it will not have a detrimental effect.

Acute Disease↗

Fumonisin-contaminated maize: physical treatment for the partial decontamination of bulk shipments.

Ten maize samples, randomly selected from a bulk shipment imported into South Africa, were characterized by a wide distribution in particulate size. Following fractionation by sieving through a 3 mm screen, the 'kernels' (fractions > or = 3 mm) corresponding to between 80.0 and 95.3% of the samples by mass, were contaminated with total fumonisin levels of between 530 and 1890 ng/g. Conversely, those fractions termed 'fines' (< 3 mm) had significantly higher total fumonisin concentrations of between 12,340 and 27,460 ng/g, and accounted for between 4.7 and 20.0% of the samples by mass. The data indicated that removal of the 'fines' resulted in overall reductions in total fumonisin levels of between 26.2 and 69.4%. It is suggested that initial removal of 'fines' from bulk shipments of maize, prior to further processing, could be considered as a preliminary fumonisin-decontamination procedure.

Chromatography, High Pressure Liquid↗

Pesticide decontamination from fabric by laundering and simulated weathering.

This laboratory study investigated the effectiveness of selected detergents and the phenomenon of simulated environmental conditions (weathering) on the removal of a commercial-grade mixture of parathion and methyl parathion from a three-layer laminated fabric. The weathering treatment consisted of exposure and non-exposure to simulated environmental conditions of heat, light, and humidity. Contaminated fabric samples were laundered in one of three detergents containing an anionic, a nonionic, and a combined anionic and nonionic surfactant. The test fabric, a three-layer fabric containing an impermeable microporous film laminated between two layers of nylon, was pipette-contaminated with 400 microliters of field strength pesticide solution and allowed to dry. Half of the contaminated samples were weathered in an Atlas Fade-Ometer. All of the contaminated samples were subsequently laundered in a Launder-Ometer. Percent of pesticide residue was determined by gas chromatography. Weathering did significantly reduce both parathion and methyl parathion residues remaining in the test fabric. No statistically significant difference was found among the three detergents. High amounts of both parathion and methyl parathion remained in the test fabric after weathering and laundry treatments. Before the test fabric can be recommended for use in protective garments further research is needed to develop more effective decontamination procedures.

Detergents↗

[Lead and zinc recovery by adsorption on peat moss during municipal incinerator used lime decontamination].

The objective of this research was to evaluate the efficiency of peat moss for lead and Zn recovery from alkaline leachates (pH 11.5) produced during decontamination of municipal incinerator fly ash. Tests carried out with peat moss columns (density of 0.13 g m l(-1)) gave very high removal yields for lead (98.9 to 100%) and Zn (98.4 to 99.8 %). The initial metal concentrations in the leachates were 126 to 138 mg Pb l(-1) and 14.4 to 23.5 mg Zn l(-1). The columns were fed using two rates (20 and 40 ml min(-1)), which correspond respectively to 17.6 and 8.8 min as contact time on peat moss. Adsorption efficiencies of 16 to 18 mg Pb g(-1) and 1.7 to 3.2 mg Zn g(-1) have been measured during this fly ash leachate treatment study. The adsorbed toxic metals can be desorbed using a chlorhydric acid solution. The peat moss can be regenerated and reused for several adsorption cycles without loss of the lead and Zn adsorption efficiencies.

Adsorption↗

Microbial translocation and impairment of mucosal immunity induced by an elemental diet in rats is prevented by selective decontamination of the digestive tract.

OBJECTIVE: To assess the effect of selective decontamination of the digestive tract (SDD) on intestinal secretory immunoglobulin A (sIgA) concentrations in a model of intestinal bacterial overgrowth and bacterial translocation induced by an elemental diet in rats. DESIGN: Laboratory study. SETTING: University hospital, Germany. MATERIAL: 45 specific pathogen free female Crl:CD(R) BR rats. INTERVENTIONS: For 7 days, 3 groups of rats were fed orally with standard chow (n = 15), total parenteral nutrition solution (ORAL-TPN, n = 15), or ORAL-TPN plus tobramycin (20 mg/L) and polymyxin E (25 mg/L) (ORAL-TPN + SDD). MAIN OUTCOME MEASURES: Bacterial translocation to mesenteric lymph nodes (MLN), numbers of gram negative enterobacteria and total aerobic bacteria in the caecum, and intestinal concentrations of sIgA. RESULTS: The incidence of bacterial translocation was significantly increased in the group given ORAL-TPN (8/15, 53%) compared with the group given chow (1/15, 7%, p < 0.01). Supplementation of ORAL-TPN with SDD reduced translocation to 0/15. The ORAL-TPN group had a pronounced overgrowth of aerobic bacteria in the caecum, mainly by gram negative enterobacteria, which was prevented by the SDD. The concentrations of intestinal sIgA were significantly reduced in the ORAL-TPN group. SDD resulted in both the soluble and insoluble sIgA fractions in the gut being within the reference ranges. CONCLUSION: SDD prevents gram negative caecal overgrowth and translocation to MLN in rodents fed on ORAL-TPN. The significantly reduced mucosal immunity caused by ORAL-TPN alone is restored by SDD, although one might have expected a further reduction in sIgA concentrations with lower microbial populations than in the ORAL-TPN group. Not only does SDD not seem to affect the mucosa associated immune system adversely, but also depressed mucosal immunity was restored.

Administration, Oral↗