- Email: [email protected]
Selective decontamination as an infection control measure
Journal
of Hospital
Infection (1991) 17, 241-242
EDITORIAL
Selective
decontamination
as an infection
control
measure Colonization and infection with multiply-resistant aerobic Gram-negative bacilli (AGNB) are frequent problems in long-stay traumatized or immunosuppressed patients in intensive care units (ICUs). Conventional methods of infection control are time consuming, labour intensive and are often restricted to the control of exogenous sources of infection. It is tempting to support the gloomy conclusion that ‘traditional control measures aimed at the prevention of exogenous acquisition of Pseudomonas aeruginosa (and other AGNB) are unlikely to have an impact on the overall incidence of infection and that efforts to prevent infection in patients who are already colonized are necessary’.’ There have been a number of trials highlighting the success of selective decontamination of the digestive tract (SDD) in the prevention of unit-acquired ‘secondary’ endogenous infections following the introduction of the concept by the Groningen group.* Nevertheless, there are a number of controversial issues that remain before the regimen of selective, parenteral and enteral antisepsis (SPEAR) can be accepted. The basis of SDD is to employ non-absorbable agents, the PTA regimen, (polymyxin B, tobramycin and amphotericin B) to eliminate or greatly reduce the number of AGNB whilst retaining the normally predominant (? and protective) anaerobic flora, thus attempting to prevent colonization or overgrowth of drug-resistant strains. In addition, the third generation cephalosporin, cefotaxime was given intravenously for the first few days to treat or prevent infection occurring while the intestinal agents take effect. To date, published studies have identified three patient populations where the effective abolition of the abnormal carrier state by means of SDD has occurred. These include ICU patients with mid-grade (10-19) APACHE II scores, patients undergoing transplantation and patients undergoing oesophageal surgery. In this issue, the use of SDD as an infection control measure is reported by Taylor & Oppenheim (p. 271). This is not a novel use of SDD as the authors recognize that SDD was used successfully to control an outbreak caused by a Klebsiella aerogenes producing a plasmid-mediated extended spectrum p-lactamase.3 By coincidence, the outbreak reported here was also caused by a multiply-resistant Klebsiella aerogenes. Traditional infection control measures had failed to eradicate the outbreak but the authors admit that to employ such measures requires the dedication of adequate numbers of trained staff. The authors conclude that ‘SDD appears to be a useful tool for eradicating outbreaks due to AGNB’. 241
242
Editorial
In a recent leading article, the author comments that SDD has opened new approaches for the investigation and the intervention of the intractable problem of colonization and infection of the digestive tract.4 Brun-Buisson et LzZ.~used SDD without systemic antibiotic and Taylor & Oppenheim have followed suit. The value of the systemic arm (cefotaxime) has yet to be evaluated but the use of such a valuable third generation cephalosporin gives cause for concern, given their capacity to stimulate inducible beta-lactamases in genera such as Pseudomonas, Enterobacter and Serratia.’ Before Taylor & Oppenheim embarked on the SDD phase of their study they had exhausted all reasonable efforts to control the outbreak, including antibiotic restriction, careful handwashing, environmental cleaning and finally closure of the ICU. Cohort isolation was practised and a modified form of SDD commenced. The PTA solution was administered via a nasogastric tube and a 2% PTA gel applied round the gum margins and the oropharynx; in addition, it was applied to the nose and the rectum. For one patient who had a vaginal reservoir of colonization and a colostomy, the gel was applied to these sites as well! Much of the additional cost of SDD is due to the use of systemic cefotaxime for the first few days which was not used in this study. However, the PTA regimen is costly, but in this study fewer specimens were sent to the laboratory for microbiological examination thus offsetting some cost. Sixteen reports assessing the development of antibiotic resistance during SDD have been published to date and whilst the emergence of Gram-negative bacilli resistant to the SDD regi’men has not been a major feature, most workers recognize the necessity of continued detailed surveillance. Such activity is expensive and perhaps now is the time for a detailed cost benefit analysis to be made by all would-be users of SDD. Meanwhile, the optimum regimen for both local and systemic antibiotics in the SDD regimen has to be decided and the optimal sub group of patients who may benefit without suffering from any sequelae needs to be identified. A. M. Emmerson
Department of Microbiology, University of Leicester, Leicester LEl 7RH References
1. Olson, B, Weistein RA, Nathan C, Chamberlin W, Kabins SA. Epidemiology of endemic Pseudomonas aeruginosa: why infection control efforts have failed. J Infect Dis 1984; 150: 808-816. 2. Stoutenbeek CP, van Saene HKF, Miranda DR, Zandstra DF. The effect of selective decontamination of the digestive tract on colonisation and infection rate in multiple trauma patients. Intens Care Med 1984; 10: 185-192. 3. Brun-Buisson C, Legrand P, Rauss A et al. Intestinal decontamination for control of nosocomial multi-resistant gram-negative bacilli: study of an outbreak in an intensive care unit. Ann Intern Med 1989; 110: 873-881. 4. Sanderson PJ. Selective decontamination of the digestive tract. Br Med J 1989; 299: 1413-1414. 5. Sanders CC. Novel resistance selected by the new expanded spectrum cephalosporins. J Infect Dis 1983; 147: 585-590.
of Hospital
Infection (1991) 17, 241-242
EDITORIAL
Selective
decontamination
as an infection
control
measure Colonization and infection with multiply-resistant aerobic Gram-negative bacilli (AGNB) are frequent problems in long-stay traumatized or immunosuppressed patients in intensive care units (ICUs). Conventional methods of infection control are time consuming, labour intensive and are often restricted to the control of exogenous sources of infection. It is tempting to support the gloomy conclusion that ‘traditional control measures aimed at the prevention of exogenous acquisition of Pseudomonas aeruginosa (and other AGNB) are unlikely to have an impact on the overall incidence of infection and that efforts to prevent infection in patients who are already colonized are necessary’.’ There have been a number of trials highlighting the success of selective decontamination of the digestive tract (SDD) in the prevention of unit-acquired ‘secondary’ endogenous infections following the introduction of the concept by the Groningen group.* Nevertheless, there are a number of controversial issues that remain before the regimen of selective, parenteral and enteral antisepsis (SPEAR) can be accepted. The basis of SDD is to employ non-absorbable agents, the PTA regimen, (polymyxin B, tobramycin and amphotericin B) to eliminate or greatly reduce the number of AGNB whilst retaining the normally predominant (? and protective) anaerobic flora, thus attempting to prevent colonization or overgrowth of drug-resistant strains. In addition, the third generation cephalosporin, cefotaxime was given intravenously for the first few days to treat or prevent infection occurring while the intestinal agents take effect. To date, published studies have identified three patient populations where the effective abolition of the abnormal carrier state by means of SDD has occurred. These include ICU patients with mid-grade (10-19) APACHE II scores, patients undergoing transplantation and patients undergoing oesophageal surgery. In this issue, the use of SDD as an infection control measure is reported by Taylor & Oppenheim (p. 271). This is not a novel use of SDD as the authors recognize that SDD was used successfully to control an outbreak caused by a Klebsiella aerogenes producing a plasmid-mediated extended spectrum p-lactamase.3 By coincidence, the outbreak reported here was also caused by a multiply-resistant Klebsiella aerogenes. Traditional infection control measures had failed to eradicate the outbreak but the authors admit that to employ such measures requires the dedication of adequate numbers of trained staff. The authors conclude that ‘SDD appears to be a useful tool for eradicating outbreaks due to AGNB’. 241
242
Editorial
In a recent leading article, the author comments that SDD has opened new approaches for the investigation and the intervention of the intractable problem of colonization and infection of the digestive tract.4 Brun-Buisson et LzZ.~used SDD without systemic antibiotic and Taylor & Oppenheim have followed suit. The value of the systemic arm (cefotaxime) has yet to be evaluated but the use of such a valuable third generation cephalosporin gives cause for concern, given their capacity to stimulate inducible beta-lactamases in genera such as Pseudomonas, Enterobacter and Serratia.’ Before Taylor & Oppenheim embarked on the SDD phase of their study they had exhausted all reasonable efforts to control the outbreak, including antibiotic restriction, careful handwashing, environmental cleaning and finally closure of the ICU. Cohort isolation was practised and a modified form of SDD commenced. The PTA solution was administered via a nasogastric tube and a 2% PTA gel applied round the gum margins and the oropharynx; in addition, it was applied to the nose and the rectum. For one patient who had a vaginal reservoir of colonization and a colostomy, the gel was applied to these sites as well! Much of the additional cost of SDD is due to the use of systemic cefotaxime for the first few days which was not used in this study. However, the PTA regimen is costly, but in this study fewer specimens were sent to the laboratory for microbiological examination thus offsetting some cost. Sixteen reports assessing the development of antibiotic resistance during SDD have been published to date and whilst the emergence of Gram-negative bacilli resistant to the SDD regi’men has not been a major feature, most workers recognize the necessity of continued detailed surveillance. Such activity is expensive and perhaps now is the time for a detailed cost benefit analysis to be made by all would-be users of SDD. Meanwhile, the optimum regimen for both local and systemic antibiotics in the SDD regimen has to be decided and the optimal sub group of patients who may benefit without suffering from any sequelae needs to be identified. A. M. Emmerson
Department of Microbiology, University of Leicester, Leicester LEl 7RH References
1. Olson, B, Weistein RA, Nathan C, Chamberlin W, Kabins SA. Epidemiology of endemic Pseudomonas aeruginosa: why infection control efforts have failed. J Infect Dis 1984; 150: 808-816. 2. Stoutenbeek CP, van Saene HKF, Miranda DR, Zandstra DF. The effect of selective decontamination of the digestive tract on colonisation and infection rate in multiple trauma patients. Intens Care Med 1984; 10: 185-192. 3. Brun-Buisson C, Legrand P, Rauss A et al. Intestinal decontamination for control of nosocomial multi-resistant gram-negative bacilli: study of an outbreak in an intensive care unit. Ann Intern Med 1989; 110: 873-881. 4. Sanderson PJ. Selective decontamination of the digestive tract. Br Med J 1989; 299: 1413-1414. 5. Sanders CC. Novel resistance selected by the new expanded spectrum cephalosporins. J Infect Dis 1983; 147: 585-590.