172

Letters

to the Editor

personnel. In this instance the person concerned MRSA but whether it has been truly eradicated

now appears to be clear of is, as yet, unknown.

We would like to thank Dr R. Marples of the Central Public Health Laboratory, Dr P. Jumaa from Whipps Cross Hospital, Dr R. M. Perinpanayagam from Queen Mary’s University Hospital, MS R. Biddle from the Gold Coast Hospital, Queensland, Australia, Mr Ian McCabe and the laboratory staff at the Whittington Hospital for their help in investigating this outbreak, and the doctor involved for his co-operation.

Department of Microbiology, Whittington Hospital, Highgate Hill, London N19 5NF, UK

R. Hancox A. Cummins M. C. Kelsey

References JF, Marples RR. Another strain of methicillin-resistant Staphylococcus aureus London. Lancet 1988; 2: 748-749. working party of the Hospital Infection Society and British Society for Chemotherapy. J Hosp Infect 1990; 16: 351-377. Recurrent staphylococcal infections and the duration of the carrier state. J Hyg Camb 1960; 58: 11-19. 4. Rosdahl VT, Laursen H, Benzon MW, Kjaeldgaard P, Thomsen M. Colonization priority among Staphylococcus aureus strains-correlation with phage type. J Hosp Infect 1988; 12: 151-162. 5. Cookson B, Peters B, Webster M, Phillips I, Rahman M, Noble W. Staff carriage of methicillin-resistant Staphylococcus aureus. J Clin Microbial 1989; 27: 1471-1476. 6. Hicks NR, Moore EP, Williams EW. Carriage and community treatment of methicillin resistant Staphylococcus aureus: what happens to colonized patients after discharge? J Hosp Infect 1991; 19: 17-24. 1. Richardson epidemic in 2. Combined Antimicrobial 3. Roodyn L.

Sir, Emergence

of resistance

during

selective

digestive

decontamination?

I have read with interest the article by van Saene, Stoutenbeek and Hart in the Journal of Hospital Infection (1991) 18, 261-277, entitled ‘Selective decontamination of the digestive tract (SDD) in intensive care patients: a critical evaluation of the clinical, bacteriological and epidemiological benefits’. The authors conclude that superinfection as a consequence of resistant bacteria has not as yet been reported. Their point, that copy strains have not been excluded in the resistance studies is well taken but, to the best of my knowledge neither have copy strains been excluded in most SDD studies.

Letters

to the Editor

173

Some additional comments seem to be necessary. For obvious reasons the authors were not able to cite the most recent studies, presented at the 17th International Congress of Chemotherapy (ICC) in Berlinlm8 and the 31st Interscience Conference on Antimicrobial Agents and Chemotherapy two previous publications, (ICAAC) in Chicago 9,10. They also omitted which clearly demonstrated emergence of antibiotic-resistant bacteria during SDD. Nau et al.” noted a rise of cefuroximeand gentamicin-resistant staphylococci shortly after the introduction of SDD in a neurological intensive care unit. The percentage of gentamicin-sensitive Pseudomonas spp. declined. The parallel increase of staphylococci insensitive to cefazolin, cefotaxime and oxacillin reflected the selection or induction of methicillin-resistant strains by SDD. Unertel et aZ.‘* described the expected risk of tracheal colonization (Kaplan-Meier estimate) during SDD with Gram-negative bacteria resistant to gentamicin as 4% at 1 month; for Gram-negative bacteria resistant to polymyxin as 8% at 1 month; and for resistant Staphylococcus aureus as 6% at 1 month. Pneumonia caused by resistant organisms and mortality both increased during SDD.” Three out of the eight SDD studies presented at the ICC in Berlin (1991) did not find a reduction in the incidence of pneumonia and a decrease in mortality was not found in six of the seven studies which measured this. In four of the eight studies oxacillin-resistant S. aureus, coagulase-negative staphylococci or cefotaxime-resistant Gram-negative organisms were described.“2p5 Two double-blind randomized studies were presented at the 31st ICAAC; in one, ventilator-associated pneumonia (VAP) due to Gram-negative bacilli was significantly less frequent in patients receiving SDD. However, a trend towards an increase in the rate of VAP caused by staphylococci was observed in the SDD group. The authors concluded that the absence of a beneficial effect on the overall incidence of VAP may be related to an increased frequency of Gram-positive pathogens.” In the other study there was no emergence of resistant strains in SDD patients, but most of the bronchopneumonias were caused by S. auwus. Decontamination of the stomach was achieved in 70% of the SDD patients, but in the trachea of only 50% of the patients, and S. aureus was more often isolated than in placebo patients (PK, Graf B, Deller A, kilian J, Ahnefelh FW. Pneimonieprophylaxe langzeitbeatmeter Patienten: Selektive Darmdekontamination nach Stoutenbeek oder Kilonisationsprophylaxe nach Unertl? Ein prospektiver randomisierter Vergleich beider Regime. Anaesthesiologische Intensivmedizin Notfallmedizin Schmerztherapie 1991; 26: 270-275. 14. Prod’hom P, Leuenberger P, Koerfer J et al. Effect of stress ulcer prophylaxis on nosocomial pneumonia in ventilated patients: a randomized comparative study. 31. ICAAC 1991; Abstr. No. 999.

Sir,

Dr Van Saene and colleagues

reply

We have read Prof. Daschner’s letter with great interest.’ His letter is the seventh in a serieslm7 in which he questions the purpose and the data available. We wish to clarify our position and to provide some counterarguments to Prof. Daschner’s views. Professor Daschner’s conclusion that ‘there is absolutely no doubt that SDD leads to emergence of resistance’ is based on 12 abstracts, one letter and one German publication. The discrepancy between the results of the review of 20 SDD publications’ in peer reviewed journals showing no increase in superinfections and Professor Daschner’s message is surprising. SDD is a method to control infections caused by potentially pathogenic microorganisms (PPM) including Staphylococcus aureus and aerobic Gramnegative bacilli (AGNB). Indigenous flora such as viridans streptococci, enterococci and coagulase negative staphylococci (CNS) are by dejinition resistant to the SDD antimicrobials.8 The SDD regimen, including the nonabsorbable mixture of tobramycin, polymyxin E, amphotericin B and the parenteral cephalorin cefotaxime, is not active against methicillinresistant S. aureus (MRSA).9 Intensivists using SDD should know that the SDD regimen needs to be adjusted in patients who are admitted with MRSA” e.g., by adding oral vancomycin to paste (2%) and suspension (4 X 250 mg). Dr Nau’s letter has already been discussed.” Apparently Dr Nau’s analysis was suboptimal due to the inclusion of both Gram-negative and Gram-positive copy strains, a failure acknowledged in his reply.12 His correspondence is not mentioned by Professor Daschner. Professor Daschner references our work13 and concludes that SDD leads to increased resistance amongst both Gram-positive and Gram-negative microorganisms, to an increase in pneumonias due to resistant bacteria and to increased mortality. This work was presented at the 3rd International Conference on Nosocomial Infections, Atlanta, 1990 and published as an

Emergence of resistance during selective digestive decontamination?

172 Letters to the Editor personnel. In this instance the person concerned MRSA but whether it has been truly eradicated now appears to be clear o...
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