B. Misset et al., MECHANISMS OF FAILURE TO DECONTAMINATE THE GUT WITH POLYMIXIN-E, GENTAMICIN AND AMPHOTERICIN-B IN PATIENTS IN INTENSIVE-CARE, European journal of clinical microbiology & infectious diseases, 13(2), 1994, pp. 165-170
The objective of the present work was to assess the possible mechanism
s of the poor efficiency of selective decontamination of the digestive
tract (SDD) in medical and surgical intensive care unit (ICU) patient
s. Sixty-four consecutive mechanically ventilated patients received gu
t decontamination with polymixin E, gentamicin and amphotericin B via
a nasogastric tube and were assessed for oropharyngeal, gastric and fe
cal colonization and for the presence of each antibiotic in the stomac
h and feces. A decrease in fecal colonization with Escherichia coli wa
s observed over 20 days but not with other gram-negative bacteria or g
ram-positive cocci. Fifteen and 26 % of the fecal colonizing gram-nega
tive bacteria were resistant to polymixin E and gentamicin, respective
ly, at admission. These proportions increased to up to 50 % after 16 d
ays of treatment. Although 50 % of staphylococci were initially sensit
ive to gentamicin, all strains were resistant to this drug after four
days of SDD. Both antibiotics were found in concentrations of less tha
n 20 mug/g in 11 of 38 stools. Of these 38 stools, nine were not conta
minated, 20 were colonized with resistant bacteria and 16 with strains
sensitive to one antibiotic present in the stool. Therefore, the poor
efficiency of gut decontamination observed was probably due to the gr
eat proportion of resistant strains on admission of the patients, to t
he selection of such resistant strains with SDD, to poor intestinal tr
ansit of the antibiotics, and to inactivation of the drugs by the fece
s. These results support stringent monitoring of fecal colonization in
patients undergoing SDD in order to detect the fecal carriage of gram
-positive and multiresistant gram-negative bacteria.