Annals of Burns and Fire Disasters - vol. XIII - n° 1 - March 2000

SUMMARY. In order to explore changes in intestinal microflora and their significance in burn patients undergoing early escharectomy en masse (EEEM), six kinds of intestinal microflora bacteria in faeces were investigated in 29 EEEM patients by microbiological methods and compared with those observed in 20 healthy controls. The results showed that there was a clear decrease in the total number of intestinal bacterial. The number of aerobes such as E. coli and Candida in EEEM patients increased more markedly than that of the control. The number of anaerobes such as Bacteroides, Bifidobacteria, and Fusobacteria in EEEM patients decreased more markedly than that in nomial controls, indicating that the ecology of the intestinal microflora was disrupted. Out of 29 patients eight suffered diarrhoea due to intestinal infection. We therefore concluded that the disruption of the ecology of the intestinal microflc,ra existed in the early stage after EEEM. It is characterized by anaerobic bacteria disruption, which can be a major cause of intestinal infection.

Introduction

Thanks to developments in the knowledge of the pathophysiological changes occurring in severe bums and to the design of modern equipment for the monitoring of critical burn patients, we can now perform early escharectomy en masse (EEEM) as early as the burn shock period in major burn patients. This technique will be beneficial to patients and enable them to recover quickly, optimally, effectively, and economically.
However, the routine application of large dose of antibiotics to patients subjected to surgery patients has led to post-operative intestinal infection symptoms, e.g. diarrhoea, of varying degrees of gravity that may even be fatal in some patients.
We therefore compared the ecology of intestinal microtlora in 29 major burn patients who underwent EEEM with that of 20 healthy controls. The results were analysed in order to assess the changes in intestinal microflora ecology that may provide sound indications for the future effective management of post-burn intestinal microtlora disruption.

Subjects and methods

1. Operation group. Twenty-nine severely burned patients (24 male, 5 female) were enrolled in the study and admitted to our burn ward between November 1994 and March 1997 (average age, 31.6 ± 8.42 yr; range, 18-49 yr; average burned TBSA, 72.1 ± 11.9%; range, 55-97%). All the patients were treated with our routine institutional methods. All the patients underwent EEEM on post- operative days 4-6. The operation area covered more than 30%. The patients received routine post-operative application of powerful broad-spectrum antibiotics according to our institutional routine. Fresh stool specimens were randomly collected on post-operative days 1-5.

2. Control group. Twenty normal persons (17 male, 3 female) were taken as the control group (average age, 31.9 ± 8.5 yr; range 20-52 yr). None of the contrcls had recently been treated with antibiotics, hormones, or any other immunosuppressive, radiotherapeutic, or chemotherapeutic, agents. The sample taking procedure was the same as that followed with the patients.

Analysis of faecal microflora

All the specimens were taken immediately to the laboratory and processed within I h. Half a gram was placed in an anaerobic chamber, diluted tenfold in reduced 0.05% yeast extract solution, and emulsified in a vortex mixer. Serial tenfold dilutions were performed in reduced 0.05% yeast extract solution. Samples (0.1 ml) of selected dilution were plated on selective and non-selective aerobic, anaerobic, and Candida media for enumeration of the members of the intestinal microflora. The plates were incubated at 37 'C for 24 h for aerobic cultures or for 48 h in an anaerobic chamber for anaerobic cultures. Plates showing 30 to 300 colonies were used for bacterial counts. The incubated bacteria or Candida were then counted and identified.

Results

As illustrated in Table I, the faecal microflora was disrupted in the post-operative period. The population level of total aerobes, such as E. coli, and Candida increased twenty to fifty times, while levels of anaerobes, such as Bifidobacteria and Bacteroides, decreased more than a hundred times. The ratio of aerobes and anaerobe was disrupted, indicating alteration of the ecology of the intestinal microflora. Of the 29 patients eight (27.6%) suffered from intestinal infection (e.g. diarrhoea).

Discussion

The normal bacterial microflora in the human intestinal lumen is an important microbiological species. Intestinal lumen aerobes and anaerobes in normal humans maintain a relatively stable ratio, the micro-ecological balance being maintained by the interaction between the host and normal physiological bacterial species. 1,2 Disruption of the normal intestinal microtlora is caused by certain medical interventions, such as surgical operations and the administration of antibiotics, especially in patients undergoing major escharectomy.' These factors make the patients prone to intestinal microflora disruption, which is characterized by an alteration in the number and ratio of various bacteria. Clinical intestinal disruption exhibits a series of intestinal symptoms such as shapeless stools or diarrhoea. The principal causes of disturbances in the intestinal microflora are, first of all, pathophysiological intestinal changes that alter the biological and micro-ecological circumferences for the colonization of normal intestinal bacterial microflora, with the result that recessive microflora are dominated. Secondly, the administration of a large amount of broad-spectrum antibiotics may kill large quantities of normal intestinal microflora and decrease colonization resistance, which leads to intestinal bacterial disruption characterized by the overgrowth of some antibioticresistant bacteria and Candida. A number of studies have suggested that the anaerobic component of the intestinal microflora is essential for the maintenance of colonization resistance.` The physiological basis for colonization resistance has been attributed to competition for nutrients, competition for attachment sites, production of bacteriocins, and production of volatile fatty acids." The decrease in the number of anaerobes must lead to a decrease in host colonization resistance, which provokes an outbreak of diseases owing to colonization in the intestine of exogenous or potentially pathogenic microorganisms.
In our investigation we found that most patients who underwent EEEM exhibited obvious clinical symptoms in the post-operative period. Some patients even Fresented severe enteral infection, which was in some cases ultimately fatal. We therefore concluded that the ecological disruption of the intestinal microflora occurred during the early stage after EEEM, which may be the result of the comprehensive action of the burn and the application of broad- spectrum antibiotics. This was one of the direct causes of intestinal infection. The ecological disruption of intestinal microflora was characterized by the disruption of anaerobic microflora. However, we still need to study how to apply these discoveries in clinical practice with burn patients undergoing EEEM.

RESUME. Les Auteurs se sont proposés d'étudier les modifications de la microflore intestinale et leur importance pour les patients brûlés traités avec l'escarrectorme précoce en masse (sigle anglais EEEM). Ils ont étudié six types de bactérie de la microflore intestinale dans les feces de 29 patients qui suivaient le traitement avec l'escarrectomie précoce en masse, moyennant des méthodes microbiologiques, et ils ont comparé les résultats aux résultats obtenus dans 20 témoins sains. Ils ont trouvé que le numéro des aérobies comme E. Coli et Candida dans les patients EEEM augmentait en manière plus marquée que celui des témoins. L-c numéro des anaérobies comme les Bacteroides, les Bifidobacteria et les Fusobacteria dans les patients EEEM diminuait en manière plus évidente que celui des témoins. Ces résultats indiquaient que l'écologie de la microflore intestinale était dérangée. Sur les 29 patients huit ont souffert de diarrhée due à l'infection intestinale. Les Auteurs ont conclu que le dérangement de l'écologie de la microflore intestinale existait dans la phase précoce après FEEEM. Cette condition est caractérisée par un dérangement des bactéries anacrobiques qui peut constituer une cause importante de l'infection intestinale.