The faecal flora : a source of healthcare-associated infections and antibiotic resistance

• Healthcare-associated infections (HAI) are important causes of mortality and morbidity, and antibiotic treatment is often necessary. Development and availability of new antibiotics are closely followed by development of resistance among microorganisms. During antibiotic therapy, a fraction of the antibiotic given is found in the gut. The human gut is an important reservoir of bacteria. Microorganisms residing or passing the gut is referred to as the gut flora or microbiota. The results of this thesis showed spread of Enterococcus spp between patients on a general intensive care unit, causing septicaemia. After improved hygiene, reorganisation of rooms and thorough cleaning of the unit, together with revision of antibiotic strategy, the incidence of septicaemia with Enterococcus spp fell. Investigation of patients treated for acute intra-abdominal infections showed a shift in the aerobic faecal flora from antibiotic-susceptible Enterobacteriaceae spp towards Enterococcus faecium, yeasts and species of Enterobacteriaceae more resistant to antibiotics, after antibiotic treatment and hospital care. Investigation of recurrent outbreaks of Serratia marcescens sepsis in patients admitted to a neonatal intensive care unit showed different clones with each outbreak. Multiple hygiene interventions and revision of antibiotic strategy subsequently obviated recurrent outbreaks of sepsis, but spread of S. marcescens was not reduced until compliance with basic hygiene guidelines remained stable above 80%. We also found that low gestational age at birth, ventilator treatment and central venous or umbilical catheters are independent risk factors for late onset sepsis. Investigation of the faecal microbiota in patients with acute appendicitis or diverticulitis revealed that disturbance of the faecal microbiota already existed on admission, with higher numbers of Enterobacteriaceae and less Bacteroides, Faecalibacterium, Ruminococcus and Prevotella prior to antibiotic treatment and hospitalisation, than the control population. After treatment and hospitalisation diversity increased significantly in the diverticulitis group, approaching the healthy controls in composition.

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