Extrahospital and intrahospital factors predisposing to the spread and colonization in patients of Pseudomonas aeruginosa, Proteus and Klebsiella in an infectious hospital.

The number of patients admitted to hospital who harbour Pseudomonas aeruginosa, Proteus and Klebsiella, keeps rising. Of the factors predisposing to colonization, only diabetes and antibiotic therapy exert their effect equally in extrahospital and intrahospital environment. Malignant diseases, immune suppressive therapy and instrumental interventions play a predominant role in the hospital. In extrahospital environment, infancy and old age, poor general condition as well as in almost half of the cases, an inflammatory process caused by viruses or bacteria was found to create favourable conditions for the colonization of facultative pathogens. One of the main sources of the Gram-negative facultative pathogens studied was the faeces of enteric patients in the hospital. The frequency of P. aeruginosa, Klebsiella and Proteus positive cultures rose parallel in the faecal and non-faecal bacteriological samples in the period 1958 to 1977. The seasonal changes observed in the frequency of positive cultures revealed that the Gram-negative facultative pathogens had increased in number first in the enteral wards, spreading subsequently to the medical and paediatric wards, and finally they appeared in a high number in the surgical wards, originating from patients transferred there from the medical or paediatric wards.