Infections in patients requiring ventilation in intensive care: application of a new classification

Abstract

OBJECTIVE: To classify infections according to the carrier state determined by surveillance cultures of throat and rectum, rather than by the traditional criterion of the time of onset after admission. METHODS: An observational cohort study of 3 months' duration was performed in a mixed medical---surgical intensive care unit (ICU) in a district general hospital of a subset of patients requiring mechanical ventilation for 3 days. Surveillance cultures from throat and rectum were obtained on admission to the ICU and then twice weekly to distinguish carriage of potentially pathogenic microorganisms (PPM) brought in by the patient from microorganisms acquired during the ICU stay. RESULTS: Out of the total population of 104 patients, 21 patients were enrolled over 3 months. Eight patients (38%) developed 12 infections, half of which were of primary endogenous pathogenesis and caused by Haemophilus influenzae, Candida albicans and Pseudomonas aeruginosa carried by the patients on admission. The remaining six were of secondary endogenous pathogenesis and caused by Acinetobacter baumannii and Pseudomonas aeruginosa acquired in the unit. CONCLUSIONS: Traditional classifications of hospital infection are challenged. If the traditional 48-h cut-off point was used, then 9 of 12 cases (75%) of infection would have been classified as nosocomial, whereas using the method based on the carrier state, 50% of all infections were caused by microorganisms carried by the patient on admission to the ICU. Moreover, we believe that the distinction between primary endogenous, secondary endogenous and exogenous is valid because these three types of infection each require different control methods.

Initial Bacterial Colonization in Patients Admitted to a Respiratory Intensive Care Unit:Bacteriological Pattern and Risk Factors

“…Microorganisms recognized as causing respiratory infections were referred to as potentially pathogenic microorganisms (PPM). PPMs were further classified into predominantly community or hospital acquired (c-PPMs and h-PPMs) and non-PPMs [22, 23]. The following microorganisms were classified as c-PPMs: Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis, Escherichia coli, methicillin-sensitive Staphylococcus aureus, and Candida spp.…”

Epidemiological Study and Classification of ICU Infections, Using the Carrier State Criterion

“…Awareness of carriage in long stay patients can provide a more realistic insight into the epidemiology of infections occurring in the ICU (8,10,12). The above is achieved with the consequent sampling of throat and rectum from the admission of the patient and afterwards every 3 days (surveillance samples), and further evaluation from the Microbiologic laboratory.…”

“…The traditional time cut-off has been used in many studies from a practical point of view (4,15,19). The 48-h cut-offpoint was introduced following the common experience of specific incubation times associated with highly pathogenic microorganisms (8,10). Though it assists in treating infections, this classification raises some practical problems (8).…”

“…This classification does not depend on the time of onset of the infection, but on the carrier state of the patients and manifestation of infections in these patients (8,10,(12)(13).…”

“…The classification of infections which is applied nowadays and conforms with CDC (4,10), is based on the 48-h cut-off, starting from the admission of the patient to the hospital (II).…”