Essentials in clinical microbiology

Acute purulent exacerbation of chronic obstructive pulmonary disease and Chlamydia pneumoniae infection

In order to investigate the role of bacteria, including Mycoplasma pneumoniae and especially Chlamydia pneumoniae in acute purulent exacerbations of chronic obstructive pulmonary disease (COPD), we examined sputum specimens and acute and convalescent sera taken 26 d apart from 49 outpatients experiencing an acute purulent exacerbation of COPD. The sera were tested for antibodies to C. pneumoniae with the microimmunofluorescence test, and for antibodies to M. pneumoniae with the indirect fluorescence antibody test. Routine microbiologic culture of sputum yielded potentially pathogenic microorganisms in 12 of the 49 patients (24%). Three patients (6%) showed serologic evidence of recent M. pneumoniae infection. Seven patients showed high IgG titers of >/= 1:1,024 to C. pneumoniae, and an additional four had a fourfold increase in IgG titer, suggesting reinfection with C. pneumoniae. Sputum from two of these 11 patients also grew Streptococcus pneumoniae, and one grew Moraxella catarrhalis. Patients with and without serologic evidence of current C. pneumoniae infection showed no significant differences in clinical features or pulmonary function. The high incidence of infection with C. pneumoniae (the sole causal agent in 16% of cases, and the causal agent with other agents in 6%) provides insight into the importance of this organism among agents leading to exacerbations of COPD in Turkey.

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

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.