Legionella and Legionnaires' disease: a review with emphasis on environmental studies and laboratory diagnosis

Comparative study of Legionella pneumophila and other nosocomial-acquired pneumonias

We studied, in a prospective way, the characteristics of definitively diagnosed nosocomially acquired pneumonias in our hospital over 36 months. Out of 55 cases, 27 were due to Legionella pneumophila and 28 to other, non-Legionella bacteria. The cases of legionellosis concentrated in July, August, and December. The only risk factors that showed significant differences (p less than 0.05) were general anesthesia and surgery and immunosuppressive disease, which were more frequent in the non-Legionella group, as were chronic liver disease and lowering of consciousness level. The absence of severe underlying disease, chronic or not, was uncommon in both groups, but more frequent in the Legionella group. We observed no differences in the clinical features of the two groups. Mean values of gamma-glutamyltranspeptidase and total bilirubin were higher (p less than 0.05) in the non-Legionella group. The only x-ray data that showed significant difference were pleural effusion, more frequent in the non-Legionella group (p less than 0.02). The mortality rate of legionellosis was 14.6 percent compared to 35.7 percent for the non-Legionella group (p less than 0.05). We conclude that a sure differential diagnosis based on clinical, roentgenographic and analytical features of both groups is not possible. The relatively low mortality rate of the Legionella group, when compared to other series of nosocomial legionellosis, could be due to the standard use of erythromycin in the therapeutic approach to nosocomial-acquired pneumonia in our hospital.

Air pollution: the pathobiologic issues

In defining the adverse effects of ambient levels of ozone on the human lung, research has tended to emphasize direct cause and effect responses. However, disease is generally multicausative and the lung has relatively few ways to respond to injury. Moreover, all adult lungs have some disease. Thus, pathogenesis is more appropriately addressed by asking "What role does the agent in question play in the causation, promotion, facilitation, and/or exacerbation of disease that is present?" Our recent studies of the lungs of 107 ostensibly healthy youths between 14 and 25 years of age (violent death cases in Los Angeles County) add suggestive evidence to epidemiologic and experimental data indicating that air pollution is adversely affecting the human lung. We found 80% of the youths with some degree of presumably subclinical Centriacinar Region disease and, in 27%, the Centriacinar Region disease was severe and extensive. Centriacinar Region disease has been linked to infectious organisms, cigarette smoke, ozone, mineral dusts, and other noxious agents. Recently, a mild form of Centriacinar Region disease has been produced in primates exposed to a level of ozone (0.15 ppm) that is frequently exceeded in Los Angeles. Since there is suggestive evidence that air pollution in Los Angeles increases the rate of decline of lung function, we suspect that there has also been an increase in the rate of structural decline, manifest in part by accentuated Centriacinar Region disease. The health significance of Centriacinar Region disease is just beginning to be appreciated. At the very least, reserve depletion reflected in the Centriacinar Region disease implies some reduction in lung performance and some increase in susceptibility to disease in general. At worst, the unexpected severity of the Centriacinar Region disease may be a bellwether for an impending rise in clinically manifested lung disease for the general population. An urgent research need is the monitoring of health through inventories of the functional and structural units of the human lung, with special emphasis on subpopulations of cell societies of the lung. The feasibility of applying image analysis for large volume objective quantitations has been demonstrated and should be implemented. Multicity studies, in cooperation with Offices of the Medical Examiner-Coroner and autopsy services in general, can help meet the critical need for increased sensitivity in the monitoring of the public health in a changing environment.

Prevalence of IgM antibodies to nine Legionella species in Icelandic children

In order to evaluate the prevalence of antibodies to Legionella species among children in Iceland, a prospective study was conducted in 424 children aged 1 month to 12 years, 28 of whom had an acute respiratory tract infection. Antibody titers to L. pneumophila serogroup 1-6, L. bozemanii, L. dumoffii, and L. micdadei were measured by microagglutination technique. Seroreactivity to Legionella spp. was found in 30% of the children greater than 3 years of age and in 22% of all children. The majority of the children with legionella antibodies had no history of previous or present respiratory tract infection. The children with previous pneumonia or bronchial asthma did not show a higher seroreactivity to legionella than children without such a history. Our observations suggests that Icelandic children are frequently exposed to Legionella species or closely related bacteria.

Atypical legionellosis: isolation of Legionella pneumophila serogroup 1 from a patient with aspiration pneumonia

It has been suspected that the number of Legionella pneumophila infections is substantially higher than commonly reported, due to subclinical infections. We report a patient where the diagnosis of a legionella infection was made only because of a large-scale surveillance programme for legionellosis. The case demonstrates the possibility of legionellas being involved in lung disease though not necessarily causing overt legionellosis.

Legionnaires' disease: an emerging surgical problem

Legionnaires' disease is an important, although often overlooked, complication in the patient postoperatively. Up to 50% of all nosocomial legionellosis in the hospitals reviewed was found in surgical patients. Patients undergoing a transplant procedure are at highest risk, but occurrence is common in the surgical patient undergoing general anesthesia, endotracheal intubation, or both. Aerosolization, aspiration, and direct instillation of contaminated water during manipulation of the respiratory tract are likely mechanisms of transmission. The usual clinical presentation is that of a nonspecific pneumonia. Specialized laboratory techniques including selective culture media, direct fluorescent antibody stains, and serological detection of antibodies are necessary for accurate diagnosis. If these tests are not routinely available, Legionnaires' disease may remain undiagnosed. Environmental surveillance of the hospital water distribution system is advisable for hospitals with a large surgical case load. If transplantation is performed, such surveillance is mandatory.