How common is Legionnaires' disease?

Aetiology of community acquired pneumonia in Valencia, Spain: a multicentre prospective study

A year long multicentre prospective study was carried out in the Valencia region of Spain, to determine the cause of community acquired pneumonia. The study was based on 510 of 833 patients with pneumonia. Of these, 462 were admitted to hospital, where 31 patients died. A cause was established in only 281 cases--208 of bacterial, 60 of viral, and 13 of mixed infection. The most common microorganisms were Streptococcus pneumoniae (14.5%), Legionella sp (14%), Influenza virus (8%), and Mycoplasma pneumoniae (4%). There was a higher incidence of Legionella sp than in other studies.

Legionella: an infrequent cause of adult community acquired pneumonia in Dublin

The commonest infectious agents identified in community acquired pneumonia (CAP) amongst 50 patients admitted to a Dublin hospital were Streptococcus pneumoniae and Haemophilis influenzae. Legionella pneumophila pneumonia occurred in only one patient who acquired infection abroad. A serological screen of blood bank donors and renal transplant recipients failed to detect antibody to Legionella pneumophila supporting the clinical findings of a low prevalence of infection in this community. It is concluded that initial antibiotic therapy for patients with CAP need not routinely include cover for Legionella.

Significance of non-pneumophila Legionella species in adult community-acquired and nosocomial pneumonias

The number of different Legionella species is increasing at an impressive rate. In two prospective studies, one involving 110 intensive-care unit (ICU) patients with mainly nosocomial pneumonias and the other 105 patients with community-acquired pneumonias, we investigated the incidence and significance of Legionella pneumophila and non-pneumophila pneumonias on the basis of 17 different main serogroups. In the first study, 14 ICU patients had 15 (13.6%) Legionella pneumonias, which, in 5 cases (33%), were of non-pneumophila etiology. In the second study, 9 patients with community-acquired pneumonias had 10 (9.5%) Legionella pneumonias. Leading this study were 6 L. gormanii infections, followed by 2 L. dumoffii and only 1 L. pneumophila and 1 L. longbeachae pneumonia. Of the total, 22 of 23 patients with Legionnaires' disease suffered from severe basic diseases and complications (acute renal failure, respiratory insufficiency, etc.) predominant among the nosocomial pneumonias. The mortality rate was significant in these patients at 33% (5 patients) in the ICU group and 10% (1 patient) in the group with community-acquired pneumonias. We conclude that non-pneumophila Legionella species should receive more diagnostic and therapeutic consideration in patients with nosocomial or community-acquired pneumonias.

Comparative clinical and laboratory features of legionella with pneumococcal and mycoplasma pneumonias

The clinical and laboratory features of 83 cases of community-acquired pneumococcal pneumonia (PP), 79 cases of legionella pneumonia (LP) and 62 cases of mycoplasma pneumonia (MP) have been compared. No unique features have been found in any group. Patients with MP were younger, were more likely to have had prior antibiotics before hospital referral, had a predominance of upper respiratory tract symptoms, low total white cell counts and lacked features of multisystem involvement. Multisystem features were common in both PP and LP with confusion, high fever, hyponatraemia, hypoalbuminaemia and abnormalities of liver function occurring more often in LP. A high leucocyte count was especially common in PP. Antibiotic therapy in community-acquired pneumonia must remain empirical until a definite microbiological diagnosis is made.

Legionnaires' disease: a review of 79 community acquired cases in Nottingham

Seventy nine cases of sporadic, community acquired legionnaires' disease have been reviewed. Annual and seasonal variation in incidence was noted. The mean age of the patients was 53 years and 50 (63%) were male. Pre-existing chronic diseases were present in only 23 (29%), including two patients receiving immunosuppressive treatment. Common symptoms included unproductive cough, dyspnoea, chest pain, headache, confusion, nausea, vomiting, and diarrhoea. Respiratory symptoms were absent, however, in 17 (22%). Localising chest signs were present in 74 (95%) cases. Frequent laboratory findings included lymphopenia, high erythrocyte sedimentation rate, hyponatraemia, raised urea and creatinine concentrations, abnormal liver function, hypophosphataemia, hypoalbuminaemia, proteinuria, and haematuria. Thirteen patients died (16%), including nine of 20 who received assisted ventilation. The mortality rate in patients treated with erythromycin (11%) was lower than in those who received other antibiotics (23%), but this difference was not statistically significant. Of the features noted on admission, only a high plasma urea concentration was significantly associated with death. Sporadic community acquired legionnaires' disease is a not uncommon disorder, which with appropriate treatment has a prognosis similar to that of other forms of community acquired pneumonia.

Aetiology and outcome of severe community-acquired pneumonia

Between January 1972 and December 1981, 50 patients with severe community-acquired pneumonia were admitted to the intensive care unit of a district general hospital. A causal pathogen was identified in 41 cases (82%). Streptococcus pneumoniae (16 cases), Legionella pneumophila (15 cases) and Staphylococcus aureus (5 cases) were the commonest. Assisted ventilation was required in 44 patients, of whom 25 died (57%). All 5 patients with staphylococcal pneumonia and 12(75%) with pneumococcal pneumonia died. Only 5 (33%) with Legionnaires' disease died. Mortality was significantly associated with age. Recommendations for the management of severe pneumonia are made.

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

Legionella pneumophila and related species are important causes of epidemic bacterial pneumonia and nosocomial infection. This review will discuss this new family of bacteria and the diseases they produce. The classification, general microbiologic characteristics, and ecology of the bacteria will be reviewed and the epidemiology and clinical aspects of the infection will be discussed. More emphasis will be given to issues that are more directly related to laboratory workers and with which the author has had more direct experience: pathology, laboratory diagnosis of human infection, pathogenesis of the infection, and virulence mechanisms of the bacterium. Therapy and prevention of the infection will be discussed more briefly.

Adult community-acquired pneumonia in central London

Strep. pneumoniae was diagnosed as the cause of pneumonia in 40 (50%) of 80 consecutive adults admitted to St Stephen's Hospital with community-acquired pneumonia. None of the patients had evidence of Mycoplasma pneumoniae infection, and Legionella pneumophila serology was positive on only one occasion. In 29 patients (36%) no causative organism was demonstrated. The diagnosis of pneumococcal infection was obtained in 15 cases by isolating Strep. pneumoniae from the sputum, in 13 further cases by demonstrating pneumococcal capsular antigen in sputum, and in 12 other cases by detecting pneumococcal antigen in serum only. Only 2 cases with pneumococcal pneumonia were bacteraemic and 3 patients (7%), all aged more than 75 years, died. The relatively low bacteraemic and mortality rates suggest that community-acquired pneumococcal pneumonia currently seen in patients admitted to hospital in central London may not be so severe as in some other areas.

Legionella pneumonia--a neglected diagnosis?

A brief survey of the epidemiology, clinical manifestations, differential diagnosis and treatment of infections with Legionella species is given, with particular emphasis on Legionella pneumophila. Because of recent epidemiological evidence that this species may be an important cause of both community-acquired and hospital-acquired pneumonia, particularly in the immunosuppressed patient, it is suggested that this microbial agent should be considered more often in the differential diagnosis of pneumonia. This has practical implications for therapy, since the drug of choice in Legionella infections is erythromycin, with doxycycline as an alternative. Rifampicin may be added to one of the drugs mentioned, in serious infection.

Comparative radiographic features of community acquired Legionnaires' disease, pneumococcal pneumonia, mycoplasma pneumonia, and psittacosis

The features of the chest radiographs of 49 adults with legionnaires' disease were compared with those of 91 adults with pneumococcal pneumonia (31 of whom had bacteraemia or antigenaemia), 46 with mycoplasma pneumonia, and 10 with psittacosis pneumonia. No distinctive pattern was seen for any group. Homogeneous shadowing was more frequent in legionnaires' disease (40/49 cases) (p less than 0.005), bacteraemic pneumococcal pneumonia (25/31) (p less than 0.01) and non-bacteraemic pneumococcal pneumonia (42/60) (p less than 0.05) than in mycoplasma pneumonia (23/46). Multilobe disease at presentation was commoner in bacteraemic pneumococcal pneumonia (20/31) than in non-bacteraemic pneumococcal pneumonia (15/60) (p less than 0.001) or legionnaires' disease (19/49) (p less than 0.025). In bacteraemic pneumococcal pneumonia multilobe disease at presentation was associated with increased mortality. Pleural effusions and some degree of lung collapse were seen in all groups, although effusions were commoner in bacteraemic pneumococcal pneumonia. Cavitation was unusual. Lymphadenopathy occurred only in mycoplasma pneumonia (10/46). Radiographic deterioration was particularly a feature of legionnaires' disease (30/46) and bacteraemic pneumococcal pneumonia (14/27), and these groups also showed slow radiographic resolution in survivors. Radiographic resolution was fastest with mycoplasma pneumonia; psittacosis and non-bacteraemic pneumococcal pneumonia cleared at an intermediate rate. Residual intrapulmonary streaky opacities remained in over a quarter of survivors from legionnaires' disease (12/42) and bacteraemic pneumococcal pneumonia (5/19).