Legionellosis: Legionnaires' disease; Pontiac fever

Global atlas of predicted functional domains in Legionella pneumophila Dot/Icm translocated effectors

Legionella pneumophila utilizes the Dot/Icm type IVB secretion system to deliver hundreds of effector proteins inside eukaryotic cells to ensure intracellular replication. Our understanding of the molecular functions of the largest pathogenic arsenal known to the bacterial world remains incomplete. By leveraging advancements in 3D protein structure prediction, we provide a comprehensive structural analysis of 368 L. pneumophila effectors, representing a global atlas of predicted functional domains summarized in a database ( https://pathogens3d.org/legionella-pneumophila ). Our analysis identified 157 types of diverse functional domains in 287 effectors, including 159 effectors with no prior functional annotations. Furthermore, we identified 35 cryptic domains in 30 effector models that have no similarity with experimentally structurally characterized proteins, thus, hinting at novel functionalities. Using this analysis, we demonstrate the activity of thirteen functional domains, including three cryptic domains, predicted in L. pneumophila effectors to cause growth defects in the Saccharomyces cerevisiae model system. This illustrates an emerging strategy of exploring synergies between predictions and targeted experimental approaches in elucidating novel effector activities involved in infection.

Impact of Chlorine Dioxide on Pathogenic Waterborne Microorganisms Occurring in Dental Chair Units

Bacterial contamination is a problem in dental unit water lines with the consequence of implementing regular disinfection. In this study, the short-term impact of chlorine dioxide (ClO₂) treatment was investigated on the microorganisms Legionella pneumophila and L. anisa, Pseudomonas aeruginosa, Escherichia coli, and Staphylococcus aureus. The environmental background was proven as an important factor regarding the tolerance to 0.4 mg/L ClO₂ as saline and phosphate-buffered saline resulted in a higher bacterial reduction than tap water. Gram-positive microorganisms demonstrated higher robustness to ClO₂ than Gram-negative, and microorganisms adapted to tap water showed increased stability compared to cultured cells. At high densities, substantial numbers of bacteria were able to withstand disinfection, whereby the use of 4.6 mg/L ClO₂ increased the inactivation rate. A massive cell decrease occurred within the first 5 minutes with subsequent plateau formation or slowed cell reduction upon further exposure. This biphasic kinetics cannot be explained by a ClO₂ depletion effect alone, because the probability of bacterial subpopulations with increased tolerance should be taken into account, too. Our results prove high disinfection efficiency to microorganisms that were rather found in correlation to the level of bacterial contamination and background solutions than the chosen concentration for ClO₂ treatment itself.

Pathogenicity and Virulence of Legionella: Intracellular replication and host response

Bacteria of the genus Legionella are natural pathogens of amoebae that can cause a severe pneumonia in humans called Legionnaires’ Disease. Human disease results from inhalation of Legionella-contaminated aerosols and subsequent bacterial replication within alveolar macrophages. Legionella pathogenicity in humans has resulted from extensive co-evolution with diverse genera of amoebae. To replicate intracellularly, Legionella generates a replication-permissive compartment called the Legionella-containing vacuole (LCV) through the concerted action of hundreds of Dot/Icm-translocated effector proteins. In this review, we present a collective overview of Legionella pathogenicity including infection mechanisms, secretion systems, and translocated effector function. We also discuss innate and adaptive immune responses to L. pneumophila, the implications of Legionella genome diversity and future avenues for the field.

Legionella and Legionnaires' disease: Time to explore in India

Legionella pneumophila was first recognised as a fatal cause of pneumonia more than four decades ago, during the 1976-American Legion convention in Philadelphia, USA. Legionella spp. continue to cause disease outbreaks of public health significance, and at present, Legionnaires' disease (LD) has emerged as an important cause of community and hospital-acquired pneumonia. Parallel to this, the understanding of LD has also increased exponentially. However, the disease is likely to be underreported in many countries because of the dearth of common definitions, diagnostic tests and active surveillance systems. In this review, we outline the basic concepts of Legionella including clinical presentations, epidemiology, laboratory diagnosis and the status of LD in India. This article also summarises the progress of research related to Legionella in this country, identifying the research gaps and discussing priorities to explore this unexplored pathogen in India.

Legionella pneumophila Grows Adherent to Surfaces in vitro and in situ

Legionella pneumophila continues to play a role in both community- and nosocomially-acquired pneumonia. We investigated the ability of L pneumophila to adhere to various types of materials such as those found in the hospital air-cooling and potable water distribution systems. Through the use of a unique sampling apparatus, we were able to regularly acquire planktonic and sessile samples and determine the numbers of bacteria present in both populations, in vitro and in situ.

Portions of these apparatuses could be aseptically removed for examination by scanning electron microscopy, or for the determination of the number of viable adherent L pneumophila. The number of bacteria present in each sample was determined by direct plate count, with presumptive L pneumophila colonies being positively identified by direct fluorescent antibody staining techniques.

The results demonstrated that not only are legionellae capable of colonizing various metallic and nonmetallic surfaces but that they are preferentially found on surfaces. Surface-adherent bacteria may play a profound role as a reservoir of these potential pathogens in aquatic environments. Furthermore, these results suggest that any comprehensive legionella monitoring program must include not only water samples but also an examination of the adherent populations.

Legionnaires' disease

Since first identified in early 1977, bacteria of the genus Legionella are recognised as a common cause of community-acquired pneumonia and a rare cause of hospital-acquired pneumonia. Legionella bacteria multisystem manifestations mainly affect susceptible patients as a result of age, underlying debilitating conditions, or immunosuppression. Water is the major natural reservoir for Legionella, and the pathogen is found in many different natural and artificial aquatic environments such as cooling towers or water systems in buildings, including hospitals. The term given to the severe pneumonia and systemic infection caused by Legionella bacteria is Legionnaires' disease. Over time, the prevalence of legionellosis or Legionnaires' disease has risen, which might indicate a greater awareness and reporting of the disease. Advances in microbiology have led to a better understanding of the ecological niches and pathogenesis of the condition. Legionnaires' disease is not always suspected because of its non-specific symptoms, and the diagnostic tests routinely available do not offer the desired sensitivity. However, effective antibiotics are available. Disease notification systems provide the basis for initiating investigations and limiting the scale and recurrence of outbreaks. This report reviews our current understanding of this disease.

Automobile windshield washer fluid: A potential source of transmission for Legionella

Epidemiological evidence suggesting driving cars to be a risk factor for legionellosis has prompted public health studies to investigate vehicle windshield washer fluid as a novel transmission source of this disease. The goal of the current study was to investigate whether or not windshield washer fluid could serve as a potential source of transmission for Legionella. A wide variation in the survival of L. pneumophila was observed when incubated in different washer fluids at 25 and 37 °C, however, one brand tested supported Legionella survival similar to or greater than sterilized deionized water. In addition, 1 L of tap water contained in a washer fluid reservoir was able to support population growth and survival of Legionella for several months. In a field study examining the windshield washer fluid of 12 elementary school buses, Legionella were detected from 84% of samples at a high concentration of 8.1×10(4) CFU/mL. Culturable cells were also detected in aerosolized washer fluid during washer fluid spray. By demonstrating survival in certain windshield washer fluids, growth within washer fluid reservoirs, and the presence of viable cells in bus washer fluid spray, we have provided evidence suggesting the potential for a novel route of Legionella exposure.

Serological investigation of pneumonia as it presents to the physician's office

PURPOSE

To define the etiology of pneumonia, using a battery of serological tests, among patients presenting to physicians' offices in Cumberland County, Nova Scotia from July 2, 1989 to July 1, 1990.

METHODS

Patients presenting to their physician's office with symptoms suggestive of pneumonia were invited to participate in the study by completing a questionnaire, having a chest radiograph and providing acute and convalescent phase serum samples. These serum samples were tested for antibodies to Mycoplasma pneumoniae, Coxiella burnetii, Legionella pneumophila, adenovirus, and influenza viruses A and B. Some of the samples were tested for antibodies to Chlamydia pneumoniae.

RESULTS

Seventy-five of the inception cohort of 203 patients had a chest radiograph compatible with pneumonia, a completed questionnaire and acute and convalescent phase serum samples. There were 39 females and 36 males with a mean age of 41.7 years. Twenty-six (35%) were admitted to hospital. The mortality rate was 3%. Forty-five per cent had a diagnosis made by serology: M pneumoniae, 22 (29%); influenza A virus, five (7%); C burnetii, L pneumophila, adenovirus, two (3%) each.

CONCLUSIONS

While it is not possible to generalize about these findings because of ascertainment bias, the data suggest that M pneumoniae is a common cause of pneumonia presenting to a physician's office and that mortality is low in this group of patients.

Pontiac fever: an operational definition for epidemiological studies

BACKGROUND

Pontiac fever is usually described in epidemic settings. Detection of Pontiac fever is a marker of an environmental contamination by Legionella and should thereby call for prevention measures in order to prevent outbreak of Legionnaire's disease. The objective of this study is to propose an operational definition of Pontiac fever that is amenable to epidemiological surveillance and investigation in a non epidemic setting.

METHODS

A population of 560 elderly subjects residing in 25 nursing homes was followed during 4 months in order to assess the daily incidence of symptoms associated, in the literature, with Pontiac fever. The water and aerosol of one to 8 showers by nursing home were characterized combining conventional bacterial culture of Legionella and the Fluorescence In Situ Hybridization (FISH) technique that used oligonucleotides probes specific for Legionellaceae. A definition of Pontiac fever was devised based on clinical symptoms described in epidemic investigations and on their timing after the exposure event. The association between incidence of Pontiac fever and shower contamination levels was evaluated to test the relevance of this definition.

RESULTS

The proposed definition of Pontiac fever associated the following criteria: occurrence of at least one symptom among headache, myalgia, fever and shivers, possibly associated with other 'minor' symptoms, within three days after a shower contaminated by Legionella, during a maximum of 8 days (minimum 2 days). 23 such cases occurred during the study (incidence rate: 0.125 cases per person-year [95% CI: 0.122-0.127]). A concentration of Legionella in water equal to or greater than 10(4).L(-1) (FISH method) was associated with a significant increase of incidence of Pontiac fever (p = 0.04).

CONCLUSION

Once validated in other settings, the proposed definition of Pontiac fever might be used to develop epidemiological surveillance and help draw attention on sources of Legionella.

The incidence of Legionella pneumophila: a prospective study in a tertiary care hospital in India

The prevalence of Legionella pneumophila causing community-acquired pneumonia (CAP) in patients who were admitted to hospital was investigated. Between April 1997 and December 1998, 60 patients admitted to the All India Institute of Medical Sciences with CAP, were included in the study. Aetiological diagnosis was based on the results of routine microbiological blood culture for bacteria and serological test by enzyme linked immunosorbent assay (ELISA) for L. pneumophila serogroup 1-7. Eight (13%) patients had a conventional bacterial aetiology and nine (15%) had serological evidence of recent infection with L. pneumophila. Legionella pneumophila may be an important cause of CAP in adults in developing countries. Empiric antimicrobial treatment should include a combination of agents to cover both atypical agents and bacterial pathogens.

Ambulatory patients with community-acquired pneumonia: the frequency of atypical agents and clinical course

OBJECTIVES

To determine the etiology of community-acquired pneumonia in patients treated in an ambulatory setting, using serological methods, and to compare presenting symptoms, radiographic manifestations, and clinical outcomes of patients with pneumonia of "atypical" and undetermined etiology.

PATIENTS AND METHODS

This prospective cohort study was conducted in emergency room and outpatient facilities of Victoria General Hospital, Halifax, Nova Scotia, and in offices of participating family doctors based in Halifax. One hundred forty-nine adults with acute onset of one or more symptoms or signs suggestive of pneumonia and radiographic evidence of pneumonia who provided informed consent were enrolled. Patients known to be HIV positive or who had been discharged from a hospital within the previous 10 days were ineligible for enrollment. Demographic features and clinical data were collected by direct patient interview and chart review by trained research nurses. Outcome measures included quantitative evaluation of pneumonia-specific symptoms, and responses to the Short Form 36 Health Survey at presentation and at 30 days after presentation. Information was also collected on each patient's health prior to pneumonia, as well as the time until each patient's self-reported return to work and to usual activities. The etiology of pneumonia was determined by testing acute and convalescent serum samples for antibodies to Legionella pneumophila serogroup 1, Mycoplasma pneumoniae, Chlamydia pneumoniae, Chlamydia psittaci, Coxiella burnetii, adenovirus, respiratory syncytia virus, influenza viruses A and B, and parainfluenza viruses 1, 2, 3.

RESULTS

The study population consisted of 149 patients, 54 (36%) of whom were men, with a mean age (+/- SD) of 41 +/- 15 years. An etiological diagnosis was made in 74 (49.7%) patients using serological methods. Etiological agents included M pneumoniae 34 (22.8%); C pneumoniae 16 (10.7%); M pneumoniae and C pneumoniae 5 (3.4%); C burnetii 4 (2.7%); influenza A virus 4 (2.7%); and other agents 6% (7.4%). Three patients (2%) had a conventional bacterial etiology, and 72 patients (48.3%) had pneumonia of undetermined etiology. Patients with pneumonia of known (atypical) and undetermined etiology were similar in terms of age, gender, race, education, employment, and comorbidity. Despite a higher proportion of patients with pneumonia of known etiology reporting sweats, chills, and headache at presentation, the two groups were similar for symptom severity and bother. The patients with pneumonia of undetermined etiology were more likely to have multilobar pneumonia (P < 0.02). Both patients with atypical pneumonia and those with pneumonia of undetermined etiology suffered severe deterioration of physical functioning with a marked but incomplete recovery at 30 days. Those with atypical pneumonia had higher physical functioning and general mental health scores at 30 days.

CONCLUSIONS

Nearly half the cases of ambulatory community-acquired pneumonia are due to "atypical" agents. It is not possible to reliably distinguish patients with atypical pneumonia from those with pneumonia of undetermined etiology by clinical features at baseline. The outcomes in terms of resolution of symptoms, functional status, return to work, and return to usual activities are essentially similar in the two groups.

Overwhelming respiratory failure associated with Legionella pneumophila

Four patients were admitted to the medical intensive care unit at King Khalid University Hospital (KKUH) with overwhelming respiratory failure. Extensive investigations revealed serological evidence of Legionella infection. Three patients required intubation and mechanical ventilation. All patients received erythromycin; rifampin was added to two patients. Two patients survived and two patients died. We report, for the first time in Saudi Arabia, four cases of Legionella pneumophila with severe respiratory failure.

Legionella pneumophila grows adherent to surfaces in vitro and in situ

Legionella pneumophila continues to play a role in both community- and nosocomially-acquired pneumonia. We investigated the ability of L pneumophila to adhere to various types of materials such as those found in the hospital air-cooling and portable water distribution systems. Through the use of a unique sampling apparatus, we were able to regularly acquire planktonic and sessile samples and determine the numbers of bacteria present in both populations, in vitro and in situ. Portions of these apparatuses could be aseptically removed for examination by scanning electron microscopy, or for the determination of the number of viable adherent L pneumophila. The number of bacteria present in each sample was determined by direct plate count, with presumptive L pneumophila colonies being positively identified by direct fluorescent antibody staining techniques. The results demonstrated that not only are legionellae capable of colonizing various metallic and nonmetallic surfaces but that they are preferentially found on surfaces. Surface-adherent bacteria may play a profound role as a reservoir of these potential pathogens in aquatic environments. Furthermore, these results suggest that any comprehensive legionella monitoring program must include not only water samples but also an examination of the adherent populations.

Legionnaires' disease: the wollongong experience

Australia experienced its largest Legionnaires' disease epidemic in Wollongong, mid 1987. This paper presents an overview of Legionnaires' disease followed by details of the Wollongong epidemic including areas of particular interest to the physiotherapist, with comparisons of milder and severe cases. Unlike other epidemics, females outnumbered males. Predisposing factors of increasing age, cigarette smoking, respiratory and medical conditions were found. Except cigarette smoking, these factors and initial chest radiograph involving two or more zones, were significant features of the severe group. Patients in these categories require careful monitoring. Blood gases demonstrated consistent hypoxaemia and hypocapnoea. Seventy-eight per cent of cases recorded little or no sputum and implications for treatment are discussed. Impressions and fears of the epidemic are presented and recommendations made.

Pneumonias acquired from others. 2. Radiographic findings, treatment

Although patterns found on the chest film of a patient suspected to have pneumonia are usually nonspecific by themselves, they are useful in eliminating or narrowing diagnostic possibilities. For example, a miliary pattern suggests miliary tuberculosis, but it may also be caused by several noninfectious diseases (table 1). Other clues, such as the presence or absence of fever, must also be considered to arrive at a likely diagnosis. Cavitary lesions, bilateral hilar adenopathy, pleural effusions, and pulmonary nodules are other findings that are commonly seen on the chest film of these patients. Possible infectious and noninfectious causes are listed in tables 2 through 5. Antimicrobial therapy that is appropriate, free from side effects, and cost-effective must be chosen. The frequency of administration of a drug can make a great difference in the total cost of treatment, since hospitals charge for each intravenous dose. The clinician should consider which drug is effective against the infective organism and also the least expensive to administer (table 6).

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.

Nursing home-acquired pneumonia. A case-control study

To determine if there are any unique features of nursing home-acquired pneumonia we carried out a case-control study wherein each patient admitted with nursing home-acquired pneumonia was age- and sex-matched with a patient with community-acquired pneumonia. There were 36 men and 38 women in the nursing home group. The mean age of both groups was 74 years. The mortality rate for nursing home-acquired pneumonia it was 40.5%, whereas for community-acquired pneumonia it was 28% (P = NS). Patients with nursing home-acquired pneumonia had a significantly higher incidence of dementia and cerebrovascular accidents, and patients with community-acquired pneumonia were more likely to be smokers and to have chronic obstructive pulmonary disease. Aspiration pneumonia was more common among patients with nursing home-acquired pneumonia (P less than .001), and Hemophilus influenza pneumonia more common among the patients with community-acquired infection (P less than .01). Sputum for culture could be obtained in only 31 and 39% of the patients--contributory to the high rates of pneumonia of unknown etiology 63.5 and 56.1% for the nursing home group and the control subjects, respectively. Patients with nursing home-acquired pneumonia received cloxacillin and aminoglycosides more frequently than patients with community-acquired pneumonia (P less than .05), and patients with community-acquired pneumonia received erythromycin more frequently than patients with nursing home-acquired pneumonia (P less than .05). Complications were common during the hospital stay of these patients--the most frequent being congestive heart failure, urinary tract infection, renal failure, and respiratory failure.

[Pneumonia caused by Legionella pneumophila. Report of the 2d Brazilian case]

Os autores relatam um caso de pneumonia por Legionella pneumophila, diagnosticado pela primeira vez em Porto Alegre, Rio Grande do Sul. A hipótese diagnóstica foi confirmada por imunofluorescência indireta nas amostras de soro do paciente enviadas ao C.D.C. (Atlanta — E.U.A.), com títulos de 1:128 na amostra da fase aguda e 1:512 na amostra da fase de convalescença.

Legionella brain stem encephalopathy and peripheral neuropathy without preceding pneumonia

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Community-acquired pneumonia requiring hospitalization. Is it different in the elderly?

The authors studied 138 patients, 57 of whom were younger than 65 years of age and 81 who were 65 years of age and older, with community-acquired pneumonia to determine whether or not such pneumonia is different in the elderly and to define how such patients are investigated and treated. Pneumonia in the elderly was characterized by a higher mortality, 30 v 10%; more likely to be of unknown etiology, 54 v 30%; and more likely to show radiographic progression after the patient had been admitted to the hospital, 48 v 11%. In addition, elderly patients were more likely to be afebrile when admitted, 57 v 26%. Twenty-seven etiologic categories were present in 77 patients in whom a cause for the pneumonia was established. Streptococcus pneumoniae accounted for 9.4% of the pneumonia overall and for 27% of the pneumonia among patients who had sputum cultures performed before antibiotic therapy. The diagnostic yield was 11.6% for blood cultures, 38.2% for sputum cultures, 2.3% for throat washing, and 22.1% for serological studies. Twenty-seven percent of patients were receiving antibiotics of the time of admission to the hospital. Most (79%) received more than one antibiotic after admission. This study indicates that community-acquired pneumonia is a serious illness and that an algorithm approach to diagnosis and treatment of such pneumonia is necessary.

Effectiveness of 1-bromo-3-chloro-5,5-dimethylhydantoin against Legionella pneumophila in a cooling tower

Cooling towers are considered to be man-made amplifiers of Legionella spp. Thus, the proper maintenance and choice of biocides is important. The only biocidal measure that has thus far been shown to be effective in field tests is the judicious use of chlorination. Perturbation studies with 1-bromo-3-chloro-5, 5-dimethylhydantoin (Bromicide; Great Lakes Chemical Corp., West Lafayette, Ind.) (BCD) were conducted on an industrial cooling tower shown to contain Legionella pneumophila. At the concentrations recommended by the manufacturer, neither the density nor the activity of L. pneumophila was affected. At comcentrations greater than 2.0 ppm (2.0 micorgram/ml) free of residual, BCD was not effective in reducing L. pneumophila to source water concentrations, nor was it effective in reducing the 2-p-iodophenyl-3-p-nitrophenyl-5-phenyl tetrazolium chloride activity of the bacterium in situ. The data indicate that at concentrations up to 2.0 ppm, BCD is not effective in these tower studies.

Overwhelming pneumonia

A classification of normal-abnormal hosts and pathogens forms the basis for discussion of the diagnosis and management of pneumonia in the critical care setting. In order to arrive at the appropriate therapy for the unusual as well as the usual causative organisms of pneumonia, individual assessment of the need for invasive procedures must be made. The critical feature, however, is to consider the wide spectrum of possibilities for each individual patient.

Serological investigations of Legionella infections in Denmark

During the period 1 July 1978 to 1 January 1982, sera from 728 patients suspected of suffering from Legionella infection were tested for Legionella antibodies by an indirect fluorescent antibody test. The antigens used were prepared from heat-killed strains of L.pneumophila serogroups 1-4. In 1981 we further incorporated antigens from serogroups 5 and 6 of L.pneumophila together with L.micdadei, L.bozemanii, L.dumoffii and L.gormanii. According to the criteria put forward by CDC, Atlanta, USA Legionella infection was confirmed in 78 patients with pneumonia. Sera from 35 showed at least a four-fold rise in titre to greater than or equal to 128, while 43 had single or static titres of greater than or equal to 256. There were 59 men and 19 women (3.1:1) with a median age of 51 and 49, respectively. More than half the patients showed maximum titres of antibodies to L.pneumophila serogroup 1. In an additional patient, who was not tested serologically, the diagnosis was made post mortem at CDC by demonstration of Legionella in lung tissue. There were 11 fatal cases among the 79 patients (13.9%). Thirty-two had contracted the disease on a journey abroad. All cases except the seven first cases among tourists from Garda, Italy, were sporadic. The number of cases diagnosed has increased heavily while the proportion of imported cases has decreased.

Survival of virulent Legionella pneumophila in aerosols

Aqueous suspensions of virulent Legionella pneumophila grown on solid medium retained virulence and aerosol survival characteristics for several months. Significant numbers of viable organisms were recovered from aerosols held at various relative humidities (r.h.) for up to 2 h. The organisms survived best at 65% r.h. and were least stable at 55% r.h. Exponential phase broth-grown organisms survived poorly in aerosols in comparison with stationary phase broth cultures or organisms grown on solid medium, suggesting that the metabolic status of Legionella pneumophila organisms may be an important factor affecting their ability to survive in aerosols and cause respiratory disease.

Histopathology of experimental Legionnaires' disease in guinea pigs, rhesus monkeys and marmosets

Guinea pigs, rhesus monkeys and marmosets were infected with L. pneumophila in small particle aerosols. Fever and acute fibrinopurulent pneumonia resulted. The lesions involved distal lung tissue only, spreading from terminal and respiratory bronchioles and producing heavy infiltration of alveoli by polymorphs and macrophages and widespread exudation of oedema fluid and fibrin. Lesions were not found in extra-pulmonary sites.

An outbreak of Legionnaires' disease in Sweden: report of sixty-eight cases

From August 27 to September 21, 1979, 58 patients fell ill with Legionnaires' disease (LD) in the town Västerås, Sweden. All patients had been staying in the town some time during 2 weeks preceding their illness, as had 10 LD patients who fell ill from mid-June to mid-August the same year. Clinically, high fever, headache, dizziness and gastrointestinal symptoms were dominating. Respiratory symptoms were moderate, radiologically verified pneumonia was seen in 59 of 64 patients examined. One patient died. The diagnosis was verified by serology, using the IFL method, in all cases. Legionella pneumophila serogroup 1 was isolated from a closed lung biopsy from 3 patients. Isolates of identical strains were made from the cooling tower on the roof of an indoor shopping centre in Västerås, visited by 57 of the patients during the incubation period.

Legionella pneumophila seen in Gram stains of respiratory secretions and recovered from conventional blood cultures

We report a fatal case of Legionnaires' disease in which Legionella pneumophila was easily visible in large numbers in Gram stains of clinical material and was recovered from conventional blood cultures after seven days incubation. The presence of many readily seen Gram-negative, pleomorphic bacilli in direct Gram stains of respiratory secretions should support a possible diagnosis of Legionnaires' disease.

[Diseases of the lungs caused by legionella species (author's transl)]

Ever since the 1976 Philadelphia epidemic and the isolation of the causative organism by MacDade in 1977, numerous clinical, epidemiological and bacteriological papers have stressed the significance of the "new" causative organisms responsible for serious cases of pneumonia. On the basis of knowledge available at present, the Legionellaceae family accounts for these bacteria. There are five different species in the genus Legionella: L. pneumophila, L. micdadei, L. bozemannii, L. dumoffii and L. gormanii. L. pneumophila occurs most frequently and has six serogroups (Serogroups 1-6), the first of which is the most important. Legionelloses, the diseases caused by these organisms, occur epidemically, endemically or sporadically. In clinical terms, these are acute cases of pneumonia which occur especially frequently in older persons and immunocompromised hosts. The course is severe in such patients. There is increased lethality. Erythromycin, rifampicin and cefoxitin are the most effective antibiotics. After the culture has been made in the suitable milieu and the material obtained by pulmonary aspiration has been inoculated into guinea pigs, the bacteriological diagnosis is made by direct immunofluorescence. The serological diagnosis is based on evidence of serological changes demonstrated by the indirect immunofluorescence test.

Prevalence of antibodies to Legionella pneumophila in animal populations

We examined more than 2,800 human and animal sera for antibodies to four serogroups of Legionella pneumophila by using the microagglutination test. Antibody titers of greater than or equal to 1:64 were considered positive. The occurrence of positive equine sera (31.4%) was significantly higher than the occurrence of positive sera in cattle (5.1%), swine (2.9%), sheep (1.9%), dogs (1.9%), goats (0.5%), wildlife (0%), and humans (0.4%). The highest titer measured in horses was 1:512. The occurrence of positive sera in horses was related directly to age. In horses less than or equal to 1, 2 to 3, 4 to 7, 8 to 12, and greater than or equal to 13 years old, the percentages of positive sera were 0, 10.1, 30.3, 44.9 and 58.1%, respectively. When we compared age-specific serogroup-specific rates in horses from Colorado and Pennsylvania, we found differences. With horses 8 to 12 and greater than or equal to 13 years old, there was a significantly higher (P less than 0.05) occurrence of sera that reacted to serogroups II and III in horses from Pennsylvania. Of 242 positive sera, 43.8% reacted to a single serogroup (serogroup III or I most commonly), and 56.2% reacted to multiple serogroups (serogroups II and III or serogroups I, II, and III most commonly). A high percentage of seropositive horses suggested that horses are commonly infected with L. pneumophila or related organisms, and the age-specific rates of occurrence indicated that infection was related directly to duration of exposure. A definitive demonstration of equine infection will depend on isolation of the agent and repetition of this serological study with antigens obtained from organisms isolated from horses.