Opportunistic pneumonia: a clinicopathological study of five cases caused by an unidentified acid-fast bacterium

Legionella micdadei: A Forgotten Etiology of Growing Cavitary Nodules: A Case Report and Literature Review

Background. Legionella micdadei is a Gram negative bacterium that can stain weakly acid fast. It was first described in 1979 after immunosuppressed patients developed pneumonia at a Pittsburgh VA, initially given the name Pittsburgh Pneumonia Agent. It is the second most common Legionella species causing infection after pneumophila, and typically infects immunocompromised hosts. It is not easy to be cultured which makes diagnosing difficult. Case Presentation. A 31-year-old female with ulcerative colitis, primary sclerosing cholangitis, and cirrhosis presented with fever, chills, shortness of breath, dry cough, and chest pain for five days after being started on immunosuppression for autoimmune hepatitis two months earlier. The first chest CT showed small bilateral cavitary nodules. The nodules continued to grow on subsequent imaging despite what was thought to be appropriate therapy. A transthoracic biopsy was performed which grew Legionella micdadei and the patient improved after being treated with levofloxacin. Conclusion. Legionella micdadei is an atypical pathogen known to cause pneumonia in immunosuppressed patients. This case highlights a typical presentation of an atypical infection not commonly thought about and should be considered when nodules are growing despite being on broad antimicrobial therapy.

Mistaken identity: Legionella micdadei appearing as acid-fast bacilli on lung biopsy of a hematopoietic stem cell transplant patient

Legionella micdadei is a potential cause of invasive lung infections in immunocompromised hosts. On biopsy specimens, it can appear as an acid-fast bacillus (AFB) and can be mistaken for a member of genus Mycobacterium. As Legionella requires selective media to grow in culture, and the commonly used, commercially available urine antigen test for Legionella only detects Legionella pneumophila serogroup-1, but not L. micdadei, it is important to consider this organism in the differential diagnosis for AFB in immunocompromised hosts. We report a case of L. micdadei infection, which was initially treated empirically for non-tuberculous mycobacteria based on AFB staining of biopsy tissue before the final diagnosis was made.

Amoebal pathogens as emerging causal agents of pneumonia

Despite using modern microbiological diagnostic approaches, the aetiological agents of pneumonia remain unidentified in about 50% of cases. Some bacteria that grow poorly or not at all in axenic media used in routine clinical bacteriology laboratory but which can develop inside amoebae may be the agents of these lower respiratory tract infections (RTIs) of unexplained aetiology. Such amoebae-resisting bacteria, which coevolved with amoebae to resist their microbicidal machinery, may have developed virulence traits that help them survive within human macrophages, i.e. the first line of innate immune defence in the lung. We review here the current evidence for the emerging pathogenic role of various amoebae-resisting microorganisms as agents of RTIs in humans. Specifically, we discuss the emerging pathogenic roles of Legionella-like amoebal pathogens, novel Chlamydiae (Parachlamydia acanthamoebae, Simkania negevensis), waterborne mycobacteria and Bradyrhizobiaceae (Bosea and Afipia spp.).

The incidence and clinical implication of sputum with positive acid-fast bacilli smear but negative in mycobacterial culture in a tertiary referral hospital in South Korea

Although it is not rare to find sputum that is positive acid-fast bacilli (AFB) smear but subsequent culture fails to isolate mycobacteria in clinical practice, the incidence and clinical implication of those sputa from new patients has not been clearly elucidated. The aim of this study was to determine the incidence and clinical implication of sputum with positive AFB smear but negative in mycobacterial culture. All sputa that were positive AFB smear requested during diagnostic work up for new patients visiting Seoul National University Hospital from 1 January 2005 through 31 December 2006 were included. Sputa producing a positive AFB smear but negative mycobacterial culture were classified into one of four categories: laboratory failure to isolate mycobacteria, false positive AFB smear, pathogen may show a positive AFB smear other than mycobacteria, and indeterminate results. Out of 447 sputa with a positive AFB smear, 29 (6.5%) failed to culture any organism. Among these 29 sputa, 18 were caused by laboratory failure to isolate mycobacteria, six were false positive smears, and five indeterminate. Although most sputum with a positive AFB smear but negative culture could be classified as a laboratory failure, clinicians should consider the possibility of false positive AFB smear.

Bacterial Infections

In Osier’s time, bacterial pneumonia was a dreaded event, so important that he borrowed John Bunyan’s characterization of tuberculosis and anointed the pneumococcus, as the prime pathogen, “Captain of the men of death.”1 One hundred years later much has changed, but much remains the same. Pneumonia is now the sixth most common cause of death and the most common lethal infection in the United States. Hospital-acquired pneumonia is now the second most common nosocomial infection.2 It was documented as a complication in 0.6% of patients in a national surveillance study,3 and has been reported in as many as 20% of patients in critical care units.4 Furthermore, it is the leading cause of death among nosocomial infections.5 Leu and colleagues6 were able to associate one third of the mortality in patients with nosocomial pneumonia to the infection itself. The increase in hospital stay, which averaged 7 days, was statistically significant. It has been estimated that nosocomial pneumonia produces costs in excess of $500 million each year in the United States, largely related to the increased length of hospital stay.

Legionella micdadei infection presenting as severe secretory diarrhea and a solitary pulmonary mass

Sixty percent of infections with non-pneumophila species of Legionella are caused by Legionella micdadei. Although diarrhea is a common symptom of legionellosis, including that due to L. micdadei infection, severe, life-threatening diarrhea is rare. We describe a patient with profound secretory diarrhea (secretion rate, up to 8 L/day) that was secondary to culture-proven L. micdadei pneumonia. In addition, a 3-cm pulmonary nodule was detected, which completely resolved after proper treatment for Legionella infection. Resolving pulmonary nodules have been previously reported in association with treatment of L. micdadei infections.

Infection due to Legionella species other than L. pneumophila

In addition to Legionella pneumophila, 19 Legionella species have been documented as human pathogens on the basis of their isolation from clinical material. Like L. pneumophila, other Legionella species are inhabitants of natural and man-made aqueous environments. The major clinical manifestation of infection due to Legionella species is pneumonia, although nonpneumonic legionellosis (Pontiac fever) and extrapulmonary infection may occur. The majority of confirmed infections involving non-pneumophila Legionella species have occurred in immunosuppressed patients. Definitive diagnosis requires culture on selective media. Fluoroquinolones and newer macrolides are effective therapy. A number of nosocomial cases have occurred in association with colonization of hospital water systems; elimination of Legionella species from such systems prevents their transmission to susceptible patients. It is likely that many cases of both community-acquired and nosocomial Legionella infection remain undiagnosed. Application of appropriate culture methodology to the etiologic diagnosis of pneumonia is needed to further define the role of these organisms in disease in humans.

An outbreak of Legionella micdadei pneumonia in transplant patients: evaluation, molecular epidemiology, and control

PURPOSE

To describe a nosocomial outbreak of Legionella micdadei pneumonia in transplant patients and to characterize the source of the outbreak and the control measures utilized.

SUBJECTS AND METHODS

We performed retrospective Legionella micdadei serologic testing to enhance case finding in transplant patients with pneumonia that lacked a documented microbial etiology, as well as prospective environmental surveillance of water sites and testing for Legionella in clinical specimens.

RESULTS

During a 3-month period, 12 cases of Legionella micdadei pneumonia were identified either by culture or serologic testing among 38 renal and cardiac transplant patients. Legionella micdadei isolates from hot water sources were found by pulsed-field gel electrophoresis to have a DNA banding pattern that was identical to the isolates from the first 3 culture-positive cases and from 2 cases that occurred 16 months later.

CONCLUSIONS

Hospitals caring for organ transplant recipients and other immunosuppressed patients must be aware of the possibility of environmental sources of outbreaks of Legionella infection. A first-line screen with the Legionella urine antigen test will identify Legionella pneumophila serogroup 1. However, specific cultures in outbreak situations should be considered to identify other Legionella pneumophila serotypes and the nonpneumophila Legionella species.

Acid-fast-positive Legionella pneumophila: a possible pitfall in the cytologic diagnosis of mycobacterial infection in pulmonary specimens

The acid-fast stain is commonly used in the rapid cytologic assessment of bronchoalveolar lavage (BAL) fluid to detect pulmonary mycobacterial infections, particularly in immunocompromised patients. The identification of acid-fast, rod-shaped organisms may be taken as presumptive evidence of such an infection, in the appropriate clinical setting. However, this determination is made less specific by the occasional acid-fast positivity of microorganisms other than mycobacteria. We report on the occurrence of a fatal pneumonia caused by acid-fast positive Legionella pneumophila detected by BAL. This is a potential pitfall in the rapid diagnosis of pulmonary mycobacterial infections.

Comparative analysis of Legionella pneumophila and Legionella micdadei virulence traits

While the majority of Legionnaire's disease has been attributed to Legionella pneumophila, Legionella micdadei can cause a similar infection in immunocompromised people. Consistent with its epidemiological profile, the growth of L. micdadei in cultured macrophages is less robust than that of L. pneumophila. To identify those features of the Legionella spp. which are correlated to efficient growth in macrophages, two approaches were taken. First, a phenotypic analysis compared four clinical isolates of L. micdadei to one well-characterized strain of L. pneumophila. Seven traits previously correlated with the virulence of L. pneumophila were evaluated: infection and replication in cultured macrophages, evasion of phagosome-lysosome fusion, contact-dependent cytotoxicity, sodium sensitivity, osmotic resistance, and conjugal DNA transfer. By nearly every measure, L. micdadei appeared less virulent than L. pneumophila. The surprising exception was L. micdadei 31B, which evaded lysosomes and replicated in macrophages as efficiently as L. pneumophila, despite lacking both contact-dependent cytopathicity and regulated sodium sensitivity. Second, in an attempt to identify virulence factors genetically, an L. pneumophila genomic library was screened for clones which conferred robust intracellular growth on L. micdadei. No such loci were isolated, consistent with the multiple phenotypic differences observed for the two species. Apparently, L. pneumophila and L. micdadei use distinct strategies to colonize alveolar macrophages, causing Legionnaire's disease.

Lung abcess complicating Legionella micdadei pneumonia in an adult liver transplant recipient: case report and review

Legionella micdadei (Pittsburgh pneumonia agent) is the second most common cause of Legionella pneumonia, and occurs predominantly in immunocompromised hosts. L micdadei is the cause of nosocomial pneumonia in renal transplant recipients, but has not been described in other adult solid organ transplant recipients. This report describes the first case of L micdadei pneumonia in an adult liver transplant recipient on immunosuppressive therapy. Importantly, this case highlights the difficulties in establishing the diagnosis, as the Legionella urinary antigen is negative, and special culture conditions are required. Furthermore, this case illustrates several atypical clinical features of L micdadei pneumonia in a transplant recipient, including a community acquired mode of transmission, occurrence several years after organ transplantation, and lung abcess formation. The patient was successfully treated with limited surgical resection and quinolone antimicrobial monotherapy.

Lung abscess caused by Legionella micdadei

We describe a case of lung abscess caused by sporadic infection with Legionella micdadei in a patient with AIDS. L micdadei infection can be very difficult to diagnose because the organism stains only weakly Gram negative, requires special culture media, and is not detectable with some direct fluorescent antibody tests that are directed only at Legionella pneumophila. Since it can stain acid fast, it may be confused with mycobacteria. The abscess was successfully treated using antibiotics and percutaneous catheter drainage.

Detection of infection or infectious agents by use of cytologic and histologic stains

A wide variety of stains are useful for detection of different organisms or, for viruses, the cytopathologic changes they induce, in smears prepared directly from clinical specimens and in tissue sections. Other types of stains, such as hematoxylin and eosin, are used routinely to stain tissue sections and are most valuable for assessing the immunologic response of the host to the invading pathogen. In many cases, the pattern of inflammation provides important clues to diagnosis and helps to guide the selection of additional "special" stains used predominantly for diagnosis of infectious diseases. A stain may be nonspecific, allowing detection of a spectrum of organisms, as do the Papanicolaou stain and silver impregnation methods, or detection of only a limited group of organisms, as do the different acid-fast techniques. Some nonspecific stains, such as the Gram stain, are differential and provide valuable preliminary information concerning identification. Immunohistochemical stains, on the other hand, are specific for a particular organism, although in some cases cross-reactions with other organisms occur. Despite the wealth of information that can be gleaned from a stained smear or section of tissue, however, the specific etiology of an infection often cannot be determined on the basis of only the morphology of the organisms seen; culture data are essential and must be considered in the final diagnosis.

Azithromycin inhibition of intracellular Legionella micdadei

Legionella micdadei is an intracellular parasite that is ingested, but not killed, by leukocytes. Within monocytes, the organism has been shown to grow 1.0 to 2.0 log10 units over 48 h (D. L. Weinbaum, R. R. Benner, J. N. Dowling, A. Alpern, A. W. Pasculle, and G. R. Donowitz, Infect. Immun. 46:68-73, 1984). Intracellular L. micdadei would appear to be a useful model in which to study the effect of antibiotics which accumulate intracellularly. Azithromycin, a newly introduced azalide, is highly concentrated within leukocytes and was therefore studied to determine its effect on a single strain of L. micdadei that had been ingested by human monocytes. Peripheral blood monocytes were allowed to ingest L. micdadei and extracellular, nonadherent organisms were subsequently removed by washing. Cells and cell-associated bacteria were then incubated at 0, 24, and 48 h in media with serial concentrations of azithromycin at sub-MIC levels (less than 1.0 microgram/ml). L. micdadei in cells not exposed to azithromycin grew 0.8 +/- 0.1 log10 units (mean +/- standard deviation) at 24 h and 1.7 +/- 0.4 log10 units at 48 h. At both 24 and 48 h, the lowest concentrations of azithromycin tested (0.02 microgram/ml) significantly inhibited bacterial growth in monocytes (P = 0.02). A stepwise inhibition of L. micdadei CFUs was noted with increasing azithromycin concentrations. In contrast, when cells were exposed to antibiotic before ingesting L. micdadei, a less effective antibacterial effect was noted. Under certain in vitro conditions, azithromycin is a potent agent against intracellular L. micdadei.

Virulence factors of the family Legionellaceae

Whereas bacteria in the genus Legionella have emerged as relatively frequent causes of pneumonia, the mechanisms underlying their pathogenicity are obscure. The legionellae are facultative intracellular pathogens which multiply within the phagosome of mononuclear phagocytes and are not killed efficiently by polymorphonuclear leukocytes. The functional defects that might permit the intracellular survival of the legionellae have remained an enigma until recently. Phagosome-lysosome fusion is inhibited by a single strain (Philadelphia 1) of Legionella pneumophila serogroup 1, but not by other strains of L. pneumophila or other species. It has been found that following the ingestion of Legionella organisms, the subsequent activation of neutrophils and monocytes in response to both soluble and particulate stimuli is profoundly impaired and the bactericidal activity of these cells is attenuated, suggesting that Legionella bacterial cell-associated factors have an inhibitory effect on phagocyte activation. Two factors elaborated by the legionellae which inhibit phagocyte activation have been described. First, the Legionella (cyto)toxin blocks neutrophil oxidative metabolism in response to various agonists by an unknown mechanism. Second, L. micdadei bacterial cells contain a phosphatase which blocks superoxide anion production by stimulated neutrophils. The Legionella phosphatase disrupts the formation of critical intracellular second messengers in neutrophils. In addition to the toxin and phosphatase, several other moieties that may serve as virulence factors by promoting cell invasion or intracellular survival and multiplication are elaborated by the legionellae. Molecular biological studies show that a cell surface protein named Mip is necessary for the efficient invasion of monocytes. A possible role for a Legionella phospholipase C as a virulence factor is still largely theoretical. L. micdadei contains an unusual protein kinase which catalyzes the phosphorylation of eukaryotic substrates, including phosphatidylinositol and tubulin. Since the phosphorylation of either phosphatidylinositol or tubulin might compromise phagocyte activation and bactericidal functions, this enzyme may well be a virulence factor. Administration of the L. pneumophila exoprotease induces lesions resembling those of Legionella pneumonia and kills guinea pigs, suggesting that this protein plays a role in the pathogenesis of legionellosis. However, recent work with a genetically engineered strain has convincingly shown that the protease is not necessary for intracellular survival or virulence. As might be expected with a complex process like intracellular parasitism, it appears that the capability of Legionella strains to invade and multiply in host phagocytes is multifactorial and that no single moiety which is responsible for the virulence phenotype will be found.

Ingestion of Legionella micdadei inhibits human neutrophil function

Legionella micdadei is a human pathogen which survives within leukocytes. To determine how this organism escapes intracellular destruction, we examined its effect on human neutrophil activity. Neutrophils were allowed to ingest L. micdadei prior to evaluation of functional activity. Compared with control cells which did not ingest organisms, cells ingesting L. micdadei showed significantly depressed production of superoxide anion (24.5 +/- 9.0 nmol/10(6) cells per 15 min versus 6.9 +/- 3.2 nmol/10(6) cells per 15 min, respectively; P = 0.002), chemotaxis (43.9 +/- 0.8 mm versus 0.9 +/- 1.3 mm of directed migration, respectively; P = 0.001) and bactericidal activity against Staphylococcus aureus (97.9% versus 37.6% of ingested organisms killed, respectively; P = 0.001). Similar degrees of inhibition could not be demonstrated when either Staphylococcus aureus or Escherichia coli was ingested by cells prior to evaluation. Inhibition of neutrophil function did not occur when phagocytosis of L. micdadei was prevented. However, inhibition occurred with heat-killed as well as with viable organisms. The inhibition of neutrophil function by ingested L. micdadei may help explain the bacterium's ability to survive intracellularly and may begin to explain the pathogenesis of this disease.

Evaluation of ultraviolet light for disinfection of hospital water contaminated with Legionella

An epidemic of nosocomial Legionella micdadei pneumonia occurred among renal transplant patients in the University of Virginia hospital between 1978 and 1982. Although no further cases were diagnosed after 1982, filters and ultraviolet light (UVL) fittings were installed in 1985 as an attempt to disinfect water piped to rooms of transplant patients, because of concern about persistence of L micdadei in hospital water. Water samples were obtained from eight UVL-treated rooms and eight control rooms. 26 of 95 control samples were culture positive for L micdadei compared with 0 of 71 samples of filtered, UVL-treated water (p less than 0.0001, Fisher's exact test). After the UVL fitting and filter had been bypassed because of a leak, 9 of 33 samples from the UVL rooms were positive (p less than 0.0001). These data suggest that UVL treatment may be useful in continuous disinfection of water in the hospital rooms of high-risk patients.

Legionnaires disease: historical perspective

In the summer of 1976, a mysterious epidemic of fatal respiratory disease in Philadelphia launched an intensive investigation that resulted in the definition of a new family of pathogenic bacteria, the Legionellaceae. In retrospect, members of the family had been isolated from clinical specimens as early as 1943. Unsolved epidemics of acute respiratory disease dating to the 1950s were subsequently attributed to the newly described pathogens. In the intervening years, the Legionellaceae have been firmly established as important causes of sporadic and epidemic respiratory disease. The sources of the infecting bacteria are environmental, and geographic variation in the frequency of infection has been documented. Airborne dissemination of bacteria from cooling towers and evaporative condensers has been responsible for some epidemics, but potable water systems are perhaps more important sources. The mode of transmission from drinking water is unclear. The Legionellaceae are gram-negative, facultative, intracellular pathogens. The resident alveolar macrophage, usually an effective antibacterial defense, is the primary site of growth. Cell-mediated immunity appears to be the most important immunological defense; the role of humoral immunity is less clear. Erythromycin remains the antibiotic of choice for therapy of infected patients, but identification and eradication of environmental sources are also essential for the control of infection.

Acid-fast bacilli in sputum: a case of Legionella micdadei pneumonia

Legionella micdadei has been implicated as a cause of nosocomial pneumonia. There are no reports of L. micdadei pneumonia diagnosed by acid-fast stain of expectorated sputum. We report a case of L. micdadei pneumonia in which expectorated sputum harbored acid-fast bacteria that reacted specifically with fluorescent antiserum to L. micdadei, confirmed by culture. In a patient at risk for nosocomial infection, the differential diagnosis of a positive sputum stain for acid-fast bacilli should include L. micdadei in addition to mycobacteria. Therapy for L. micdadei infection should be considered pending confirmation of the diagnosis.

Interferon inhibits the growth of Legionella micdadei in mouse L cells

The intracellular growth of Legionella micdadei was inhibited in mouse L cells treated with interferon (IFN). This IFN-mediated restriction was dose-dependent and required preincubation of the L cells with high doses of IFN (1,000 U/ml) for maximal inhibition. Incubation of L. micdadei with IFN alone had no detectable effect on growth of the bacteria. The IFN-mediated growth restriction was not dependent upon tryptophan concentration in the culture medium.

Antimicrobial therapy of experimental Legionella micdadei pneumonia in guinea pigs

Several antimicrobial agents were evaluated for activity against experimental Legionella micdadei pneumonia in guinea pigs. Erythromycin, rifampin, doxycycline, and sulfamethoxazole-trimethoprim produced significant reductions in mortality. Penicillin, cefazolin, cefoxitin, chloramphenicol, and gentamicin were not efficacious even though, at the doses administered, the peak concentrations of these agents in serum substantially exceeded their MICs for the test strain. It is suggested that the poor performance of the latter group of agents resulted from poor penetration into cells in which L. micdadei was multiplying.

Properties of an acid phosphatase from Legionella micdadei which blocks superoxide anion production by human neutrophils

The high-speed supernatant (100,000 g, 1 h) obtained after centrifuging a suspension of Legionella micdadei that had been freeze-thawed and sonicated contained (i) considerable acid phosphatase activity when assayed using 4-methylumbelliferyl phosphate (MUP) as the substrate, and a factor that blocked superoxide anion production by human neutrophils stimulated with f-Met-Leu-Phe. Chromatography of the extract on a hydroxylapatite column resolved two acids phosphatases (designated ACP1 and ACP2). Subsequent chromatography of ACP2 on a Sephadex G-150 column revealed coincident elution of phosphatase activity and neutrophil blocking activity. When heated at 45 degrees C for various periods of time, the phosphatase activity of the acid phosphatase preparation was lost at the same rate as the ability of the preparation to block superoxide anion production by neutrophils. Furthermore, preincubation of neutrophils and acid phosphatase together in the presence of a heteropolymolybdate complex that inhibits the phosphatase eliminated the effect of the L. micdadei phosphatase on neutrophil superoxide anion production. ACP2 had the following properties: pH optimum, 6.0; Km for MUP, 3.8 mM; isoelectric point, 4.5; substrate specificity, MUP greater than ADP greater than phosphoenolpyruvate greater than phosphothreonine greater than phosphoserine greater than phosphotyrosine; molecular weight (estimated by sucrose density gradient centrifugation and gel filtration chromatography), 71,000-86,000. These results indicate that a cell-associated phosphatase may play a role in the virulence of L. micdadei.

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.

Failure of erythromycin in treatment of Legionella micdadei pneumonia

A 59-year-old immunocompromised woman had nosocomial Legionella micdadei infection that failed to respond to two weeks of erythromycin in high intravenous doses and oral rifampin. Treatment with intravenous trimethoprim-sulfamethoxazole and oral rifampin, which previously has not been used in this infection, resulted in cure.

Applications of electron microscopy to diagnostic pulmonary pathology

Viruses and other possible causative agents should be sought light and electron microscopically in all cases of ill-defined diseases including "sarcoid." Ideally, tissue should be prepared for electron microscopic examination as soon as a specimen is obtained; however, when this has not been done, tissue preserved in formalin solution can be used. Viruses, some bacteria, and other agents suspected on the basis of light microscopic findings can be verified electron microscopically by reprocessing paraffin-embedded tissue from areas that show smudge cells, focal necrosis with atypical cellular proliferation, and nuclear inclusions. Electron microscopically, all dying cells show swelling and rupture of cellular organelles and membranes; reactive changes include proliferation of branching tubules and paracrystalline and other types of proteinaceous precipitates (inclusions) in both the nucleus and cytoplasm. Qualitative and quantitative changes of cellular organelles, fibrils, microvilli, and intercellular junctions reflect hyperplasia, metaplasia, or dysplasia of the cell and may enable identification of the diseases, e.g., desquamative interstitial pneumonia. In various conditions, basal laminae become irregular, disruptive, or reduplicated following epithelial necrosis and regeneration. Electron microscopic evidence of immunologic damage to basal lamina and cells and immuno-electron-microscopic features of the lung in general require further studies. Electron microscopic features of transbronchial biopsy specimens may be diagnostic in cases of alveolar proteinosis, histiocytosis X, and amyloidosis. Ultrastructural abnormalities of cilia are common; primary ciliary defects are rare. Finally, light microscopic, scanning electron microscopic, and x-ray energy-dispersive spectrometric examinations of paraffin-embedded sections appear most practical for the pathologic evaluation of cases of pneumoconiosis.

Community-acquired Legionella micdadei (Pittsburgh pneumonia agent) infection in Sweden

The first case of Legionella micdadei (Pittsburgh Pneumonia Agent) infection in Sweden is presented. A previously healthy 68-yr-old man fell ill with diarrhoea, fever, and mental confusion. Subsequently chest roentgenography revealed pneumonic infiltrates and a seroconversion to L. micdadei was shown. No source or transmission of infection was established. The only notable event was that the patient had been drinking rain-water from a barrel 1 day prior to his illness. An alimentary route of infection was considered.

New beta-lactamase-resistant cephem treatment of guinea pigs infected with Legionella pneumophila

The in vivo antimicrobial effect of seven new beta-lactamase-resistant cephems (cefotaxime, latamoxef, ceftazidime, ceftriaxone, cefotiam, cefbuperazone, and MT-141) on Legionella pneumophila (strain 81-066, serogroup IV) in guinea pigs was compared with that of erythromycin. As the minimal LD100 within one week was about 4.0 X 10(9) CFU/ml by intraperitoneal injection of the strain, the animals were inoculated with 2.0 ml of twofold dilutions of a suspension of this bacterium. The animals developed purulent peritonitis and systemic involvement demonstrated by the development of periangitis, pneumonia and pleuritis in the lungs. Three different doses of antibiotics were administered intraperitoneally immediately after the rectal temperature reached more than 40 C. Erythromycin had a significant therapeutic effect but none of the new cephems tested death of the infected guinea pigs.

Simultaneous infection with Legionella pneumophila and Pittsburgh pneumonia agent. Clinical features and epidemiologic implications

Nosocomial pneumonia caused simultaneously by two organisms, Legionella pneumophila and the Pittsburgh pneumonia agent, was documented in seven patients in one institution. In all seven cases, both organisms were demonstrated by isolation from culture or visualization by direct immunofluorescence. Four patients died as a result of pneumonia, including two who received erythromycin therapy. The hospital water distribution system appeared to be the reservoir for both L. pneumophila and Pittsburgh pneumonia agent. These seven cases constituted 26.9 percent and 17.9 percent of the cases of Pittsburgh pneumonia agent and Legionnaires' disease, respectively, at one institution. Given this relatively high incidence of dual infection, it is likely that the mode of transmission for both organisms is identical. Dual infection may account for some cases of antibody response to more than one Legionella species. Historical parallels of the discovery of L. pneumophila and Pittsburgh pneumonia agent are reviewed.

The use of tracheal and pulmonary aspiration to diagnose Legionella micdadei pneumonia

Legionella micdadei (Pittsburgh pneumonia agent) pneumonia was diagnosed in three patients by transtracheal aspiration and in a fourth patient by percutaneous lung aspiration on two occasions. The organism was identified by direct fluorescent antibody staining and by culture in each case. Diagnosis by aspiration of the respiratory tract was rapid, specific, and safe. This allowed early institution of specific antimicrobial therapy in a group of severely ill, immunocompromised patients. These techniques should be considered whenever the diagnosis of L micdadei pneumonia is likely.

Bactericidal activity of antibiotics against Legionella micdadei (Pittsburgh pneumonia agent)

The bactericidal activity of five antibiotics for Legionella micdadei was determined by the construction of time-kill curves. Erythromycin, rifampin, penicillin G, cephalothin, and gentamicin were bactericidal for L. micdadei at readily achievable concentrations. The minimal bactericidal concentrations, defined as those producing 99.9% killing within 24 h, were: erythromycin, 4.6; rifampin, 0.13; penicillin G, 0.25; cephalothin, 2.5; and gentamicin, 0.25 micrograms/ml. The ratios of the minimal bactericidal to minimal inhibitory concentrations for these antibiotics ranged from 1 to 8. Thus, the poor in vivo activity of beta-lactam and aminoglycoside antibiotics against L. micdadei cannot be ascribed to a lack of killing by these agents.

Isolation of Pittsburgh pneumonia agent from a hospital shower

Tatlockia (Legionella) micdadei, the Pittsburgh pneumonia agent, was isolated from a hospital shower. Although it was not possible, at the current time, to establish an epidemiological link to disease acquisition, this information may be significant because it provides further evidence that a water-associated reservoir of this organism exists within the hospital.

Susceptibility of Pittsburgh pneumonia agent (Legionella micdadei) and other newly recognized members of the genus Legionella to nineteen antimicrobial agents

The susceptibilities of 11 strains representing the five recognized species of Legionella were determined by agar dilution testing on buffered charcoal-yeast extract agar. All of the legionellae tested were susceptible to rifampin, erythromycin, rosaramycin, chloramphenicol, and the aminoglycosides and were resistant to clindamycin and vancomycin. Susceptibilities to penicillins and cephalosporins were variable. Legionella micdadei, Legionella bozemanii, and Legionella gormanii were susceptible to these agents, but minimal inhibitory concentrations for each species were different. Legionella dumoffii resembled Legionella pneumophila in being resistant to penicillin, cephalothin, and cephamandole and susceptible to moxalactam and cefoxitin. All species except L. micdadei produced beta-lactamase.

Successful treatment of Legionella micdadei (Pittsburgh pneumonia agent) pneumonia with erythromycin

Optimal treatment of Legionella micdadei pneumonia has not been established, although in vitro studies have shown the pathogen to be sensitive to erythromycin. At our institution, L. micdadei pneumonia was diagnosed in six patients over a one and one-half year period. All patients were immunocompromised and had a typical clinical syndrome; in four of six, diagnosis was made by isolation of the pathogen. All patients received erythromycin (2 to 4 g daily) for 12 to 27 days, and five of six recovered completely. One patient improved initially but died four weeks later from Serratia marcescens pneumonia and septicemia. Although L. micdadei may cause life-threatening pneumonia in immunocompromised hosts, prompt diagnosis and institution of erythromycin therapy can result in a favorable outcome.

Lung biopsy in immunocompromised patients: one institution's experience and an approach to management of pulmonary disease in the compromised host

The authors report on their institution's experience with 53 lung biopsies, including 26 open, 22 transbronchial, and five trephine air drill biopsies, performed in immunocompromised patients with roentgenographic pulmonary infiltrates. Open biopsy was far more likely to provide a specific etiologic diagnosis (81%, P less than 0.001) than transbronchial biopsy (32%), or trephine biopsy (20%). Infection (17 biopsies), neoplastic disease, (7) or drug-related pneumonitis (2) were identified most frequently. Patients with myeloproliferative disease, granulocytopenia, or those who had not received prior immunosuppressive therapy were most likely to have a nondiagnostic biopsy (P less than 0.05 for each factor). The overall complication rate of biopsy procedures was 15% and was comparable with all three methods. Survival in this series was not significantly lower if a specific etiologic diagnosis could not be established, but correlated with the respiratory rate (less than 20 per minute), pO2 (greater than 60 torr), and the roentgenographic pattern (other than bilateral diffuse disease) at the time of biopsy (P less than 0.05 for each factor). There were 18 cases (34%) in which a clearcut etiologic diagnosis would not be established at the time of biopsy; based on serologic tests performed ex post facto, 2 of 12 of these cases (17%) were Legionnaire's disease. Lung biopsies were helpful in the management of the majority of the cases, although nondiagnostic biopsies continue to be a problem. The authors propose an approach to the management of compromised patients with pulmonary infiltrates.

The pathology of the Legionella pneumonias. A review of 74 cases and the literature

Following the discovery of Legionella pneumophila as the cause of an epidemic of pneumonia at an American Legion convention in Philadelphia, a group of related bacteria were recognized as additional human pathogens. This newly established bacterial genus, Legionella, includes the agents of Legionnaires' disease, Pittsburgh pneumonia, and several related infections. There are many similarities in the pathology of human infection caused by all the Legionella species. All produce a severe confluent lobular or lobar pneumonia, and abscess formation is not uncommon. A leukocytoclastic inflammatory infiltrate of neutrophils and macrophages, "septic" vasculitis of small blood vessels, coagulation necrosis, and focal septal disruption are characteristic but not diagnostic features. The inflammatory response is clearly that of a bacterial pneumonia with a necrotizing component, and does not resemble most mycoplasmal, chlamydial, or viral pneumonias. The bacteria can be demonstrated well by special stains. Acid fastness of Legionella micdadei, the cause of Pittsburgh pneumonia, is a helpful presumptive clue to diagnosis. The bacteria can be presumptively speciated in tissue by direct immunofluorescence. In addition, reliable recovery of the organisms on agar media now allows a specific diagnosis to be made. As a group, these infections are properly referred to as the Legionella pneumonias.

Etiologic diagnosis of acute pneumonia in adults: a growing challenge

For most pneumonia patients, an etiologic diagnosis can be established by proper use of noninvasive methods. Cultures of blood and pleural fluid and serologic titers are the most specific. The clinical history is helpful in distinguishing community- from hospital-acquired pneumonia and in identifying patients who are immunosuppressed or aspiration prone. When noninvasive diagnostic means and initial antibiotic therapy fail, the physician must choose between further empiric treatment and an invasive procedure with its attendant risks. For seriously ill and immunosuppressed patients, the need for an etiologic diagnosis is usually sufficient to justify these risks. The need for invasive diagnostic procedures is likely to increase in the future, necessitating greater knowledge of the relative risks and merits of each procedure on the part of all physicians who treat patients with pneumonia.

Legionella micdadei (Pittsburgh pneumonia agent): direct fluoresent-antibody examination of infected human lung tissue and characterization of clinical isolates

Legionella micdadei (Pittsburgh pneumonia agent) was identified by direct fluorescent-antibody (DFA) examination of lung tissue in six of seven persons diagnosed previously as having L. micdadei pneumonia only by histopathology and in four persons who also had positive cultures of the organism. No cross-reactions occurred with monospecific DFA conjugates prepared against Legionella pneumophila serogroups 1 to 6, Legionella bozemanii, Legionella dumoffii, and Legionella gormanii. One person had L. pneumophila serogroup 6 identified by DFA examination of lung tissue and subsequent culture of stored pulmonary secretions. Characterization of the four strains of L. micdadei revealed specific DFA reactions, bacteriological behavior, and cellular fatty acid composition that allow identification of the organism. DFA testing appears to be a sensitive method for identifying L. micdadei prescent in human lung tissue or cultured on artificial media.

Opportunistic lung infections in renal transplant patients: a comparison of Pittsburgh pneumonia agent and legionnaires' disease

From July 1977 to January 1980, 5 cases of pneumonia owing to Pittsburgh pneumonia agent and 4 cases owing to Legionella pneumophila occurred in our renal transplant population. Comparison of the clinical manifestations, laboratory features an radiographic changes demonstrated no unique characteristics that allowed differentiation from other bacterial pneumonias. Diagnosis in all cases required histologic or serologic identification of the infecting organism. We herein present our protocol for establishing rapidly the diagnosis of pneumonia in renal transplant patients with emphasis on the use of open lung biopsy.

Bacteria newly recognized as nosocomial pathogens

Bacteria recently recognized as nosocomial pathogens generally fall into three categories: those that grow slowly, those that are fastidious in their nutritional or atmospheric requirements and those that resemble commensals. Each characteristic has contributed to the delay in perceiving their importance. Mycobacterium chelonei and Myco. fortuitum--which grow slowly, although characterized as "rapid-growing" mycobacteria--cause sternal osteomyelitis, pericarditis and endocarditis after cardiac surgery as well as other wound infections after many types of surgery. Myco. chelonei-like organisms have been found to cause "sterile" peritonitis in patients receiving long-term peritoneal dialysis. Legionella pneumophila and L. micdadei are fastidious bacteria that were more difficult to detect because they stain poorly with the Gram method. They cause pneumonia and lung abscess, especially in immunocompromised people. Clostridium difficile is an anaerobe that causes toxin-mediated pseudomembranous colitis in persons given antibiotics that inhibit competing gut bacteria. Chylamydia trachomatis, an intracellular organism that has not been grown in vitro, causes pneumonia and conjunctivitis in young infants who acquire the organism from their mothers at birth. Group JK bacteria cause septicemia in patients whose immune responses have been suppressed and must be distinguished from "diphtheroid" contaminants in blood cultures. Clinicians, microbiologists and epidemiologists must be alert to the characteristics of these organisms that make them easily overlooked and should also anticipate the existence of other bacteria not yet identified.

Infection in the renal transplant recipient

The incidence of infection in the renal transplant patient is directly related to the net immunosuppressive effect achieved and the duration of time over which this therapy is administered. A second major factor in the causation of infections in this population is the nosocomial hazards to which these patients are exposed, ranging from invasive instrumentation to environmental contamination with Aspergillus species, Legionella pneumophila, Pseudomonas aeruginosa and other microbial pathogens. Careful surveillance is necessary to identify and eliminate such nosocomial sources of infection. The major types of infection observed can be categorized according to the time period post-transplant in which they occur: postsurgical bacterial infection in the first month after transplantation; opportunistic infection, with cytomegalovirus playing a major role, and transplant pyelonephritis in the period one to four months post-transplant; and a mixture of conventional and opportunistic infections in the last post-transplant period. Conventional infection in this late period occurs primarily in patients with good renal function who are receiving minimal immunosuppressive therapy; opportunistic infection occurs primarily in patients with poor renal function who are receiving higher levels of immunosuppression.