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Bacteria
Published in Julius P. Kreier, Infection, Resistance, and Immunity, 2022
Legionnaires′ disease was first described in 1976 and eventually the etiologic agent was identified as Legionella pneumophila, an inhabitant of contaminated water that may become airborne in aerosols from cooling towers, air conditioners, and plumbing systems where water has previously been heated followed by a prolonged period of stagnation. Apparently sufficient nutrients accumulate in water lines from valve gaskets, etc. to support growth of the organisms. When contaminated aerosols are inhaled, infection may result. The bacteria are probably not free-living in the water, but infect free-living amoebae and ciliated protozoa; where, if they infect amoebae cysts, can survive environmental extremes such as insufficient chlorination, desiccation, and elevated temperature. A second species, L. micdadei is also implicated in the disease in immunocompromised patients. Both species are facultative intracellular pathogens which multiply within mononuclear phagocytes following ingestion or inhalation. They have also been observed to multiply in vacuoles of amoebae. Disease production is related to impairment of host defense mechanisms. A heat stable cytotoxin that blocks the oxidative metabolism of monocytes and neutrophils and production of a phosphatase enzyme that blocks superoxide production by neutrophils are implicated in the pathogenesis of the disease. Legionella are quite susceptible to erythromycin.
Legionnaire’s Disease and Severe Pneumonia Mimics in the Critical Care Unit
Published in Cheston B. Cunha, Burke A. Cunha, Infectious Diseases and Antimicrobial Stewardship in Critical Care Medicine, 2020
Legionnaire’s disease is usually accompanied by a variety of extrapulmonary findings, e.g., headache (HA), mental confusion, loose stools, and abdominal pain. Influenza may also present with HA and mental confusion; otherwise-unexplained loose stools in a CAP patient suggests influenza or M. pneumoniae as a diagnostic possibility. While Legionnaire’s disease is accompanied by fever (usually >102°F) + chills, influenza is characterized by severe rigors and myalgias with profound fatigues, not features of Legionnaire’s disease [31,32,35].
Legionella Pneumophila Infection
Published in Meera Chand, John Holton, Case Studies in Infection Control, 2018
Legionella spp. are found commonly in fresh water and soil. The number of bacteria in the source is a determining factor in the development of Legionnaires’ disease. Hospital-acquired outbreaks of Legionnaires’ disease have been reported repeatedly and are associated with potable water supplies rather than cooling towers. Many cases are not diagnosed because the signs and symptoms are nonspecific and many hospitals do not routinely test patients with hospital-acquired pneumonia. Detection of Legionella spp. in the water supply on routine testing increases the suspicion of Legionnaires’ disease and makes diagnosis more likely. Colonization of water supplies in large buildings is common, but showering is not a common means of transmission in hospitals. Most cases result from aspiration of oropharyngeal secretions and, hence, patients with chronic lung disease or recent surgery are most at risk.
Antibacterial carbonic anhydrase inhibitors: an update on the recent literature
Published in Expert Opinion on Therapeutic Patents, 2020
Claudiu T. Supuran, Clemente Capasso
Discovered 37 years ago, Legionella pneumophila is a Gram-negative environmental bacterium that usually infects amoeba [109,110]. However, this bacterium provoked life-threatening pneumonia-like disease in many participants to the 58th Annual Convention of the American Legion in Philadelphia in 1976, an occasion with which it was discovered. This condition was subsequently called Legionnaires’ disease or legionellosis. The bacterial pathogen was characterized in detail, being shown that a large number of its subspecies and serovars are widespread [109]. Two β-CAs were identified in the genome of L. pneumophila designated as LpCA1 (locus tag lpg2500, NCBI reference sequence WP_014844650.1), and LpCA2 (locus tag lpg2194; NCBI reference sequence WP_014842179.1) [62]. LpCA1 and LpCA2 CO2 hydrase activity was also determined. The first isoform, LpCA1 showed a moderate degree of activity with a kcat of 3.4 × 105 s−1 and kcat/KM of 4.7 × 107 M−1 s−1. This activity is comparable to that of other α- and β-CAs from different species. The second isoform, LpCA2, was on the other hand more active than LpCA1, with the following kinetic parameters: kcat of 8.3 × 105 s−1 and kcat/Km of 8.5 × 107 M−1 s−1.
Urinary antigen testing in community-acquired pneumonia in adults: an update
Published in Expert Review of Anti-infective Therapy, 2019
Diego Viasus, Laura Calatayud, María V. McBrown, Carmen Ardanuy, Jordi Carratalà
Several studies have assessed targeted antibiotic adjustment based on LUAT. Two single-centre retrospective cohort studies showed that a positive LUAT led to adequate treatment alterations in 22%-60% of cases [64,67]. Garbino et al. [66] evaluated 792 hospitalized CAP patients, of which 27 had positive LUAT; in two-thirds of the cases, the test had a direct impact on the clinical management of CAP. However, patient comorbidities and individual clinical judgment continue to be important for determining optimal treatment. In contrast, Dionne et al. [70] found that 62% of CAP patients, who were admitted from the emergency room or who had developed pneumonia in hospital, received empirical therapy for L. pneumophila but in 68% of these cases the treatment was not influenced by the negative LUAT. Furthermore, Lettinga et al. [83] analysed the effect of timely target treatment during an outbreak in the Netherlands. One hundred eighty-eight patients were identified with confirmed or probable Legionnaires’ disease during the outbreak, 141 required hospitalization, 40 ICU admission had confirmed disease, and 16 death. They finding that positive LUAT and early adequate therapy reduced the risk of intensive care unit admission and death by 38%.
Detection of amoeba-associated Legionella pneumophila in hospital water networks of Johannesburg
Published in Southern African Journal of Infectious Diseases, 2018
P Muchesa, M Leifels, L Jurzik, TG Barnard, C Bartie
Health-care-associated Legionnaires’ disease (LD) has been reported worldwide.25,26 In South Africa, the first investigation of an outbreak of LD in a Johannesburg teaching hospital in 1985 reported 12 cases in hospitalised patients, with two patients confirmed to have acquired the disease in the hospital.27 A more recent surveillance study of two South African hospitals by Wolter et al.28 reported Legionella in 21 (1.2%) cases of patients diagnosed with HIV or tuberculosis infections. However, this study did not aim to prove if the infections were acquired from the hospital environment. Hospital-associated LD cases in South Africa may be under-reported due to the lack of robust and reliable surveillance mechanisms and lack of accurate diagnosis. Routine sampling of hospital water supplies with the application of amoebal enrichment and co-culture techniques to resuscitate bacteria in the VBNC state can be effective strategies to prevent and manage hospital-acquired LD.5,29 Therefore, future work will focus on the detection of Legionella spp. from hospital water supplies and hospital surfaces, and comparing them with clinical samples. This will establish any link between occurrence of the organisms in the hospital environment with LD infection in patients using amoeba culture and molecular techniques. Knowledge on the occurrence of amoebae-associated L. pneumophila in the hospital water systems will also provide baseline information to monitor potential outbreaks that may be facilitated by their presence.