Legionella pneumophila
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''Legionella pneumophila'' is a thin,
aerobic Aerobic means "requiring air," in which "air" usually means oxygen. Aerobic may also refer to * Aerobic exercise, prolonged exercise of moderate intensity * Aerobics, a form of aerobic exercise * Aerobic respiration, the aerobic process of cel ...
, pleomorphic, flagellated, non-spore-forming,
Gram-negative Gram-negative bacteria are bacteria that do not retain the crystal violet stain used in the Gram staining method of bacterial differentiation. They are characterized by their cell envelopes, which are composed of a thin peptidoglycan cell wall ...
bacterium of the genus ''
Legionella ''Legionella'' is a genus of pathogenic gram-negative bacteria that includes the species '' L. pneumophila'', causing legionellosis (all illnesses caused by ''Legionella'') including a pneumonia-type illness called Legionnaires' disease and a mil ...
''. ''L. pneumophila'' is the primary human
pathogenic bacterium Pathogenic bacteria are bacteria that can cause disease. This article focuses on the bacteria that are pathogenic to humans. Most species of bacteria are harmless and are often beneficial but others can cause infectious diseases. The number of t ...
in this group and is the causative agent of
Legionnaires' disease Legionnaires' disease is a form of atypical pneumonia caused by any species of ''Legionella'' bacteria, quite often '' Legionella pneumophila''. Signs and symptoms include cough, shortness of breath, high fever, muscle pains, and headaches. Naus ...
, also known as legionellosis. In nature, ''L. pneumophila'' infects freshwater and soil
amoeba An amoeba (; less commonly spelled ameba or amœba; plural ''am(o)ebas'' or ''am(o)ebae'' ), often called an amoeboid, is a type of Cell (biology), cell or unicellular organism with the ability to alter its shape, primarily by extending and ret ...
e of the genera ''
Acanthamoeba ''Acanthamoeba'' is a genus of amoebae that are commonly recovered from soil, fresh water, and other habitats. ''Acanthamoeba'' has two evolutive forms, the metabolically active trophozoite and a dormant, stress-resistant cyst. Trophozoites are ...
'' and ''
Naegleria ''Naegleria'' is a free living amoebae protist genus consisting of 47 described species often found in warm aquatic environments as well as soil habitats worldwide. It has three life cycle forms: the amoeboid stage, the cyst stage, and the flage ...
''. The mechanism of infection is similar in amoeba and human cells.


Characterization

''L. pneumophila'' is a Gram-negative, non-encapsulated, aerobic bacillus with a single, polar flagellum often characterized as being a
coccobacillus A coccobacillus (plural coccobacilli), or bacilluscocco, is a type of bacterium with a shape intermediate between cocci (spherical bacteria) and bacilli (rod-shaped bacteria). Coccobacilli, then, are very short rods which may be mistaken for coc ...
. It is
aerobic Aerobic means "requiring air," in which "air" usually means oxygen. Aerobic may also refer to * Aerobic exercise, prolonged exercise of moderate intensity * Aerobics, a form of aerobic exercise * Aerobic respiration, the aerobic process of cel ...
and unable to
hydrolyse Hydrolysis (; ) is any chemical reaction in which a molecule of water breaks one or more chemical bonds. The term is used broadly for substitution, elimination, and solvation reactions in which water is the nucleophile. Biological hydrolys ...
gelatin Gelatin or gelatine (from la, gelatus meaning "stiff" or "frozen") is a translucent, colorless, flavorless food ingredient, commonly derived from collagen taken from animal body parts. It is brittle when dry and rubbery when moist. It may also ...
or produce
urease Ureases (), functionally, belong to the superfamily of amidohydrolases and phosphotriesterases. Ureases are found in numerous bacteria, fungi, algae, plants, and some invertebrates, as well as in soils, as a soil enzyme. They are nickel-contai ...
. It is also non- fermentative. ''L. pneumophila'' is neither
pigment A pigment is a colored material that is completely or nearly insoluble in water. In contrast, dyes are typically soluble, at least at some stage in their use. Generally dyes are often organic compounds whereas pigments are often inorganic compo ...
ed nor does it autofluoresce. It is
oxidase In biochemistry, an oxidase is an enzyme that catalyzes oxidation-reduction reactions, especially one involving dioxygen (O2) as the electron acceptor. In reactions involving donation of a hydrogen atom, oxygen is reduced to water (H2O) or hydro ...
- and
catalase Catalase is a common enzyme found in nearly all living organisms exposed to oxygen (such as bacteria, plants, and animals) which catalyzes the decomposition of hydrogen peroxide to water and oxygen. It is a very important enzyme in protecting t ...
-positive, and produces
beta-lactamase Beta-lactamases, (β-lactamases) are enzymes () produced by bacteria that provide multi-resistance to beta-lactam antibiotics such as penicillins, cephalosporins, cephamycins, monobactams and carbapenems ( ertapenem), although carbap ...
. ''L. pneumophila'' colony morphology is gray-white with a textured, cut-glass appearance; it also requires
cysteine Cysteine (symbol Cys or C; ) is a semiessential proteinogenic amino acid with the formula . The thiol side chain in cysteine often participates in enzymatic reactions as a nucleophile. When present as a deprotonated catalytic residue, sometime ...
and
iron Iron () is a chemical element with symbol Fe (from la, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, right in f ...
to thrive. It grows on
yeast extract agar Yeast extract agar is a growth medium containing yeast extract. It may refer to: * The nonselective yeast extract agar of Windle Taylor * YM (selective medium), for yeasts and molds * Buffered charcoal yeast extract agar Buffered charcoal yeast e ...
in "opal-like" colonies.


Cell membrane structure

While ''L. pneumophila'' is categorized as a Gram-negative organism, it stains poorly due to its unique
lipopolysaccharide Lipopolysaccharides (LPS) are large molecules consisting of a lipid and a polysaccharide that are bacterial toxins. They are composed of an O-antigen, an outer core, and an inner core all joined by a covalent bond, and are found in the outer m ...
content in the outer leaflet of the outer cell membrane. The bases for the somatic
antigen In immunology, an antigen (Ag) is a molecule or molecular structure or any foreign particulate matter or a pollen grain that can bind to a specific antibody or T-cell receptor. The presence of antigens in the body may trigger an immune response. ...
specificity of this organism are located on the side chains of its cell wall. The chemical composition of these side chains both with respect to components and arrangement of the different sugars, determines the nature of the somatic or O-
antigenic determinants An epitope, also known as antigenic determinant, is the part of an antigen that is recognized by the immune system, specifically by antibodies, B cells, or T cells. The epitope is the specific piece of the antigen to which an antibody binds. The p ...
, which are important means of serologically classifying many Gram-negative bacteria. At least 35 different
serovar A serotype or serovar is a distinct variation within a species of bacteria or virus or among immune cells of different individuals. These microorganisms, viruses, or cells are classified together based on their surface antigens, allowing the epi ...
s of ''L. pneumophila'' have been described, as well as several other species being subdivided into a number of serovars.


Detection

Sera have been used both for slide
agglutination In linguistics, agglutination is a morphological process in which words are formed by stringing together morphemes, each of which corresponds to a single syntactic feature. Languages that use agglutination widely are called agglutinative lang ...
studies and for direct detection of bacteria in tissues using immunofluorescence via
fluorescent Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation. It is a form of luminescence. In most cases, the emitted light has a longer wavelength, and therefore a lower photon energy, tha ...
-labelled
antibody An antibody (Ab), also known as an immunoglobulin (Ig), is a large, Y-shaped protein used by the immune system to identify and neutralize foreign objects such as pathogenic bacteria and viruses. The antibody recognizes a unique molecule of the ...
. Specific antibody in patients can be determined by the indirect fluorescent antibody test.
ELISA The enzyme-linked immunosorbent assay (ELISA) (, ) is a commonly used analytical biochemistry assay, first described by Eva Engvall and Peter Perlmann in 1971. The assay uses a solid-phase type of enzyme immunoassay (EIA) to detect the presence ...
and microagglutination tests have also been successfully applied. ''Legionella'' stains poorly with Gram stain, stains positive with silver, and is cultured on charcoal yeast extract with iron and cysteine.


Ecology and reservoirs

''L. pneumophila'' is a
facultative intracellular parasite Intracellular parasites are microparasites that are capable of growing and reproducing inside the cells of a host. Types of parasites There are two main types of intracellular parasites: Facultative and Obligate. Facultative intracellular pa ...
that can invade and replicate inside
amoebae An amoeba (; less commonly spelled ameba or amœba; plural ''am(o)ebas'' or ''am(o)ebae'' ), often called an amoeboid, is a type of cell or unicellular organism with the ability to alter its shape, primarily by extending and retracting pseudopo ...
in the environment, especially species of the genera ''
Acanthamoeba ''Acanthamoeba'' is a genus of amoebae that are commonly recovered from soil, fresh water, and other habitats. ''Acanthamoeba'' has two evolutive forms, the metabolically active trophozoite and a dormant, stress-resistant cyst. Trophozoites are ...
'' and ''
Naegleria ''Naegleria'' is a free living amoebae protist genus consisting of 47 described species often found in warm aquatic environments as well as soil habitats worldwide. It has three life cycle forms: the amoeboid stage, the cyst stage, and the flage ...
'', which can thus serve as a reservoir for ''L. pneumophila.'' These
hosts A host is a person responsible for guests at an event or for providing hospitality during it. Host may also refer to: Places *Host, Pennsylvania, a village in Berks County People *Jim Host (born 1937), American businessman *Michel Host ( ...
also provide protection from environmental stresses, such as
chlorination Chlorination may refer to: * Chlorination reaction In chemistry, halogenation is a chemical reaction that entails the introduction of one or more halogens into a compound. Halide-containing compounds are pervasive, making this type of transform ...
. Legionella has been shown to proliferate on the walls of pipes in biofilms. Sloughed legionella from biofilms in plumbing systems can be aerosolized through faucets, showers, sprinklers, and other fixtures which can lead to infection after prolonged exposure.


Frequency of occurrence

In the United States, approximately 3 infections with ''L. pneumophila'' appear per 100,000 people per year. The infections peak in the summer. Within endemic regions, about 4% to 5% of
pneumonia Pneumonia is an inflammatory condition of the lung primarily affecting the small air sacs known as alveoli. Symptoms typically include some combination of productive or dry cough, chest pain, fever, and difficulty breathing. The severity ...
cases are caused by ''L. pneumophila''.


Pathogenesis

In humans, ''L. pneumophila'' invades and replicates inside
macrophage Macrophages (abbreviated as M φ, MΦ or MP) ( el, large eaters, from Greek ''μακρός'' (') = large, ''φαγεῖν'' (') = to eat) are a type of white blood cell of the immune system that engulfs and digests pathogens, such as cancer cel ...
s. The internalization of the bacteria can be enhanced by the presence of
antibody An antibody (Ab), also known as an immunoglobulin (Ig), is a large, Y-shaped protein used by the immune system to identify and neutralize foreign objects such as pathogenic bacteria and viruses. The antibody recognizes a unique molecule of the ...
and
complement A complement is something that completes something else. Complement may refer specifically to: The arts * Complement (music), an interval that, when added to another, spans an octave ** Aggregate complementation, the separation of pitch-clas ...
, but is not absolutely required. Internalization of the bacteria appears to occur through
phagocytosis Phagocytosis () is the process by which a cell uses its plasma membrane to engulf a large particle (≥ 0.5 μm), giving rise to an internal compartment called the phagosome. It is one type of endocytosis. A cell that performs phagocytosis is ...
. However, ''L. pneumophila'' is also capable of infecting non-phagocytic cells through an unknown mechanism. A rare form of phagocytosis known as coiling phagocytosis has been described for ''L. pneumophila'', but this is not dependent on the Dot/Icm (intracellular multiplication/defect in organelle trafficking genes) bacterial secretion system and has been observed for other pathogens. Once internalized, the bacteria surround themselves in a membrane-bound
vacuole A vacuole () is a membrane-bound organelle which is present in plant and fungal cells and some protist, animal, and bacterial cells. Vacuoles are essentially enclosed compartments which are filled with water containing inorganic and organic mo ...
that does not fuse with
lysosomes A lysosome () is a membrane-bound organelle found in many animal cells. They are spherical vesicles that contain hydrolytic enzymes that can break down many kinds of biomolecules. A lysosome has a specific composition, of both its membrane prote ...
that would otherwise degrade the bacteria. In this protected compartment, the bacteria multiply.


Dot/Icm type IV secretion system and effector proteins

The bacteria use a type IVB secretion system known as Dot/Icm to inject effector proteins into the host. These effectors are involved in increasing the bacteria's ability to survive inside the host cell. ''L. pneumophila'' encodes for over 330 "effector" proteins, which are secreted by the Dot/Icm translocation system to interfere with host cell processes to aid bacterial survival. It has been predicted that the genus ''Legionella'' encodes more than 10,000 and possibly up to ~18,000 effectors that have a high probability to be secreted into their host cells. One key way in which ''L. pneumophila'' uses its effector proteins is to interfere with fusion of the ''Legionella''-containing vacuole with the host's
endosome Endosomes are a collection of intracellular sorting organelles in eukaryotic cells. They are parts of endocytic membrane transport pathway originating from the trans Golgi network. Molecules or ligands internalized from the plasma membrane can ...
s, and thus protect against lysis. Knock-out studies of Dot/Icm translocated effectors indicate that they are vital for the intracellular survival of the bacterium, but many individual effector proteins are thought to function redundantly, in that single-effector knock-outs rarely impede intracellular survival. This high number of translocated effector proteins and their redundancy is likely a result of the bacterium having evolved in many different
protozoan Protozoa (singular: protozoan or protozoon; alternative plural: protozoans) are a group of single-celled eukaryotes, either free-living or parasitic, that feed on organic matter such as other microorganisms or organic tissues and debris. Histo ...
hosts.


''Legionella''-containing vacuole

For ''Legionella'' to survive within macrophages and protozoa, it must create a specialized compartment known as the ''Legionella''-containing vacuole (LCV). Through the action of the Dot/Icm secretion system, the bacteria are able to prevent degradation by the normal endosomal trafficking pathway and instead replicate. Shortly after internalization, the bacteria specifically recruit
endoplasmic reticulum The endoplasmic reticulum (ER) is, in essence, the transportation system of the eukaryotic cell, and has many other important functions such as protein folding. It is a type of organelle made up of two subunits – rough endoplasmic reticulum ( ...
-derived vesicles and
mitochondria A mitochondrion (; ) is an organelle found in the Cell (biology), cells of most Eukaryotes, such as animals, plants and Fungus, fungi. Mitochondria have a double lipid bilayer, membrane structure and use aerobic respiration to generate adenosi ...
to the LCV while preventing the recruitment of endosomal markers such as
Rab5a Ras-related protein Rab-5A is a protein that in humans is encoded by the ''RAB5A'' gene. Function RAB5A localizes to early endosomes where it is involved in the recruitment of RAB7A and the maturation of these compartments to late endosomes. I ...
and
Rab7a Ras-related protein Rab-7a is a protein that in humans is encoded by the ''RAB7A'' gene. Ras-related protein Rab-7a is involved in endocytosis, which is a process that brings substances into a cell. The process of endocytosis works by folding the ...
. Formation and maintenance of the vacuoles are crucial for pathogenesis; bacteria lacking the Dot/Icm secretion system are not pathogenic and cannot replicate within cells, while deletion of the Dot/Icm effector SdhA results in destabilization of the vacuolar membrane and no bacterial replication.


Nutrient acquisition

Legionella is
auxotrophic Auxotrophy ( grc, αὐξάνω "to increase"; ''τροφή'' "nourishment") is the inability of an organism to synthesize a particular organic compound required for its growth (as defined by IUPAC). An auxotroph is an organism that displays this ...
for seven amino acids: cysteine, leucine, methionine, valine, threonine, isoleucine, and arginine. Once inside the host cell, ''Legionella'' needs nutrients to grow and reproduce. Inside the vacuole, nutrient availability is low; the high demand of
amino acids Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although hundreds of amino acids exist in nature, by far the most important are the alpha-amino acids, which comprise proteins. Only 22 alpha am ...
is not covered by the transport of free amino acids found in the host
cytoplasm In cell biology, the cytoplasm is all of the material within a eukaryotic cell, enclosed by the cell membrane, except for the cell nucleus. The material inside the nucleus and contained within the nuclear membrane is termed the nucleoplasm. The ...
. To improve the availability of amino acids, the parasite promotes the host mechanisms of proteasomal degradation. This generates an excess of free amino acids in the cytoplasm of ''L. pneumophila''-infected cells that can be used for intravacuolar proliferation of the parasite. To obtain amino acids, ''L. pneumophila'' uses the AnkB F-Box effector, which is farnesylated by the activity of three host enzymes localized in the membrane of the LCV:
farnesyltransferase Farnesyltransferase () is one of the three enzymes in the prenyltransferase group. Farnesyltransferase (FTase) adds a 15-carbon isoprenoid called a farnesyl group to proteins bearing a CaaX motif: a four-amino acid sequence at the carboxyl ter ...
, Ras-converting enzyme-1 protease, and '' ICMT''.
Farnesylation Prenylation (also known as isoprenylation or lipidation) is the addition of hydrophobic molecules to a protein or a biomolecule. It is usually assumed that prenyl groups (3-methylbut-2-en-1-yl) facilitate attachment to cell membranes, similar to ...
allows AnkB to get anchored into the cytoplasmic side of the vacuole. Once AnkB is anchored into the LCV membrane, it interacts with the SCF1
ubiquitin ligase A ubiquitin ligase (also called an E3 ubiquitin ligase) is a protein that recruits an E2 ubiquitin-conjugating enzyme that has been loaded with ubiquitin, recognizes a protein substrate, and assists or directly catalyzes the transfer of ubiquitin ...
complex and functions as a platform for the docking of K48-linked polyubiquitinated proteins to the LCV. The K48-linked polyubiquitination is a marker for proteasomal degradation that releases two- to 24-amino-acid-long peptides, which are quickly degraded to amino acids by various
oligopeptidase An Oligopeptidase is an enzyme that cleaves peptides but not proteins. This property is due to its structure: the active site of this enzyme is located at the end of a narrow cavity which can only be reached by peptides. History Background P ...
s and
aminopeptidase Aminopeptidases are enzymes that catalyze the cleavage of amino acids from the amino terminus ( N-terminus) of proteins or peptides (exopeptidases). They are widely distributed throughout the animal and plant kingdoms and are found in many subcel ...
s present in the cytoplasm. Amino acids are imported into the LCV through various amino acid transporters such as the neutral amino acid transporter B(0). The amino acids are the primary carbon and energy source of ''L. pneumophila'', that have almost 12 classes of ABC-transporters, amino acid permeases, and many
proteases A protease (also called a peptidase, proteinase, or proteolytic enzyme) is an enzyme that catalyzes (increases reaction rate or "speeds up") proteolysis, breaking down proteins into smaller polypeptides or single amino acids, and spurring the for ...
, to exploit it. The imported amino acids are used by ''L. pneumophila'' to generate energy through the
TCA cycle The citric acid cycle (CAC)—also known as the Krebs cycle or the TCA cycle (tricarboxylic acid cycle)—is a series of chemical reactions to release stored energy through the oxidation of acetyl-CoA derived from carbohydrates, fats, and protein ...
(Krebs cycle) and as sources of carbon and nitrogen. However, promotion of proteasomal degradation for the obtention of amino acids may not be the only
virulence Virulence is a pathogen's or microorganism's ability to cause damage to a host. In most, especially in animal systems, virulence refers to the degree of damage caused by a microbe to its host. The pathogenicity of an organism—its ability to ca ...
strategy to obtain carbon and energy sources from the host. Type II–secreted degradative enzymes may provide an additional strategy to generate carbon and energy sources.


Genomics

The determination and publication of the complete genome sequences of three clinical ''L. pneumophila'' isolates in 2004 paved the way for the understanding of the molecular biology of ''L. pneumophila'' in particular and ''Legionella'' in general. In-depth comparative genome analysis using DNA arrays to study the gene content of 180 ''Legionella'' strains revealed high genome plasticity and frequent
horizontal gene transfer Horizontal gene transfer (HGT) or lateral gene transfer (LGT) is the movement of genetic material between Unicellular organism, unicellular and/or multicellular organisms other than by the ("vertical") transmission of DNA from parent to offsprin ...
. Further insight in the ''L. pneumophila''
lifecycle Life cycle, life-cycle, or lifecycle may refer to: Science and academia * Biological life cycle, the sequence of life stages that an organism undergoes from birth to reproduction ending with the production of the offspring *Life-cycle hypothesis ...
was gained by investigating the gene expression profile of ''L. pneumophila'' in ''Acanthamoeba castellanii'', its natural host. ''L. pneumophila'' exhibits a biphasic lifecycle and defines transmissive and replicative traits according to gene expression profiles.


Genetic transformation

Transformation Transformation may refer to: Science and mathematics In biology and medicine * Metamorphosis, the biological process of changing physical form after birth or hatching * Malignant transformation, the process of cells becoming cancerous * Trans ...
is a bacterial adaptation involving the transfer of DNA from one bacterium to another through the surrounding liquid medium. Transformation is a bacterial form of
sexual reproduction Sexual reproduction is a type of reproduction that involves a complex life cycle in which a gamete ( haploid reproductive cells, such as a sperm or egg cell) with a single set of chromosomes combines with another gamete to produce a zygote tha ...
. In order for a bacterium to bind, take up, and recombine exogenous DNA into its chromosome, it must enter a special physiological state referred to as " competence". To determine which molecules may induce competence in ''L. pneumophila'', 64 toxic molecules were tested. Only six of these molecules, all DNA-damaging agents, caused strong induction of competence. These were
mitomycin C Mitomycin C is a mitomycin that is used as a chemotherapeutic agent by virtue of its antitumour activity. Medical uses It is given intravenously to treat upper gastro-intestinal cancers (e.g. esophageal carcinoma), anal cancers, and breast c ...
(which introduces DNA inter-strand crosslinks),
norfloxacin Norfloxacin, sold under the brand name Noroxin among others, is an antibiotic that belongs to the class of fluoroquinolone antibiotics. It is used to treat urinary tract infections, gynecological infections, inflammation of the prostate gland, g ...
,
ofloxacin Ofloxacin is a quinolone antibiotic useful for the treatment of a number of bacterial infections. When taken Oral administration, by mouth or intravenous, injection into a vein, these include pneumonia, cellulitis, urinary tract infections, prost ...
, and
nalidixic acid Nalidixic acid (tradenames Nevigramon, NegGram, Wintomylon and WIN 18,320) is the first of the synthetic quinolone antibiotics. In a technical sense, it is a naphthyridone, not a quinolone: its ring structure is a 1,8-naphthyridine nucleus that ...
(inhibitors of
DNA gyrase DNA gyrase, or simply gyrase, is an enzyme within the class of topoisomerase and is a subclass of Type II topoisomerases that reduces topological strain in an ATP dependent manner while double-stranded DNA is being unwound by elongating RNA-poly ...
that cause double-strand breaks),
bicyclomycin Bicyclomycin (Bicozamycin) is a broad spectrum antibiotic active against Gram-negative bacteria and the Gram-positive bacterium, ''Micrococcus luteus'' that was isolated from ''Streptomyces sapporonesis'' and ''Streptomyces aizumenses'' in 1972. ...
(causes double-strand breaks), and
hydroxyurea Hydroxycarbamide, also known as hydroxyurea, is a medication used in sickle-cell disease, essential thrombocythemia, chronic myelogenous leukemia, polycythemia vera, and cervical cancer. In sickle-cell disease it increases fetal hemoglobin and d ...
(causes oxidation of DNA bases). These results suggest that competence for transformation in ''L. pneumophilia'' evolved as a response to
DNA damage DNA repair is a collection of processes by which a cell identifies and corrects damage to the DNA molecules that encode its genome. In human cells, both normal metabolic activities and environmental factors such as radiation can cause DNA da ...
. Perhaps induction of competence provides a survival advantage in a natural host, as occurs with other pathogenic bacteria.


Drug Targets

Several enzymes in the bacteria have been proposed as tentative drug targets. For example, enzymes in the iron uptake pathway have been suggested as important drug targets. Further, a cN-II class of IMP/GMP specific 5´-nucleotidase which has been extensively characterized kinetically. The tetrameric enzyme shows aspects of positive homotropic cooperativity, substrate activation and presents a unique
allosteric site In biochemistry, allosteric regulation (or allosteric control) is the regulation of an enzyme by binding an effector molecule at a site other than the enzyme's active site. The site to which the effector binds is termed the ''allosteric site ...
that can be targeted to design effective drugs against the enzyme and thus, the organism. Moreover, the enzyme is distinct than its human counterpart making it an attractive target for drug development.


Treatment

Macrolides The Macrolides are a class of natural products that consist of a large macrocyclic lactone ring to which one or more deoxy sugars, usually cladinose and desosamine, may be attached. The lactone rings are usually 14-, 15-, or 16-membered. Macro ...
(
azithromycin Azithromycin, sold under the brand names Zithromax (in oral form) and Azasite (as an eye drop), is an antibiotic medication used for the treatment of a number of bacterial infections. This includes middle ear infections, strep throat, pneumon ...
or
clarithromycin Clarithromycin, sold under the brand name Biaxin among others, is an antibiotic used to treat various bacterial infections. This includes strep throat, pneumonia, skin infections, ''H. pylori'' infection, and Lyme disease, among others. Clarith ...
) or
fluoroquinolones A quinolone antibiotic is a member of a large group of broad-spectrum antibiotic, broad-spectrum bacteriocidals that share a bicyclic molecule, bicyclic core structure related to the substance 4-Quinolone, 4-quinolone. They are used in human and ...
(
levofloxacin Levofloxacin, sold under the brand name Levaquin among others, is an antibiotic medication. It is used to treat a number of bacterial infections including acute bacterial sinusitis, pneumonia, H. pylori (in combination with other medications), ...
or
moxifloxacin Moxifloxacin is an antibiotic, used to treat bacterial infections, including pneumonia, conjunctivitis, endocarditis, tuberculosis, and sinusitis. It can be given by mouth, by injection into a vein, and as an eye drop. Common side effects in ...
) are the standard treatment for ''Legionella'' pneumonia in humans, with levofloxacin being considered first line with increasing resistance to azithromycin. Two studies support superiority of levofloxacin over macrolides, although not FDA approved.The Sanford Guide to Antimicrobial Therapy 2013


References


External links


Major topic "Legionella pneumophila": free-full text articles in PubMedLegionella pneumophila, causative agent of Legionnaire's disease and Pontiac fever at MetaPathogenType strain of ''Legionella pneumophila'' at Bac''Dive'' - the Bacterial Diversity Metadatabase
{{Taxonbar, from=Q147885 Legionellales Gram-negative bacteria Bacteria described in 1979