Legionella is a bacteria that is responsible for the disease known as Legionnaires disease, found in water droplets that have been dispensed in the air. In most cases, legionella leads to pneumonia and has been isolated in 40% of hospital pneumonia cultures.  The symptoms and treatments vary in most cases and depend on the severity of the infection. 

Legionella infection is known to have two variations. The first is severe and may or may not lead to pneumonia. This form of the disease  usually occurs from two to 10 days after exposure  but is known to occur up to 16 days later. The symptoms of this disease are cough, muscle aches, shortness of breath and fever that progresses into pneumonia.These symptoms can be long lasting and mimic the flu. Once infected and cultures of the bacteria can be made, the treatment is antibiotic treat with azithromycin. A chest x-ray can be used to show the infiltrates and pneumonia in the lungs. 

The second form of legionella infection is an illness known as Pontiac Fever. Pontiac Fever is the milder form of legionella infection and in most cases does not lead to pneumonia. This can occur from two hours to 2 days after exposure. The symptoms are similar to the first form of legionnaires disease, however, it resolves spontaneously. In a majority of Pontiac Fever cases, there aren’t any symptoms that develop. Lastly, Pontiac Fever does not require a treatment or hospitalization. Here is a news clip about a legionnaires disease outbreak within the last five years. 

Legionella pneumophila is a bacterium that can live a long life cycle that can be separated into two distinct phases. The two phases are known as the replication phase and the dispersal phase. The dispersal phase is the most important and dangerous phase of the legionella life cycle.

                In the dispersal phase, legionella is motile and able to move freely in an aqueous environment. The bacteria at this point, are seeking a warm suitable host to infect within or outside a bio-film. Once in dispersal phase, legionella changes shape and forms a thicker body with flagellum, making their new form more optimal for orientation towards the host cell. The dispersal phase in legionella is the most dangerous and is known to be when the bacterium is most virulent and pathogenic. This is virulence is due to the legionella’s increase probability of being taken up by aerosol droplets and dispersed by water droplets in contaminated water sources. Lastly, in this phase legionella is considered viable but cannot be cultured, so testing and detection of this bacterium is complex and difficult to conducted. 

                The replication phase of Legionella can only begin once the bacteria has attached to the surface of the host cell or amoeba. Legionella bacteria can reproduce both intracellularly and extracellularly, however extracellular replication is a rarity and depends on the extracellular conditions. The host cell or environment must maintain a temperature that is  between 22-55˚C (72-131˚F), to allow for replication to occur. Legionella’s principle replication is through binary fission, in which one bacterium can replicate and segregate its DNA to produce identical replicated cells. Once this phase has completed and legionella has depleted the host cell of nutrients, the bacteria evacuates the cell and the dispersal phase begins. 

Legionella is an aquatic bacterium that can be found in two distinctive shapes. The first is rod-shaped and the second is coccoid shaped, with both displaying three polar or lateral flagella. Legionella is characteristically single celled organisms that can survive in bio-films contained within man-made water sources. The legionella bacteria are gram-negative and largely aerobic and are capable of drawing energy from their hosts, therefore they are considered parasites of eukaryotic cells. Each legionella bacteria are measured to be between 300 nm-900 nm by  2000-3000 nm. Legionella are not highly motile unless they are contained within media that has a low salt concentration, in which they utilize their and are flagella. If contained within a high salt concentration media, Legionella, are found to not have any flagella present. Legionella are able to reproduce in two phases. The first is 

The genome of Legionella was sequenced and catalogued  into four strains. Each of sequences were collected from humans afflicted with Legionnaires disease. The strains were Philadelphia strain, Lens Strain, Corby strain, and the Paris strain. The Philadelphia strain was originally discovered in the original outbreak of the disease and the lens strain is responsible for 12% of cases in France. The actual genome consists of 3,259 predicted genes and 80% of these genes between the strains are the same, with 10% of genes within each strain being unique. This diversity within the genome of Legionella can be explained by its ability to perform horizontal gene transfer between each of the strains and other bacteria.

Hello! My name is Deah McMillan. For my blog project I decided to visit the CDC museum. The CDC museum is located in Atlanta, Georgia and is federally run. I chose this location because it is free and has a wide range of diseases to research. 

The CDC is responsible for research ad development of most vaccines that are available today and is instrumental in prevention of pandemics and epidemics from devastating the population. 

Legionnaires Disease is the topic of my blog project and I will be providing details about the bacteria, Legionella pneumophila. Legionella pneumophila is a gram-negative, water-borne, bacteria that is responsible for infections of the lungs. In the past, outbreak of this particular disease was subject of a mystery that led to the discovery of this previously unreported bacteria. 

As time goes on, we will explore the CDC’s discovery of Legionella pneumophila and how it reproduces and causes disease in humans.