1.+Infectious+Agent+(ks982)

An infectious agent is a pathogen which can cause disease. Legionnaires disease is caused by the infectious agent l //egionella pnemophila//. This part is not needed, it should be integrated in the next paragraph.
 * //__ Infectious agents: [[image:http://www.asm.org/branch/brcano/96543c.jpg width="136" height="85" align="right" caption="(Fig 1) Scanning electron micrograph of L.pneumophila"]] __//**

Legionnella pneumophila is of the genus Legionella from the family Legionellaceae. Figure 1, shows a scanning electron micrograph of the infectious agent.There are many different species of Legionella with 53 species currently discovered. 70 serogroups of Legionella have been identified (Guyard 2011) with //L. pneumophila// being the primary human pathogenic bacterium in this group. //L. pneumophila// serogroup 1 alone is responsible for 95% of all cases of Legionnaires disease. (Valero.2009) Good, but the figure does not support your discussion.

L. pneumophila, pictured in figure 2 ? , are flagellated, non-capsulated, thin bacterium. They are aerobic, non-spore forming, gram negative cocco bacilli. The organism is approximately 2µm - 20µm in length and 0.3-0.9µm in width. The cell envelope is composed of branched-chain fatty acids and distinctive ubiquinones, whose structural differences have been used to classify different Legionella species. In infected tissue and clinical specimens, the organisms are coccobacillary and often measure 1–2 μm.

The optimum growth temperature for the bacteria is 35 degrees Celsius. At low temperatures the bacterium enters a dormant stage until exposed to more favourable conditions. L.pneumophila thrives in areas where there are high concentrations of rust and organic particles.Providing the bacteria with a source of iron and nitrogen necessary for growth, as well as protection from harsh chemicals. Mostly copied and pasted

Legionella Pneumophila are normally found in aquatic environments such as lakes and ponds. They act as intracellular pathogens of amoebae and in biofilms. Biofilms are highly efficient and stable ecosystems where resident L.pneumophila are well adapted to survive prolonged periods of environmental stress. L. pneumophila are spread primarily by water, but can colonize in any warm, damp environments and manmade water systems such as air conditioning and hot water systems. (Guyard.2011)

There is a parasitic relationship between Legionella and some of its protozoan hosts like Hartmanella vermiformi and Acanthamoeba Castellanies. The bacterium is able to invade and then multiply in the host. Growth of L. pneumophila in certain protozoan such as Acanthamoeba castellanii enhances the invasion of epithelial cell macrophage in humans. __A cycle of replication within amoebic hosts increases the virulence in humans improving their ability to replicate inside eukaryotic cells such as macrophages, epithelial and endothelial cells. (Declerck.2007) __ This part is good, most of the previous 2 paragraphs are not relevant to this topic, it would be better placed in Epidemiology

Humans become infected with the bacterium by inhaling aerosols from the contaminated water sources. L. pneumophila bacterium causes disease in humans by replicating inside alveolar macrophages. Virulent forms of the L. pneumophila bacterium have an ability to prevent phagosome to lysosome fusion, resulting in severe pneumonia known as legionnaires disease. Non virulent strains of the L. pneumophila species are unable to cause disease as they are defective in replicating inside the host cell. (Cianciotto.2001). Figure 3, shows how the bacterium enters a human host and replicates to cause disease. good

The virulence of the l. pneumophila, depends on its species specific genes. Salt sensitivity, motility and the presence of contact dependent cytotoxicity have an ability to affect the function of the dot/icm system. The inactivation of the defective for organelle trafficking/intracellular multiplication (dof/icm) gene results in the inhibition of the phagosome- lysosome fusion preventing intracellular growth in a host. (Vogel.1999) This should be part of pathogenicity

Legionella are gram negative bacilli which do not grow on routine media used in microbiology. They require complex nutritional requirements such as high cysteine levels, iron and low sodium levels to grow. As a result it is often difficult to isolate and identify outside of the host.

In conclusion the Patient can be diagnosed with legionnaires disease. It has been caused by an infection of the gram negative bacteria l. pneumophila. The patient has acquired the infection by inhaling the aerosols from a contaminated water source and it seems to be community acquired infection. Legionella are gram negative bacilli which do not grow on routine media used in Bacteriology. It requires complex nutritional requirements present in buffered charcoal yeast extract. The growth of the patients infectious agent on the BCYE plate is characteristic of l.pneumophila. The unretained crystal violet dye on the gram staining of the bronchial wash identified the
 * __Conclusion:__**

agent to be gram negative which is also another characteristic of l. Pneumophila.

Admin (2011) //Legionellosis,// [Internet], About Health, Last accessed on October 22nd 2011 at URL: [] (fig 2)
 * __References:__**

Bock, R. (2011), //Key step identified in Legionnaire’s disease infection process,// [Internet], NIH NEWS, National institutes of health, Last accessed on October 15th 2011 at URL: [] (fig3)

Cianciotto, N. (2001), Pathogenicity of Legionella Pneumophila//, International journal of medical microbiology//, **291**: 331-343

Declerck, P. (2007), Replication of Legionella pneumophila in biofilms of water distribution pipes, //Microbiological reasearch,// **164**: 593-603

Guyard, C. (2011//),// Legionella infections and travel associated legionellosis//,// //Travel medicine and infectious disease//, //**9:**//176-186

Kunkel, D. (2004), //Scanning Electron Micrograph of L. Pneumophila, // [internet], NCASM July case study, Last accessed on Oct 15th 2011 at URL: [] (fig 1)

Valero, L. (2009), Legionella pneumophila:population genetics phylogeny and genomics ,//Infection genetics and evolution//, **9**:727-739

Vogel, J. (1999), Cell biology of Legionella Pneumophila//,// //Current opinion in microbiology//, **2**:30-34

Some interesting data were reported and discussed, but you wrote more than the required 500 words and have not been able to identify what was most relevant to your topic and have stretched your discussion to your colleagues' topics. This is something that should have been identified and solved during meetings,