# _Legionella pneumophila_--Virulence Factors and the Possibility of Infection in Dental Practice
###### Abstract  
_Legionella pneumophila_ is defined as a bacterium that can cause severe pneumonia. It is found in the natural environment and in water, and is often found in water tanks. It can be an integral part of biofilms in nature, and the protozoa in which it can live provide it with food and protect it from harmful influences; therefore, it has the ability to move into a sustainable but uncultured state (VBNC). _L. pneumophila_ has been shown to cause infections in dental practices. The most common transmission route is aerosol generated in dental office water systems, which can negatively affect patients and healthcare professionals. The most common way of becoming infected with _L. pneumophila_ in a dental office is through water from dental instruments, and the dental unit. In addition to these bacteria, patients and the dental team may be exposed to other harmful bacteria and viruses. Therefore, it is vital that the dental team regularly maintains and decontaminates the dental unit, and sterilizes all accessories that come with it. In addition, regular water control in dental offices is necessary. a _A._e._g._a._a. _Legionella_ is found in the natural or artificial aquatic environment [22]. It occurs in planktonic form or as part of biofilms [23] and has the ability to move into a sustainable but uncultured state (VBNC) [19]. Elevated temperature, inorganic and organic water content, and the presence of protozoa play a crucial role in their growth and spread [24]. The most significant number of _Legionella_ is found in water samples with temperatures from 30 \({}^{\circ}\)C to 40 \({}^{\circ}\)C [25]. Infections in humans occur exclusively by inhalation of contaminated aerosols, which can occur in air conditioning systems, cooling towers, spas, fountains, ice machines, plant sprayers, dental appliances, and showerheads [26]. The material from which the pipeline system is built significantly influences the appearance of high concentrations of bacteria (Figure 1) [5]. The use of copper as a plumbing material has been shown to help reduce the risk of Legionnaires' disease, while plastic materials support many _L. pneumoniae_ bacteria [27]. \begin{table}
\begin{tabular}{l c c} \hline \hline \multicolumn{1}{c}{**Characteristics**} & \multicolumn{1}{c}{_Legionella pneumophila_} & \multicolumn{1}{c}{**References**} \\ \hline Family & _Legionellaceae_ & [15] \\ Form & bacillus & [1] \\ Coloring per gram & Gram (-) & [1] \\ Metabolism & Aerobic & [1] \\ pH & 5–8.5 & [16] \\ Habitat & Aquatic habitats (biofilm, within \\  & multicellular organisms) & [17] \\ Reproduction temperature & 25–37 \({}^{\circ}\)C & [18] \\ Survival temperature & 0–63 \({}^{\circ}\)C & [16] \\ Nutrients & Amino acids (L-cysteine), iron & [17] \\ Sensitivity & Drying, chlorine, UV radiation & [19] \\ \hline \hline \end{tabular}
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Table 1: Classification of _Legionella pneumophila_. \begin{table}
\begin{tabular}{l c c} \hline \hline \multicolumn{1}{c}{_Legionella_**sp.**} & \multicolumn{1}{c}{**Serogroups Associated**} & \multicolumn{1}{c}{**Diseases**} & \multicolumn{1}{c}{**Mortality Rate**} \\ \hline _L. anisa_ & & Pleural infection & \\ _L. bozemantii_ & 1 and 2 & Pneumonia & \\ _L. cardiaca_ & & Native endocarditis & \\ _L. cincinnatiensis_ & & Pneumonia & \\ _L. clemsonensis_ & & Pneumonia & \\ _L. dumoffii_ & & Legionnaires’ disease & \\ _Legionella feeleii_ & 1 and 2 & Pontiae fever & \\ _L. hackeliae_ & 1 and 2 & Pneumonia & \\ _L. jordanis_ & & Endocarditis & \\ _L. lansigensis_ & & Pneumonia & \\ _Legionella longbeachae_ & 1 and 2 & Pneumonia & \\ _L. macacheernii_ & & Pneumonia & \\ _L. micladaei_ & & Opportunistic & \\ _L. parisiensis_ & & Pneumonia & \\ _L. pneumoniae_ & & Pontiae fever, & \\ _L. pneumoniae_ & 1–15 & Legionnaires’ disease, & \\  & & and pneumonia & \\ \hline \hline \end{tabular}
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Table 2: _Legionella_ species, serogroup details, and their ability to cause human infection and mortality rate [7,17,20,21].