An Microbiological Overview of Salmonella Bacteria

Introduction

Salmonella is a bacteria that infects intestinal tract. It consists of a group of bacteria that leads to typhoid fever, gastroenteritis, enteric fever, and food poisoning. Naturally, the bacteria are rod-shaped, gram-negative and with a cell composed of peptidoglycan. In Microbiology, gram-negative is a bacteriology term meaning a bacteria that changes its color from violet stain to red counterstain in Gram’s methods of staining. According to Snyder et al. (2013), the Salmonella family composes of above 2,300 serotypes of microscopic single-celled bacteria. However, only two of the serotypes account for over 50 percent infections in the United States (Koivunen, 2003). Salmonella enteritidis and Salmonella typhimurium are the most infectious and inhabits the gut of infected animals and humans.

Microscopic, Cultivation, and Non-cultivation Methods

There are two primary microscopic methods used to detect and confirm the presence of Salmonella bacteria. First, there are the traditional methods that make use of colony appearance on chromogenic media (Koivunen, 2003). According to Koivunen (20023), Salmonella clinical samples are cultured onto the agar media and then incubated at 37 degrees delicious for 24 hours. The bred specimens are then taken under a microscope to detect the presence of the bacteria in the sample using bright-field microscopy. Rapid methods are also used to detect the presence of Salmonella (Koivunen, 2003). Using the traditional methods, identifying and confirming the specimen may take up to five days. However, rapid test methods allow the biologist to detect the presence of the bacteria in real time. Using this method, the specimen first undergoes enrichment stage using novel culture techniques such as immunomagnetic separation, and ELISA-based assays. The sample then undergoes fluorescent microscopy to detect the presence of the bacteria. Also, molecular techniques such as DNA hybridization and PCR-based detection are also applied to offer real-time detection of the bacteria (Koivunen, 2003).

Application to Clinical Microbiology Processing

Salmonella undergoes microbiology processing during identification and confirmation period. Currently, rapid methods are widely used to detect and confirm the presence of Salmonella. First, the confirmation tests are based on latex agglutination, enzyme-linked immunosorbent assay (ELISA), simple-to-use lateral flow test using immunochromatographic technology, and enzyme immunoassay (EIA) (Snyder et al., 2013). Secondly, microbiologists make use of molecular methods to confirm the presence of the bacteria. Such methods are notably DNA hybridization and PCR assays used in detecting Salmonella enterica Snyder et al., 2013).

Relationship with Humans

Salmonella lives in the intestines of people. Consuming food or intake of water contaminated with the bacteria leads to infection. Mostly, the disease originates from contaminated feces (Snyder et al., 2013). In the developed world, the spread of the disease is very minimal due to high hygienic levels. However, developing countries still has high infection rates. The bacteria can end up in the human guts through various ways. First, uncooked meat, seafood, and poultry may lead to infection especially when the meat is contaminated during slaughtering (Snyder et al., 2013). Secondly, contaminated fruits and vegetables are also an important cause of infection in human beings. Food and plants become contaminated due to washing with contaminated. Moreover, raw eggs may also contribute to disease in humans. When laid by an infected hen, the eggs contain the bacteria that made up ingested if the hands is not properly cleaned. Lastly, pets and amphibians also lead to infection in humans. Pets and bacteria carry the pathogen, but they do not become ill (Snyder et al., 2013). Their droppings in turn contaminate toys, clothes, and furniture. Consequently, the pathogen ends up in the human body. After infection, various Salmonella-induced gastroenteritis signs starts to show. Such symptoms includes stomach cramps, bloody stool, chills, diarrhea, headache, muscle pains, nausea, and vomiting (Snyder et al., 2013).

Analysis of Salmonella Virulence Factors

According to Levinson (1996), pathogens produce molecules that help them that helps them contribute to their pathogenicity. Such may be achieved through attachment to cells, evasion of the host’s immune system, entry into and out of cells, and obtaining nutrition from the host. Such molecules refer to virulence factors. Salmonella has four main virulence factors that help the pathogen accomplish the above. First, it has virulence plasmid. The plasmid is capable of restoring mouse virulence hence overcoming the host immune system. Moreover, the plasmid harbors 7.8 kb Salmonella plasmid virulence locus that carries five designated genes RABCD (Ochiai et al., 2008). The genes help in replication such that the host’s immune system is defenseless Secondly, the bacteria produces both endotoxins and exotoxins that can kill mammalian cells. Therefore, the bacteria can move into and out of the cell freely. Additionally, the bacteria have fimbriae consisting of filamentous surface structures made of helically arranged repeated proteins. The fimbriae cluster in a 7-9 kb operon capable of evading the host’s immune system. Lastly, flagella also constitute salmonellas’ virulence factor (Ochiai et al., 2008). The flagella are usually in groups of five to 10. The virulence phase variation enables it to overcome the host defense mechanism.

Various host factors increase the risk of contracting salmonella. First, international travels to developing increases the chances of an individual to contract the bacteria. Secondly, according to Ochiai et al. (2008) owning a pet bird or reptile also increase the chance of individual contracting the bacteria. He attributes the risk to the fact threat a bird and a pet act as they act as carriers in their digestive tract. Moreover, stomach and bowel disorders may reduce natural defense against the bacteria. Using antacids lowers the stomach acidity making allowing more of the bacteria to survive. Also, inflammatory bowel disease damages intestinal lining making the Salmonella bacteria take better hold onto the intestinal wall. Lastly, recent use of antibiotics reduces the number of good bacteria thereby inhibiting the host’s ability to fight off the bacteria (Ochiai et al., 2008). Lastly, immune problems such as AIDS, Malaria, sickle cell disease, and anti-rejection drugs taken after an organ transplant may increase an individual’s risk to contract the bacteria.

The diseases have varied importance on public health. First, the disease is host specific. As such, it can reside on individual hosts without causing illness (Ochiai et al., 2008). For example, Salmonella Dublin in cattle and Salmonella Choleraesuis in pigs do not affect the animals. However, in human beings, the bacteria have life-threatening effects. Such outcomes on public health include causing gastroenteritis, typhoid fever, and food poisoning. Lastly, the ease of transmission between one host to the other also makes the bacteria’s important public health outcome (Ochiai et al., 2008).

Treatment and prevention methods

According to World Health Organization (WHO), treating the symptom, rehydration, and electrolyte replacement forms the basic treatment procedures in adults (Ochiai et al., 2008). Electrolytic replacement entails providing the body with electrolytes such as potassium, sodium, and chloride ions lost during vomiting. Secondly, the younger and the elderly may require routine antimicrobial therapy though the method is not recommended for moderate cases of healthy individuals as it may not wipe the bacteria completely. Jane (2014) asserts that antimicrobial applies when the bacteria spread to other apart of the body apart from the intestines.

WHO outlines several methods that would help prevent spread and infection with the bacteria infections (Ochiai et al., 2008). First, eating properly cooked food and served while hot reduces the chance of ingesting the bacteria significantly. Secondly, avoiding using ice unless made from safe water reduces the chance of contracting the bacteria. Moreover, drinking boiled water help remove the bacteria contained in contaminated water (Ochiai et al., 2008). Furthermore, medics’ advice washing of hands with soaps before eating to reduces the chances of contaminating the food. Lastly, washing fruits and vegetables reduces the risk of spreading the diseases.