Alexa Leach Research Project on Pathogens Life Sciences August 2012
Salmonella is a type of bacterial pathogen. Salmonella is the genus name for many closely
related bacteria that cause disease. It was named after the American veterinary pathologist, Daniel Elmer Salmon. Salmonella reproduces in the digestive tract in not only humans, but also animals. Salmonella causes Salmonellosis which is easily prevented and treatable, medically and homeopathically, however, still very common today and can even cause death, due to various environmental and socio-economic issues which aid to the spreading of this disease. The classification of Salmonella is rather complex. Salmonella is a type of bacteria, and thus belongs to the Kingdom Monera or Eubacteria and are Prokaryotic. Salmonella belongs to the phylum Proteobacteria and the class Gamma Proteobacteria . It belongs to the order Enterobacteriales, the family Enterobacteriaceae and the genus Salmonella. There are
approximately two thousand similar species of this type of bacteria. This has caused much confusion in terms of classifying each species. In order to simplify this, the Center for Disease Control and Prevention (CDC) has agreed upon two species of Salmonella. These consist of Salmonella enteritidis and Salmonella bongori . Each of these contains multiple subspecies into
multiple serotypes. Even today, thousands of these serotypes have not even been discovered and identified yet (Brenner, 2000). However, many scientists regard this as an incorrect classification, and say that there are thousands of species of Salmonella, such as Salmonella typhi, Salmonella cholera-suis and Salmonella enteritidis. Scientists are constantly trying to
agree upon classifying the various species and serotypes of Salmonella, however, due to the new discoveries and genetic mutations of each serotype, it may never be agreed upon. Salmonella is a rod-shaped virus and does not retain violet hue in the Gram staining procedure,
and thus Gram-negative. Gram -negative bacteria is pathogenic, which means it causes disease or harm to its host. It consists of a cell wall, cell membrane, cytoplasm, ribosomes, plasmids plasmids and nucleoid region. It has a diameter of around 0.7 to 1.5 µm, and a length from 2 to 5 µm. It has flagella which grades in all directions. This allows for locomotion. They are chemoorganotrophs. This means that they obtain energy from reduction and oxidation reactions of organic sources. It is also anaerobic, which means oxygen is not necessary to its survival. Salmonella can survive for several weeks outside of a living l iving host and is not destroyed by freezing temperatures. The bacteria will only be destroyed in temperatures above 75 °C which creates a problem is food is not properly washed or cooked.
Salmonella is transmitted by the consumption of raw food
that is contaminated with the bacteria, such as vegetables that have not been cooked or washed properly, or on meat or eggs. Salmonella can be transferred if the food handler or processor does not use gloves when dealing with food and has touched something contaminated, such as in a public bathroom without washing their hands. It can also be transmitted by reptiles or rodents through their feces. It therefore has a large host range, as it can be transmitted from a rodent, to a chicken to a human very easily. If the food is contaminated with a high concentration of the bacteria, the person is more likely to become infected. Children, elderly people and HIV positive people are more likely to become infected. Once ingested, the bacteria attacks the stomach and intestines. Incubation can take from a few hours to seventy-two hours. The bacteria imbeds itself into the intestinal lumen (as seen in the picture to the right) and reproduced. The liver, spleen and especially the gallbladder have a high concentration of Salmonella. If left untreated the disease can spread through the bloodstream to other joints, organs, placenta, and membranes around the brain. The toxins released by the bacteria can affect damage the rest of the body even further (Rogers, 2011). In more serious cases, the bacteria may enter the lymph tracts, which carry water and protein to the blood, and the blood itself. Salmonella mainly causes gastroenteritis (from non-typhoidal Salmonella) which is a type of food poisoning. Some serotypes can also cause Typhoid Fever,
whilst others are harmless. The general term for these infections is salmonellosis. Most people infected will develop diarrhea, abdominal cramps, fever and vomiting which can last up to a week. Other symptoms caused by Salmonella infection include: enlargement of the spleen and lymph nodes, accumulation of fluid and blood in organs such as the lungs, damage to the liver. In chronic cases, arthritis may even occur, which is known as Ruiters Syndrome and can last for months, or even years. Different symptoms will occur in different mammals and birds. This can be diagnosed by a doctor by mentioning foods you have eaten and seeing the symptoms you have, or a fecal test, and occasionally bloods tests, to confirm or determine the prognosis. Researchers are working toward a vaccine to prevent Salmonella, however, this is far from happening at the moment. Some Salmonella serotypes have become immune to antibiotics, however, this is still the dominant medication for Salmonellosis in the western world. Usually ampicillin or ciprofloxacin is administered. Often it is treatable at home, and only if the
symptoms get worse or are present for more than a few days, then antibiotics are
administered. If the infection is very severe, the person might have to go to hospital for treatment, such as intravenous fluids if severe dehydration occurs. Medication, like pain killers, may be prescribed to treat symptomatically. Various indigenous and alternative treatments are used around the world for people that may not be able to afford antibiotics for example. They drink plenty of fluids, especially garlic tea as garlic is reported to stunt the growth of Gramnegative bacteria. Arsenicum is also said to help with diarrhea, nausea and vomiting. Activated charcoal is also used in order to absorb and cleanse the intestines (Bardot, 2010). Oil of oregano is also used for its antimicrobial properties as it contains phenol which is used to destroy the Salmonella bacteria (Snyder 2009). Salmonella reproduces by binary fission. This is when a particular DNA molecule replicates and
both copies join to the cell membrane. This begins to grow between the two DNA molecules. Once the bacterium doubles its original size, the cell membrane begins to pinch inward. A cell wall then forms between the two DNA molecules. This divides the original cell into two identical daughter cells (Bailey, 2011). This is done within the intestinal lumen of the host. Once reproduced, the bacterium either stays within the intestine, or enters the bloodstream or lymph tracts. Salmonella is easily prevented. Food needs to be washed and cooked thoroughly. It is also
important to have good personal hygiene. If working with food, the person needs to wash their hands with antibacterial soap thoroughly before and after working with the food, and also clean the utensils and surfaces in which the food touched. Cross contamination of food needs to be avoided, such as cooked and non-cooked food. Hands need to be washed very well after touching any birds, reptiles or pets, and after going to the bathroom, especially in public areas. Rather breastfeed your baby, instead of using formulas mixed with milk, as infants are highly susceptible to acquiring the disease. Although Salmonella is preventable, thousands of people all over the world are diagnosed with it every year. Many socio-economic factors contribute to the spreading of this type of bacteria. The main factors are poverty and lack of education. Millions of people in the world are poor and do not have enough money to support their daily needs. This means they do not have the financial aid to get medical assistance if they are sick and often pass on the disease to the people around them unknowingly. They also do not have the proper education and money in order to have adequate sanitation and good hygiene. All of this aids to the spreading of various diseases, viruses and bacteria, like Salmonella for example. Many poor environmental conditions contribute to poor hygiene which ultimately helps spread this disease.
Salmonella is a genus of bacteria that even though easily prevented and treatable, is still abundant in today’s society. Man y socio-economic and environmental issues contribute to the spreading of this type of bacteria that reproduces within the intestines’ of its host, causing
disease, ill-health and possible even death.
