Campylobacter A Spiral Motile Gram Negative Microaerophilic Bacterium Biology Essay


Campylobacter is a spiral, motile, gram negative, microaerophilic bacterium meaning it only requires low levels of oxygen. It is generally 0.3µm thick and 0.5-5µm in thickness and may be flagellated on either one end or both ends of the cell (Kayser, 2005). Campylobacter jejuni is the species at the forefront of this particular genus in terms of food borne pathogens, being recognized as the most important cause of enteritis in humans after Escherichia coli, in the industrialized world (Gallardo F, 1998).

C.jejuni is most commonly found in foods such as meat, poultry and raw milk. A study on raw milk in the United States of America reported that 12% of milk from dairy farms in eastern Tennessee was contaminated with C.jejuni most likely a result of bovine feces. Another study showed retail chicken as having an isolation rate of 98%. The highest levels of contamination are said to be found in skin and giblets with counts often in excess of 103/100g (Altekruse, 1999).

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Infection by C.jejuni can be caused by: drinking untreated water, drinking raw milk, eating undercooked meats or handling of undercooked meat and poultry. The transfer of the bacterium from human to human is relatively uncommon. It has been found in the USA that there is a notable rate of infection amongst young adults with 8 in every 100,000 infections whereas the rate amongst adults being less than 3 per 100,000 (Altekruse, 1999).

Once C.jejuni enters the system, it produces an enterotoxin in a similar way to which E.coli does as well as the formation of cytotoxins. This leads to a form of enterocolitis that has watery, sometimes bloody stools which are accompanied by high fever. The symptoms present after an incubation period of 2 to 5 days and last approximately 1 week. Other forms of Campylobacter run a systemic course before presiding near the heart (myocarditis) and spinal cord (meningitis) (Kayser, 2005).

Campylobacter can be found in excessive numbers in individual stools of infected persons and grown on blood agar plates at the optimum temperature of 42oC under microaerophilic conditions for 48 hours. Then the identification process is performed based on the cells requirements to grow as well as a catalase and oxidase test (Kayser, 2005).

In terms of treatment, the most important facet is replacement of fluids and electrolytes that is lost through severe diarrhea. However, antibiotics may be required for treatment of invasive cases as complications may subsequently result in a condition known as Guillian-Barre syndrome (WHO, 2010a). Preventative measures are the best method to reduce Campylobacter infections. This includes safe hygiene practices, avoidance of undercooked meats and poultry and ensuring that no cross contamination occur between preparation and storage foods (Phillips, 1995).

Escherichia coli are a lactose fermenting, gram negative, rod shaped, motile organism commonly found in human gastrointestinal (GI) tracts. Their antigenic characteristics are based on the O, K and H antigens. Almost always, it is considered part of the normal microflora as the bacteria inhabit the tract within hours after birth and inhabit the human bowel within 40 hours. This is usually a result of contact with the bacterium that may be consumed through food or water, or handling of a child (Todar, 2008).

The E.coli strain most commonly associated with foodborne illness is the enterohemorrhagic E.coli (EHEC). This type of bacteria causes hemorrhagic colitis as well as hemolytic-uremic syndrome (HUS) which occurs in 5% of all infections. This sort of bacterium attaches itself to enterocytes using fimbriae and produce shigalike toxins. The serovar most frequently involved in HUS is O157:H7 which is the biggest public health concern (Kayser, 2005).

This pathogen is mainly contracted from the ingestion of contaminated foods including: raw ground meats and raw milk. Water may also be contaminated from infected animal feces as well as cross contamination while food is prepared. Recently, the largest outbreaks have been a result of contamination amongst fruits and vegetables that have been contaminated with feces from domestic or wild animals during the handling process. Then, the transmission from human to human has been via the fecal oral route (WHO, 2010b).

As E.coli is usually a commensal, they can be pathogenic in immunosuppressed hosts. So, once these E.coli become pathogenic, they insert themselves within intestinal mucosa, they begin to reproduce and cause symptoms of abdominal cramping and diarrhea most commonly. In accompaniment with these, fever and vomiting can also occur. The incubation period is generally three to eight days and symptoms begin to subside within 10 days. Fatalities associated with enterohemorrhagic E.coli patients are often a result of HUS and range from 3-5% of people (Nataro and Kaper, 1998)

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An agar medium known as sorbitol-MacConkey agar is used in the isolation of enterohemorrhagic E.coli. This contains 1% sorbitol in place of lactose in the standard MacConkey medium. Colourless colonies indicate growth of enterhemorrhagic bacteria (Nataro and Kaper, 1998)

Treatment requires antibiotics with severe types and replacement of fluids and electrolytes that are lost during diarrhea. An opioid drug known as Loperamide may be used to slow down intestinal activity. Prevention is a hygiene issue, as well as avoidance of contaminated food and water. Also, it is important to not completely reduce the count of normal microbiota within the gastrointestinal tract (Kayser, 2005).

Salmonella is a gram negative, facultative, rod shaped bacteria that is often 1µm in width and 2µm in length. They are oxidase negative, motile and are glucose fermenters producing acid and gas. The serotypes of Salmonella are based on the O antigen structures, the H antigen that refers to flagellum and the Vi antigen that refers to the capsule (Ellermeier, 2006).

The Salmonella bacterium is transferred from animals to humans through the ingestion of contaminated foods that have animalian origin. Most commonly, the bacterium is found in meat, poultry, milk and eggs. Vegetables are also involved when they are grown in contaminated manure (WHO, 2010c). In the US alone, there is an estimated count of 1.9 x 106 infections worldwide with an increasing rate in the developed world (Ashkenazi, 1988).

Infection progresses when Salmonella attaches to the enterocytes of the ileum and colon then, using the invasin proteins on its surface, penetrates the mucosal lining. The illness develops presenting with diarrhea and vomiting; sometimes accompanied by high fever. These symptoms tend to last a few days without any particular therapy (Kayser, 2005).

To detect Salmonella in stool samples, a non-selective medium such as blood agar can be used. As well as that, MacConkey agar, that is selective and differential media, can also be used to identify the lactose fermenting, gram negative bacterium. Also, a highly selective medium like bismuth sulphite agar may also be used (Ellermeier, 2006).

In order to treat Salmonella infections, the most important treatment is to replace fluids and electrolytes that are lost from vomiting and diarrhea. Also, antibiotics may be used such as: 4-quinolones which is a broad-spectrum antibiotic, or aminopenicillins. The only possible prevention is to avoid exposure to the bacterium. This means drinking clean water, avoiding uncooked food in countries where Salmonella occur. As well as this, it is important to report the cases to health authorities (Kayser, 2005).