Question

1. can mrsa and clostridium dificile be part of someones “normal flora” ? explain.

2 lactobacillus and candida albicans are vaginal normal flora. describe their relationship.

3. under what circumstances van commensal bacteria cause infections?

Answer 1

1. Staph bacteria are normally found on the skin or in the nose of about one-third of the population. The bacteria are generally harmless unless they enter the body through a cut or other wound, and even then they cause only minor skin problems in healthy people. MRSA is an infection caused by Staphylococcus bacteria. MRSA is very contagious and can be spread through direct contact with a person who has the infection

C. difficile bacteria are present in intestines but never become sick, though rarely may still spread the infection. Signs and symptoms usually develop within five to 10 days after starting a course of antibiotics, but may occur as soon as the first day or up to two months Spores from C. difficile bacteria are passed in feces and spread to food, surfaces and objects when people who are infected don't wash their hands thoroughly. The touch a surface contaminated with C. difficile spores and then unknowingly swallows the bacteria.

2. In humans Lactobacillus is present in the digestive system, urinary system and genital system. In women Lactobacillus species are normally a major part of the vaginal microbiota. Lactobacillus forms biofilms in the vaginal and gut microbiota, allowing them to persist during harsh environmental conditions .Lactobacillus exhibits a mutualistic relationship with the human body, as it protects the host against potential invasions by pathogens, and in turn, the host provides a source of nutrients.

Candida albicans is an opportunistic pathogenic of yeast and is a common member of the human gut flora. It can also survive outside the human body. It is detected in the gastrointestinal tract and mouth in 40–60% of healthy adults. It is usually a commensal organism, but it can become pathogenic in immunocompromised individuals. It causes the human infection candidiasis, which results from an overgrowth of the fungus.

Lactobacillus bacteria were able to protect human oral mucosa cells against damage caused by C. albicans infections. They offered effective protection against the fungus, and inflammatory reactions without treatment. Lactobacillus bacteria were unable to directly inhibit the growth of the Candida cells.

The Lactobacillus bacteria and C. albicans appear to compete for glucose. The bacteria thus deprive the fungus of the food it needs to form the hyphae that are crucial for its virulence. The bacteria occupy the docking sites that the fungus needs in order to attach to cells.The reduced ability to attach to and enter mucosal cells also effect the albicans survival.

3. Commensals, such as E.Coli can become pathogenic when they escape their original niche and start to colonize deeper tissues. These results show that under constant pressures from component of the host immune system such as macrophage phagocytosis, commensal rapidly acquires pathoadaptive mutations that cause transcriptome changes associated to the host-microbe It may results in phenotypic changes, increased intracellular survival, through the delay of phagosome maturation and increased ability to escape macrophages.