Microbes and Normal Flora Flashcards
What are the classes of microbial organisms?
Viruses
Bacteria
Fungi
Protozoa
Viruses
RNA or DNA
No independent metabolism- can only exist in other cells
No organelles
Simple protein coat (cell membrane from host cell)
Eg: Influenza Rhinovirus Herpes simplex Ebola/Lassa HIV
Bacteria
DNA as a single chromosome
Independent metabolism
No organelles
Cell wall
Pepticoglycan cell wall= gram stain -ve
Lipopolysaccharide cell wall= gram stain +ve
Fungi
DNA as multiple chromosomes
Independent metabolism and organelles
Cell wall
E.g Candida (candidiasis- thrush)
Protozoa
DNA as multiple chromosomes
Independent metabolism
Organelles
Cell membrane
E.g. Giardia
What do positive and negative gram stains indicate?
+ve: peptidoglycan cell wall
-ve: lipopolysaccharide cell wall
What are the classes of bacteria?
Classified on gram staining and shape:
Gram stain +ve or -ve
Coccus (round) or bacillus (rod/elongated shape)
Example of a gram positive cocci
Staphylococcus aureus and streptococcus species
Example of gram negative cocci
Haemophilus influenzae
Example of gram positive bacilli
Bacillus anthracis and lactobacilli species
Example of gram negative bacilli
Salmonella, Escherichia coli (E Coli)
Define symbiotic relationships
Close, long term interaction between 2 different species
Can be mutualistic, commensal or parasitic
Define mutualistic interactions
Both parties benefit
Define commensal interactions
One party benefits, no harm to the other party
E.g. colonisation
Normal gut flora
Define parasitic interactions
One party benefits, the other is harmed.
Define infection
Invasion and multiplication of microbes in an area of the body where they are not normally present. May cause symptoms or not. Does not necessarily cause disease.
Define pathogen
Micro organism able to cause disease
Define obligate pathogen
Pathogen that must cause disease in order to be transmitted from one host to another. Must infect host in order to survive.
Define opportunistic pathogen
A pathogen that takes advantage of an opportunity not normally present, such as a host with a weak immune system (i.e. breached integumentary barrier, disrupted gut flora)
What effects can antibiotics have on normal microbiota?
Can kill normal flora, allowing opportunity for pathological bacteria to invade (e.g. clostridium difficile)
