Bacteriology Flashcards
What shape is a Coccus/cocci bacteria
Spherical
What name is given to a coccus bacteria that divides in 1 plane to form 2 cocci?
Diplococcus
What type of bacteria is a streptococcus bacteria?
A chain coccus - Division in 1 plane produces chains
What type of bacteria is a staphylococcus?
A bunch/clump coccus - Division in 3 planes produces a clump
What shape is a Bacillus/Bacilli bacteria?
Rod-shaped - can form chains
What shape is a Fusiform bacteria?
Long, slender rods
What shape is a Vibrio bacteria?
A curved rod
What is a common example of a vibrio bacteria?
Vibrio cholerae = cholera
What shape is a spirillum bacteria?
A rigid spiral
What shape is a spirochaete bacteria?
A flexible spiral
What causes sporulation?
Stress or starvation of a prokaryote
What forms a spore?
The mother cell begins binary fission and one chromosome is sacrificed to form the spore.
Which common bacteria produces spores?
Clostridiodes difficile
How does sporulation increase the severity of infection?
It increases resistance to many antimicrobial challenges as they have no ribosomes or cell membrane to target and they are small enough to be easily spread
What are the stages of gram staining?
Stain with crystal violet
Treat with Gram’s iodine
Decolourize with acetone or ethanol
Stain with basic fuchsin or safranin
Gram + = Violet, Gram - = pink
What are the limitations of gram staining?
Not all microorganisms stain well with Gram stain e.g. Mycobacterium tuberculosis
What is an aerobic bacteria?
A bacteria that grows in oxygen
What is an obligate aerobe?
A bacteria that requires oxygen to live
What is an obligate anaerobe?
A bacteria that is killed by oxygen
What is a facultative anaerobe?
A bacteria that can tolerate aerobic and anaerobic conditions
What is a capnophilic bacteria?
A bacteria that prefers high CO2 levels
What is a microaerophilic bacteria?
A bacteria that prefers low oxygen levels
What is a selective media?
A medium that selects for the growth of one prokaryote over another
What medium is selective for Staphylococci bacteria?
Mannitol Salt Agar - 7.5% salt allows isolation of Staphylococci
How does the Salmonella-Shigella agar isolate for Salmonella and Shigella?
It contains bile salts that inhibit coliforms
What is a differential media?
Agar that contains chemicals that produces visible stains in colonies that facilitate identification
Which differential medium facilitates the identification of Enetrobacteriacae?
MacConkay Agar
Which differential medium facilitates the identification of lactose fermenters such as E. coli?
Eosin and Methylene Blue agar
What is a pathogen?
A harmful organism that produces a pathology
What is a commensal/ a mutualism/ a symbiosis?
An organism that is part of the natural flora
What is an opportunistic pathogen?
An organism that causes infection when opportunity/change in natural immunity arises
What is a contaminant?
An organism that is growing in a culture by accident
What is virulence?
The capacity of a microbe to damage the host
What are some examples of protozoan diseases?
Leishmaniasis
Malaria
Toxoplasma
Cryptosporidiosis - found in under chlorinated swimming pools
Entamoebosis
What are some examples of fungal infections?
Candida (E.g. Candida albicans = Thrush)
Aspergillus (Moulds)
What are the 2 gram negative prokaryotes we should known?
Neisseria spp
Escherichia spp
What are examples of gram positive prokaryotes we should know?
Streptococcus spp
Staphylococcus spp
Enterococcus spp
Clostridium
What are the 2 types of Neisseria prokaryotes we should know?
Neisseria meningitidis = most common cause of bacterial meningitidis
Neiseria gonorrhoeae = only cause of gonorrhoea
What is a coliform?
A species of gram negative bacilli that looks like Escherichia coli (E.coli) when on gram film and when cultured by blood agar
Under what main group do coliforms fall?
Enterobacteriaceae
What are some examples of gut commensal coliforms?
Most E.coli strains
Klebsiella spp
Enterobacter spp
Proteus spp
What are some examples of significant gut pathogens?
Salmonella spp
Shigella spp
Verotoxin producing Escherichia coli (VTEC) such as E.coli O157 and O104
What 1st line antibiotic is used for the treatment of infections caused by coliforms?
Gentamicin
What are the risks of gentamicin use?
It is highly toxic and can cause kidney damage
Why do patients with coliform sepsis become very unwell quickly?
Because when the coliform bacteria die, they release endotoxins (LPSs on gram negative bacteria)
What is sepsis?
A host response to a severe infection
What is septicaemia?
Blood poisoning caused by the movement of bacteria into the blood stream
What occurs during sepsis to cause septic shock?
Infection causes increased permeability of blood vessel walls, meaning fluid moves into tissues
This decreases blood volume and pressure, so heart rate increases
This decreases oxygen perfusion of vital organs
This leads to septic shock
How does sepsis increase risk of haemorrhage?
Increased permeability of blood vessels causes blood clotting
This uses up all clotting factors
This means there’s a higher risk of haemorrhage
How does septicaemia cause fever (symptom of sepsis)?
Antigens in the blood stream cause stimulation of macrophages
These macrophage release cytokines that move to the anterior hypothalamus
Prostaglandin E is released which increases the body’s thermal set point
This triggers a cold response
What temperature is defined as fever?
38-40 degrees celcius
What are febrile convulsions?
Fits that can occur in children due to a fever
What diseases are caused by Group A Streptococci?
Streptococcal sore throat (Scarlet fever)
Invasive diseases such as Necrotising fasciitis
Puerperal sepsis (Infection of pregnant and post-natal women)
What Group A Streptococcus is responsible for 50% of bacterial sore throats?
Streptococcus pyogenes
What is an alpha haemolytic bacteria?
A bacteria that causes oxidation of red blood cells turning it a green-brown colour
What is a beta haemolytic bacteria?
A bacteria that causes full rupture of red blood cells
Are GAS bacteria alpha or beta haemolytic?
Beta
What is pneumonia?
An acute inflammation of the lungs, usually caused by the inhalation of Streptococcus pneumoniae
It causes the plugging of alveoli and bronchioles by a fibrous exudate
What is the most important group of non-haemolytic streptococci?
Enterococci
What are 2 examples of enterococci that we should know?
Enterococcus faecalis
Enterococcus faecium
What disease is most commonly caused by enterococci?
Urinary Tract Infections
What is a VRE?
A Vancomycin Resistant Enterococci, a very resistant strain of enterococci
What are examples of Staphylococci?
Staphylococcus aureus
Staphylococcus epidermidis
Staphylococcus saprophiticus
Is Staphylococcus aureus coagulase positive or negative?
Positive = can coagulate plasma in the blood
Is Staphylococcus epidermidis coagulase positive or negative?
Negative = cannot coagulate plasma in the blood
What is MRSA?
Methicillin Resistant Staphylococcus aureus
What bacteria is the most common cause of skin, soft tissue and wound infection?
Staphylococcus aureus
What are the 3 species of Clostridioides we should know?
Clostridioides difficile - common cause of diarrhoea after taking antibiotics
Clostridioides perfringens - Causes ‘gas’ gangrene, a severe soft tissue infection following wound contamination
Clostridioides tetani - Causes tetanus, a usually fatal paralytic disease
Which class of bacteria posses endotoxins?
Gram -ve bacteria
Which class of bacteria posses exotoxins?
Gram +ve bacteria
What happens to Staphylococcus aureus on a blood agar plate?
It shows up golden on a blood agar plate
What type of inheritance causes blood related disorders and blood types?
