CP1 Bacterial Pathogens Flashcards
What colour do gram + bacteria stain?
Black/purple
What causes gram + bacteria to appear black/purple after staining?
The waxy mycolic acid coat is not dissolved by acetone or ethanol in the staining process causing the bacteria to retain its purple colour (and can appear black after further staining)
What is the role of the waxy mycolic acid coat on gram + bacteria?
To prevent the bacteria drying out
What colour do gram - bacteria turn after staining?
Pink/red
What causes gram - bacteria to look pink/red after staining?
The cell wall and fatty layer are decolourised by acetone/ethanol in the staining process thus becoming transparent allowing the pink stain to take.
What medical condition can arise from gram - bacteria and why?
Gram negative septic shock
Because the fatty layer around the cell wall can release endotoxins (lipopolysaccharides) into the blood stream
Where in the body is staphylococcus aureus found in 30-50% of individuals?
Nose
What are 4 infections caused by staphylococcus aureus?
- Skin and soft tissue damage
- Bacteraemia and septicaemia
- Bone/joint infections e.g. osteomyelitis
- Endocarditis
How does S. aureus cause skin/soft tissue infections.
The bacteria adheres to damaged skin and produces exoenzymes and toxins which provoke the immune response
What type of bacteria is staphylococcus epidermis?
A coagulase negative staphylococci
What environment in the body are coagulase negative staphylococci normally found? (Healthy to be there)
Skin
What type of pathogen is straphylococcus epidermis?
Opportunistic pathogen
What is the aetiology of coagulase negative staphylococci bacteria?
Adhere to metal or plastic ‘foreign bodies’ (e.g. intravascular catheters, prosthetic joints and cardiac valves).
What allows staphylococcus epidermis (and other coagulase negative staphylococci) to adhere to metal and plastic?
These bacteria have a slime layer called glycocalyx which forms biofilms on plastics and metals.
What is streptococcus pyogenes better known as?
Strep A
What environment are strep A bacteria usually found in?
Pharynx
What 5 infections are caused by primary strep A infection?
- Scarlet fever
- Sore throat
- Necrotising fasciitis
- Puerperal sepsis
- Skin and soft tissue damage
What antibiotic can be used to treat strep A?
Penicillin
What is an example of a secondary presentation caused by strep A?
Glomerulonephritis
What environment are streptococcus pneumoniae usually found in?
Pharynx
What are the 2 main infections caused by streptococcus pneumoniae?
Pneumonia and meningitis
What is the most common cause of bacterial meningitis for most age groups (not neonates)?
Streptococcus pneumoniae
What is the most common cause of bacterial meningitis in neonates?
Streptococcus agalacitiae aka strep B
Where are escherichia coli (E.coli) found in the body?
Colon
What 6 infections can be caused by E.coli?
- UTIs
- Intra- abdominal infections
- Sepsis
- Haemolytic uraemic syndrome (usually caused by O157 strain)
- Bacteroeamia
- hospital acquired/nosocomial infections
What is the aetiology of E.coli caused UTIs?
E.coli colonises urethral meatus and surrounding tissue and adheres to the uroepithelial cells. This them triggers a host inflammatory response.
Name 2 coliform bacteria that cause similar infections to E.coli?
Klebsiella pneumoniae and enterobacter cloacae
Where are pseudomonas aeruginosa bacteria usually found?
In water
What 4 infections are often caused by pseudomonas aeruginosa?
- Ventilator associated pneumonia
- Bacteraemia
- UTIs
- Soft tissue infections
What type of pathogen is pseudomonas aeruginosa bacteria?
Opportunistic pathogen
What is characteristic of a pseudomonas aeruginosa infection on the skin?
A green pigment
What environment are neisseria meningitidis bacteria found?
Pharynx
What 2 infections are caused by neisseria meningitidis?
Meningococcal sepsis and bacterial meningitis
Why is there a reduction in sepsis and meningitis caused by neisseria meningitidis?
Vaccination
What 3 common bacterias that cause infection have no colonisation patterns?
Neisseria gonorrhoeae
Chlamydia difficile
Mycobacterium tuberculosis
What 2 infections are caused by neisseria gonorrhoeae?
- Gonorrhoea
- Ophthalmia neonatorum (occurs when infected mother has vaginal birth passing infection to baby’s eyes)
What secondary infection can occur after primary neisseria gonorrhoeae infection?
Invasive infections e.g. septic arthritis
What infection is caused by chlamydia trachomatis?
Chlamydia
What is the most common STI?
Chlamydia
What is another name for mycobacterium?
Acid Fast Bacilli (AFBs)
Why are mycobacterium called AFBs?
As they do not stain using conventional gram staining
What is a common infection causing mycobacterium?
Mycobacterium tuberculosis
What infection is caused by mycobacterium tuberculosis?
Tuberculosis (both pulmonary and extra pulmonary)
Who is most vulnerable to infection from atypical mycobacterium?
Immune compromised patients and those with chronic lung disease e.g. COPD
What 3 infections are caused by haemophilus influenzae?
- Respiratory tract infections
- Capsulated meningitis
- Capsulated epiglottitis
What has caused a reduced rate of capsulated haemophilus influenzae meningitis and epiglottitis?
Vaccination
What environment is haemophilus influenzae most commonly found?
Pharynx
What environment is clostridium difficile usually found in?
Colon
What is the most common infection caused by clostridium difficile?
Pseudomembranous colitis
What has caused a reduction in clostridium difficile infections?
Infection prevention interventions
What term describes the three species of pus-forming streptococci?
Streptococcus milleri complex
What infection does the streptococcus milleri group/complex cause?
Abscesses - commonly in lungs, liver, brain and mouth
What bacteria causes diphtheria?
Corynebacterium diptheriae
Why is diptheria uncommon in UK now?
Vaccination
Bacteraemia with which bacteria can cause colonic malignancies?
Streptococcus gallolyticus
What bacteria causes sub-acute bacterial endocarditis?
Viridans streptococci
What is another name for propionibacterium acnes?
Cutibacterium acnes
What 3 infections are associated with cutibacterium acnes?
- Acne
- Device associated infections
- Post procedural infections
What type of bacteria is cutibacterium acnes?
Gram +
What is the collective name for some gram - bacteria species found in normal bowel flora?
The enterobacteriae aka coliforms
What three factors are involved in bacterial infection?
- Host factors
- Bacterial factors
- Opportunity
What three infections are caused by spirochaetes bacteria?
- syphilis
- Leptospirosis
- Lyme disease
What spirochaetes causes syphilis?
Treponema pallidum
Give four examples of bacteria types that are anaerobes?
- Most clostridium bacteria (e.g. clostridium difficle, clostridium perfingens, clostridium tetani and clostridium botulinum)
- Bacteroids
- Fusobacterium
- Prevotella
What infection is associated with clostridium perfingens?
Gas gangrene
What infection is associated with clostridium tetani?
Tetanus
What infection is caused by clostridium botulinum?
Botulism
