T1 - L1 BACTERIAL PATHOGENS Flashcards
what are features of gram + bacteria?
thick cell wall that retains the colour of gram stain (purple)
what are features of gram - bacteria?
has thinner cell wall surrounded by fatty
membrane so doesn’t not retain the gram stain (appears pink)
what does cocci refer to?
round shape
what does bacilli refer to?
rod shape
what does coccbacillus refer to?
in between a rod and sound shape
what does staph refer to?
grape shape appearance/ morphology
what does stryph refer to?
line shape appearance/ morphology
what are the three 3 factors needed for a bacteria to cause infection?
- host factors
- bacterial factors
- Opportunity
To cause infection, bacterial need a triad of host factors, bacterial factors and opportunity. What is meant by opportunity?
- exposure
- normal flora
To cause infection, bacterial need a triad of host factors, bacterial factors and opportunity. What is meant by bacterial factors?
- virulence
- resistance
- environmental survival
To cause infection, bacterial need a triad of host factors, bacterial factors and opportunity. What is meant by host factors?
- immune system [e.g. elderly and vaccination]
- devices [e.g. lines/catheters]
what is virulence?
the severity or harmfulness of an infection
NB: [Some highly virulent to all people; others are opportunistic to vulnerable people]
which bacterial is the most common cause of UTIs?
E. coli
gram - bacilli
E.coli is part of the normal flora in which part of the human body?
bowel
why are UTIs more common in women?
shorter urethra
can E.coli develop a resistance to antibiotics?
yes
which bacterial is the most common cause of skin infections?
Staphylococcus aureus
gram + cocci
where is S. aureus most commonly found on the human body?
Nasal carriage in up to 50% of people
what are the key features of s. aureus?
- able to adhere to damaged skin
- produces exoenzymes and toxins
what type of infection does S. aureus cause?
skin/soft tissue infections
what bacteria is most likely to cause surgical site infections?
Staphylococcus aureus
what bacteria causes endocarditis?
Staphylococcus aureus
what bacteria causes osteomyelitis?
Staphylococcus aureus
what infections does Staphylococcus aureus primarily cause?
- skin infections (e.g impetigo, wound infections, folliculitis)
- osteomyelitis/septic arthritis
- endocarditis
what test would detect S. aureus?
coagulase test
[Staphylococcus aureus is coagulase positive – all the other S spp are negative!]
is Staphylococcus epidermidis more less virulent than S. aureus?
less virulent and invasive
where is Staphylococcus epidermidis normally found on the human body?
normally intact with skin
is Staphylococcus epidermidis coagulase negative or positive?
coagulase negative staphylococci
which bacteria causes infection by adhering to “foreign bodies” such as catheters or prosthetics?
Staphylococcus epidermidis
what mechanism does Staphylococcus epidermidis use to adhere to prosthetic materials?
Adheres to plastics/metals using glycocalyx (‘slime’), forming biofilms
what does strepto refer to?
Strepto = “Chain” in Greek
chain like appearance
which bacteria is also referred to as “group A strep”
Streptococcus pyogenes
what is the most common cause of a bacterial sore throat?
Streptococcus pyogenes
what bacteria causes scarlet fever?
Streptococcus pyogenes
what bacteria causes necrotising fasciitis?
Streptococcus pyogenes
what bacteria causes puerperal sepsis?
Streptococcus pyogenes
what infections can Streptococcus pyogenes cause?
- puerperal sepsis
- scarlet fever
- necrotising fasciitis
what is the most common cause of bacterial pneumonia?
Streptococcus pneumoniae
what is the most common cause of bacterial meningitis in children/adults?
Streptococcus pneumoniae
except in neonates
what common childhood infection does Streptococcus pneumoniae cause?
otitis media
what bacteria is also referred to as “group B strep”?
Streptococcus agalactiae
what is the most common cause of bacterial meningitis in neonates/babies?
Streptococcus agalactiae
what is the Streptococcus milleri complex?
Three closely related species of pus-forming streptococci
- associated with abscesses
what is meant by Viridans streptococci?
Collective name for a number of species of α-haemolytic streptococci that
inhabit [normal flora in] the upper respiratory tract
what is a classic cause of sub-acute bacterial endocarditis?
Viridans streptococci / α-haemolytic streptococci
bacteraemia caused by Streptococcus gallolyticus can be associated with what condition?
colonic malignancies
what classification of bacteria is Listeria monocytogenes?
Gram positive bacillus
which bacteria is able to be transmitted to humans from animals?
Listeria monocytogenes
Classic features of Listeria monocytogenes?
- able to grow at low temperatures
- therefore associated with consuming cheese made from unpasteurised milk and other foodstuffs
what classification of bacteria is the Corynebacterium species
?
Gram positive bacilli
what is the common cause of bacterial diphtheria?
Corynebacterium diphtheria
which bacteria is associated with acne?
Propionibacterium acnes
what classification of bacteria is Propionibacterium acnes?
Gram positive bacillus
what is meant by Enterobacteriaceae (‘coliforms’)?
A collective term for a number of species of gram negative bacilli found in bowel flora
including: Escherichia coli, Klebsiella pneumoniae and
Enterobacter cloacae
what is a nosocomial infection?
hospital acquired infection
e.g. line
infections, pneumonia, wound infections
what is the most common cause of nosocomial infections?
E. coli
toxigenic strains of which bacteria can cause severe diarrhoea and haemolytic uraemic syndrome (HUS)?
E. coli
Toxigenic strains (e.g. O157)
what classification of bacteria is Pseudomonas aeruginosa?
Multi-resistant gram negative bacillus
which bacteria produces a characteristic green pigment?
Pseudomonas aeruginosa
what classification of bacteria is Neisseria meningitidis?
Gram negative diplococcus [two cocci stuck together side by side; Diplo = pair]
what infections does Neisseria meningitidis cause?
meningococcal sepsis and/or meningitis
observing whether a rash disappears under a glass is a test for what?
purpuric non-blanching rash (sepsis)
Neisseria meningitidis
what is a sign of meningococcal sepsis and/or meningitis caused by Neisseria meningitidis?
g a purpuric lesion on the skin that
does not blanch/disappear when pressed with glass
what classification of bacteria is Neisseria gonorrhoeae?
Gram negative diplococcus
what bacteria causes Ophthalmia neonatorum [conjunctivitis]?
Neisseria gonorrhoeae
what classification of bacteria is Haemophilus influenzae?
Gram negative coccobacilli
Haemophilus influenzae is part of the normal flora in which bit of the human body?
normal respiratory tract flora
what sort of infections does Haemophilus influenzae cause?
respiratory tract infections (e.g. pneumonia, infective
exacerbations of COPD)
where in the bodies normal flora will you find anaerobes?
[Many colonise the flora of the large bowel due to its anaerobic environment]
what classification of bacteria is Clostridium species?
gram positive bacilli
NB: Many are spore-forming organisms
which are the Clostridium species causes antibiotic-associated diarrhoea/colitis?
C. difficile
which are the Clostridium species causes gas gangrene?
C. perfringens
which are the Clostridium species causes tetanus?
C. tetani – cause of tetanus
which are the Clostridium species causes botulism?
C. botulinum
what bacterial species are anaerobic?
Bacteroides species
Fusobacterium species
Prevotella species
clostridium species
what is a polybacterial infection?
caused by more than one bacterium
what bacterial species are feared to as ‘Acid Fast Bacilli’ (AFBs)? why are they known as this?
Mycobacterium species
Do NOT stain using conventional gram staining
[stained by acid fast stain]
list bacteria without a conventional cell wall.
[DO NOT stain with the gram stain]
Chlamydia species e.g. C. trachomatis – commonest cause of STI
Mycoplasma species e.g. M. pneumoniae – common cause of respiratory tract infections
what does Leptospira cause? (spiral bacteria)
Leptospirosis
what does Borrelia cause? (spiral bacteria)
Lyme Disease through tick bite
what does Treponema pallidum cause? (spiral bacteria)
syphilis
what classification of bacteria is Staphylococcus aureus?
gram + cocci
what classification of bacteria is Streptococcus pyogenes?
gram + cocci
what classification of bacteria is Streptococcus agalactiae?
gram + cocci
what classification of bacteria is neisseria meningitides?
gram - cocci
what classification of bacteria is neisseria gonorrhoeae?
gram - cocci
what classification of bacteria is bacillus anthracis?
gram + bacilli
what classification of bacteria is clostridium difficile?
gram + bacilli
what classification of bacteria is listeria monocytogenes?
gram + bacilli
what classification of bacteria is corynebacterium diphtheriae?
gram + bacilli
what classification of bacteria is salmonella typhi?
gram - bacilli
what classification of bacteria is shigella spp?
gram - bacilli
what classification of bacteria is escherichia coli?
gram - bacilli
what classification of bacteria is proteus spp?
gram - bacilli
what classification of bacteria is Yersinia pestis?
gram - bacilli
what classification of bacteria is haemophilus?
gram - coccobacilli
what classification of bacteria is bordetella?
gram - coccobacilli
what classification of bacteria is brucella?
gram - coccobacilli
what classification of bacteria is pasteurella?
gram - coccobacilli
what classification of bacteria is helicobacter?
spiral bacteria
what classification of bacteria is campylobacter?
spiral bacteria
what classification of bacteria is borrielia?
spiral bacteria
what classification of bacteria is leptospira?
spiral bacteria
what classification of bacteria is treponema pallidum?
spiral bacteria
