Gram Positive Bacteria Flashcards
What are bacteria?
Single celled prokaryotes
How do most bacteria reproduce?
through binary fission
What do gram positive bacteria have which makes up a large portion of their cell wall?
Peptidoglycan
What do gram negative bacteria have which makes up a large portion of their cell wall?
Lipopolysaccharides (lipid A is what makes the bacteria very toxic and causes the harmful disease) and outer membrane proteins
What method can be used to distinguish between types of bacteria which are causing the infection?
Gram stain
What are gram positive cocci which are present in clusters called?
Staphylococci
What are gram positive cocci which are present in chains called?
Streptococci (enteroccci)
What test is used to check for staphylococci?
Coagulase test
What does it mean when coagulase test is positive for staphylococci?
If positive, then staphylococcus aureus is present which can be MSSA or MRSA
Where is staphylococci carried?
Carried in nose, axilla perineum (groin area), hairline
What disease are associated with staphylococci?
Wide range of diseases from: boils, soft tissue infections, septicaemia, cellulitis, skin abscesses, pneumonia, toxic shock syndrome and food poisoning (dangerous and non-dangerous)
Why is staphylococcus aureus penicillin resistant?
It contains Beta- lactamase
Why is MRSA causing problems for infection control? (3)
- They are methicillin resistant (staphylococci aureus)
- can mutate quickly
- resistant to penicillin (common antibiotics)
What strain is associated with coagulase +ve test for staphylococcus?
Staphylococcus aureus
What 3 strains are associated with streptococci?
- alpha haemolysis (partial)
- beta haemolysis (complete)
- non- haemolytic
What colour does blood agar turn in alpha (partial) haemolysis?
turns green
What colour does blood agar turn in beta (complete) haemolysis?
turns clear
What effect does the non-haemolytic strain have on blood agar? (group D streptococci)
No effect
What two strains does alpha-haemolytic streptococci include?
- streptococcus pneumoniae
- viridans streptococcus
What does viridans streptococci cause?
endocarditis (infection and inflammation of the lining of the heart, especially the heart valves)
What do streptococcus pyogenes cause? (Group A, Beta haemolytic)
-throat infections (sore throat)
-skin infections (e.g. cellulitis or necrotising fasciitis)
-scarlet fever
- acute rheumatic fever
-acute glomerulonephritis
Treated with penicillin
What does Streptococcus Agalactiae cause? (Group B, Beta haemolytic)
- neonatal sepsis including meningitis and bacteraemia (usually spread from mother to baby through amniotic fluid)
- most people develop natural immunity to it because of constant exposure
What is another name for bacteria in Group A strep for Beta haemolytic bacteria?
Streptococcus pyogenes
What is another name for bacteria in Group B strep for Beta haemolytic bacteria?
Streptococcus agalactiae
Where is Group D enterococcus faecalis found? (non-haemolytic)
Found in the gut as a normal commensal
What does Group D enterococcus faecalis cause?
non-haemolytic
- Gut commensal.
- Can cause UTI.
- VRE an increasing problem in some hospitals (vancomycin resistant enterococci)
What does Clostridium Difficile cause?
- pseudomembranous colitis (inflammation of the colon)
- DIARRHOEA (because of toxin production)
- nausea
- abdominal cramps
- pyrexia (high temp)
- anorexia (loss of appetite)
What increases a person’s chances of getting clostridium difficile?
Taking large amounts of antibiotics
Where does clostridium perfringens cause ?
- present in soil and normal commensal (flora) in normal human and animal gut/ faeces
- toxigenic strains cause food poisoning
- Main cause of “gas gangrene”
- Serious infection treated with penicillin and/or metrondiazole.
What does clostridium perfringens contaminate/infect?
- food (enterotoxin producing strains lead to food poisoning)
- serious wounds which causes gas gangrene
What do toxins from clostridium tetani cause?
- Cause of tetanus due to toxin acting on CNS.
- Toxoid used for immunisation.
Why is tetanus caused? (linked to NMJ)
Loss of inhibition at neuromuscular junction which causes uncontrollable muscle spasms
What are the 4 main anaerobic bacilli? (clostridiums)
- clostridium difficile
- clostridium tetani
- clostridium perfringens
- clostridium botulinum
What are the 2 aerobic small bacilli groups? And what do each cause?
- corynebacterium (diphtheria)
2. listeria monocytogenes (meningitis)
What are the 2 aerobic large bacilli groups? And what do they cause?
- bacillus cereus (food poisoning)
- bacillus anthracis (anthrax)
What does Staphylococcus aureus cause?
- Normal flora in nose and skin.
- Major pathogen in skin, endocarditis, cellulitis, abscesses, osteomyelitis, toxin mediated food poisoning and toxic shock syndrome. Affect skin and soft tissue
What are the main symptoms of streptococcus pyogenes? (strep throat)
- red and swollen tonsils
- throat pain (pain swallowing)
- swollen/tender lymph nodes in the neck
- fever, rash, vomiting
What are the main symptoms of streptococcus pneumoniae?
- fever (pyrexia) and headache
- cough
- shortness of breath
- chest pain
- stiff neck
- disorientation and confusion
- chills
- ear pain
what are the main symptoms of clostridium difficile? (affects bowel; colitis)
- watery diarrhoea (10-15 times a day)
- abdominal cramps and pain
- tachycardia (fast heart rate)
- fever
- blood and pus in stool
- dehydration
- anorexia (loss of appetite)
What are the 3 main staphylococci?
- staphylococcus aureus
- staphylococcus epidermis
- staphylococcus saprophyticus
What does a positive coagulase test indicate?
Staphylococcus aureus
What two bacteria are associated with negative coagulase test?
- staphylococcus epidermis
2. staphylococcus saprophyticus
What does Staphylococcus epidermis cause?
Found everywhere on skin. May cause infection of catheters, prostheses and ventriculo-peritoneal shunts.
What does Staphylococcus saprophyticus cause?
Cause of UTI in women of child bearing age.
What does streptococcus pneumoniae cause?
- Normal flora in upper resp. tract.
- Commonest cause of bacterial lobar pneumonia. Major cause of meningitis in children and elderly. Vaccine available
What does viridians streptococcus cause?
- Normal resident in mouth.
- Common cause of endocarditis, following dental treatment
What is the spore forming, aerobic bacillus bacteria?
Bacillus Species
What two groups are aerobic, spore-forming, bacillus species split into and what do they cause?
- bacillus cereus (food poisoning)
2. bacillus anthracis (anthrax)
What are the 2 aerobic, non-spore forming bacilli?
- listeria monocytogenes
2. corynebacterium diphtheriae
What does listeria monocytogenes cause? (aerobic non-spore forming bacilli)
- Found in animal and vegetable products (may be ingested).
- Cause menegitis in neonates and the elderly and bacteraemia in pregnancy
What does corynebacterium diphtheriae cause?
Causes diphtheria and skin commensals
What are the 4 anaerobic spore forming bacilli?
“Please don’t take brainscape”
- clostridium difficile
- clostridium perfringens
- clostridium tetani
- clostridium botulinum
What does clostridium botulinum cause?
- Cause of botulism following ingestion of contaiminated food.
- Produces most potent neurotoxin. Rare in UK.
