Ella Kulman Microbiology

define commensal

an organism that colonises the host but causes no disease

define virulence

the degree to which a given organism is pathogenic

what would gram positive bacteria look like down a microscope?

purple/blue

what would gram negative bacteria look like down the microscope?

pink/red

what type of organism would you stain with Ziehl Neelson?

mycobacteria e.g. TB

give an example of a slow growing bacteria

TB

give an example of a fast growing bacteria

E.coli and S.aureus

what types of bacteria release endotoxin?

gram negative

what types of bacteria release exotoxin?

gram positive and gram negative

what are plasmids?

circular pieces of DNA that often carry genes for antibiotic resistance

give an example of a gram negative diplococci

Neisseria e.g. N.meningitidis and N.gonorrhoeae

give an example of a gram positive cocci

staphylococcus and streptococcus

what can be done to distinguish between staphylococcus and streptococcus?

catalase test → staph=catalase +ve, strep=catalase -ve

how would you describe the arrangement of staphylococci?

clusters of cocci

how would you describe the arrangement of streptococci?

chains of cocci

what bacteria would be coagulase positive?

staphylococci aureus

what bacteria would be coagulase negative?

all others e.g. staphylococci epidermis

give examples of gram negative bacilli

shigella, salmonella, E.coli etc

give examples of gram positive bacilli

clostridium, bacillus, cornyebacterium etc

what kind of bacteria is MacConkey agar used with?

gram negative bacilli

name 2 gram negative bacilli that will give a positive result with MacConkey agar

1. E.Coli
2. Klebsiella pneumoniae

where in the body might you find staphylococci?

nose and skin

how is staph aureus spread?

aerosol and touch

how is c.diptheriae spread?

droplet spread

which type of e.coli would you associate with causing travellers diarrhoea?

enterotoxigenic e.coli (ETEC)

what are the symptoms of enteropathogenic e.coli infection?

chronic watery diarrhoea

what are the symptoms of enterohaemorrhagic e.coli?

bloody diarrhoea

what are the symptoms of shigella infection?

severe bloody diarrhoea and frequent passage

how is shigella passed on?

via contaminated food/water or from person to person

what is gastroenteritis?

frequent cause of food poisoning - 24hr incubation period

what is enteric fever?

typhoid fever - systemic disease

why is v.cholerae so dangerous?

pt is losing huge amounts of water which can result in hypovolaemic shock and severe dehydration - this can lead to death

why is v.cholerae not killed if you have a fever?

grows at 18-42°C

how would you grow haemophilus influenzae?

on chocolate agar as it requires haem and NAD

what diseases can haemophilus influenzae cause?

meningitis and pneumonia

how is N.meningitidis spread?

aerosol transmission - high risk in colonised people e.g. uni/Haj

how can you detect chlamydia?

serum antibodies or PCR - won't grow on agar

name the spirochaete that is responsible for causing syphilis

T. pallidum

why are severe fungal infections rare?

fungi are unable to grow at 37°C and are often killed by the innate and adaptive immune response

what fungal infection can often be a presenting factor for HIV?

pneumocystitis pneumonia - its an opportunistic infection that can cause lung infection in immunocompromised people

which group of streptococci can cause infective endocarditis?

alpha haemolytic streptococci

what signs and symptoms might you see in someone who has been infected with malaria?

fever, haemolysis, chills, sweats, headaches etc

give an example of a virus that causes damage by direct destruction of host cells

poliovirus or HIV

give an example of a virus that causes damage by triggering host cell 'over-reactivity' as a response to infection

hep B and C, HIV

what cells act as 'host cells' for HIV?

CD4+ cells - macrophages/dendritic cells can also be invaded by HIV

what is the effect of HIV infection on CD4 count?

HIV leads to uncontrolled CD4 activation and apoptosis - CD4 numbers decrease over time

what is a clinically important gram positive resistant bacteria?

MRSA

what antibiotic might be used in the treatment for s.pneumoniae?

amoxicillin

when might you use penicillin?

for skin/soft tissue infections, endocarditis

give an advantage of penicillin

has a narrow spectrum so there is a reduced chance of resistance

amoxicillin can be given to people infected with which bacteria?

H.influenzae, enterococci, e.coli, shigella, streptococci etc

what antibiotic would be given to someone infected with staph. aureus?

flucloxacillin

pt presents with cellulitis, what antibiotic might you give them?

flucloxacillin - s.pyogenes and staph.aureus are often a cause of cellulitis

what types of bacteria do monobactams work against?

gram negative bacilli

why would you give someone monobactams?

if they have a penicillin allergy

what types of bacteria does vancomycin work against?

gram positive only - good for MRSA treatment

pt presents with UTI, what antibiotic might you give them?

trimethoprim

what virus can cause shingles?

varicella zoster virus

name 3 resp diseases associated with HIV

-bacterial (pneumococcal) pneumonia
-TB
-pneumocystis pneumonia (PCP)

name 4 diseases that haemophilus influenzae can cause

1. meningitis
2. otitis media
3. pharyngitis
4. exacerbations of COPD

name 6 vaccine preventable diseases that are notifiable

1. diptheria
2. measles
3. mumps
4. rubella
5. tetanus
6. whooping cough

name 1 staph and 1 strep that can cause impetigo

staph aureus and strep pyogenes

give 2 examples of protozoa that can cause diarrhoea

1. cryptosporidium
2. giardia lamblia

name a bacteria that can cause ascending cholangitis

klebsiella pneumoniae

what key additional tests need to be performed in someone with MRSA?

1. echo - to rule out endocarditis
2. spinal MRI

what is the first line treatment for meningitis?

cefotaxime

what would the CSF cell count look like for viral meningitis?

-high lymphocytes
-normal/high protein
-normal glucose

what would the CSF cell count look like for bacterial meningitis?

-raised neutrophils
-high protein
-low glucose

what 3 viruses can cause encephalitis?

-herpes simplex virus
-varicella zoster virus
-HIV

what layer of the skin is affected in cellulitis?

sub-cutaneous layer

name 2 bacteria that can cause cellulitis

1. S.pyogenes
2. S.aureus

what disease is it important to rule out in someone with cellulitis?

DVT!!!!

name 4 species of the plasmodia genus that cause malaria

1. P.falciparum
2. P.ovale
3. P.vivax
4. P.malariae

what is the treatment for malaria?

chloroquine

what growth medium can be used to culture mycobacteria?

Lowenstein Jensen

what organism can cause neonatal sepsis?

group B streptococci