Microbiology Flashcards
boil with pus on child’s forehead
purple cocci in clusters
S. aureus
20yo student fever headache
CSF sample
pink diplococci
N. meningitidis
Blood culture from febrile 62yo woman with pain and burning on passing urine
gram negative rods
E.coli
CSF sample from neonate febrile and irritable
purple rods
Listeria
57yo woman went to dentist 2 months ago night sweats and malaise chains of purple cocci green halo on culture grows around optochin
strep viridans
What do the organisms usually cause depending on their Lancefield group?
A, C, G- tonsillitis, skin infections
B- neonatal sepsis and meningitis
D- UTIs
what is the purpose of the optochin disc?
to differentiate between alpha haemolytic strep
what is the purpose of the Lancefield test?
to differentiate between beta-haemolytic strep by detecting surface antigens
What are the sterile sites in the body?
lungs- pleural fluid blood CSF peritoneal cavity Lower resp tract urinary tract joints
Where are commensal bacteria found in the body?
skin mouth vagina large intestine urethra
Which bacteria can cause bloody diarrhoea?
Shigella dysenteriae E. coli Campylobacter jejuni Yersinia spp Salmonella spp
Which viruses can cause bloody diarrhoea?
rotavirus
norovirus
adenovirus
Which protozoa can cause bloody diarrhoea?
Entamoeba histolytica
giardia lamblia
Which agar can be used to isolate identify salmonella and shigella?
XLD and MacConkey (non-lactose fermenting)
How do you distinguish between salmonella and shigella?
oxidase test
positive = salmonella
negative = shigella
Which viruses would you test for when doing a respiratory PCR?
influenza A/B parainfluenza 1-4 respiratory syncytial virus rhinovirus adenoavirus coronavirus
What 3 different markers are searched in an HIV blood test?
viral RNA
COBAS antigen
COBAS antibody
Which viruses cause viral meningitis?
enterovirus
herpes simplex
varicella zoster
adenovirus
When is retesting for HIV indicated?
clinical suspicion of seroconversion illness
high risk exposure in last 3 months
22yo woman 24hr hx of severe pleuritic chest pain, breathlessness, productive rusty sputum, very unwell.
blood and sputum culture show Strep pneumoniae
what is the final diagnosis and which antibiotic is first line for this organism?
invasive pneumococcal pneumonia
amoxicillin
List the atypical pathogens that can cause community acquired pneumonia.
chlamydophila psittaci
mycoplasma pneumoniae
coxiella burnetti
legionella pneumophila
Which antibiotics would you use against atypical pathogens causing community acquired pneumonia?
macrolides (clarithromycin, erythromycin)
fluoroquinolones (ciprofloxacin, levofloxacin)
tetracycline (doxycycline)
amoxicillin does not work
clarithromycin is first line for legionella
Which bacterium grows on chocolate agar but not blood?
H. influenzae
What antibiotics should be used to treat a H. influenzae infection?
amoxicillin, doxycycline
What is the first line antimicrobial used to treat a pneumocystis jirovecii infection?
co-trimoxazole
with prednisolone if significant type 1 failure
Which antibiotics would you use to treat an exacerbation of bronchiectasis caused by P. aeruginosa?
antipseudomonal beta lactam like ceftazidime
fluoroquinolone like ciprofloxacin
What marks would you expect to see on the nails of a patient with infective endocarditis?
splinter haemorrhages
What is the standard antibiotic treatment for endocarditis caused by Strep viridans and for how long?
benzyl penicillin high dose for 6 weeks
synergistic gentamicin
What is the standard antibiotic against staph aureus?
flucloxacillin (beta lactam penicillin)
Which medium is specific to campylobacter?
charcoal cefazolin sodium decarboxylate agar
List diarrhoea-causing pathogens that can be detected with stool microscopy.
cryptosporidium parvum
entamoeba histolytica
giardia lamblia
schistosoma mansoni
Which bacterium is responsible for antibiotic-associated diarrhoea?
Clostridium difficile
Which antibiotics would you use to treat a clostridium infection?
metronidazole (because it is anaerobic)
oral vancomycin
What empirical antibiotics would you start a patient on who is suspected to have an enteric bacterial infection?
cefuroxime/co-amoxiclav and metronidazole
A 48yo woman unwell with fever, jaundice, severe RUQ pain and tenderness. Blood test reveals neutrophil leucocytosis with raised alkaline phosphatase and bilirubin. US of abdomen shows thick walled gall bladder with gall stones and dilated common bile duct.
What is the probably surgical diagnosis and which empirical antibiotic would be appropriate?
acute cholecystitis
co-amoxiclav
What additional tests would you perform in someone with (MRSA) bacteraemia?
echocardiogram to check for IE
MRI spine to check for discitis
Which antibiotics would you use to treat UTI caused by amoxicillin-resistant E.coli/klebsiella?
trimethoprim
nitrofurantoin or co-amoxiclav
Which bacteria are likely to cause meningitis in neonates?
E.coli
Group B strep
listeria monocytogenes
Which bacteria are likely to cause meningitis in infants?
N. meningitidis
H. influenzae
S. pneumoniae
Which bacteria are likely to cause meningitis in young adults?
N. meningitidis
S. pneumoniae
Which bacteria are likely to cause meningitis in the elderly?
S. pneumoniae
N. meningitidis
Listeria
What are the viral causes of meningitis?
mumps virus echo virus coxsackie virus other enteroviruses herpes simplex virus lymphocytic chorio meningitis virus poliovirus
How would you manage a patient with meningitis caused by strep pneumoniae?
IV cefotaxime IV dexamethasone (pneumococcal infections cause a lot of inflammation which can increase the risk of long term sequelae like deafness)
What groups are at risk of meningitis due to Listeria monocytogenes?
immunocompromised alcohol dependency diabetes pregnancy HIV long-term steroids children elderly
Why should a lumbar puncture not be performed in someone with suspected meningitis back rash?
No. The presence of a characteristic rash and the presentation raises a strong clinical suspicion of meningococcal septicaemia and meningitis. There is no need to do a lumbar puncture and may be harmful in the event of coagulation abnormalities secondary to the meningococcal sepsis. The diagnosis can often be confirmed by either peripheral blood culture or peripheral blood molecular testing for N.meningitis (ie. PCR).
bacteria can get into sterile CSF
What actions (other than treating the pt) need to be taken when someone has confirmed meningitis?
notify public health England
prophylaxis in close contacts- single dose ciprofloxacin/rifampicin
vaccinate others
In a drowsy and confused elderly patient with suspected meningitis, what therapy should be started whilst awaiting lab results?
IV antibiotics for possible bacterial meningitis
IV acyclovir to treat possible herpes simplex virus
