Microbiology Flashcards
describe the appearance of listeria monocytogens
β-haemolytic anaerobic Gram-positive rod/ bacillus
common cause of travellers diarrhoea
e. coli
casues of non-bloody diarrhoea
giardia
vibrio cholera
bacillus cereus
pt develops sudden diarrhoea and non bloody diarrhoea after eating re-heated rice
Bacillus cereus
pear-shaped trophozite containing two nuclei, four flagellae and a suction disc is…
Giardia lamblia
anaemia, thrombocytopenia and renal failure
haemolytic uraemic syndrome casued by 0157:H7 toxin from E. coli
Examples of live attenuated vaccination
live pathogen but made less pathogenic (is grown in non human tissue)
(MMR-VBOY)
MMR
VZV
BCG
oral- polio, typhoid
yellow fever
examples of inactivated vaccines
quadravalent influenze
polio
cholera
bubonic plague
hepA
Rabies
Pertussis
examples of conjugate vaccines
(NHS-T)
N meningitidis
H influenzae
Strep pneumonia
Tetanus
examples of DNA/RNA vaccines
Sars-CoV-2 (mRNA)
adenovirus
examples of adjuvents
alum (most common)
CpG
complete freunds adjuvent
mechanism of alum as an adjuvent
antigens absorbed into alum as a means of slowly releasing the antigen
activates Gr1+ cells produce IL4 –> primes naiive B cells
mechanism of CpG as an adjuvent
activates TLR on APCs
causes of bloody diarrhoea
shigella
campylobacter jejuni
E.coli
entamoeba hystolytica
salmonella
yersinia
comma shaped bacteria
vibrio cholera
what is the difference in pattern of paralysis between GBS and clostridium botulinum
GBS- ascending paralysis
C. botulinum- descenting paralysis
Rose spots are pathopneumonic for what infection
Salmonella typhi
flask shaped ulcer is caused by what infection?
Entamoeba hystolytica
CSF analysis shows very high protein, low glucose and high lymphocytes is likely to be…
mycobacterium tuberculosis meningitis
what kind of media is best for culturing neisseria meningitidis
grown best on Thayer–Martin VCN media as only allows n. meningitidis to grow
what is the causative organism of lyme disease
borrelia burgdorferi
Gram-negative coccobacillus that causes a painful ulcer
Haemophilus ducreyi
differential diagnosis for genital ulcer
PAINFUL:
Herpes simplex
haemophilis ducreyi
PAINLESS:
primary syphilis
lymphogranuloma venerum
what STI can be cultured on chocolate agar?
haemophilus ducreyi
drug of choice in cases of methicillin-resistant Staphylococcus aureus infections (MRSA)
vancomycin
side effects of chloramphenicol
aplastic anaaemia
complications of human herpes virus 8
Kaposi’s sarcoma
multicentric castleman disease
primary effusion lymphoma
antiviral used in the treatment of influenza
oseltamivir
causative organisms of encephalitis
HSV1, west nile virus, flavivirus
listeria monocytogens encephalitis (worse than listeria meningitis)
Amoebic: naegleria fowleri, habitat, acanthoemeba
toxoplasma gondii (cats)
bacterial causative organisms of meningitis
direct bacterial toxicity or indirect inflammatory reponse
N. meningitidis , strep pneumoniae, H influenzae
neonate and elderly: GBS, listeria, E.coli
Chronic: TB
causative organisms of
causative organisms of
common viral casues of meningitis
enteroviruses (coxsackie, echovirus), mumps, HSV2, measles, VZV
(usually asceptic meningitis)
brain abscess pathology
otitis media/mastoiditis/paranasal sinuses
endocarditis/haematogenously
Microbiology:
Streptococci (both aerobic and anaerobic)
Staphylococci,
Gram-negative organisms. (particularly in neonates)
Mycobacterium tuberculosis
fungi
parasites
Actinomyces and Nocardia species
causes of viral hepatitis
hepatitis A-E
EBV
CMV
describe Hepatitis A
faecal-oral transmission
only ever acute
2-6wks incubation period
symptoms of acute hepatitis
Non-specific systemic Sx:
fever, malaise, fatigue, loss appetitte
Abdo pain
Acute raised bilirubin:
Jaundice
dark urine
(pale grey or white stool)
puritis
Investigations for HAV
anti-HAV IgM- acute infection
may be neg first week
anti-HAV IgG- immunity
If ALT>500- order IgM as IgG will not be high yet so will give a false negative
Managament of hep A
mainly supportive
vaccination is available but not in UK
describe Hepatitis B
parental, vertical, sexual
2-6 months incubation
what defines chronic HBV and what are the complications
HBsAg reactivity persisting >6months
comp:
Cirrhosis
hepatocellular carcinoma
extra hepatic manifestations
describe HBV serology
HBsAg- if positive= active infeciton
E antigen- denotes viral replication and will be high with a high viral load
HBcAg- acute infection
AntiHBc Ab- past or present exposure
antiHBs- immune either from infection or immunisation
radiological findings of cirrhosis
coarse echotexture, nodularity, portal HPTN- splenomegaly
tumour marker for hepatocellular carcinoma
alfa fetoprotein
when is HBV vaccine given
2,3,4 months
screening in pregnancy
HBsAg positive, eAg negative: vaccine at birth + routine
schedule
HBsAg positive, eAg positive: vaccine at birth PLUS
HBIG within 48 hours
Describe Hep C
ssRNA, flavivirdae
transmission through blood products, sharing needles, sharing snorting
2wk-6month incubation
40-60%
progress to
chronicity
Investigations for HCV
Hep C RNA PCR should be requested if acute infection suspected
If RNA is negative then it means pt does not have infection
if anti-HCV Ab positive- exposure
managament of HCV
Acute infection:
treated with direct acting antivirals
12wk Tx course OD
describe hepatitis D
Only co-infects with hepatitis B leading to severe acute disease
vaccination agains hep B will protect against hep D
describe hepatitis E
hepeviridae ssRNA virus
2-8wks incubation
never chronic infection except in immunocompromised
30% mortality in pregnant women
extrahepatic manifestations of hepatitis E
thrombocytopenia, red cell aplasia
proximal myopathy, necrotising myositis
encephalitis, ataxia, brachial neuritis
membranoproliferative glomerulonephritis, IgA nephropathy
extrahepatic manifestations of hepatitis B
polyarteritis nodosa
sick serum syndrome
arthritis
cryoglobulinaemia
extrahepatic manifestations of hepatitis C
cryoglobulinaemia
glomerulonephritis
in what situations would a viral infection required treatment with antivirals
COVID- resp failure
chicken pox- varicella pneumonitis
herpes- encephalitis
viral hep- chronic hep C
monkey pox - eye lacerations
general rule of Acute vs chronic infection in terms of DNA and RNA viruses
RNA viruses- acute and generally cleared by immune system (exception to retroviruses)
DNA viruses - chronic infections as they find ways to hide within human body
treatment for HSV encephalitis
Start empiric treatment immediately with iv Acyclovir 10mg/kg tds without waiting for test results
If confirmed, treat for 14 - 21 days *
MOA of acyclovir
guanasine analogue
inhibits DNA synthesis
what metabolises acyclovir to make it active
viral thimadine kinase
complications of CMV in immunocompromised
Colitis
Pneumonitis
Hepatitis
Retinitis
Bone marrow suppression
only treat CMV with signs of complications not just infection
what are owls eyes inclusions a sign of
CMV colitis
complications of congenital CMV infection
ears: sensorineural deafness
eyes: chorioretinitis
heart: myocarditis
neurology: microcephaly, encephalitis
lung: pneumonitis
complication of chronic EBV infection
Chronic infection in immunocompromised->Post-Transplant Lymphoproliferative
DiseaseLatently infected B cells – polyclonal expansion
Predisposes to lymphoma
most common cause of bronchiolitis
Respiratory syncytial virus
Treatment of bronchiolitis in severe cases
- mostly untreatable
- ribavirin
- IgG
What is used as propylaxis for RSV infection
prevention- palivizumab
antiviral drugs in COVID
early infection- antivirals:
-Nirmatrelvir, remdisivir
Late
- steroids
Baricitinib (requiring O2) – JAK inhibitor
IL-6 inhibitors (Tocilizumab / Sarilumab) – advanced respiratory support
complications of BK virus
haemorrhagic cystitis
BK Nephritis & ureteric stenosis
what is the main mechanism of resistance for acyclovir
thymidine kinase mutation
- enzyme involved in metabolising acyclovir to an active form to stop viral DNA synthesis
3 taxonomic families of parasites
Cestodes (hydatid, tapeworm)
Trematodes (lung, liver and intestinal fluke, schisto
Nematodes (roundworms- hookworm, ascarids, strongyloids)
treatment of worms
praziquantel
example of a hydatid disease and what is the definitive host?
echinococcus
dogs
what is the life cycle of schistosomiasis
Cercariae invade human skin when in contact with contaminated water.
Worms develop in venous plexus
Eggs excreted in faeces or urine
Hatch into miracidia, which parasitise snails
Snails release cercariae
Adult schistosomes lay eggs:
Migration of eggs through bladder or bowel causes damage
Retrograde passage of eggs into the liver causes “cirrhosis”
diagnosis of schisto
microscopy:
Urine: S. haematobium
Stool: S. mansoni, S. japonicum
serology
biopsy
signs and symptoms of schisto
fevers, chills
chronic: cirrhosis
examples of soil transmitted helminths
ascaris lumbricoides
trichuris trichiura
hookworm
strongyloids stercoralis
incubation period of p falciparum malaria
1wk-3months
incubation period of viral haemorrhagic fever
3-21 days
treatment for p falciparum
SEVERE: IV artesunate
MILD: oral artemisinin combination therapy eg. riamet,
malerone
what investigation do you need to determine severe from non severe maleria
parasitaemia
examples of malarial prophylaxis
malarone
mefloquine
doxycycline
presentation of malaria
~15 days after bite (vivax several months, falciparum ~10-30days)
fevers- cyclical or ontinuous with spikes
chills, sweats
altered GCS
resp distress
AKI
hepatic failure
coagulopathy
haemolytic anaemia
hypoglycaemia
schiznot : spot diagnosis
maleria
treatment of non-falciparum
3 days oral chloroquine + primaquine 14 days after
CHECK G6PD deficiency
spot diagnosis:
can leave palm print on rash, thrombocytopenia
dengue
what is dengue spread by
ades aegypti mosquito
(bites during the day)
symptoms of dengue
can be asymptomatic
retro-orbital headache
myalgia
nausea, vomiting
sunburn rash- palm print
severe abdo pain
ecchymoses
organ impairment
shock
anorexia, constipation, abdo pain
vacant expression
T39 (himalaya peak temps), HR90
normal Plts
returned from india
gram negative rod on culture
salmonella typhi
management of salmonella thyphi
fluids
IV ceftriaxone with oral azithromycin follow on
Abx of choice for MRSA
vancomycin
what is the cell targeted by EBV and what does it bind to
B cells
binds to complement receptor
opportunistic infections / AIDS defining
pneumocystis jerovecii
TB
JC virus- progressive multifocal leukoencephalopathy
cryptococcus neoformans
Candida
toxoplasmosis
oral hairy leukoplakia
shingles
causes of a ring enhancing lesion with oedema on brain MRI
toxoplasmosis
TB
Bacterial brain abscess
primary CNS lymphoma
uveitis, genital ulcer, oral ulcer
japanese
Bechets
Cancer of what organ is commonly associated with schistosomiasis infection?
bladder
lancfield grouping used to classify which type of pathogenic organism
streptococci
what is the treatment for visceral leishmaniasis
Liposomal amphotericin B
treatment of tapeworms
praziquantel
What is the primary infective lesion produced by Mycobacterium tuberculosis called in the lungs?
ghon focus
caseating granuloma
Give an example of a scoring system which can be used in primary care to guide if antibiotics may be beneficial for a sore throat?
CENTOR
fever, tonsillar exudate, anterior cervical lymphadenopathy, and absence of cough
A Löwenstein-Jensen medium is used to facilitate growth of what respiratory pathogen?
TB
Most common cause of aseptic meningitis
Enteroviruses eg. Coxackie or echovirus
how is cellulitis classified for treatment
Eron classification
I- systemically well and no comorbitities
II- comorbidities either systemically well or unwell
III- significant systemic upset including confusion, hypotension, tachycardia and comorbidities
IV- sepsis or nec fasciitis
admission for IV antibiotics
- class III or IV
- rapidly progressing
- <1year
- periorbital/ orbital cellulitis
most common organism found on central line infections
staph epidermidis
features of legionairres pneumonia and how is it diagnosed and treated ?
flu-like symptoms including fever (present in > 95% of patients)
dry cough
relative bradycardia
confusion
lymphopaenia
hyponatraemia
deranged liver function tests
pleural effusion: seen in around 30% of patients
diagnosis:
urinary antigen test
Rx:
erythromycin/ clarythromycin
features of leptospirosis, RFs and Rx
RFs:
sewage workers, farmers, returning travellers
features:
the early phase is due to bacteraemia and lasts around a week
may be mild or subclinical
fever
flu-like symptoms
subconjunctival suffusion (redness)/haemorrhage
second immune phase may lead to more severe disease (Weil’s disease)
acute kidney injury (seen in 50% of patients)
hepatitis: jaundice, hepatomegaly
aseptic meningitis
Rx:
benzylpenicillin or doxycycline
describe the CURB 65 score
Confusion- 1
Urea >7mmol/L -1
RR >30 - 1
BP <90/60 -1
score 0-1: can be managed in community with amoxicillin PO for 5 days
score 2- amoxicillin PO 5-7 days + clarythromycin
consider admission
score 3-5 - admission, consider ITU, IV co-amoxiclav + clarythromycin 7d
mechanisms of antimicrobrial resistance and examples of each
BEAT
Bypass antibiotic sensitive step- eg. MRSA
Enzyme- mediated drug inactivation eg. beta-lactamases
Accumulation of drug impairment eg. tetracycline resistance
Target modification - eg. quinolone resistance
HIV positive, multiple ring-enhancing lesions on CT scan and a negative thallium SPECT scan.
toxoplasmosis
single, homogenous-enhancing lesion and a positive (rather than negative) thallium SPECT scan
CNS lymphoma
treatment for CNS toxoplasmosis infection in immunocompromised
sulfadiazine and pyrimethamine
antibiotics used for MRSA
- vancomycin
- teicoplanin
- linezolid
what infection is commonly associated with post gastroenteritis lactose intolerance?
giardia lamblia
dry cough, arthralgia, cold agglutanin test/ AIHA, erythema multiforme
mycoplasma pneumoniae
treatment for genital warts
multiple, non-keratinised warts: topical podophyllum
solitary, keratinised warts: cryotherapy
post exposure prophylaxis for HBV
positive HBV-Ag
known responder to vaccine - give vaccine booster
known non responder or no vaccine- give IVIg and vaccine booster
features of HIV seroconversion
3-12 weeks post infection
lymphadenopathy
malaise, myalgia, arthralgia
diarrhoea
maculopapular rash
mouth ulcers
rarely meningoencephalitis
what should be done if an HIV+ person has a CD4+ count of <200/mm3
prescribe co-trimoxazole prophylaxis for PCP
which antibiotic is commonly associated with a disulfiram- like reaction when consumed with alcohol
metronidazole
Sx: nausea, vomiting and flushing
what is cushings triad
Sign of raised ICP
hypertension with a widened pulse pressure
bardycardia
irregular breathing
as a result of cerebrum compression
therefore LP contraindicated
what are some causes of a false positive non-treponemal test for syphilis (eg. VDRL, rapid plasma reagin test)
Some Times Problematic Mistakes Happen
SLE
TB
Pregnancy
maleria
HIV
Negative non-treponemal test + positive treponemal test :
consistent with sucessful treatment of syphilis
Positive non-treponemal test + negative treponemal test
consistent with a false-positive syphilis result e.g. due to pregnancy or SLE
Positive non-treponemal test + positive treponemal test
consistent with active syphilis infection
prophylaxis for animal bites
co-amoxiclav
or
doxy + metronidazole if penicillin allergic
antibiotics used for cellulitis
Eron I
flucloxacillin
erythromycin if penicillin allergic
Eron class II-IV
IV co-amoxiclav, clindamycin, erythromycin, ceftriaxone
lab features of pseudomonas aeruginosa
Gram-negative rod
non-lactose fermenting
oxidase positive
toxins produced by pseudomonas
produces both an endotoxin (causes fever and shock) and exotoxin A (inhibits protein synthesis by catalyzing ADP-ribosylation of elongation factor EF-2)
what antibiotic can cause a black hairy tongue after discontinuation
tetracyclines
