Microbiology Flashcards by Maia Cunningham

What are three ways which antibiotics work?

disruption of cell membrane
disrupt nucleic acid synthesis
disrupt protein synthesis

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What are some drivers of antimicrobial resistance?

human/animal misuse/overuse
suboptimal dosing
healthcare transmission

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Name 3x modes of resistance

restricted access (impermability or efflux pumps)
modification of drug target
inactivating enzymes

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What are the two types of resistance?

Intrinsic/chromosomal (of an entire species)

or
Acquired (through mutation or gene transfer), of a strain

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What method of resistance does MRSA use?

Acquired, changes to penicillin binding protein (target modification)

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What can we use for MRSA?

Vancomycin (IV) or other things (but check susceptibility): clindamycin, cotrimoxazole, doxycycline, ciprofloxacin

e.g. send home with oral clindamycin

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What can we use for MSSA (normal Staph Aureus?)

Flucloxacillin, amox-clav, all cephalosporins + carbapenams

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Beta lactamase production is associated with which gram bacteria?

Gram negative

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How can we target bacteria with B-lactamase production?

Clavulanate or tazobactam

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How to treat ESBL (extended spectrum) bacteria?

e.g. enterobacteria love this

Clavulanate + tazobactam are not reliable, need to use **carbapenam **

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Drugs to treat pseudomonas aeruginosa?

Piperacillin-tazobactam
Ceftazidime, Cefepime
Meropenem
Ciprofloxacin

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What is the virulent component of Staph aureus?

Protein A, a component of the cell wall which bings to Fc protion of antibodies, so IgG and complement cannot bind–> impaired phagocytosis

Protein A adheres S. aureus to vWF –> increased infectiousness at skin penetration

Protein A binds to TNFR-1 receptors –> lung inflamation

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What does Staph aureus cause?

Pneumonia, (IVDU)
Septic arthritis,
Skin infections (cellulitis, impetigo, boils, abscesses)
Bacterial endocarditis (IVDU)
Osteomyelitis

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Which heart valve is most implicated in bacterial endocarditis of Staph aureus?

Tricuspid

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What are the toxin diseases of Staph aureus?

Scalded skin syndrome
Toxic shock syndrome
Food-poisoning

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What does staph epidermis often cause?

Artificial joint, indwelling catheter and valve replacement infections

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Where do we see staph saphro?

UTI in sexually active females

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How do we test for staph epidermis/saphro VS staph aureus?

staph epidermis+saphro are coagulase negative

Staph aureus is coagulase positive

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1) What does not have anaerobic cover?

Amoxicillin-clavulanate
Metronidazole (only treats anaerobes)
Meropenem
Cefazolin

Cefazolin

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2) On piptax for HAP. Gets C diff. AKI, WCC 30. lactic acidosis

Treatment?
Oral vancomycin + urgent surgical review
Oral metronidazole
Fecal transplant
Stop antibiotics (not sufficient alone)

Oral vancomycin + urgent surgical review

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Inpatient for stroke, fever, on review has phlebitic. gram positive cocci!

Remove line and start flucoloxacillin
Start vanco and ceftrizone
Echo as likely has endocarditis
Await coagulase status

Remove line and start flucoloxacillin

If they were not feverish/phlebitis, w8 4 coag status b4 treatment.

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Elbow surgery -> febrile with mucky wound. Likely cause?

Staph aureus + strep pyogenes
E coli + Pseudomonas aeruginosa
Staph haemolyticus, strept agalactiae ( normal bugs
Candidas albicans, anaerobes

Staph aureus + strep pyogenes

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What is not a risk factor for leptosporiasis?
Triathalon in lake
Abbatoir worker
Working in rat infested shop
Eating raw chicken

Eating raw chicken

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How does toxoplamosis present in an immunocompromised person?

Asymptomatic
Pharyngitis
Encephalitis
Mono-nucleosis like syndrome (this or asymptomatic in NORMAL person)

Encephalitis

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Bloody diarrhea after going to SE Asia Likely pathology? Shigella Listeria Giardia Norovirus

Shigella THE REST CAUSE SMALL BOWEL PRESENTATION - large volume crampy Shigella most likely LB and travel

Spreading erythema over leg, non fluctuant and no wound. Most likely organism? Streptococcus pyogenes Staph aureus MRSA

Streptococcus pyogenes | NON-PURULENT

Dog bite to hand, erythema + pus from wound. Which abx? Amox-clauv Fluclox Cefalexin Doxyxycline

Amox-clauv

Recurrent skin abscesses, previous MRSA. New boil on leg but otherwise well what is most appropriate? Flucloxacillin Cefalexin Co-trimoxazole Vancomycin

Co-trimoxazole Pencillin + cephlosporins (first two) wont work Vancomycin is IV drug, not in community Co-trimoxazole best

IVDU fevers and general malaise , splinter haemorrhage + murmur of Left sternal edge. What next? Treat with ceftrizone + vancomycin 3 blood cultures and wait for results Admit to hospital for.6 weeks abx Start flucloxacillin + organise transosephageal echo.

3 blood cultures and wait for results Patient is not that sick and who knows what bug he has (iV drug user)

10kg loss, changed bowel habit, anaemia + now unwell with fevers and malaise for 2 weeks. Most likely bug? Strept gallolyticus Staph aureus Enterococcus faecalis Eikenella corrodens

Strept gallolyticus Very specific bug associated with colorectal cancer --> subacute endocarditis EF could also present like this but the history is key Eikenella more likely with dental work

Aortic valve replacement. obstructed renal stone, Fever, unwell 2 weeks. BC positive with gram positive cocci endocarditis What bug? Enterococcus faecalis Strep viridans Staph aureus Streptococcus pyogenes

Enterococcus faecalis All are gram positive, renal hx - enterococcus faecalis (can commonly colonize the urine) Viridans - usually to do with mouth e.g. dental

Recent dental work, 4/52 unwell. 3x BC grew strep viridans. Most appropriate abx? Penicillin Amoxicillin Vancomycin Flucloxacillin

Penicillin

Metastatic melanoma with brain mets. Dexamethasone 8mg for last 7 weeks, SOB + hypoxia. Most likely organism? Legionella Pneumocystic jiroveci RSV Pseudomonas aeruginosa

Pneumocystic jiroveci Steroids predispose to this. SOB + hypoxic, bilateral infiltrates CXR is the picture.

AML< induction chemo. Neutropenic 20 days. New fever + cough. CT shows nodules with surrounding ground glass ?bug Aspergillus fumigatus Candida albicans Staph aureus Cryptococcus neoformans

Aspergillus fumigatus

New HIV, CD4 count 20. Has headache fever meningism. LP high opening pressure. Bug? Cryptococcus neoformans HIV encephalitis Listeria Pneumocystis jiroveci

Cryptococcus neoformans

Multiple abx for recurrent chest infecitions/ Itchy white discharge. Tx? Fluconazole Flucytosine Terbinafine (nails) Amphotericin B (usually for serious invasive fungal infections)

Fluconazole

Lung cancer, high dose steroids. Change in taste, pain and difficulty swallowing. White plaques on tongue.

Fluconazole orally Nystatin drops not sufficient

Return from Vietnam 1wk ago. High fever, headache, myalgia, rash for 2/7. What test made the diagnosis? Dengue NSI antigen Leptospirosis PCR Blood culture with gram neg bacilli Ebola PCR

Dengue NSI antigen Typhoid wouldn't cause myalgia and rash as commonly as dengue

Returned from Uganda 2/52 agoo, High fever, malaise, abdo pain, 10% parasites in blood. Treatment? Doxycycline IV artesunate Chloroquine Artemether-lumafantrine

IV artesunate Falciporim (from Africa), 10% parasites is severe Art-Lum also treats malaria, but this is for less severe Doxycycline is a prophylaxis

Return from visiting parents in India 2 wks ago. High fever, anorexia, abdo pain last week. Dx? Malaria Typhoid Dengue Leishmaniasis

Typhoid

Risk factors for brucella? Unpasteurized milk Tick bite Floodwater exposure Childcare centres

**Unpasteurized milk** Tick bite Floodwater exposure Childcare centres Goats + cows predominantly

Fever, cervical lymphadenopathy + deranged LFTs. What is unlikely to cause this? HIV Toxo CMV Influenza

Influenza

Patient with CAP. Which does not need legionella cover? Severe pneumonia Summer season Winter season Recent potting mix exposure

Winter season

Which abx do not provide legionella cover? Doxycycline Azithromycin Amoxicillin Ciprofloxacin

Amoxicillin | Beta lactams do not

Fever, cough, SOB + consolidation on CXR. Likely pathogen? Strep pneumoniae Strepto pyogenes Strepto agalactiae Streptococcus mutans

Strep pneumoniae

Strep pneumoniae --> meningitis, what to treat with? Ceftrixone 2g q12h Ceftriaxone 2g q24h Amoxicillin 2g q4h Vancomycin 1.5g q12h

Ceftrixone 2g q12h

Simple cystitis. ESBL E-coli. What drug to NOT use? Nitrofuantoin Trimethoprim Cefalexin Meropenem

Cefalexin | Cephalosporin! Mero is typical, and the others could work

Old lady has fever, confusion and new urinary symptoms. Which drug? Nitrofuantoin Flucloxacillin Meropenem Ceftrixone

Ceftrixone

MRSA bacteraemia, multiple brain abscess. Which abx is best? Vancomycin Doxycycline Clindamycin Flucloxacillin

Vancomycin

Which is a Macrolide? Clindamycin Tobramycin Gentamicin Azithromycin

Azithromycin

UTI. Reg meds methotrexate, aspirin, prednisone, simvastatin, omeprazole. Which drug must be avoided? Nitrofurantoin Amoxicillin Cefalexin Trimethoprim

Trimethoprim Affects folate pathways - methotrexate --> pancytopenia

Man with urethral discharge, recent unprotected sex. Gram neg cocci. Cause? Gonorrhea Chlamdia Syphillis Mycoplasma genitalium Cannot gram stain the rest

Gonorrhea Cannot gram stain the rest

Male presents with urinary sx + pelvic pain, Tender prostate on exam. Abx? Nitrofuantoin Cotrimoxazole Gentamycin Trimethoprim

Cotrimoxazole

Complicated UTI (prostate) - need systemic so nitro + trimeth off the list. Gentamycin does not enter tissue/abscess, better for bloodstream. Full STI screen female: HIV + syphillis serology, oral rectal + vaginal swabs for NAAT Vag swab for trichomonas + BV First pass urine chlamydia + gonorrhoea Tell her doesn't need testing

HIV + syphillis serology, oral rectal + vaginal swabs for NAAT

Female with dysuria + frequency. Least likely pathology? Staph saphrophyticus E coli Pseudomonas aeruginosa Proteus mirabilis

Pseudomonas aeruginosa

Man with dementia with fractured hip. Urine from catheter --> enterobacter clocae. Action? Treat with amox-clav Treat with nitro Change catheter + resend sample Do nothing as no sign of infection

Do nothing as no sign of infection

Man never tested/treated for syphillis before, asymptomatic. Serology EIA reactive, TPPA reactive, RPR 1:64. What should we treat it as? Primary Secondary Early latent Late latent

Late latent Aymptomatic - must be latent. Cannot say due to unknown duration - treat as late as safer, most rigid treatment.

Abscess on thigh in young main. Most likely pathogen? E coli Streptococcus pyogenes Staph aureus Staph epidermis

Staph aureus

Smelly urine grew pseudomonas. What do you do? Treat with IV piperacillin-taxobactam Ciprofloxacin Take another urine culture Do not treat + reassure

Do not treat + reassure Smelly urine is not a symptom. NO dysuria, frequency or systemic symptoms.

Abx for MRSA? Flucloxacillin Cefazolin Piperaciillin-tazobactam Co-trimoxazole

Co-trimoxazole

HIV lost to follow up. PJP presentation. What is not an AIDS defining infection? Kaposi sarcoma Toxoplasmosis encephalitis Leptospirosis Cryptosporidium

Leptospirosis

IV patient, CD4 count 800, VL undetectable. New partner, wants advice on risk. Partner needs PREP + condoms. Advise no sex. Advise not to disclose. No risk of transmission. Discuss PREP for casual sex, condoms for other STI

No risk of transmission. Discuss PREP for casual sex, condoms for other STI

New HIV with CD4 180. What is at the least risk of? TB CMV retinitis Oesophageal candidias Pneumocystitis

CMV retinitis <200 so more infections but… <100 toxo, <50 CMV TB at any CD4 count.

New HIV CD4 count 230. VL 200,000. What will happen once he starts treatment? Counts wont change CD4 rise, VL undetectable Risk in both CD4 count + viral load Reduction in both CD4 + viral

CD4 rise, VL undetectable

45M with new RUQ pain, jaundice, fever, Bloods: HBsAg positive, anti HBc IgM positive. What is prognosis? Risk of fulminant hepatitis is high (50%) 90% chance of progressing to chronic HBV Likely to recover in 3 months, unlikely to progress to chronic HBV Reasonable risk of developing hepatocellular carcinoma (25%)

Likely to recover in 3 months, unlikely to progress to chronic HBV New infection of hep B, new onset in an adult will likely go away. IgM positive means acute infection. Last 6 months. If get this as a kid, 90% change of progressing to chronic Hep B.

Which patient with Hep B are we most likely to treat? 12 asymptomatic, normal LFTS, VL 500000 copies 34F pregnant, HBsAg negative, Anti-HBc Ab positive, negative HBV DNA 50y Male, ALT 300, HBeAg neg, VL 10,000 copies 50y M, ALT 30, HbeAg positive, VL 100000 copies

50y M ALT 300, HBeAg positive, VL 100000 copies HBsAg = surface antigen, currently have the virus, could be acute or chronic HBeAg = e-protein, similar to above Anti-HBc Ab = antibody, indicates protection either through vaccine or past infection anti-HBc or HBcAB = core antibody, means a past or current hep B infection. --> does not provide protection against hep B like above Would treat the one with LIVER inflammation Pregnant has PAST Hep B

Relapse rate for Maviret with Hep C? 50 1 90 10 Cures pretty much everybody.

Which Hep most worried about in pregnancy for mother? A D C E

E E big issue in pregnancy. B would be an issue in pregnancy for vertical transmission.

Latent TB infection Treatment 95% efficacious Patients should be treated as they are infectious Patients have cavities on CXR 80% will eventually develop active TB

Treatment 95% efficacious Latent - non-infectious, generally no cavities, just tiny calcified granulomas. 5-10% progress to active TB lifetime risk.

Which vaccine bad for pregnant? Covid Varicella Meningococcal ACWY Pertussis

Varicella + MMR

Which is not effective against pseudomonas? Ciprofloxacin Piperacilin-tazobactam Ceftriaxone Ceftazidime

Ceftriaxone

Newborn baby w/ hearing loss ?CMV. What is best test? Maternal CMV serology Urine CMV PCR Baby CMV IgG Placental histology

Urine CMV PCR Within 3 weeks. After 3 weeks could've been from community Babies don’t make IgG

What mechanism of resistance does ESBL employ?

Inactivating enzyme (beta-lactamase) Resistant to all penicillins and cephalosporins