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Genitourinary infections Flashcards

1
Q

What are most common organisms causing UTIs?

A 
E. coli 70%
Klebsiella
Proteus
Enterobacter spp
Enterococcus faecalis
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2
Q

Which patients require imagining of urinary tract, if pyelonephritis suspected?

A

All male patients

Females if >2 episodes of pyelonephritis

any patient with Proteus species isolated

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3
Q

Patient on CAPD for chronic renal failure. Last 24 hours noted dialysis fluid is cloudy, with mild abdominal pain.

What is most likely cause of this infection?

A

Staph aureus/ CoNS - 50% infections

gram neg including pseduomonas

fungi (candida) 5% - particularly if culture results are negative

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4
Q

Patient on CAPD for chronic renal failure. Last 24 hours noted dialysis fluid is cloudy, with mild abdominal pain.

Fluid sent for analysis

What criteria are used to confirm microbiological diagnosis of infection?

A

Cell count >100mm3, usually >50% polymorphs

fluid also grown in blood culture bottles

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5
Q

Patient on CAPD for chronic renal failure. Last 24 hours noted dialysis fluid is cloudy, with mild abdominal pain.

What is empirical treatment?

A

Intraperitoneal vancomycin and gentamicin

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6
Q

Patient on CAPD for chronic renal failure. Last 24 hours noted dialysis fluid is cloudy, with mild abdominal pain.

Pseudomonas isolated.

Patient on vancomycin and gentamicin.

Does organism alter antibiotic management?

A

Can stop vancomycin

Once improved, switch to ciprofloxacin for 21 days total treatment

Need to exchange PD line, as pseudomonas forms biofilms

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7
Q

Renal transplant patient has rising creatinine, concerns about rejection.

Urine microscopy shows “decoy cells”

What does this mean?

A

Decoy cells are infected epithelial cells, which have large, abnormal nuclei. Can sometimes look like cancer cells

In this case, like due to BK virus

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8
Q

What is usual natural history of BK virus infection?

A

50% of children infected by age 4 - most asymptomatic
80% of adults infected

transmitted respiratory, faecal-oral, sexual, transplant

remains latent in renal tubular epithelial cells. First sigsn of re-activation include slowly rising creatinine

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9
Q

What are symptoms of BK virus reactivation in immunosuppressed/ renal transplant patients?

A

Tubule-interstitial nephritis

haemorrhagic cystitis

pneumonitis

meningoencephalitis

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10
Q

How to diagnose BK reactivation

A

renal biopsy gold standard

BK virus DNA PCR - blood or urine

BK virus decoy cell microscopy - can be useful as screening tool

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11
Q

19 year old with fever, flank pain.

Urinalysis showed >50 white cells, 10 red cells, 3+ bacteria

gram negative rod seen, which is beta haemolytic

What is significance of WCC?

A

normal urine <10 white cells

> 50 suggests infection/ inflammation

bacteria colonies help point towards infection

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12
Q

19 year old with fever, flank pain.

Urinalysis showed >50 white cells, 10 red cells, 3+ bacteria

gram negative rod seen, which is beta haemolytic

What is causative organism?

A

E. coli can often be beta haemolytic

Pseudomonas is only other GNEG which is beta-haemolytic. But this would be less likely as young, and no catheter

Can differentiate between these, as E. coli will be lactose fermenter, and Pseudomonas will not

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13
Q

19 year old with fever, flank pain.

Urinalysis showed >50 white cells, 10 red cells, 3+ bacteria

E. coli in culture

Had amoxicillin with GP, which she failed to complete.

What is explanation for deteriorating?

A

Amoxicillin selected for resistance organism e.g E. coli

This pressure likely caused move of antimicrobial resistance plasmid ESBL

This provides resistance to penicillin and cephalosporins

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14
Q

What are treatment options for ESBL UTI?

A

Meropenem IV

Nitrofurantoin/ fosfomycin oral

Need to check sensitivities, as can be sensitive to other agents e.g tazocin, co-trimoaxozle, cipro, get

ESBL provides resistance to penicillin/ cephalosporins, but often confers resistance to multiple other antibiotics

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15
Q

What are features which indicate pyelonephritis over cystitis?

Cysitis - bladder
Pyelonephritis - kidney

A 
Systemic symptoms -
fever
flank pain
hypotension
tachycardia

urinalysis - white blood cell casts

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16
Q

Why is it important to differentiate cystitis from pyelonephritis?

A

cystitis treatment duration is 3 days female, 7 days male

pyelonephritis is 7-14 days treatment

pyelonephritis will require imaging to assess for renal stone obstruction

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17
Q

What are virulence factors, which allow E. coli to infect urinary tract?

A

P fimbriae - adhesion, and resistance to phagocytosis

haemolysin - directly cytotoxic

aerobactin - siderophore which is molecule which scavenge iron, an essential nutrient for bacteria

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18
Q

What are reasons that a gonococcal vaccine cannot be produced?

A

Vaccines normally target exotoxins or cell surface component

Gonorrhoea does not produce conventional exotoxin

Gonorrhoea can re-arrange pilin genes, called antigenic variation. Which changes the pili expressed on surface

19
Q

Chlamydia used detected via NAAT

What media can be used for culture?

A

McCoy cells

fluorescin stain can show intracellular chlamydia

20
Q

What is life cycle of chlamydia?

A

infectious elementary body is endocytosed

bacteria develop into reticulate bodies, which are reproductive form

reticulate bodies then reproduce, and condense to form elementary bodies, which are released when cell lyses

21
Q

What infections do different serovars of chlamydia trachomatis cause?

A

Chlamydia trachomatis A/ B/ C - trachoma

Chlamydia trachomatis D-K - genital chlamydia

Chlamydia trachomatis L1 -L 3 - LVG

Chlamydia psitacci - pneumonia

Chlamydia pneumoniae - pneumonia

22
Q

16 years old presents with crampy abdo pain, vaginal bleeding, abnormal discharge.

Considering PID

Swabs for chlamydia/ gonorrhoea NAAT are negative.

Why does treatment still need to cover for these organisms?

A

Swabs are often endocervical, so cannot exclude upper genital infection e.g ovaries/ fallopian tubes

23
Q

What are differential diagnoses for ulcerating genital lesions?

A

Painful -
HSV
LVG
Chancroid

Painless
Syphilis
Donovanosis

24
Q

HSV2 is usual culprit of encephalitis

Why are cases of HSV1 encephalitis rising?

A

Unclear

Possibly higher rates of oral sex, leading to higher HSV1 transmission

Primary HSV1 genital infection may then lead to encephalitis

25
Q

26 year old female with white genital discharge.
Wet mount prepared, which shows organism.

What is diagnosis?

What other genital infections can be detected by wet mount prep?

A

Trichomonas - NAAT testing now more commonly used, which does Chlamydia/ gonorrhoea as well

Candida - yeast and pseudohyphae will be seen

26
Q

What are consequences of untreated trichomonas infection in pregnancy?

A

Preterm labor
Premature rupture of membranes
LBW baby

27
Q

Why HPV types causes -

genital warts

cancer - cervical/ anal/ oropharyngeal

A

genital warts - 6/ 11

cervical cancer - 16/ 18 cause 70% of cancers

28
Q

HPV causing cervical cancer

What classification systems are used to grade pre-malignant changes?

A

Bethesda system - cytological findings

29
Q

Urine culture on chromogen plate suggests staph aureus. This is sub-cultured onto other plates to help identify what type of staph

What plate is useful?

A

Novobiocin disc

Sensitive - Staph aureus
Resistant - Staph saprophyticus (CoNS)

30
Q

Patient with tape worm coming out of anus.

Worm is quite wide and flat.

What species of tape worm is this?

A

Diphyllobothrium latum

Latum is latin for broad or wide

31
Q

Which part of tape worms contain eggs?

A

Scolex (head) attached to segments called proglottids

These rectangular proglottids contain eggs. They are broken off and passed in stool.

In lab can crush proglottid which release eggs, can be viewed microscopy

32
Q

What is definitive host of Diphyllobothrium latum?

A

Fish tape worm - but humans are definitive host. Worm replicates in humans

uncooked white fish/ sushi are common sorke

33
Q

What are common tape worms which infect humans?

A

Diphyllobothrium latum - fish

Taenia solium - pork. Causes cysticercosis

Taenia saginata - beef

Humans are definitive hosts for all 3. It is a naming convention irony, that they are named after the species which they use as intermediary host

34
Q

E. coli
E. histolytica
E. moshkovskii

All appear similar microscopically. How can we distinguish species?

A

E. histolytica will have phagocytosed red cells.

35
Q

Blood culture positive

Gram neg bacilli
Macconkey - non-pigmented colonies
H2S producing

A

Non-pigmented colonies on Macconkey suggests non-lactose fermenters

Patient with gastroenteritis - this would suggest non-typhoidal salmonella

Humans are natural host and reservoir for salmonella. But can be zoonosis from birds/ reptiles

36
Q

Salmonella species have increasing resistance to fluoroquinolones

What is most common mechanism of resistance?

A

Mutation of binding site of DNA gyrase - gyrA gene

Ceftriaxone and azithromycin are other options for treatment

37
Q

STEC producing E. coli can cause HUS.

What is pathophysiology which causes death in HUS?

A

5% mortality - usually children <5

Haemolysis - anaemia
Thrombocytopenia
Uraemia and raised creatinine

Shiga toxin bind to and damage endothelial cells of renal tubules

38
Q

What are sources of E. coli infection?

A

uncooked beef is most common. It is common commensal/ pathogen in bovine

Run-off water from cattle, can affect crops. So leaf vegetables - lettuce, spinach, sprouts. Impossible to wash thoroughly before eating

Petting zoos are also common sources of outbreaks

39
Q

Severe sepsis can cause DIC.

What is pathophysiology?

A

systemic activation of coagulation cascade in an unregulated manner

Causes intravascular deposition of fibrin - resulting in occlusive thrombi of microvasculature

Causes consumption of platelets and clotting factors - can lead to bleeding and bruising

infection can cause activation of cytokines. But non-infectious causes such as trauma, burns, malignancy can cause DIC

Neiserria meningitidis has lipopolysacchardie on outcer capsule, which can lead to DIC, and meningococal rash. Bacteria + antibody complex depositon also contributes to rash. DIC can cause also adrenal haemorrhage and Waterhouse-Friedrichsen syndrome

40
Q

Filter feeders such as shellfish and oysters can harbour GI pathogens - as they ma filter raw sewage.

What are some examples?

A

HAV

Vibrio species

41
Q

Cirrhosis patients are at greatly increased risk of infection with vibrio species e.g V. vulnifucus

Why is this?

A

Greatly reduced levels of complement - causing reduced chemotaxis and phagocytosis

42
Q

Some bacteria have quorom sensing. What is this?

A

Different bacteria in population can have different gene expression.

One set of quorom sensing-regulated genes are expressed at low bacterial concentrations, and another at high bacterial concentrations

This means best genes are present, at correct time, for optimisation - symbiosis, virulence, motility, biofilm formation, antibiotic production

43
Q

HBeAg appears shortly after HBsAg, and persists for 3-6 weeks before disappearing (before HBsAg disappears)

HBeAg is a marker of viral replciation.

What is significance of any mutations which affect HBeAg?

A

core/ pre-core promoter mutations render HBeAg negative, or reduce its expression.

These mutations are associated with higher liver disease, and higher rates of HCC

Treatment guidelines have lower threshold for treatment in these patients

44
Q

Patient has been fully vaccinated against HBV.

They then acquire HBV infection, and hepatitis.

How can we explain this?

A

Vaccine used is a recombinant vaccine

  • some people do not respond to vaccine, so we should measure anti-HBs levels
  • mutation of S gene in HBsAg, can cause infection, but vaccine will not protect. This is termed a vaccine-escape mutant. It is very rare. Usually results in reduced transmissibility, so less-fit virus

Question Bank (33 decks)

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