Past papers 2 Flashcards
Components of cell walls
- NAG
- Lipid A
- Ergosterols
- Mycolic acid
- LPS
- Mycobacteria
- Fungi
- Peptidoglycan
- LPS
Lipid A - endotoxin - Mycobacteria
Mycolic acid - Fungi
Ergosterol - Peptidoglycan
The sugar component consists of alternating residues of β-(1,4) linked N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM)
Identification of organisms
- Modified Zn stain
- Thin blood film – Giemsa stain
- Concentrated iodine
- Calcofluor white stain
- Filamentous fungi on BAL
- Cryptosporidium
- Ova in stool
- Malaria
- Filamentous fungi on BAL
Calcofluor white stain - used to stain yeasts - Cryptosporidium
Modified Zn stain - Ova in stool
Concentrated iodine - Malaria
Thin blood film – Giemsa stain
patient with HIV cryptococcal meningitis was treated with caspofungin. Why is this is bad choice?
poor CSF penetration
too expensive
crypto resistant
contradicted in AIDS
Echinocandins are ineffective against cryptococcal
Another similar question exists with answer:
- cryptococcus is resistant to echinocandins as it does not contain 1,3 beta-d-glucan synthase
Cryptococcus does contain 1,3 beta-d-glucan synthase, but resistance is intrinsic by other means
Correct answer in that example is poor CSF penetration
Match the following organisms with the clinical pictures
Neisseria gonorrhea chlamydia trachomatis candida albicans treponema pallidum haemophilus ducreyi calymmobacterium granulomatis ureaplasma urealyticum trichomonaas vaginalis
- A 20 year old man presents with dysuria and uretheral discharge.A gram stained smear of a uretheral swab shows numerous pus calls but no organisms were detected
- A 34 year old man returning from Thailand where he had unprotected sex presents with a painless ulcer on his penis
- A 24 year old woman presents with arthritis and skin rash
- A 30 year old pregnant woman presents with itch and soreness and a thick white discharge
- A recent immigrant from Africa presents with a painful ulcer on his penis which bleeds on touch associated with tender enlarged inguinal lymph nodes, bacteriologic smear and culture were done but they were not helpful.
- A 20 year old man presents with dysuria and uretheral discharge.A gram stained smear of a uretheral swab shows numerous pus calls but no organisms were detected
Chlamydia trachomatis - A 34 year old man returning from Thailand where he had unprotected sex presents with a painless ulcer on his penis
treponema pallidum - A 24 year old woman presents with arthritis and skin rash
Neisseria gonorrhoea - A 30 year old pregnant woman presents with itch and soreness and a thick white discharge
trichomonas vaginalis - thick white discharge
candida albicans - usually cottage cheese
Bacterial Vaginosis - Gardnerella. Usually fishy smell - A recent immigrant from Africa presents with a painful ulcer on his penis which bleeds on touch associated with tender enlarged inguinal lymph nodes, bacteriologic smear and culture were done but they were not helpful.
haemophilus ducreyi
32wks pregnant lady with confirmed rubella.
Advice:
termination of pregnancy
child likely to be born with severe deformities
no risk of infection to fetus
risk of infection present, but deformities rare
risk of infection present, but deformities rare
No risk of documented abnormalities if infection occurs after 20 weeks
Woman develops rubella infection 8 days into pregnancy – what are the consequences for the foetus?
Miscarriage/ stillbirth
microcephaly
cardiac disease
visual problems e.g cataracts
Deafness
Pregnant woman is both HBV and HCV positive. Her newborn baby should receive the following treatment?
- Zidovudine
- Human Hep B immune globulin and full Hep B vaccination
- Human immune globulin only
- Interferon
Human Hep B immune globulin and full Hep B vaccination
Congenital infections.
- Toxoplasma gondii
- Chlamydia trachomatis
- Rubella
- Listeria monocytogenes
- CMV
- Treponema pallidum
- Parvovirus B19
- Pregnant woman had flu-like illness which is followed by a septic abortion. Autopsy of infant shows granulomas in liver
- A baby born with IUGR and hepatosplenomegaly
- A pregnant woman develops fetal hydrops on ultrasound
- A 2 month old infant presents with conjunctivitis and pneumonia
- Pregnant woman had flu-like illness which is followed by a septic abortion. Autopsy of infant shows granulomas in liver
Toxoplasma - A baby born with IUGR and hepatosplenomegaly
CMV - A pregnant woman develops fetal hydrops on ultrasound
Parvovirus B19 - A 2 month old infant presents with conjunctivitis and pneumonia
Chlamydia trachomatis
- A pregnant woman, 12 weeks gestation, is picked up at antenatal screening as HIV+ve. CD4 count is 500, viral load is 9000, the patient is asymptomatic and clinically well. Which of the following is the most correct?
a) Perform amniocentesis to detect whether the baby is infected
b) Do nothing and treat the baby after birth
c) Commence short-term antiretroviral therapy from the second trimester
d) A Ceasarian section is virtually unavoidable
Commence short-term antiretroviral therapy from the second trimester
Mother should then continue long term ARV - new evidence that should be on ARV regardless of CD4 count
Baby should get ARV e.g zidovudine
HBIG HBIG and hep B vaccination High dose hep B vaccination VZIG VZIG plus vaccination VZV vaccination HNIG Do nothing
- Baby of hep B eAg positive mother
- Neonate whose mother developes chickenpox 2 days post delivery
- Non-immune pregnant woman in contact with measles
- CRF patient, not currently on dialysis but who will be commencing dialysis in the near future
- Non-pregnant paediatric nurse, is not varicella immune, who has been looking after her mother with ophthalmic zoster
- Baby of hep B eAg positive mother
HBIG and hep B vaccination - Neonate whose mother develops chickenpox 2 days post delivery
VZIG - no cross-placenta antibody transfer. Give up to 7 days old - Non-immune pregnant woman in contact with measles
HNIG - CRF patient, not currently on dialysis but who will be commencing dialysis in the near future
High dose hep B vaccination - Non-pregnant paediatric nurse, is not varicella immune, who has been looking after her mother with ophthalmic zoster
VZV vaccination - occupational exposure
Pregnant woman 14 weeks, concerned re risk of toxoplasma and present to GP for testing. Results show weak positive IgM, positive IgG, predominantly
high avidity. What should she be advised?
Pregnancy likely to be severely affected and advise termination
Baby should receive sulphadiazine and pyrimethamine after delivery
Mother should receive sulphadiazine and pyrimethamine for duration of pregnancy
Mother should receive spiramycin for duration of pregnancy, baby is unlikely to be affected
spiramycin is recommended for women whose infections were acquired and diagnosed before 18 weeks gestation and infection of the fetus is not documented or suspected. Spiramycin acts to reduce transmission to the fetus and is most effective if initiated within 8 weeks of seroconversion. 40% of primary infection in pregnancy will infect foetus
Congenitally infected newborns are generally treated with pyrimethamine, a sulfonamide, and leucovorin for 12 months.
spiramycin is a macrolide
Pregnant woman tests positive for toxoplasma in pregnancy.
May present with flu-like illness, lymhadenopathy
What are risks to foetus?
Miscarriage
hydrocephalus
retinchoroiditis
Pregnant woman tests positive for toxoplasma in pregnancy.
What is treatment?
If diagnosed before 18 weeks gestation - Spiramycin to reduce risk of transmission.
USS/ choriamniocentesis - assess if baby affected. If affected, start pyremethamine/ sulphadiazine/ folinic acid for treatment (stop spiramycin)
Does toxoplasma infection always need treated?
Treat if immunocompromised, or pregnant
If otherwise well, after flu-like illness, toxoplasma will form cysts, and symptoms will resolve. Will only reactivate if become immunocompromised
Pregnant women 18 weeks, brings child who has
chickenpox to GP. Mother is
sure she has not had VZV. What should the GP do?
a. Issue prophylactic acyclovir
b. Issue VZIG
c. Test for VZV IgM
d. Test for VZV IgG
Test for VZV IgG ??
If non-immune, offer VZIG within 10 days
A pregnant woman returns from India and dies shortly after her return of an acute illness. Which of the following is most likely the cause?
Brucella Typhus Hep A Hep D Hep E
HEV
- A baby born to mother with primary CMV infection in pregnancy is detected to have 20000 copies/ml CMV in urine 2 days after birth. The most appropriate management strategy is:
a. Reassure and do nothing
b. Treat with IV Aciclovir for 2 weeks
c. Treat with IV Ganciclovir for 2 weeks
d. Refer for audiology assessment
e. Check CMV IgM in baby
Refer for audiology
If baby is well, and audiology/ brain imaging normal, then likely do not need to treat.
Aciclovir incorrect
Ganciclovir - should be for 6 months
IgM incorrect
A 24 week pregnant staff nurse sustains a needlestick from a HBSag positive patient who is HbEag positive. She has received 3 HBV immunisations in the past, and anti HBS level is < 10. The correct management is:
a. Give HBV vaccine dose and HBIG
b. Give infant HBIG at birth
c. Do nothing
d. Treat with Lamivudine
Give HBV vaccine dose and HBIG
Pregnant woman (36 weeks) suffers a rash illness, then presents to GP. Blood taken shows: Rubella IgG positive, IgM negative, Parvovirus IgG positive, IgM positive. What is the most likely outcome?
a. Normal healthy child
b. intra-uterine death
c. congenital rubella syndrome,
d. Hydropsfetalis
normal healthy baby
No risk of documented abnormalities if infection occurs after 20 weeks
A pregnant woman (32 weeks gestation) present with painful ulcer on her vagina. HSV2 PCR comes back positive. What would be you action?
Treat with acyclovir and treat baby
tell her all will be fine
treat with acyclovir and consider elective caesarian
measure HSV2 antibody to see if it is primary infection deliver by emergency section
treat with aciclovir, and consider elective caesarian section
45yrs old male,travels to Mexico, presenting with a rash followed by pneumonia
CXR: cavitating lesion.
Cause?
Coccidioides
Child with rash on face and shoulders. Then develops desquamation of palms /soles
what is cause?
GAS - Scarlet fever
Child with conjunctivitis, then develops pneumonia.
What are potential causes?
Chlamydia trachoamtis - neonatal
Measles
Scaly rash with skin depigmentation, microscopy shows yeasts and small hyphae:
Trichophyton
Microsporum
candida
M. furfur
M furfur - pityriasis versicolor
What is pediculus humanus?
Human louse
A. Herpes zoster B. Herpetic whitlow C. Hot tub folliculitis D Cat scratch E. Kawasaki F. Lyme Disease G. Erysipelothroid H. Sporothricosis I. Herpangina
Which is the most accurate presentation:
- Large salmon coloured lesion of erythema migrans with central clearing due to tick bite
- Disease of childhood, lesions in mouth which become vesicular with a grey base and punched out edge
- Desquamation and prominent papillations on the tongue
- Vesicular rash with pustular lesions, erythema and painful swelling of the digits
- Migrating lymphacutaneous lesions in thigh of young man following dirt bike accident
- Large salmon coloured lesion of erythema migrans with central clearing due to tick bite
Lyme disease - Disease of childhood, lesions in mouth which become vesicular with a grey base and punched out edge
Herpangina - also called mouth blisters. Coxsackie virus - Desquamation and prominent papillations on the tongue
Kawasaki - Vesicular rash with pustular lesions, erythema and painful swelling of the digits
Herpetic whitlow - Migrating lymphacutaneous lesions in thigh of young man following dirt bike accident
Sporotrichosis
A. Herpes zoster B. Herpetic whitlow C. Hot tub folliculitis D Cat scratch E. Kawasaki F. Lyme Disease G. Erysipelothroid H. Sporothricosis I. Herpangina
- Vesicular rash with dermatomal distribution
- Acute self limiting infection due to Pseudomonas aeruginosa
- Maculopapular lesions on fingers after cleaning fish
- Prominent cervical lymphadenopathy and primary inoculation lesion
- Vesicular rash with dermatomal distribution
Herpes Zoster - Acute self limiting infection due to Pseudomonas aeruginosa
Hot tub folliculitis - Maculopapular lesions on fingers after cleaning fish
Erysipelothroid - Prominent cervical lymphadenopathy and primary inoculation lesion
Cat scratch disease
Fisherman’s wife presents with cellulitis of one finger.
What is possible cause?
Eryispelothrix
Gram pos bacilli
Infection in humans is often occupationally related, occurring most frequently in people whose jobs are closely related to contaminated animals, their products, wastes, or soil. Butchers, abattoir workers, veterinarians, farmers, fishermen, and fish-handlers are at highest risk of infection.
Rashes a- Roseola infantum b- Erythema infectiosum c- Scarlet fever d- Molluscum contagiosum e- Measles f- Herpangina g- German measles
- A 10 year old girl presents with pinkish umblicated warty lesions on her buttocks
- A 7 year old boy presents with high fever,sore throat ,enlarged painful cervical lymph nodes ,strawberry tongue and a diffuse erythematous rash
- A 3 year old boy presents with fever and painful vesicles in his mouth
- A seven year old boy presents with fever and intense erythema of the cheeks followed by spread of the rash to the trunk for only one day
A 9 month infant presents with fever and wide spread macular rash. Tests were +ve for human herpes virus 6
- A 10 year old girl presents with pinkish umblicated warty lesions on her buttocks
molluscum contagiosum - A 7 year old boy presents with high fever,sore throat ,enlarged painful cervical lymph nodes ,strawberry tongue and a diffuse erythematous rash
Scarlet fever - GAS - A 3 year old boy presents with fever and painful vesicles in his mouth
Herpangina - Coxsackie
-A seven year old boy presents with fever and intense erythema of the cheeks followed by spread of the rash to the trunk for only one day
erythema infectiosum
A 9 month infant presents with fever and wide spread macular rash.tests were +ve for human herpes virus 6
Roseola infantum
German measles also know as rubella
Erythema infectiosum - also known as Parvovirus B19
What are other names for these infections?
German measles
Erythema infectiosum
Exanthem subitum
German measles - Rubella
Erythema infectiosum - Parvo B19/ 5th disease
Exanthem subitum - Roseola/ 6th disease
Which of the following viruses are not associated with a vesicular rash -
Rubella Virus Measles Virus Parvovirus HSV-1 VZV
Rubella Virus
Measles Virus
Parvovirus
A 19 year old man presents with flu-like illness, lymphadenopathy, fleeting
macular rash and sore throat. History of unprotected sex over last 6
months. HIV testing positive. What is the most likely diagnosis?
Acute retroviral illness
Farmer’s wife presents with dark lesion/ purple nodule on finger. What are possible causes?
Orf - pox virus
A. Dark lesion on farmer’s wife’s finger B. Umbilical lesions on boy’s face C. Lesion on fishmonger’s hand D. Hot-tub folliculitis E. Depigmentation of trunk and arms
- Malassezia furfur
- Molloscum contagiosum
- Orf
- Pseudomonas aeruginosa
- Erysipelothrix
- Staph aureus
A. Dark lesion on farmer’s wife’s finger
Orf
B. Umbilical lesions on boy’s face
Molluscum contagiosum
C. Lesion on fishmonger’s hand
Erysipelothrix
D. Hot-tub folliculitis
Pseudomonas
E. Depigmentation of trunk and arms
Malassezi furfur
- Clostridium tetani
- Corynebacterium diphtheriae
- Clostridium botulinum
- Staph aureus
- Clostridium perfringens
- Vibrio cholera
- Produces elastase
- Produces Lecithinase
- Toxin production induces flaccid paralysis
- Produces elastase
Staph aureus - Produces Lecithinase
Clostridium perfringens - Toxin production induces flaccid paralysis
Clostridium botulinium
Toxins
A. Shiga toxin B. SPE-C C. Diptheria toxin D. Cholera toxin E. Alpha toxin of Clostridium perfringes F. Tetanus toxin G. Endotoxin H. Botulinum toxin
- Its lipid component induces fever and shock by inducing TNF
- Blocks release of acetylcholine
- It inhibits protein synthesis by ADP-ribosylation of elongation factor 2
- It increases cyclic AMP by ADP-ribosylation of G protein
- Its lipid component induces fever and shock by inducing TNF
Endotoxin - Lipid A - Blocks release of acetylcholine
Botulinum toxin - It inhibits protein synthesis by ADP-ribosylation of elongation factor 2
Diptheria toxin - It increases cyclic AMP by ADP-ribosylation of G protein
Cholera toxin?
A. Shiga toxin B. SPE-C C. Diptheria toxin D. Cholera toxin E. Alpha toxin of Clostridium perfringens F. Tetanus toxin G. Endotoxin H. Botulinum toxin
- Action is via phospholipase C hydrolysis of phosphorylcholine in cell membrane
- Inactivates protein synthesis by degrading 28s rRNA
- Superantigen which binds directly to MHC II, and interacts with -chain of TCR to release cytokine cascade
- A-B subunit toxin binds ganglioside receptors to interfere with synaptic transmission
- Action is via phospholipase C hydrolysis of phosphorylcholine in cell membrane
Alpha toxin of Clostridium perfringens - Inactivates protein synthesis by degrading 28s rRNA
Shiga toxin - Superantigen which binds directly to MHC II, and
interacts with -chain of TCR to release cytokine cascade
SPE-C - Streptococcal Pyrogenic Exotoxin C is a super-antigen with wide cross-reactivity - A-B subunit toxin binds ganglioside receptors to interfere with synaptic transmission
Tetanus toxin
What are examples of polyoma viruses?
BK
JC
SV40
Match the bacteria and their toxins
a-adenylate cyclase b-shiga like toxin c-cholera toxin d-oedema factor e-heat stable and heat labile toxin f-pyrogenic exotoxin
E coli O157 pertussis ETEC Streptococcus pyogenes Bacillus anthracis
E coli O157
shiga like toxin
pertussis
adenylate cyclase
ETEC
heat stable and heat labile toxin
Streptococcus pyogenes
pyrogenic exotoxin - SPE
Bacillus anthracis
oedema factor
i. Presence of P fimbriae
ii. Presence of type 4 pili
iii. Stimulation of T lymphocytes
iv. Inhibits formation of phagolysosome
v. Inhibition of acetylcholine receptors
vi. Presynaptic inhibition of GABA receptors
A. Cystitis B. Toxic shock syndrome C. Tetanus D. Botulism E. Meningococcal carriage F. M TB
A. Cystitis
P fimbriae - E. coli
B. Toxic shock syndrome
Stimulation of T lymphocytes
C. Tetanus
Presynaptic inhibition of GABA receptors
D. Botulism
Inhibition of acetylcholine receptors
E. Meningococcal carriage
Type 4 pili - assumed to play a key role in the initial adherence to human epithelial cells by virtue of the associated adhesin protein PilC
F. M TB
Inhibition of phagolysosome
Toxins
A. Increase in cAMP leading to fluid loss
B. Includes lethal factor, oedema factor and protective antigen
C. Elongation factor 2
D. Produces neurotoxin that leads to spastic paralysis
E. Produces neurotoxin that leads to flaccid paralysis
- C. diphtheria
- C. botulinum
- V. cholera
- C. tetani
- B. anthracis
- B. pertussis
- S.aureus
A. Increase in cAMP leading to fluid loss
V cholera
B. Includes lethal factor, oedema factor and protective antigen
B anthracis
C. Elongation factor 2
C diptheria
D. Produces neurotoxin that leads to spastic paralysis
C tetani
E. Produces neurotoxin that leads to flaccid paralysis
C botulinum
What is the most important component of endotoxin leading to septic shock?
Lipid A
Classifying streptococci
What are examples of alpha haemolytic streptococci?
How to differentiate them?
Strep pneumo - optochin S
Strep viridans - optochin R
Strep viridans group is wide group of bacteria, which live in oral cavity.
Can cause IE/ neonatal sepsis/ gingivitis
What are examples?
Strep milleri/ anginosus – abscesses brain/ liver/ GI
S sanguinis
S mutans
S mitis
Classifying streptococci
beta haemolytic streptococci classified by Lancefield groups A/B/C/E, depending on carbohydrate expressed
GAS and GBS are two of most important streptococci.
GPC in chains seen on agar. How to rule out these two pathogens?
Latex agglutination of Lancefield groupings
Strep pyogenes - bacitracin S, PYR pos
Strep agalactiae - bacitracin R, PYR neg, CAMP pos, Hippurate hydrolysis pos
What are GAS virulence factors?
GAS virulence factors M protein Lipoteichoic acid Hyaluronic acid Streptolysins Streptodrnase. DNA
What are examples of gamma haemolytic streptococci?
They cause UTI/ GI/ biliary/ IE infection
enterococci - AKA group D strep
Strep bovis (gallolyticus)
GPC in chains seen on blood agar. Gamma haemolytic. How to distinguish between these organisms?
enterococci - AKA group D strep Strep bovis (gallolyticus)
Bile esculin positive.
Bile esculin agar contains oxgall (bile salts) to inhibit the growth of gram positive organisms other than enterococci and group D streptococci- confirms gamma haemolysis
Enterococci - PYR pos
Strep bovis - PYR neg
What are uses for Hippurate hydrolysis test?
Tests for -
GBS
Campylobacter jejuni (coli is neg)
Baby with early onset sepsis. Suspect GBS
What is treatment?
Benzylpenicillin 7 days
Lumbar puncture - if meningitis
Benzylpenicillin 14 days, gentamicin 5 days
48 AML 15 day chemo via Hickman line. Treated Taz + gent.
Blood cultures grow GPC in long chains – alpha strep, optochin R
What is possible causative organism?
Does treatment need changed?
S viridans group – Strep oralis/ mitis
Add vancomycin
Source - either oral (mucositis) or line related
Blood cultures from line/ consider remove line
TTE
48 trauma patient – base of skull fracture/ SAH/ IVH.
Blood culture GPC in pairs and chains
What are possible causative organisms
Alpha strep - Strep pneumoniae causing meningitis
Gamma strep - Enterococcus
Blood culture seems more likely to be streptococci than staphylocci. Possible other causes -
Staph aureus
Staph epidermidis
