Past papers 5 Flashcards
Ventriculitis secondary to a CNS prosthesis. Which drug which will be a useful adjunct in treatment?
clindamycin gentamicin erythromycin moxifloxacin rifampicin
intrathecal gentamicin?
Rifampicin also useful for prosthesis and biofilms
Person goes surfing, develops wound infection and sepsis, GNB isolated from wound
Mycobacteriym marinum
Vibrio vulnificus
pseudomonas
Vibrio vulnificus
Patient presents with iron deficiency anaemia.
Stool OCP shows 300micron size thin shelled eggs in faeces
What is the cause?
roundworm trichuris strongyloides enterobius ancylostoma
anyclostoma - hookworm
What infections is Acanthamoeba associated with?
Contact lens kerratitis
Scaly rash with skin depigmentation, microscopy shows yeasts and small hyphae
Trichophyton
Microsporum
candida
M. furfur
malassezia furfur - pityriasis versicolor
Child with NSI from a needle lying in a park frequented by IVDUs. What is course of action
accelerated course of Hep B vaccine send needle for HBV testing give PEP for HIV HBIG Do nothing
Do nothing - according to new guidelines
Child with enlarged axillary LNs,recently given kittens as gift. What is most likely cause?
Bartonella hensleae
Bartonella quintana causes trench fever
Bartonella bacilliformis - oroya fever
Mother gives birth to a child with microcephaly. Has 3 cats. What is most likely cause?
Toxoplasma
Pregnant lady in contact with a child with rubella. Course of action:
Check childs Rubella IgG check childs rubella IgM check mums rubella IgG check mums rubella IgM give immunoglobulin
Check mums rubella IgG + take history for MMR
If mum immune, then that is end of investigation
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 - infections after 20 weeks
There is a well known single step mutation leading to a high level resistance with loss of catalase activity.
Choose right combination:
MTB - izoniazid
S.aureus - cipro
Gp A strep - erythromycin
Pseudomonas- Imipenem
MTB- isoniazid
What is Vincent’s angina?
acute necrotising ulcerating gingivitis - sloughing of gums
Usually poor dentition, or immunocompromised
Diptheria or normal flora can be causes
Link the chemicals/ enzyme/ growth with the organism?
A. Black pigment
B. Phenylalanine deaminase
C. Growth in 6.5% NaCl
D. Lecithinase (α-toxin)
Clostridium perfringenes Streptococcus pneumoniae Proteus species Streptococcus agalctiae Saphylococcus aureus Enterococcus Bacteroides melanogenicus (also known as prevotella melaninogenica)
Black pigment - bacteroides melanogenicus/ prevotella. Normal upper respiratory tract flora. Grow on blood agar forming dark black colonies, which darken over a few weeks
Proteus - phenylalanine deaminase. Test used to see if organism has this enzyme, which removes amine group from phenyalanine, producing green colour. This helps identify Proteus, Morganella, Providencia
Staphylococcus aureus - can grow in 6.5%NaCal
Clostridium perfringens - lecinthinase alpha-toxin. Type A strains produce toxin which causes gas gangrene. Which is a life-threatening infection with fever, pain, edema, myonecrosis and gas production.
1. Clinical presentation A. Rose spots B. Risus sardonicus C. Black eschar D. Asymmetrical paralysis E. Descending symmetrical paralysis
Options:
i. Lymes disease
ii. Typhoid
iii. Anthrax
iv. Tetanus
v. Botulism
vi. Polio
vii. Rabies
Options:
i. Lymes disease
ii. Typhoid = A
iii. Anthrax = C
iv. Tetanus = B
v. Botulism = E
vi. Polio = D
vii. Rabies = symmetrical ascending paralysis
Mode of transmission
A. Shigella enteritis B. Listeria meningitis C. CMV pneumonitis D. Crptosporidial diarrhoea E. Lymes disease
i. Drinking contaminated water
ii. Faeco-oral route
iii. Vertical transmission
iv. Sexual contact
v. Spread by health care workers
vi. Swimming in contaminated water
vii. Endogenous infection
viii. Air borne spread
ix. Tick bite
A. Shigella enteritis - faecal-oral
B. Listeria meningitis - vertical?
C. CMV pneumonitis - sexual contact? Endogenous infection?
D. Cryptosporidial diarrhoea -drinking contaminated water
E. Lymes disease - tick bite
1Infection control
A. Known MDRTB B. Leukemia patient on chemotherapy with persistent neutropenia C. MRSA patients in a ward D. Case of Dengue haemorrhagic fever E. Child with calicivirus infection
i. Cohort nursing
ii. Negative pressure room
iii. Positive pressure room
iv. No special precautions needed
v. Universal infection control precautions
vi. Enteric precautions
vii. Transfer to ID hospital with category 4 facilities
viii. Isolate in side room
A. Known MDRTB - negative pressure room
B. Leukemia patient on chemotherapy with persistent neutropenia - positive pressure room
C. MRSA patients in a ward - cohort nursing
D. Case of Dengue haemorrhagic fever - transfer to ID hospital with category
E. Child with calicivirus infection - isolated in side room. Virus usually causes gastroenteritis, which is normally self-limiting
- Virus morphology
A. Enveloped, icosahedral DNA virus, grows in many cell lines
B. Non enveloped positive sense RNA virus, grows easily
C. Slow growing DNA virus in fibroblast cell lines, narrow host range
D. Small DNA virus, grows in Cells in S phase
E. Enveloped icosahedral ssRNA virus, not much CPE
Options
i. Rubella
ii. CMV
iii. Influenza
iv. Polio
v. HHV-6
vi. HSV
vii. VZV
viii. Parvovirus
i. Rubella = E
ii. CMV (dsDNA) = C
iii. Influenza = negative-sense ssRNA
iv. Polio = B
v. HHV-6
vi. HSV = A
vii. VZV = C?
viii. Parvovirus = D
Virus morphology
A. Enveloped, icosahedral DNA virus, grows in many cell lines
B. Non enveloped positive sense RNA virus, grows easily
C. Slow growing DNA virus in fibroblast cell lines, narrow host range
D. Small DNA virus, grows in Cells in S phase
E. Enveloped icosahedral ssRNA virus, not much CPE
i. Rubella
ii. CMV
iii. Influenza
iv. Polio
v. HHV-6
vi. HSV
vii. VZV
viii. Parvovirus
A. Enveloped, icosahedral DNA virus, grows in many cell lines - HSV
B. Non enveloped positive sense RNA virus, grows easily - polio
C. Slow growing DNA virus in fibroblast cell lines, narrow host range - CMV
D. Small DNA virus, grows in Cells in S phase - parvovirus
E. Enveloped icosahedral ssRNA virus, not much CPE - rubella
Bacterial infections and antibiotics
A. Brucellosis
B. Child with cellulitis with pseudomonas in wound swabs
C. Osteomyelitis with Klebsiella following RTA
D. Hepatitis C
E. Influenza B
i. Piperacillin/ tazobactam with an aminoglycoside
ii. Flucloxacillin
iii. Ciprofloxacin
iv. Amantadine
v. Lamuvidine
vi. Interferon & ribavirin
vii. Doxycycline + rifampicin
viii. Oseltamivir
A. Brucellosis - doxycycline and rifampicin
B. Child with cellulitis with pseudomonas in wound swabs - tazocin and aminoglycoside
C. Osteomyelitis with Klebsiella following RTA - ciprofloxacin
D. Hepatitis C - interferon and ribavirin
E. Influenza B - oseltamivir
Four neonates in intensive care colonised with Pseudomonas aeruginosa over 4 month period, with clear evidence of co-location.
What is optimal method for typic P. aeruginosa to investigate a possible outbreak?
Antimicrobial susceptibility patterns Pyocin typing Pulsed-field gel electrophoresis Whole genome sequencing Variable nucelotide tandem repeat
Whole genome sequencing
Cases separated a lot by time, so will be most useful, although time consuming
Four patients on surgical ward are diagnosed with healthcare associated MRSA wound infections in a week.
What is most useful investigation to determine similarity of these isolates?
Phage typing with international consenss phages
Multilocus sequence typing (MLST)
Bacterial antibiotic susceptibility profiles
Capsular antigen typing
Ribosomal 16S sequencing
Multilocus sequence typing (MLST)
Phage and antibiotic susceptibility profiles are difficult to have consistent reproducible results
18 year old woman has mid-stream urine sent to the lab.
Which statement is correct?
- unpreserved urine should be processed in <4 hours from collection time
- Preservatives such as iodine stabilise bacterial counts for 24-72 hours from collection
- Suprapubic aspirate should be obtained
- First void urine of the day should be collected
- Pure growth of an organism in a mid0strema urine is indicative of a pathogen-
- unpreserved urine should be processed in <4 hours from collection time
- early morning urine only useful for investigation of renal TB
- boric acid and tartaric acid are useful preservatives which stunt bacterial growth, and prevent bacterial overgrowth which may lead to false-positive result
What is role of leukocyte esterase in diagnosing urinary tract infections?
Leukocyte esterase present in neutrophils/ macrophages - released when cells are damaged or lysed.
Leucocyte esterase test more sensitive than nitrate test.
75-96% sensitivity, 94-98% specificity
- Prone to false positives from vaginal secretions, trichomonal infections or high blood WCC
- Prone to false negatives - neutropenic patients
Combine with nitrate test to increase specificity and sensitivity
When should asymptomatic bacteriuria be treated?
- if pregnant. Women screened in first trimester
- if >10power5 organisms on two consecutive mid-stream samples
Treating asymptomatic bacteriuria in patients with diabetes, older persons, patients with catheters, and patients with spinal cord injuries does not improve outcomes.
What is role of nitrate test when diagnosing UTI?
- detects presence of nitrate reductase
- sensitivity 30-80%, specificity 92-100%
- produced by most gram neg Enterobacteriales
Which organisms can cause UTI, but have negative nitrate reductase test?
Do not have enzyme to reduce ntirate
Staph aureus
Enterococcus (Group D Strep)
Acinetobacter
What culture medium is most appropriate for isolating Haemophilus influenzae?
Blood agar Chocolate bacitracin agar MacConkey agar Mannitol salt agar XLD
Chocolate bacitracin agar
Bacitracin inhibits growth of staph/ strep/ micrococcus/ Neisseria which can be common commensals of upper respiratory tract, and may overgrow any Haemophilus present
- blood - non-selective so many things will grow
- MacConkey - selects for gram negs based on their ability to ferment lactose
- Mannitol salt - selects gram pos such as Staph/ micrococcus
- XLD - selective for Salmonella (red) and shigella (yellow)
Blood culture from 7 year old haematology patients grows:
gram pos cocci
catalase pos
coagulase neg
Resistant to teicoplanin
What is identity?
S aureus S haemolyticus S intermedius S lugdunesis S epidermidis
S haemolyticus - has unusual resistant phenotype. Often resistant to meticillin, gentamicin, erythromycin, and rarely glycopeptides such as teicoplanin.
S aureus is coagulase pos
In screening for ESBLE Enterobacteriales which antimicobial disc can be used?
Cefpodoxime Cefotaxime Ceftazidime Cefalexin Cefoxitin
Cefpodoxime - all ESBLs are resistant to this antibiotic
- ## Cefoxitin is screening antibiotic for AmpC production
Which of the following bacteria is latex agglutination test not commonly used?
Staph aureus Strep pyogenes Shigella sonnei Pseudomonas aeruginosa Salomenlla Typhi
Pseudomonas
- Staph aureus - catalase/ coagulase tests
- Step pyogenes - Lancefield grouping
- Shigella/ Salmonella Typhi - Vi antigen
36 year old with ruptured dental abscess. Swab of pus sent. Which of following antimicrobials is commonly used to make selective media for anaerobes?
Colistin Neomycin Chloramphenicol Vancomycin Metronidazole
Neomycin
- provides selective media by inhibiting most faculative anaerobes
36 year old with ruptured dental abscess. Swab of pus sent. Which of following antimicrobials is commonly used to make selective media for anaerobes?
Colistin Neomycin Chloramphenicol Vancomycin Metronidazole
Neomycin
- provides selective media by inhibiting most faculative anaerobes
Patient with painless ulcer on penis. Syphilis serology negative
Strongly suspect syphilis is the cause
What is explanation?
Prozone effect
Effect whereby either very high antibody or antigen titres do not agglutinate because of either high excess of antibody or antigen
Serum needs to be diluted serially to enable agglutination reaction to occur
23 year old presents with fever of unknown origin
Blood culture is oxidase positive
Does not grow without blood
Can ferment glucose but not maltose
What is likely diagnosis?
Neisseria sica Neisseria meningitidis Neisseria gonorrhoeae Moraxella catarrhalis Acinetobacter spp
Neisseria gonorrhoeae - disseminated infection can cause meningitis, endocarditis, arthritis
N gonorrhoea - glucose + , maltose -
N meningitidis - glucose + , maltose +
M cattarhalis - glucose - , maltose -
17 year old with fever and oral pain.
Swab sent for MC&S
A diagnosis can be made based solely on gram stain morphology of which infection?
Diptheria Arcanobacterium haemolyticum Vincent's angina Group A strep Actinomycosis
Vincent’s angina - due to anaerobes such as Bacteroides, Fusobacterium, as well as overpopulation of commensals such as Spirochaetes and Borrelia
Known as trench mouth. Due to poor diet, poor oral hygiene, stress. Ulceration and sloughing of dead tissue in mouth
Ludwig’s angina is infection of floor of mouth
Gram stain shows slender rods which are pointed at ends
What is cause of Job syndrome immunodeficiency?
How might it present?
Jobs syndrome - hyper-IgE syndrome with defective T-cells/ neutrophils.
Presents childhood atopic dermatitis with recurrent Staph aureus skin infections
