Microbiology

Question 1

HDV

Answer 1

Smallest virus - more plant viroid than human virus
Only seen with HBV co-infection
Requires HBV surface proteins for it’s cycle
Superinfection in chronic HBV
Rx: IFalpha, Farnesyl-transferase inhibitors (cannot assemble virion), lonafarnib (no multiply)

Question 2

HEV

Answer 2

Self-limited, complications for immunocompromised and pregnant
Many genotypes
1 and 2 in epidemic areas, epidemic outbreaks- floods, water contamination
3 and 4 low endemicity, pigs
Rx: ribavarin and peginterferon

Question 3

HBV

Answer 3

Perinatal, percutaneous, STI
Non-curable (unless spontaneous resolution)
CD4+ and CD8+ liver injury, low in chronic
IgM early infection
High HBeAg - high virus lvls
HBsAb - recovery from natural infection or vaccine
HBeAb - seroconversion (stable low level load) if HBsAg not achieved
Anti-HBc - may have resolved or chronic, achieved after HBeAb seroconversion
ALT rises with immune clearance (T cell mediated immunity)
Chronic >6months

Question 4

HCV

Answer 4

Main indicator for liver transplant
Highly prolific
20% SRV
Can spontaneously resolve (jaundice, young, female)
6 major genotypes (depend on E1, NS5B( lacks proof reading)regions)
US 1
EU 1, 3
4-6 high prevalence areas
SVR after peginterferon/ribavirin low in 1, high in 2/3
Type 3 high degree of stearosis
DAAs not as mono-therapies, at least with ribavirin

Question 5

Osteomyelitis

Answer 5

Haematogenous; children after bacteraemia, metaphyseal
Contiguous; after trauma, surgery, or soft tissue infection
Direct; any age, any bone
Diabetic; foot ulcers and all the things diabetics have, hard to treat, amputation
Periosteal thickening and elevation + lysis and sclerosis
S. Aureus (adhesins), group B strep in children

Question 6

Septic arthritis

Answer 6

S. Aureus + Strep spp (flucloxacillin + rimfapacin for staph) + (benzyl penicillin or cefuroxime for strep)
H. Influenzae if <3
N. Gonorrhoea in young adults
G negative in IVDUs; pseudomonas
2-3wks Abx

Question 7

Prosthetic joint

Answer 7

Epidermal flora eg S. Epidermis, S. Aureus
Bio-film
Surgical drainage + 6wks Abx
Replace joint
1 or 2 stage

Question 8

Infective endocarditis

Answer 8

Native valve IE; congenital problems, rheumatic, dgenerative, usually strep viridans
Prosthetic valve IE; coag -ve staph
IVDU IE; staph aureus
Nosocomial
HACEK
Q fever (coxiella burnetti): culture negative, Rx: tetra, hydroxychloroquine (year therapy)
Strep 60-80%, staph 20-35%

Question 9

Foodborne illness

Answer 9

Salmonella/shigella
Campylobacter
E. Coli 0157
Listeria monocytogenes
Clostridium perfringens

Question 10

Mandatory surveillance

Answer 10

MRSA
C. Diff
GRE
E. Coli/ klebsiella/ pseudomonas
Surgical site infection

Question 11

Trachoma

Answer 11

Chlamydia trachomatis (serovars A-C)
Most common cause of preventable blondness worldwide
1st infection by 2yrs
Hand to eye and flies transmission
Prevention: clean water, decrease fly population
Rx: erythromycin or doxycycline, eyelid surgery
WHO: S.A.F.E 2020 elimination

Question 12

Pneumococcal Vaccination

Answer 12

Children <2yrs (vaccination programme) PCV
13 capsular types
Adults over 65 PPC
2-64 high risk adults
23 types (covers 65%)

Question 13

Respiratory syncytial virus

Answer 13

Passive immunisation
RSV directed antibodies (Palivizumab)
Preterm infants w/ chronic ling disease, acyanotic heart disease
Consider in: SCID <2yrs, long-term vent <1yr/ <2 w/ +pathology

Question 14

Bexsero

Answer 14

Menigiococcal B vaccine
Efficacy not stablished
Vaccination of children/adults w/ asplenia, lab workers that work with organism or in outbreaks

Question 15

Neutropenic sepsis

Answer 15

Neutrophil count 0.5 and lower
Either T >38 or signs/symptoms of sepsis
E.coli, pseudomonas (voriconazole), alpha-haemolytic strep, anaerobes, coag -ve staph
Other: candida (aerodigestive tract), LRTI - pseudomonas, skin - pseudo, candida, fusarium
Mucomycosis: rhinocerebral (Rx: debridement and antifungal)
Rx: anti pseudo;piperacillin/tazobactam, imipenem, meropenem, ceftazadine
Combined: anti-pseudo + gentamycin
Prevention: cipro, G-CSF, infection control

Question 16

T-cell and cell-mediated immunity

Answer 16

B cell can also be compromised
Pneumonitis jirovecii: fungus, immunofluorescent staining, high-dose co-trimoxazole
Cryptococcus neoformans: yeast, can lead to meningitis, CSF micro (India ink), Rx; amphotericin + flucytosine then fluconazole
Herpesvirus: active/passive immunisation, prophylactic antivirals
Revention: co-trimoxazole, aciclovir, antifungals

Question 17

B cell and humoral immunity

Answer 17

Acquired: CLL, MM, anti-cancer Rx, hypo/asplenism
Some congenital
Encapsulated bacteria: S. Pneumoniae, N. Meningitidis, HIb
Capnophaga canimorsus
Parasites: babesia, plasmodium
Active immunisation
Prophylaxis: penicillin, or macrolide
Ig replacement

Question 18

HIV

Answer 18

HIV is a retrovirus
Infects CD4 T lympocytes
Kills immune cells and disturbs function of the immune system-key role of CD4 cells
AIDS is the result of T lymphocyte defect
Treatment is targeted at the replicative cycle, can now reverse soke of the immune defects
T cells: >500 normal, 200-500 asymptomatic, <200 AIDS, <50 risk of death in 12months

Question 19

Malaria

Answer 19

Protozoan infection (plasmodium vivax, falciparum, ovale, malariae)
Incubation period: 7-30d, vivax up to a year, vivax/ovale hypnozoites
Presentation: flu-like symptoms, resp symptoms, GI symptoms, CNS symptoms, shock, acidosis, DIC, hypoglycaemia, splenic rupture
Ix: blood film, antigen test, clotting screen, blood cultures, pH, serology
Rx: quinine, doxycycline, fansidar, primaquine, supportive, avoid overhydration, exchange transfusion
Prevention;protection against bites, protection from infection, prevent parasite life cycle

Question 20

Other protozoa

Answer 20

Leishmaniasis: visceral (heparosplenomegaly), cutaneous (topical sores), Sandflies, Dx: biopsy, Rx: antimonials, pentamidine, ampotericin, prevention: bed nets, dog control
Trypanosomiasis; tsetse fly, sleeping sickness, africa
Chaga’s; rejuvid, megaoesophagus, megacolon, cardiomyopathy, Rx: arsenicals

Question 21

Scistosomiasis

Answer 21

Trematode
Presentation:
None - swam in lake malawi
Swimmer’s itch
Katayama fever; fever, arthralgia, urticarial rash
Haematuria
Malignancy
Paraparesis
Dx: ova in urine and stool or biopsy, oesinophilia
Rx: praziquantel