Microbiology Flashcards

Question

Chlamydophila spp. (chlamydia pneumonia/psittaci)

Answer 1

**bacteria:** obligate intracellular parasite **disease:** atypical chlamydia pneumonia **treatment**: doxycycline

Answer 2

**cover:** good positive/negative **adverse:** grey baby syndrome (hepatic met), aplastic anaemia, BM hypoplasia

Answer 3

**bacteria:** gram positive rod spore forming **botulinum:** blocks ACh release causing flaccid paralysis\ - treatment: toxin Ig **tetani:** prevents release glycine/GABA (inhibits inhibitor) causing excessive muscle contraction - treatment: anti-tetanospasmim Ig **perfringens** (only non-motile): alpha toxin myonecrosis **difficile:** nosocomial diarrhoea due to antibiotics, exotoxin A (enterotoxin) + B (cytotoxin), pseudomembranous colitis **- treatment:** metronidazole, vancomycin

Answer 4

**risks:** transplant from CMV +ve donor to -ve recipitent, decreased T cell function **clinical:** - renal transplant: graft loss - liver transplant: hepatitis/colitis - lung/BMT: pneumonitis - cardiac: early myocarditis/late atherosclerosis - HIV: retininits/colitis/encephalitis **treatment:** 2 weeks ganciclovir, then 6 months PO valganciclovir

Answer 5

**congenital (rare):** skin vesicles, eye damage, microcephaly **postnatal 3 categories:** - skin/eye/mouth (50%): 20% neuro sequalae, no mortality - CNS disease/encephalitis (30%): 2-3 wks, meningitis, normal neuro imaging then oedema/haem/lesions - disseminated (25%): 1st week, sepsis, multiorgan (liver, lungs, adrenals, CNS, skin), 85% mortality **management:** IV aciclovir 2-3 weeks, oral supression 6/12 post

Answer 6

**virus:** coronaviridae, ss RNA **clinical:** 15% common colds - croup, asthma, LRTOs, enteritis, colitis, SARS

Answer 7

**bacteria:** gram positive rods aerobic, metachromic granules - exotoxin encoding bacteriophage **disease:** pseudomembranes in oropharynx, cervical LN, myocarditis **treatment:** erythromycin, penicillin

Answer 8

**CSF cultures:** - gram stain negative 60% meningitis - PCR for N meningitidis, S pneumo, HSV, enterovirus **CSF cytology:** - bacterial: increased neutrophils/protein, decreased glucose - viral: increased lymphocytes, normal glucose/protein - TB: elevated lymphocytes/protein, low glucose

Answer 9

**bacteria:** gram negative rods anaerobic **antigens:** K (capsule), O (outer polysaccharide), H (flagellum) **disease:** UTI gram negative sepsis, neonatal pneumonia _ETEC_: traveller's diarrhoea, LT+ST _EHEC_: 0157:H7 blood diarrhoea, HUS (fever, haem anaemia, thrombocytopaenia, acute renal failure) **- source:** uncooked hamburger meat **treatment:** bactrim, gentamicin

Answer 10

**virus:** herpesvirus (HHV 4), ds DNA **spread:** 50% positive by 5 yrs **mechanism:** establishes latency in all adults **clinical:** young usually asymptomatic - _acute:_ 1-2 wks, fever, tonsillar sx, lymphadenopathy, hepatospleenomegally (60%) _- resolution phase_: 3-4 weeks, enlarged nodes, severe fatigue **associations:** malignancy, lymphoproliferative disease, neurologic (5%), ITP 20%, neutropaenia (GBS, facial nerve palsy, meningitis, transverse myelitis, peripheral neuritis), cardiac, resp, neck abscess, morbilliform rash post pernicillin, splenic rupture **diagnosis:** low platelets, abnormal LFTs, serology/PCR, monospot (high spec, low sens)

Answer 11

**SHiNE SKiS** - **S**.pneumo, **Hi**b, **N**.meningitidis, **E**.coli, - **S**almonella, **K**lebs**i**ella, GB**S**

Answer 12

**definition:** inflammation of the brain with generalised dysfunction cerebral function +/- altered consciousness **causes:** - direct: HSV - immune: EBV, mycoplasma **treatment:** IVIg for enteroviruses, azithromycin for mycoplasma

Answer 13

**bacteria:** gram positive cocci in pairs anaerobes - eg faecalis (80% infections), faecium **disease:** 15% neonatal infections, UTI, subacute endocarditis, bacteraemia, endocarditis **resistance:** common resistance VRE **treatement:** vancomycin, linezolid, daptomycin, teicoplanin

Answer 14

**virus:** picornavirus, ss RNA, include poliovirus, coxsackie, echovirus **epidemiology:** summer/autumn, infants **transmission:** incubation 3-6 days, resp shedding 1-3 weeks, faecal shedding 7-11 weeks **clinical:** fever, malaise, rash, headache, pharyngitis, vesicular lesions buccal surfaces, fever, blisters palms/soles, vomiting diarrhoea, myositis, arthritis, orchitis _- enterovirus:_ high rates CNS/cardiopulm involvement (encephalitis, pulm oedema/haem, shock) _- enterovirus/coxsackie:_ acute haemorrhagic conjunctivitis, myocarditis/pericarditis (30% all myocarditis, usually coxsackie B, mortality \<4%) _- enterovirus/coxsackie/echovirus:_ meningitis (\>90% viral), encephalitis (10-20%, enterovirus 71), GBS, transverse myelitis, ospoclonus-myoclonus, brainstem encephalitis, acute flaccid paralysis _- coxsackie:_ RTI, pleuritic chest pain **neonatal infection:** most asymptomatic, CNS necrosis, arrythmias, CCF, MI, hepatic necrosis/failure, NEC, myositis, vomiting, diarrhoea **diagnosis:** PCR (stool/NPA/CSF)

Answer 15

**organisms:** enterobacter, serratia, citrobacter, aeromonas, proteus, morganella morghani **treatment:** carbapenem

Answer 16

**mechanism:** inhibits RNA synthesis for cell wall formation **use:** TB **side effects:** optic neuritis, do not use in young that you can't monitor vision, headache, dizziness, confusion, hyperuricaemia, peripheral neuropathy, hepatotoxicity, pancytopaenia

Answer 17

**transmission:** faecal-oral **pathophysiology:** ingestion cyst then trophozoites released and adhere to wall to revert to cysts and shed in faeces **clinical:** diarrhoea, malaise, abdo pain, weight loss, lactose intolerance (40%) **diagnosis:** stool microscopy

Answer 18

**drugs:** vancomycin, teicoplanin **mechanism:** bacteriocidal - inhibit cell wall synthesis **cover:** many gram positive, NO gram negative **adverse:** red man syndrome infusion dependant

Answer 19

**bacteria:** gram positive cocci anaerobic in chains/diplococci **transmission:** 25% pregnant women **clinical:** perinatal disease (pneumonia, meningitis, sepsis) **treatment:** benzylpenicillin + gentamicin (+ cefotaxime for meningitis\_

Answer 20

**bacteria:** small gram negative cocci-bacillus encapsulated - 6 strains have capsules - HiB most virulent **transmission:** respiratory droplets **disease:** septic arthritis, epiglottitis, meningitis, OM, pneumonia **treatment:** 3rd gen cephalosporin, gentamicin, prophylaxis rifampin

Answer 21

**bacteria:** gram negative rod **disease:** chronic gastritis, duodenal/gastric ulcers, MALT tumours, gastric adenocarcinoma **treatment:** triple therapy (PPI, amoxicillin, clarithomycin)

Answer 22

**virus:** picornaviridae **incubation**: 28 days **source:** shellfish, uncooked food **clinical**: flu like, jaundice, dark urine for 1-2 weeks **diagnosis:** increased ALT/bili, anti HepA IgM positive **treatment:** supportive

Answer 23

**diagnosis:** - HBsAg: hallmark of infection - HBcAg: Ag expressed in infected hepatocytes and not in serum - Anti-HBc: detected through course of infection - HBeAh: from precore protein and marker of replication _- acute:_ HBsAg + antiHBc IgM _- previous:_ antiHBs and antiHBc IgG _- immune_: antiHBs only _- chronic:_ HBsAg \>6months **prevention:** vaccine prevents 85%, Ig prevents 95%

Answer 24

**virus:** herpesvirus ds DNA **subtypes:** HSV1 oral, HSV2 genital **clinical:** - primary infections can be severe - recurrent infections: virus lies latent and can reactivate, less severe and shorter duration - skin vesicles and shallow ulcers on erythematous base - gingivostomatitis (kids 6m-5yrs), herpes labialis, cutaneous (herpes whitlow), genital (90% unaware of infection, urethritis, dysuria, discharge), ocular (unilater conjunctivitis with preauricular LN), CNS (HSV1 leading cause encephalitis) **diagnosis:** PCR **treatment:** - oral aciclovir \<72hrs - genital acyclovir/famcilovir, valacyclovir - CNS or immunocompromised: IV acyclovir

Answer 25

**definition:** unilateral vesicular eruption in well defined dermatomal distribution and acute neuritis **location:** thoracic/lumbar most common - zoster keratitis/opthalmicus can result from opthalmic branch trigeminal nerve **treatment:** immunocompetent: oral aciclovir 5x per day if \<72hr post sx - immunocompromised: IV aciclovir

Answer 26

**virus:** human herpes virus 6 and 7, ds DNA **incubation**: 9 days **clinical:** - 80% seropositive by 1 yr, peak 9-21 months - fever starts suddenly and lasts for 4 days - diffuse macular rash across torso starts with fever resolution - assoc cervical LN, febrile convulsion (15%), diarrhoea (70%)

Answer 27

**epidemiology:** 4 million children worldwide - 90% in Africa, 15% access to ARR **pathophysiology:** - retroviridae ss RNA Virus - HIV-1 and HIV-2 with different genetics **HIV-1 life cycle:** - attaches to cell surface molecules of CD4 cell/macrophage via CXCR-4 fusion + CCR5 - enters cell and viral RNA released into cytoplasm - viral RNA to DNA via reverse transcriptase, then to dsDNA with transcription/translation - viral RNA/proteins gather cell surface and protease cleaves viral protein so virus buds off and released into circulation

Answer 28

**3 medications HAART** (avoid resistance) - 2 NRTI + NNRTI or PI **side effects:** headache, diarrhoea, lipodystrophy, hepatitis, severe rashes, lactic acidosis, abacavir hypersensitivity syndrome - lipodystrophy syndrome: central distribution of fat, loss of peripheral fat, increased serum lipids, insulin resistance

Answer 29

**clinical:** - often not diagnosed (only 15% exposed tested) - faster disease progress - symptoms when CD4 200-300 - CNS involvement more common **treatment:** - HAART impacts on development - longer duration of treatment required **prognosis:** - without ART 20-50% die \<2yrs

Answer 30

**2 prognostic indications:** - HIV RNA viral load (strongest) - CD4 count (% in lymphocyte component of WCC) **clinical:** - common + serious (\>50%): sepsis, bacterial pneumonia - common +mild: OM, skin, soft tissue - less common: meningitis, UTI, abscess, bone/joint - opportunistic infections: PJP, atypical myobacterial (MAC), oral candidiasis, crytosporidium diarrhoea, HSV gingivostomatitis, VZV, CMV, RSV, JC virus **Systems:** - CNS: JC virus progressive multifocal leukoencephalopathy, CMV, HSV, cryptococcus, coccidiodes inmitis - resp: S.pneumonia, H.influenze, M.catarrhalis, P.aeruginosa, lymphocytic interstitial pneumonitis (unknown cause, 25-40% kinds by 2-3yrs, treat steroids) - CV S: cardiomyopathy, LVH, arrhythmias, CCF - GIT: diarrhoea, abdo pain, FTT, malabsorption, oral thrush, oral hairy leukoplakia - skin: seborrhoeic dermatitis, eczema, HSV, molluscum, warts - haem: anaemia (70%), leukopaenia (30%), thrombocytopaenia (20%) - onc: NHL, primary CNS lymphoma, leiomyosarcoma, Kaposi sarcoma HHV8

Answer 31

**transmission:** - _vertical_ (infant HIV mo): 75% not infected, 15% infected labour, 5-10% pregnancy, 5-15% breastfeeding ie. 25-40% (can be reduced to \<1% with HAART) - _horizontal:_ transfusions (90% risk, 3% paed), needlestick (0.3% risk), unprotected anal sex (3%)/vaginal sex (0.3%), mucous membrane exp (0.09%) **stages of infection:** - initially titre low but with replication reaches a threshold and viraemia occurs _1) seroconversion (2-6wks post exposure):_ flu like illness, fever, malaise, myalgia, pharyngitis, maculopapular rash _2) Asymptomatic infection OR persistent generalised lymphadenopathy_ (30%) - nodes \>1cm diameter at 2 or more extra-inguinal sites for \>3m - assoc humoral response to virus: CD8 limits infection by blocking chemoreceptors (CC5), hypergammaglobulinaemia induced, cytokine response - monocytes retain virus w/o dying act as reservoir, LN\>blood _3) AIDS-related complex_ - constitutional collection symptoms/signs: fever, night sweats, diarrhoea, weight loss, minor infections _4) AIDs_ - CD4 count\< 200x10^6 - prognosis 2yrs if untreated

Answer 32

**virus:** paramyxoviridae ss RNA **epidemiology:** most\<5yrs **clinical:** - increased severity with RSV - fever, cough, rhinorrhoea, wheeze, OM, LRTI (bronchiolitis 60%, croup 18%, asthma 14%, pneumonia 8%) - causes 10% outpatient LRTI (2nd to RSV) **diagnosis:** PCR

Answer 33

**bacterial:** strep pneumoniae, Hib, neisseria meningitidis, mycobacterium tuberculosis, borrelia burgdorferi, mycoplasma pneumoniae, bartonella henselae, listeria monocytogenes **viral:** HSV, West Nile virus, influenza, adenovirus, EBV, mumps, lymphocytic choriomeningitis virus, arboviruses

Answer 34

**bacterial:** staph aureus, Hib, mycoplasma pneumonia **viral:** adenoviruses, influenza, parvovirus, cytomegalovirus

Answer 35

**virus:** orthomyxoviridae ss RNA, H1N1 (swine flu) **incubation:** 1-7 days, highly contagious via droplets **clinical:** fever 2-3d, chills, headache, myalgia, pneumonia, GIT **complications:** bacterial infection, myositis, encephalopathy, Reye syndrome, cardiac **treatment:** amantadine, zanamivir, oseltamavir

Answer 36

**mechanism:** interupts cell wall synthesis **use:** TB **side effects:** hepatotoxicity, peripheral neuropathy

Answer 37

**bacteria:** gram negative rod with large polysaccharide capsule - 40% people carriers **disease:** bacteraemia, CAP, UTI, meningitis, nosocomial infections **4 A's:** aspiration pneumonia, lung abscesses, alcoholics, diabetics **treatment:** ceftriaxone

Answer 38

**bacteria:** gram negative rod waterborne, faculative intracellular **transmission:** aerosole droplets, no human-human **disease:** atypical pneumonia, Pontiac fever, flu-like symptoms - associated diarrhoea, vomiting, hyponatraemia, neuro (50%), hepatic dysfunction **diagnosis:** - CXR: patchy lobar consolidation - sputum culture/serology/urinary Ag **treatment:** erythromycin, fluoroquinolones

Answer 39

**definition:** septic thrombophlebitis internal jugular vein **organism:** anaerobic gram -ve rod fusobacterium necrophorum **clinical:** pharyngitis/tonsillitis to thrombophlebitis to seeding of multiple organs with septic emboli - pneumonia may lead to resp failure in untreated cases **management:** - blood culture - US jugular veins - CT chest

Answer 40

**organism:** spirochete **location:** tropical regions **source:** infects wild/domestic animals **transmission:** reservoir animals shed organism in urine **clinical:** fever, myaglias, headache, meningitis, pulmonitis, renal/liver failure

Answer 41

**drug:** clindamycin **mechanism:** bacteriostatic - inhibit protein synthesis by binding 50s subunit **cover:** staph/step **adverse:** arrhythmias, pseudomembranous colitis

Answer 42

**cover:** VRE, MRSA **adverse:** $$$, hypertension

Answer 43

**organism:** gram +ve bacilli anaerobic **source:** environment, food **clinical:** - in pregnancy crosses placenta and causes fetal infection - disease of neonate/immunocompromised: meningitis **treatment:** benzyl penicillin + gentamicin

Answer 44

**definition:** acute diffuse infection of submandibular/sublingual spaces - usually after cavity injuries or dental extraction **organism:** bacterial mixed **clinical:** induration floor of mouth/tongue - airway obstruction can occur

Answer 45

**drugs:** erythromycin, roxithromycin, azithromycin, clarithromycin **mechanism:** - bacteriostatic - inhibit translocation with ribosome 50s subunit **cover:** - +: atypicals (chlamydia, legionella, mycoplasma) - -: moraxella, gonococcus, campylobacter **adverse:** GI side effects

Answer 46

**organism:** anopheles mosquito **subtypes:** - P.falciparum: most common - P.vivax: most lethal - P.ovale: most benign **incubation:** 12-14 days **pathophysiology:** invade RBCs, digest RBC protein/Hb, prevent RBC deformation and cause haemolysis **clinical:** fever, sweats, headache, myalgia, nausea, vomiting, diarrhoea, abdominal pain, cough, anaemia, thrombocytopaenia, hepatosplenomegally, jaundice, LN **clinical children**: convulsions, coma, hypoglycaemia, met acidosis, anaemia

Answer 47

**pathophysiology:** infection extends to the air cells of the skull behind the ear inside the mastoid process **clinical:** fevers, headache, pain, tenderness, swelling to mastoid region, discharge from ear **organisms:** strep pneumo, GAS, staph aureus, strep pyogenes, moraxella catarrhalis, H.influenzae, Pseudo aeru **diagnosis:** CT facial bones **treatment:** IV AB +/- surgery

Answer 48

**virus:** paramyxoviridae ss RNA **incubation:** 7- 14 days **spread:** 90% contacts, contagious 3-5 days prior to rash **clinical the 3 c's**: 1) cough 2) corzya 3) conjunctivitis - fever, rash starts behind ears, koplik spots - respiratory sx - cardiac (myocarditis, pericarditis, ECG changes) - neuro (abnormal EEG, encephalitis .1%, 25% sequalae) - subacute sclerosing panencephalitis: 7yrs post infection in 1/100,000, progressive fatal brain damage **diagnosis:** serology, PCR, thrombocytopaenia, leukopaenia **contacts:** MMR vaccine within 72 hours - normal human immunoglobulin (NHIG): infants \<6m if mother is the contact or was \<28 weeks, all infants 6-9 months, immunocompromise, nonimmune oregnant women, exposed and no vaccine \<72hrs - if no contact tx given: exclude from school 14 days

Answer 49

**meningococcal C conjugate vaccine** - given 12 months - decreases invasive disease and carriage No vaccine available for B subtype

Answer 50

**drug:** aztreonam **adverse:** no cross-reactivity other beta lactams **cover**: NO gram positive, Ecoli, klebsiella, haemophilus, moraxella, shigella, yersinia

Answer 51

**organism:** gram negative diplococcus **clinical:** cold, sinusitis, OM **treatment:** augmentin, cephalexin, bactrim, erythromycin

Answer 52

**virus:** paramyxoviridae ss RNA **transmission:** incubation 12-25 days, spread droplets 1-2d pre and 7d post parotid swelling **clinical:** - 2 days prodrome: headache, fever, vomiting - parotitis: bilateral 70%, peaks 3 days - meningitis+/- encephalitis 10-30% - orchitis: more common post puberty - other: pancreatitis, carditis, arthritis, thyroiditis **diagnosis:** serology **prevention:** MMR vaccine

Answer 53

**epidemiology:** 1-5yrs **transmission:** eating soil **location:** submandibular LNs: preauricular/post cervical, axillary, inguinal LN **clinical**: unilateral slowly enlarging LN - firm, painless, freely movable and not erythematous - suppurate after several weeks, central fluctuation, thinning overlying skin with red/purple discolouration - rupture with sinus formation **treatment:** complete surgical excision + 6 months clarithromycin/rifabutin

Answer 54

**bacteria:** gram negative acid-fast rod, obligate intracellular pathogen **disease:** tuberculoid (reactive skin test), lepromatous disease - associated ulnar nerve injury

Answer 55

**bacteria:** gram negative acid fast rod aerobe **source:** aerosolized droplets **disease:** primary TB in upper lobes (Ghon focus: caseating necrosis/secondary calcification/fibrosis, Ghon complex: +LN), reactivation of _latent infection_ (most common) - reactivation rate 10% lifetime **treatment**: _RIPE_ therapy: rifampin, isoniazid, pyrazinamide, ethanbutol

Answer 56

**organism:** atypical gram +ve, no cell wall, self replicating **epidemiology:** school ages, 40% 3-15yrs **incubation:** 1-3 weeks **pathophysiology:** - target cell wall of ciliated resp epithelium and induce cytokines **clinical:** headache, malaise, low grade fever, cough, wheeze, rhinorrhoea, OM **extrapulmonary:** - haem: haemolysis (cold agglutinin response in 60%) 2-3 wks post, thrombocytopaenia, coagulation defects - skin: mild to severe rash (SJS) - CNS: meningoencephalitis, peripheral neuropathy, transverse myelitis, CN palsy, cerebellar ataxia, GBS **diagnosis:** - CXR: no specific, interstitial pneum lower lobes usually unilateral - bloods: low Hb, high WCC/platelets/ESR, myco serology IgM **treatment:** macrolide

Answer 57

**risks:** HepB 33%, HepC 3%, HIV 0.3% **prophylaxis:** - _HepB:_ non immunised/poor response given vaccine \<12hrs, if known +ve source then HBIG and HepB vaccine - _HepC:_ diagnostic tests with PCR immediately/4wk/12wk, Ab immediately/12wks, ALT/AST 4wks/12wks - _HIV:_ +ve source then PEP if\<72hrs, unknown is case-case

Answer 58

**organism:** gram negative diplococcus encapsulated aerobic **clinical:** urethritis, vulvovaginitis, opthalmitis, disseminated disease (cardiac, osteomyelitis) - GUT infection: 2-5 days in men, 5-10 days in women - PID: dissemination from fallopian tubes to peritoneum and live - opthalmitis: uni or bilateral, hyperacute bacterial conjunctivitis within 12 hours of innoculation, severe and sight threatening **treatment:** ceftriaxone

Answer 59

**organism:** gram negative diplococcus with polysaccharide capsule - serotypes B/C/Y cause 1/3 of cases each - B 75% and C 15% australia **epidemiology:** 1/100,000 with 50%\< 2 years - endemic with outbreaks - 2% infants and 30% adolescents carriers **clinical:** bacteramiae, sepsis, meningococcaemia, meningococcal meningitis, arthritis, pharyngitis, pneumonia - induction of coagulation pathways causing vasculitis/DIC - acute meningococcaemia: pharyngitis, myalgia, weakness, vomiting, diarrhoea, headache rash 7%, limp pain, refusal to WB, septic shock, DIC, acidosis, coma - acute meningitis: headache, photophobia, lethargy, vomiting, nuchal rigidity, seizures, focal neuro signs **complications:** skin infarctions, adrenal haemorrhage, myocarditis, deafness, erythema nodosum **treatment:** ceftriaxone, prophylaxis with rifampicin or IM ceftriaxone **prognosis:** 10% mortality highest age 15-24yrs **vaccine:** quadrivalent vaccine (A, C, Y, W135)

Answer 60

**drugs:** metronidazole, tindazole **mechanism:** bacteriocidal - metabolise to active metabolites inhibit cell wall synthesis **cover:** gram positive/negative anaeobes, anaerobic protozoa (giardia, entamoeba)

Answer 61

**organism:** gram +ve bacilli aerobic **clinical:** opportunistic infection - local or disseminated disease with suppurative infection **treatment:** bactrim

Answer 62

**clinical:** inflammation of tissues of the orbit, with proptosis, limited movement of eye, oedema of conjunctiva, inflammation and swelling or eyelids, decreased VA **pathophysiology:** direct extention or venous spread **complications:** optic nerve involvement, vision loss, cavernous sinus thrombosis, meningitis, subdural empyema, brain abscess **diagnosis:** CT to detect subperiosteal abscess or intracranial extension **treatment**: IV AB +/- drainage

Answer 63

**incidence:** 1/1000, 50% \<5yrs, M\>F 2:1 **risk factors:** sickle cell, immunodef, sepsis, trauma, indwelling device **site:** tubular bones 80%, usually rapidly growing bones - 50% tibia/fibula/femur **chronic recurrent multifocal OM** - non-bacterial, adolescents, periodic bone pain/fever, usually manidible/clavicle, XR with osteolytic lesions, treat with naproxim

Answer 64

**population:** patients with chronic haemolysis - eg. sickle cell, thalassaemia, pyruvate kinase deficiency **pathophysiology:** develop transient and absolute reticulocytopaenia induced by virus **clinical:** fever, malaise, lethargy, symptoms of profound anaemia - may have concurrent vasoocclusive pain crisis **diagnosis:** low Hb, reticulocytopaenia

Answer 65

**virus:** parvoviridiae DNA virus **transmission:** 60% adults immune **incubation**: 4-14 days, most infectious prior to rash **clinical:** - non specific prodrome: fever, malaise, lethargy - 1 week: glove/sock rash, slapped cheek, circumoral pallor - 2 week: aplastic crisis: Hb 30-40 **pregnancy:** reduced RBC production causing hydrops fetalis **diagnosis:** clinical, IgM **treatment:** IVIg only if aplasia **rare associations:** arthritis, neuro, myocarditis, cutaneous, haem, AI, hydrops fetalis in pregnancy

Answer 66

**drugs:** _narrow spectrum (beta lactamase sensitive):_ penicillin - all strep, staph saprophyticus, enterococcus, meningococcus _penicillin with beta lactamase inhibitors:_ augmentin, timentin, tazocin - all gram positive, most gram negative NOT pseudomonas, meningococcus _anti-staph peniciilins:_ flucloxacillin, dicloxacillin, methacillin - staph, strep pyogenes only _moderate spectrum:_ amoxicillin, ampicillin - strep, staph saprophyticus, enterococcus, listeria, E.coli, haemophillus, meningococcus _broad spectrum:_ piperacillin, ticarcillin - strep, staph saprophyticus, enterococcus, listeria, most gram negative **use:** gram positive infections (primarily strep), beta lactamase resistant can be used for staph. but not MRSA **mechanism:** block bacterial peptidoglycan cell wall formation - beta lactam ring resembles D-ala D-ala portion of wall so inserts and prevents normal cell wall synthesis - beta lactamases open beta lactam ring **metabolism:** liver **excretion:** kidneys **side effects:** rash, hypersensitivity

Answer 67

**organism:** fungus pneumocystis jiroveci **incidence:** peak 3-6m with neonatal HIV, mortality \<1yr **clinical:** fever, tachypnoea, SOB, hypoxemia **CXR:** diffuse bilat interstitial infiltrate/diffuse alveolar disease **diagnosis:** methylene blue fungal stain (fungal components turn black), immunofluorescent staining **treatment:** bactrim

Answer 68

**components:** 7 serotypes: 80% that cause disease - mutant diptheria toxin as carrier protein/aluminium phosph **administration:** 2/4/6 months **protection:** \>95% protection against invasive disease by those strains - \>85% protein all strains **clinical:** - decreased OM, pneumo, carriage, AB use **adverse:** local reaction 10% \*\* conjugated vaccine effective \<2yrs

Answer 69

**virus:** picornaviridae ss RNA **aetiology:** Asia, Africa **mechanism:** affects anterior horn cells **clinical:** - 95% asymptomatic - 5% abortive poliomyelitis (flulike) - 1% non paralytic polio (flu like, transient bladder/bowel dysfunction, nuchal rigidity) - 0.1% paralytic polio: spinal muscle (asym flaccid paralysis), bulbar (CN and medullary disease), polioencephalitis (seizures, coma, spastic paralysis), paralytic with resp insufficiency **diagnosis:** virus in stool **management:** supportive

Answer 70

**viruses:** BK and JC ds DNA viruses **transmission:** oral/respiratory **risk factors:** immunocompromised hosts **clinical:** _BK virus:_ - renal transplants, renal tubulointerstitial nephritis, rarely ureteral stenosis - BMT: haemorrhagic/nonhaeorrhagic cystitis - also vasculopathy, meningoencephalopathy, retinitis, pneumonitis, hepatitis, SLE, GBS **diagnosis:** BKV IgG, urine electron microscopy (cast like polyomavirus aggregates)

Answer 71

**bacteria:** _motile_, gram negative rod aerobic **source:** pool, hot tub **clinical:** opportunistic pathogen, burn patients, CF, DM, shunts, catheters - erythema gangrenosum, septisaemia **treatment:** ceftazidime/cefepime, tazocin, timentin, ticarcillin, carbenicillin, piperacillin

Answer 72

**mechanism:** bactericidal **use:** TB **side effects:** GI upset, hepatotoxicity (4%), hyperuricaemia

Answer 73

**drugs:** ciprofloxacin, norfloxacin, moxifloxacin **mechanism:** bacteriocidal - inhibit DNA gyrase, DNA not supercoiled, death **penetrance:** IV=oral **cover:** NO +, - rods/cocci/pseudomonas/mycobacteria **adverse:** ciprofloxacin (skin sensitivity, tendinopathy, CNS stimulation)

Answer 74

**definition:** bulging abscess caused by displacement of uvula **etiology:** school aged/adolescents **clinical:** trismus (spasm masseter muscles), "hot potato" voice, spasm of internal pterygoid that elevates the palate

Answer 75

**epidemiology:** 1-6yos **mechanism:** small LN disappear post 5 yrs **diagnosis:** lateral neck XR with measurement of prevertebral space that exceeds x2 diameter of C2 suggest abscess or pockets in air

Answer 76

**epidemiology:** \<4yrs, M\>F **clinical:** fever, irritability, decreased intake, drooling, neck stiffness, torticollis, refusal to move neck, muffled voice, stridor, resp distress **organism:** GAS, staph aureus, Hib, klebsiella, MAIC **diagnosis:** - lateral neck XR: paravertebral space increased in depth compared to AP measurement of adjacent vertebrae, soft tissue mass, air/fluid level **treatment:** IV AB +/- drainage

Answer 77

**organism:** streptococcus pyogenes **incidence:** 3% untreated strep infections, age 5 to 14 years **risk factors:** malnutrition/poverty **pathophysiology:** - type II hypersensitivity reaction - strep Ab react to myocardium/joints **clinical:** - symptoms 2-4 weeks post throat infection 2 major OR 1 major + 2 minor **_- major manifestations (5): 'JONES'_** * **J**oints (70%): early, migratory polyarthritis large joints * **O**bvious carditis (50%): MS, mumur MR/AR, pericarditis/pericardial effusion, cardiomegally/CCF * **N**odules (\<1%): hard painless nodules extensor surfaces, assoc carditis * **E**rythema marginatum (\<3%): purple annular lesions LL/torso, disappear in cold * **S**ydenham chorea (15%): neuro/pysch, latent period to 8mths after other symptoms, initial emotional lability 1-4wks then chorea/motor weakness, increased antineuronal Ab - **_minor manifestations '_cr**_ITERIA_**': I**nflammatory cells, **T**emp, **E**levated ESR/CRP, **R**aised PR, **I**tself (hx), **A**rthralgia **diagnosis:** - positive ASO, antiDNase B titres, elevated CRP/ESR, prolonged PR interval **treatment:** 10 day treatment - IM ben pen every 3-4 weeks for a minimum of 10 years

Answer 78

**virus:** ssRNA **clinical:** most common cause 'common cold' - less common fever, OM

Answer 79

**drug:** rifamycin antibiotic **mechanism:** inhibits RNA polymerase **indication:** TB **side effects:** transient increase LFTs, GI upset, headache, dizziness, flulike, thrombocytopaenia, anaemia, orange tears/saliva/stools, induced CYP 450

Answer 80

**virus:** paramyxoviridae ss RNA **incubation:** 4-6 days, shed virus for 1-2 wks post infection **epidemiology:** M\>F, peak 2-5months, nearly ALL 2yo infected clinical: rhinorrhoea, cough, desaturation, apnoea\*\*, bronchiolitis (40-70%), viral pneumonia **management:** supportive, 1% infected hospitalised **prevention:** palivizumab RSV Ig (reduced risk recurrent wheeze in exprems), monthly IM during RSV season for \<2yrs with CLD/home O2/CHD **diagnosis:** NPA PCR

Answer 81

**virus:** rubella virus ssRNA **incubation:** 14-21 days **clinical:** - prodrome: fever, malaise, headache, conjunctivitis, eye pain - cervical LN - forchheimer sign: pinpoint petechiae on soft palate - rash to face spreads to rest of body **diagnosis:** serology

Answer 82

**bacteria:** gram negative motile rods aerobic **transmission:** contaminated food/water eg. eggs, poultry, reptiles **clinical:** gastroenteritis, meningitis (high mortality), bacteraemia (1-5% diarrhoea) _- typhoid fever_: salmonella typhi (rose spots, pain, pea-soup diarrhoea) **treatment:** antibiotics if \<3 months or immunocompromised - ceftriaxone, ampicillin

Answer 83

**incubation:** 10-14 days **clinical** - week 1: fever, headache, myalgia - week 2: vomiting, diarrhoea, cough - week 3: rose spots - resolves in 2-4 weeks

Answer 84

**definition:** superantigen mediated toxic syndrome of GAS pharyngitis **mechanism:** delayed-type skin reactivity to pyrogenic exotoxins A,B,C - formation of specific antitoxin antibodies **clinical:** - rash within 24-48 hours of symptoms lasting 3-4 days - diffuse, papular erythematous sandpaper blancing rash to neck/trunk/extremities with desquamation - face spared and circumoral pallor - strawberry tongue **prognosis:** mortality 20% untreated, 1% treated

Answer 85

**parasite**: trematode (flat worms) **location:** Africa, Middle East **transmission:** direct penetration of skin from eggs in freshwater **pathogenesis:** related to immune system response to eggs that invade local tissue - can cause fibrosis/scarring **clinical:** **- GI:** abdominal pain, diarrhoea, PR bleeding, HSM - **GU:** bladder/gonadal fibrosis, renal dysfunction **diagnosis:** eggs in urine/stool **treatment:** praziquantel

Answer 86

**bacteria:** gram negative rod **pathophysiology:** phagocytosed and replicated intracellularly and spreads cell-cell - releases shiga toxin - infection with \<10 organisms **clinical:** bloody diarrhoea, WCC in stool **treatment:** amoxycillin, bactrim

Answer 87

**bacteria:** gram positive cocci in clusters **source:** normal skin flora with low virulence **clinical:** infection if foreign body or immune compromise only - prosthetic devices (heart valves, catheters) **treatment:** vancomycin (usually resistant to vancomycin)

Answer 88

**mechanism:** epidermolytic/exfoliative toxins A or B - act on zona granulosa of epidermis - granular layer split by binding desmoglein I in desmosomes - formation of fragile/tense bullae **clinical:** \<5yrs - rash preceded by fever, malaise, conjunctivitis, tender/erythematous skin - 1-2 days later: flaccid blisters with Nikolsky's sign - no scarring **diagnosis:** - bullae: sterile - skin biopsy: cleave plane in lower stratum granulosum with minimal necrosis, _NO_ inflammatory infiltrate **treatment:** IV penicillin

Answer 89

**bacteria:** gram positive cocci in clusters - coagulase positive - forms yellow golden colonies **pathophysiology:** - major virulence factor protein A: interacts IgG preventing opsonisation - techoic acid: adhesion to mucosal cells - slime layer: protects from opsonisation - coagulase: interacts with fibrinogen to cause organism clumping and protect from phagcytocsis - catalase: inactivates H2O2 - beta lactamase: AB resistance **clinical:** tissue abscesses, soft tissue infection, pneumonia (HAP), osteomyelitis, impetigo **exotoxin mediation:** TST, SSS, food poisoning _- toxins:_ TSST-1, enterotoxin (both superantigens) - effects persist despite treatment **methicillin resistance:** conferred by altered penicillin proteins **MSSA treatment:** flucloxacillin **MRSA treatment:** clindamycin + ciprofloxacin, vancomycin, linezolid

Answer 90

**organism:** gram negative bacillus **source:** hospital environment, tap water, nebulisers **infection:** opportunistic serious infection in ICU typically ventilators

Answer 91

**bacteria:** commensal gram positive cocci **clinical:** dental caries

Answer 92

**organism:** gram positive cocci catalase negative **Lancefield grouping** (based on carbohydrate composition) - group A: strep pyogenes - group B: strep agalactiae - group C/D: beta haemolytic strep - group D: enterococcus - group E/F: alpha haemolytic (S. pneumoniae and viridans)

Answer 93

**bacteria:** gram positive cocci in pairs or chains - 90 serotypes, encapsulated most virilent - virulence factor: IgA protease, polysaccharide capsule **clinical:** most common cause of bacteraemia (80%), bacterial pneumonia, and OM in childrens - also meningitis (2nd most common cause), sinusitis, osteomyelitis, brain abscess, empyema, pericarditis **treatment:** benzyl penicillin + gentamicin **complications:** increased severity with SS, B cell defects, HIV, leukaemia, aplasia **risk factors:** \<2yrs, male, SS/asplenia, HIV, cochlear implant, immunse disease, immunosuppresion vaccination: PPV23 covers \>95% invasive serotypes, decrease invasive infection 93%, decreased lobar pneumonia 73%

Answer 94

**bacteria:** gram positive cocci in chains - \>100 serotypes **virulence**: M protein resistance to phagocytosis **toxins:** 3 pyrogenic exotoxins (SpeA,SpeB,SpeC) - SpeB: necrotising fasciitis **enzymes:** hyaluronidase, streptokinase, steptolysin O/S **clinical:** pharyngitis, impetigo, eryspialis/cellutitis **toxin mediated disease**: scarlet fever, TSLS, necrotizing fasc - _scarlet fever_: pharyngitis, strawberry tongue, sandpaper like rash **risk factors:** age 3-15yrs, winter, HIV, DM, chronic disease **AI disease**: rheumatic fever, post strep GN **treatment:** benzyl penicillin

Answer 95

**mechanism:** inhibit production of folic acid needed for DNA synthesis **drugs:** bactrim **cover** - +: enterococcus, listeria, GAS, PCP NO staph/strep - -: Ecoli

Answer 96

**drugs:** tetracycline, doxycycline, minocycline **mechanism:** - bacteriostatis - inhibit binding of tRNA at 30s subunit ribosome **cover:** + staph, strep, malaria, cholera, NO -

Answer 97

**organism:** staph and strep superantigens - staph aureus: toxic shock syndrome causing toxin (TSST) - strep pyogenes: strep pyrogenic exotoxins **mechanism:** - superantigens create toxins A,B,C,D,E - superantigens join APC non specifically and cause massive Tcell proliferation and cytokine release **clinical:** shock with liver, renal, pulmonary, neuro sx **diagnosis:** - s.aureus: blood cultures negative - GAS: blood cultures positive - thromboytopaenia **treatment:** treat shock/source of infection, antibiotics, IvIG, clindamycin (stops toxin transcription)

Answer 98

**Treat all close contacts ASAP** - AB prophylaxis for household of contacts in last 7 days **Antibiotics** - children rifampicin 2/7 - adults: IM ceftriaxone or cipro or fluclox STAT _DO NOT GIVE_ rifampicin/ciprofloxacin in pregnancy: teratogenic

Answer 99

**A**minoglycosides (gentamicin/tobramycin) **A**ztreonam **C**ephalosporin (ceftazidime/cefipime) **C**arbapenem **T**imentin

Answer 100

**bacteria:** spirochete **clinical:** - _primary syphillis:_ painless chancre - _secondary:_ 1-6months condylomo lata - _tertiary:_ 1-10yrs, gumma formation, neuro sx - _congenital:_ rhinoritis, lesions, hepatospleenomegally, haemolytic anaemia/thrombo **diagnosis:** VDRL, RPR, syphilus IgM

Answer 101

**mechanism:** competetively inihibit bacterial folate production

Answer 102

**organism:** gram +ve bacilli aerobes mycoplasma tuberculosis **epidemiology:** rate of new cases/mortality falling - highest risk 0-1yrs - 10% cases worldwide are children - highest burden: Africa, Asia, Latin America - 10% coinfected HIV **transmission:** droplets, untreated infected person 15 others/yr **etiology:** 5 mycobacteria in M.tuberculosis complex: M.tuberculosis, M.bovis, M.africanum, M.microti, M.canetti **pathophysiology:** _1) initial infection: i_nhalation of droplet, 40% chance develop TB - local infection at portal of entry: bacilli carried to LN by macrophages - local tissue inflammation with LN/parenchyma causing tissue hypersensitivity - progression to fibrosis/calcification/caseation= caseating granuloma (primary Gohn complex) _2) Post primary infection_ - 90% enter latent phase/10% develop TB pneumonia _3) Clinical disease_ - disseminated/meningeal 2-6 months - pulmonary 3-9 months - bones/joints year _4) Reactivation_ - \>1yr after initial infection - endogenous regrowth of partially encapsulated lesions **clinical:** - asymptomatic early stages _pulm TB:_ chronic cough, fever\>38 for \>2wks, weight loss, FTT - primary TB CXR: regional lymphadenitis, small lung focus, pleural effusion - miliary TB CXR: diffuse millet seeds - reactivation TB: right upper lobe _extrapulmonary (_25% presentation) - disseminated disease (hepatosplenomegally, LN, skin, CNS (0.3%), pericardial effusion, abdominal, renal, bones) **TB/HIV coinfection:** increased mortality/dissemination/extrapulmonary **perinatal infection:** mortality 50%, onset 2-3wks sepsis, congenital rare MDR TB: need 18m treatment, difficult to treat

Answer 103

**diagnosis:** - _organism tests:_ microscopy, AFB, culture from body fluid (8-10wks), molecular testing (40-80% sensitive if smear positive, NAAT, PcR) - _immune response tests:_ TST (crossreacts BCH, false negatives), immune response test, quantaferon gold (IFN-g release assay) - ALWAYS test for HIV **prevention:** vaccine BCG: 50% effective preventing pulm TB, 50-80% effective preventing disseminated/meningeal TB, time limited **treatment:** RIPEx2, RIx4 - RIPE for 2 months then RI for 4 more months - if MDR then for 19 months - TB meningitis for 6-9months

Answer 104

**virus:** herpesviridae ds DNA **incubation:** 10-21 days **transmission**: 80-90% households, 1-2d before rash and until crusts over **clinical:** fever, pruritic rash, headache, malaise, anorexia - complications: pneumonia, postinfectious cerebellar ataxia (1/4000), encephalitis (1/100,000), zoster **post exposure:** vaccine\<72 hrs - ZIG: pregnant women \<96hrs, neonates from day 5 prior and 2 days post birth if mother develops, neonates \<30d old if mother negative, premature infants \<28wks, immunosuppressed - immunocompromise: ZIG and IV aciclovir - "significant exposure": face-face\>5 mins, same household, same room\>1hr

Answer 105

**bacteria:** comma-shaped motile gram negative rod - large inoculum required **transmission**: faecal oral **pathophysiology:** - do NOT invade GI mucosa/blood - cholera toxin: AB exotoxin, increased cAMP and Cl secretion causing increased Bicarb secretion **clinical:** large watery mucous gastroenteritis (rice water stool) - 20% severe dehydration **treatment:** doxycycline, tetracycline

Answer 106

**viruses:** - enterovirus (most common) - herpesvirus: HSV1 (most severe/encephalitis), HSV2 (neonates) - VZV (cerebellar ataxia to severe encephalitis) - CMV/HHV6: immunocompromised also: EBV, arbovirus, adenovirus, influenza,lymphocytic choriomeningitis virus, measles, mumps, HIV **treatment:** aciclovir for HSV otherwise supportive

Answer 107

**bacteria:** gram negative rod, anaerobic, motile at 22 degrees **pathophysiology**: terminal ileum, colonizes peyer's patch causing terminal ileitis - fever, RIF pain **transmission:** animal faeces **treatment:** self-limited, bactrim, ceftriaxone

Answer 108

**invasive aspergillus:** voriconazole **candida:** fluconazole, caspofungin **cryptococcus:** amphotericin B \*\*Amphotericin good broad spectrum but toxic

Answer 109

**polyenes (ampho, nystatin):** make holes in cell membrane **azoles/terbinafine:** interefere with celll membrane synthesis **echinocandins (caspofungin):** inhibit cell was synthesis **griseofluvin/5 FC:** cell division, NA synthesis inhibitor