Infectious Disease Flashcards
Amoebiasis
Entamoeba histolytica, spread by faeco-oral route
= asymp, mild diarrhea, dysentery (profuse watery, may be long incubation)
Inv - hot stool microscopy
-> PO metronidazole, luminal agent
Comp - liver abscess (right lobe, fever/ RUQ pain, US, anchovy paste aspiration)
Bites
Causes - dogs and cats (multiple org, Pastuerella), human
-> clean wound, co-amoxiclav (doxy + met if allergy)
Anthrax
Woolsorter’s disease, bacillus anthracis, gram+ rod, spread by infected carcasses
= painless black eschar, no pus, GI bleeding
-> ciprofloxacin
Aspergilloma
Mass-like fungus ball (mycetoma), often colonises an existing lung cavity
RF - lung cancer, CF, TB
= cough, blood
Inv - CXR (rounded opacity, crescent sign), Aspergillus preciptins
Bacillus cereus
Gram+ rod, food poisoning, resolves <24hrs
Causes - reheated rice
= (30m-6hrs after) vomiting from cereulide toxin, (8-16hrs) diarrhea from other exotoxins, crampy abdo pain
Botulism
Clostridium botulinum, produces neurotoxin that irreversibly blocks Ach release
Causes - tinned food, IVDU
= flaccid paralysis, diplopia, ataxia, bulbar palsy, fully conscious
-> botulism antitoxin must be given early
Campylobacter jejuni
Most common bacterial GE in UK, gram- bacillus, foecal-oral
= headache/ malaise prodrome, diarrhea, may be bloody, abdo pain
-> self limits, clarithromycin if severe/ IC
Comp - Guillain-Barre, reactive arthritis
Cat Scratch disease
Bartonella henselae, gram- rod
= Hx cat scratch, fever, regional nodes, headache
Chancroid
Haemophilus ducreyi, tropical disease
= painful genital ulcers, unilateral painful inguinal nodes
Chickenpox Exposure: IS
-> VZ Ig
See obs for pregnancy
Cholera
Vibrio cholerae, gram-
= profuse diarrhea (rice water), dehydration, hypoglycaemia
Classification of bacteria
Gram+ cocci = staph, strep, enterococci
Gram+ rods (ABCD L)
= actinomyces, bacillus anthracis, clostridium, diphtheria, listeria monocytogenes
*Gram+ turn purple/ blue when stained
Gram- cocci = Neisseria meningitidits/ gonorrhoea, moraxella catarrhalis
Gram- rod = everything else
Cryptosporidiosis
Most common protozoal diarrhea in UK, hominis or parvum
RF - IS, young children
= water diarrhea, abdo cramps, fever, sclerosing cholangitis, pancreatitis
Inv - acid-fast stool (red cysts)
Cytomegalovirus
= congenital, mononucleosis, retinitis (bleeds, necrosis, pizza -> IV ganciclovir), encephalopathy, penumonitis, colitis
Inv - Owl’s eye (intranuclear inclusion bodies)
Dengue Fever
Viral infection, RNA, mosquito spread, hemorrhagic if severe
= fever, headache, bone pain, myalgia, pleuritic pain, flushing, MP rash, vomiting, DIC (v PLT, bleeding)
Comp - dengue shock syndrome
Diphtheria
Corynebacterium diphtheriae, gram+, exotoxin
RF - east Europe/ Asia,
= sore throat, diphtheric membrane on tonsils (necrotic mucosal cells), bulky cervical lymp, neuritis, heart block
-> IM penicillin, antitoxin
Enteric Fever
Salmonella typhi (typhoid) and paratyphi (paratyphoid), gram- rods, faecal-oral
= headache, fever, arthralgia, bradycardia, abdo pain, distention, constipation, rose spots (trunk, ^pt)
Comp - osteomyelitis (^sickle cell), GI bleed, meningitis, cholecystitis
EBV: Links
Burkitt’s, Hodgkin’s, nasopharyngeal cancer, HIV-associated CNS lymphomas.
Hairy leukoplakia
Escherichia coli
Gram- rod
= traveller’s diarrhea, HUS (O157:H7, ground beef), UTI, neonatal menignitis
Genital Herpes
Causes - HSV2 (and HSV1)
= painful genital ulcers, dysuria, pruritis, systemically unwell in primary infection, tender ing nodes
Inv - NAAT
-> PO acyclovir, saline bathing, pain relief, lidocaine
Genital Warts
Condylomata accuminata, HPV 6/11
= small fleshy lumps, may bleed or itch
-> top podophyllum or cryotherapy, often resist/ recur
Giardiasis
Giardia lamblia, protozoa, faeco-oral spread
RF - travel, swimming in river/lake, MSM
= aymptomatic, non-bloody diarrhea, steatorrhoea, abdo pain, bloating, weight loss, malabsorption, lactose intol
Inv - stool microscopy (trophozoite, cysts), stool antigen
-> metro
Gonorrhoea
Neisseria gonorrhoea, gram- diplococcus
= (males) urethral discharge, dyrsuria, (females) cervicitis, discharge
Comp - urethral strictures, epididymitis, salpingitis (infertility), septic arthritis, disseminated (migratory polyarthritis, dermatitis, tenosynovitis)
-> IM Ceftriaxone, or PO cefixime + azithromycin
Gas Gangrene (Myonecrosis)
Clostridia perfringens, a-toxin causing gangrene and haemolysis
= tender oedematous skin, haemorrhagic blebs and bullae, crepitus
Hepatitis: Key Bits
A) FO, institutions, not chronic, no HCC, vaccine available
B) fluids, chronic and HCC (polyarteritis, cryo, GN), vaccine available
C) blood (IVDU/ transfuse <1991), chronic and HCC (porphyria, cryo, GN), no vaccine
D) fluids (with hep B only), chronic and HCC, no vaccine
E) FO (pork), mortality during pregnancy, no chronic, no HCC, no vaccine
Herpes Simplex Virus
= gingiviostomatitis (primary infection), cold sores, painful genital ulcers
-> PO/ topical acyclovir
Pregnant
Primary - urgent referral, treat in T3, elective c-section if acquired at term
Recurrent - risk of transmission is low, may suppress >36wks
Infectious mononucleosis
Causes - EBV, CMV, HHV6
= sore throat, fever, lymph nodes, malaise, palatal petechiae, splenomegaly, ^LFTs, atypical lymphocytes, cold hemolytic anaemia, MP rash with amoxicillin
Inv - heterophil Ab test (monospot) in 2nd week of illness
-> supportive, avoid contact sports for 4wks (splenic rupture)
Legionella
Colonizes water tanks
= flu-like, fever, dry cough, bradycardia, confusion
Inv - lymphopenia, v Na, ^LFTs, CXR (mid/lower consol, pleural effusion), urinary antigen to diagnose
-> erythromycin or clarithromycin
Leprosy
Mycobacterium leprae, granulomatous disease of peripheral nerves and skin
= hypopigmented bum/ face/ extensors, sensory loss
-> rifampicin + dapsone + clofazimine
Leptospirosis
Leptospira interrogans, infected rat urine
RF - sewage worker, farmer, vets, ^tropics
= (early) fever, flu-like, subconjunctival haemorrhage, (second - Weil’s) AKI, hepatitis, jaundice, aseptic meningitis
Inv - Ab Leptospira develop after 7 days, PCR, blood/ urine culture, CSF
-> high-dose benzylpenicillin or doxycycline
Leishmaniasis
Sandfly bite
Cutaneous - crusted lesion
Mucocutaneous - nose and pharynx involved
Visceral - fevers, sweats, splenomegaly, weight loss, grey skin, hypersplenism
Lyme disease
Borrelia burgdorferi, spread by ticks
Early (<30d) = erythema migrans (bulls eye), headache, fever, joint pain
Late (>30d) = heart block, peri/myocarditis, facial nerve palsy
Inv - clinical, ELISA Ab if no rash (repeat at 4wks if still suspected), immunoblot
-> remove tick, doxy if early (amox if allergy/ preg), ceftriaxone if disseminated
Lymphogranuloma Venereum
Chlamydia trachomatis
RF - MSM, HIV, tropics
- Small painless pustule, forms into ulcer
- Painful inguinal nodes
- Proctocolitis
-> doxycycline
Malaria
Plasmoidium protozoa, spread by female anopheles mosquito, ^severe with falciparum
Falciparum
= acidosis, fever, anaemia, low glucose, schizonts on blood film
Comp - seizures, AKI, ARDS, DIC
Vivax, Ovale, Malariae
= fever (cycles 48hrs), headache, splenomegaly, nephrotic syndrome with malariae
-> artemisinin based combination or chloroquine
Necrotising Fasciitis
Medical emergency
Causes - T1 by mix (post-surgical DM), T2 by strep pyo
= ^perineum (Fournier’s), acute onset, pain ≠ features, swelling, erythema, necrosis, crepitus, fever, tachy
-> urgent referral to surgery, debridement, IV Abx
Pseudomonas aeruginosa
Gram- rod
= chest infections (^CF), burns, wound infections, ‘hot tub’ folliculitis, otitis externa, UTI
Q fever
Coxiella burnetti
Causes - abattoir, cattle, sheep
= prodrome (fever, malaise), atypical pneumonia, endocarditis (culture negative), transaminitis
-> doxy
Rabies
Viral disease causing acute encephalitis
= prodrome of headache, fever and agitation, hydrophobia (water causes muscle spasm), salivation
-> HR Ig and full course of vaccine
Schistosomiasis haematobium
Parasitic flatworm, Africa, risk of bladder SCC
= swimmer’s itch, obstructive uropathy, bladder calcification, haematuria
Inv - XR (calcification of egg clusters)
-> single PO praziquantel
Toxic Shock Syndrome
Severe systemic reaction to staphylococcal exotoxins, infected tampons
= fever, v BP, diffuse erythematous rash, desquamation
Syphilis
Treponema pallidum
Primary
= chancre (painless ulcer), local non-tender nodes
Secondary (6-10wks later)
= fever, lymphadenopathy, rash on trunk/ palms/ soles, buccal ulcers (snail track), condylomata lata (painless warts on genitals)
Tertiary
= gummas (skin/ bone granuloma), aortic aneurysms, tabes dorsalis, Argyll-Robertson pupil
-> IM benpen, may get Jarisch Herxheimer reaction (fever, rash, tachy but no wheeze/ v BP)
Congenital
= blunt incisors, mulberry molars, rhagades (linear mouth scar), keratitis, saber shins, saddle nose, deaf
Syphilis: Investigation
Non-treponemal - RPR, VDRL (not sensitive to syphilis) *False positives in pregnancy, HIV, Malaria, TB and SLE
Treponemal - T pallidum-EIA, TP-HA (sensitive)
Results
+ve NT and +ve Trep = active infection
+ve NT and -ve Trep = false positive
-ve NT and +ve trep = successfully treated syphilis
Tetanus
Clostridium tetani, exotoxin prevents GABA release
RF - IVDU
= fever, lethargy, headache, lockjaw, facial spasm, arched back/ extended neck (opisthotonus)
-> metronidazole, IM HT Ig
Toxoplasmosis gondii
Obligate intracellular pathogen, cats
= asymp, like infectious mononucleosis, IS get cerebral toxoplasmosis (CT multiple ring enhancing lesions), chorioretinitis
-> pyrimethamine + sulphadiazine for 6 weeks
Yellow Fever
Viral hemorrhagic fever, mosquito
= flu-like, sudden onset high fever, rigor, n+v, bradycardia, brief remission before jaundice, oliguria
TB
RF - Asia/ South America/ Africa, exposure, HIV (20x), IS, silicosis, apical fibrosis
Primary: Ghon focus in lungs (complex with hilar nodes), granuloma formation, necrosis in centre, heals by fibrosis (or miliary if IS)
Secondary: reactivation when host is IS
- apex of lungs, CNS (meningitis), cervical nodes (scrofuloderma), vertebral bodies (Pott’s), renal, GIT
Inv - Mantoux for latent, in active use CXR (upper cavitation, BHL), 3 acid-fast sputum smears (v sensitive in HIV), NAAT, sputum culture is best
Mantoux test - induration <6mm is negative (give BCG), 6-15mm is hypersensitive (? prev BCG/ TB), >15mm TB
TB: Management
Active -> 2m RIPE, RI for 4m, if meningeal then 1yr steroids as well
Latent -> 3m RI or 6m I (p), cannot pass on the disease
HIV
Seroconversion 3-12wks after infection
= sore throat, lymph, myalgia, diarrhea, MP rash, mouth ulcers, then asymp until IC (AIDS defining)
Inv - HIV Ab (99% by 3m, ELISA and Western blot) + p24 antigen, repeat to confirm (12wk if neg), viral load
*Test 4wks post-exposure if no symptoms
HIV management
ART asap after diagnosis e.g., 2NRTI + PI or NNRTI
AIDS defining illnesses
Kaposi’s sarcoma - HHV-8
= purple skin papules, radio + resect
Pneumocystis jiroveci pneumonia (PCP) - ^common opportunistic, prophylaxis if CD4 <200
= few chest signs, SOB, dry cough, fever, pneumothorax, exercise induced desat, BA lavage
-> co-trimoxazole
Candidiasis - ^common cause of oesophagitis in HIV
-> fluconazole
CNS lymphoma - linked with EBV
= homogenous ring enhancing lesion, single or multiple, SPECT+ve
Others incl. oral thrush, shingles, hairy leukoplakia (EBV), Cryptosporidium diarrhoea, cerebral toxoplasmosis, leukoencephalopathy, HIV dementia, aspergillosis, TB
Cryptococcus
Fungal infection of CNS, seen in HIV
= headache, fever, n+v, seizures, focal neuro
Inv - LP (high opening pressure, India ink), CT (meningeal enhancement, oedema)
Benign Liver Lesions
Hemangioma: benign tumour
= red/ purple, hyper-vascular, US (hyperechoic)
Liver abscess: comp of biliary sepsis
= US (fluid-filled cavity)
Hydatid cyst: Echinoccous infection, fibrotic reaction
= malaise, RUQ pain, ^LFTs, eosinophilia, US (septa, daughter cysts), don’t aspirate
-> mebendazole to sterilise, resect
Live Vaccines
BCG
MMR
oral polio
yellow fever
oral typhoid
