Infectious diseases Flashcards

Question

What are the risk factors for a surgical site infection?

Answer 1

* patient characteristics * age, DM, steroids, immunosuppression, obesity, burn, malnutrition, patient with other infections, traumatic wound, radiation, chemotherapy * other factors * prolonged pre-operative hospitalisation, reduced blood flow, break in sterile technique, multiple antibiotics, haematoma, seroma, foreign bodies (drains, sutures, grafts), skin preparation, hypoxaemia, hypothermia

Answer 2

* typically fever POD #5-8 (*Streptococcus* and *Clostridium* can present in 24h) * pain, blanchable wound erythema, induration, purulent discharge, warmth * complications: fistula, sinus tracts, sepsis, abscess, suppressed wound healing, superinfection, spreading infection to myonecrosis or fascial necrosis (necrotizing fasciitis), wound dehiscence, evisceration, hernia

Answer 3

* used to reduce the chance of surgical site infections pre-operative antibiotics for most surgeries (cefazolin ± metronidazole or if β-lactam allergy, clindamycin ± gentamycin) * within 1 h pre-incision; can re-dose at 1-2 half-lives (_~q4-8h) in the OR * not required for low risk elective cholecystectomy, hemorrhoidectomy, fistulotomy, sphincterotomy for fissure * generally no need to continue prophylactic antibiotics post-operatively * reserve post-operative antibiotics for treatment of suspected or documented intra-abdominal infection * normothermia (maintain patient temperature 36-38ºC during OR) * hyperoxygenation (consider FiO2 of 80% in OR) * chlorhexidine-alcohol wash of surgical site * hair removal should not be performed unless necessary; if so, clipping superior to shaving * protect skin edges (moistened lap pads); consider delayed primary closure of incision for contaminated wounds

Answer 4

* examination of the wound: inspect, compress adjacent areas, swab drainage for C&S and Gram stain * re-open affected part of incision, drain, pack, heal by secondary intention in most cases * for deeper infections, debride necrotic and non-viable tissue * antibiotics * demarcation of erythema only if cellulitis or immunodeficiency

Answer 5

* neuropathy, peripheral vascular disease, and hyperglycemia contribute to foot ulcers that heal poorly and are predisposed to infection * organisms in mild infection: *S. aureus, Streptococcus* spp. * organisms in moderate/severe infection: polymicrobial with aerobes (*S. aureus, Streptococcus, Enterococcus*, GNB) and anaerobes (*Peptostreptococcus, Bacteroides, Clostridium*)

Answer 6

* NOT all ulcers are infected * consider infection if: probe to bone, ulcer present \>30 d, recurrent ulcers, trauma, PVD, prior amputation, loss of protective sensation, renal disease, history of walking barefoot * diagnosis of infected ulcer: ≥2 of the cardinal signs of inflammation (redness, warmth, swelling, pain) or the presence of pus * ± crepitus, osteomyelitis, systemic toxicity * visible bone or probe to bone → osteomyelitis * infection severity: * mild = superficial (no bone/joint involvement) * moderate = deep (beneath superficial fascia, involving bone/joint) or erythema \>2 cm * severe = infection in a patient with systemic toxicity (fevers, tachypnea, leukocytosis, tachycardia, hypotension)

Answer 7

* curettage specimen from ulcer base, aspirate from an abscess or bone biopsy (results from superficial swabs do not represent organisms responsible for deeper infection) * blood C&S if febrile * assess for oseteomyelitis by x-ray (although not sensitive in early stages) or MRI if high clinical suspicion * if initial x-ray normal, repeat 2-4 wk after initiating treatment to increase test sensitivity

Answer 8

* evaluate for early surgical debridement ± revascularization or amputation * eliminate/reduce pressure and provide regular local wound care * mild to moderate: Amoxycillin + clavulanate 875 + 125 mg PO 12h * severe: piperacillin/tazobactam 4 + 0.5 g IV q8h * encourage glycemic control

Answer 9

* commonly identified causes of fever in returning traveler * parasitic: malaria (20-30%) * viral: non-specific mononucleosis-like syndrome (4-25%), dengue (5%), viral hepatitis (3%) * bacterial: typhoid from Salmonella (2-7%), rickettsioses (3%) * diverse group of causative pathogens: traveler's diarrhea (10-20%), RTI (10-15%), UTI/STD (2-3%) * febrile illness in travelers can be caused by routine infections that are common in non-travelers (e.g. URTI, UTI) * less commonly, fever can be due to non-infectious causes: e.g. DVT, PE

Answer 10

* pre-travel preparation * travel itinerary: when, where, why, what, who, how? * dates of travel (determine incubation period) * season of travel: wet or dry * destination: country, region (urban or rural), environment (jungle, desert, etc.) * purpose of trip * persons visiting friends and family more likely to be exposed to local population and pathogens * style of travel: lodgings, camping, adventure traveling * local population: sick contacts * transportation: use of animals * exposure history * street foods, untreated water: increased risk of traveler's diarrhea, enteric fever * uncooked meat/unpasteurized dairy: increased risk of parasitic infection * body fluids (sexual contacts, tattoos, piercings, IVDU, other injections) * increased risk of HBV, HCV, HIV, GC, C. trachomatis, syphilis * animal/insect bites: increased risk of malaria, dengue, rickettsioses, rabies * fever pattern * incubation period: use the earliest and latest possible dates of exposure to narrow the differential diagnosis and exclude serious infections * \<21 d: consider malaria, typhoid fever, dengue fever, rickettsioses; exclude HBV, TB * \>21 d: consider malaria, TB; exclude dengue fever, travelers' diarrhea, rickettsioses * body systems affected: GI, respiratory, CNS, skin

Answer 11

* all travelers with fever should undergo the following tests * blood work: FBC, LFT, UECs, thick and thin blood smears x3 (for malaria), blood C&S * urine: urinalysis, urine C&S * special tests based on symptoms, exposure history, and geography * stool: C&S, O&P * CXR * dengue serology for IgM

Answer 12

1. Sporozoites enter blood via mosquito bite, infect liver 2. Hepatic infiltration 3. Infect red blood cells 4. Trophozoite divides asexually many times to produce schizont (contains merozoites) 5. Red blood cell lyses and merozoites attack other red blood cells (chills and fever) 6. Male and female gametocytes (from merozoites) ingested by mosquito during bite 7. Male and female gametocytes (from merozoites) fuse in mosquito gut; produce ookinete 8. Ookinete matures into an oocyst which contains individual sporozoites; migrates to mosquito salivary glands

Answer 13

* flu-like prodrome * paroxysms of high spiking fever and shaking chills (due to synchronous systemic lysis of RBCs) (lasts several hours) * P. vivax and P. ovale: chills and fever q48h but can be variable * P. malariae: chills and fever q72h but can be variable * P. falciparum: less predictable fever interval, can be highly variable (\>90% ill within 30 d) * abdominal pain, diarrhea, myalgia, H/A, and cough * hepatosplenomegaly and thrombocytopenia without leukocytosis

Answer 14

* *P. falciparum*: CNS involvement (cerebral malaria = seizures and coma), severe anemia, acute renal failure, ARDS, primarily responsible for fatal disease * *P. knowlesi*, and rarely *P. vivax* can be fatal

Answer 15

* microscopy: blood smear q12-24h (x3) to rule out infection * thick smear (Giemsa stain) for presence of organisms * thin smear (Giemsa stain) for species identification and quantification of parasites * rapid antigen detection tests

Answer 16

* P. vivax, P. ovale: chloroquine (and primaquine to eradicate liver forms) * P. vivax, chloroquine resistant: primaquine with quinine and doxycycline or tetracycline or mefloquine * P. malariae, P. knowlesi: chloroquine * P. falciparum: most areas of the world show chloroquine resistance – check local resistance patterns * artemisinin combination therapy (e.g. artesunate + doxycycline or clindamycin or atovaquone/proguanil) * atovaquone/proguanil combination (Malarone®) * quinine plus doxycycline, tetracycline, or clindamycin * mefloquine and artemisinin resistance increasing in southeast Asia (check local resistance) * prevention with antimalarial prophylaxis, covering exposed skin, bed nets, insect repellant

Answer 17

* Most cases occur in \>50 * M\>F = 2:1 * Risk factors: * IVD use * endocarditis * degenerative spine disease * prior spinal surgery * corticosteroid therepy/immunocompromised state

Answer 18

* *Staph aureus* (\>50%) * Enteric gram -ve bacilli - urinary tract instrumentation * *Pseudomonas aeruginosa and Candida spp.* - associated with IVD * Group B and G haemolytic streptococci - esp. in DM * TB

Answer 19

* Back or neck pain - localised to the infected disc space, exacerbated by physical activity or percussion to the affected area. * Radiating pain to the abdo, leg, scrotum, groin or perineum * Spinal pain that begins insidiously and progressively worsens over weeks\>months and worse at night

Answer 20

* Bloods: FBC, UECs, LFT, CRP/ESR, blood cultures, * Urine: MCS * Echo: endocarditis * Imaging: CT guided needle bipsy (MCS), MRI

Answer 21

* Abx: pathogen specific - for a min of 6 weeks * Staph aureus: cefazolin 2g IV q8h * Strep spp: ceftriaxone 1-2g IV q24h * Empirial: vancomycin 15-20 mg/kg Q8-12h PLUS a cephalosporin * Surgery: used only in patietns with neurological deficits

Answer 22

Inflammation of the meninges

Answer 23

* lack of immunisation against S. pneumoniae, H. influenzae type b in children * haematogenous spread after invasion from a mucosal surface (nasopharynx) * parameningeal focus (otitis media, infection, sinusitis) * penetrating head trauma * anatomical meningeal defects – CSF leaks * previous neurosurgical procedures, shunts * immunocompromise (corticosteroids, HIV, asplenia, hypogammaglobulinemia, complement deficiency) * contact with colonised or infected persons

Answer 24

* neonates and children: fever, vomiting, lethargy, irritability, poor feeding * older children and adults: fever, H/A, neck stiffness, confusion, N/V, lethargy, photophobia, altered level of consciousness, seizures, focal neurological signs, papilledema * petechial rash in meningococcal meningitis, seen more frequently on trunk or lower extremities

Answer 25

* blood work: * FBC and differential, UEC (for SIADH), blood C&S * CSF: opening pressure, cell count + differential, glucose, protein, Gram stain, bacterial C&S * Acid fast bacilli, fungal C&S, cryptococcal antigen in immunocompromised patients, subacute illness, suggestive travel history or TB exposure * PCR for HSV, VZV, enteroviruses, WNV if viral cause suspected * imaging/neurologic studies: * CT, MRI, EEG if focal neurological signs present

Answer 26

* bacterial meningitis is a medical emergency: **do not delay antibiotics for CT or LP** * empiric antibiotic therapy * \<2 mo call paeds/ED consultant * age \>2 mo + adults: ceftriaxone IV * Direct Abx therapy: see eTG for specific treatments * Dexamethasone IV within 20 min prior to or with first dose of antibiotics * continue Q6h for 4 days

Answer 27

* immunization * children: immunization against H. influenzae, S. pneumoniae, N. meningitidis * adults: immunization against N. meningitidis in selected circumstances (outbreaks, travel, epidemics) and S. pneumoniae (Pneumovax®) for high-risk groups * prophylaxis: close contacts of patients infected with H. influenzae should be treated with rifampin if they live with an inadequately immunized (\<4 yr) or immunocompromised child (\<18 yr); ciprofloxacin, rifampin, or ceftriaxone if close or household contact of a patient with N. meningitidis

Answer 28

* infection of cardiac endothelium, most commonly the valves * classifications: acute vs. subacute, native valve vs. prosthetic valve, right-sided vs. left-sided * leaflet vegetations that are comprised of platelet-fibrin thrombi, WBCs, and bacteria

Answer 29

* predisposing conditions * high risk: prosthetic cardiac valve, previous IE, congenital heart disease (unrepaired, repaired within 6 mo, repaired with defects), cardiac transplant with valve disease (surgically constructed systemic-to-pulmonary shunts or conduits) * moderate risk: other congenital cardiac defects, acquired valvular dysfunction, hypertrophic cardiomyopathy * low/no risk: secundum aterial septal defect (ASD) or surgically repaired ASD \< VSD, PDA, MV prolapse, ischemic heart disease, previous CABG * opportunity for bacteremia: IVDU, indwelling venous catheter, hemodialysis, poor dentition, DM, HIV * frequency of valve involvement MV \>\> AV \> TV \> PV but in 50% of IVDU-related IE the tricuspid valve is involved

Answer 30

* Streptococcus1 (36%) * S. aureus4 (28%) * Enterococcus (11%) * S. epidermidis * GNB * Other: * Streptococcus bovis (usually associated with underlying GI malignancy, cirrhosis) * Culture-negative organisms including nutritionally-deficient streptococci, HACEK, Bartonella, Coxiella, Chlamydia, Legionella, Brucella * Candida

Answer 31

* S. aureus (68%) * Streptococcus (13%) * Enterococcus * GNB * Candida * Other: * IVDU endocarditis pathogens depend on substance used to dilute the drugs (i.e. tap water = Pseudomonas, saliva = oral flora, toilet water = GI flora)

Answer 32

* S. aureus (36%) * S. epidermidis (17%) * Enterococcus * GNB * Other: * Streptococcus bovis (usually associated with underlying GI malignancy, cirrhosis) * Culture-negative organisms including nutritionally-deficient streptococci, HACEK, Bartonella, Coxiella, Chlamydia, Legionella, Brucella * Candida

Answer 33

* Streptococcus (20%) * S. aureus (20%) * S. epidermidis (20%) * Enterococcus (13%) * Other: * Streptococcus bovis (usually associated with underlying GI malignancy, cirrhosis) * Culture-negative organisms including nutritionally-deficient streptococci, HACEK, Bartonella, Coxiella, Chlamydia, Legionella, Brucella * Candida

Answer 34

* Modified Duke Criteria * definitive diagnosis if: 2 major, OR 1 major + 3 minor, OR 5 minor * possible diagnosis if: 1 major + 1 minor, OR 3 minor

Answer 35

* systemic * fever (80-90%), chills, weakness, rigors, night sweats, weight loss, anorexia * cardiac * dyspnea, chest pain, clubbing (subacute) * regurgitant murmur (new onset or increased intensity) * signs of CHF (secondary to acute MR, AR) * embolic/vascular * petechiae over legs, splinter haemorrhages (linear, reddish-brown lesion within nail bed) * Janeway lesions (painless, 5 mm, erythematous, haemorrhagic pustular lesions on soles/ palms) * focal neurological signs (CNS emboli), headache (mycotic aneurysm) splenomegaly (subacute) * microscopic haematuria, flank pain (renal emboli) ± active sediment * immune complex * Osler’s nodes (painful, raised, red/brown, 3-15 mm on digits) * glomerulonephritis * arthritis * Roth’s spots (retinal haemorrhage with pale center)

Answer 36

* serial blood cultures: 3 sets (each containing one aerobic and one anaerobic sample) collected from different sites \>1 h apart * persistent bacteremia is the hallmark of endovascular infection (such as IE) * repeat blood cultures (at least 2 sets) after 48 to 72 h of appropriate antibiotics to confirm clearance * blood work: FBC (normochromic, normocytic anemia), ESR (increased), RF (+), BUN/Cr * urinalysis (proteinuria, hematuria, red cell casts) and urine C&S * ECG: prolonged PR interval may indicate perivalvular abscess * Echo findings: vegetations, regurgitation, abscess * TTE (poor sensitivity) inadequate in 20% (obesity, COPD, chest wall deformities) * EE indicated if TTE is non-diagnostic in patients with at least possible endocarditis or if suspect prosthetic valve endocarditis or complicated endocarditis (e.g. paravalvular abscess/perforation) (~90% sensitivity)

Answer 37

* medical * usually non-urgent and can wait for confirmation of aetiology before initiating treatment: Need ID/micro consult and cardio consult * empiric antibiotic therapy if patient is unstable; administer ONLY after blood cultures have been taken * first-line empiric treatment for native valve: Gentamicin IV PLUS Benzylpenicillin 1.8 g IV q4h PLUS flucoxacillin 2g IV q4h * first line empiric treatment for prosthetic valve: gentamicin IV PLUS flucloxacillin 2g IV q4h PLUS vancomycin IV * targeted antibiotic therapy: antibiotic and duration (usually 4-6 wk) adjusted based on valve, organism, and sensitivities * monitor for complications of IE (e.g. CHF, conduction block, new emboli) and complications of antibiotics (e.g. interstitial nephritis) * prophylaxis only for high risk individuals listed above with dental procedures OR invasive procedure of the respiratory tract that involves incision or biopsy of the respiratory mucosa, such as tonsillectomy and adenoidectomy OR procedures on infected skin, skin structure, or musculoskeletal tissue * dental/respiratory: amoxicillin 2g single dose 1h prior; * skin/soft tissue: cephalexin single dose 30-60 min prior * surgical: * most common indication is refractory CHF * other indications include: valve ring abscess, fungal etiology, valve perforation, unstable prosthesis, ≥2 major emboli, antimicrobial failure (persistently positive blood cultures), mycotic aneurysm, staphylococci on a prosthetic valve

Answer 38

* unilateral dermatomal eruption occurring 3-5 d after pain and paresthesia of that dermatome; may be disseminated in Immunosuppressed (eg HIV, organ transplant) * vesicles, bullae, and pustules on an erythematous, edematous base * lesions may become eroded/ulcerated and last days to weeks * pain is can be pre-herpetic, synchronous with rash, or post-herpetic * severe post-herpetic neuralgia often occurs in elderly and may be permanent * Hutchinson’s sign: involvement of tip of nose suggests eye involvement * distribution: thoracic (50%), trigeminal (10-20%), cervical (10-20%); disseminated in HIV

Answer 39

* caused by reactivation of VZV * risk factors: immunosuppression, old age, occasionally associated with hematologic malignancy, stress

Answer 40

* none required, but can do Tzanck test, direct fluorescence antibody test, or viral culture to rule out HSV

Answer 41

* compress with normal saline, Burow’s, or betadine solution * analgesics (NSAIDs, amitriptyline) * famciclovir or valacyclovir or acyclovir for 7 d; must initiate within 72 h to be of benefit; IV acyclovir for ophthalmic or disseminated Involvement * gabapentin 300-600 mg PO tid for post-herpetic neuralgia

Answer 42

1-2 days pre-eruptions and 5 daqys post-eruption

Answer 43

Mainly airborne, but also through direct contact with vesicle fluid.

Answer 44

* Appearance: groups of skin lesions, polymorphic, from macules to papules to vesicles to crusts * Timing: 1-3 d after start of symptoms * Distribution: generalized * Significant pruritis * Enanthem: vesicular lesions which may become pustular or ulcerate

Answer 45

* Supportive : Avoid salicylates (due to risk of Reye syndrome) * Consider antivirals * Respiratory and contact isolation, report to Public Health * Prevention: varicella vaccine

Answer 46

* Skin: bacterial suprainfection, necrotizing fasciitis * CNS: acute encephalitis and cerebellar ataxia * Systemic: hepatitis, DIC * Congenital varicella syndrome if intrapartum infection

Answer 47

* non-specific: diarrhea, vomiting, fever, anorexia, headache, myalgias, abdominal cramps * bacterial and parasitic agents more common in older children (2-4 yr) * recent infectious contacts: symptoms usually begin 24-48 h after exposure

Answer 48

* not usually necessary in young children * stool analysis: leukocytes/erythrocytes suggests bacterial or parasitic etiology; pH \<6 and presence of reducing substances suggests viral etiology

Answer 49

* viral gastroenteritis usually self-limiting (lasts 3-7 d in most cases) * adverse effects related to hypovolemia, shock, tissue acidosis, and rapid onset and overcorrection of electrolyte imbalances * death in severe dehydration (rare in developed countries)

Answer 50

* most commonly caused by Staphylococcus aureus * mechanism of spread: hematogenous (most common) vs. direct-inoculation vs. contiguous focus. * risk factors: recent trauma/surgery, immunocompromised patients, DM, IV drug use, poor vascular supply, peripheral neuropathy.

Answer 51

* symptoms: pain and fever * on exam: erythema, tenderness, oedema common ± abscess/draining sinus tract; impaired function/WB

Answer 52

* workup includes: * FBC, WBC and diff, ESR, CRP, blood culture, aspirate culture/bone biopsy * Imaging: * MRI is the imaging modality of choice for demonstrating bone, bone marrow, and soft tissue nabnormalities * ^99mTc, followed by ¹¹¹In labeled white cell scan or gallium radioisotope scan * plain film * visible 8-10 d after process has begun * osteomyelitic changes on plain film * soft tissue swelling * local periosteal reaction * pockets of air (from anaerobes) may be seen in th * tissues, may also suggest necrotizing fasciitis * mottled and nonhomogeneous with a classic “moth-eaten” appearance * cortical destruction

Answer 53

Systemic inflammatory response syndrome (SIRS) requires 2 or more of the following (the definition differs for children): 1. T \>38 C or \<36 C 2. P \>90/min 3. RR \>20/min or PaCO2 \<32 mmHg 4. WCC \>12 or \>10% immature band form * sepsis: SIRS + proven or provable infection * severe sepsis: sepsis + signs of end-organ dysfunction and hypoperfusion * septic shock: severe sepsis + hypotension (\<90 mmHg sBP), despite adequate fluid resuscitation

Answer 54

* causative agents are identified in only 50-70% of cases * when organisms are identified, GP and GN organisms are the cause in 90% of cases * primary bloodstream infection or secondary bacteremia → local immune response → immune cells release pro-inflammatory cytokines → immune response spreads beyond local environment → unregulated, exaggerated systemic immune response → vasodilation and hypotension → involvement of tissues remote from the site of injury/infection resulting in multiple major organ dysfunction → periodic immunoparalysis

Answer 55

* history: fever, chills, dyspnea, cool extremities, fatigue, malaise, anxiety, confusion * physical: abnormal vitals (fever, tachypnea, tachycardia, hypotension), local signs of infection

Answer 56

* Blood: FBC UECs, BUN, LFTs, ABG, lactate, INR, PTT, FDP, blood cultures x3 * Urine: urinalysis, urine C&S and cultures of any wounds or lines * Imaging: CXR (other imaging depends on suspicion of focus of infection)

Answer 57

* respiratory support: O₂ ± intubation * cardiovascular support: IV fluids, ± norepinephrine + ICU * IV antibiotics (empirical, depends on suspected source) * start with broad spectrum antibiotics (piperacillin/tazobactam or meropenem) ± additional agents depending on patient risk factors, suspected etiology of infection, and local microbial susceptibilities (± aminoglycoside for drug-resistant GNs or vancomycin for MRSA) * narrow once susceptibilities are known * hydrocortisone IV in patients with septic shock unresponsive to fluid resuscitation and vasopressors

Answer 58

* inhalation and deposition in the lung can lead to one of the following outcomes: * immediate clearance of the pathogen * latent TB: asymptomatic infection contained by host immune defenses (represents 95% of infected people) * primary TB: symptomatic, active disease (represents 5% of infected people) * secondary TB: symptomatic reactivation of previously dormant TB (represents 5-10% of those with latent TB, most often within the first 2-3 yr of initial infection) at a pulmonary or extra-pulmonary site

Answer 59

* social and environmental factors * travel or birth in country with high TB prevalence (e.g. Asia, Latin America, Sub-Saharan Africa, Eastern Europe) * Aboriginal, crowded living conditions, low SES/homeless, IVDU * personal or occupational contact * host factors * immunocompromised/immunosuppressed (especially HIV, including extremes of age) * silicosis * chronic renal failure requiring dialysis * malignancy and chemotherapy * substance abuse (e.g. drug use, alcoholism, smoking)

Answer 60

* primary infection usually asymptomatic, although progressive primary disease may occur, especially in children and immunosuppressed patients • secondary infection/reactivation usually produces constitutional symptoms (fatigue, anorexia, night sweats, weight loss) and site-dependent symptoms * pulmonary TB * chronic productive cough ± hemoptysis * CXR consolidation or cavitation, lymphadenopathy * non-resolving pneumonia despite standard antimicrobial therapy * miliary TB * widely disseminated spread especially to lungs, abdominal organs, marrow, CNS * CXR: multiple small 2-4 mm millet seed-like lesions throughout lung * extrapulmonary TB * lymphadenitis, pleurisy, pericarditis, hepatitis, peritonitis, meningitis, osteomyelitis (vertebral = Pott’s disease), adrenal (causing Addison’s disease), renal, ovary

Answer 61

* screening for latent TB * Mantoux skin tests * diagnose prior TB exposure; can not diagnose or exclude active disease * IFN-γ release assay (IGRA): * in patients previously infected with TB, T-cells produce increased amounts of IFN-γ when re-exposed to TB antigen * detects antigen not present in the BCG vaccine or in most types of non-tuberculous- mycobacteria (NTM), therefore fewer false positives * American guidelines treat IGRAs as equivalent to the TB skin test and preferable in patients with a history of BCG vaccination or who may not return for skin test reading * diagnostic tests/investigations for active pulmonary TB * morning sputum on 3 consecutive days for acid-fast bacilli smear and culture * Bronchoavleolar lavage * CXR * nodular or alveolar infiltrates with cavitation (middle/lower lobe if primary, apical if secondary) * pleural effusion (usually unilateral and exudative) may occur independently of other radiograph abnormalities * hilar/mediastinal adenopathy (especially in children) * tuberculoma (semi-calcified well-defined solitary coin lesion 0.5-4 cm that may be mistaken for lung CA) * miliary TB * evidence of past disease: calcified hilar and mediastinal nodes, calcified pulmonary focus, pleural thickening with calcification, apical scarring

Answer 62

* empiric therapy: INH + rifampin + pyrazinamide + ethambutol + pyridoxine * pulmonary TB: INH + rifampin + pyrazinamide + ethambutol + pyridoxine x 2 mo (initiationphase), then INH + rifampin + pyridoxine x 4 mo in fully susceptible TB (continuation phase), total 6 mo * extrapulmonary TB: same regimen as pulmonary TB but increase to 12 mo in bone/joint, CNS, and miliary/disseminated TB + corticosteroids for meningitis, pericarditis * empiric treatment of suspected MDR (multidrug resistant) or XDR (extensively drug-resistant) TB requires referral to a specialist * MDR = resistance to INH and rifampin ± others * XDR = resistance to INH + rifampin + fluoroquinolone + ≥1 of injectable, second-line agents * very difficult to treat, global public health threat * suspect MDR TB if previous treatment, exposure to known MDR index case, or immigration from a high-risk area * note: TB is a reportable disease to Public Health

Answer 63

* primary prevention * airborne isolation for active pulmonary disease * BCG vaccine * _~80% effective against pediatric miliary and meningeal TB * effectiveness in adults debated (anywhere from 0-80%) * routine use rarely recommended in American population, however widely used in other countries * secondary prevention (defer in pregnancy unless mother is high risk) * likely INH-sensitive: isoniazid (INH) + pyridoxine (vit B 6 to help prevent INH-associated neuropathy) x 9 mo * likely INH-resistant: rifampin x 4 mo

Answer 64

* HIV is a retrovirus that causes progressive immune system dysfunction which predisposes patients to various opportunistic infections and malignancies * HIV virion includes an envelope (gp41 and gp120 glycoproteins), matrix (p17) and capsid (p24) enclosing 2 single-stranded copies of RNA + enzymes in its core * virion glycoproteins bind CD4 and CXCR4/CCR5 on CD4+ T lymphocytes (T-helper cells) to fuse and enter the cells * RNA converted to dsDNA by reverse transcriptase; dsDNA is integrated into host genome * virus DNA transcribed and translated using host cell machinery, post-translational modifications include proteolytic activity of virally encoded protease enzymes * newly produced virions bud out of host cell, incorporating host cell membrane; additional maturation steps are required before virion is considered infectious * exact mechanisms of CD4 depletion incompletely characterized but likely include direct viral cytopathic effects, apoptosis, increased cell turnover

Answer 65

**Acute (Infection) Retroviral Syndrome** * 40-90% experience an acute "flu-like" illness (may include fever, pharyngitis, lymphadenopathy, rash, arthralgias, myalgias, H/A, GI symptoms, oral ulcers, weight loss) 2-6 wk post-exposure lasting 10-15 d * haematologic disturbances (lymphopenia, thrombocytopenia) * 10-20% present with aseptic meningitis; HIV RNA and/or p24 may be detected in CSF * associated with a high level of plasma viremia and therefore high risk of transmission **Asymptomatic (Latent) Stage** * during latent phase, HIV infects and replicates in CD4+ T lymphocytes (lymph nodes) * normal CD4 count: 500-1,100 cells/mm 3 * CD4 count drops 60-100 cells/mm 3 per year * by 10 yr post-infection, 50% have AIDS, 30% demonstrate milder symptoms, and \<20% are asymptomatic if left untreated **AIDS Definition in United States** * CD4+ T-lymphocyte count of \<200 cells/μL OR * CD4+ T-lymphocyte percentage of total lymphocytes of \<14% OR * documentation of an AIDS-defining condition

Answer 66

* anti-HIV antibodies detectable after a median of 3 wk, virtually all by 3 mo (therefore 3 mo window period) * initial screening test (3rd generation antibody test): enzyme linked immunosorbent assay (ELISA) detects serum antibody to HIV; sensitivity \>99.5% * increasingly, combination p24 antigen/HIV antibody tests (4th generation) used for screening; improved sensitivity in early or acute infection and sensitivity/specificity approach 100% for chronic infection * confirmatory test: in positive screen, Western blot confirmation by detection of antibodies to at least two different HIV protein bands (p24, gp41, gp120/160); specificity \>99.99% * rapid (point of care) antibody tests: higher false positives, therefore need to confirm positive results with traditional serology * p24 antigen: detection by ELISA may be positive during "window period"

Answer 67

* verify positive HIV test * complete baseline history and physical exam, then follow-up every 3-6 mo * laboratory evaluation * routine CD4 count to measure status of the immune system * routine HIV-RNA levels (viral load) * also important indicator of effect of ART * baseline HIV resistance testing to guide ARV therapy * HLA-B\*5701 genetic test to screen for abacavir hypersensitivity * baseline tuberculin skin test (PPD): induration greater than 5 mm is positive * baseline serologies (hepatitis A, B, and C, syphilis, toxoplasma, CMV, VZV) * routine biochemistry and hematology, CXR * annual fasting lipid profile and fasting glucose (due to HAART side effects) * education * regular follow-up on CD4 counts and viral loads (q3-6 mo) as well as strict adherence to ART improves prognosis * prevention of further transmission through safer sex and clean needles for injection drug use * HIV superinfection (transmission of different HIV strains from another HIV+ person) does rarely occur so barrier protection during sex is still recommended * discuss importance of disclosing HIV status to partners including risk of criminal prosecution of non-disclosure in jurisdictions where applicable * connect to relevant community groups and resources * health care maintenance * assessment of psychosocial concerns and referral to psychiatry or social work if appropriate * vaccines: influenza annually, 23-valent pneumococcal every 5 yr, HBV (if not immune), HAV (if seronegative) * annual screening (PAP smear, STDs) * management of comorbid conditions and provision of general primary care

Answer 68

* recommended that all HIV+ patients initiate HAART to prevent disease progression and transmission; strength of evidence supporting that recommendation changes depending on CD4 count and sexual practices (AI evidence that CD4 \<350 should be on HAART) * patients starting HAART should be committed to treatment and understand the importance of adherence; poor compliance can lead to viral resistance; may defer treatment on the basis of clinical and psychosocial factors on case by case basis * initiate ART if opportunistic infection/malignancy, pregnancy, HIV-associated nephropathy, HIV-associated thrombocytopenia, need for hepatitis B therapy in HBV co-infected patients * consider starting treatment early if HCV co-infection, high HIV viral load, comorbid conditions (e.g. cardiovascular disease) * consider results of baseline resistance testing and complete ART history before (re-)initiating HAART * goal: keep viral load below limit of detection i.e. \<40 copies/mL (undetectable); viral load should decrease 10-fold within 4-8 wk, be undetectable by 6 mo and restore immunological function * strong evidence against intermittent HAART or ‘drug holidays’ * ART leads to 96% reduction in risk of transmitting HIV to sexual partners

Answer 69

* education, including harm-reduction * safer sexual practices: condoms for vaginal and anal sex, barriers for oral sex * harm reduction for injection drug users: avoid sharing needles * treatment of HIV+ women with HAART during the 2nd and 3rd trimester of pregnancy and AZT during delivery followed by treatment of the infant for 6 wk (decreases maternal-fetal transmission from 25% to \<3%) * universal blood and body precautions for health care workers * post-exposure prophylaxis (PEP) after occupational (e.g. needle-stick injury) and non- occupational (e.g. consensual sex, sexual assault) exposure to HIV: 2- or 3-drug regimen initiated immediately (\<72 h) after exposure and continuing for 4 wk * recent data has demonstrated efficacy of pre-exposure prophylaxis (oral PrEP or topical microbicides) in preventing HIV although additional data needed * ART associated with 96% reduction in risk of transmitting HIV to sexual partners * screening of blood and organ donation

Answer 70

* pain out of proportion to clinical findings and beyond border of erythema * oedema, ± crepitus (subcutaneous gas from anaerobes), ± fever * infection spreads rapidly * patients may rapidly become very sick (tachycardia, hypotension, lightheadedness) * late findings * skin turns dusky blue and black (secondary to thrombosis and necrosis) * induration, formation of hemorrhagic bullae

Answer 71

* a clinical/surgical diagnosis – do NOT wait for results of investigations before beginning treatment * blood and tissue C&S * serum CK (elevated CK usually means myonecrosis – a late sign) * plain film x-ray (soft tissue gas may be visualized) * surgical exploration for debridement of infected tissue

Answer 72

* Mammalian * Dog and cat: Pasteurella multocida, S. aureus, S. viridans * 80% of cat bites, 5% of dog bites become infected * amoxicillin + clavulanic acid * Human: Eikenella corrodens, S. aureus, S. viridans, oral anaerobes * amoxicillin + clavulanic acid

Answer 73

* identified in only 40-70% of cases * when cause is identified, the most common aetiology is viral * e.g. HSV, VZV, EBV, enteroviruses, CMV, West Nile, HIV, mumps, measles, rabies, polio * bacteria: L. monocytogenes, Mycobacteria, spirochetes (syphillis) * parasities: protozoa (e.g. Toxoplasma) and helminths (rare) * fungi: e.g. Cryptococcus * post-infectious (e.g. acute disseminated encephalomyelitis [ADEM])

Answer 74

* CSF: opening pressure, cell count + differential, glucose, protein, Gram stain, bacterial C&S, PCR for HSV, VZV, EBV, enteroviruses, and other less common viral etiologies * serology: may aid diagnosis of certain causes of encephalitis (e.g. West Nile virus) * imaging/neurologic studes: CT, MRI, EEG to define anatomical sites affected * invasive testing: brain tissue biopsy may be required for culture, histological examination, and immunocytochemistry (if diagnosis not clear via non-invasive means) * findings in herpes simplex encephalitis (must rule out due to high mortality) * CT/MRI: medial temporal lobe necrosis * EEG: early focal slowing, periodic discharges

Answer 75

* Large family of facultatively anaerobic Gram-negative bacilli * Found in the normal flora of animals and human, as well as soil and water * Transmission * From other animal or humans and from the inanimate environment * Arising from the body’s normal flora when opportunities are provided by medical, surgical or other therapy * Medically important genera: E. coli, Klebsiella sp., Proteus sp., Enterobacter sp., Salmonella sp., Shigella sp. And Yersinia sp.

Answer 76

* E. Coli * Salmonella sp * Shigella sp

Answer 77

* Predominantly affecting at risk hospitalised patients * Neutropenic patient – particular risk of bacteraemia * Long-stay patients (with wounds, drains, IV and urinary catheters, ventilated and multiple antibiotics) – particular infection of catheter associated UTI * Burns patients – particular risk of bacteraemia and wound infection * Patients with cystic fibrosis or other chronic lung disease – particular risk of respiratory infection, including an acute ventilator associated respiratory infection * Other risks – folliculitis and dermatitis from spas and swimming pools, otitis externa (particularly in diabetics), corneal ulcer from contaminated contact lens solutions, endopthalmitis from penetrating injury, and osteomyelitis from puncture wound through shoes into the calcaneous

Answer 78

* Fever, stiff neck, reduced consciousness * Petechial rash, a sign of septicaemia, may be present without other signs of meningitis * Septic or reactive arthritis may develop

Answer 79

* 2.4g benzylpenicillin IM before hospitalisation if high suspicion on clinical grounds * Give dexamethasone 10mg IV before or with the first dose of antibiotics, then 6-hourly * Plus ceftriaxone 4g IV daily

Answer 80

Vancomycin

Answer 81

Ciprofloxacin

Answer 82

Metronidazole.

Answer 83

* Lincomycins

Answer 84

* Tetracyclines * Macrolides * Aminoglycosides * Chloramphenicol.

Answer 85

* Sulphonamides/trimethoprim * Quinolones * Metronidazole.

Answer 86

* Penicillins * Vancomycin * Cephalosporins * Macrolides

Answer 87

* reservoir: infected humans and other mammals * food/waterborne (especially in the Rockies) and fecal-oral transmission of infectious cysts * risk factors: travel, camping, institutions, day care centers, MSM

Answer 88

* giardiasis (“beaver fever”) * symptoms vary from asymptomatic to self-limited mild watery diarrhea to malabsorption syndrome (chronic giardiasis where the parasite coats small intestine and thus prevents fat absorption) * nausea, malaise, abdominal cramps, bloating, flatulence, fatigue, weight loss, steatorrhea * no haematochezia (no invasion into intestinal wall), no mucus in stool

Answer 89

* multiple stool samples (daily x 3 d) for microscopy - 90% sensitivity (1 stool sample - 50% sensitvity, hense 3 is needed), detects cysts and oocytes * stool antigen used occasionally * occasionally small bowel aspirate or biopsy

Answer 90

* metronidazole * good personal hygiene and sanitation, water purification (iodine better than chlorination), outbreak investigation

Answer 91

Vanc or metronidazole

Answer 92

* Clindamycin * cephalosporins * amoxicillin

Answer 93

Clarithromycin or erythromycin. Alternatively tetracycline or doxycycline.

Answer 94

Mycoplasma pneumoniae

Answer 95

* Haemolytic anaemia: s associated with the presence of cold agglutinins, found in up to 50% of cases of Mycoplasma pneumonia. Diagnosis is based on demonstration of anti-Mycoplasma antibodies in paired sera. * Renal failure * Hepatitis * Myocarditis * Meningism and meningitis * Transverse myelitis * Cerebellar ataxia. * Cutaneous manifestations include erythema multiforme.