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COMLEX Level 1 (Comprehensive Osteopathic
Medical Licensing Examination of the United
States – Level 1) QUESTIONS AND DETAILED
SOLUTIONS
COMLEX Level 1 (Comprehensive Osteopathic Medical Licensing Examination of the United States –
Level 1) question set, written to your specifications. This exam covers the core biomedical and
osteopathic principles tested at the end of the second year of medical school.
ACTUAL EXAM COVERAGE – SUMMARIZED POINT FORM
• Osteopathic Principles and Practices (OPP): Somatic dysfunction (TART – tenderness,
asymmetry, range of motion, tissue texture changes), Fryette’s principles (Type I & II
mechanics), Chapman’s reflexes (viscerosomatic relationships), viscerosomatic reflexes,
somaticovisceral reflexes, facilitated segment, paraspinal muscle hypertonicity, myofascial
release, high-velocity low-amplitude (HVLA) thrust, counterstrain (strain/counterstrain), muscle
energy, facilitated positional release, cranial osteopathy, Still technique, ligamentous articular
strain (LAS), treatment of ribs (bucket handle, pump handle, caliper motion), sacral diagnosis (L5
motion, sacral base, sulci, ILA), innominate diagnosis (ASIS, PSIS, pubic symphysis)
• Biochemistry: Enzyme kinetics (Michaelis-Menten, Lineweaver-Burk, Vmax, Km, competitive vs
noncompetitive inhibition), glycolysis (key enzymes: hexokinase, PFK-1, pyruvate kinase,
products, regulation), gluconeogenesis (key enzymes: pyruvate carboxylase, PEPCK, FBPase-1,
G6Pase), TCA cycle (isocitrate dehydrogenase, alpha-ketoglutarate dehydrogenase, succinate
dehydrogenase), electron transport chain (complexes I-IV, ATP synthase, NADH vs FADH2),
glycogenolysis/glycogenesis, pentose phosphate pathway (G6PD), fatty acid oxidation (carnitine
shuttle, beta-oxidation), ketogenesis/ketolysis, urea cycle, amino acid metabolism (PKU,
alkaptonuria, maple syrup urine disease), nucleotide metabolism (Lesch-Nyhan, OTC deficiency),
vitamins (B1, B2, B3, B6, B9, B12, C, A, D, E, K, deficiencies)
• Microbiology & Immunology: Gram-positive cocci (Staph aureus – coagulase positive, protein A;
Staph epidermidis; Strep pyogenes (GAS) – M protein, ASO; Strep agalactiae (GBS); Strep
pneumoniae – optochin sensitive, bile solubility; Enterococcus), Gram-positive rods (Bacillus
anthracis, Listeria, Clostridium tetani/perfringens/difficile/botulinum, Corynebacterium
diphtheriae), Gram-negative cocci (Neisseria meningitidis, Neisseria gonorrhoeae), Gram-
negative rods (E. coli, Klebsiella, Proteus, Pseudomonas, Salmonella, Shigella, Yersinia, Vibrio,
Campylobacter, Helicobacter, Legionella, Bordetella, Haemophilus, Brucella, Francisella),
Spirochetes (Treponema pallidum, Borrelia burgdorferi, Leptospira), Mycobacteria (TB – acid-
fast, Runyon groups, leprosy), Viruses (DNA vs RNA, naked vs enveloped), Herpesviruses (HSV-
1/2, VZV, EBV, CMV, HHV-6, HHV-8), Hepatitis viruses (HAV, HBV, HCV, HDV, HEV), Retroviruses
(HIV – p24, gp120, gp41, reverse transcriptase), Respiratory viruses (RSV, influenza,
parainfluenza, adenovirus, rhinovirus, SARS-CoV-2), GI viruses (rotavirus, norovirus), CNS viruses
(polio, rabies, West Nile, La Crosse, arboviruses), Antifungals (azoles, polyenes, echinocandins,
flucytosine), Antivirals (acyclovir, ganciclovir, oseltamivir, HAART), Antibiotics (beta-lactams,
vancomycin, macrolides, tetracyclines, aminoglycosides, quinolones, sulfonamides,
metronidazole), Antimicrobial resistance (MRSA, VRE, ESBL, KPC, NDM-1), Innate immunity
(complement, phagocytes, NK cells, PRRs, TLRs), Adaptive immunity (B cells, T cells, MHC I/II,
CD4/CD8), Hypersensitivity (Type I-IV), Autoimmunity (SLE, RA, MS, type 1 DM, Graves,
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Hashimoto), Immunodeficiencies (SCID, DiGeorge, CVID, IgA deficiency, Hyper-IgM, Wiskott-
Aldrich, Ataxia-telangiectasia, CGD, leukocyte adhesion deficiency)
• Pharmacology: Pharmacokinetics (absorption, distribution, metabolism – CYP450, Phase I/II,
elimination), Pharmacodynamics (agonists, antagonists, partial agonists, inverse agonists,
therapeutic index, ED50, TD50), Autonomic pharmacology (cholinergic agonists/antagonists,
adrenergic agonists/antagonists, ganglionic blockers, neuromuscular blockers), CV drugs (beta-
blockers, CCBs, ACE inhibitors, ARBs, nitrates, antiarrhythmics, diuretics, anticoagulants,
antiplatelets, thrombolytics), CNS drugs (SSRIs, SNRIs, MAOIs, TCAs, antipsychotics – typical vs
atypical, benzodiazepines, barbiturates, anticonvulsants, opioids, anesthetics), Respiratory drugs
(beta-2 agonists, anticholinergics, steroids, leukotriene modifiers), Endocrine drugs (insulin,
sulfonylureas, metformin, TZD, GLP-1 agonists, SGLT2 inhibitors, thyroid hormone, antithyroid
drugs, corticosteroids), Antibiotics (mechanisms, resistance), Antineoplastics (MTX, 5-FU,
cyclophosphamide, doxorubicin, vincristine, cisplatin, tamoxifen, imatinib)
• Pathology: Cellular injury (necrosis – coagulative, liquefactive, caseous, fat, fibrinoid; apoptosis
– intrinsic/extrinsic pathways), inflammation (acute – neutrophils, vasodilation, chemotaxis;
chronic – macrophages, lymphocytes, granulomas), hemodynamic disorders (edema,
hyperemia, congestion, hemorrhage, thrombosis (Virchow’s triad), embolism
(thromboembolism, fat, air, amniotic), infarction (red vs white), shock (hypovolemic,
cardiogenic, distributive, obstructive)), neoplasia (benign vs malignant, carcinoma vs sarcoma,
metastasis, TNM staging, tumor markers (PSA, AFP, CEA, CA-125, hCG, calcitonin), oncogenes
(RAS, MYC, HER2/neu), tumor suppressors (p53, Rb, APC, BRCA1/2)), genetics (Mendelian
disorders – AD, AR, X-linked, mitochondrial, imprinting, trinucleotide repeats, aneuploidy,
structural abnormalities), immunopathology (amyloidosis, hypersensitivity), vascular pathology
(atherosclerosis, aneurysms, vasculitis), cardiac pathology (MI, heart failure, cardiomyopathies,
valvular diseases, endocarditis), respiratory pathology (COPD, asthma, pneumonia, TB, lung
cancer), GI pathology (GERD, peptic ulcer, IBD (Crohn vs UC), hepatitis, cirrhosis, pancreatic
cancer, colorectal cancer), renal pathology (nephritic vs nephrotic syndromes, ATN,
pyelonephritis, renal cell carcinoma, Wilms tumor), reproductive pathology (prostate cancer,
BPH, testicular cancer, ovarian tumors, endometrial cancer, cervical dysplasia), endocrine
pathology (DM type 1/2, thyroiditis, thyroid neoplasms, adrenal disorders), neuropathology
(stroke, Alzheimer, Parkinson, Huntington, MS, gliomas)
• Physiology: Cellular physiology (membrane potential, action potentials, ion channels, synapses,
second messengers), Neurophysiology (CNS, PNS, ANS, reflexes, sensory/motor pathways,
special senses), Cardiovascular (cardiac action potentials, ECG, cardiac cycle (Wiggers diagram),
cardiac output (HR × SV), preload, afterload, contractility, Frank-Starling, blood pressure
regulation (baroreceptors, RAAS, ANP), microcirculation, autoregulation), Respiratory (lung
volumes/capacities, ventilation/perfusion (V/Q) matching, diffusion capacity, oxygen-
hemoglobin dissociation curve (Bohr effect, Haldane effect), control of breathing
(central/peripheral chemoreceptors), acid-base balance (respiratory acidosis/alkalosis,
metabolic acidosis/alkalosis, anion gap, delta ratio)), Renal (GFR, RPF, filtration fraction,
clearance, autoregulation (myogenic, TGF), tubular function (reabsorption/secretion),
countercurrent multiplier, RAAS, acid-base handling, diuretics sites of action), GI (motility
(peristalsis, migrating motor complex), digestion/absorption (carbs, proteins, fats), hormones
(gastrin, CCK, secretin, GIP, motilin, ghrelin), liver function, biliary system), Endocrine
(hypothalamus-pituitary axis (portal system), thyroid axis (TRH/TSH/T3/T4), adrenal axis
(CRH/ACTH/cortisol, aldosterone (RAAS)), pancreatic hormones (insulin/glucagon), calcium
homeostasis (PTH, calcitonin, vitamin D), reproductive hormones (GnRH, FSH, LH, estrogen,
progesterone, testosterone), growth hormone), MSK (muscle contraction (sliding filament,
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cross-bridge), excitation-contraction coupling (ryanodine receptor, calcium release), motor unit,
twitch/tetanus, muscle fiber types, smooth muscle)
• Osteopathic Diagnosis & Manipulation (COMLEX Specific): Sacral mechanics (L5 rotation, sacral
base motion – flexion/extension, torsion (R vs L), unilateral flexion/dysfunction), Innominate
diagnosis (anterior/posterior rotation, inflare/outflare, superior/inferior pubic shear), Lumbar
spine (neutral vs non-neutral mechanics – Fryette’s), Thoracic spine (T1-T4, T5-T10, T11-L1, rib
diagnosis (inhaled/exhaled restriction), cervical spine (diagnosis of C0-C1, C1-C2, lower cervical),
Chapman reflex points (locations, organ correlation), Viscerosomatic reflexes (spinal levels for
heart (T1-T5), lungs (T2-T7), gallbladder (T5-T9), appendix (T10-L1), kidneys (T10-L1), uterus
(T10-L2), etc.), Counterstrain tender points (treatment by shortening the muscle to its point of
ease), Muscle energy (isometric contraction followed by relaxation, engage restrictive barrier),
HVLA (thrust to restrictive barrier, cavitation), Facilitated segment (paraspinal muscle
hypertonicity, treatment via inhibition, myofascial release), Cranial osteopathy (cranial rhythmic
impulse, sphenobasilar synchondrosis motion, Sutherland’s sign, vault holds)
1. A 65-year-old male presents with chest pain that radiates to the left arm, diaphoresis, and nausea. His
ECG shows ST-segment elevation in leads II, III, and aVF. Which coronary artery is most likely occluded?
A) Left anterior descending (LAD)
B) Left circumflex (LCx)
C) Right coronary artery (RCA)
D) Posterior descending artery (PDA)
Correct: C – Leads II, III, aVF correspond to the inferior wall of the heart, which is supplied by the right
coronary artery (RCA) in most individuals.
2. A newborn presents with projectile, non-bilious vomiting after feeding. An olive-shaped mass is
palpated in the right upper quadrant. What is the most likely diagnosis, and what is the associated
metabolic disturbance?
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A) Intussusception leading to hypokalemia
B) Pyloric stenosis leading to hypochloremic metabolic alkalosis
C) Malrotation leading to hypernatremia
D) Hirschsprung disease leading to hyperkalemia
Correct: B – Hypertrophic pyloric stenosis causes gastric outlet obstruction with loss of hydrochloric
acid, resulting in hypochloremic metabolic alkalosis.
3. A patient with a history of IV drug use presents with fever, back pain, and a new regurgitant murmur.
Transesophageal echocardiography shows a vegetation on the tricuspid valve. What is the most likely
causative organism?
A) Streptococcus viridans
B) Staphylococcus aureus
C) Enterococcus faecalis
D) Coxiella burnetii
Correct: B – Staphylococcus aureus is the most common cause of acute infective endocarditis in IV drug
users, frequently affecting the tricuspid valve.
COMLEX Level 1 (Comprehensive Osteopathic
Medical Licensing Examination of the United
States – Level 1) QUESTIONS AND DETAILED
SOLUTIONS
COMLEX Level 1 (Comprehensive Osteopathic Medical Licensing Examination of the United States –
Level 1) question set, written to your specifications. This exam covers the core biomedical and
osteopathic principles tested at the end of the second year of medical school.
ACTUAL EXAM COVERAGE – SUMMARIZED POINT FORM
• Osteopathic Principles and Practices (OPP): Somatic dysfunction (TART – tenderness,
asymmetry, range of motion, tissue texture changes), Fryette’s principles (Type I & II
mechanics), Chapman’s reflexes (viscerosomatic relationships), viscerosomatic reflexes,
somaticovisceral reflexes, facilitated segment, paraspinal muscle hypertonicity, myofascial
release, high-velocity low-amplitude (HVLA) thrust, counterstrain (strain/counterstrain), muscle
energy, facilitated positional release, cranial osteopathy, Still technique, ligamentous articular
strain (LAS), treatment of ribs (bucket handle, pump handle, caliper motion), sacral diagnosis (L5
motion, sacral base, sulci, ILA), innominate diagnosis (ASIS, PSIS, pubic symphysis)
• Biochemistry: Enzyme kinetics (Michaelis-Menten, Lineweaver-Burk, Vmax, Km, competitive vs
noncompetitive inhibition), glycolysis (key enzymes: hexokinase, PFK-1, pyruvate kinase,
products, regulation), gluconeogenesis (key enzymes: pyruvate carboxylase, PEPCK, FBPase-1,
G6Pase), TCA cycle (isocitrate dehydrogenase, alpha-ketoglutarate dehydrogenase, succinate
dehydrogenase), electron transport chain (complexes I-IV, ATP synthase, NADH vs FADH2),
glycogenolysis/glycogenesis, pentose phosphate pathway (G6PD), fatty acid oxidation (carnitine
shuttle, beta-oxidation), ketogenesis/ketolysis, urea cycle, amino acid metabolism (PKU,
alkaptonuria, maple syrup urine disease), nucleotide metabolism (Lesch-Nyhan, OTC deficiency),
vitamins (B1, B2, B3, B6, B9, B12, C, A, D, E, K, deficiencies)
• Microbiology & Immunology: Gram-positive cocci (Staph aureus – coagulase positive, protein A;
Staph epidermidis; Strep pyogenes (GAS) – M protein, ASO; Strep agalactiae (GBS); Strep
pneumoniae – optochin sensitive, bile solubility; Enterococcus), Gram-positive rods (Bacillus
anthracis, Listeria, Clostridium tetani/perfringens/difficile/botulinum, Corynebacterium
diphtheriae), Gram-negative cocci (Neisseria meningitidis, Neisseria gonorrhoeae), Gram-
negative rods (E. coli, Klebsiella, Proteus, Pseudomonas, Salmonella, Shigella, Yersinia, Vibrio,
Campylobacter, Helicobacter, Legionella, Bordetella, Haemophilus, Brucella, Francisella),
Spirochetes (Treponema pallidum, Borrelia burgdorferi, Leptospira), Mycobacteria (TB – acid-
fast, Runyon groups, leprosy), Viruses (DNA vs RNA, naked vs enveloped), Herpesviruses (HSV-
1/2, VZV, EBV, CMV, HHV-6, HHV-8), Hepatitis viruses (HAV, HBV, HCV, HDV, HEV), Retroviruses
(HIV – p24, gp120, gp41, reverse transcriptase), Respiratory viruses (RSV, influenza,
parainfluenza, adenovirus, rhinovirus, SARS-CoV-2), GI viruses (rotavirus, norovirus), CNS viruses
(polio, rabies, West Nile, La Crosse, arboviruses), Antifungals (azoles, polyenes, echinocandins,
flucytosine), Antivirals (acyclovir, ganciclovir, oseltamivir, HAART), Antibiotics (beta-lactams,
vancomycin, macrolides, tetracyclines, aminoglycosides, quinolones, sulfonamides,
metronidazole), Antimicrobial resistance (MRSA, VRE, ESBL, KPC, NDM-1), Innate immunity
(complement, phagocytes, NK cells, PRRs, TLRs), Adaptive immunity (B cells, T cells, MHC I/II,
CD4/CD8), Hypersensitivity (Type I-IV), Autoimmunity (SLE, RA, MS, type 1 DM, Graves,
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Hashimoto), Immunodeficiencies (SCID, DiGeorge, CVID, IgA deficiency, Hyper-IgM, Wiskott-
Aldrich, Ataxia-telangiectasia, CGD, leukocyte adhesion deficiency)
• Pharmacology: Pharmacokinetics (absorption, distribution, metabolism – CYP450, Phase I/II,
elimination), Pharmacodynamics (agonists, antagonists, partial agonists, inverse agonists,
therapeutic index, ED50, TD50), Autonomic pharmacology (cholinergic agonists/antagonists,
adrenergic agonists/antagonists, ganglionic blockers, neuromuscular blockers), CV drugs (beta-
blockers, CCBs, ACE inhibitors, ARBs, nitrates, antiarrhythmics, diuretics, anticoagulants,
antiplatelets, thrombolytics), CNS drugs (SSRIs, SNRIs, MAOIs, TCAs, antipsychotics – typical vs
atypical, benzodiazepines, barbiturates, anticonvulsants, opioids, anesthetics), Respiratory drugs
(beta-2 agonists, anticholinergics, steroids, leukotriene modifiers), Endocrine drugs (insulin,
sulfonylureas, metformin, TZD, GLP-1 agonists, SGLT2 inhibitors, thyroid hormone, antithyroid
drugs, corticosteroids), Antibiotics (mechanisms, resistance), Antineoplastics (MTX, 5-FU,
cyclophosphamide, doxorubicin, vincristine, cisplatin, tamoxifen, imatinib)
• Pathology: Cellular injury (necrosis – coagulative, liquefactive, caseous, fat, fibrinoid; apoptosis
– intrinsic/extrinsic pathways), inflammation (acute – neutrophils, vasodilation, chemotaxis;
chronic – macrophages, lymphocytes, granulomas), hemodynamic disorders (edema,
hyperemia, congestion, hemorrhage, thrombosis (Virchow’s triad), embolism
(thromboembolism, fat, air, amniotic), infarction (red vs white), shock (hypovolemic,
cardiogenic, distributive, obstructive)), neoplasia (benign vs malignant, carcinoma vs sarcoma,
metastasis, TNM staging, tumor markers (PSA, AFP, CEA, CA-125, hCG, calcitonin), oncogenes
(RAS, MYC, HER2/neu), tumor suppressors (p53, Rb, APC, BRCA1/2)), genetics (Mendelian
disorders – AD, AR, X-linked, mitochondrial, imprinting, trinucleotide repeats, aneuploidy,
structural abnormalities), immunopathology (amyloidosis, hypersensitivity), vascular pathology
(atherosclerosis, aneurysms, vasculitis), cardiac pathology (MI, heart failure, cardiomyopathies,
valvular diseases, endocarditis), respiratory pathology (COPD, asthma, pneumonia, TB, lung
cancer), GI pathology (GERD, peptic ulcer, IBD (Crohn vs UC), hepatitis, cirrhosis, pancreatic
cancer, colorectal cancer), renal pathology (nephritic vs nephrotic syndromes, ATN,
pyelonephritis, renal cell carcinoma, Wilms tumor), reproductive pathology (prostate cancer,
BPH, testicular cancer, ovarian tumors, endometrial cancer, cervical dysplasia), endocrine
pathology (DM type 1/2, thyroiditis, thyroid neoplasms, adrenal disorders), neuropathology
(stroke, Alzheimer, Parkinson, Huntington, MS, gliomas)
• Physiology: Cellular physiology (membrane potential, action potentials, ion channels, synapses,
second messengers), Neurophysiology (CNS, PNS, ANS, reflexes, sensory/motor pathways,
special senses), Cardiovascular (cardiac action potentials, ECG, cardiac cycle (Wiggers diagram),
cardiac output (HR × SV), preload, afterload, contractility, Frank-Starling, blood pressure
regulation (baroreceptors, RAAS, ANP), microcirculation, autoregulation), Respiratory (lung
volumes/capacities, ventilation/perfusion (V/Q) matching, diffusion capacity, oxygen-
hemoglobin dissociation curve (Bohr effect, Haldane effect), control of breathing
(central/peripheral chemoreceptors), acid-base balance (respiratory acidosis/alkalosis,
metabolic acidosis/alkalosis, anion gap, delta ratio)), Renal (GFR, RPF, filtration fraction,
clearance, autoregulation (myogenic, TGF), tubular function (reabsorption/secretion),
countercurrent multiplier, RAAS, acid-base handling, diuretics sites of action), GI (motility
(peristalsis, migrating motor complex), digestion/absorption (carbs, proteins, fats), hormones
(gastrin, CCK, secretin, GIP, motilin, ghrelin), liver function, biliary system), Endocrine
(hypothalamus-pituitary axis (portal system), thyroid axis (TRH/TSH/T3/T4), adrenal axis
(CRH/ACTH/cortisol, aldosterone (RAAS)), pancreatic hormones (insulin/glucagon), calcium
homeostasis (PTH, calcitonin, vitamin D), reproductive hormones (GnRH, FSH, LH, estrogen,
progesterone, testosterone), growth hormone), MSK (muscle contraction (sliding filament,
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cross-bridge), excitation-contraction coupling (ryanodine receptor, calcium release), motor unit,
twitch/tetanus, muscle fiber types, smooth muscle)
• Osteopathic Diagnosis & Manipulation (COMLEX Specific): Sacral mechanics (L5 rotation, sacral
base motion – flexion/extension, torsion (R vs L), unilateral flexion/dysfunction), Innominate
diagnosis (anterior/posterior rotation, inflare/outflare, superior/inferior pubic shear), Lumbar
spine (neutral vs non-neutral mechanics – Fryette’s), Thoracic spine (T1-T4, T5-T10, T11-L1, rib
diagnosis (inhaled/exhaled restriction), cervical spine (diagnosis of C0-C1, C1-C2, lower cervical),
Chapman reflex points (locations, organ correlation), Viscerosomatic reflexes (spinal levels for
heart (T1-T5), lungs (T2-T7), gallbladder (T5-T9), appendix (T10-L1), kidneys (T10-L1), uterus
(T10-L2), etc.), Counterstrain tender points (treatment by shortening the muscle to its point of
ease), Muscle energy (isometric contraction followed by relaxation, engage restrictive barrier),
HVLA (thrust to restrictive barrier, cavitation), Facilitated segment (paraspinal muscle
hypertonicity, treatment via inhibition, myofascial release), Cranial osteopathy (cranial rhythmic
impulse, sphenobasilar synchondrosis motion, Sutherland’s sign, vault holds)
1. A 65-year-old male presents with chest pain that radiates to the left arm, diaphoresis, and nausea. His
ECG shows ST-segment elevation in leads II, III, and aVF. Which coronary artery is most likely occluded?
A) Left anterior descending (LAD)
B) Left circumflex (LCx)
C) Right coronary artery (RCA)
D) Posterior descending artery (PDA)
Correct: C – Leads II, III, aVF correspond to the inferior wall of the heart, which is supplied by the right
coronary artery (RCA) in most individuals.
2. A newborn presents with projectile, non-bilious vomiting after feeding. An olive-shaped mass is
palpated in the right upper quadrant. What is the most likely diagnosis, and what is the associated
metabolic disturbance?
, Page 4 of 138
A) Intussusception leading to hypokalemia
B) Pyloric stenosis leading to hypochloremic metabolic alkalosis
C) Malrotation leading to hypernatremia
D) Hirschsprung disease leading to hyperkalemia
Correct: B – Hypertrophic pyloric stenosis causes gastric outlet obstruction with loss of hydrochloric
acid, resulting in hypochloremic metabolic alkalosis.
3. A patient with a history of IV drug use presents with fever, back pain, and a new regurgitant murmur.
Transesophageal echocardiography shows a vegetation on the tricuspid valve. What is the most likely
causative organism?
A) Streptococcus viridans
B) Staphylococcus aureus
C) Enterococcus faecalis
D) Coxiella burnetii
Correct: B – Staphylococcus aureus is the most common cause of acute infective endocarditis in IV drug
users, frequently affecting the tricuspid valve.
