3.28 Klebsiella Pneumoniae Microbiology review for the USMLE Step 1 Exam Klebsiella pneumoniae is a lactose-fermenting, gram-negative bacilli that causes pneumonia and is part of the normal GI flora in humans. It causes infection when introduced to the respiratory tract and is commonly found in hospitals, making it a common cause of nosocomial pneumonia. Risk factors for klebsiella pneumonia include alcoholism and diabetes. Symptoms of klebsiella pneumonia include cough, fever, pleuritic chest p...
Mar 24, 2023•5 min•Season 3Ep. 28
3.27 Chlamydia Species Microbiology review for the USMLE Step 1 exam Chlamydia is a gram-negative bacteria that is an obligate intracellular organism. It has a two-part life cycle involving the reticular body (active form) and elementary body (inactive form). There are three main species of chlamydia that cause human infections: chlamydia trachomatis, chlamydia pneumoniae, and chlamydia psittaci. Chlamydia trachomatis is the most common sexually transmitted infection in the US and causes genital...
Mar 23, 2023•7 min•Season 3Ep. 27
3.26 Pseudomonas Aeruginosa Microbiology review for the USMLE Step 1 Exam Pseudomonas aeruginosa is an encapsulated gram-negative oxidase positive rod that causes a variety of diseases. It can be found in soil, hospitals, and water, and it particularly likes water. P. aeruginosa can enter the body through contact with water, inhalation of respiratory droplets, or by medical equipment. The symptoms of infections caused by P. aeruginosa are caused by the toxins it secretes, including phospholipase...
Mar 17, 2023•9 min•Season 3Ep. 26
3.25 Proteus Species Microbiology review for the USMLE Step 1 exam Proteus species are gram-negative rods that cause hospital acquired urinary tract infections They have swarming motility and can move quickly in a coordinated fashion across surfaces due to their numerous flagella They can self-elongate and secrete a sticky polysaccharide when in contact with solid surfaces, allowing for attachment and easy motility Proteus mirabilis and Proteus vulgaris are the two main species that cause infect...
Mar 15, 2023•6 min•Season 3Ep. 25
3.24 Salmonella Species Microbiology review for the USMLE Step 1 Exam Salmonella are gram-negative bacteria that cause gastrointestinal disease. They have flagella that enable them to move around and infect cells, and can live inside macrophages. There are two categories of salmonella species: typhoidal and non-typhoidal. Typhoidal salmonella, such as salmonella typhi, cause typhoid fever and are usually acquired through contaminated water. Non-typhoidal salmonella, such as salmonella enteritidi...
Mar 13, 2023•7 min•Season 3Ep. 24
3.23 Yersinia Species Microbiology review for the USMLE Step 1 Exam Yersinia are gram-negative, non-motile bacteria that cause zoonotic diseases. Yersinia produce urease enzyme to survive in the stomach and are facultative intracellular bugs. Three species of yersinia causing disease in humans are Yersinia pestis, Yersinia enterocolitica, and Yersinia pseudotuberculosis. The Yersinia species inhibit phagocytosis, the capsule contains F1 and V proteins and the injectosome injects Yersinia outer p...
Mar 10, 2023•9 min•Season 3Ep. 23
3.22 Escherichia Coli (E. Coli) Microbiology review for the USMLE Step 1 Exam Esherichia coli (E. coli) is a lactose-fermenting, gram-negative rod causing various diseases, ranging from mild gastroenteritis to septic shock. E. coli diseases can be divided into two categories: intestinal infections and extraintestinal infections (outside the GI system). E. coli is part of the normal flora in the human GI tract, but some strains are pathogenic. Four pathogenic strains of E. coli are Entertoxigenic...
Mar 08, 2023•14 min•Season 3Ep. 22
2.22 Tuberculosis Pulmonary system review for the USMLE Step 1 Exam Tuberculosis is caused by Mycobacterium tuberculosis bacteria and mainly affects the lungs. It is more common in developing countries, with India, Indonesia, China, Nigeria, Pakistan, and South Africa having the most TB deaths worldwide. TB is spread through inhaling infected aerosolized droplets, making crowded places hotspots for TB spread. Primary TB infection occurs when a person inhales infected droplets and the bacteria be...
Mar 05, 2023•6 min•Season 2Ep. 22
2.21 Pneumonia: Lobar, Broncho, and Interstitial Pulmonary system review for the USMLE Step 1 Exam Pneumonia is an infection of the lung parenchyma that deals with gas exchange Three classic patterns of pneumonia: lobar, bronchopneumonia, and interstitial pneumonia Lobar pneumonia involves a single lobe of the lung and has four stages: congestion, red hepatization, gray hepatization, and resolution Most commonly associated with strep pneumoniae, also caused by Legionella and Klebsiella Bronchopn...
Mar 04, 2023•5 min•Season 2Ep. 21
2.20 Pneumothorax Pulmonary system review for the USMLE Step 1 Exam Pneumothorax is a collection of air outside the lung in the pleural cavity, caused by a hole in the pleurae that allows air to infiltrate and disturb normal respiratory function. There are three categories of causes: primary spontaneous, secondary spontaneous, and trauma. Trauma, such as blunt force or penetrating wounds, is the most common cause, as well as iatrogenic causes like transthoracic needle aspiration and central veno...
Mar 04, 2023•9 min•Season 2Ep. 20
2.19 Pleural Effusions: Transudate vs Exudate Pulmonary system review for the USMLE Step 1 Exam Pleural effusion is an abnormal accumulation of fluid in the pleural cavity. Pleural effusions can be characterized as either exudative or transudative based on the content of the extra fluid. Exudative effusions have high protein and lactate dehydrogenase content, while transudative effusions have low protein and lactate dehydrogenase content. Pleural exudates are commonly caused by lung infections, ...
Mar 03, 2023•5 min•Season 2Ep. 19
2.18 Digital Clubbing Pulmonary system review for the USMLE Step 1 Exam Digital clubbing is the enlargement of the ends of fingers and toes due to growth of connective tissue between the nail matrix and the distal portion of the digit. It is defined quantitatively as an increased angle between nail bed and nail plate (> 180°). Digital clubbing is caused by an interaction between platelets, megakaryocytes, and the growth factors platelet derived growth factor (PDGF) and vascular endothelial gr...
Mar 03, 2023•3 min•Season 2Ep. 18
2.17 Pickwickian Syndrome Pulmonary system review for the USMLE Step 1 Exam Pickwickian Syndrome is also called obesity hypoventilation syndrome Characterized by daytime hypoventilation leading to hypercapnia Often occurs in individuals with a BMI over 30 Excess fat puts pressure on lungs and reduces ability to fully inflate Reduction in ventilatory drive may also cause hypercapnia Typical patient presents with obesity, daytime sleepiness, and symptoms consistent with obstructive sleep apnea Dia...
Mar 01, 2023•3 min•Season 2Ep. 17
2.16 Sleep Apnea Pulmonary system review for the USMLE Step 1 Exam Sleep apnea is the repeated severe decrease or cessation of airflow into the lungs for more than 10 seconds during sleep, which causes the person to stop breathing for more than 10 seconds while they’re sleeping. There are two types of sleep apnea: obstructive sleep apnea and central sleep apnea. Obstructive sleep apnea occurs when the airway collapses during sleep, and it is more likely to be associated with snoring, gasping, an...
Mar 01, 2023•8 min•Season 2Ep. 16
2.15 Pulmonary Hypertension Pulmonary system review for the USMLE Step 1 Exam Pulmonary hypertension is elevated blood pressure within the pulmonary arteries at rest, defined as a mean pulmonary artery pressure above 20 mmHg. Primary pulmonary hypertension is high blood pressure in the pulmonary arteries that is not caused by some underlying disease, while secondary pulmonary hypertension is high blood pressure caused by an underlying condition. Common underlying conditions for secondary pulmona...
Feb 27, 2023•9 min•Season 2Ep. 15
2.14 Acute Respiratory Distress Syndrome (ARDS) Pulmonary system review for the USMLE Step 1 Exam Acute respiratory distress syndrome (ARDS) is an acute, diffuse, inflammatory form of lung injury that is life-threatening for patients. ARDS is a response from the lungs to severe injury, most commonly caused by sepsis, but can also be caused by pneumonia, trauma, drowning, toxin inhalation, and pancreatitis. The lung injury from sepsis causes systemic inflammation, damaging lung tissue and causing...
Feb 27, 2023•7 min•Season 2Ep. 14
2.13 Sarcoidosis Pulmonary system review for the USMLE Step 1 Exam Sarcoidosis is a multisystem inflammatory disorder with non-caseating granulomas in various organs Most commonly affects the lungs and causes restrictive lung disease Classic patient is a young black female in her 20-30s, but can affect any gender or race Symptoms vary depending on which organs are affected, and can include uveitis, skin lesions, joint pain, and swollen lymph nodes Bilateral hilar lymphadenopathy is a classic che...
Feb 26, 2023•5 min•Season 2Ep. 13
3.21 H. Pylori Microbiology review for the USMLE Step 1 exam Helicobacter Pylori (H. Pylori) is a gram-negative, comma-shaped bacteria that causes chronic gastritis Estimated that 50% of people worldwide are infected with H. Pylori; higher in developing countries, lower in developed countries More common in populations with lower socioeconomic status and in crowded conditions with poor hygiene Spread through oral-oral or fecal-oral routes Colonizes the antrum of the stomach Produces urease that ...
Feb 15, 2023•6 min•Season 3Ep. 21
3.20 Vibrio Species Microbiology review for the USMLE Step 1 Exam Vibrio species are gram negative comma-shaped rods with a single flagellum, allowing them to move quickly Two main species that cause human infections: Vibrio cholerae and Vibrio vulnificus Vibrio cholerae causes foodborne disease called cholera through cholera toxin secretion, spread through the fecal-oral route in developing countries Cholera is characterized by watery, mucinous diarrhea, if left untreated can lead to hypovolemi...
Feb 13, 2023•8 min•Season 3Ep. 20
3.19 Campylobacter Jejuni Microbiology review for the USMLE Step 1 exam Campylobacter jejuni is a gram-negative, comma-shaped bacteria that causes diarrheal illness It is the most common cause of bacterial diarrhea in the US It can be distinguished from other gram-negative, comma-shaped bacteria by its desired culture temperature of 42C/107F It is mostly acquired through consumption of raw milk, undercooked poultry, and contaminated water 90% of cases in the US occur during the summer months, li...
Feb 10, 2023•5 min•Season 3Ep. 19
3.18 Bartonella Henselae Microbiology review for the USMLE Step 1 exam Bartonella henselae is an intracellular gram negative rod that causes several different diseases Bartonella targets and lives inside specialized immune cells called CD34+ cells Bartonella creates a protective vacuole that protects it and helps it evade immune detection Bartonella henselae is a facultative intracellular bacteria Three different clinical syndromes associated with bartonella henselae: cat scratch disease, bacill...
Feb 10, 2023•4 min•Season 3Ep. 18
3.17 Brucella Species Microbiology review for the USMLE Step 1 exam Brucella species are gram-negative intracellular coccobacilli that are spread from animals to humans, causing a zoonotic infection called Brucellosis. B. melitensis is the most common species that causes infection in humans and is also the most virulent. Brucella only requires a very small dose (10-100 bacteria) to cause full-blown disease, often spread through contaminated unpasteurized milk or contact with animal carcasses. "B...
Feb 08, 2023•4 min•Season 3Ep. 17
3.16 Pasteurella Multocida Microbiology review for the USMLE Step 1 exam Pasteurella multocida is a gram-negative coccobacillus that commonly causes infection following animal bites or scratches Classic presentation is a young male with swollen, red, and tender skin at the site of the bite or scratch Symptoms develop rapidly, usually within 3-48 hours after injury In rare cases, infection can progress to necrotizing fasciitis or bacteremia Diagnosis is made clinically using patient history and s...
Feb 06, 2023•2 min•Season 3Ep. 16
3.15 Bordetella Pertussis Microbiology review for the USMLE Step 1 exam Bordetella pertussis is a gram-negative bacterium that causes whooping cough Spread through respiratory droplets, most people are vaccinated against it Adheres to ciliated respiratory epithelial cells and produces toxins that cause inflammation and systemic effects Pertussis toxin and tracheal cytotoxin are important toxins secreted by the bacteria Symptoms include four stages: incubation, catarrhal, paroxysmal, and convales...
Feb 03, 2023•6 min•Season 3Ep. 15
3.14 Haemophilus Influenzae Microbiology review for the USMLE Step 1 exam Haemophilus influenzae is a gram negative coccobacilli that is often encapsulated, encapsulated strains are broken up into subgroups a through f, non-encapsulated strains are referred to as non-typable The most common pathogenic strain is type b, which causes disease in children and immunocompromised individuals, it is the strain that we vaccinate against The group B H. influenzae vaccine is a conjugated polysaccharide vac...
Feb 01, 2023•8 min•Season 3Ep. 14
3.13 Moraxella Catarrhalis Microbiology review for the USMLE Step 1 exam Moraxella Catarrhalis is a gram negative diplococcus that is part of normal upper respiratory tract flora Mainly causes three different types of infections: otitis media in children, lower respiratory tract infections in COPD patients, and pneumonia in elderly patients Otitis media is the most common bacterial infectious disease in childhood and the most common reason for which children receive antibiotics. M. catarrhalis c...
Feb 01, 2023•4 min•Season 3Ep. 13
3.12 Neisseria Species Microbiology review for the USMLE Step 1 exam Neisseria species are gram negative diplococci that infect and live inside neutrophils Two main species that cause infections in humans: Neisseria gonorrhoeae and Neisseria meningitidis Neisseria gonorrhoeae causes the sexually transmitted infection gonorrhea, which is the second most common STI Risk factor for gonorrhea is unprotected sex with an infected person N. gonorrhoeae uses pilli to adhere to epithelial cells and invad...
Jan 30, 2023•9 min•Season 3Ep. 12
3.11 Nocardia and Actinomyces (Branching Filamentous Species) Microbiology review for the USMLE Step 1 exam Nocardia and Actinomyces are two gram positive bacteria that grow in filaments, resembling fungal hyphae. Both are associated with chronic pulmonary lesions, subcutaneous abscesses, and multiple draining sinuses. Both are capable of producing sulfur granules. Actinomyces is anaerobic and colonizes the mouth, GI, and urinary tracts. It can cause "lumpy jaw syndrome" and requires a long cour...
Jan 30, 2023•9 min•Season 3Ep. 11
3.10 Clostridium Species Microbiology review for the USMLE Step 1 exam Clostridium species are spore-forming anaerobic gram-positive rods that secrete toxins Four main species: Clostridium difficile, Clostridium perfringens, Clostridium botulinum, Clostridium tetani Clostridium difficile: common cause of antibiotic-associated diarrhea, caused by overgrowth of C. diff in gut after taking antibiotics that do not kill it, treatment involves stopping offending antibiotic and changing to one that can...
Jan 27, 2023•10 min•Season 3Ep. 10
3.09 Corynebacterium Diptheriae Microbiology review for the USMLE Step 1 Exam Corynebacterium diphtheriae is an aerobic gram positive rod that causes diphtheria, commonly spreads through respiratory droplets C. diphtheriae produces an exotoxin called diphtheria toxin which can cause systemic effects by inactivating elongation factor (EF-2) via ADP-ribosylation and shutting down protein synthesis Diphtheria causes fever, sore throat, croup-like cough, pseudomembranous pharyngitis, severe cervical...
Jan 25, 2023•5 min•Season 3Ep. 9
