What component of Mycoplasma cell membrane is unique?Answer: It contains sterols like cholesterol and is the cell's only protective layer. Mycoplasma...
Why do penicillins and cephalosporins not work against Mycoplasma?
Why do penicillins and cephalosporins not work against Mycoplasma?Answer: Mycoplasma has no cell wall, therefore, penicillins and cephalosporins...
How is nocardiosis treated?
How is nocardiosis treated?Answer: Trimethoprim-sulfamethoxazole (TMP-S...
What risk factors predispose to Nocardia infection?
What risk factors predispose to Nocardia infection?Answer: Immunosuppression and can...
How does a Nocardia infection manifest?
How does a Nocardia infection manifest?Answer: Infection with Nocardia can produce pneumonia, lung abscesses, and can spread systemically. Abscesses...
How is Nocardia transmitted?
How is Nocardia transmitted?Answer: Transmitted via inhalation, producing lung abscesses and cavitations (it can be confused with Mycobacterium ...
Does Nocardia require oxygen?
Does Nocardia require oxygen?Answer: Yes. Nocardia is aerobic, in contrast to Actinomyces, an anaero...
Where is Nocardia normally found?
Where is Nocardia normally found?Answer: In the soil with transmission via inhalation. Nocardia is never a normal flo...
Describe the appearance of Nocardia asteroides on light microscopy:
Describe the appearance of Nocardia asteroides on light microscopy:Answer: Gram-positive rods forming branching, beaded filament S. Nocardia is also...
How are Actinomyces infections treated?
How are Actinomyces infections treated?Answer: Penicillin G (often for a prolonged course) +/- surgical drain...
How does an Actinomyces infection manifest?
How does an Actinomyces infection manifest?Answer: Actinomyces causes eroding abscesses with draining sinus tracts. Main forms are cervicofacial...
Can Actinomyces grow without oxygen?
Can Actinomyces grow without oxygen?Answer: Yes. Actinomyces is an anaero...
What are sulfur granules of Actinomyces?
What are sulfur granules of Actinomyces?Answer: Yellow-colored colonies and cellular debris (do not actually contain sulfur) that are visible within...
Where is Actinomyces normally found?
Where is Actinomyces normally found?Answer: In the gingival crevices of the teeth, especially in patients with poor oral hygiene. It forms part of...
Describe the appearance of Actinomyces israelii on light microscopy:
Describe the appearance of Actinomyces israelii on light microscopy:Answer: Gram-positive rods forming branching, beaded filaments. Colonies in pus...
A 30-year-old woman from Southeast Asia presents with a hypopigmented, macular forearm lesion and associated with loss of sensation (decreased pin prick). The arm shows significant muscle atrophy. What is the most likely diagnosis?
A 30-year-old woman from Southeast Asia presents with a hypopigmented, macular forearm lesion and associated with loss of sensation (decreased pin prick)....
A 34-year-old male immigrant presents to the physician with a cough and fever. On his last visit 12 months ago, his PPD was positive and chest x-ray showed likely active tuberculosis. He was treated with INH and rifampin and his symptoms abated. On this visit, he appears very sick and has hard time breathing. He denies night sweats and hemoptysis. His temperature is 102.1°F. Chest x-ray reveals infiltrates in the right middle and lower lobes and a Ghon complex. He is still taking INH and rifampin, which do not seem to help. What is the most likely diagnosis?
A 34-year-old male immigrant presents to the physician with a cough and fever. On his last visit 12 months ago, his PPD was positive and chest x-ray showed...
A patient presents with low-grade fever, chills, night sweats, weight loss, and a cough productive of blood-tinged sputum for 2 months. You suspect tuberculosis (TB) and order a chest x-ray. What findings on chest x-ray would be consistent with your suspected diagnosis?
A patient presents with low-grade fever, chills, night sweats, weight loss, and a cough productive of blood-tinged sputum for 2 months. You suspect tuberculosis...
A 22-year-old woman is taking isoniazid prophylaxis for tuberculosis exposure. After 1 month of therapy she develops tingling in both her hands. What is the term for what she is experiencing and how would you treat her?
A 22-year-old woman is taking isoniazid prophylaxis for tuberculosis exposure. After 1 month of therapy she develops tingling in both her hands. What...
What causes fish-tank or swimming-pool granuloma?
What causes fish-tank or swimming-pool granuloma?Answer: Mycobacterium marinum.Granulomatous, ulcerating lesions at the site of breaks in the skin...
What is Mycobacterium avium complex (MAC) and what are its symptoms?
What is Mycobacterium avium complex (MAC) and what are its symptoms?Answer: A mycobacterium ubiquitous in water and soil, but has become a common...
How are close contacts prophylactically treated?
How are close contacts prophylactically treated?Answer: Daps...
What are potential toxicities associated with dapsone treatment?
What are potential toxicities associated with dapsone treatment?Answer: Methemoglobinemia and hemoly...
What is the treatment of leprosy?
What is the treatment of leprosy?Answer: Dapsone and rifampin for tuberculoid form. Add clofazimine for lepromatous form. Because of slow growth...
What is the main host defense against leprosy?
What is the main host defense against leprosy?Answer: Cell-mediated immunity (CD4+ T cells and macrophages) because M. leprae is a facultative intracellular...
How is M. leprae cultured or grown?
How is M. leprae cultured or grown?Answer: Mycobacterium leprae cannot be cultured on artificial media, and has been grown on mouse footpads and...
What conditions favor the growth of M. leprae?
What conditions favor the growth of M. leprae?Answer: Low temperature (30°C). Mycobacterium leprae preferentially affects cool areas of the body...
How is leprosy transmitted?
How is leprosy transmitted?Answer: Respiratory secretions or contact with skin lesions of infected individual. However, not all individuals are susceptible...
What laboratory test distinguishes between lepromatous and tuberculoid leprosies?
What laboratory test distinguishes between lepromatous and tuberculoid leprosies?Answer: Lepromin skin test is Negative in lepromatous leprosy. Positive...
What is tuberculoid leprosy?
What is tuberculoid leprosy?Benign form of leprosy that is mild and sometimes self-limiting disease in a person with intact cell-mediated immunity. Usually...
What is lepromatous leprosy?
What is lepromatous leprosy?Malignant, progressive form of leprosy that results from failure of cell-mediated immunity and primarily affects the nerves,...
What are the two main clinical manifestations of leprosy?
What are the two main clinical manifestations of leprosy?1. Lepromatous leprosy2. Tuberculoid lepr...
What is the most common cause of adrenal insufficiency worldwide?
What is the most common cause of adrenal insufficiency worldwide?Answer: Adrenal...
What is the most common extrapulmonary manifestation of tuberculosis?
What is the most common extrapulmonary manifestation of tuberculosis?Answer: Scrofula or cervical mycobacterial lymphadeni...
What is Pott disease?
What is Pott disease?Answer: Tuberculous infection of the thoracic/lumbar spine leading to destruction of intervertebral discs/bodies and compression...
Who gets miliary tuberculosis?
Who gets miliary tuberculosis?Answer: Those with weakened cell-mediated immunity (HIV positive, elderly, childr...
What is miliary tuberculosis?
What is miliary tuberculosis?Answer: Disseminated TB infection leading to millet seed-sized granulomas in the lungs, liver, spleen, bone, kidneys,...
What percentage of primary infections progress to active tuberculosis?
What percentage of primary infections progress to active tuberculosis?Answer: Five percent of those primarily infected will develop reactivation...
What are the main toxicities of anti-tuberculous therapy?
What are the main toxicities of anti-tuberculous therapy?Answer: Rifampin → orange discoloration of urine/tears, hepatitis, drug interactionsIsoniazid...
What is the treatment of active tuberculosis?
What is the treatment of active tuberculosis?Answer: Cough with hemoptysis, low-grade six-month regimen: initially four drugs (rifampin, isoniazid,...
What are the signs and symptoms of active pulmonary tuberculosis?
What are the signs and symptoms of active pulmonary tuberculosis?Answer: Cough with hemoptysis, low-grade fever, night sweats, and weight loss. Chest...
What is secondary tuberculosis?
What is secondary tuberculosis?Answer: Reactivation of a prior infection due to weakened immunity (months to years later). Most adult cases of active...
Pathology Correlate: The Ghon complex is the hallmark of primary tuberculosis, what is it?
Pathology Correlate: The Ghon complex is the hallmark of primary tuberculosis, what is it?Answer: Ghon complex = a Ghon focus (calcified TB granuloma...
What is the pathology of symptomatic primary tuberculosis?
What is the pathology of symptomatic primary tuberculosis?Answer: In the lungs and other organs, large caseous granulomas develop and eventually...
What groups are at risk for symptomatic primary tuberculosis?
What groups are at risk for symptomatic primary tuberculosis?Answer: Those with deficient cell-mediated immunity (children, elderly, immunocom-promised...
What are the clinical manifestations of most primary infections with tuberculosis?
What are the clinical manifestations of most primary infections with tuberculosis?Answer: No symptoms (asymptomatic 90%), positive PPD, Ghon com...
Pathology Correlate: Describe the pathogenesis of primary tuberculosis:
Pathology Correlate: Describe the pathogenesis of primary tuberculosis:Answer: Mycobacteria ingested by phagocytes trigger cell-mediated immunity...
What is primary tuberculosis?
What is primary tuberculosis?Answer: An infection in the lungs of a previously unexposed individ...
How is tuberculosis transmitted?
How is tuberculosis transmitted?Answer: Inhalation of infected respiratory dropl...
How is M. tuberculosis cultured?
How is M. tuberculosis cultured?Answer: Lowenstein-Jensen agar. However, it is important to remember that TB is very difficult to culture and takes...
What can cause a false-positive PPD?
What can cause a false-positive PPD?Answer: Bacillus Calmette-Guérin (BCG) vaccine, prior treated tuberculosis (once exposed, the PPD remains positive...
What medication must be coadministered to all patients on isoniazid therapy and why?
What medication must be coadministered to all patients on isoniazid therapy and why?Answer: Vitamin B6 (pyridoxine) to prevent a peripheral neur...
How is latent tuberculosis (TB) infection detected and how is it treated?
How is latent tuberculosis (TB) infection detected and how is it treated?Answer: Latent infection is conversion to positive PPD with no signs or...
What are the criteria for a positive PPD skin test?
What are the criteria for a positive PPD skin test?Answer: A positive test is defined based on the size of the red, raised in duration after 48 hours:...
Purified protein derivative (PPD) is a skin test for tuberculosis. How does it work?
Purified protein derivative (PPD) is a skin test for tuberculosis. How does it work?Answer: Intradermally injected proteins from M. tuberculosis...
What is the main host defense against M. tuberculosis?
What is the main host defense against M. tuberculosis?Answer: Cell-mediated immunity (CD4+ T cells and macrophag...
What populations are most at risk for TB?
What populations are most at risk for TB?Answer: Elderly persons, immunocompromised, human immunodeficiency virus (HIV)/immunosuppressed (transplant...
What two classic "ancient" diseases are caused by mycobacteria?
What two classic "ancient" diseases are caused by mycobacteria?Answer: Tuberculosis ("consumption") by Mycobacterium tuberculosis and leprosy (Hansen...
What other bacteria are acid-fast? Why?
What other bacteria are acid-fast? Why?Answer: Nocardia species are acid-fast because their cell walls are also high in mycolic ac...
What is the principal dye in acid-fast stain and what component of the cell wall does it bind?
What is the principal dye in acid-fast stain and what component of the cell wall does it bind?Answer: Carbolfuchsin binds to mycolic acid (long-chain...
How are mycobacteria visualized under light microscope?
How are mycobacteria visualized under light microscope?Answer: Appear red with Ziehl-Neelsen acid-fast stain. Stain is positive for AFB = "acid-fast...
What are some characteristics of mycobacteria?
What are some characteristics of mycobacteria?Answer: Obligate aerobes, acid-fast bacilli, intracellular growth, and multiple-drug resista...
A 30-year-old human immunodeficiency virus (HlV)-positive man presents with 1 week of fever and malaise. On his forearm there is a 2-cm round, vascular, nontender, friable exophytic lesion. What is the diagnosis? Pathogen? Appropriate treatment?
A 30-year-old human immunodeficiency virus (HlV)-positive man presents with 1 week of fever and malaise. On his forearm there is a 2-cm round, vascular,...
A 5-year-old girl presents to the emergency department (ED) with a deep puncture wound on her hand from a cat bite. There is considerable pain, erythema, and swelling noted. What is required for prophylaxis?
A 5-year-old girl presents to the emergency department (ED) with a deep puncture wound on her hand from a cat bite. There is considerable pain, erythema,...
A 25-year-old woman presents with a painful rash on her hand and tender axillary adenopathy for 2 days. She owns two cats. On examination, she has multiple pruritic erythematous vesicles and papules on her right hand with suppurative axillary adenopathy. What is the diagnosis? Treatment?
A 25-year-old woman presents with a painful rash on her hand and tender axillary adenopathy for 2 days. She owns two cats. On examination, she has multiple...
A patient of yours kills a deer infected with F. tularensis; he then skins it. His wife then prepares the deer for dinner but undercooks it. The deer is served at her office for lunch the next day. What type of infection will the husband present with? What type will his wife and her coworkers present with?
A patient of yours kills a deer infected with F. tularensis; he then skins it. His wife then prepares the deer for dinner but undercooks it. The deer...
What is trench fever?
What is trench fever?Answer: Disease that affected up to 1 million soldiers during World War I. Typically presents with flu-like illness with bone...
What diseases does Bartonella quintana cause?
What diseases does Bartonella quintana cause?Answer: Trench fever, bacillary angiomatosis (several species of Bartonella are known to cause bacillary...
What is the treatment of bacillary angiomatosis?
What is the treatment of bacillary angiomatosis?Answer: Oral erythromycin or doxycycline. Newer macrolides such as azithromycin and clarithromycin...
What is bacillary angiomatosis? What patient population is affected?
What is bacillary angiomatosis? What patient population is affected?Answer: Systemic disease that often presents with cutaneous vascular lesions...
What is the treatment of cat scratch disease?
What is the treatment of cat scratch disease?Answer: Azithromycin, quinolones, or doxycycl...
What is seen on a lymph node biopsy of cat scratch disease?
What is seen on a lymph node biopsy of cat scratch disease?Answer: Stellate granulo...
What is cat scratch disease? What patient population is most often affected?
What is cat scratch disease? What patient population is most often affected?Answer: Cutaneous lesion at the site of cat scratch/bite with regional...
What diseases does Bartonella henselae cause?
What diseases does Bartonella henselae cause?Answer: Cat scratch disease and bacillary angiomato...
What drugs are used as treatment and prophylaxis for P. multocida?
What drugs are used as treatment and prophylaxis for P. multocida?Answer: Treat with penicillin G and prophylaxis with amoxicillin/clavulanate. Pasteurella...
Why shouldn't wounds from animal bites be sutured up?
Why shouldn't wounds from animal bites be sutured up?Answer: Pasteurella multocida is a facultative anaerobe and suturing the wound would provide...
How does P. multocida most commonly present?
How does P. multocida most commonly present?Answer: Painful wound infection with rapid swelling within 24 hours of b...
What is the typical source of Pasteurella multocida in human infections?
What is the typical source of Pasteurella multocida in human infections?Answer: Cat or dog bites (their normal oral flora) or cat scra...
What is the treatment of choice for Brucella?
What is the treatment of choice for Brucella?Answer: Doxycycline plus rifampin or doxycycline plus streptomy...
Who is most likely to acquire brucellosis?
Who is most likely to acquire brucellosis?Answer: Those with close contact with livestock (farmers, veterinarians, meat packers) and those who drink...
What is the most characteristic symptom of brucellosis?
What is the most characteristic symptom of brucellosis?Answer: Undulant (a diurnal rising and falling) fever actually occurs in a minority of patients....
What type of cells does Brucella infect?
What type of cells does Brucella infect?Answer: Reticuloendothelial system (lymph nodes, spleen, liver, and bone marr...
What is the drug of choice for the treatment of F. tularensis?
What is the drug of choice for the treatment of F. tularensis?Answer: Streptomy...
How is F. tularensis diagnosed?
How is F. tularensis diagnosed?Answer: Serological tests since laboratory culture is danger...
What is required for host defense against F. tularensis?
What is required for host defense against F. tularensis?Answer: Cell-mediated immunity as F. tularensis is an intracellular patho...
Francisella tularensis has what special culture requirement?
Francisella tularensis has what special culture requirement?Answer: Most strains require cystei...
How virulent is F. tularensis?
How virulent is F. tularensis?Answer: Highly virulent. Requires only 10 to 50 organisms to cause disease. Most diagnostic laboratories will not culture...
How is F. tularensis spread?
How is F. tularensis spread?Answer: Via vectors (wood ticks, deerflies, mosquitoes) and handling of infected animals (especially rabbits and deer)....
Francisella tularensis causes two forms of tularemia, describe both forms:
Francisella tularensis causes two forms of tularemia, describe both forms:1. Ulceroglandular form (70%-80%; handling of infected animals) presents with...
How is Y. enterocolitica treated?
How is Y. enterocolitica treated?Answer: Treat with either fluoroquinolones or trimethoprim-sulfamethoxazole (TMP-SMX). It is resistant to cepha...
Yersinia enterocolitica infection is often confused with what condition?
Yersinia enterocolitica infection is often confused with what condition?Answer: Appendiciti S. Yersinia enterocolitica causes mesenteric adenitis...
How is Yersinia enterocolitica transmitted to humans and what does it cause?
How is Yersinia enterocolitica transmitted to humans and what does it cause?Answer: Consumption of contaminated meat, animal feces, and unpasteurized...
What type of vaccine against Y. pestis is available? What is its limitation?
What type of vaccine against Y. pestis is available? What is its limitation?Answer: A killed whole-cell vaccine protects against bubonic plague and...
How is Y. pestis infection treated?
How is Y. pestis infection treated?Answer: Streptomycin, gentamicin, or doxycycl...
Why is the bubonic plague referred to as the Black Death?
Why is the bubonic plague referred to as the Black Death?Answer: Cutaneous hemorrhage and disseminated intravascular coagulation cause a black skin...
What is the progression of disease in a person infected with Y. pest
What is the progression of disease in a person infected with Y. pestAnswer: Initially lymph nodes will swell and become erythematous, warm, and painful...
What is the purpose of the F1 envelope antigen?
What is the purpose of the F1 envelope antigen?Answer: Inhibits phagocytosis and allows Y. pestis to survive intracellularly in the lymph nodes causing...
Name the important virulence factors for Y. pestis:
Name the important virulence factors for Y. pestis:Answer: F1 envelope antigen, V antigen, W antigen, endoto...
How virulent is Y. pestis?
How virulent is Y. pestis?Answer: Extremely. One to ten organisms can cause disea...
What are the important animal reservoirs for Y. pestis?
What are the important animal reservoirs for Y. pestis?Answer: Rats (worldwide) and prairie dogs (United Stat...
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