Infectious Flashcards
candidemia
disseminated form of Candida infection. Candida exists as a single-celled budding yeast with pseudohyphae (C albicans also exhibits “germ tubes,” hyphal structures formed when the organism is grown in a specific nutritionally rich serum).
- Candida is a component of normal human skin and mucous membrane flora and is an opportunistic pathogen (does not cause disseminated infection in healthy people)
- Host defense is provided by 2 immune system components with distinct functions:
1. T lymphocytes (in particular TH cells) are important for prevention of superficial Candida infection (eg, oral/esophageal candidiasis, cutaneous candidiasis, Candida vulvovaginitis).
Conditions such as HIV (low T-cell count) increase the risk of superficial candidiasis.
2. Neutrophils prevent the hematogenous spread of Candida. Disseminated candidiasis (eg, candidemia, endocarditis) is more likely in patients who are neutropenic or otherwise immunocompromised (eg, cancer with chemotherapy) and in those with inherited impairments of phagocytosis.
Neisseria gonorrhea and N meningitidis.
Low levels of C5, C6, C7, C8, and C9 predispose individuals
Candida albicans infection
- white plaques on this patient’s oral mucosa are characteristic of oral thrush
- Oral thrush most commonly presents with white patches on the oral mucosa (pseudomembranous candidiasis) that can be easily scraped off, revealing an erythematous mucosal surface underneath
- Microscopic examination of KOH-treated scrapings shows Candida yeast and pseudohyphae.
- Oral thrush occurs in denture wearers, diabetics, immunosuppressed patients, and patients receiving steroids, antibiotics, or chemotherapy
- Other superficial diseases associated with Candida include cutaneous candidiasis (“diaper rash” in infants) and Candida vulvovaginitis.
- Cutaneous candidiasis occurs in areas exposed to heat and high humidity (such as the groin and perianal area in infants).
- Vulvovaginal candidiasis is associated with antibiotic and contraceptive use, pregnancy, diabetes mellitus, and HIV.
Microsporum
Caused by animal contact
- This fungus affects the superficial keratinized skin layer, causing dermatophytosis.
Histoplasma capsulatum
- endemic to the Mississippi and Ohio River basins
- present in bird and bat droppings.
- history of cleaning bird coops or exploring caves.
rabies
- patient’s progressive agitation, disorientation, and pharyngospasm
- fatal infection caused by a neurotrophic virus from the Rhabdoviridae family
- Exposure usually occurs when patients come into contact with contaminated saliva from an infected animal (eg, dog, bat), which likely occurred during this patient’s camping trip in New Mexico.
- contains a bullet-shaped envelope with knob-like glycoproteins that allow it to attach to the nicotinic acetylcholine receptor at the neuromuscular junction
- virus replicates locally within the muscle tissue of the bite wound for several days or weeks and then travels in a retrograde fashion through peripheral nerve axons to the dorsal root ganglia.
- From there, it rapidly ascends the spinal cord and infects the diencephalon, hippocampus, and brain stem
- Patients initially develop a nonspecific flu-like prodrome (fever, malaise, myalgias); paresthesias radiating proximally from a known wound site can be an important clue.
- When the virus enters the CNS, the infection typically evolves into rabies encephalitis, which is characterized by painful pharyngeal spasms leading to avoidance of water (hydrophobia), mental status changes, muscular rigidity, and autonomic dysfunction (pupil dilation, hypersalivation).
- Once symptoms of rabies encephalitis appear, postexposure prophylaxis is no longer effective and nearly all patients die.
Epstein-Barr virus
- binds to CD21 on inactive B-lymphocytes and results in infectious mononucleosis,
- usually characterized by sore throat, swollen lymph nodes, malaise, and atypical lymphocytosis.
- this virus is a member of the Herpesviridae family, initial infection is followed by a long-standing (usually asymptomatic) latent infection.
Rhinovirus
- binds intracellular adhesion molecule-1, which is found on nasopharyngeal and adenoid epithelial cells.
- associated with the common cold,
influenza virus
- has hemagglutinin glycoproteins that allow it to attach to sialic acids on the surface of the respiratory epithelium.
- characterized by fever, myalgias, cough, headache, and respiratory symptoms;
Cytomegalovirus
- binds to vascular endothelial integrins, leading to replication within endothelial cells
- Initial infections are often asymptomatic, but patients can develop a mononucleosis-type syndrome (eg, lethargy, fever, atypical lymphocytosis).
HIV
- present with a macular or maculopapular rash associated with fever.
- rash is usually well circumscribed and involves the trunk, face, and palms and soles.
Varicella
- presents with fever and a vesicular eruption that can affect multiple areas, including the face, trunk, abdomen, and extremities.
herpes simplex infection
- Disseminated herpes simplex infection is seen primarily in immunocompromised patients and presents with diffuse vesicles on an erythematous base.
disseminated gonococcal infection (DGI).
- purulent arthritis of the knee, oligoarticular joint pain, and a few vesiculopustular lesions on the extremities
- one of the most common causes of septic arthritis in young, sexually active individuals.
- due to the spread of Neisseria gonorrhoeae from a (usually asymptomatic) genitourinary infection into the systemic circulation.
- present with either purulent arthritis or triad of polyarthralgia, dermatitis and tenosynovitis
- diagnosis is made when blood, urine or joint fluid microscopy and culture reveal gram neg intracellular diplococci
Salmonella
- gram neg
oxidase negative chrved rod - Px with sickle cell dse are at increased risk of septic arthritis d/t salmonella
