PC705 Module 2 Infectious Disease

Streptococcus Pneumoniae - answernormally colonized in the pharynx Cultured from throat swab If found in the lungs, most common form of infection Causes community-acquired pneumonia. Can be tricky to ID. Continue to search - listen to breath sounds, spo2, cxr, living situation Fungal Cell Membranes - answerkey elements: Eukaryotic cells *membrane lipid ergosterol* which is the *target of antifungal drugs* and is not found in human cells. Azoles (fluconazole) and allylamines (terbinafine) block the production of ergosterol. Fungal infections can be superficial (dermatophytes on skin & hair) or systemic (rarer and more lethal) More common in immunocompromised people. HIV - answerretrovirus: -RNA based virus *Reverse transcriptase enzyme converts to single-strand, then double strand DNA* -integrase inserts into host cell genome ID: test for presence of HIV P24 antigen and antibodies to HIV Viral load and CD4 count is tracked. Antiretroviral therapies (ART) target reverse transcriptase (nucleoside RT inhibitors or non-nucleoside RT inhibitors); integrase inhibition; protease inhibition; fusion inhibition; block of coreceptor. Goal of ART Tx: achieve low to undetectable viral copies, at which point it is not possible to transmit the virus to others. Progression if not treated: Tracking of CD4 lymphocytes indicate an acute decline, recovery, followed by a more prolonged decline during clinical latency (9 weeks to 9 years) until death. Viral load has an acute peak that is then suppressed by adaptive immune responses, then gradually increased during latency (9wk-9yr range), followed by a rapid increase with transition to AIDS. At risk populations: older adults have reduced awareness of risk since they aren't worried about pregnancy, Dx may be delayed, more rapid decline and more severe presentation due to an already lower CD4 count with aging. Malaria (Plasmodium Species) - answerthe best way to ID: look under a microscope to see the parasite Plasmodium falciparum! *infection colonizes in the liver, symptoms begin once it spreads to rbcs.* *dx confirmed by microscope for RBC inclusions* Other ID methods: polymerase chain reaction (PCR) for parasite DNA, immune-based rapid detection test, host antibodies. Protozoal parasite of 5 pathogenic Plasmodium species Transmission by the female Anopheles mosquito: organism proliferation is sexual (in mosquito) and asexual (in vertebrate host) Parasites have a high degree of drug resistance. Prophylaxis given to travelers in high-risk areas. Prevention: protective clothing, mosquito nets High-risk groups: children, pregnancy, concurrent HIV infection Norovirus - answermost common cause of viral gastroenteritis in children ID: immune-based detection or NAAT Mycobacterium tuberculosis - answerexample of avoidance factors in bacteria. MTB avoids destruction by a thick, lipid-rich cell wall and its ability to block lysosomal degradation. It's an intracellular pathogen. Exposure is often followed by effective clearance or latency. Progression to disease occurs in vulnerable populations, kids, immunocompromized, homeless shelters. Host responses reduce risk of infection: lung protective mechanisms, mucocillary clearance, cough. Penetration to alveoli facilitates uptake by macrophages - THICK LIPID WALL RESISTS DESTRUCTION - bacilli grow in macrophages, TB infection established, ID via sputum culture. Macrophages present antigen, activate T lymphocytes to accumulate in infection focus. Granuloma (waxy ball) forms and grows. Granuloma breakdown disseminates infection, producing TB disease, increasing risk of spread. Reason for latent infection. TB infection: not symptomatic TB disease: symptomatic, can spread disease. Life cycle: airborne droplet transmission to others, infected macrophages, granuloma contains infection - bacilli replicate - immune cells multiply, granuloma is vulnerable to rupture which would release bacilli systemically. Colonization vs. Infection - answercolonized - carrier, meaning that infectious organism is present on or in the body without necessarily causing illness, no evidence of inflammation, limited bacterial growth, no progression to infection, no s&s. Infection - organism present, documented by culture or another means, infection progresses with pathogen numbers increasing + invading tissues, local inflammation (red, heat, swelling, pain), s&s present, may become systemic (sepsis, bacteremia)