MMSC 428 EXAM 4 QUESTIONS WITH VERIFIED SOLUTIONS LATEST UPDATE 2026

MMSC 428 EXAM 4 QUESTIONS WITH VERIFIED SOLUTIONS LATEST UPDATE 2026 CMI - Answers immune system response that is important for fighting off intracellular parasites (FIPs and OIPs), because once they are inside of the cells antibodies are not helpful mycobacterium characteristics - Answers -have a lot of hydrophobic myconic fatty acids in their cell wall, so they do not gram stain well -gram positive like bacilli -obligate aerobes -slow growers -colonies take 4-6 weeks to appear -produce dry, flat colonies with irregular filamentous edge that may produce orange or yellow carotenoid pigment -catalase + (measured with semiquantitative test) -have innate resistance to disinfectants and antimicrobial therapies due to slow growth and hydrophobic cell wall -show beading (irregular staining) and cording (clumped cells sticking together) in carbol fuschin stain -can be classified according to Runyun classification -MALDI-TOF, high pressure liquid chromatography (HPLC) MIDI, and NAAT are the best way to identify species -antibodies are detect with PPD skin test, active infections can be seen with chest X ray (granulomas) Mycobacterium tuberculosis clinical significance - Answers -most important member of the mycobacterium tuberculosis complex (MTBC) -causes tuberculosis (LRT infection) -bacteria cause a delayed type hypersensitivity response that causes overstimulation of the CMI, which causes the damage that is seen (not the bacteria) -bacteria are innately resistant to a lot of drugs and multi-drug resistant strains are appearing and making it more difficult to treat -most cases are seen in asia, africa and india -not seen a lot in the US, most cases are immigrants -vaccine is available (attenuated M. bovis) semiquantitative catalase test - Answers hydrogen peroxide is added to bacteria located in a test tube, and the height of the bubbles produced tells you approximately how much catalase enzyme is produced by the bacteria -used to differentiate the mycobacteria species mycobacterium tuberculosis - Answers -FIP that mainly infects monocytes and macrophages (latent infection) -most common mycobacterial infection in the world -causes respiratory infections -being a FIP is the most important virulence factor -gram positive-like cell wall that does not gram stain due to high myconic lipid content -produce nonpigmented buff colored (tannish white) colonies in heaping piles -NO3 (nitrate) + -niacin + -heat stable catalase - (is heat labile) -sensitive to isoniazid and rifampin -show a lot of cording (clumping of cells) in microscopy -gene probes on direct samples, HPLC MIDI and MALDI-TOF are best ways to identify the speices mycobacterium bovis - Answers -member of the mycobacterium tuberculosis complex -very similar species to M. tuberculosis -**T2H sensitive** -produces heat labile catalase -bacteria that is used to make the vaccine for tuberculosis -causes a Tb-like disease in humans that is acquired from cows (inhalation or unpasteurized dairy) -causes Tb in cows mycobacterium ulcerans - Answers -found in fresh water and and mud -grows mainly in the tropics and subtropics (humid) -**grows at 30 C not 37 C** because it causes a skin infection and the skin is cooler than the core temp -Buruli ulcer: bacteria in mud or water is introduced into a lesion that begin forms a raised nodule and then transforms to a Buruli ulcer most common mycobacteria (worldwide) - Answers 1. mycobacterium tuberculosis acterium leprae acterium ulcerans mycobacterium kansasii - Answers -**photochromagen** (only member of the MTB complex that is) -Runyon classification group 1 (slow growers, photochromagens) -relatively weak pathogen -common infection in the US -NTM lung disease: similar to Tb, but only seen in immunocompromised individuals mycobacterium avium complex (MAC) - Answers -found in fresh water, soil and plants -is not necessary to identify the species for treating infections, just need to identify to the level of the complex -nonchromogenic -**NAP sensitive** -Runyon classification group 3 (slow grower, nonchromogenic) -important human pathogens, infections have increased dramatically since AIDS epidemic (80's) mycobacterium avium complex (MAC) clinical significance - Answers -M. avium and M.intracellularae are very clinically significant -used to only be seen in older men with history of smoking, since the 80's there has been a significant increase in cases due to rise in AIDS -weak pathogens, only infect immunocompromised individuals -pulmonary disease: Tb-like disease only seen in compromised lungs (HIV, AIDS, history of smoking) -cervical lymphadenitis: inhaled bacteria infect cervical lymph nodes in children (weak immune system) -disseminated infection: AIDS and HIV patients do not have adequate CMI response to stop the bacteria from spreading, so secondary infections are seen around the body -may be associated with Crohn's disease mycobacterium leprae - Answers -second most common mycobacterial infection in the world -VERY slow growing bacteria -cannot be cultured on media, but can be grown in armadillo and mouse animal models -antibodies can be detected with lepromin test (similar to PPD test for Tb) -acid fast positive mycobacteirum leprae clinical significance - Answers -hansen disease (leprosy): lesions on the skin and cartilage, 2 forms with varying severity (tuberculoid or lepromatous) -rare in US, most cases are acquired outside the US -**NOT highly contagious from person to person** -can be spread through nasal secretions -2nd most common mycobacterial infection in the world mycobacterium haemophilum - Answers -slow grower -requires hemin (X factor) from blood -grows better at 30 C than 37 C because it causes skin infections -produces heat labile catalase -mainly isolated from skin lesions mycobacterium marinum - Answers -found in fresh water -photochromagen -grows better at 30 C not 37 C because it causes skin infections -swimming pool granuloma: fresh water or improperly chlorinated pool can harbor bacteria that enter a skin lesion and forms an ulcer mycobacterium xenopi - Answers -found in soil and water -Runyon classification group 2 (slow grower, scotochromagen) -not a common isolate, can be a commensal organism or lab contaminant -clinically significant for immunocompromised individuals mycobacterium gordonae - Answers -not a common isolate in the lab -may be a commensal organism or lab contaminant -usually only infection to immunocompromised individuals mycobacterium abscessus - Answers -grows well at 35-37C -causes information or abscesses on a wound or at an internal site -more infectious to immunocompromised individuals, but is being seen more and more often mycobacterium chelonae - Answers -environmental pathogen -rare clinical isolate -clinically significant when isolated from immunocompromised patient -mainly causes wound infections mycobacterium scrofulaceum - Answers -rare isolate -causes wound infections -mainly seen in immunocompromised individuals mycobacterium laboratory characteristics - Answers -obligate aerobes -acid fast bacilli with gram-positive- like cell wall -do NOT gram stain well due to high content of myconic fatty acids in the cell wall -acid fast + (carbon fuschin can be hot or cold) -auramine-rhodamine flourescent stain and phenol acridine orange fluorescent stain can be used -very slow growers (about 6 weeks for colonies) -grow well on nutritious agars like middlebrook 7H10 and 7H11, and LJ agars -unique hydrophobic cell wall prevents disinfectants from entering the cell -very few genes are active due to slow growth, so there are not many mechanisms for antibiotics to attack Runyon classification - Answers a classification scheme that is used to identify Mycobacterium spp. based on their growth rate (fast or slow growers) and pigment production (photochromogens, scotochromogens, nonchromogens) -**not used anymore due to the high number of species that were exceptions to the classification** -group 1: slow growers, photochromogens -group 2: slow growers, scotochromogens -group 3: slow growers, nonchromogens -group 4: fast growers, scotochromogens or nonchromogens photochromogen - Answers bacteria that produce pigments only when they are incubated in light scotochromogens - Answers bacteria that produce pigments when they are incubated in either the light or dark Mycobacterium kansasii (fill in the blank) - Answers the most commonly isolated photochromogen in the US is ________________________________________ Mycobacterium tuberculosis pathogenesis - Answers Tuberculosis -primary infection: bacteria are inhaled and taken up by macrophages in the lungs, initial flu-like symptoms occur with dry cough and memory immune cells form (5% mount immune response and clear bacteria completely -latent infection: symptoms go away, and bacteria form latent infection in granulomas in the lungs (active pockets of bacteria, pus and immune cells in the lungs that are blocked off from the rest of the body) -reactivation: reactivation of bacteria occurs when a granuloma bursts open or from bacteria in the environment, over stimulating the CMI memory cells and causing very severe illness with bloody productive cough, inflammation and "consumption" -disseminated infection: (military Tb) bacteria in the blood stream during the reactivation infect secondary body sites and lead to serious and life-threatening infection mycobacterium leprae pathogenesis - Answers Hansen disease (leprosy) -bacteria is spread through close contact with nasal secretions, and after many years of incubation skin and cartilage lesions begin forming -2 clinical manifestations, not that contagious from person to person -Tuberculoid (TL): mild skin lesions form, swelling and granulomas appear, effective CMI response is mounted and bacteria are cleared with a few months of antibiotics -Lepromatous (LL): constant bacteremia causes severe progressive skin lesions that affect mucous membranes, causes swelling in bones, joints (claw hands), and face (lion face) due to strong antibody response that increases inflammation and weak CMI response, usually will be on antibiotics for the rest of their life to keep bacteria at a controllable level tuberculosis prevention - Answers -PPD skin test: tuberculin proteins are made into standard concentration, 1/10 mL is injected subcutaneouslyand enters regional lymph nodes, within 48-72 hours if there are any memory cells from a previous tuberculosis infection there will be a strong CMI response that causes a raised lesion of 10 mm or more (reactive skin test) -chest X ray: if someone has a reactive skin test you follow up with chest X ray to see if the infection is latent (granulomas seen) or past (calcified Ghon complexes) -isoniazid, rifampin, ethambutol and pyrazinamide are administered as a multi-drug cocktail for 6-9 months to treat infection -BCG vaccine (attenuated M. bovis) is made by growing M. bovis until it is not virulent and injecting suspension into children (60% effective) BCG vaccine - Answers vaccine for tuberculosis made using attenuated M. bovis -only 60% effective in children -not effective in adults Ghon complex - Answers calcified lesions in the lungs that indicate a previous infection with Tuberculosis -granulomas were so old that they become anaerobic and killed the bacteria (obligate aerobes) and the area calcified positive PPD test - Answers tells you that the person has memory cells from a previous exposure to tuberculosis -does not tell you if the person is currently infected or not -should be followed up with chest X ray to evaluate mycobacterium ulcerans (fill in the blank) - Answers the causative agent of Buruli ulcer is __________________ tuberculoid (TL) hansen disease immue response - Answers -strong effective CMI response is mounted and able to manage the bacteria and decrease sympomts -very few antibodies produced (not that helpful for FIPs)