MIC 401 EXAM 3 QUESTIONS WITH VERIFIED SOLUTIONS LATEST UPDATE 2026

MIC 401 EXAM 3 QUESTIONS WITH VERIFIED SOLUTIONS LATEST UPDATE 2026 Clostridium - Answers C. botulinum, C. difficile, C. perfringens, C. tetani Gram Postive Bacilli -sometimes stain weakly Spore Formers- hard to treat Most are obligate anaerobes Most are motile Catalase negative (no bubbles) found pretty much anywhere Very good at producing powerful toxins C. perfringens - Answers very fast generation time "tissue gas"- if person dies and not preserved- body will start to fill with gas as a result of its over growth Enzymes can produce gas Nagler plate Histotoxic clostridia Enterotoxigenic clostridia It doesn't grow out of control-its the toxins that it produces that are the problem alpha toxin - Answers degrades phospholipids- particularly in RBC, WBC, Endothelia, and muscle cells C. perfringens Toxins - Answers Primary toxin- alpha toxin beta, epsilon and lota toxins along with other minor toxin not all strains express all toxins Histotoxic clostridia - Answers C. Perfingens type A Gas Gangrene Alpha toxin Special environment- trauma or necrotic tissue, vascular damage, decreased oxygen Symptoms- Local edema, gas production, fever and pain, Necrotic black color, sweet smell, no pus Gas Gangrene- Risk factors, Complications, Treatment - Answers Risk factors- traumatic injuries, surgery around intestinal microbiota, the elderly Immunological complications- Stop immune cells by causing platelet buildup and blockage Escape and grow in cytoplasm Uniquely able to escape a phagocyte before the lysosome fuses with it and the immune system cant find in because its inside one of our cells and eventually escapes the cell It also kills neutrophils- creates a soapy film instead of puss because of the dead neutrophils Treatment- debry of dead tissue, antiserum-polyvalent antitoxin, broad spec AB, Hyperbaric oxygen chamber(helps kill them because they are anearobic) Enterotoxigenic Clostridia C. Perfringens (Food poisoning) - Answers Type A - ingested, breaks down small intestinal mucosa and get leakage Treatment- get AB to toxins One of many ways of getting food poisoning- one of the top 3 C. difficile - Answers "drumstick" shape-subterminal spores Toxin types- Enterotoxin A, Cytotoxin B Transmission- Fecal-oral route Human Pathogen- AB-associated diarrhea, Colitis Enterotoxigenic Clostridia (C. difficile Colitis) - Answers Risk group- patients receiving AB therapy Infection mode- Colonization of Intestines, toxin production, Leukocyte infiltration, formation of Pseudomembrane Treatment- Stop/change AB theapy, Maintain Fluid and Electrolyte balance, fecal transplant C. Tetani - Answers mainly found as spores in soil and GI tract of animals Tetanus Toxin (tetanus-"lock-jaw") Transmission- break in skin, not spread person to person Tetanus toxin - Answers Neurotoxin-blocks release of neruro-inhibitor glycine causes antagonistic muscles to contract at the same time One of the more potent toxins known, only need small amount to cause effects Tetanus - Answers initial involvement of neck and jaw muscles with progression to others in neonatal, initial infection of umbilical stump Initial symptoms- crampin and twitching around wound Later- seating and pain, Risus Sardonicus "sarcastic grin"- cant make another face Extreme symptoms- violent spasms of trunk and back, paralysis of resp. muscles Treatment- AB, muscle relaxants, tetanus immunoglobin, mechanical vent or trach, debribement of necrotic tissue Vaccine- exposure to naturally aquired tetanus doesn't result in immunity C. botulinum - Answers Soil of sediment often as a spore- able to tolerate low oxygen conc ACH causes contraction of muscles- when inhibited-paralysis very deadly organsims Flaccid paralysis- opposite of tentanus SNAR protiens cause ach to be relased- botulism destroys these proteins and ach cant be relased anymore- muscles can no longer contract Botulism - Answers Food-borne and wound symptoms- GI disturbance (18-36 hours), neuromuscular- starts in muscles of the head and descending paralysis Wound symptom- droopy eye lids are a telling sign infant- most common, less than 1 year old, ingestion of spore, why dont give honey to newborns, vaccination of pregnant females Treatment for all- AB Medical use of botulinum toxin - Answers Muscle spasticity, Migraines, Cosmetic Clostridia postive note - Answers major area of research for biofuel production- if given a certain type of feed they produce ethanol and acetone to help make fuel Listeria monocytogenes - Answers gram positive rod most frequent in immunocompromised patients major problem in pregnant women-causes death in babies and the women-not all infections will cross the placenta but high rates in this disease Patients with lymphoma, on steroids, or receiving TNF blocking agents Has a desire for the Nervous System- causes meningitis tumbling motility Require thorough pasteurization, can multiply at 4C and survive frozen Passed from animals to people- associated with milk and milk products, particularly soft cheeses Listeria moncytogenes Pathogensis - Answers replicated intracellularly Attaches to insteinal epithelial call and macrophages once in the phagolysome secretes hemolysis which allow for escape from phagosome and replication in the cytoplasm Listeria monocytogenes treatment - Answers Ampicillin Trimethoprim-Sulfamethoxazole Corynebacterium diphtheriae - Answers Gram postive bacillus Tellurite agar improve ID and recovery B-phage encoding gene for toxin production Human are only reservoir spread by droplet or airborne spreed highly effective vaccine but needs to be kept up with Diptheria pathogenesis - Answers Non-invasive Exotoxin- two seg B (binds to specific receptors) and A(active segment) Toxin works by ADP-ribosylation (EF2)which results in cessation of protein synthesis Targets Heart, Nerves, and Kidneys Very potent Diptheria clinical manifestations - Answers pharyngeal infection but the toxin spread is what causes the problem Extending down the respiratory tract and lead to suffocation from aspiration Bull Neck- massively increases lymph nodes Diptheria immunity, prevention, and treatment - Answers no natural immunity Taxoid vaccine Need vaccine even after exposure because of no natural immunity Pancillin and erythromycin treatment may need antitoxin Bacillus anthracis - Answers gram positive bacilli non-hemolytic growth sporulates in Oxygen oval spores PGA capsule-important in the inhibition of phagocytosis of the vegetative bacilli Catalase positive and non-motile PGA encodes on the pX01 - Answers Protective antigen, edema factor, lethal factor Protective Toxin - Answers combines with Edema factor to make edema toxin EF- increases cyclic AMP and interfers with cell function combines with Lethal factor to create leathal toxin- kills cells Cutaneous Anthrax - Answers Development of classic black eschar local inoculation of spores no purulence and painless development of significant local disease inhalational anthrax - Answers pleural fluid and widened mediastiunum-enlarging and hemorrhagic medistinal nodes Woolsorter's disase rapid disease progression rapid progressio to death Gastrointestinal Anthrax - Answers ingestion of contaminated food unusual in humans CNS anthrax - Answers meningitis rapid progression first US case in the bioterrorism cases Anthrax treatment - Answers Ciprofloxacin, penicillin, tetracycline, Quniolone Human GT tract - Answers contains a variety of commensal bacteria 60-100X more bacterial cells than eukaryotic cells in our body 500 to 1,00 species of bacteria Salmonella spp. - Answers Gram negative, motile bacillus Facultative anerobe Non-lactose fermenter Oxidase-negative Sulfur-reduction-alternative energy production Serovar - Answers a group of closely related microorganisms distinguished by a characteristic set of molecules that evoke an antibody response 5 of these under salmonella Salmonella-Shigella Agar - Answers selective growth medium for gram neg bacteria- contains bile salts that inhibit Gram pos Sugar utilization-neutral red sulfur reduction- sodium thiosulfate Flagellar proteins are - Answers antigenically diverse Classify Salmonella (strains) by - Answers Flagella (119 types) LPS-O side chain differences (Serotypes) (2400 types) Serovar enteritidis - Answers Salmonella Oral enty of infection usually linked to the intestine Invasive bacterium- enters into cytoplasm of the gut "ruffling"- plasma membrane prior to unvasion by salmonella- stimulates its own uptake into gut cells INDUCES REARRANGMENT OF THE ACTIN CYTOSKELETON OF HOST CELL Fever, nausea, cramps, diarrhea Self-limiting disease- rarely is fatal Serovar typhi - Answers Typhoid Fever obligate human pathogen DISSEMINATION FROM INSTINE VIA MARCOPHAGES to lumphatics, blood, liver, kidneys, gall bladder- SYSTEMIC BACTEREMIA Reinvades the intseinal epithelium-hemorrhagic ulceration Could be acute or chonic Infection and Entry of Salmonella enteriditis - Answers gut epithelium Peyer's patches- M cells- used for uptake of proteins and other particles and immune surveillance- salmonella exploits M cells M cells are primary route of invasion Virulence proteins expressed by Salmonella - Answers Clustered in the chromosome (Pathogenicity island I-SPI-1) Mutations-if you knock out any of these genes it diminishes pathogensis Genes in Pathogensis Island 1 encode - Answers Type III secretion system- injects "SIP/SSP" effectors (proteins) into the cytoplasm of the infected cell- to manipulate cell function Stimulates uptake of bacterium into the host cell Once Salmonella is inside the cell theres another Pathogenesis Island- SPI-2 - Answers Same type 3 secretion system- responsible for survival of salmonella in the cytoplasm SSE (effector) Shigella spp. - Answers 4 species all causing bacterial dysentery obligate human pathogen- highly infectious-only 5-50 bactria needed to cause infection Non-motile- no flagellae Facultatice anerobe Non-lactose fermenter-utlizes other sugars Oxidase-NEG characterized by serotypes- only ~ 45 O antigen serotypes Hektoen Enteric Agar - Answers Bile salts inhibit Gram po bacteria bromthymol blue for sugar fermentors Shigella produces raised, green, moist colonies Shigella Dysentery - Answers Ab cramps, fever, diarrhea Infection of submucosal cells of intestines * dose NOT commonly disseminate beyond the gut inflamation, loss of epithelial cells Ulcerative lesions form on the lining of the gut Stool contain copious amounts of mucus and blood- UNLIKE salmonella infections Shigella virulence plasmid - Answers encode genes for invasion again encodes for type 3 secreation system IpaB - Answers (Shigella) protient injecting into the cell- causes lysis of the vacuolar membrane Escapes into the cytoplasm- rich intracellular soup replication occurs in the cytoplasm SHIGA TOXIN- interrupts cellular proteien synthesis IpaC - Answers (shigella) unique type of mobilty- no flagellae triggers actin polymerization at the end of the cell - gives it a "rocket propulsion for cell-to-cell spread. Vibrio - Answers 20 species have been identified 12 are responsible for human disease Vibrio cholerae - Answers "rice water stool" (mucus) 5-20 liters of water loss/day gram neg, motile "comma-shaped" bacterium Free-living and gut (pathogenic) Facultative anaerobe Capsule Pilus-attacehs to gut epitherlial cells Ferments glucose and sucrose Oxidase-postive LPS- 138 O serotypes non-invasive-remains attached to the cell surface Most prevalent virulent strains of Vibro Cholerae - Answers O1 and O139 TCBS Agar - Answers Vibrio cholerae show up yellow by low pH, acid, sucrose fermentor Cholera Virulence determinants - Answers Flagellae- motility is required to swim thru the mucus lining to the gut epithelial Pilus- attachment to gut cells HA protease- digest pillus and cholerae is shed from the gut to diarrhae- disppersed to other person via water/food Need a lot to get infected because its susceptible to stomach acid- needs to be in a buffer-food or in large amounts in water Cholera toxin - Answers Enterotoxin secreting into the lumen of the gut bind to receptor on surface of gut epithelial cells transported into host cells cytoplasm Elevates level of intracellular cAMP Stimulates the realse of K+ and NA+ from the cell and water follows Death by electrolytic shock conversion of avirulent strains of V. Cholerae - Answers lysogenic- cholera toxin genes become encoded on phage genome Campylobacter spp. - Answers Gastroenteritis caused by __________ is usually a self-limiting illness and does not require antibiotic therapy campylobacter spp. - Answers A "vibrio-like" bacterium In many animals- recently implicated in human disease Gram-neg "helical-shaped" bacillus Two polar Flagellae Capsule Dose NOT ferment(use) sugars Required CO2 for growth exceptionally small- need electon microscope C. jejuni - Answers Acute gastroenteritis Mucosal surface of intestine is ulcerated, edematous, bloody, inflamed Virulence feature not well-defined E.coli - Answers Non-pathogenic ecoli is a normal constituent of our gut flora- "commensal" or "symbiotic" Can infect many tissues and organs 45% of enteric infections gram-neg bacillus Faculative anaerobe Ferments glucose and lactose Can be flagellated or non-flagellated pili and/or fimbriae capsule or unencapuslated Genetically diverse