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Micro lecture 17
| Question | Answer |
|---|---|
| Characteristics of Mycobacteria | Gram-variable, acid-fast, slender, straight or slightly curved rods; aerobic growth |
| What kind of cell wall do Mycobacteria have? | Hydrophobic due to MAPc layer. This makes them slow growers. |
| What kills Mycobacteria? | UV light, sunlight, pasteurization |
| What is the "Gold Standard" for identifying M. tuberculosis? | Lowenstein-Jensen agar (PIC: yellow growth on malachite-green) or Middlebrook agar. Takes 3-8 weeks to grow on solid media. |
| What does Cord factor do? | promotes formation of cord-like clumps |
| How is tuberculosis acquired? | inhalation of the bacterium within droplet nuclei |
| Where is a weird spot M. tuberculosis can survive? | in activated macrophages |
| What is the classical response against M. tuberculosis? | Formation of a granuloma (tubercle) to contain the infection. Granuloma may heal by fibrosis and calcification but may contain viable bacteria for many years. |
| Caseous necrosis cons | unstable, tends to liquify with discharge into bronchial tree, producing a bacteria breeding ground |
| disseminated (miliary) TB | in which tubercles are found in many organs. |
| M. leprae | leprosy |
| What are the 2 types of leprosy? | Tuberculoid leprosy and lepromatous leprosy |
| Tuberculoid leprosy | red, blotchy skin lesions, thick nerve sheaths, local anesthesia on face, trunk, and extremities, good response to lepromin, better prognosis than lepromatous leprosy. |
| Lepromatous leprosy | little to no response to lepromin; bacilli at very high levels, skin and nerves involved with loss of local sensation resulting in amputations and trauma. |
| Characteristics of Nocardia | filamentous, branched, Gram-positive, non-spore-forming, partially acid-fast; aerobic soil organism |
| What do N. asteroides and N. brasiliensis cause? | chronic pneumonia with abscesses, necrosis, and cavity formation |
| How is Nocardia acquired? | inhalation or traumatic introduction |
| What does Nocardia look like on a slide? | long, delicate and branching |
| What agar should Nocardia be grown on? | buffered charcoal yeast extract. it's because Nocardia can be slow-growing and can be overtaken by other organisms. BCYE is selective. |
| What are the 4 acid-fast genera? | Mycobacterium tuberulosis & Mycobacterium leprae; Cryptosporidium & Cyclospora oocysts; Nocardia |
| Actinomyces characteristics | anaerobic, filamentous, branching growth. Growth kinda looks like fungi (hence... "myco").Fragments into slender Gram-positive rods. Non-spore forming. Cell wall w/peptidoglycan. |
| Where do actinomyces live? | small spaces between teeth, caecum. causes infections in decayed teeth, lungs, and intestines. |
| What does actinomyces look like in a colony? | like a bunch of molars... remember this to remember where they grow. In a gram stain, they look like a nasty shower drain of long black hairs ew. |
| Cervicofacial actinomyces | Leaves a big hole in your cheek/jawline and your sinuses drain through it and EW. |
| Proprionibacteria characteristics | Small Gram-positive bacilli; arranged in short chains/clumps; found on skin, conjunctiva, external ear, oropharynx, female genital tract; anaerobic/aerotolerant; ferments carbs |
| P. acnes causes... | acne (duhhh) |
| What does Proprionibacteria look like on a gram stain? | V-shaped or "chinese character" arrangements |
| Name the Gram-negative pathogens | Neisseria, Moraxella, Acinetobacter |
| Neisseria characteristics | Aerobic; Oxidase-positive; Gram-negative diplococci with adjacent sides flattened together (look like coffee beans); non-motile, non-spore forming; most produce catalase; produce acid via CHO oxidation |
| N. gonorrhoeae | Produces acid by oxidizing glucose; Fastidious, use Thayer-Martin agar at 35-37deg C; cold sensitive |
| N. meningitidis | Produces acid by oxidizing glucose and maltose; visible growth on nutrient agar; has a polysaccharide capsule protecting it from phagocytosis |
| oh jesus eye gonorrhea | oh god why is this on my screen |
| Gonococci in joints cause | arthritis |
| Gonococci in meninges cause | meningitis |
| Gonococci in heart cause | endocarditis |
| Pilin protein of fimbrae (pili) | Provide attachment to nonciliated human cells of moist membranes. Provide resistance to killing by PMNs. Evade immune system and allow reinfection due to antigenic variation and phase variation. |
| antigenic variation between pilin proteins | having a slightly different amino acid sequence |
| phase variation in pilin expression | reversible switch between piliated and nonpiliated states |
| Por protein | Porin proteins of outer membrane are used for serotype classification |
| Opa proteins (opacity proteins) | mediates firm attachment to each other and to eukaryotic cells |
| Iron obtaining mechanisms | Mediates acquiring iron for bacterial metabolism |
| LOS (lipo-oligosaccharide) | has endotoxin activity; has lipid A but lacks O-antigen polysaccharide. Both Neisserial pathogens shed blebs of outer membrane as they grow. |
| IgA Protease | cleaves IgA hinge |
| Virulence factors of N. gonorrhoeae | Pilin protein, Por protein, Opa protein, Iron obtaining mechanisms, LOS, IgA protease |
| Virulence factors of N. meningitidis | Capsule, pili permit attachment to nasopharynx, survive inside PMN, LOS (endotoxin) mediates most clinical symptoms |
| Endemic | disease present to a greater or lesser extent in a particular locality |
| epidemic | disease or anything resembling a disease attacking or affecting many individuals in a community or a population simultaneously |
| How does meningitis make it to the meninges? | entry from the blood across the choroid plexus to the CSF and meninges. |
| What serotypes of meningitis cause most of the infections? | A, B, C, Y, and W135. |
| All but B have _________ | a vaccine against them |
| Why doesn't the group B have a vaccine? | Group B is a weak immunogen and does not induce a protective antibody response. |
| Moraxella and Acinetobacter characteristics | nonmotile, gram negative coccobacilli; can be confused with neisseria in gram stains |
| Moraxella catarrhalis characteristics | oxidase positive; causes middle ear infections |
| Acinetobacter characteristics | oxidase negative, A. beaumannii is an important nosocomial pathogen resistant to many antibiotics |
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