Neisseriaceae and Antimicrobial Susceptibility Testing – Flashcards
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| Neisseriaceae |
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| Gram neg diplococci. Inhabit the mucous membranes of warm-blooded hosts. non-motile and non-spore forming. Grows in CO2 |
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| Neisseriaceae are catalse what? Oxidase what? |
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| Cat-Pos Ox-Pos |
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| Neisseria gonorrhoeae causes what in males? |
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| Urethritis Dyuria Urethral discharge |
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| Neisseria gonorrhoeae causes what in females? |
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| Endocervix infection, symptoms include: cervicovaginal discharge, lower ab pain, abnormal periods |
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| What are some populations with a high prevalence of neisseria gonorrhoeae? |
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| Low socioeconimic class Residence in urban areas Drug abuse Prostitute |
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| Lab identification of Neisseria gonorrhoeae? |
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| Grows in translucent, raised, moist, grayish-white colinies on CHOC or MTN agar. Produces bubbles to superoxol Can be identified usingMolecular probe technology |
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| MTM agar |
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| Selective media for Neisseria Contains: Vancomycin- Inhibits gram pos Colistin- Inhibits gram neg Nystatin- Inhibits yeasts Trimethylprym- Inhibits flagellar action of proteus. (Prevents from swarming) |
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| Neisseria gonorrhoeae carbohydrate test and enzyme test |
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| Carb test- Only glucose pos Enzyme test- Hydroxypropyl aminopeptidase positive |
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| What is the standard for diagnosis of Neisseria gonorrhoeae? |
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| Culture |
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| Neisseria meningiditis symptoms: |
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| Confusion, headache, fever. Causes petechiae which are small hemorrhagic skin lesions |
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| Neisseria meningiditis acute form |
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| Slight fever, respiratory tract symptoms |
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| Neisseria meningiditis chronic form |
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| Fever, rash, arthritis |
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| Spread of Neisseria meningiditis |
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| Spread by respiratory droplets or direct contact with respiratory secretions. Humans are the only host. |
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| Lab identification of Neisseria meningiditis |
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| The presence of inflammatory cells has prognostic value (with fulminant, rapidly fatal disease, many organisms are seem with few inflammatory cells) Colony on CHOC agar and MTM agar is similar to N. gonorrhoeae. Will grow on blood agar. |
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| Direct antigen detection |
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| Test used to identify Neisseria meningiditis. Performed to identify meningococcal capsular polysaccharides. Pos test is helpful for early diagnosis. Neg test does not rule out meningitis caused by other organisms. |
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| Neisseria meningiditis carbohydrate and enzyme test results |
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| Carb- Glucose and maltose positive Enzyme- Gamma glutamylaminopeptidase positive |
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| Neisseria species are normal flora of the |
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| Human respiratory tract |
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| N. subflava, N. mucosa, N. sicca and N. flavescens may cause what? |
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| Endocarditis in patients with prosthetic heart valves or IVDA |
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| N. lactamica |
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| Can grow on selective media. Isolated from genital sites, CSF and blood |
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| Lab results for other Neisseria spp. |
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| Carb test- Glucose, lactose and maltose pos Enzyme test- beta-D-galactosidase ONPG-hydrolyzed |
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| N. cinera |
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| Recovered from patients with AIDS as a cause of nosocomial pneumonia. Grows on BAP and CHOC |
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| N. cinera carb test and enzyme test |
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| Carb- No production of acid from carbs in the CTA-based or rapid carb tests. Weakly pos glucose has been reported for some automated systems. Enzyme test- Pos for hydroxypropyl aminopeptidase |
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| Colistin disk susceptibility test |
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| Can differentiate N. cinera from N. gonorrhoeae. N cinera= S. N gonorrhoae= R |
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| Only rod-shaped member of the genus Neisseria? |
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| N. elongata |
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| Moeraxella catarrhalis |
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| May cause lower respiratory tract infection in older people or those with chronic disease. Also causes otitis media and acute sinitis in children |
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| Opthalmia neonatorum |
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| Acquired through the acquisition of Moraxella catarrhalis at birth from the mother's colonized genital tract. |
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| Lab identification of Moraxella catarrhalis |
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| Grows on BAP and CHOC. Slides on agar. Carb test: assacharolytic Enzyme test: Neg for all enzymes tested. DNase: positive Chromogenic cephalosporin test: posive (Production of an inducible, cell-associated beta-lactamase) |
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| B. Cat disk |
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| Quick spot test used to identify Moraxella catarrhalis. The organism hydrolyzes the ester-linked butyrate in disk to produce a color change. |
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| MIC |
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| The minimum amount of antibiotics that can be used to inhibit the spread of an organism. |
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| Bacteriocidal |
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| Kills bacteria |
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| Bacteriostatic |
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| Prevents organism from growing. |
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| Procedure for an MIC |
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| Set up serial dilution with antimicrobial agent to determine which of the concentrations is the least concentration which prevents the organism from growing. To find the correct tube. Find the first tube in which the organism appears not to be growing |
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| MBC |
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| The minimum concentration of anitbiotic that will kill a specific microorganism. |
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| Procedure for MBC |
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| After performing a serial dilution with a specific organism and antibioticm, quantitatively subculture all clear wells to determine what the minimum concentration of antibiotic is that will kill the organism |
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| Which is larger: The bacteriocidal concentration or the bacteriostatic concentration? |
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| The bacteriocidal concentration |
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| Is it possible to perform an MBC on a cidal agent? |
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| Yes |
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| Is it possible to perform an MBC on a static agent? |
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| No because the agent will only prevent the organism from growing, not kill it |
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| Schlicter Test |
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| Involves using patient serum which is tested against a certain bacteria to see if it will kill it. |
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| What are some things that are important to standardize in antimicrobial testing? |
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| Conc of agent Conc of organism Standardized McFarland inoculation Size of disk Plate thickness How far apart discs are Incubation time Standardized zone of clearing Incubation temp Manufacture consistency |
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| Kirby-Bauer Susceptibility Test |
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| A method to determine the sensitivity of microorganisms to specific antimicrobial drugs; greater drug efficacy yields larger microbe-free zones surrounding drug-containing disks after overnight growth on solid media. (MIC Test) |
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| E-Test |
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| Quantitative technique for determining the antimicrobial susceptibility of microorganisms (MIC Test) |
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| How can you get a falsely resistant MIC? |
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| Not enough antibiotic Too much organism |
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| How can you get a falsely susceptible MIC? |
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| Too few organisms in tubes Too much antibiotics in tubes Dilution is off |
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| Set up a normal MIC using serial dilution |
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| 1. Make serial dilution by dividing each preceeding tube concentration by 2. (Take tube 1 conc and divide it in half and repeat) 2. Add TSB or Mueller-Hinton broth to each test tube 3. Add necessary amount of antibiotic to the first tube. Transfer the same amount of solution into the next tube and repeat for all tubes. 4. Need a growth control (no antibiotic) 5. Need a sterility control (no organism) |
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| Determine a normal MBC |
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| 1. Inoculate a plate for each clear tube that was present. Streak to obtain a colony count. 2. Incubate plates 3. Examine the plates for presence of growth of test organism. |
