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Clinical Micro
Gram Negative Bacilli
| Question | Answer |
|---|---|
| N. gonorrhoeae gram stain morphology | Gram negative diplococcus and appears intracellular in neutrophils |
| Gonorrhoeae is positive with: | Oxidase, catalase, glucose |
| Growth environment for N. gonorrhoeae | 5-10% CO2 at 35 degrees C |
| How is gonorrhoeae diagnosed in women? | Gram stain --> diplococcus from culture |
| Virulence factors of N. gonorrhoeae | Pili, Adhesion factors IgA protease Capsule - escapes phagocytosis Higher risk for patients with complement deficiencies |
| What N. gonorrhoeae causes: | Most common agent of septic arthritis in adults younger than 30 infections of the urethra, endocervix, anal canal, pharynx, and conjunctiva Second most reported STD Major cause of venereal disease Possibly mixed with chlamydia |
| Gonorrhea in males | 2-7 days on incubation. Discharge, Dysuria, prostatis, epididymitis |
| Gonorrhea in females | Urethral infections and cervicitis produce cervical discharge, fever, acute pain and dysuria cause pelvic inflammatory disease (PID), gonococcal arthritis, endometritis and peritonitis. PID may cause sterility |
| Gonorrhea treatment | most are positive for beta-lactamase production Treat with: Ceftriaxone susceptibility testing for quinolone |
| What is PPNG? | Penicillinase positive Neisseria gonorrhoeae |
| Treatment for Gonorrhea with concurrent Chlamydia? | 7 day regimen of doxycycline |
| Gonococcal Ophthalmia Neonatorum | severe conjunctivitis in neonates leading to blindness Infected by vaginal delivery |
| Treatment/prevention for Gonococcal Ophthalmia Neonatorum | antimicrobial eye drops are instilled within 1 hour of delivery Or treat with 1% tetracycline eye ointment or 0.5% erythromycin eye ointment |
| Neisseria meningitidis is positive for: | Maltose, oxidase, and glucose |
| Neisseria meningitidis colony morphology: | flat, smooth, gray to white on chocolate |
| Virulence factors of Neisseria meningitidis | antiphagocytic capsule. Cell wall endotoxin --> septic shock Pili IgA protease Capsule - antiphagocytic and determines is serogroup: A, B, C, Y, and W135 Higher risk for patients with complement deficiencies |
| Specimens for Neisseria meningitidis | CSF, sputum, blood, nasopharyngeal swabs |
| Natural habitat and transmission of Neisseria meningitidis | nasopharyngeal tract in humans. Transmission through droplets and close contact |
| Treatment for Neisseria meningitidis | Broad-spectrum cephalosporin |
| Two peak ages for Neisseria meningitidis infection? | babies 3-9 months old (immune system not fully developed) Teens in crowded conditions (dorms) Highest virulence is during winter. |
| Neisseria meningitidis pathogenesis | engulfed by epithelial cells and survive and multiply in the bloodstream Once bacteria reaches the subarachnoid space- proliferation is uncontrolled. Survivors can suffer from neurological sequelae |
| Complications of Neisseria meningitidis? | DIC Thrombocytopenia Petechiae |
| Treatment for meningococcal meningitis? | Rifampin and Ciprofloxacin |
| Vaccine for Neisseria meningitidis? | polysaccharide capsular antigens for groups A,C,Y, and W135 Group B is a poor immunogen |
| What is a good ID test for Neisserria? | rapid carbohydrate utilization |
| what is the indictor in the rapid carbohydrate utilization test? | Phenol red |
| What sugars are tested for? | Glucose, fructose, maltose, lactose |
| Mycobacteria characteristics | non spore forming nonmotile obligate aerobes environmental organisms use glycerol as a carbon source |
| Mycobacteria cell wall structure | high lipid content - 60% mycolic acids protects from dehydration, alkaline, germicides, alcohol acids Hydrophobic |
| Glycoprotein found in mycobacteria | N-glycolymuramic acid |
| Mycobacteria with gram stain | poorly stained gram-positive bacilli "gram ghosts" |
| Ziehl-Neelsen | Heat stain acid fast stain |
| Ziehl-Neelsen reagents | carbofuchsin, acid-alcohol (HCL), and methylene blue or malachite green |
| Difference between Ziehl-Neelsen and Kinyoun? | Doesn't use heat- replaces heat with Phenol Same reagents |
| How many fields are needed to examine for an acid-fast smear? | 300 fields before reporting negative |
| Advantages of a Fluorochrome stain? | Can be examined at lower magnification More sensitive than an acid-fast stain more fields can be examined faster can be re-stained using an acid-fast procedure |
| Reagents for Fluorochrome stain | auramine-rhodamine, acid-alcohol, and potassium permanganate |
| What does potassium permanganate do? | quenches and reduces the background fluorescence of cellular debris. |
| Lowenstein-Jensen agar - what's in it? | egg-based with malachite green to inhibit normal flora |
| Incubation of Lowenstein-jensen agar: | 5-10% CO2 at 35-37C for a week with loose caps and then 7 more weeks with tightened caps, protect from the light |
| Middlebrook 7H10/7H11 media | agar based contains 2% glycerol (support MAC growth) must be refrigerated and incubated in the dark |
| What happens with 7H11 agar is exposed to light? | May release formaldehyde which is toxic to mycobacteria |
| Benefits of liquid AFB media? | provide more rapid recovery of AFB than solid medium isolation rates are also higher |
| Mycobacterium growth index tube (MGIT) | contains 7H9 broth with larges amounts of O2 to quench the fluorescence of a fluorochrome |
| Incubation of mycobacteria? | 35C in the dark with 5-10% CO2 and high humidity. cultures held for 8 weeks before negative |
| Incubation of M marinum, M ulcerans, and M haemophilum? | (skin lesions) solid media at 25-30C |
| Semiquantitative catalase test: | All mycobacteria produce catalase Strains of TB are <45mm of bubbles Non-TB are >45mm of bubbles |
| Heat-sensitive catalase: | mycobacteria heated to 68C for 20 minutes with 30% H2O2 and 10% 80 TB strains are negative (no bubbles) |
| What does Niacin do? | plays an important role in the redox reactions that occur during mycobacterial metabolism It accumulates in the medium in which the organisms grow |
| Niacin test | should be performed on cultures 3 weeks or older if positive (yellow color) and colonies are buff color and rough - maybe M. TB |
| Nitrate test | M. TB and M. kansasii are positive |
| Arylsulfatase test | 3 day test M. fortuitum and M. chelonae are positive ability of enzyme to breakdown phenolphthalein disulfide into phenolphthalein turn red in presence of sodium bicarbonate |
| Thiophene-2-Carboxylic Acid Hydrazide (TCH) | differ M. bovis (susceptible) from M. TB (resistant) |
| Tween 80 | nonpathogenic, slow growing scotochromogens and nonphotochromogens production a lipase that is able to hydrolyze to oleic acid and polyoxyethylated sorbitol |
| Use of nucleic acid assays? | ID by DNA sequencing |
| AccuProbe | for M. TB and M. avium species highly specific takes less than 2 hours can use culture isolates |
| Direct nucleic acid amplification | Detects M. TB target: 16srRNA gene |
| Mycobacterium tuberculosis complex | M.tuberculosis M. Bovis M. africanum |
| What does NTM or MOTT stand for? | Nontuberculuous mycobacteria Mycobacteria other than M.TB |
| Characteristics of NTMs? | Slow growing opprotunisitc infections in AIDS Rapid growing Noncultiviable: M. leprae |
| Tuberculosis | ancient disease entered human population when cattle were domesticated |
| Transmission of Tuberculosis | Airborne: inhalation of tiny droplet - cause chronic lowe respiratory tract disease |
| TB suspect | Hemoptysis (coughing blood) Persistent cough for 3 or more weeks weight loss fever night sweats collect 3 specimens |
| Where can bacteria of TB spread? | lymphatic system, CNS, and heart |
| What does TB do to macrophages? | form multinucleated cells and form granulomas with other cells --> tubercles Lesions can calcify and make a ghon complex. |
| What causes a reactivation of TB? | alteration in the cell-mediated immune response poor nutrient, alcoholism, diabetes, |
| First line drugs for TB? | Rifampin, isoniazid, pyrazinamide, ethambutol, streptomycin |
| Miliary tuberculosis | lungs look like they have millet seeds |
| M. TB definitive ID | colonies on LJ appear non pigmented, dry, and granular roselike formation from broth culture on acid-fast stain Niacin positive Nitrate positive 68C catalase positive NAP susceptible |
| Tests for TB | Skin test purified protein derivative (PPD) test - antigen is composed of heat-killed, filtered, ammonium sulfate precipitated protein |
| PPD results | person who has been infected by TB will show erythema and induration firmness |
| QuantiFERON -TB gold test | measure cell-mediated immune response to M TB |
| Runyon Classification of NTM | Made in 1959 based on phenotypic characteristics - growth rate and colonial pigmentation |
| Photochromogens | colonies are pigmented when exposed to light. Pigment is controlled by an O2-dependent light inducible enzyme M. kansasii |
| Scotochromogens | colonies are pigmented weather grown in dark or light M. scrogulaceum |
| Nonphotochromogens | No pigment M. avium |
| Rapid growers | appear on media in <7days |
| M. bovis | zoonosis pulmonary infections in cattle and humans nonphotochromogen TCH susceptible |
| M. avium complex | M.avium and M.intracellularae from water, soil, and dairy products affects immunocompromised causes lymphadenitis in children slow growing non-chromogen |
| M. kansasii | from tap water pulmonary infections - resembles TB but cannot disseminate in healthy patients most common slow growing photochromogen Nitrate and Catalase positive |
| M.xenopi | from water - hot water taps transmitted in aerosols pulmonary infections in adults |
| M.ulcerans, M.marinum, and M.haemophilum | skin infections grow on surface of extremities because optimal temperature 30-32 |
| Causative agent of swimming pool granuloma? | M. marimum develop granulomatous skin lesions |
| M.fortuitum, M.chelonae, M.abscessus | causes abscesses and osteomyelitis weakly virulent rapidly growing mycobacteria |
| M.gordonae | found in fresh and tap water rarely pathogenic slow growing scotochromogen |
| M.scrofulaceum | Causes cervical lymphadenitis mainly in children slow growing scotochromogen |
| Diagnosis of leprosy | Hypopigmented skin lesion skin-smar positive for acid-fast bacilli OCR |
| Optimal temperature for M. leprae - leprosy | 33 C |
| Transmission of M. leprae | person to person through inhalation or contact with infected skin Armadillos are carriers |
| Signs of leprosy | discolored light patches on skin and loss of feeling affects nerves: numbness, paralyzed muscles |
| Treatment of Leprosy | rifampin, clofazimin, and dapsone |
| TB Specimen collection and transport | Urine: morning sputum or bronchoscope aspirations feces 10cc of CSF blood wounds, skin lesions |
| Transport medium for TB specimens? | Amies or Stuarts medium |
| N-acetyl-L-Cysteine (NALC) | mucolytic agent is used to digest mucus and free trapped mycobacteria. |
| Specimen treated with NaOH | increases the pH to a level that is antibacterial |
| What is resistance due to? | Non adherence Incorrect drug prescription Poor quality of drugs erratic supply of drugs |
| Multidrug-resistant M.tuberculosis (MDR-TB) | Resistance to isoniazid and rifampin poor prognosis |
| Extremely-drug resistant M.tuberculosis(XDR-TB) | Resistance to any fluoroquinolone at least one of three injectable second-line drugs in addition to isoniazid and rifampin. |
| Vaccines for TB | Bacille Calmette-Guerin - BCG derived from M. bovis |
Created by:
Mirielles
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