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Clinical Micro

Gram Negative Bacilli

QuestionAnswer
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