Transcript CLSC 3033 MEDICAL MICROBIOLOGY
The Gram-Negative Cocci
Case Study
A 20-year-old female college student complained of a low-grade fever and pain, redness, and swelling of several of her joints Aspirates from both ankles and an elbow showed many PMNs and gram-negative intracellular and extracellular diplococci Cultures on Thayer-Martin and MacConkey agar failed to produce growth after 5 days of incubation W.B. Saunders Company items and derived items copyright © 2001 by W.B. Saunders Company.
Points to Consider
What special growth requirements should be available to these organisms to be recovered from clinical samples?
What virulence factors do these organisms use to produce disease?
What complications may develop from initial forms of infections?
How are these organisms identified?
Other points to consider W.B. Saunders Company items and derived items copyright © 2001 by W.B. Saunders Company.
The Pathogenic Neisseria Species and
Moraxella catarrhalis
General characteristics Aerobic, gram-negative diplococci Oxidase-and catalase-positive
Neisseria elongata
rod-shaped) is an exception (catalase-negative and Exist as usual flora in the upper respiratory and urogenital tracts Primary pathogens include
N. gonorrhoeae meningitidis
and
N.
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Neisseria gonorrhoeae
Virulence factors Fimbrae (common pili) enhance the ability of bacterial cells to adhere to host cells and to each other Lipopolysaccharide: resembles that of other gram-negative organisms W.B. Saunders Company items and derived items copyright © 2001 by W.B. Saunders Company.
Neisseria gonorrhoeae:
Virulence factors
Outer membrane proteins Protein I (PI): demonstrated in patients with disseminated disease; also found in rectal cultures of male homosexuals; resistant to serum bactericidal effects Protein II (PII): sensitive to bactericidal effects; associated with adherence to mucosal cells Protein III (PIII)-major binding site for immunoglobin-G – blocking antibody W.B. Saunders Company items and derived items copyright © 2001 by W.B. Saunders Company.
Neisseria gonorrhoeae:
Clinical Infections
Disease in the male Incubation period: 1 to 7 days Transmitted only by intimate sexual contact 95% show symptoms of acute infection Symptoms include dysuria, urethral discharge Complications include epididymitis and urethral stricture, and prostatitis W.B. Saunders Company items and derived items copyright © 2001 by W.B. Saunders Company.
Neisseria gonorrhoeae:
Clinical Infections
Disease in the female 20% to 80% are asymptomatic Symptoms (if symptomatic) include burning or frequency of urination, vaginal discharge Fever and abdominal pain Complications include pelvic inflammatory disease (PID) W.B. Saunders Company items and derived items copyright © 2001 by W.B. Saunders Company.
Neisseria gonorrhoeae:
Infections in Other Sites
Disseminated gonococcal disease Acute form has the following symptoms: fever, chills, malaise, intermittent bacteremia, and skin lesions If untreated will progress to septic joint form of the disease Gonococcal arthritis occur as a result of disseminated gonococcal bacteremia W.B. Saunders Company items and derived items copyright © 2001 by W.B. Saunders Company.
Neisseria gonorrhoeae:
Infections in Other Sites
Disease in children In infancy, an eye infection (ophthalmia neonatorum) may occur during vaginal delivery Infection is preventable with the application of eye drops at birth Extragenital infections Pharyngitis Anorectal infections W.B. Saunders Company items and derived items copyright © 2001 by W.B. Saunders Company.
Laboratory Diagnosis:
Neisseria gonorrhoeae
Clinical specimens Genital sites Anal- oral/pharyngeal Eye Blood/joint fluids Transport media: Transgrow or JEMBEC JEMBEC W.B. Saunders Company items and derived items copyright © 2001 by W.B. Saunders Company.
Laboratory Diagnosis:
Neisseria gonorrhoeae
Identification Morphology
Gram-negative, kidney bean –shaped diplococci A direct gram-stained smear of male urethral discharge showing intracellular gram negative diplococci
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Laboratory Diagnosis:
Neisseria gonorrhoeae
Identification
Inoculated culture media must be incubated at 35 0 C in 3% to 5% CO 2
Colony morphology on modified Thayer-Martin (MTM) agar
Small, gray
Translucent, raised
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Laboratory Diagnosis:
Neisseria gonorrhoeae
Candle extinction jar with inoculated MTM agar plates.
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Laboratory Diagnosis:
Neisseria gonorrhoeae
Identification Oxidase test Carbohydrate utilization test; acid produced only in the glucose tube indicates that the isolate is
N. gonorrheoae
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Neisseria meningitidis
General characteristics Exclusively human parasite Exist as harmless member of normal upper respiratory flora Identical with
Neisseria gonorrhoeae
Antigenic structures Capsular polysaccharide: nine serotypes — B, C, D, X, Y, Z, W135, 29E.
Contribute to invasive properties by inhibiting phagocytosis A, W.B. Saunders Company items and derived items copyright © 2001 by W.B. Saunders Company.
Neisseria meningitidis:
Clinical Infections
Bacterial meningitis Transmission is by respiratory droplets and requires both close contact and lack of specific antibody (susceptibility) Symptoms include fever, headache, stiff neck, nausea, vomiting, and purulent meningitis with increased WBCs W.B. Saunders Company items and derived items copyright © 2001 by W.B. Saunders Company.
Neisseria meningitidis:
Clinical Infections
Bacteremia (meningococcemia)
Appearance of skin petechiae Hemorrhage in the adrenal glands in W-F syndrome
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Laboratory Diagnosis:
Neisseria meningitidis
Identification Examine direct smear from CSF
Gram-stained smear of CSF showing the extracellular and intracellular gram negative diplococci
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Laboratory Diagnosis:
Neisseria meningitidis
Identification
Examine cultures on blood agar and chocolate agar plates
Oxidase-test –positive
Conventional CTA carbohydrates for biochemical identification or immunologic methods are available for serogrouping
Neisseria meningitidis
growing on sheep blood agar (right) and chocolate agar (left)
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Other “Related” Species
Moraxella catarrhalis
Normal commensal of the respiratory tract Has become an important opportunistic pathogen Clinical infections Pneumonia Sinusitis Otitis media Predisposing factors Advanced age Immunodeficiency Neutropenia Other debilitating diseases W.B. Saunders Company items and derived items copyright © 2001 by W.B. Saunders Company.
M. catarrhalis Moraxella catarrhalis
growing on chocolate agar after 48 hours of incubation Direct smear from an otitis media sample showing intracellular gram-negative diplococci; M. catarrhalis was identified from cultures
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Identification of Selected Neisseria Species
Species
N. gonorrhoeae N. meningitidis N. lactamica N. sicca M.
catarrhalis
Growth BAP R.T T/M Acid production Gluc Mal Lac Suc + + + =/+ + = = v + + + + + = = + + + + + + = = = + = = + = = = = = + =
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Points to Remember
Clinically significant
Neisseria
species Other related opportunistic pathogens Clinical infections associated with pathogenic species Complications that may result from these infections Methods of identifying important species W.B. Saunders Company items and derived items copyright © 2001 by W.B. Saunders Company.