the gram-negative cocci. w.b. saunders company items and derived items copyright © 2001 by w.b....

The Gram-Negative Cocci

W.B. Saunders Company items and derived items copyright © 2001 by W.B. Saunders Company.

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


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


The Pathogenic Neisseria Species and Moraxella catarrhalis

General characteristics Aerobic, gram-negative diplococci Oxidase-and catalase-positive Neisseria elongata is an exception (catalase-negative and

rod-shaped) Exist as usual flora in the upper respiratory and urogenital

tracts Primary pathogens include N. gonorrhoeae and N.

meningitidis


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


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


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


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)


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


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


Laboratory Diagnosis:Neisseria gonorrhoeae

Clinical specimens Genital sites Anal- oral/pharyngeal Eye Blood/joint fluids

Transport media: Transgrow or JEMBEC

JEMBEC


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



Identification Inoculated culture media

must be incubated at 350

C in 3% to 5% CO2

Colony morphology on modified Thayer-Martin (MTM) agarSmall, gray Translucent, raised



Candle extinction jar with inoculated MTM agar plates.



Identification Oxidase test

Carbohydrate utilization test;acid produced only in the glucose tube indicates that the isolate is N. gonorrheoae


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— A,

B, C, D, X, Y, Z, W135, 29E. Contribute to invasive properties by inhibiting phagocytosis


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


Neisseria meningitidis:Clinical Infections

Bacteremia (meningococcemia) Appearance of skin petechiae

Hemorrhage in the adrenal glands in W-F syndrome


Laboratory Diagnosis:Neisseria meningitidis

Identification Examine direct smear

from CSF

Gram-stained smear of CSF showing the extracellular and intracellular gram-negative diplococci


Neisseria meningitidis growing on sheep blood agar (right) and chocolate agar (left)

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


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


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


Identification of Selected Neisseria Species

Species GrowthBAP R.T T/M

Acid productionGluc Mal Lac Suc

N. gonorrhoeae

N. meningitidis

N. lactamica

N. sicca

M. catarrhalis

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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

the gram-negative cocci. w.b. saunders company items and derived items copyright © 2001 by w.b....

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