GRAM NEGATIVE COCCI Flashcards by Antea Eper

Microscopic appearance of Neisseria

Gram-negative diplococci with coffee or kidney bean shaped

Except N. elongata and N. weaver (rod-shaped)

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Culture morphology of Neisseria spp.

Small, gray-white opaque, convex, and glistening colonies

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What medium is the growth of Neisseria best observed?

Enriched medium containing blood serum, cholesterol or oleic acid

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Most of the colonies of Neisseria are non pigmented except…

N. flava
N. flavescens
N. subflava

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Biochemical test:

Neisseria spp.

Oxidase (+)
Catalase (+) except N. elongata
Carbohydrate fermenters (primarily glucose and maltose)

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Oxygen requirement and optimum temperature for growth of Neisseria

Facultative anaerobe; Capnophilic (2-8% CO2)
Moist temperature

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They are sensitive to drying and extremes of temperature

N. gonorrheae
N. meningitidis

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Natural habitat of Neisseria

Mucous membranes of the respiratory and urogenital tracts

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A gram negative intracellular diplococci, kidney or coffee-bean shaped, that is transmitted by sexual contact, or congenital transmission. They are found in the urogenital tract, anorectal area, oropharynx, and conjunctiva. It is not part of the normal flora and man is the only known host.

Neisseria gonorrheae

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Leading cause of sexually transmitted disease

Neisseria gonorrheae

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Culture morphology Neisseria gonorrheae

Small, tan, translucent and raised after 24-48 hours of incubation (CAP)

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The primary reason for their strict pathogenicity to humans is their ability to bind to transferrin

Neisseria gonorrheae

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Principal virulence factor of Neisseria gonorrheae

Common pili

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Produces IgA protease which is important in its pathogenesis (IgA is an antibody found in mucous membrane secretions)

Neisseria gonorrheae
Neisseria meningitidis

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Virulent colonial type of Neisseria gonorrheae

T1 and T2

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Avirulent colonial type of Neisseria gonorrheae

T3 to T5

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Virulence factors of Neisseria gonorrheae

Common pili
Receptors for transferring
Capsule
IgA
Cellular membrane proteins (Por B)
Lipooligosaccharide (LOS) endotoxin

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Rare isolates of Neisseria gonorrheae isolated from asymptomatic men
Susceptible to penicillin
More fastidious
Smaller in size

Auxotypes (AHU strains: arginine, hypoxanthine, and uracil)

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Causative agent of the following clinical infections:

Gonorrhea
Purulent urethritis (males)
Cervicitis (females)
Pharyngitis
Anorectal infections
Conjunctivitis
Purulent arthritis

Neisseria gonorrheae

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Meaning “flow of seed” and “brothel”, is an acute pyogenic infection of non-ciliated columnar and transitional epithelium with a short incubation period of 2-7 days; patients may be asymptomatic

Symptoms: purulent discharge, lower abdominal pain and dysuria (men); dysuria and vaginal bleeding (women)

What is the infection and its causative agent?

Gonorrhea caused by Neisseria gonorrheae

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Bacteria responsible for sterility and perihepatitis (Fitz-Hugh-Curtis syndrome)

Neisseria gonorrheae

This syndrome occurs when gonococcal cervicitis is left untreated

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Causative agent of ophthalmia noenetorum, an eye infection acquired during vaginal delivery through an infected birth canal

Neisseria gonorrheae

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A gonococcal eye infection acquired during vaginal delivery through an infected birth canal

Conjunctivitis (ophthalmia neonatorum)

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What swab is used to collect specimens for Neisseria gonorheae?

Dacron or rayon swabs

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Transport medium for Neisseria gonorrheae

Amies medium with charcoal

Neisseria gonorrheae swab specimens placed in transport systems need to be plated within how many hours?

6 hours

Cotton swabs are considered toxic to this bacteria due to the presence of toxic fatty acids in the cotton fiber

Neisseria gonorrheae

How are blood specimens for Neisseria gonorrheae collected?

Blood is first collected in vacutainer tubes and then transferred to the broth culture system within one hour of collection. Routine blood cultures aren’t used because they are inhibited by SPS.

Body fluids (like joint fluid or CSF) is kept at what temperature?

Kept at RT or placed at 37ºC before plating

Urethritis with >5 PMN/field but no bacteria

Non-gonococcal urethritis (C. trachomatis)

Extracellular gram-negative diplococci are the ________ forms of Neisseria gonorrheae

Avirulent forms

What specimen is used for gram staining Neisseria gonorrheae?

Urogenital specimens Pharyngeal specimens are not used because commensal Neisseria spp. may be present

Why are direct gram stains of bodily fluids cytocentrifuged?

Direct gram stain is best accomplished with cytocentrifugation because this concentrates small numbers of organisms (100 fold)

Biochemical test results: Cystine Trypticase agar: yellow color within 24-27 hours at 35-37ºC Oxidase test: purple Superoxol test: vigorous bubbling Cephalosporinase test: deep pink/red color within 10 minutes Beta lactamase: (+) DNAse test: (-)

Neisseria gonorrheae

Biochemical test: Neisseria gonorrheae

Glucose fermenter Oxidase (+) Superoxol test (+) Cephalosporinase test (+) within 10 minutes Beta lactamase (+) DNAse (-)

Confirms the biochemical identification using monoclonal antibodies directed against N. gonorrheae attached to killed S. aureus cells

Coagglutination

A highly specific and sensitive test that uses monoclonal antibodies that recognize epitopes on the principal other membrane protein (Por) of N. gonorrheae. it also confirms the morphologic appearance of the bacteria

Fluorescent antibody test (FAT)

This test detects gonococcal antigen or nucleic acid directly in specimens. It has the advantage of having the ability to test for Chlamydia trachomatis at the same time; less sensitive for transport and storage conditions. It is also suitable for screening many patients simultaneously.

Molecular assays - Nucleic acid amplification

This test is a rapid, direct detection of gonococcal rRNA in genital and conjunctivital specimens. Its disadvantage is that it is not approved for pharyngeal or rectal specimens; cannot identify B-lactamase-producing strain; not applicable for susceptibility testing

Chemiluminescent Nucleic acid probe

Virulence factor of Neisseria meningitidis

Pili Polysaccharide capsule IgA1 Cellular membrane proteins (Por A and Por B) LOS endotoxin

Causative agent of spotted fever

Neisseria meningitidis Other names for spotted fever: epidemic meningococcal meningitis / meningococcemia / cerebrospinal fever

Leading cause of fatal bacterial meningitis

Neisseria meningitidis

Microscopic appearance of Neisseria meningitidis

Intracellular or extracellular gram negative diplococci Encapsulated strains can have a halo around organism

It may be found as a commensal inhabitant of the upper respiratory tracts of the carriers; it colonizes the mucous membranes of nasopharynx and oropharynx

Neisseria meningitidis

Has the tendency to invade serous and joint fluids, causing pleuritis and arthritis

Neisseria meningitidis

Biochemical test: Catalase (+) Oxidase (+) Superoxol (-) Gamma-glutamyl aminopeptidase test (+) Glucose and maltose fermenter; requires iron for growth

Neisseria meningitidis

Biochemical test: Neisseria meningitidis

Catalase (+) Oxidase (+) Superoxol (-) Gamma-glutamyl aminopeptidase test (+) Glucose and maltose fermenter; requires iron for growth

It refers to the presence of Neisseria meningitidis in the blood and can occur as an acute or chronic form. It occurs with or without meningitis. Source of epidemics: oral secretions and respiratory droplets (person-to-person) Signs and symptoms: frontal headache, stiff neck, fever (epidemic meningitis in adults)

Menigococcemia

What skin lesion develops during bacteremic spread due to release of endotoxin after bacterial cell lysis?

Petechial skin lesions

This complex activates the clotting cascade, depositing fibrin in small vessels, producing hemorrhage on the adrenals (Waterhouse-Friderichsen), altering peripheral vascular resistance, and leading to shock and death. What complex and what bacteria is responsible?

LOS-endotoxin complex in Neisseria meningitidis

People with deficiency in complement C5-C8 are at risk of…

Meningococcemia

DOC for meningococcal meningitis

Penicillin G

The colony morphology is similar to T3 colonies of N. gonorrheae on CAP

Neisseria cinerea

Differentiates N. cinerea from N. gonorrheae

Colistin susceptibility

Yellow-pigmented Neisseria spp. assacharolytic

Neisseria flavescens

Commonly found in the nasopharynx of infants and children. It is isolated from meningococcal carrier surveys, commonly from children 2 years old and rarely in adults.

Neisseria lactamica

It is usually isolated from the nasopharynx of children or young adults. It has also been isolated from airways of dolphins.

Neisseria mucosa

Culture morphology: Dry, wrinkled, adherent and breadcrumbs-like colonies

Neisseria sicca

A rod-shaped gram negative cocci with a weakly positive or negative catalase test

Neiserria elongata

A rod-shaped gram negative cocci that is a normal oral microbiota in dogs and can be found in humans in infections following dog bites

Neisseria weaveri

The most commonly isolated moraxella

Moraxella catarrhalis

Moraxella is part of the normal flora of…

Upper respiratory tract (oropharynx)

3rd most common cause of otitis media and sinusitis in children

Moraxella catarrhalis

Culture morphology of Moraxella catarrhalis

Smooth, opaque, gray to white colonies with “honey puck” appearance Colonies remain intact when pushed across the plate with a loop 48-hour colony may have elevated center, thinner wavelike periphery— “wagon wheel appearance”

Definitive diagnosis of Moraxella catarrhalis

Butyrate esterase (+)

Biochemical test: Moraxella catarrhalis

Oxidase (+) Catalase (+) Asaccharolytic DNAse (+) Butyrate esterase (+) Nitrate reduction (+)

Is a chocolate agar with an enrichment supplement (IsoVitaleX) and antibiotics (vancomycin, colistin, and nyacin)

Thayer Martin Agar

Antibiotics present in Thayer Martin Agar

Vancomycin Colistin Nystatin

Vancomycin inhibits the growth of...

Gram positive bacterias

Colistin inhibits the growth of

Gram negative except Neisseria

Nystatin inhibits the growth of...

Fungi

Components of Modified Thayer Martin Agar (MTM)

Enrichment supplement (IsoVitaleX) Antibiotics (vancomycin, colistin, nystatin) Trimethoprim lactate

Composition of Martin Lewis Medium (ML)

(MTM + nystatin replaced with anisomycin) Enrichment supplement (IsoVitaleX) Antibiotics (vancomycin, colistin, anisomycin) Trimethoprim lactate

A transparent medium with lysed horse blood, horse plasma, and yeast dialysate Antimicrobial agents: vancomycin, colistin, trimethoprim, and amphotericin B Advantage: genital mycoplasma will also grow on this agar

New York City Medium (NYC)

What medium is used to isolate Neisseria gonorrheae?

New York City Medium (NYC)

What medium contains NYC antibiotics + lincomycin

GC-LECT medium

What is the purpose of gamma glutamyl aminopeptidase test?

The substrate, gamma glutamyl aminopeptidase is used to distinguish between gonococci and meningococci

What requirement is followed for the inoculation of Neisseria?

The sensitivity of Neisseria to drying and extreme temperatures requires them to be directly inoculated at the bedside

Culture morphology of Neisseria meningitidis

Encapsulated strains are mucoid in appearance; bluish gray-colonies (BAP) Small, tan, mucoid colonies (CAP)

Microscopic appearance of Neisseria meningitidis

Gram-negative intracellular diplococci

Requires iron for growth

Neisseria meningitidis Neisseria gonorrheae

Major pathogens of Neisseria

Neisseria gonorrheae Neisseria meningitidis

GRAM NEGATIVE COCCI Flashcards

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