GRAM NEGATIVE COCCI Flashcards
Microscopic appearance of Neisseria
Gram-negative diplococci with coffee or kidney bean shaped
Except N. elongata and N. weaver (rod-shaped)
Culture morphology of Neisseria spp.
Small, gray-white opaque, convex, and glistening colonies
What medium is the growth of Neisseria best observed?
Enriched medium containing blood serum, cholesterol or oleic acid
Most of the colonies of Neisseria are non pigmented except…
N. flava
N. flavescens
N. subflava
Biochemical test:
Neisseria spp.
Oxidase (+)
Catalase (+) except N. elongata
Carbohydrate fermenters (primarily glucose and maltose)
Oxygen requirement and optimum temperature for growth of Neisseria
Facultative anaerobe; Capnophilic (2-8% CO2)
Moist temperature
They are sensitive to drying and extremes of temperature
N. gonorrheae
N. meningitidis
Natural habitat of Neisseria
Mucous membranes of the respiratory and urogenital tracts
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
Leading cause of sexually transmitted disease
Neisseria gonorrheae
Culture morphology Neisseria gonorrheae
Small, tan, translucent and raised after 24-48 hours of incubation (CAP)
The primary reason for their strict pathogenicity to humans is their ability to bind to transferrin
Neisseria gonorrheae
Principal virulence factor of Neisseria gonorrheae
Common pili
Produces IgA protease which is important in its pathogenesis (IgA is an antibody found in mucous membrane secretions)
Neisseria gonorrheae
Neisseria meningitidis
Virulent colonial type of Neisseria gonorrheae
T1 and T2
Avirulent colonial type of Neisseria gonorrheae
T3 to T5
Virulence factors of Neisseria gonorrheae
Common pili
Receptors for transferring
Capsule
IgA
Cellular membrane proteins (Por B)
Lipooligosaccharide (LOS) endotoxin
Rare isolates of Neisseria gonorrheae isolated from asymptomatic men
Susceptible to penicillin
More fastidious
Smaller in size
Auxotypes (AHU strains: arginine, hypoxanthine, and uracil)
Causative agent of the following clinical infections:
Gonorrhea
Purulent urethritis (males)
Cervicitis (females)
Pharyngitis
Anorectal infections
Conjunctivitis
Purulent arthritis
Neisseria gonorrheae
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
Bacteria responsible for sterility and perihepatitis (Fitz-Hugh-Curtis syndrome)
Neisseria gonorrheae
This syndrome occurs when gonococcal cervicitis is left untreated
Causative agent of ophthalmia noenetorum, an eye infection acquired during vaginal delivery through an infected birth canal
Neisseria gonorrheae
A gonococcal eye infection acquired during vaginal delivery through an infected birth canal
Conjunctivitis (ophthalmia neonatorum)
What swab is used to collect specimens for Neisseria gonorheae?
Dacron or rayon swabs
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
