NEISSERIA MENINGIDITIS (MENINGEOCOCCUS): Gram-negative diplococcus
BACTEREMIAS
Only cause disease when in bloodstream
NEISSERIA MENINGIDITIS (MENINGEOCOCCUS): Gram-negative diplococcus
Name-Derivation:
Epidemiology / At Risk: Communicable bia inhaled droplets.
#2 cause of infantile meningitis.
Transient normal flora of throat.
Manifestations:
Meningeococcemia: Bugs in the bloodstream leads to a rash with lots of bugs in it.
Gram negative DIC and shock are possible complications.
Meningitis: Vomiting and fever may be the only signs in infants. No treatment leads to death.
Processing:
Specimen: CSF, rash exudate, blood, synovial fluid.
Stain:
Mostly extracellular gram-negative cocci. Because of their thick capsule they are not phagocytosed.
Lots of PMN's.
Culture: Smooth colonies. Capsule.
Thayer-Martin (chocolate agar with antibiotics)
Sterile specimens (CSF, blood) will can be grown on chocolate agar alone.
CO2
Subculture for glucose / maltose fermentation tests.
Identification:
Catalase(+), Oxidase(+): Neisseria
Glucose-fermenting, Maltose-fermenting (Meningidits)
Serotypes: Based on the capsule antigen.
A,B,C,D,29E: Originally known to be virulent
W135,X,Y,Z: Orginally thought to be harmless; now it's known otherwise.
Type-B is the most virulent because it is not immunogenic -- we cannot make protective antibodies against it.
It is made out of alpha-2,8-n-acetylneuraminic acid. It is rapidly degraded and thus not immunogenic.
Quellung Reaction: Add antiserum to look for Type-B. Swelling shows positive test.
CIE, Latex Agglutination: On CSF or urine. Two specific antibody tests to look for capsular antigens.
Virulence:
Cell-Associated:
Capsule: Thick polysaccahride determining the serogroup. Antiphagocytic.
Type-B is not immunogenic.
Outer Membrane Proteins: Another basis for serotyping.
They are being used to search for a conjugate vaccine.
They have homology with the Outer Membrane Proteins (I thru III) of N.Gonorrhea.
LPS: Induces the Schwartzman Reaction. Causes the rash and can lead to necrosis.
Pili: Adhesins in upper respiratory tract.
Enzymes:
IgA Protease: Two types, cleaves bonds at hinge region of IgA1
Oxidase
Needs Iron: Iron is taken up by an energy-dependent (not siderophore) mechanism.
Host Immune Response: Serological
Antibody is essential to phagocytosis of this bug.
Problem: cross-reacting antigens (E.Coli, E.Fecaelis) stimulate IgA, which blocks IgM, hindering serum immunity. Not good.
Group-B can be phagocytosed but remains serum resistant.
Vaccine / Prevention: Given to military recruits. Contains A, C, Y, W135. Naturally it doesn't contain B because Type-B is not immunogenic!
Vaccine can only be given to people older than two.
Treatment: Prophylactic antibiotic treatment for kids younger than 6 years old, with documented contact with an index case.
BRUCELLOSIS: Small gram-negative rod (coccobacillus)
Species
B. Melitensis goat
B. Abortus cattle
B. Suis pig
B. Canis dog
Epidemiology / At Risk: Zoonotic. Cattle ranchers and people who handle cattle.
Manifestations: Undulating Fever, Bang's Disease
Infecting organisms go into bloodstream and then are taken up by fixed RES macrophages, where they reside happily.
Organisms are occassionally released from fixed macrophages and go back into the bloodstream. Fever waxes and wanes according to the presence of organisms in the bloodsteam.
Symptoms: Fever, chills, sweats, myalgia, weakness, recurring at 10-day intervals.
Chronic disease causes microabscesses, granulomas, and caseation in the spleen and liver.
This results from Type-IV cell mediated response to the bugs.
Processing:
Specimen: Blood, bone marrow
Stain: Not useful
Culture: Brucella Agar = Selective Agar containing Erythritol, which the bugs subsist on.
Erythritol is found in reproductive tract of cattle, hence these bugs cause abortion in cattle. Humans don't have erythritol so no abortion happens.
Identification:
Facultative Intracellular Parasite of macrophages
Catalase (+)
Oxidase (+)
Gas-liquid chromatography can be used to identify the species.0
Virulence:
Catalase
5'-GMP, Adenine: They inhibit the release of peroxidase by PMN's, thus hindering the halide pathway of killing.
Facultative Intracellular Parasite of macrophages
LPS: Responsible for fever.
Host Immune Response:
IgM persists throughout infection. IgG waxes and wanes with fever.
IgG blocks IgM's bactericidal action in the serum.
Acute:Convalescent titer of 1:160.
Vaccine / Prevention: Cattle are vaccinated in Kansas. Live attenuated B.Abortus.
LISTERIA MONOCYTOGENES: Gram (+) pleomorphic rods
Name-Derivation: Monocytogenes = induces a monocytic response (in animals only).
Epidemiology / At Risk: Zoonotic. Ingestion of contaminated cole slaw, raw hot dogs, chicken, cheese, milk.
At Risk: PREGNANT women, young and old, immunocompromised.
Manifestations: Listeriosis. Bug has a tropism for the CNS.
Neonatal Disease:
Infected at early pregnancy: Abortion or very sick baby.
Infected at late pregnancy: Congential diseases. Sepsis, fetal distress, seizures. Delayed-onset meningitis and meningeoencephalitis.
Adult Disease: Bacteremia. Meningitis, endocarditis.
Pregnant Woman: Mild-flu like illness, usually associated with ice cream.
Sequelae: Strictly immunologic -- aseptic meningitis and rash.
Processing:
Specimen: CSF, blood, amniotic fluid.
Stain: Rods, both inside and outside cells, tends to filamentous.
Culture: Blood agar. Small colonies with narrow zone of beta-hemolysis.
Can grow in cold (4C), therefore it's perfectly happy when refrigerated.
Identification:
Catalase (+)
beta-Hemolysis
Facultative Intracellular Parasite of macrophages
Virulence:
Listerolysin O: Oxygen labile, beta-Hemolytic, like Streptolysin-O
Cytotoxic to RBC's, WBC's, PMN's (at low pH intracellularly), and myocardium
Disrupts phagolysosome.
Catalase
Facultative Intracellular Parasite of macrophages: actin polymerizes to allow the bugs to travel from cell to cell, like Shigella.
Cell Wall Lipid: Induces granulocytic response in humans. Induces an IgM response.
In humans, hemolytic due to cross-reaction with blood-group antigen. It's not gram-negative, but this leads to a hemolytic crisis.
Host Immune Response:
Monocytic response in animals. Granulocytic with left-shift (standard) response in humans.
Cross-reaction with Staph and Strep leads to high diagnostic titer of 1:200.
Protective Cell-mediated immunity is induced.
Only cause disease when in bloodstream
NEISSERIA MENINGIDITIS (MENINGEOCOCCUS): Gram-negative diplococcus
Name-Derivation:
Epidemiology / At Risk: Communicable bia inhaled droplets.
#2 cause of infantile meningitis.
Transient normal flora of throat.
Manifestations:
Meningeococcemia: Bugs in the bloodstream leads to a rash with lots of bugs in it.
Gram negative DIC and shock are possible complications.
Meningitis: Vomiting and fever may be the only signs in infants. No treatment leads to death.
Processing:
Specimen: CSF, rash exudate, blood, synovial fluid.
Stain:
Mostly extracellular gram-negative cocci. Because of their thick capsule they are not phagocytosed.
Lots of PMN's.
Culture: Smooth colonies. Capsule.
Thayer-Martin (chocolate agar with antibiotics)
Sterile specimens (CSF, blood) will can be grown on chocolate agar alone.
CO2
Subculture for glucose / maltose fermentation tests.
Identification:
Catalase(+), Oxidase(+): Neisseria
Glucose-fermenting, Maltose-fermenting (Meningidits)
Serotypes: Based on the capsule antigen.
A,B,C,D,29E: Originally known to be virulent
W135,X,Y,Z: Orginally thought to be harmless; now it's known otherwise.
Type-B is the most virulent because it is not immunogenic -- we cannot make protective antibodies against it.
It is made out of alpha-2,8-n-acetylneuraminic acid. It is rapidly degraded and thus not immunogenic.
Quellung Reaction: Add antiserum to look for Type-B. Swelling shows positive test.
CIE, Latex Agglutination: On CSF or urine. Two specific antibody tests to look for capsular antigens.
Virulence:
Cell-Associated:
Capsule: Thick polysaccahride determining the serogroup. Antiphagocytic.
Type-B is not immunogenic.
Outer Membrane Proteins: Another basis for serotyping.
They are being used to search for a conjugate vaccine.
They have homology with the Outer Membrane Proteins (I thru III) of N.Gonorrhea.
LPS: Induces the Schwartzman Reaction. Causes the rash and can lead to necrosis.
Pili: Adhesins in upper respiratory tract.
Enzymes:
IgA Protease: Two types, cleaves bonds at hinge region of IgA1
Oxidase
Needs Iron: Iron is taken up by an energy-dependent (not siderophore) mechanism.
Host Immune Response: Serological
Antibody is essential to phagocytosis of this bug.
Problem: cross-reacting antigens (E.Coli, E.Fecaelis) stimulate IgA, which blocks IgM, hindering serum immunity. Not good.
Group-B can be phagocytosed but remains serum resistant.
Vaccine / Prevention: Given to military recruits. Contains A, C, Y, W135. Naturally it doesn't contain B because Type-B is not immunogenic!
Vaccine can only be given to people older than two.
Treatment: Prophylactic antibiotic treatment for kids younger than 6 years old, with documented contact with an index case.
BRUCELLOSIS: Small gram-negative rod (coccobacillus)
Species
B. Melitensis goat
B. Abortus cattle
B. Suis pig
B. Canis dog
Epidemiology / At Risk: Zoonotic. Cattle ranchers and people who handle cattle.
Manifestations: Undulating Fever, Bang's Disease
Infecting organisms go into bloodstream and then are taken up by fixed RES macrophages, where they reside happily.
Organisms are occassionally released from fixed macrophages and go back into the bloodstream. Fever waxes and wanes according to the presence of organisms in the bloodsteam.
Symptoms: Fever, chills, sweats, myalgia, weakness, recurring at 10-day intervals.
Chronic disease causes microabscesses, granulomas, and caseation in the spleen and liver.
This results from Type-IV cell mediated response to the bugs.
Processing:
Specimen: Blood, bone marrow
Stain: Not useful
Culture: Brucella Agar = Selective Agar containing Erythritol, which the bugs subsist on.
Erythritol is found in reproductive tract of cattle, hence these bugs cause abortion in cattle. Humans don't have erythritol so no abortion happens.
Identification:
Facultative Intracellular Parasite of macrophages
Catalase (+)
Oxidase (+)
Gas-liquid chromatography can be used to identify the species.0
Virulence:
Catalase
5'-GMP, Adenine: They inhibit the release of peroxidase by PMN's, thus hindering the halide pathway of killing.
Facultative Intracellular Parasite of macrophages
LPS: Responsible for fever.
Host Immune Response:
IgM persists throughout infection. IgG waxes and wanes with fever.
IgG blocks IgM's bactericidal action in the serum.
Acute:Convalescent titer of 1:160.
Vaccine / Prevention: Cattle are vaccinated in Kansas. Live attenuated B.Abortus.
LISTERIA MONOCYTOGENES: Gram (+) pleomorphic rods
Name-Derivation: Monocytogenes = induces a monocytic response (in animals only).
Epidemiology / At Risk: Zoonotic. Ingestion of contaminated cole slaw, raw hot dogs, chicken, cheese, milk.
At Risk: PREGNANT women, young and old, immunocompromised.
Manifestations: Listeriosis. Bug has a tropism for the CNS.
Neonatal Disease:
Infected at early pregnancy: Abortion or very sick baby.
Infected at late pregnancy: Congential diseases. Sepsis, fetal distress, seizures. Delayed-onset meningitis and meningeoencephalitis.
Adult Disease: Bacteremia. Meningitis, endocarditis.
Pregnant Woman: Mild-flu like illness, usually associated with ice cream.
Sequelae: Strictly immunologic -- aseptic meningitis and rash.
Processing:
Specimen: CSF, blood, amniotic fluid.
Stain: Rods, both inside and outside cells, tends to filamentous.
Culture: Blood agar. Small colonies with narrow zone of beta-hemolysis.
Can grow in cold (4C), therefore it's perfectly happy when refrigerated.
Identification:
Catalase (+)
beta-Hemolysis
Facultative Intracellular Parasite of macrophages
Virulence:
Listerolysin O: Oxygen labile, beta-Hemolytic, like Streptolysin-O
Cytotoxic to RBC's, WBC's, PMN's (at low pH intracellularly), and myocardium
Disrupts phagolysosome.
Catalase
Facultative Intracellular Parasite of macrophages: actin polymerizes to allow the bugs to travel from cell to cell, like Shigella.
Cell Wall Lipid: Induces granulocytic response in humans. Induces an IgM response.
In humans, hemolytic due to cross-reaction with blood-group antigen. It's not gram-negative, but this leads to a hemolytic crisis.
Host Immune Response:
Monocytic response in animals. Granulocytic with left-shift (standard) response in humans.
Cross-reaction with Staph and Strep leads to high diagnostic titer of 1:200.
Protective Cell-mediated immunity is induced.