Microbiology Recall: Gram-Negative Cocci: Neisseria, Moraxella, & Acinetobacter

Front 1

What is Neisseria?

Back 1

Facultative
Anaerobic
G-
Diplococcus

Front 2

Wht is the classic morphology of Neisseria on light microscopy?

Back 2

Kidney bean shaped diplococci

Front 3

Which environment provides optimal growth for neisseria?

Back 3

High CO2 concentration

Front 4

What are two important enzymes that Neisseria possess?

Back 4

1) Cytochrome C oxidase
2) Catalase

Front 5

Wht is the function of Neisseria's two important enzymes?

Back 5

1) Cytochrome C oxidase is an enzyme that is part of electron transport and nitrate metabolism that can acept electrons from other substrates.
2) Catalase is an enzyme that inactivates toxic oxygen species by converting hydrogen peroxide to water and oxygen.

Front 6

What selective media is used for culturing Neisseria?

Back 6

Thayer-Martin VCN

Front 7

What is the composition of Thayer-Martin VCN media?

Back 7

Chocolate agar with vancomycin, colistin, and nystatin.

Front 8

What makes Thayer-Martin VCN selective?

Back 8

1) Vancomycin kills the G+ organisms
2) Colistin kills all G- organisms except Neisseria
3) Nystatin kills fungi

Front 9

What are two Neisseria species that cause disease in humans?

Back 9

N. meningitidis
N. gonorrhoeae

Front 10

How are N. meningitidis and N. gonorrhoeae metabolically differentiated?

Back 10

N. meningitidis can metabolize maltose and glucose
N. gonorrhoeae can only metabolize glucose.

Front 11

How are N. meningitidis and N. gonorrhoeae structurally differentiated?

Back 11

N. meningitidis is encapsulated and will have a positive Quellung reaction
N. gonorrhoeae is unencapsulated and will have a negative Quellung reaction

Front 12

What is N. meningitidis?

Back 12

Encapsulated facultative, anaerobic, G- diplococcus capable of fermenting maltose and glucose

Front 13

What is another name for N. meningitidis?

Back 13

Meningococcus

Front 14

What are the virulence factors of meningococcus?

Back 14

1) Antiphagocytic polysacharide capsule
2) Lipooligosaccharide (LOS) endotoxin
3) Immunoglobulin (Ig) A1 protease
4) Pili-facilitating adherence
5) Transferrin-binding proteins A and B, i.e., proteins that extract iron from human transferrin

Front 15

What are two ways of classifying N. meningitidis?

Back 15

Serotype
Serogroup

Front 16

What is the basis for N. meningitidis serotype differentiation?

Back 16

Outer membrane proteins and LOSs

Front 17

How many serotypes exist for N. meningitidis?

Back 17

>20

Front 18

What is the basis for N. meningitidis serogroup differentiation?

Back 18

Polysaccharide capsule

Front 19

How many N. meningitidis serogroups exist?

Back 19

>13

Front 20

Which N. meningitidis serogroups are infectious?

Back 20

Serogroups A, B, C, W, and Y

Front 21

Which N. meningitidis serogroup is the predominant cause of meningococcal disease in the United States?

Back 21

Serogroup B

Front 22

Which virulence factor is responsible for the petechial rash of meningococcal infections?

Back 22

LOS

Front 23

What is the only natural host for N. meningitidis?

Back 23

Humans

Front 24

What is the mode of transmission for N. meningitidis?

Back 24

Inhalation of aerosolized respiratory droplets.

Front 25

What are two populations at increased risk for meningococcal infections?

Back 25

1) Infants (6months-2 years)
2) Individuals living in close quarters such as schoold, prisons, and military barracks

Front 26

Why do infants younger than 6 months of age have a smaller risk of meningococcal infection?

Back 26

Maternal antibodies (IgG) confer protection.

Front 27

What are three predisposing risk factors for meningococcal disease?

Back 27

1) Recent URI
2) Active or passive smoking
3) Deficiencies in the late complement components, e.g., deficiency of C5b-C9 membrane attack complex (MAC)

Front 28

How does N. meningitidis most commonly affect humans?

Back 28

Asymptomatic nasopharyngeal colonization.

Front 29

How does N. meningitidis adversely affect humans?

Back 29

1) Meningitis
2) Meningococcemia
3) Waterhouse-Friderichsen syndrome (fulminant meningococcemia)

Front 30

What is a classic sign of N. meningitidis infection?

Back 30

Petechial rash progressing to purpura.

Front 31

What is the most common form of meningococcal disease?

Back 31

Meningitis

Front 32

What is meningitis?

Back 32

Inflammation of the protective tissues covering the brain.

Front 33

What are five symptoms of meningitis?

Back 33

1) Nucal rigidity
2) Severe headache
3) Altered mental status
4) Photophobia
5) Nonspecific symptoms including fever, vomiting, irritability, and lethargy

Front 34

What is meningococcemia?

Back 34

The presence of N. meningitidis in the blood.

Front 35

What is teh classic skin finding seen with meningococcemia?

Back 35

Petechial rash

Front 36

What are the symptoms of meningococcemia?

Back 36

1) Spiking fevers
2) Chills
3) Arthralgias
4) Myalgias

Front 37

What is the drug of choice for treating meningococemia in the adult?

Back 37

Ceftriaoxne
Cefotaxime

Front 38

What is Waterhouse-Friderichsen syndrome?

Back 38

Bilateral hemorrhage of the adrenal glands leading to adrenal insufficiency causing hypotension, tachycardia, disseminated intravascular coagulation, coma, and death.

Front 39

What is used for N. meningitidis prophylaxis?

Back 39

Rifampin

Front 40

When is prophylaxis for N. mengitidis indicated?

Back 40

For individuals who are close-contacts of patients infected with N. meningitidis.

Front 41

Is there a vaccine available for N. meningitidis?

Back 41

YES

Front 42

Who should get vaccinated for N. meningitidis?

Back 42

College students living in dormitories, military recruits, and travelers visiting endemic areas.

Front 43

What serogroups does the N. meningitidis vaccine protect against?

Back 43

Serogroups A, C, W, and Y
Unfortunately serogroup B is not effectively covered by this vaccine because it has a capsule containing polysialic acid, which does not elicit an adequate immune response.

Front 44

What is N. gonorrhoeae?

Back 44

Unencapsulated, facultative, anaerobic G- diplococcus capable of fermenting glucose.

Front 45

How is N. gonorrhoeae spread?

Back 45

1) Sexually
2) During parturition with an infected mother.

Front 46

What are the virulence factors of gonococcus?

Back 46

1) Pili
2) IgA1 Protease
3) Outer membane proteins (OMPI and OMPII)

Front 47

What are three functions of pili?

Back 47

1) Adherence to host cells
2) Prevention of phagocytosis from macrophages and neutrophils
3) Highly variable antigens protecting against antibodies.

Front 48

What two mechanisms allow gonococcus to avoid the host's immune system?

Back 48

Gene conversion
Phase variation

Front 49

What is gene conversion?

Back 49

Process by which N. gonorrhoeae produces pilin molecules with different antigens by recombining pilin genes.

Front 50

What is phase variation?

Back 50

Reversible lack of pilin expression

Front 51

How does phase variation occur?

Back 51

When a pilin gene is moved.

Front 52

What is the clinical significance of gene conversion and phase variation?

Back 52

1) Inability to create an effective vaccine because of highly variable bacterial antigens.
2) Reinfection may occur after first infection because initial infection does not confer immunity to gonococci with different antigens.

Front 53

What are common symptoms of gonococcal infection in males?

Back 53

Dysuria and purulent discharge from urethra.

Front 54

What are complications of gonococcal disease in males?

Back 54

1) Epididymitis
2) Prostatitis
3) Urethral strictures
4) Gonococcal bacteremia
5) Septic arthritis

Front 55

What are common symptoms of gonococcal infection in females?

Back 55

Dysuria, purulent vaginal discharge, and pain with sexual intercourse (dyspareunia).
Gonorrhea is more frequently asymptomatic in women than in men.

Front 56

What are complications of gonococcal disease in females?

Back 56

1) PID
2) Septic arthritis
3) Endometriosis
4) Gonococcal bacteremia
5) Infertility
6) Increased rate of ectopic pregnancy.

Front 57

Who is most likely to contract gonococcal septic arthritis?

Back 57

Sexually active individuals

Front 58

Why is gonococcal bacteremia less frequent than meningococcal bacteremia?

Back 58

Unlike encapsulated meningococci, unencapsulated gonococci have a limited ability to multiply in the blood stream.

Front 59

What are complications of gonococcal bacteriemia?

Back 59

1) Pericarditis
2) Endocarditis
3) Meningitis

Front 60

What are less common sites of N. gonorrhoeae infection in sexually active individuals?

Back 60

Anorectal area and throat.

Front 61

How is N. gonorrhoeae diagnosed?

Back 61

Gram stain and culture of infected fluid or discharge.
Culture of infected fluid or discharge is the gold standard for diagnosis because Gram stain is often negative.

Front 62

What do you look for on Gram stain?

Back 62

G- diplococci within polymorphonuclear neutrophils (PMNs).

Front 63

What are two rapid tests for detection of gonorrhea?

Back 63

1) Enzyme-linked immunoabsorbent assay for detection of gonococcal antigens
2) DNA probe assay for detection of gonococcal ribosomal genes.

Front 64

What is teh drug of choice for the treatment of gonococcal infections?

Back 64

Ceftriaxone

Front 65

Why is doxycycline often added to the treatment regimen for gonorrhea?

Back 65

Patients with gonorrhea are also aften coinfected with Chlamydia trachomatis.

Front 66

What clinical manifestation occurs with N. gonorrhoeae infection during parturition?

Back 66

Ophthalmia neonatorum

Front 67

What organism besides N. gonorrhoeae causes ophthalmia neonatorum?

Back 67

C. trachomatis

Front 68

What type of damage results from Ophthalmia neonatorum?

Back 68

Damage to the cornea may cause blindness.

Front 69

How is Ophthalmia neonatorum prevented?

Back 69

Newborn prophylaxis with erythromycin eye drops.

Front 70

How is Ophthalmia neonatorum treated?

Back 70

Systemically with ceftriaxone.

Front 71

What is Moraxella?

Back 71

Nonmotile, aerobic, G- coccus usuallly found in pairs that resemble Neisseria.

Front 72

Is Moraxella oxidase positive or negative?

Back 72

Oxidase positive.

Front 73

Does Moraxella ferment glucose?

Back 73

NO
It does not ferment any carbohydrates.

Front 74

Which species of Moraxella is the most important human pathogen?

Back 74

M. catarrhalis

Front 75

What infection does M. catarrhalis cause?

Back 75

1) Otitis media
2) Sinusitis
3) Bronchitis
4) Pneumonia

Front 76

How is M. catarrhalis treated?

Back 76

Because most strains are resistant to penicillins, trimethoprim-sufamethoxazole is often used.

Front 77

Whch species of Moraxella is a common cause of blepharitis (infection of the eyelid)?

Back 77

M. nonliquefaciens

Front 78

What is another common cause of blepharitis?

Back 78

Staphylococcus aureus

Front 79

What is Acinetobacter?

Back 79

Encapsulated, nonmotile, obligately aerobic coccobacillus that resembles Neisseria.

Front 80

Is Acinetobacter oxidase positive or negative?

Back 80

Oxidase negative

Front 81

Does Acinetobacter ferment glucose?

Back 81

NO
It does not ferment any carbohydrates

Front 82

Where is Acinetobacter found?

Back 82

Widely distributed in soil and water, but also part of normal skin flora.

Front 83

Which species of Acinetobacter usually causes human infection?

Back 83

A. calcoaceticus

Front 84

What infections does A. calcoaceticus cause?

Back 84

1) Sepsis
2) Pneumonia
3) UTI

Front 85

Which two patient populations are at higher risk for infection?

Back 85

1) Immunocompromised patients
2) Hospitalized patients wiht indwelling catheters or who are using respiratory ventilation