Gram-negative Cocci

What’s a distinctive biochemical feature between N. gonorrheae and N. meningitidis and Moraxella

N, meningitidis can ferment maltose
N. gonorrheae and Moraxella cannot ferment maltose

What are the reservoirs for N. gonorrheae?

Only humans

What are the documented modes of transmission for N. gonorrheae?

• Sexual (any kind)

• Vertical (Mother to neonate ocular infection)

Non-sexual transmission not documented

What are the virulence factors of N. gonorrheae?

• IgA proteases

• Lipooligosaccharides LOS (Strong endotoxin)

• Antigenic variation of pili (shuffle pili genes → Escape IS

What does N. gonorrhoeae cause in men?

If untreated, epididymitis and prostatitis

What does N. gonorrhoeae cause in women?

If untreated: Urethral stricture, salpingitis, tubo-ovarian abscess, PID, Fit-HughCurtis syndrome, Sterility

What does N. gonorrhoeae cause in neonates?

Ophthalmia neonatorum (conjunctivitis) 2-5 days after birth

What if N. gonorrhoeae remains untreated for too long

Bacteremia and septic arthritis

How is N. gonorrhoeae diagnosed in males

We take a urine sample from patients who have not urinated in at least 2 hours, also intraurethral swabs (discharge at the meatus), and intrarectal swab

N gonorrhoeae diagnosis in women

Swabs from: cervix, vagina, urethra, rectal, endometrium, Skene/ Bartholin glands

Common methods of diagnosis in men & women

Oropharyngeal swabs (oral sex)
Blood
Fluid from arthritic joints

Nucleic acid amplification test

What morphological characteristics

IC kidney-beaned shaped Gram-negative diplococci inside Polymorphonuclear cells (Neutrophils and stuff)

N. gonorrhoeae culture medium

Modified Thayer-Martin agar

• They are capnophiles and require 5-10% CO2.

• They’re also very delicate and autolytic and must be cultured right after specimen acquisition

N. gonorrhoeae Biochemical characteristics

• Glc +

• Proline arylamidase +

• Maltose -

• Levulose -

• Saccharose - (They are saccharolytic)

• Gamma gt -

N. gonorrhoeae treatment (Venereal and neonatal)

Venereal: Single dose IM ceftriaxone, and if chlamydia isn’t yet ruled out, must also add doxycycline

Neonatal: Erythromycin eye ointment → Prevent neonatal blindness

N. gonorrhoeae treatment

Pretty common, β-lactamases

N. gonorrhoeae prevention

• Safe sex

• Treatment of partner

N. gonorrhoeae vaccine

None, antigenic variation

What are the hosts for N. meningitidis

Only in humans, it normally colonizes the oropharyngeal and nasopharyngeal tracts. Carrier rate is 8-20%

N. meningitidis transmission mode

Respiratory droplets

What are the symptoms of N. meningitidis bacteremia

When N. meningitidis enters the bloodstream, it releases LOS endotoxins in large amounts and causes the following:

• Waterhouse-Friderichsen syndrome - acute hemorrhagic adrenal insufficiency

• Petechiae

• Purpura

• Adrenal hemorrhage

• DIC

• Shock

*Note: While bacteremia may lead to meningitis, patients can easily die from the symptoms before ever getting meningitis (19-70% mortality at this stage)

Explanations

Petechiae and purpura result from endotoxin-induced endothelial injury and DIC, while adrenal hemorrhage causes acute adrenal insufficiency.

DIC leads to microthrombi everywhere + bleeding everywhere → Adrenal glands normally have very high blood flow, and this blocks it → Bilateral adrenal hemorrhage → Hemorrhagic adrenal insufficiency

What are the epidemiological characteristics of meningococcal meningitis?

• 2nd most common meningitis (King is S. pneumoniae - pneumococcus)

• Sporadic in young children

Outbreaks: Occur among adults in crowded living conditions (dorms/army)

How would you describe meningococcal meningitis in children and adults?

What’s its mortality rate?

Rapidly progressive 7-13%

Describe Meningitides’ capsule as a virulence factor

• Antiphagocytic

• Resistance to complement-mediated lysis

• Contributes to antigenic variation (13 serogroups)

Progression to meningitis chart

N. meningitidis invasive serotypes

A, B, C, Y and W135

A, B, C cause 90% of meningococcal diseases

Compare the 6 types of meningitis depending on:
- CSF appearance, pressure, WBC/uL, Protein mg/dL, Glucose mg/dL, Chloride

What’s the best way to diagnose Meningococci

• Gram stain on CSF → Find IC and EC encapsulated diplococci with flat adjacent sides

• PCR on serum and CSF

• Immunofluorescent test kits for CDF available commercially for: NHS

Extra:

Although meningococcal meningitis requires bacteremia, blood tests alone are insufficient because bacteremia may be transient, while CSF directly samples the infected compartment, provides higher diagnostic yield, and distinguishes bacterial meningitis from other causes.

How do we culture meningococci

Modified Thayer-Martin agar
→ Obligate aerobe
→ Capnophile → 5-10% CO2

A patient presents subacute illness, focal neurological deficits, seizures, or a contiguous ENT source, and a history of COM, sinusitis, dental infection, or recent surgery what do you do?

These symptoms fit the clinical presentation of brain abscesses, which is caused by anaerobes.
HOWEVER, we must still rule out meningococci, because missing meningococci is catastrophic, and time-critical, so:
→ The CNS specimen must be split between the aerobic, capnophilic, modified Thayer-Martin, and Robertson’s cooked medium: allows us to cultivate Bacteroide and anaerobic cocci

What are the biochemical characteristics of N. meningitidis

• Maltose +

• Glc +

• Gamma GT+

• ONPG -

Neisseria meningitidis treatment and prophylaxis and vaccination

Treatment:

• Ceftriaxone

• Penicillin G

Prophylaxis:

• Rifampicin + Ciprofloxacin/ Ceftriaxone

Vaccination:

• Polyvalent vaccine for ACYW135

• New vaccine for B group (high-risk individuals)

Where can we find Moraxella catarrhalis?

1-5% of adults carry it in their URT

Children and older adults may have HIGHER frequencies

What clinical conditions can Moraxella catarrhalis cause

Otitis media, sinusitis, bronchitis, pneumonia

How do we culture M. Catarrhalis

Specimen: Sputum / sinus biopsy / Middle ear pus

Morphology: Coccobacilli

Culture: Incubation conditions similar to gonococci, BUT grows on NA and does not require increased CO2

M. catarrhalis Biochemistry

• Ox +

• Cat +

• DNase +

• Tributyrin +

What helps us differentiate between M. catarrhalis and Neisseria

Moraxella catarrhalis does not ferment any sugars: Glc - / Lac - / Mal - / Suc -