Microbiology Lecture 3.3: Non-Enteric Gram-Negative Bacteria

What does the cell wall of Non-Enteric Gram-Negative Bacteria contain?

LPS

What does LPS do that's important clinically?

1. Activate innate immune cells

2. Trigger release of inflammatory cytokines

What shape is Neisseria species?

Diplococci

What is the key structural difference between N. meningitidis and N. gonorrhoeae?

N. meningitidis has a capsule

N. gonorrhoeae does not

What disease does N. gonorrhoeae cause?

Gonorrhea

What kind of disease is Gonorrhea?

Sexually Transmitted Infection (STI)

What does transmission of N. gonorrhoeae occur by?

Sexual Contact (Oral, Vaginal, Anal)

What are the virulence factors of N. gonorrhoeae?

1. Type IV pili

2. Por protein

3. Lipooligosaccharide (LOS)

4. Opa Proteins

5. IgA Protease

6. Beta-Lactamase

What does Type IV pili mediate?

Attachment to non-ciliated mucosal epithelium

What does Type IV pili undergo to allow evasion of host antibodies?

Antigenic Variation

Type IV pili are highly _______

Variable

What do Por proteins facilitate?

Invasion of epithelial cells

What do Por proteins inhibit to promote survival in the cell?

Phagosome-Lysosome Fusion

What is an important component of Lipooligosaccharide (LOS)?

Lipid A

What do Opa proteins mediate?

Tight binding to host cells

What are opaque colonies expressing?

Opa proteins

What do IgA proteases cleave?

IgA antibodies

What does beta-lactamase inactivate?

Penicillin (Antibiotic Resistance)

What is N. gonorrhoeae inside to pass through the epithelium to invade the cell?

Phagosomes

What does the release of LOS by N. gonorrhoeae cause?

1. Inflammation

2. Tissue Damage

50% of females infected by N. gonorrhoeae are _________

Asymptomatic

Do most men develop symptoms from N. gonorrhoeae infection early or late?

Early

What does infection by N. gonorrhoeae cause in infants?

Eye infection

What are the typical symptoms of N. gonorrhoeae infection?

1. Purulent Discharge

2. Painful Urination

3. Inflammation

4. Swelling

5. PID (In females)

What can PID lead to in females?

Infertility

What are other manifestations of N. gonorrhoeae?

1. Pharyngitis

2. Anorectal infection

What is caused when N. gonorrhoeae is spread through the bloodstream to skin or joints?

Disseminated Gonococcal Infection (DGI)

What is Disseminated Gonococcal Infection (DGI) characterized by?

1. Fever

2. Arthritis

3. Pustular rash

What is the serious infection of protective membranes (meninges) called?

Bacterial Meningitis

What causes Bacterial Meningitis?

Bacteria enter bloodstream and cross blood-brain barrier

What is the reservoir of Neisseria meningitidis?

Human Nasopharynx

Does a high or low amount of people infected by Neisseria meningitidis develop invasive infections?

Low

What allows transmission of Neisseria meningitidis?

1. Respiratory droplets

2. Aerosolized secretions

What are the virulence factors of Neisseria meningitidis?

1. Polysaccharide Capsule

2. Type IV Pili

3. LOS

What does the Polysaccharide Capsule protect bacteria from?

Phagocytosis

Which factor is a major virulence determinant?

Polysaccharide Capsule

Which virulence factor is a basis for serogroup classification?

Polysaccharide Capsule

What is Neisseria meningitidis internalized into?

Phagocytic Vesicles

Can Neisseria meningitidis survive intracellularly?

Yes

In what percentage of carriers can Neisseria meningitidis cross epithelial barrier, enter bloodstream, and reach meninges?

Less than 1%

What does Neisseria meningitidis cause in the meninges?

Inflammation

What are the diseases caused by Neisseria meningitidis?

1. Meningococcemia (Sepsis)

2. Meningitis

3. Bronchopneumonia

When does Meningococcemia occur?

When bacteria disseminates through bloodstream

What are the symptoms of Meningococcemia?

1. Thrombosis of small vessels

2. Hemorrhagic skin lesions

3. Multiorgan involvement

If untreated, what can Meningococcemia lead to?

Shock and death

What is the purulent inflammation of the meninges called?

Meningitis

What are the symptoms of Meningitis?

1. Headache

2. Neck stiffness

3. Photophobia

What is the mortality rate for untreated Meningitis?

100%

Bronchopneumonia occurs especially in those with ________

Underlying lung disease

What is used to prevent infection by Neisseria meningitidis?

Polyvalent polysaccharide-protein conjugate vaccine

E. corrodens is part of what?

Normal oral microbiota

What can E. corrodens become?

Opportunistic and cause of serious infections

What does E. corrodens colonize?

Human oropharynx and upper respiratory tract (Normal habitat)

Transmission of E. corrodens caused by?

Endogenously by own oral microbiota

What are the common sources of infection by E. corrodens?

1. "Fight-bite" wounds

2. Human bite wounds

3. Dental trauma

What can E. corrodens cause if it gains access to deeper tissues?

1. Local oral infections

2. Subacute endocarditis

3. Sinusitis, meningitis, brain abscesses

4. Pneumonia and lung abscesses

Patients with what are more likely to experience Subacute endocarditis?

Preexisting heart disease

What does E. corrodens do if grown on solid media?

Pit or corrode agar surface

Is Pseudomonas aeruginosa opportunistic?

Yes

In what patients does Pseudomonas aeruginosa thrive in?

Immunocompromised or hospitalized patients

What are the distinctive features of Pseudomonas aeruginosa?

1. Blue-green pigment

2. Grape-like odor

Is Pseudomonas aeruginosa ubiquitous?

Yes

What is Pseudomonas aeruginosa isolated from?

Hospital sites

What does Pseudomonas aeruginosa transiently colonize?

Respiratory and gastrointestinal tract

What are the risk factors of Pseudomonas aeruginosa?

1. Broad-spectrum antibiotic use

2. Respiratory therapy equipment

3. Indwelling devices

What are the virulence factors of Pseudomonas aeruginosa?

1. Adhesins

2. Type III Secretion System

What are the adhesins of Pseudomonas aeruginosa?

1. Type IV pili

2. Alginate capsule

3. Exotoxin A

4. Intrinsic Antibiotic Resistance

What does the Type III Secretion System do?

Inject toxins directly into host cells

What is the mucoid polysaccharide layer that protects against phagocytosis and antibiotics?

Alginate Capsule

In what disease are Alginate Capsules prominent in?

Chronic lung infections (Cystic fibrosis)

What does Exotoxin A do?

1. Inhibit protein synthesis

2. Cause cell death

What is the portal of entry for Pseudomonas aeruginosa?

1. Inhalation (Usually)

2. Wounds

3. Catheters

4. Contaminated Water

What are the steps of Pseudomonas aeruginosa infection?

1. Attachment

2. Toxin secretion

3. Invasion

4. Biofilm formation

What describes the infection caused by Pseudomonas aeruginosa?

1. Chronic

2. Resistant to treatment

What are the diseases cause by Pseudomonas aeruginosa infections?

1. Pulmonary Infections

2. Urinary Tract Infections (UTI)

3. Skin and Soft Tissue Infections

4. Ear Infection

5. Eye Infection

6. Bacteremia and Endocarditis

What are asymptomatic colonization and necrotizing bronchopneumonia examples of?

Pulmonary Infections

Patients with what are Pulmonary Infections common in?

1. Chronic Lung Disease

2. Ventilator Use

3. Cystic Fibrosis

What are Urinary Tract Infections (UTI) usually associated with?

Indwelling urinary catheters

What causes Skin and Soft Tissue Infections?

1. Burn wounds

2. Folliculitis

3. Nail infections

What infection can be caused in burn wounds?

Bacteremia

What usually causes Folliculitis?

Contaminated hot tubs and pools

What usually causes Nail infections?

Contaminated water in nail salons

What can cause ear infections?

1. Swimmer's Ear

2. Chronic otitis media

What can cause Eye Infections?

1. Corneal trauma

2. Contaminated contact lens solution

Is the mortality rate for Bacteremia and Endocarditis high or low?

High

What are Bacteremia and Endocarditis common in?

1. Immunocompromised patients

2. Indwelling medical devices

What are Haemophilus influenzae divided into?

Six capsular serotypes (a-f)

What is the division of Haemophilus influenzae into serotypes based on?

Antigens in polysaccharide capsules

What are Nonencapsulated strains of Haemophilus influenzae called?

Non-typeable

What is the most virulent form of Haemophilus influenzae?

Serotype b (Hib)

What reduced the incidence of Haemophilus influenzae infections?

Hib Vaccine

What are Haemophilus influenzae infections caused by in vaccinated populations?

Non-typeable (nonencapsulated) strains

What is the transmission of Haemophilus influenzae caused by?

Respiratory droplets

What are the virulence factors of Haemophilus influenzae?

1. Type IV Pili

2. Capsule

3. IgA Protease

What are bacterial capsules composed of?

Polyribitol phosphate (PRP)

What does the colonization of Haemophilus influenzae begin as?

Mild upper respiratory tract colonization

What can encapsuled strains of Haemophilus influenzae do?

Cross epithelial and endothelial barriers and enter bloodstream

When encapsuled strains of Haemophilus influenzae enter the bloodstream, what is the result?

1. High-grade bacteremia

2. Dissemination to distant sites

What do nonencapsulated strains of Haemophilus influenzae typically cause?

Localized mucosal infections

What do encapsulated strains of Haemophilus influenzae typically cause?

Systemic invasive disease