Microbiology - Chapter 20 - Gram negative

Gram-negative bacteria

type of bacteria that stain red with Gram stain and have a thin cell wall with an outer membrane

Gram negative Aerobic Bacilli (rods)

1) Bordetella (B. pertussis)
2) Legionella (L. pneumophila)
3) Pseudomonads (P. aeruginosa)

B. pertussis causes

whooping cough

treatment for B. pertussis

primarily supportive care

prevention for B. pertussis

immunization (Dtap or Tdap)

Legionella

gram negative
Aerobic
bacilli

Bordetella

gram negative
Aerobic
bacilli

L. pneumophila

-causes most disease in humans
-causes Legionaires' disease
-results in pneumonia
- can be fatal

treatment for Legionella

-respiratory fluoroquinolones
- azithromycin

Prevention of Legionella

Water below 20C and above 60C
Prevent water stagnation
Very difficult

Pseudomonads

Aerobic
Bacilli
common in soil
many are serious plant pathogens
problematic in hospitals (why they don't like plants in hospitals anymore)
opportunistic pathogens

treatment of psuedomonads

treatment difficult due to drug resistance

disease caused from Pseudomonads

Pseudomonad aeruginosa

Neisseria

gram negative
diplococci

2 diseases caused by Neisseria pathogenic to humans

1) N. gonorrhea
2) N. meningitisis

N. gonorrhea

gram negative
dilplococci
Aerobic
causes gonorrhea

treatment of N. gonorrhea

antibiotics

pathology of N. gonorrhea

- gonococci can evade immune system
- can survive within neutrophils

Nisseria gonorrhea virulence factors

- In men, pus-filled discharge, painful urination
- In women, often asymptomatic, can trigger pelvic inflammatory disease (PID)
- Infections can occur in gential tract, pharyngitis, gingivitis

Nisseria meningitidis

gram negative
Aerobic
diplococci
causes meningitis

Enterobacteriaceae

- gram negative
- facultative anaerobe
- Normal microbial intestinal flora of most animals and humans
- Ubiquitous in water, soil and decaying vegetation
- Enteric bacteria are the most common gram negative pathogens of humans

2 most important families of gram-negative, facultative anaerobic bacilli

1) Enterobacteriaceae
2) Pasteurellaceae

Pathogenic Enterobacteriaceae divided into 3 groups

1) Coliform (rods, ferment lactose)
2) Noncoliforms (do not ferment lactose)
3) True pathogens (make anyone sick)

4 Coliform Enterobacteriaceae

1) Escherichia coli (E. coli)
2) Klebsiella (K. pneumoniae)
3) Serratia
4) Proteus

E. coli

- gram negative
- facultative anaerobic
- Coliform (ferments lactose, rod)
- common cause healthcare associated UTI (catheter)

E. coli O157:H7

gram negative
Toxin-producing strain of E. coli
First seen in 1982; causes bloody diarrhea
Leading cause of diarrhea worldwide
undercooked meat

Klebsiella

gram negative
facultative anaerobic
opportunistic
in digestive & respiratory tracts of humans & animals
causes K. pneumonia

Klebsiella pneumoniae

What encapsulated gram-negative, lactose-fermenting rod is associated with pneumonia in patients with alcoholism, diabetes, and chronic lung disease?

Serratia

- gram negative bacilli
- coliform (lactose fermenting)
- produces red pigment at room temp
- can grow on catheters, in saline solution and other hospital supplies
- can cause life-threatening infection to immunocompromised patient
- resistant to antimicrobial drugs

Proteus

- gram negative
- facultative anaerobe
- Coliform (lactose fermenting)
- UTI with long-term catheter use
- resistant to antimicrobial drugs

3 Enterobacteriaceae True pathogens

1) Salmonella
2) Shigella
3) Yersinia

Salmonella

- gram negative
- non lactose fermenting
- facultative anaerobic
- lives in intestines of birds, reptiles, and mammals
- most human infection due to consuming food with animal feces
- can cause salmonellosis and typhoid fever

Can cause Typhoid fever

Salmonella

True pathogenic Enterobacteriaceae Pathology

- inhibit phagocytosis
- rearrange cytoskeleton of eukaryotic cells
- induce apoptosis

Salmonella symptoms

diarrhea, fever, and abdominal cramps
causes gastroenteritis, bacteremia, peritonitis

treatment of salmonella

fluid and electrolyte replacement
Typhoid fever - antimicrobial drugs
gallbladder removal
vaccines for travelers

Shigella

What nonmotile gram-negative, non-lactose-fermenting facultative anaerobic rod uses the human colon as its only reservoir and is transmitted by fecal-oral spread?

4 well defines species of Shigella

1) S. dysenteriae
2) S. flexneri
3) S. boydii
4) S. sonnei

pathogenicity of Shigella

secretes Shiga toxin
stops protein synthesis
produces more severe disease

treatment for Shigellosis

fluid and electrolyte replacement

Yersinia

- gram negative
- facultative anaerobic
- non lactose fermenting
- true pathogenic Enterobacteriaceae

3 species of Yersinia

Y. enterocolitica (causes inflammation of intestinal tract)
Y. pseudotuberculosis (less severe inflammation of the intestine)
Y. pestis (causative agent of the bubonic and pneumonic plague)

Treatment of Yersinia pestis

many antibacterial drugs are effective

Pasteurellaceae

-Most are small, nonmotile, facultative anaerobes
-Require heme or cytochromes for growth
- gram negative