Gram-Negative Opportunistic Infections

Question 1

What is an opportunistic pathogen?

Answer 1

Pathogen only capable of causing disease in immunocompromised people

Question 2

What are biofilms?

Answer 2

Dense microbial communities surrounded by an extracellular matrix; associated with most opportunistic infections

Question 3

What is the most common opportunistic pathogen?

Answer 3

E. coli

Question 4

What are the 4 types of clinical syndromes E. coli can cause?

Answer 4

1. Gastrointestinal
2. Urinary tract infections
3. Bacteremia
4. Meningitis

Question 5

A bacteriurial infection is an infection in which at least ___ bacteria/ml are present in the urine.

Answer 5

100,000

Question 6

what are the clinical features of Cystitis syndrome?

Answer 6

involves dysuria, increased urinary frequency and urgency, and suprapubic tenderness. Usually lower UTI

Question 7

what are the clinical features of acute pylenophritis syndrome?

Answer 7

results from disseminated UTI; involves flank pain, tenderness, and fever; dysuria and increased frequency and urgency

Question 8

What are the clinical syndromes caused by Uropathogenic E. coli (UPEC)?

Answer 8

Generally UTI

Can be cystitis or acute pylenophritis

Question 9

describe the pathogenicity of Uropathogenic E. coli (UPEC). how does it cause disease in cells? in what types of cells?

Answer 9

Almost always ascending
involves various adhesins
not all strains are equivalent
forms “pods” or biofilm-like structures within epithelial cells of urinary tract, can replicate within cells

Question 10

describe the virulence factors of Uropathogenic E. coli (UPEC)

Answer 10

Adhesins, LPS, capsule, motility, exotoxins including hemolysin

Question 11

All of the Uropathogenic adhesins are mannose-resistant except one. It is ______ and causes _____ syndrome (cyctitis/pyelonephrotis).

Answer 11

Type 1 pili; cystitis

Question 12

What are the uropathogenic E. coli (UPEC) adhesins associated with pyelonephritis?

Answer 12

P pili and F adhesin

Question 13

What is mannose-resistant adhesion?

Answer 13

Many UTI bacteria are capable of binding mannosides of uroepithelial cells. If binding is not blocked by mannose the pilus is referred to as mannose-resistant.

Question 14

How is adherence of E. coli measured?

Answer 14

Hemagglutination

Question 15

______ _______ is a critical trait of bacteremic E. coli and is correlated with production of _____ capsule.

Answer 15

Serum resistance; K1

Question 16

What is the hallmark of gram-negative bacteremia?

Answer 16

systemic reaction to endotoxin or LPS

Question 17

Which E. coli strain is associated with neonatal meningitis?

What is its major pathogenic determinant?

Answer 17

E. coli K1
The K1 polysialic acid capsule allows the organism to escape phagocytosis. Siderophores contribute to its ability to cause disease.

Question 18

Which opportunistic pathogen generally occurs in the lung and is associated with CF and COPD?

Answer 18

Pseudomonas aeruginosa

Question 19

what is Pyocyanin? what species of bacteria makes it?

Answer 19

A blue pigment secreted by P. aeruginosa that is also a virulence factor that generates ROS

Question 20

What toxins does P. aeruginosa secrete that contribute to its pathogenicity?

Answer 20

Endotoxin
Exotoxins
Proteases (elastases) - lung connective tissue breakdown
Phospholipases - surfactant breakdown

Question 21

what are the physical properties of P. aeruginosa? (G+/-?, metabolic type?)

Answer 21

Gram-negative

obligate aerobe in laboratory

Question 22

While P. aeruginosa is considered an obligate aerobe, it can use _____ as an electron acceptor or ferment _______.

Answer 22

Nitrate; arginine

Question 23

Gram-negative opportunistic pathogens (7)

Answer 23

1. Escherichia coli
2. Pseudomonas aeruginosa
3. Klebsiella pneumonia
4. Enterobacter cloacae
5. Serratia marcesens
6. Proteus vulgaris/mirabilis
7. Acinetobacter baumanii

Question 24

what are the clinical features of Klebsiella pneumoniae clinical syndrome?

Answer 24

• primary pneumonia when underlying medical problems are present “red current jelly” sputum
• urinary tract and wound infections
• bacteremia and meningitis
• diarrhea

Question 25

Word association: "red current jelly" sputum

Answer 25

Klebsiella pneumoniae

Question 26

What is Klebsiella pneumoniae's main virulence factor? why this factor?

Answer 26

the capsule due to reduced phagocytosis and reduced complement susceptibility

Question 27

Capsule production can help identify K. pneumoniae based on _____ ______ _______.

Answer 27

mucoid colony morphology

Question 28

What types of infections are associated with Enterobacter cloacae?

Answer 28

burns, wounds, respiratory and urinary infections

Question 29

In what setting do Enterobacter cloacae infections occur?

Answer 29

In the hospital secondary to antibiotic therapy

Question 30

How does Enterobacter cloacae differ from Klebsiella?

Answer 30

E. cloacae is motile and less heavily encapsulated

Question 31

what are the virulence factors of Serratia marcesens?

Answer 31

MS-fimbrae, proteases, siderophores, swarming motility

Question 32

In what settings are Serratia marcesens infections likely to be seen?

Answer 32

Often nocosomial secondary to broad spectrum antibiotic therapy or instrumentation such as tracheostomy, indwelling catheters, dialysis, respirators

Question 33

What are the non-nocosomial or out-patient settings associated with Serratia marcesens?

Answer 33

heroin addicts; septic arthritis

Question 34

Prodigiosins

Answer 34

produced by Serratia and give rise to a characteristic red color

Question 35

Which gram-negative opportunistic pathogen is common in the environment?

Answer 35

Serratia marcesens

Question 36

What are the 2 characteristics of Proteus vulgaris/mirabilis that contribute to pathogenicity?

Answer 36

1. Flagella mediate swarming motility | 2. Urease synthesis leads to salt crystalization and stone formation

Question 37

What type of infection does Proteus vulgaris/mirabilis cause?

Answer 37

Urinary tract infection

Question 38

What are the physical properties of Acinetobacter baumanii?

Answer 38

oxidase negative non-fermenter, short rod

Question 39

In what setting do infections with Acinetobacter baumanii infections usually occur and what complicates their treatment?

Answer 39

Nocosomial, often associated with indwelling medical devices | Reservoirs in hospitals may exist and multi-drug resistant strains exist

Question 40

what virulence factors does Acinetobacter baumanii produce?

Answer 40

capsular polysaccharides, protein adhesins, proteolytic and lipolytic enzymes, LPS

Question 41

What types of infections does Provindencia cause?

Answer 41

Nocosomial infections of urinary tract, blood, respiratory tract, and wounds

Question 42

Which gram-negative pathogen causes neonatal meningitis and brain abscesses?

Answer 42

Citrobacter diversus

Question 43

Which gram-negative opportunistic pathogens ferment lactose? (The others don't)

Answer 43

E. coli K. pneumonia E. cloacae

Question 44

Most gram-negative opportunistic pathogens are faculative anaerobes. Which gram-negative opportunistic pathogen is a non-fermenter?

Answer 44

Acinetobacter baumanii