Gram-Negative Opportunistic Infections Flashcards
What is an opportunistic pathogen?
Pathogen only capable of causing disease in immunocompromised people
What are biofilms?
Dense microbial communities surrounded by an extracellular matrix; associated with most opportunistic infections
What is the most common opportunistic pathogen?
E. coli
What are the 4 types of clinical syndromes E. coli can cause?
- Gastrointestinal
- Urinary tract infections
- Bacteremia
- Meningitis
A bacteriurial infection is an infection in which at least ___ bacteria/ml are present in the urine.
100,000
what are the clinical features of Cystitis syndrome?
involves dysuria, increased urinary frequency and urgency, and suprapubic tenderness. Usually lower UTI
what are the clinical features of acute pylenophritis syndrome?
results from disseminated UTI; involves flank pain, tenderness, and fever; dysuria and increased frequency and urgency
What are the clinical syndromes caused by Uropathogenic E. coli (UPEC)?
Generally UTI
Can be cystitis or acute pylenophritis
describe the pathogenicity of Uropathogenic E. coli (UPEC). how does it cause disease in cells? in what types of cells?
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
describe the virulence factors of Uropathogenic E. coli (UPEC)
Adhesins, LPS, capsule, motility, exotoxins including hemolysin
All of the Uropathogenic adhesins are mannose-resistant except one. It is ______ and causes _____ syndrome (cyctitis/pyelonephrotis).
Type 1 pili; cystitis
What are the uropathogenic E. coli (UPEC) adhesins associated with pyelonephritis?
P pili and F adhesin
What is mannose-resistant adhesion?
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.
How is adherence of E. coli measured?
Hemagglutination
______ _______ is a critical trait of bacteremic E. coli and is correlated with production of _____ capsule.
Serum resistance; K1
What is the hallmark of gram-negative bacteremia?
systemic reaction to endotoxin or LPS
Which E. coli strain is associated with neonatal meningitis?
What is its major pathogenic determinant?
E. coli K1
The K1 polysialic acid capsule allows the organism to escape phagocytosis. Siderophores contribute to its ability to cause disease.
Which opportunistic pathogen generally occurs in the lung and is associated with CF and COPD?
Pseudomonas aeruginosa
what is Pyocyanin? what species of bacteria makes it?
A blue pigment secreted by P. aeruginosa that is also a virulence factor that generates ROS
What toxins does P. aeruginosa secrete that contribute to its pathogenicity?
Endotoxin Exotoxins Proteases (elastases) - lung connective tissue breakdown Phospholipases - surfactant breakdown
what are the physical properties of P. aeruginosa? (G+/-?, metabolic type?)
Gram-negative
obligate aerobe in laboratory
While P. aeruginosa is considered an obligate aerobe, it can use _____ as an electron acceptor or ferment _______.
Nitrate; arginine
Gram-negative opportunistic pathogens (7)
- Escherichia coli
- Pseudomonas aeruginosa
- Klebsiella pneumonia
- Enterobacter cloacae
- Serratia marcesens
- Proteus vulgaris/mirabilis
- Acinetobacter baumanii
what are the clinical features of Klebsiella pneumoniae clinical syndrome?
- primary pneumonia when underlying medical problems are present “red current jelly” sputum
- urinary tract and wound infections
- bacteremia and meningitis
- diarrhea
Word association: “red current jelly” sputum
Klebsiella pneumoniae
What is Klebsiella pneumoniae’s main virulence factor? why this factor?
the capsule due to reduced phagocytosis and reduced complement susceptibility
Capsule production can help identify K. pneumoniae based on _____ ______ _______.
mucoid colony morphology
What types of infections are associated with Enterobacter cloacae?
burns, wounds, respiratory and urinary infections
In what setting do Enterobacter cloacae infections occur?
In the hospital secondary to antibiotic therapy
How does Enterobacter cloacae differ from Klebsiella?
E. cloacae is motile and less heavily encapsulated
what are the virulence factors of Serratia marcesens?
MS-fimbrae, proteases, siderophores, swarming motility
In what settings are Serratia marcesens infections likely to be seen?
Often nocosomial secondary to broad spectrum antibiotic therapy or instrumentation such as tracheostomy, indwelling catheters, dialysis, respirators
What are the non-nocosomial or out-patient settings associated with Serratia marcesens?
heroin addicts; septic arthritis
Prodigiosins
produced by Serratia and give rise to a characteristic red color
Which gram-negative opportunistic pathogen is common in the environment?
Serratia marcesens
What are the 2 characteristics of Proteus vulgaris/mirabilis that contribute to pathogenicity?
- Flagella mediate swarming motility
2. Urease synthesis leads to salt crystalization and stone formation
What type of infection does Proteus vulgaris/mirabilis cause?
Urinary tract infection
What are the physical properties of Acinetobacter baumanii?
oxidase negative non-fermenter, short rod
In what setting do infections with Acinetobacter baumanii infections usually occur and what complicates their treatment?
Nocosomial, often associated with indwelling medical devices
Reservoirs in hospitals may exist and multi-drug resistant strains exist
what virulence factors does Acinetobacter baumanii produce?
capsular polysaccharides, protein adhesins, proteolytic and lipolytic enzymes, LPS
What types of infections does Provindencia cause?
Nocosomial infections of urinary tract, blood, respiratory tract, and wounds
Which gram-negative pathogen causes neonatal meningitis and brain abscesses?
Citrobacter diversus
Which gram-negative opportunistic pathogens ferment lactose? (The others don’t)
E. coli
K. pneumonia
E. cloacae
Most gram-negative opportunistic pathogens are faculative anaerobes. Which gram-negative opportunistic pathogen is a non-fermenter?
Acinetobacter baumanii
