ICL 2.17: Pseudomonas & Burkholderia

Question 1

What is the microbiology of pseudomonas aeruginosa?

Answer 1

Gram negative bacilli (rods) —> can be arranged in pairs

oxidase positive

Question 2

What does pseudomonas aeruginosa ferment?

Answer 2

Lactose/glucose non-fermenting

Does NOT ferment lactose or glucose

Question 3

Where is pseudomonas aeruginosa found in nature?

Answer 3

Sometimes present as a part of the normal flora of humans

It’s ubiquitous in nature; basically it’s found everywhere —> common in soil and water

Question 4

Is pseudomonas aeruginosa motile?

Answer 4

Yes

Single polar flagellum

Question 5

What conditions does pseudomonas aeruginosa need to grow?

Answer 5

Optimum temperature for growth is 37 C (body temperature) — but it can also grow up to 42 C

It also has very minimal nutritional requirements; it can even grow in distilled water

These two factors together make pseudomonas aeruginosa very hard to get rid of

Question 6

Which disease is pseudomonas aeruginosa strongly associated with?

Answer 6

Cystic fibrosis!!

Nearly every CF patient will eventually acquire pseudomonas!

Once acquired, chronic infection will almost always ensue…

Question 7

What is cystic fibrosis?

Answer 7

Autosomal recessive disease

Caused by mutation in CFTR channel which causes chloride ions to not be moved efficiently —> this leads to mucus building up outside of cells

Bacteria can then accumulate in the mucus and cause infections

This is especially important in airways

CXR looks like patchy infiltrates literally everywhere

Question 8

How does pseudomonas aeruginosa cause chronic infections in CF patients?

Answer 8

Over 50% of CF patients have chronic pseudomonas aeruginosa infections by adolescence

It often mutates to better survive CF in the lung by expressing mucoid

Mucoid helps it to stick around in the lungs, literally

Infection causes chronic inflammation —> chronic inflammation causes lung damage —> lung damage causes death

Question 9

What are the main virulence factors associated with pseudomonas aeruginosa?

Answer 9

1. Alginate

2. Adhesins

Question 10

What is the function of alginate in pseudomonas aeruginosa?

Answer 10

It’s a virulence factor that causes the mucoid phenotype!

It acts as an adhesin which lowers bacterial susceptibility to phagocytosis and antibiotic penetration

It promotes biofilm formation

Also called capsule, exopolysaccharide and glycocalix

Question 11

What’s the function of adhesins in pseudomonas aeruginosa?

Answer 11

They are virulence factors that include fimbriae/pili and flagella

They provide adherence in the respiratory tract! Duh

Adhesins are aided by elastase, a protease that digests fibronectin to expose receptor

Question 12

What are the toxins and secreted enzymes associated with pseudomonas aeruginosa?

Answer 12

1. Exotoxin A
2. Exoenzyme S
3. LPS
4. Pyoverdin
5. Pyocyanin
6. Alkaline protease
7. Phospholipase C

Question 13

What is the function of exotoxin A?

Answer 13

It’s a toxin of pseudomonas aeruginosa —> has necrotizing activity at infection site

It has identical function to the diphtheria toxin = ADP-ribosylates EF-2 which impairs translation

Even though it’s partially identical to DT, it’s antigenically distinct and uses a different receptor

Question 14

What’s the function of exoenzyme S? In what patient population is it commonly seen?

Answer 14

It’s a toxin of pseudomonas aeruginosa

Specially, it’s an ADP-ribosylating toxin that is thought to impair phagocytosis

It’s frequently seen in infected burn victims

Question 15

Does pseudomonas aeruginosa have LPS?

Answer 15

Yes because it’s gram (-) bacteria

It’s a toxin for pseudomonas aeruginosa

Question 16

What is pyoverdin?

Answer 16

It’s a toxin of pseudomonas aeruginosa

It has a yellow pigment!!**

It binds host iron = siderophore

It also regulates secretion of other virulence factors

Question 17

What is pyocyanin?

Answer 17

Toxin of pseudomonas aeruginosa

It’s blue in pigment**

It catalyze the production of superoxide and H2O2

It also stimulates release of IL-8 which attracts neutrophils

Question 18

What’s the function of alkaline protease?

Answer 18

It’s a toxin of pseudomonas aeruginosa

It causes tissue destruction and interferes with host immune response

Question 19

What is phospholipase C?

Answer 19

It’s a toxin of pseudomonas aeruginosa

It’s a hemolysis = lyses RBCs

It also facilitates tissue destruction

Question 20

Does pseudomonas aeruginosa have antibiotic resistance?

Answer 20

Yes! It’s intrinsically resistant to antibiotics

Question 21

Why is pseudomonas aeruginosa intrinsically resistant to a lot of antibiotics?

Answer 21

1. Low permeability of its cell wall
2. The genetic capacity to express a wide variety of resistance mechanisms
3. It can become resistant through mutation in chromosomal genes which regulate resistance genes
4. It can acquire additional resistance genes from other bacteria via plasmids, transposing and bacteriophages
5. It can form biofilms

Question 22

What are biofilms? Which bacteria are they associated with?

Answer 22

pseudomonas aeruginosa

Biofilms are communities of surface-associated microorganisms embedded in a matrix of extracellular polymeric substance (EPS) — think about the plaque on your teeth

Biofilms protect bacteria from the environment —> the concentration of antibiotics needed to kill bacteria in biofilms is several hundred times the amount needed to kill free-swimming bacteria

Question 23

Biofilms are commonly associated with what?

Answer 23

Device-related infections like catheters, prosthesis, cardiac valves, etc.

You usually have to replace the indwelling device to get rid of the biofilm

Question 24

what kind of pathogen is psuedomonas aeruginosa?

Answer 24

it’s an opportunistic pathogen

in healthy individuals infections are rare

Question 25

what are the requirements for psuedomonas aeruginosa to cause an infection?

Answer 25

it's an opportunistic pathogen; in healthy individuals infections are rare colonization requires: 1. skin breakage/abrasions 2. artificial inoculation (catheters, respirators) 3. some type of immunodeficiency/immunosuppression or underlying condition

Question 26

what tissues does psuedomonas aeruginosa infect?

Answer 26

it can infect almost any tissue because of its many virulence factors and high antibiotic resistance

Question 27

what are the clinical diseases associated with psuedomonas aeruginosa?

Answer 27

1. pulmonary infections 2. skin and soft tissue infections 3. eye infections 4. ear infections 5. UTI 6. endocarditis 7. bacteremia

Question 28

how does psuedomonas aeruginosa cause pulmonary infections?

Answer 28

ranges in severity from asymptomatic colonization to sever necrotizing bronchopneumonia typically seen in patients with cystic fibrosis, chronic lung diseases, congestive heart failure or neutropenia immunocompromised patients are at higher risk, especially when previously treated with broad-spectrum antibiotics or when a mechanical ventilator is used mortality rate is 70%

Question 29

what types of skin and soft tissue infections does psudomonas aeruginosa cause ?

Answer 29

1. burn infections very common in patients with severe burns; incredibly difficult to treat 2. folliculitis typically from immersion in contaminated water (hot tubs) 3. nail infections 4. osteochondritis = inflammation of bone and cartilage

Question 30

which patients get UTIs from psudomonas aeruginosa?

Answer 30

primarily in patients with indwelling catheters it's actually one of the leading causes of hospital-acquired UTIs

Question 31

which populations are more likely to get psudomonas aeruginosa bacteremia?

Answer 31

people with with neutropenia, diabetes, extensive burns, hematologic malignancies, AIDS-related immunodeficiency aka someone with an underlying immunodeficiency

Question 32

how do you diagnose psudomonas aeruginosa ?

Answer 32

1. pigmentation P. aeruginosa produces two main types of soluble pigments: pyoverdin (yellow) and pyoctanin (blue) 2. odor = grape-like odor 3. culture

Question 33

what would a psudomonas aeruginosa culture show?

Answer 33

gram (-) bacilli B-hemolytic oxidase positive

Question 34

how do you treat psudomonas aeruginosa infection?

Answer 34

really difficult to treat due to intrinsic resistance and compromised host defenses of most patients also it's ubiquitous, so impossible to eradicate from the hospital environment so a combination of antibiotics is generally used = B-lactam + aminoglycoside choice of antibiotic depends on site of infection, severity, and local resistance patterns

Question 35

how do you prevent psudomonas aeruginosa infection?

Answer 35

1. maintain sterility of equipment especially ventilators, catheters 2. avoid inappropriate administration of broad-spectrum antibiotics because they eliminates normal microbiota)

Question 36

FLASHCARD: pseudomonas summary?

Answer 36

gram-negative rod, lactose non-fermenting, oxidase positive, motile found ubiquitously in the environment primarily an opportunistic pathogen of immunocompromised hosts --> major pathogen of the cystic fibrosis lung produces a wide variety of virulence factors, including toxins, adhesins, and alginate can be fairly easily identified due to the pigments it produces and its fruity, grapelike odor is intrinsically resistant to many antibiotics and forms biofilms causes a wide range of human disease—can infect almost any tissue given the opportunity

Question 37

what is the pathogen? the parents of Z., a 2-year old girl with a chronic cough, became alarmed because her cough worsened over a week’s time and her color “became poor” with coughing her parents are unable to remember when she was last cough-free and state that she sometimes spit out yellow-green mucus after forceful coughing, most often when waking up in the morning on examination, Z. was an alert but pasty and pale-looking child with increased respiratory effort and rapid breathing --> on inspiration, crackles were heard throughout the lung fields her extremities showed moderate clubbing with mild cyanosis CXR showed increased (abnormal) interstitial and peribronchial markings throat culture was performed, a specimen of the green mucus was obtained and sent for Gram stain and culture --> sputum Gram stain showed many Gram-negative bacilli based on the history, physical examination, and x-ray, a tentative diagnosis of cystic fibrosis was made

Answer 37

Pseudomonas aeruginosa

Question 38

which pathogen is responsible? 58-year-old male was admitted to a hospital in southern India after suffering from high-grade fevers with intermittent cough and expectoration for the previous three months his history included well-managed diabetes for the past 20 years, and no travel for the last 6 months he had consulted 4 different hospitals previously and received several broad-spectrum antibiotics due to a diagnosis of P. aeruginosa infection at the last hospital visited in spite of compliance with the antibiotic treatment, he remained febrile and his condition progressively worsened CT of the thorax showed bilateral pleural effusions and left chest wall abscess samples of pus, blood, urine, sputum, and pleural fluid were collected and cultured --> cultures of the pus, blood, and pleural fluid yielded pure growth of non-lactose fermenting colonies on MacConkey agar and non-hemolytic colonies on blood agar microscopy showed gram-negative rods

Answer 38

burkholderia pseudomallei

Question 39

what is MacConkey agar?

Answer 39

made of lactose

Question 40

why is burkholderia pseudomallei often misdiagnosed?

Answer 40

it's super similar to pseudomonas aeruginosa so a delay in the identification of B. pseudomallei or a misidentification as another species (most commonly, Pseudomonas species or as a contaminant in culture) is not uncommon in laboratories that are unfamiliar with this organism the problem is a delay in diagnosis can be fatal, since empirical antibiotic regimens used for suspected bacterial sepsis often do not provide adequate coverage for B. pseudomallei

Question 41

what is the microbiology of burkholderia?

Answer 41

gram (-) bacilli (rod) oxidase positive very large genomes

Question 42

is burkholderia anaerobic or aerobic?

Answer 42

obligate aerobes

Question 43

what do burkholderia ferment?

Answer 43

lactose non-fermenting does NOT ferment lactose

Question 44

are burkholderia motile?

Answer 44

all species are motile except B. mallei which lacks flagella

Question 45

what is commonly used to identify burkholderia?

Answer 45

they're resistant to polymyxin B

Question 46

which bukrholderia species are relevant to human health?

Answer 46

1. B. cepacia complex 2. B. mallei 3. B. pseudomallei

Question 47

what disease does B. cepacia complex cause?

Answer 47

causes the same range of diseases as P. aeruginosa ex. respiratory disease, skin infections, endocarditis, etc. similar to P. aeruginosa, are ubiquitous, can colonize moist surfaces and are opportunistic pathogens

Question 48

what disease does B. mallei cause?

Answer 48

glanders it's an infection that usually occurs in equids via nasal secretion humans can acquire it via aerosols high mortality rate even with antibiotics because it's really resistant it has varying clinical symptoms and is really rare so it's hard to diagnose

Question 49

what disease does b. pseudomallei cause?

Answer 49

melioidosis symptoms include: 1. cough 2. chest pain during breathing 3. high fever 4. headache and general muscle soreness. 5. weight loss but there's varying clinical symptoms so it's difficult to diagnose

Question 50

where is B. cepaciae complex found in nature?

Answer 50

ubiquitous can colonize moist surfaces and are opportunistic pathogens it was originally identified as a plant pathogen that caused soft rot in onions

Question 51

how difficult are B. cepacia to kill?

Answer 51

incredibly tough to kill can survive betadine!! (the brown stuff they clean people with before surgery)

Question 52

which diseases can B. cepacia complex cause?

Answer 52

commonly found in: 1. CF patients 2. chronic granulomatous disease 3. UTIs (catheters) 4. some patients who acquire B. cepacia infection develop the so-called “cepacia syndrome,” a rapidly fatal pneumonia and sepsis, with a high mortality

Question 53

which bacterial infection is a contraindication for lung transplantation?

Answer 53

B. cepacia complex

Question 54

which virulence factors are associated with B. cepacia complex?

Answer 54

1. LPS (even more toxic than that of pseudomonas) 2. lipase 3. proteases 4. flagella 5. biofilms

Question 55

which species is the only non-motile bukholderia species?

Answer 55

burkholderia mallei

Question 56

what species does burkholderia mallei normally infect?

Answer 56

normally found in equids = horses, zebra, etc. but it can also infect humans during World War I, Germany initiated a clandestine program to infect horses and cattle owned by Allied armies with glanders German agents infiltrated the United States and infected animals prior to their shipment across the Atlantic in support of Allied forces

Question 57

why is burkholderia mallei a tier 1 select agent?

Answer 57

it would be a great bioweapon because: 1. highly infectious through aerosol 2. LD50 = less than 500 organisms 3. no available vaccine

Question 58

how are burkholderia pseudomallei infections usually acquired?

Answer 58

infection usually occurs via skin abrasion it's motile so it's capable of polymerizing actin to spread from cell to cell

Question 59

in what environment is burkholderia pseudomallei commonly found?

Answer 59

moist, tropical soils like rice patties specifically south east asia **Thailand

Question 60

why is burkholderia pseudomallei classified as a tier 1 select agent?

Answer 60

1. easily aerosolized 2. LD50 < 10 organisms in the aerosol form (even less than B. mallei) 3. high mortality rate despite antimicrobial treatment 4. no vaccine

Question 61

what is meliodosis?

Answer 61

caused by burkholderia pseudomallei wide range of clinical manifestations; severity varies melioidosis is able to affect any organ except heart valves patients with meliodosis usually have risk factors for disease like diabetes, thalassemia, alcohol use or renal disease frequently has a history of occupational or recreational exposure to mud of pooled surface water

Question 62

what are the predisposing conditions for melioidosis?

Answer 62

1. diabetes 2. renal disease 2. injury/drowning

Question 63

how is B. pseudomallei transmitted?

Answer 63

1. percutaneous inoculation 2. inhalation 3. ingestion

Question 64

what are the similarities between burkholderia pseudomallei and B. mallei?

Answer 64

both are encapsulated and can live intracellularly in most cell types no real transmission person-to-person

Question 65

how are burkholderia pseudomallei and B. mallei related?

Answer 65

B. mallei is a “subclone” of B. pseudomallei so B. mallei lacks ~20% of B. pseudomallei genes but has most virulence factors in common so hopefully a vaccine against one will protect against both

Question 66

how do you treat burkholderia pseudomallei infections?

Answer 66

all cases of melioidosis, even mild disease, should be treated with initial intensive therapy (at least two weeks of intravenous therapy) followed by eradication therapy orally for a minimum of three months B. pseudomallei are characteristically resistant to penicillin, ampicillin, first- and second-generation cephalosporins, gentamicin, tobramycin, and streptomycin

Question 67

FLASHCARD: Burkholderia

Answer 67

gram-negative, lactose non-fermenting, oxidase positive, obligate aerobes 3 species relevant to human health = B. cepacia complex (BCC), B. mallei, B. pseudomallei BCC is a group of species not easily differentiated from each other, which cause a similar range of diseases as P. aeruginosa --> CF, CGD, UTIs, cepacia syndrome B. mallei causes glanders, normally a disease of equids that can also infect humans --> hard to diagnose, high fatality rate; only non-motile burkholderia B. pseudomallei causes meliodosis --> low infectious odse, high mortality, not easily identified; infection usually occurs via skin abrasion those with diabetes and other underlying conditions are at higher risk; common in south/southeast Asia

Question 68

what can you use to identify burkholderia?

Answer 68

resistant to polymyxin B

Question 69

which burkholderia species are tier 1 select agents?

Answer 69

1. B. mallei | 2. B. pseudomallei