Chapter 21 Pseudomonas

Question 1

What are the phenotypic traits of pseudomonas

Answer 1

Non-spore forming
Aerobic 
They are straight gram negative bacilli 
OXIDASE POSITIVE
Capable of serving at 4 degrees Celsius they are mesophilic
Oxidize glucose

Question 2

Describe the normal habitat of Pseudomonas species and the route of transmission

Answer 2

Natural habitat: They are normally found in water, soil and plants. In domestic environments they are found in swimming pools, hot tubes and in contact lens solutions and hospital settings they are found in showers and medical devices

Route of transmission: Ingestion of contaminated food or water, exposure to contaminated medical devices , they can also enter by penetrating wounds

Question 3

Describe the normal habitat of Burkholderia cepacia and their route of transmission

Answer 3

Habitat: They are normally found in soil, water and plants, they can survive in hospital settings and they colonize respiratory tract of cystic fibrosis patients
Route of transmission: Exposure to medical devices and solutions contaminated from the environment. Person to person transmission

Question 4

Identify the factors that contribute to the pathogenicity of Pseudomonas aeruginosa and explain the mechanism for each

Answer 4

Factors that contribute to the organisms pathogenicity include:

• Exotoxin A: Kills the host by inhibiting protein synthesis
• Exoenzyme S and T: Production of various proteolytic enzymes and hemolysins that are capable of destroying the cells and tissues
• Pilli and adhesins: They reinforce attachment to the host cell
• Pyocyanin: they contribute to the green pigment in P.aeruginosa they damage the cells by producing reactive oxygen species

Question 5

What is quorum sensing ? and also explain the complications in quorum sensing

Answer 5

It is a mechanism that will detect bacterial products in the environment they are capable of forming biofilm
Formation of biofilms is associated with serious infections and they form microcolonies in the tissue

Question 6

List the various disease states associated with P. aeruginosa

Answer 6

They are opportunistic pathogens and patients with exposed skin tissue(Natural first line of defense) are more susceptible eg patients with burns and cystic fibrosis
They are divided into 2 broad categories:
-Community acquired Infections(CAI): Swimmers ear (otitis external), eye infections, Osteomyelitis, endocarditis in intravenous drug users and cause respiratory tract infections in cystic fibrosis patients
-Hospital Acquired infections(HAI): Respiratory tract infections, they used Luki tube for patients that cant produce sputum, Urinary tract infections, Central nervous system and bacteremia

Question 7

List the various disease states associated with Burkholderia

Answer 7

They cause lung infections and bacteremia in patients with cystic fibrosis and chromic granulomatous infection
Nosocomial infections include septicemia, urinary tract infections, and respiratory tract infections

Question 8

List the appropriate identification scheme for identifying P. aeruginosa.

Answer 8

Blood agar: Spreading, flat colonies with metallic sheen/mucoid colonies in CF patients
MacConkey agar: Non lactose fermenters Mucoid colonies mistaken for klebsiella
Beta hemolytic
Oxidase positive
Grapelike odor
Catalase positive( protects it against destruction of bacteria)
Oxidizes glucose and xylose
Nutrient agar: Display a distinct blue-green (pyocyanin) pigment production

Question 9

Describe the media and chemical principle of each media used, including differential and selective agars that aid in the cultivation of Pseudomonas, Brevundimonas,

Answer 9

5% sheep blood agar an chocolate agars: Beta hemolysis on blood agar
MacConkey agar: All organisms grow and are lactose fermenters, Mucoid colonies
Cetrimide agar: Routine media that is used for the isolation of Pseudomonas aeruginosa
Muller-Hilton agar: Green pigment due to pyocyanin

Question 10

Describe the potential therapies for B. cepacia and B. pseudomallei and the concerns regarding optimal therapy.

Answer 10

Many isolates of pseudomonas can be very resistant to antimicrobial testing
Burkholderia cepacia: Piperacillin,Ceftazidime, Ciprofloxacin
Burkholderia pseudomallei: Ceftazidime , Piperacillin-tazobactam

Question 11

Describe and identify the patterns of antibiotic resistance in P. aeruginosa.

Answer 11

P.aeruginosa is intrinsically resistant to antimicrobial agents and they acquire resistance to active agents