L.8 GNB: Pseudomonas Flashcards
(113 cards)
1
Q
What are Non-Fermenting Gram-Negative Bacilli (NFGNB)?
A
Gram-negative bacilli that are aerobic organisms and non-lactose fermenting on MacConkey agar
Often associated with nosocomial infections and frequently exhibit intrinsic and acquired antimicrobial resistance
2
Q
What is a general characteristic of Non-Fermenting Gram-Negative Bacilli?
A
They are often associated with nosocomial infections
This refers to infections acquired in a hospital setting
3
Q
What does a positive oxidase reaction indicate?
A
Pseudomonas spp.
Positive oxidase test indicates the presence of certain bacteria that can utilize oxygen
4
Q
What does a negative oxidase reaction indicate?
A
Acinetobacter spp.
Negative oxidase test indicates the absence of cytochrome c oxidase
5
Q
Where are Pseudomonas spp. commonly found?
A
They are frequently found in:
* Soil
* Water
* Sewage
* Hospital environments
* Hot tubs and showers
* Surfaces of plants and animals
These bacteria are ubiquitous in the environment
6
Q
What roles do Pseudomonas spp. play in the environment?
A
They play roles in:
* Plant pathogenesis
* Food spoilage
* Environmental bioremediation
Environmental bioremediation includes processes like hydrocarbon degradation
7
Q
Fill in the blank: Non-Fermenting Gram-Negative Bacilli are _______.
A
aerobic organisms
8
Q
True or False: Non-Fermenting Gram-Negative Bacilli can be involved in food spoilage.
A
True
9
Q
What are the modes of transmission for Pseudomonas aeruginosa?
A
Modes of Transmission include:
* Direct contact with contaminated water (e.g. bathing, ingestion)
* Inhalation of contaminated aerosols
* Contaminated medical equipment, especially if rinsed with unsterile water
* Indirect contact via the hands of healthcare workers after touching contaminated surfaces
Additional modes of transmission may exist but are not detailed here.
10
Q
What percentage of bacterial isolates in clinical microbiology labs does Pseudomonas aeruginosa account for?
A
Approximately 15%
This statistic highlights its prevalence in clinical settings.
11
Q
Why is Pseudomonas aeruginosa classified as an ESKAPE pathogen?
A
Due to its multidrug resistance
ESKAPE pathogens are known for their ability to evade the effects of antibiotics.
12
Q
What proportion of healthcare-associated infections (HAIs) is caused by Pseudomonas aeruginosa according to 2017 data?
A
~4%
This data reflects its significant role in HAIs.
13
Q
What are common infection sites for Pseudomonas aeruginosa?
A
Common Infection Sites include:
* Respiratory tract (especially in ventilated patients)
* Urinary tract
* Burn wounds
* Surgical sites
* Bloodstream infections (e.g. catheter-related)
* Ear infections (e.g. swimmer’s ear)
* Corneal ulcers (especially with contact lens use)
These sites reflect the opportunistic nature of the pathogen.
14
Q
What are risk factors for immunocompromised hosts?
A
Disrupted physical barriers and weakened immune systems
Disrupted physical barriers include burn injuries, intravenous lines, urinary or dialysis catheters, and endotracheal tubes. Weakened immune systems include neonates, cystic fibrosis patients, HIV/AIDS, neutropenia, complement deficiencies, and hypogammaglobulinemia.
15
Q
List examples of disrupted physical barriers in immunocompromised patients.
A
- Burn injuries
- Intravenous lines
- Urinary or dialysis catheters
- Endotracheal tubes
16
Q
List examples of weakened immune systems in immunocompromised patients.
A
- Neonates
- Cystic fibrosis patients
- HIV/AIDS
- Neutropenia
- Complement deficiencies
- Hypogammaglobulinemia
17
Q
What are the key facts about Acinetobacter spp.?
A
Oxidase-negative, non-fermenting Gram-negative bacilli found in soil, water, and hospital environments
Acinetobacter baumannii is the most clinically relevant species.
18
Q
What clinical infections are caused by Acinetobacter spp.?
A
- Ventilator-associated pneumonia (VAP)
- Wound and burn infections
- Bloodstream infections
- Urinary tract infections
19
Q
True or False: Acinetobacter spp. are known for their ability to survive on dry surfaces.
A
True
20
Q
Acinetobacter spp. are notorious for developing _______.
A
multi-drug resistance
21
Q
What is the most clinically relevant species of Acinetobacter?
A
Acinetobacter baumannii
22
Q
What type of infections does P. aeruginosa frequently cause?
A
Localized infections, especially in individuals with compromised barriers or underlying conditions
P. aeruginosa is known for its opportunistic infections in vulnerable populations.
23
Q
What is the primary respiratory infection associated with P. aeruginosa?
A
Pneumonia, particularly ventilator-associated pneumonia (VAP)
VAP is a significant risk for patients on mechanical ventilation.
24
Q
In cystic fibrosis patients, what type of infection is commonly caused by P. aeruginosa?
A
Chronic pulmonary infections, often leading to progressive lung damage due to biofilm formation
Biofilms protect bacteria from the immune system and antibiotics.
25
What is otitis externa commonly known as?
Swimmer’s ear
## Footnote
This condition is often associated with water exposure.
26
What type of ear infection is particularly seen in children or immunocompromised individuals?
Otitis media
## Footnote
Otitis media is an infection of the middle ear.
27
What eye infection is often associated with contact lens use?
Bacterial keratitis
## Footnote
Trauma to the eye surface can increase the risk of this infection.
28
What is osteomyelitis and how does it typically occur?
An infection of the bone, typically following trauma or surgery, including puncture wounds through footwear
## Footnote
Osteomyelitis can lead to serious complications if untreated.
29
What gastrointestinal issues can P. aeruginosa cause?
Diarrhoea, enteritis, or enterocolitis, especially in immunocompromised or hospitalized patients
## Footnote
These conditions can lead to significant morbidity in vulnerable populations.
30
What are catheter-associated urinary tract infections (CAUTIs) particularly associated with?
Long-term catheterized patients
## Footnote
CAUTIs are a common complication in hospitalized patients.
31
In what type of patients do systemic infections from P. aeruginosa tend to occur?
Critically ill or immunocompromised patients
## Footnote
Systemic infections are serious and require immediate medical attention.
32
What is the trend in invasive P. aeruginosa bloodstream infections from 2015 to 2018?
Increased by 54%
## Footnote
This increase indicates a rising concern for public health.
33
What has been the fluctuation range of multidrug resistance (MDR) among invasive P. aeruginosa isolates since 2014?
4–9%
## Footnote
MDR poses a significant challenge in treating infections.
34
What types of secondary infections can arise from primary respiratory or wound infections?
Secondary pneumonia, osteomyelitis, and septic arthritis
## Footnote
These infections can complicate initial conditions and require different treatment approaches.
35
What is endocarditis typically associated with?
IV drug use or prosthetic valves
36
What are Central Nervous System (CNS) infections characterized by?
Rare but severe
37
What often leads to CNS infections?
Neurosurgical procedures or contiguous spread from adjacent infections
38
What types of infections are included in Skin and Soft Tissue Infections?
* Wound infections
* Burn wound colonization
* Necrotizing fasciitis
* Ecthyma gangrenosum
39
What is the first phase of P. aeruginosa Infection?
Colonisation Phase
40
What occurs during the Colonisation Phase of P. aeruginosa Infection?
Following a break in the first-line defense, mediated by cell-associated virulence factors
41
What are some examples of cell-associated virulence factors in P. aeruginosa?
* Pili
* Capsule
42
What is the second phase of P. aeruginosa Infection?
Chronic Infection Phase
43
Why is the Chronic Infection Phase especially relevant?
In cystic fibrosis
44
What occurs during the Chronic Infection Phase of P. aeruginosa Infection?
* Formation of biofilms
* Chronic inflammation
* Progressive tissue destruction
45
What is the third phase of P. aeruginosa Infection?
Acute Infection Phase
46
What drives the Acute Infection Phase of P. aeruginosa Infection?
Aggressive virulence factors
47
What are the consequences of the Acute Infection Phase in P. aeruginosa Infection?
* Invasion
* Tissue necrosis
* Systemic toxicity
48
What are the cell-associated factors of P. aeruginosa that promote adherence and colonization?
Capsule, Type IV pili, Lipopolysaccharide (LPS)
## Footnote
Capsule is especially alginate in mucoid strains.
49
What role does Lipopolysaccharide (LPS) play in P. aeruginosa virulence?
Triggers host inflammatory response, shows structural variability, changes during transition from non-mucoid to mucoid phenotype
## Footnote
Important for immune evasion.
50
What are the secreted (extracellular) factors of P. aeruginosa that cause invasion, tissue destruction, and immune evasion?
Proteases, Elastases, Phospholipase C, Exotoxin A, Endotoxin (LPS)
## Footnote
Exotoxin A inhibits protein synthesis via ADP-ribosylation.
51
What is the function of Exotoxin A in P. aeruginosa?
Inhibits protein synthesis via ADP-ribosylation, contributes to local tissue necrosis and systemic toxicity.
52
What does Endotoxin (LPS) trigger in the host?
Sepsis and inflammatory cytokine release.
53
What is pyocyanin?
A blue-green pigment with cytotoxic effects that interferes with antioxidant systems in host cells
## Footnote
Example: glutathione.
54
What are the effects of pyocyanin on host cells?
Promotes oxidative stress and damages respiratory epithelium.
55
What is alginate slime and its role in P. aeruginosa infections?
A polysaccharide matrix forming part of biofilms that inhibits ciliary clearance and protects bacteria from:
* Phagocytosis
* Antibiotics
* Host immune response.
56
What is the function of leukocidin secreted by P. aeruginosa?
Destroys white blood cells (leukocytes), weakening the immune defense.
## Footnote
Leukocidin contributes to the virulence of P. aeruginosa by impairing the host's immune response.
57
What does elastase degrade and how does it affect lung tissue?
Degrades elastin, contributing to lung tissue destruction. Cleaves immune components: IgG, IgA, and complement proteins. Breaks down surfactant proteins A and D, impairing lung function.
## Footnote
Elastase plays a significant role in the pathogenesis of lung infections caused by P. aeruginosa.
58
What is the role of alkaline protease in P. aeruginosa infections?
Lyses fibrin, disrupting clot formation and tissue structure.
## Footnote
Alkaline protease contributes to tissue damage and aids in the spread of infection.
59
What is the effect of phospholipase C in P. aeruginosa?
Hydrolyzes cell membranes, contributing to host cell lysis.
## Footnote
This enzyme enhances the pathogenicity of P. aeruginosa by damaging host cell integrity.
60
How does Exotoxin A affect host cells?
Inactivates elongation factor 2 (EF-2) through ADP-ribosylation, halting protein synthesis, causing cell death.
## Footnote
Exotoxin A is a major virulence factor that significantly impacts cell function.
61
What regulates the expression of Exotoxin A?
Environmental iron levels.
## Footnote
The availability of iron influences the virulence of P. aeruginosa by regulating toxin production.
62
What is the function of Exotoxin S?
Disrupts the function of phagocytic immune cells, impairing the host’s ability to clear the infection.
## Footnote
This toxin is critical for P. aeruginosa's evasion of the immune system.
63
What is the Type III Secretion System (T3SS) in P. aeruginosa?
Injects effector proteins directly into host cells, enabling immune evasion and tissue damage.
## Footnote
T3SS is a key mechanism by which P. aeruginosa exerts its virulence.
64
What is the role of ExoS in P. aeruginosa infections?
Promotes intracellular survival and disrupts cytoskeletal function; particularly relevant in cystic fibrosis (CF).
## Footnote
ExoS is vital for the persistence of P. aeruginosa in chronic infections.
65
What does ExoT disrupt in host cells?
Host cell signaling and migration.
## Footnote
ExoT contributes to the pathogenicity of P. aeruginosa by interfering with normal cellular functions.
66
What is the characteristic of ExoU?
Highly cytotoxic; causes rapid lysis of host cells; more prevalent in ICU and burn unit isolates.
## Footnote
ExoU is associated with severe infections and indicates a high level of virulence.
67
What effect does ExoY have on host cells?
Increases intracellular cAMP, disrupting cellular functions.
## Footnote
The increase in cAMP alters signaling pathways within host cells, contributing to the pathogenicity of P. aeruginosa.
68
True or False: ExoS and ExoU are usually co-expressed by the same strain of P. aeruginosa.
False.
## Footnote
ExoS and ExoU are typically mutually exclusive, indicating different pathogenic strategies.
69
What is a biofilm?
A structured community of bacteria enclosed in a self-produced matrix.
## Footnote
Biofilms are significant in chronic infections due to their protective properties.
70
What is the matrix of a biofilm rich in?
Alginate, an exopolysaccharide.
## Footnote
Alginate contributes to the structural integrity and protective function of biofilms.
71
What are the two growth modes of bacteria in biofilms?
Planktonic (free-floating) and sessile (surface-attached).
## Footnote
The transition to sessile growth enhances bacterial survival.
72
What is one way biofilms protect P. aeruginosa?
They shield P. aeruginosa from:
* Phagocytes
* Antibodies
* Disinfectants
* Antibiotics
## Footnote
This protection contributes to the persistence of infections.
73
Where are biofilms commonly found in healthcare settings?
On medical devices and hospital infrastructure.
* Medical devices: Catheters, prosthetic joints, heart valves, shunts.
* Hospital infrastructure: Water systems, air-conditioning units.
## Footnote
Biofilms serve as persistent reservoirs of infection.
74
What are the challenges in treating P. aeruginosa infections?
Intrinsic and acquired antibiotic resistance.
* Resistance may emerge during treatment.
* Biofilms contribute to therapeutic failure.
## Footnote
These challenges complicate the management of infections.
75
What is recommended for the therapy of P. aeruginosa infections?
Avoid monotherapy due to rapid resistance development. Use dual therapy:
* A β-lactam (e.g., ceftazidime, piperacillin-tazobactam)
* Plus an aminoglycoside (e.g., tobramycin) or fluoroquinolone (e.g., ciprofloxacin).
## Footnote
Carbapenems (e.g., meropenem) are often reserved for MDR strains.
76
Fill in the blank: Biofilms contribute to _______ failure.
therapeutic
## Footnote
This underscores the difficulty in treating infections associated with biofilms.
77
True or False: Biofilms can develop resistance during treatment.
True
## Footnote
This characteristic makes treating infections more complicated.
78
What are the mechanisms of antimicrobial resistance?
* Outer membrane impermeability (inherent to Gram-negatives)
* Biofilm formation – impairs antibiotic penetration
* Efflux pumps – actively expel antibiotics
* Resistance plasmids – acquired genes encoding resistance enzymes
* Enzyme production – β-lactamases that degrade antibiotics
* Resistance to disinfectants – complicates infection control in hospitals
## Footnote
Each mechanism contributes to the ability of bacteria to survive exposure to antibiotics and other antimicrobial agents.
79
What is the Burkholderia cepacia Complex (BCC)?
A group of environmental Gram-negative bacilli
## Footnote
BCC is often non-pathogenic in healthy individuals but can be highly pathogenic in certain populations.
80
Is Burkholderia cepacia pathogenic in healthy individuals?
No
## Footnote
BCC is typically non-pathogenic in healthy individuals.
81
In which patients is Burkholderia cepacia highly pathogenic?
Patients with cystic fibrosis (CF)
## Footnote
In these patients, BCC can cause chronic respiratory infections.
82
What clinical condition can Burkholderia cepacia cause in patients?
Necrotizing pneumonia known as 'cepacia syndrome'
## Footnote
This syndrome is associated with rapid respiratory decline and poor transplant outcomes.
83
What does it mean if Burkholderia cepacia is often intrinsically multi-drug resistant (MDR)?
It means that BCC can resist multiple antibiotics without prior exposure
## Footnote
This intrinsic resistance complicates treatment options.
84
What are the implications of Burkholderia cepacia for patients with cystic fibrosis?
* Accelerated lung function decline
* Frequent hospitalizations
* Increased need for IV antibiotics
* Reduced life expectancy
## Footnote
These factors significantly impact the health and quality of life of CF patients.
85
What infection control measures are recommended for managing Burkholderia cepacia in patients with CF?
* Segregation in both inpatient and outpatient settings
* Social isolation to prevent cross-infection in CF communities
## Footnote
These measures are crucial to manage the risk of infections among CF patients.
86
True or False: Burkholderia cepacia is considered a relative contraindication to lung transplantation in some cases.
True
## Footnote
The presence of BCC may complicate the decision to proceed with lung transplantation.
87
What is Acinetobacter baumannii?
An opportunistic pathogen ubiquitous in the natural environment (soil, water, skin)
## Footnote
Major cause of nosocomial infections, especially in ICUs.
88
What are common clinical associations of Acinetobacter baumannii?
* Ventilator-associated pneumonia (VAP)
* Catheter-associated infections
* Bloodstream infections (BSI)
* Wound infections (e.g., post-surgical or combat-related)
## Footnote
Known for causing outbreaks across hospitals.
89
What does CRAB stand for?
Carbapenem-Resistant Acinetobacter baumannii
## Footnote
This strain is of particular concern due to its resistance.
90
Name some resistance mechanisms of Acinetobacter baumannii.
* Efflux pumps
* Enzymatic degradation (carbapenemases)
* Biofilm formation
* Altered outer membrane proteins
## Footnote
These mechanisms contribute to its multi-drug resistance.
91
What is Stenotrophomonas maltophilia?
A previously classified member of the Pseudomonas group, found in soil, water, and plants
## Footnote
Not highly virulent but concerning in immunocompromised patients.
92
What are typical infections caused by Stenotrophomonas maltophilia?
* Pneumonia (especially VAP)
* Bloodstream infections
## Footnote
Increasingly reported in cystic fibrosis patients.
93
What antibiotic is often required for treating Stenotrophomonas maltophilia?
Trimethoprim-sulfamethoxazole (co-trimoxazole)
## Footnote
Inherently multidrug-resistant (MDR).
94
Name some resistance mechanisms of Stenotrophomonas maltophilia.
* β-lactamase production
* Efflux pumps
* Low outer membrane permeability
## Footnote
These mechanisms contribute to its multidrug resistance.
95
True or False: Acinetobacter baumannii is known for its ability to survive on dry surfaces.
True
## Footnote
This characteristic aids its outbreak potential in hospitals.
96
Fill in the blank: Stenotrophomonas maltophilia is increasingly reported in patients with _______.
Cystic Fibrosis
## Footnote
Often co-infects with P. aeruginosa.
97
What is the primary specimen type for identifying Pseudomonas aeruginosa?
Multiple specimen sources should be considered:
* Urine
* Sputum
* Blood
* Pus / wound swabs
## Footnote
Specimen sources are critical for accurate identification of the organism.
98
What type of agar is used as general media for culturing Pseudomonas aeruginosa?
Blood agar and Chocolate agar
## Footnote
These media support the growth of a wide range of bacteria, including P. aeruginosa.
99
Which agar is considered moderately selective for Pseudomonas aeruginosa?
MacConkey agar (non-lactose fermenter)
## Footnote
This agar differentiates between lactose fermenters and non-fermenters.
100
What is the highly selective culture medium for Pseudomonas aeruginosa?
Cetrimide agar (selects for P. aeruginosa)
## Footnote
Cetrimide agar is specifically designed to isolate P. aeruginosa from mixed cultures.
101
What are the incubation conditions for culturing Pseudomonas aeruginosa?
Temperature: 37°C for 24–48 hours; Atmosphere: Aerobic
## Footnote
These conditions are optimal for the growth of P. aeruginosa.
102
What are the key identification features of Pseudomonas aeruginosa?
Gram-negative bacilli, Oxidase positive, Weak catalase positive, Grows at 42°C but not at 4°C, Produces distinctive colonies (e.g., green pigment, fruity smell)
## Footnote
These characteristics aid in the laboratory identification of the organism.
103
What does the API 20 NE test include for identifying Pseudomonas aeruginosa?
8 conventional biochemical tests and 12 assimilation tests (based on minimal media turbidity)
## Footnote
This system is specifically designed for non-Enterobacterales Gram-negative bacilli.
104
True or False: The Vitek system is always effective in identifying mucoid strains of Pseudomonas aeruginosa.
False
## Footnote
The Vitek system may struggle to correctly identify mucoid strains of P. aeruginosa.
105
Fill in the blank: Pseudomonas aeruginosa is a type of _______.
Gram-negative bacilli
## Footnote
This classification is important for understanding its characteristics and treatment.
106
What is the Burkholderia cepacia Complex (BCC)?
A group of bacteria that are Gram-negative bacilli and non-lactose fermenters
## Footnote
BCC includes several species that can be pathogenic, particularly in immunocompromised individuals.
107
What are the basic lab features of Burkholderia cepacia?
GNB, oxidase positive, non-lactose fermenter, aerobic
## Footnote
GNB stands for Gram-negative bacilli.
108
How can Burkholderia cepacia be selectively isolated from respiratory specimens?
Using Burkholderia cepacia selective agar
## Footnote
This agar inhibits P. aeruginosa and enhances the isolation of BCC.
109
What is required for the definitive identification of B. cepacia?
Molecular methods due to biochemical overlap with other non-fermenters
## Footnote
Biochemical tests alone may not accurately differentiate B. cepacia from other species.
110
What are the key features of Stenotrophomonas and Acinetobacter spp.?
Gram-negative bacilli, oxidase negative, non-lactose fermenters, strictly aerobic
## Footnote
These features are essential for the identification and differentiation of these species.
111
What culture media may support the growth of Stenotrophomonas and Acinetobacter spp.?
Cetrimide agar and Burkholderia cepacia agar
## Footnote
Burkholderia cepacia agar may assist in differential growth.
112
True or False: Automated AST is reliable for non-fermenters.
False
## Footnote
Automated methods like Vitek are not reliable for non-fermenters such as Pseudomonas aeruginosa and Acinetobacter baumannii.
113
What manual methods are recommended for Antimicrobial Susceptibility Testing (AST)?
Disk diffusion, E-tests, broth microdilution for confirmation
## Footnote
These methods provide more accurate results for non-fermenters compared to automated systems.
