Opportunistic Infections Flashcards
When does a bacterium not need to be as virulent to cause infection?
When host resistance is reduced
What are the frequently encountered opportunistic pathogens?
E. coli
Staph. aureus
Klebsiella pneumoniae
Enterococcus spp.
Pseudomonas aeruginosa
Enterobacter spp.
Serratia spp.
Proteus spp.
Clostridium difficile
What kind of epidemic can many of the opportunistic pathogens cause?
Nosocomial epidemics
Which of the opportunistic pathogens can’t cause nosocomial epidemics?
E. coli
Proteus spp.
Clostridium difficile
What do opportunistic infections in a patient often indicate?
That there is something else wrong with the patient because the host must be altered in some way for pathogens to take hold.
Which local defects in a patient can lead to opportunistic infections?
Anatomical defects
Surgical and other wounds
Burns
Catheterisation
Foreign bodies in general
Why does a foreign body in the patient often lead to opportunistic infections?
Because the pathogen can find refuge in the foreign body
What type of anatomical defects can lead to opportunistic infections?
Short urethra in women can lead to UTIs
How can surgery lead to an opportunistic infection?
Breaking of the skin means it is more likely to become infected.
Which systemic defects in a patient can lead to opportunistic infections?
Extremes of age
Leukopaenia
Malignancy
Malnutrition
Diabetes
Liver disease
Immunocompromising infections
Antimicrobial treatment
Immunodeficiencies
What is candadiasis one of the first indications of?
Diabetes
Which infections can lead to an increased likelihood of opportunistic infections?
HIV
Measles
What are the different types of opportunistic infection?
Wound infection
UTI
Intra-abdominal infection
Septicemia (sepsis)
Meningitis
Which group of people are particularly susceptible to meningitis?
Neonates
What are the two sources of opportunistic infections?
Endogenous (own microbiota) and exogenous
What are the different types of specimens that can be cultured?
Wound swab
Pus
Urine
Sputum
Blood
CSF
What does treatment of opportunistic infections depend on?
Antibiotic susceptibility
True or false: nosocomial strains are often multi-resistant.
True
What is used to treat multi-resistant nosocomial strains of opportunistic pathogens?
More potent bactericidal agents
What are the 2 ways of preventing opportunistic nosomial pathogens?
Aseptic technique (esp. hand hygiene)
Education
Is pseudomonas G- or G+?
Gram negative
What morphology is pseudomonas?
Rod
Is pseudomonas motile?
Yes
What is pseudomonas’ relationship with oxygen?
It’s an aerobe or facultative anaerobe
Is pseudomonas fermenting or non-fermenting?
Non-fermenting
Is pseudomonas sporing or non-sporing?
Non-sporing
What would the results for catalase and oxidase be for pseudomonas?
Catalase and oxidase positive
What do some species of pseudomonas, e.g. pseud. aeruginosa, produce?
Pigments - e.g. pyocyanin in ps. aeruginosa.
Why can pseudomonas survive almost anywhere?
Because it has low nutritional requirements
How is pseudomonas divided into species?
According to biochemical tests
What is pseudomonas aeruginosa subtyped according to?
Serotype and biotype
How is pseudomonas aeruginosa subtyped in epidemiological studies?
Using RFLP or MLST (multilocus sequence typing)
In which patients is ps. aerugonisa an important opportunistic pathogen?
Patients with cystic fibrosis
Which species of pseudomonas is a ubiquitous saprophyte?
Pseudomonas aeruginosa
What are the 4 species of of pseudomonas that colonise the respiratory tract of patients with cystic fibrosis?
Ps. aeruginosa
Burkholderia cepacia
Stenotrophomonas maltophilia
Burkholderia pseudomallei
Which species of genera of Burkholdia causes melioidosis?
Burkholderia pseudomallei
What type of environments is ps. aeruginosa particularly found in?
Moist environments
What does ps. aeruginosa transiently colonise?
Skin
Mucous membranes
GIT
Which diseases is ps. aeruginosa mostly associated with as a nosocomial pathogen?
Pneumonia
UTI
Sepsis
Where are most ps. aeruginosa infections acquired from?
Environment
How are ps. aeruginosa inspections spread in hospitals?
On hands and fomites
What are all pseudomonas strains inherently resistant to?
Many antibiotics and weak disinfectants
Which 2 areas can ps. aeruginosa cause superficial infections?
Skin and eye
Which superficial infections of the skin can ps. aeruginosa cause?
Wound infection
Otitis externa
Folliculitis
Which superficial infections of the eye can ps. aeruginosa cause?
Keratitis
Corneal ulcer
Which two types of deep and systemic infections can ps. aeruginosa cause?
Pulmonary
Other
Which pulmonary deep infections can ps. aeruginosa cause?
Nosocomial pneuomina
Chronic infections in patients with cystic fibrosis
Which other deep and systemic infections can ps. aeruginosa cause?
UTI
Endocarditis
Osteomyelitis
Septicaemia
In immunocompromised patients
When will ps. aeruginosa invade the skin?
When in very high numbers
What does ps. aeruginosa adhere to weakly?
Intact epithelium
What does ps. aeruginosa use to adhere to the intact epithelium?
Flagella
Pili
LPS
What components of ps. aeruginosa bind to toll-like receptors?
LPS and flagellin
What effect does binding to toll-like receptors have?
Cytokine production
What does the LPS core of ps. aeruginosa bind to?
CFTR
CF transmembrane conductance region
What does ps. aeruginosa do once it has adhered?
Produces a biofilm
What assists adherence and biofilm formation?
Capsule
What are the properties of ps. aeruginosa biofilms that are different to individual ps. aeruginosa?
More capsule material - mucoid phenotype
More adherent
Less invasive
Shorter LPS (no O-antigen)
Slowed growth
Increased resistance to antibiotics
What is the advantage of the ps. aeruginosa biofilm?
Increased resistance to antibiotics
What are many of the biofilm properties of ps. aeruginosa due to?
Activation of genes that are regulated by quorum sensing
What is quorum sensing?
Regulatory cell process of signalling between bacteria that ensures there is sufficient cell density before a gene product is made, allowing bacteria to increase in numbers before secreting a product, e.g. virulence protein.
What facilitates ps. aeruginosa’s spread through body tissues?
Reduced PMNs
Flagella
Exoenzymes
Exotoxins
LPS-CFTR-mediated invasion
Which exoenzymes does ps. aeruginosa use to spread through body tissues?
Proteases
Haemolysins
Phospholipases
Elastase
Which exotoxins does ps. aeruginosa use to spread through body tissues?
Exotoxin A
Exoenzymes S and U
These inhibit phagocytosis
What effect does LPS-CFTR-mediated invasion by ps. aeruginosa have?
Aggravates corneal damage
What happens in patients with a defect in CFTR?
Abnormal ion transport
Thickened mucus
Impaired mucociliary function
Are pseudomonas and staph. inhibited by high salt concentrations?
No
What do bacteria in biofilms resist?
Mechanical removal
Are bacteria in biofilms more or less visible to the innate immune system?
Less
What happens when DNA is secreted from the bacteria and dying cells in a biofilm?
Leads to thickened mucous
Which bacterial variants will persist?
Those with reduced virulence
What effect do the type III secreted proteins from ps. aeruginosa have?
Exoenzymes S, T, U and Y (=ExoS, ExoT, ExoU, ExoY) act on host cell targets to interfere with phagocytosis and enhance cytokine production
What does exotoxin A released from ps. aeruginosa do?
Blocks protein synthesis (same as diphtheria toxin)
What do LasA and LasB proteases released from ps. aeruginosa do?
Act together as elastase
What do phospholipases released from ps. aeruginosa do?
Damages cell membranes
Degrades surfactant
Can pseudomonas be eradicated from the environment?
No
How can ps. aeruginosa be controlled?
Reduce risk of susceptible patients by suitable management of burns, neutropenia, catheters, ventilators
Be on alert for infection and treat early
Practice high levels of hand hygiene
Use contact lenses and solutions appropriately
Lifelong monitoring and treatment of CF patients
What allows ps. aeruginosa to occupy many different environments?
Its low nutritional requirements and genetic versatility
What is the leading cause of hospital-acquired infections?
Ps. aeruginosa
What does ps. aeruginosa have a preference for in humans?
Situations where innate immunity is reduced
What is the key to controlling pseudomonas infections?
Prevention
