Lecture 6.1 - Infections on surfaces

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Questions and Answers

What is the primary mechanism by which bacteria form biofilms?

Quorum sensing

Adherence to host cells or prosthetic surface (correct)

Invasion and multiplication

Host response

Which of the following is NOT a symptom of infection?

Purulence or erythema

Headache (correct)

Malaise

Fever

What is the primary goal of diagnosis in infection management?

To determine the antimicrobial susceptibilities

To identify the infecting organism (correct)

To develop a treatment plan

To monitor the patient's immune response

Which of the following bacteria is NOT typically associated with endocarditis?

Pseudomonas aeruginosa Signup and view all the answers

What is the primary function of quorum sensing in bacteria?

To coordinate virulence factor secretion Signup and view all the answers

What is the primary challenge in diagnosing infections related to prosthetic surfaces?

Adherent organisms Signup and view all the answers

What is the primary aim of treatment in infection management?

To sterilize tissue Signup and view all the answers

Which of the following investigations is NOT typically used to diagnose infections?

Genetic testing Signup and view all the answers

What is the primary function of the surface of the GI tract in relation to microorganisms?

To provide a site for microorganisms to establish infection Signup and view all the answers

Which of the following microorganisms is NOT a type of fungus that can be found on the skin?

Bacteriophage Signup and view all the answers

What is the primary cause of pneumonia?

Infection of one or both lungs Signup and view all the answers

Which of the following is an example of an internal surface infection?

Endocarditis Signup and view all the answers

What is the primary characteristic of cystic fibrosis?

Build-up of mucus in the lungs and digestive system Signup and view all the answers

Which of the following microorganisms is commonly found in the skin and is a Gram-positive bacterium?

Staphylococcus aureus Signup and view all the answers

What is the primary site of infection for Pseudomonas aeruginosa in patients with cystic fibrosis?

Lungs Signup and view all the answers

Which of the following is an example of an artificial surface that can provide a site for microorganisms to establish infection?

Central venous line catheter Signup and view all the answers

What type of adhesins are usually components of the bacterial cell membrane, cell wall or capsule?

Polysaccharide adhesins Signup and view all the answers

Which of the following prosthetic surface infections is NOT an example of an intravascular device?

Prosthetic joints Signup and view all the answers

What is the approximate incidence of infection for primary hip replacement?

0.43% Signup and view all the answers

Which of the following microorganisms is NOT typically associated with early post-operative infections of joint replacements?

Pseudomonas aeruginosa Signup and view all the answers

What is the main function of adhesins in bacterial infection?

To promote bacterial adherence to host surfaces Signup and view all the answers

Which of the following is an example of a non-fimbrae protein adhesin?

Lipoteichoic acid Signup and view all the answers

What is the typical duration of antibiotic therapy for prosthetic joint infections?

Months Signup and view all the answers

Which of the following is NOT a source of infection in an IV line?

Prosthetic joint Signup and view all the answers

Study Notes

Surfaces

Interface between a solid and either a liquid or gas
Natural body surfaces: skin, GI tract, urinary tract
Artificial surfaces: intravenous lines, central venous line catheters, NG tubes, prosthetic devices, and implants

Microorganisms on Skin

Viruses: papilloma, herpes simplex
Bacteria:
- Gram positive: Staphylococcus aureus, coagulase negative staphylococci, Corynebacterium
- Gram negative: Enterobacteriaceae
Fungi: yeasts, dermatophytes
Parasites: mites

Mucosal Microflora

No specific information provided

Natural Infection Sites

External surfaces:
- Pharyngitis (sore throat)
- Conjunctivitis (infection of conjunctiva)
- Gastroenteritis (inflammation of the gastrointestinal tract)
- Urinary tract infection (infection in any part of the urinary system)
- Pneumonia (infection of one or both lungs)
Internal surfaces:
- Endocarditis (infection of the endocardium)
- Septic arthritis (joint infection)
- Osteomyelitis (infection of the bone)
- Empyema (pus in the pleural cavity)

Cystic Fibrosis

Mucus build-up in lungs and digestive system
Persistent lung infections:
- Pseudomonas aeruginosa
- Mycobacterium abscessus
- Aspergillus species

Adhesins

Proteins that help bacteria bind to host surfaces (e.g., skin, mucous membranes, deeper tissues)
Examples: fimbriae (pili) in E. coli, non-fimbriae proteins, and polysaccharide adhesins
Teichoic acids in gram-positive bacteria serve as adhesins for staphylococcus and streptococcus species

Prosthetic Surface Infections

Examples:
- Intravascular lines
- Central venous catheters
- Peritoneal dialysis catheters
- Prosthetic joints
- Breast prostheses
- Cardiac valves
- Pacing wires
- Endovascular grafts
- Ventriculoperitoneal shunts

Prosthetic Joint Infections

Result in morbidity and are costly
Require antibiotic therapy for weeks/months
Longer stay in hospital
Incidence of infection:
- Hip replacement: approximately 0.43% for primary and 1.58% for revision
- Knee replacement: approximately 0.54% for primary and 2.1% for revision

Microorganisms Causing Infections of Joint Replacements

Early post-operative infections (<1 month):
- S. aureus
- Gram-negative organisms (E. coli, Proteus, Klebsiella)
- Enterobacteraceae
- Enterococci (E. faecalis)
Late post-operative infections (2-12 months):
- Coagulase negative staphylococci (mainly S. epidermidis)
- S. aureus
- Other species (e.g., S. haemolyticus, S. simulans, S. warneri)

Endocarditis (Prosthetic and Non-Prosthetic Valve)

Coagulase negative staphylococci (including S. epidermidis)
S. aureus
Viridans streptococci
Enterococcus faecalis
HACEK group (Haemophilus, Aggregatibacter, Cardiobacterium, Eikenella, Kingella)
Candida

Cardiac Pacing Wire Endocarditis

No specific information provided

Processes in the Pathogenesis of Infection at Surfaces

Adherence to host cells or prosthetic surface
Biofilm formation
Invasion and multiplication
Host response

Biofilms

Stages of biofilm formation:
- Attachment
- Maturation
- Dispersion

Quorum Sensing

Controls:
- Sporulation
- Biofilm formation
- Virulence factor secretion
Three principles:
- Signalling molecules (autoinducers)
- Cell surface or cytoplasmic receptors
- Gene expression -> co-operative behaviours and more AI production

Symptoms of Infection

Fever
Inflammation at the site of insertion
Purulence or erythema
Pain
Malaise

Investigations

Full blood count (FBC)
C-reactive proteins
ESR
Blood culture (gram stain, antibiotic sensitivity)
Samples (fluid, biopsy) - bacterial growth; PCR
Scans

Management

Diagnosis:
- Aim is to identify infecting organism and its antimicrobial susceptibilities
- Challenges: adherent organisms, low metabolic state/small colony variants
- Blood cultures
- Tissue/prosthetic material sonication and culture
Treatment:
- Aim is to sterilize tissue
- No specific information provided

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Description

Learn about the different types of surfaces, including natural and artificial ones, and the various microorganisms that can inhabit them, such as viruses and bacteria. This quiz covers the basics of microbiology and skin microorganisms.