RCSI Aerobic Gram Negative Bacilli (GNB) 1 Past Paper PDF 2024

RCSI Royal College of Surgeons in Ireland Coláiste Ríoga na Máinleá in Éirinn SESSION ID: GIHEPMicroL1 Aerobic Gram Negative Bacilli (GNB) 1 *Coliforms, *Proteus, Pseudomonas Class Year 2 Course Undergraduate Medicine Lectu...

RCSI Royal College of Surgeons in Ireland Coláiste Ríoga na Máinleá in Éirinn SESSION ID: GIHEPMicroL1 Aerobic Gram Negative Bacilli (GNB) 1 *Coliforms, *Proteus, Pseudomonas Class Year 2 Course Undergraduate Medicine Lecturer Dr. Rachel Grainger Date 10th September 2024 * The term “Enterobacterales” includes these  Learning Outcomes By the end of the lecture, you will be able to: 1. Outline the basic laboratory features of clinically important Enterobacterales & Pseudomonas species and explain the biological role of each in the pathogenesis of infection 2. Discuss the epidemiology of clinically important Enterobacterales & Pseudomonas species 3. Describe the pathogenesis of infections caused by clinically important Enterobacterales & Pseudomonas species 4. Recognise and describe the clinical features and complications of infections caused by clinically important Enterobacterales & Pseudomonas species.  Learning Outcomes By the end of the lecture, you will be able to: 5. Outline the laboratory diagnosis of infections caused by clinically important Enterobacterales & Pseudomonas species and describe their laboratory features e.g. Gram stain appearance etc. 6. Choose the appropriate antimicrobial agents to treat infections caused by clinically important Enterobacterales & Pseudomonas species 7. Use the appropriate measures to prevent the acquisition and spread of infections caused by clinically important Enterobacterales & Pseudomonas species Introduction 1. Enterobacterales a. A family of gram-negative (pink) bacilli (rod-shapped) b. ‘Enteric’ = relating to or occurring in the intestines (GIT is their habitat) c. Common causes of intra-abdominal, respiratory tract & bloodstream infections d. Increasing antibiotic resistance with these organisms i. Beta-lactamase production including extended-spectrum beta-lactamases (ESBLs) 2. Pseudomonas spp. & related genera ENTEROBACTERALES: CLASSIFICATION Normal intestinal flora Escherichia coli Important organisms, Klebsiella spp. covered in this Proteus spp. lecture, revise GNB lecture in FFP2 also Others Serratia spp. Enterobacter spp. Less important Citrobacter spp. Pathogens (not normal flora) Salmonella spp. Important, covered in next Shigella spp. lecture Yersinia spp. Important, covered in Enteric Toxin-producing E.coli infections ENTEROBACTERALES: MICROBIOLOGY Most are motile with flagellae Facultative anaerobes Ferment glucose and other carbohydrates May be lactose fermenters or non-lactose fermenters  ENTEROBACTERALES: STRUCTURE Cell wall (contains Capsule (contains lipopolysaccharide O-antigen) K-antigen) Fimbriae Flagella (H-antigen) ENTEROBACTERALES: STRUCTURE (THE GRAM- NEGATIVE CELL WALL) Composed of: O-side-chains Lipid A  Pathogenesis Gets in – portal of entry Contact, environment, Adhesins, pili AMR Gets out & Attaches to spreads further cells LPS, toxins Causes Defeats/evades Capsule damage to host the immune cells system VIRULENCE FACTORS Adhesins – aid in binding to host cells, e.g. fimbriae Capsules – help avoid phagocytosis but poor immunogens Lipopolysaccharide – potent inducer of host immune response via endotoxin release (lipid A) – Endotoxin  activation of complement, cytokines & WBCs  decrease in platelets  DIC  fever, hypotension, death Toxins – e.g. haemolysins of E. coli Antimicrobial resistance – e.g. via plasmid exchange  ENTEROBACTERALES: ESCHERICHIA COLI Normal GI flora in humans (esp. in the colon) Most strains are non- pathogenic Microbiology Lactose fermenters Grow well on non- http://www.emlab.com/s/sampling/env-report-02-2007.html selective media ESCHERICHIA COLI Causes a wide range of infection Community-acquired: – Urinary tract infection (UTI) – Bloodstream infection (BSI) – Intra-abdominal infection: cholecystitis, appendicitis – Neonatal meningitis Healthcare-associated: – Healthcare-associated pneumonia – Post-operative intra-abdominal pus collection – Bloodstream infection (BSI) Gastroenteritis (toxin-producing strains only) URINARY TRACT INFECTION (UTI) E. coli = most common cause of UTI in the community (~80%) & in hospitals (~50%) Originates from the perianal area & travels along the urethra to the bladder – Shorter in females hence why UTI more common – May spread from the bloodstream to urinary tract (