RCSI Aerobic Gram-Negative Bacilli (GNB) 1 PDF

Leading the world to better health Aerobic Gram- Negative Bacilli (GNB) 1 Dr. Rachel Grainger Clinical Lecturer Dept. of Clinical Microbiology, RCSI  RCSI Royal College of Surgeons in Ireland Coláiste Ríoga na Máinleá in...

Leading the world to better health Aerobic Gram- Negative Bacilli (GNB) 1 Dr. Rachel Grainger Clinical Lecturer Dept. of Clinical Microbiology, RCSI  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. Shigella spp. Important, covered in next Yersinia spp. lecture Toxin-producingImportant, covered in Enteric infections E.coli 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  CASE SCENARIO 1 A 22-year-old female attends her GP C/o urinary frequency & dysuria Otherwise systemically well Has not recently been on antibiotics She has no PV discharge. WHICH ONE OF THE FOLLOWING IS THE MOST LIKELY DIAGNOSIS? A.Cervical carcinoma B.Chlamydia urethritis C.Cystitis D.Pyelonephritis E.Vaginal thrush  CASE SCENARIO 1 Empiric Treatment ( www.antibioticprescribing.ie ): NITROFURANTOIN PO for 3 days TRIMETHOPRIM PO for 3 days FOSFOMYCIN single dose  CASE SCENARIO 1 Laboratory Report: Day 1: Urine white cell count >100/ µl Day 2: E. coli isolated from urine; susceptibilities pending Day 3: E. coli – SUSCEPTIBLE to NITROFURANTOIN / TRIMETHOPRIM She completes a three day course of nitrofurantoin Symptoms resolve & she requires no further investigations or follow-up CASE SCENARIO 2 A 36-year-old female presents to the ED with vomiting, left flank pain and a temperature of 38.8oC. WHICH OF THE FOLLOWING IS THE MOST LIKELY SOURCE? A. Appendicitis B. Diverticulitis C. Pneumonia D. Pancreatitis E. Pyelonephritis WHICH OF THE FOLLOWING MICROBIOLOGY INVESTIGATIONS ARE MOST IMPORTANT INITIALLY? A. Aspirate from left kidney for Gram stain B. Blood cultures alone C. Faeces (stool) for culture/PCR D. MSU & Blood cultures E. Pro-calcitonin level CASE SCENARIO 2 Empiric Treatment (Guidelines App): IV CEFUROXIME +/- GENTAMICIN Laboratory Report Day 1: Urine white cell count >100/ µl Day 2: Escherichia coli isolated from urine; susceptibilities pending Day 3: Escherichia coli – RESISTANT to TRIMETHOPRIM / CO-AMOXICLAV – SUSCEPTIBLE to NITROFURANTOIN / CEFUROXIME / GENTAMICIN N.B. Nitrofurantoin not suitable in this case  CASE SCENARIO 3 A 2-day-old baby presents with: – Tachypnoea – Feeding poorly – Irritable when handled Meningitis is suspected WHICH ONE OF THE FOLLOWING IS THE MOST LIKELY CAUSATIVE PATHOGEN? A. Bordetella pertussis B. E. coli C. Haemophilus influenzae D. Staphylococcus epidermidis E. Streptococcus pneumoniae  CASE SCENARIO 3 Empiric Treatment (Temple St. Guidelines): IV CEFOTAXIME / AMOXICILLIN / GENTAMICIN  CASE SCENARIO 3 Empiric Treatment (Temple St. Guidelines): IV CEFOTAXIME/AMOXICILLIN/GENTAMICIN Laboratory Report (CSF Microscopy, Culture and Susceptibilities) Day 1: CSF white cell count 600/µl (normally