RCSI Aerobic Gram Negative Bacilli (GNB) 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 OTHER INFECTIONS CAUSED BY E. COLI Intra-abdominal infections (including those previously mentioned): – Appendicitis, Acute cholecystitis, Peritonitis – Liver & Sub-phrenic abscesses Meningitis – Neonate Early onset: after delivery, acquired during birth Late onset: up to 3 months/neonatal period; may have been acquired during birth or later – Other age groups: post-traumatic / post-operative, e.g. major road traffic accident, neurosurgical procedures Bloodstream infection (BSI) – Sources of endotoxic or gram-negative septic shock may be: Intra-abdominal pathology Urinary tract sepsis Neonatal meningitis  TREATMENT OF E. COLI INFECTIONS Depends on source, patient factors, resistance patterns Many E.coli are amoxicillin resistant Additional antibiotic resistance more common in hospitals with various resistance mechanisms e.g., ESBL Source:www.hpsc.ie ENTEROBACTERALES: KLEBSIELLA SPP. Microbiology Lactose fermenters i.e., pink on MacConkey agar Mucoid colonies KLEBSIELLA SPP. K. pneumoniae, K. oxytoca Normal inhabitant of the GIT of healthy humans Are NOT associated with gastroenteritis/diarrhoeal disease May be resistant to multiple antibiotics – e.g. ESBL, CPE Infections  cause healthcare associated infections (HCAIs) – Pneumonia, including ventilator-associated pneumonia (VAP) – Urinary tract infection (UTI) – less commonly than E. coli – Intra-abdominal infections – appendicitis, cholecystitis – Bloodstream infection (BSI) KLEBSIELLA PNEUMONIAE & PNEUMONIA – In alcoholics, compromised respiratory function – Necrotizing pneumonia, “red currant jelly” sputum – Often affects upper lobes; may cause abscesses – Also causes ventilator-associated pneumonia ESBL: EXTENDED-SPECTRUM BETA- LACTAMASE Enzymes carried by Enterobacterales (e.g. E.coli, Klebsiella spp.) which make them resistant to: – Cephalosporin antibiotics – Sometimes co-amoxiclav (“Augmentin”) – Sometimes piperacillin-tazobactam (“Tazocin”) Cause UTIs, intra-abdominal infections High prevalence of ESBL producers in nursing homes in Ireland  IS THERE A PROBLEM WITH MULTIPLE ANTIMICROBIAL RESISTANCE IN ENTEROBACTERALES?? Electron microscopic image by Charles C. Brinton, Jr. Plasmid The genes for CPE & ESBL enzymes are carried on PLASMIDS A plasmid is a piece of genetic material which can easily be transmitted from one bacterium to another CPE: CARBAPENEMASE-PRODUCING ENTEROBACTERALES Enterobacterales (e.g. E.coli, Klebsiella spp.) resistant to meropenem (our “last-resort” antibiotic) – They produce enzymes called carbapenamases e.g. IMP, KPC, OXA-48, NDM Also resistant to many other classes of antibiotics Live in the bowel More & more evidence that CPE widespread in hospital environment Management of infection with these organisms is a challenge (e.g. UTIs, intra-abdominal infection)  CPE IN IRELAND 2013-2022 Source: HPSC – Enhanced surveillance of CPE in Ireland ENTEROBACTERALES: PROTEUS MIRABILIS Microbiology Non-lactose fermenter Characteristic “swarming” on agar: spreads out and takes over the plate Unpleasant fish-like smell Oxidase-negative  ENTEROBACTERALES: PROTEUS MIRABILIS Proteus mirabilis is most common Proteus species causing infection Normal GI flora; may be pathogenic at other sites May cause: – Urinary tract infection (Patients with urinary tract abnormalities/long-term catheters) – Bloodstream infection (Often related to urosepsis) Infection is often healthcare-associated ENTEROBACTERALES: PROTEUS MIRABILIS ENTEROBACTERALES: ENTEROBACTER SPP., SERRATIA SPP., CITROBACTER SPP. May form part of the normal intestinal flora but are typically found in the environment Not intrinsically pathogenic Cause healthcare-associated infections (HCAI) (e.g., pneumonia, intravascular catheter sepsis, UTI, abdominal wound), infection/abscess) in at-risk patients Often resistant to multiple antibiotics  PSEUDOMONAS SPP. EPIDEMIOLOGY Pseudomonas aeruginosa is the most important clinically Widespread in moist areas in the environment – Sinks, drains – Also soil, plants, animals Difficult to treat – Intrinsically resistant to many antibiotics – Acquires resistance quickly Forms biofilm e.g., in taps http://ru.pall.com/main/medical/scientific-information-45031.page  P. AERUGINOSA: MICROBIOLOGY Non-lactose fermenter Oxidase positive Strict aerobe P. AERUGINOSA: MICROBIOLOGY Mucoid variants of Pseudomonas aeruginosa are seen in cystic fibrosis. These form biofilm in the respiratory tract. VIRULENCE FACTORS Pili Flagellae (adhesins), Polysaccharide capsule, Pyocyanin which impairs cilia Endotoxin, i.e. lipopolysaccharide  Pathogenesis Gets in – portal of entry Contact, environment, Adhesins, pili AMR Gets out & Attaches to spreads further cells Capsule, LPS, toxins Causes Defeats/evades biofilm, damage to host the immune pyocyanin cells system P. AERUGINOSA: CLINICAL PRESENTATIONS Bloodstream infection (e.g. in burns patients) Neutropenic sepsis (e.g., in haematology/oncology patients) Outbreaks in NICU - Preterm babies Pneumonia – Acute pneumonia in ventilated patients (VAP) – Chronic colonisation/infection in http://www.medscape.org/viewarticle/458771_5 cystic fibrosis, and bronchiectasis Urinary tract infection – Often complicated UTI, associated with urinary catheters P. AERUGINOSA: CLINICAL PRESENTATIONS Eye infection – Post- trauma or surgery – Associated with contaminated fluids e.g., contact lens solutions – Can lead to destruction of eye http://webeye.ophth.uiowa.edu/eyeforum /cases/171-pseudomonas-keratitis.htm Ear infections – Otitis externa in swimmers – May be severe in diabetics: malignant otitis externa TREATMENT OF P. AERUGINOSA Fewer treatment options than coliforms as intrinsically resistant to many antibiotics - Piperacillin-tazobactam - Ceftazidime (3rd generation cephalosporin) - Ciprofloxacin (quinolone) - Aminoglycosides e.g. gentamicin - Carbapenems e.g. meropenem (reserved)  OPPORTUNISTIC PATHOGENS Organism of low intrinsic virulence which cause infection when the host defences are impaired Typically in patients whose immune system is compromised by disease or treatment of disease (e.g. malignancy, high dose corticosteroids)  BURKHOLDERIA CEPACIA A major cause of opportunistic infection in the lungs of patients with cystic fibrosis (CF) Easily transmitted by social contact Multi-resistant and difficult to treat Causes “cepacia syndrome” – Acute fatal necrotising pneumonia +/- BSI BURKHOLDERIA PSEUDOMALLEI Causes melioidosis, seen in SE Asia, AUS Reservoir: water e.g. paddy fields May cause severe pneumonia with BSI & high mortality even in normal hosts  STENOTROPHOMONAS MALTOPHILIA An opportunistic pathogen May be a coloniser in – Hospitalised patients – Respiratory tract of patients with cystic fibrosis Usually following prolonged broad- spectrum antibiotics – Bloodstream infections (often associated with central venous catheter) http://lib.jiangnan.edu.cn/ASM/112-19.jpg – Pneumonia Intrinsically resistant to many antibiotics  ACINETOBACTER BAUMANNII Epidemiology: Can survive on wet & dry surfaces in hospital environments Multi-resistant strains occur – e.g., seen in injured US soldiers returning from Iraq & Afghanistan in 2000s – Can be associated with hospital outbreaks, especially in ICU setting – Very limited treatment options  SUMMARY There is increasing recognition of relatively non-pathogenic GNBs as a cause of opportunistic infection Emerging – and spreading – antibiotic resistance in these organisms (e.g., ESBL- producers, CPE) is a major challenge