BMS2037 Pseudomonas 2023 PDF

BMS2037 Pseudomonadaceae & other opportunistic pathogens Pseudomonads and long-lost relatives Dr Alison Cottell Aims: Introduce the group, with main focus on Pseudomonas aeruginosa Focus on clinical significance of the group, with reference to environmental significance of Pseudomonas syringae...

BMS2037 Pseudomonadaceae & other opportunistic pathogens Pseudomonads and long-lost relatives Dr Alison Cottell Aims: Introduce the group, with main focus on Pseudomonas aeruginosa Focus on clinical significance of the group, with reference to environmental significance of Pseudomonas syringae Learning outcomes: Be familiar with this diverse group; the phylogeny; nature, and key members Understand diverse roles of members in the group Understand P. aeruginosa as the epitome of an opportunistic pathogen Be familiar with the diversity of species within the Burkholderia genus Classification of the Pseudomonadaceae Domain Bacteria Phylum Proteobacteria Class Beta Gamma Order Burkholderiales Pseudomonadales Family Burkholderiaceae Pseudomonadaceae Genus Burkholderia Pseudomonas Species cepacia aeruginosa Characteristics Gram-negative Polar flagella Strictly aerobic (Zyomonas ??) Many genera and species within the group, including: Pseudomonas Burkholderia Xanthamonas Rastonia Zyomonas Sphingomonas Stenotrophomonas P aeruginosa: infections in humans Capsule Pathogenesis: No single mechanism – multifactorial Structural: • Adhesins / pili / EPS / LPS • Capsule (evades immune cells & antibiotics) • Pyocyanin: impairs ciliary function. Stimulates inflammatory response. A siderophore. Exotoxins: Inhibit protein synthesis; tissue damage Cytotoxin: Leukocyte damage; pulmonary injury Enzymes: Elastase; protease; haemolysins. Variety of cell and tissue damage Pyocyanin P aeruginosa: infections in humans Opportunistic: exploits failings in host defences to initiate infection P aeruginosa: infections in humans Gastrointestinal: any part (oropharynx to rectum) in immunocompromised Skin and soft tissue: After breakdown of integument (burns, trauma, dermatitis, high moisture conditions (swimmers; toe webs of athletes and troops; divers; perineal region; under nappies of infants) Burn Toe web Hot tub folliculitis Eye Understanding the wider role and impact of the Pseudomonadaceae 1. Aside from infections, where may people commonly encounter bacteria from the Pseudomonad group? 2. Aside from Pseudomonas, which genera may cause infections in humans? 3. Which genera from the list may cause a significant type of infection in animals? 4. What features of P. aeruginosa and related pseudomonads may be responsible for an increase in bacteraemia caused by these species over the last ~ 30 years? 1. Aside from infections, where may people commonly encounter bacteria from the Pseudomonad group? Ubiquitous in the environment • soil • decaying organic matter • vegetation • water Members of the Pseudomonadaceae may be pathogen of plants and animals Many genera and species within the group, including: Pseudomonas Burkholderia Xanthamonas Rastonia Zyomonas Sphingomonas Stenotrophomonas Plant pathogens of the Pseudomonad group Plant pathogen 1. Ralstonia solanacearum 2. Pseudomonas syringae 3. Pseudomonas marginalis 1 2 Disease Wilt diseases of many cultivated plants (potatoes, tomatoes) Chlorosis and necrotic legions on leaves Pectinolytic, soft rots 3 P. aeruginosa Ubiquitous– can multiply in nutritionally poor environments • API 20NE assimilation tests • Aviation fuel • Distilled water • Photographic chemicals • Cosmetics • Plasticisers Faecal carriage rates are between 15 – 25% (higher in vegetarians) Faecal carriage rates 15% 25% Pseudomonas syringae https://www.youtube.com/watch?v= pH-afIrfUbQ 2. Aside from Pseudomonas, which genera may cause infections in humans? Many genera and species within the group, including: ✓ Pseudomonas ✓ Burkholderia Xanthamonas ✓ Rastonia Zyomonas ✓ Sphingomonas ✓ Stenotrophomonas 2. Aside from Pseudomonas, which genera may cause infections in humans? Plant pathogen Disease Pseudomonas aeruginosa Model opportunistic pathogen: Immunosuppressed; cystic fibrosis; burns patients Pseudomonas fluorescens Poor pathogens. Can grow at 4o C – Pseudomonas putida rare cases of endotoxic shock from contaminated blood products Burkholderia cepacia Opportunistic infection in CF lung infections Burkholderia mallei Glanders in horses – rarely in humans Burkholderia pseudomallei Melioidosis in humans and farm animals – tropics/ subtropics Non-pathogenic species may cause medical problems: e.g. contamination of blood bank products P aeruginosa: infections in humans Opportunistic: exploits failings in host defences to initiate infection Burkholderia pseudomallei – melioidosis Occurrence Occurs as a saprophyte in parts of Southeast Asia, India, Africa, and North Australia Found in soil, water, rice paddies. Long term environmental survival (14 years!) Impact Melioidosis causes severe infections in animals and humans in some tropical countries (20% of community acquired septicaemia in Thailand; ~35 – 75% case fatality) Infections Clinically similar to Glanders. Localised infection – lesions result from inoculation through a break in the skin – may progress to the bloodstream. Pulmonary infection – mild bronchitis to severe pneumonia Main difference from B. mallei: geographic distribution and habitat. A. Pulmonary disease: diabetic patient B. Cutaneous disease C. Abscess Note: Diabetes; renal failure, and HIV raise severity of melioidosis – high risk of septic shock Burkholderia pseudomallei – melioidosis Infections Patients with latent melioidosis may be symptom-free for decades. The longest period between presumed exposure and clinical presentation is ~62 years. Dubbed the “Vietnam time-bomb” following military activity and soil disturbance. Animals Widespread. In 1975 a panda introduced to a Paris zoo caused a major outbreak – serious damage to a number of zoo populations and equestrian clubs. 3. Which genera from the list may cause a significant type of infection in animals? Many genera and species within the group, including: Pseudomonas Burkholderia Xanthamonas Rastonia Zyomonas Sphingomonas Stenotrophomonas 3. Which genera from the list may cause a significant type of infection in animals? Burkholderia mallei – causes glanders Occurrence Solipeds (horses & donkeys) Endemic in parts of Africa; Asia; Middle East Rare in humans: vets; grooms & riders; butchers etc. Glanders symptoms Ulceration and cutaneous lesions Pulmonary abscesses Septicaemia Chronic: multiple abscesses (muscles; joints; spleen; liver) Biological weapon Low infectious dose; easy to produce; pulmonary/ septicaemia have high mortality (even when treated); slow to diagnose Glanders affected Russian military horses in WW1 – biowarfare? Glanders: Cutaneous ulcer formation Outbreak in a Chinese village in 1942-3. Suspected Japanese attacks. (Disease eradicated in China in 1906) 4. What features of P. aeruginosa and related pseudomonads may be responsible for an increase in bacteraemia caused by these species over the last ~ 30 years? Many genera and species within the group, including: Pseudomonas Burkholderia Xanthamonas Rastonia Zyomonas Sphingomonas Stenotrophomonas P aeruginosa: infections in humans Capsule Pathogenesis: No single mechanism – multifactorial Structural: • Adhesins / pili / EPS / LPS • Capsule (evades immune cells & antibiotics) • Pyocyanin: impairs ciliary function. Stimulates inflammatory response. A siderophore. Exotoxins: Inhibit protein synthesis; tissue damage Cytotoxin: Leukocyte damage; pulmonary injury Enzymes: Elastase; protease; haemolysins. Variety of cell and tissue damage Pyocyanin P. aeruginosa survives in hospital environments: • Mops • Sinks / Toilets • Dialysis equipments • Respiratory tubing • Cut flowers Related members of this group also appear as opportunists Burkholderia cepacia Target research paper There will be five MCQ questions in Test 1 based on this research paper – available on SurreyLearn.