18. Microbiology of Cystic Fibrosis.pdf

Microbiology of Cystic Fibrosis Lungs Susu M Zughaier, PhD Associate Professor of Microbiology College of Medicine, Qatar University March 20, 2024 Learning Objectives Describe the microbiology of Cystic Fibrosis (CF) lungs in early childhood, adolescence and adulthood Explain mechanisms of pathogen...

Microbiology of Cystic Fibrosis Lungs Susu M Zughaier, PhD Associate Professor of Microbiology College of Medicine, Qatar University March 20, 2024 Learning Objectives Describe the microbiology of Cystic Fibrosis (CF) lungs in early childhood, adolescence and adulthood Explain mechanisms of pathogenesis and virulence factors of common pathogens in CF lungs Describe biofilm formation leading to antibiotic resistance in CF lungs Describe the relation between pulmonary exacerbations and lung function decline Digital stethoscope for lung auscultations (AI in Medicine) What is Cystic Fibrosis (CF)? CF is a multisystem disease affecting the lungs, digestive system, sweat glands, and the reproductive tract Lungs are the major system and progressive lung disease is the major cause of morbidity and mortality for most patients Over a highly variable time course ranging from months to decades after birth, individuals eventually develop chronic infection of the respiratory tract leading to lung function decline and respiratory failure (steatorrhoea) What Causes Cystic Fibrosis? Cystic Fibrosis is an inherited autosomal recessive genetic disease caused by mutation in both copies of the gene that encodes CFTR protein in chromosome 7 CFTR: ABC transporterclass ion channel CFTR (Cystic Fibrosis Transmembrane Conductance Regulator) is an ABC transporter class, ion channel protein that conducts chloride CFTR: Transmembrane Chloride channel Figure 1. Normal vs. CF Airway. Schematic drawings of normal and CF airways, illustrating selected components of epithelial apical ion transport. (A) Secreted mucins are produced by submucosal glands in the large airways and surface goblet cells, forming the overlying, mucinrich component of the airway surface layer (ASL). This layer is normally transported by effective beating of cilia in the periciliary layer (PCL). ASL hydration is largely controlled by the balance of chloride secretion through CFTR and sodium reabsorption by the epithelial sodium channel (ENaC). (B) Mucin overproduction from hypertrophic submucosal glands and hyperplastic surface goblet cells characterize the CF large airways. Non-functional or absent CFTR leads to diminished chloride transport and increased sodium transport through ENaC. Airway dehydration reduces the PCL, impairing mucociliary transport. Accumulation of thick, sticky mucus increases overall ASL thickness and promotes a low pH environment favoring chronic bacterial infection and inflammation. The CF ASL environment is a likely barrier for cell therapy. https://www.frontiersin.org/journals/pharmacology/articles/10.3389/fphar.2019.00074/full Pathophysiology of CFTR mutation Defective CFTR results in decreased secretion of chloride and increased reabsorption of sodium and water across epithelial cells The resultant reduced height of epithelial lining fluid (airway surface liquid) and decreased hydration of mucus results in mucus that is stickier to bacteria, which promotes infection and inflammation CF is a multisystem disease Major long term complications: Progressive lung disease CF related diabetes (CFRD) Liver diseases & intestinal obstruction Osteoporosis & infertility in men Pathophysiology of CFTR mutation Secretions in the respiratory tract, pancreas, GI tract, sweat glands, and other exocrine tissues have increased viscosity, which makes them difficult to clear (Too Sticky) Too sticky Defective chloride channel Pathophysiology of Cystic Fibrosis Respiratory System is the most affected in Cystic Fibrosis Airway infections are the major cause of morbidity and mortality in CF Frontiers in Pharmacology 7(e98502):275 · September 2016 Microbiology of Cystic Fibrosis Lungs Newborn lungs: Healthy airway with surface liquid & cilia The abundance of nutrients within sputum facilitates pathogen colonization, increase neutrophil recruitment and sputum accumulation Early Childhood: Impaired mucociliary clearance and defective immune responses Late stages of CF disease: Increased host inflammatory responses and epithelial damage, increasing the abundance of pathogens and Biofilm formation PLOS Pathogens | DOI:10.1371/journal.ppat.1005846 Microbiology of Cystic Fibrosis Lungs The most common pathogens causing disease in CF patients: Staphylococcus aureus Methicillin-resistant S. aureus (MRSA) Pseudomonas aeruginosa Multidrug-resistant P. aeruginosa (MDR-PA) Haemophilus influenza (HiB vaccine available) Burkholderia cepacia complex Stenotrophomonas maltophilia Acromobacter xylosoxidance Aspergillus fumigatus Nontuberculous mycobacteria Too sticky Bhagirath et al. BMC Pulmonary Medicine (2016) 16:174 Common Pathogens in Early, Late Childhood and adult CF Adolescents Adults Children Staphylococcus aureus is most common in childhood whereas Pseudomonas aeruginosa is most common in adults Pathogenesis Mechanisms & Virulence Factors Bacterial pathogens that cause infections in CF airways possess major virulence factors such as its ability to adhere, colonize and invade the host epithelial cells; secretion of toxins, production of pigments and protective exopolysaccharides such as alginate and its ability to resist host defenses. Dysfunctional host defenses in Cystic Fibrosis facilitates bacterial infections CF disease is characterized by neutrophil influx to the airway Inability of CF patients to clear infections clearly points to a dysfunctional innate immunity Staphylococcus aureus Virulence Factors and Pathogenesis Staphylococcus aureus is a Gram positive cocci in clusters, facultative anaerobic bacteria MRSA: is methicillin resistant S. aureus Common clinical pathogen causing wide range of infections in skin, soft tissue and deep tissues Leading cause of blood stream, lower respiratory tract infections MRSA are hospital-acquired as well as communityacquired infections. S. aureus annual mortality rate exceeds that of most infectious diseases No vaccine is available FYI https://link.springer.com/chapter/10.1007/978-3-642-19940-0_7 Staphylococcus aureus Virulence Factors https://link.springer.com/chapter/10.1007/978-3-642-19940-0_7 FYI Pseudomonas aeruginosa Pseudomonas aeruginosa is a dominant pathogen in people with cystic fibrosis (CF) contributing to morbidity and mortality. Its tremendous ability to adapt greatly facilitates its capacity to cause chronic infections. The adaptability and flexibility of the pathogen are afforded by the extensive number of virulence factors it has at its disposal, providing P. aeruginosa with the facility to tailor its response against the different stressors in the environment. https://www.mdpi.com/1422-0067/22/6/3128# FYI Representation of P. aeruginosa adaptation to the cystic fibrosis (CF) lung over the course of infection. In early stages, isolates are fully equipped with virulence factors that allow respiratory tract colonisation and lung injury. The stressful environment of the CF airway drives P. aeruginosa pathoadaptative changes that enable long-term colonisation and establishment of recalcitrant infections. https://www.mdpi.com/1422-0067/22/6/3128# Pseudomonas aeruginosa Virulence Factors and Pathogenesis in CF Lungs Pseudomonas aeruginosa is a Gram negative bacilli/ rod, obligate aerobic bacteria Adhere to epithelial cells, invade and colonize airways (Flagella, pili & secreted virulence factors) Produces Exotoxin A that inhibits host protein synthesis Adhere Invade Exoenzyme S that interferes with phagocytic killing Mucoid exopolysaccharides Phospholipase C that damages the host (Alginate) tissues Pyocyanin that damages tissue by ROS Elastase B enzyme that degrades tissues Alginate that forms a mucoid layer Pyocyanin is a major virulence Factor secreted by Pseudomonas aeruginosa Pyocyanin (PCN) is blue green pigment PCN is essential for P. aeruginosa virulence PCN-deficient P. aeruginosa does not cause infection PCN is important for biofilm development PCN is controlled by quorum sensing process Pyocyanin blue green pigment PCN is cytotoxic redox-active small molecule Increase ROS which damages tissues PCN inhibits catalase; oxidizes glutathione, reduces NADPH thus depletes substrate for NADPH oxidases. Pyocyanin Burkholderia cepacia Complex Burkholderia cepacia is a Gram negative bacilli/ rod, environmental aerobic bacteria Cepa is a Latin word for onion B. cepacia complex is a collection of many strains of Burkholderia species that causes disease in immune suppressed individuals B. cepacia Complex cause fatal necrotizing pneumonia in cystic fibrosis patients “Cepacia syndrome” B. cepacia complex is resistant to antibiotics Burkholderia cepacia Complex There are almost 20 different B. cepacia complex species. The species found most often in people with cystic fibrosis are: B. cenocepacia B. cepacia complex causes fatal B. multivorans cepacia syndrome B. vietnamiensis B. dolosa B. cepacia B. gladioli B. cepacia produces a melanin-like pigment that helps bacteria to evade oxidative killing in the host https://www.slideshare.net/doctorrao/pseudomonas-an-update Burkholderia cepacia Complex in CF B. Cepacia is LPS is more inflammatory, contributing to Cepacia syndrome B. Cepacia produces melanin-like pigment that protect the bug from ROS & facilitate survival in lungs FYI Stenotrophomonas maltophilia Stenotrophomonas maltophila is a Gram negative tiny bacilli/ rod, obligate aerobic bacteria Environmental bacteria that lives in water/ aquatic areas/ wet surfaces. No vaccine is available S. maltophilia causes opportunistic infections in immune suppressed patients including pneumonia and blood stream infections Flagellated motile bacteria S. maltophilia is a common pathogen in cystic fibrosis (previously Pseudomonas maltophilia) S. maltophilia is difficult to treat produces two metalloproteinases thus resistance to antibiotics S. maltophilia produces virulence factors DNAse, lipase, elastase, and hyaluronidase Pigmented colonies Non typable Hib doesn’t have capsule and hence does not have vaccine Hemophilus influenza type B (HiB) “Vaccine preventable infection” Hemophilus influenzae is a Gram negative coccobacilli, fastidious, facultative aerobic bacteria H. influenza causes meningitis, epiglottitis, conjunctivitis, pneumonia, endocarditis, and sinusitis Vaccine is available Vaccine is prepared from the capsule http://slideplayer.com/slide/11324307 Moraxella catarrhalis Moraxella catarrhalis is a Gram negative diplococci, aerobic bacteria M. catarrhalis causes acute purulent exacerbation of chronic bronchitis (common in COPD) M. catarrhalis causes episodes of otitis media and sinusitis but very rarely can cause systemic infection M. catarrhalis adheres to epithelial cells using adhesins M. catarrhalis produces oxidase, DNAse and Blactamase, therefore resistant to penicillin and Blactam antibiotics No vaccine is available Acromobacter xylosoxidans Acromobacter xylosoxidans is a Gram negative rods, aerobic bacteria A. xylosoxidans is an opportunistic pathogen that causes infection in CF and COPD A. xylosoxidans previously named Alcaligenes xylosoxidans (oxidizes xylose) Endophthalmitis A. xylosoxidans causes endophthalmitis, keratoconjunctivitis, catheter-associated bloodstream infection, endocarditis, pneumonia, meningitis, and peritonitis A. xylosoxidans develops resistance to antibiotics No vaccine is available Skin infection caused by multidrug resistant A. xylosoxidans Aspergillus species: Fungal infection Aspergillus species are abundant indoors and outdoors Spores are breathed and cause allergic reactions, infections and invasive disease only in immune compromised people and in chronic obstructive pulmonary disease (COPD) and Cystic Fibrosis Spores Aspergillus nigers Aspergillus terreus Aspergillosis is mainly in lungs but also infect sinuses and skin Aspergillus in tissues Aspergillus fumigatus Aspergillus in tissues Common Pathogens in Early, Late Childhood and adult CF P. aeruginosa How do bacteria adapt to CF lungs environment? Niche modification and bacterial adaptation Long term Pseudomonas aeruginosa Infections and Adaptation in CF Lungs Flagella, pili, T3SS Exotoxins Pyocyanin LPS (modified) Alginate (mucoid) Biofilm Nature Medicine volume 18, pages 509–519 (2012) Pseudomonas aeruginosa Adaptation in CF lungs Mucoid At the chronic stage of infection, P. aeruginosa is fully adapted to CF environment and exhibits overproduction of alginate, are resistant to antibiotics (expression of efflux pumps), and adapted metabolism. Antibiotic resistance Biofilm Formation in CF lungs Biofilm is a highly complex structure of bacterial growth on living or nonliving surfaces where bacteria adhere to each to form communities within a self-produced matrix (slime). This matrix consists of extracellular polysaccharides (EPS), proteins, DNA and water which is the major part of biofilm responsible for the flow of nutrients inside biofilm matrix. Bacterial biofilms are infectious in nature and can results in nosocomial infections. Biofilm formation increases antibiotic resistance Biofilm Formation in CF Lungs The formation of biofilms in CF airways by Pseudomonas aeruginosa, are associated with a worse clinical outcome. Biofilms are very difficult to eradicate due to their complex matrix and EPS that resist host defenses. Moreover, bacteria adapt to biofilm environment by changing its genetic and phenotypic characteristics including resistance to antibiotic therapy. Biofilms in CF airways are major contributor to reduced antibiotic activity and associate with increased frequency of pulmonary exacerbations Pulmonary Exacerbations Associate with Lung Function Decline Frequency of pulmonary exacerbation reduces survival Frequency of pulmonary exacerbation reduces quality of life Life Expectancy in Cystic Fibrosis https://www.frontiersin.org/articles/10.3389/fphar.2016.00275/full AI in Medicine Applications Digital Stethoscope for Lung Auscultation Recorded lung sounds, breath, and cough sounds can be used in Machine learning algorithms/Apps to assist in decision making and patient monitoring. Lung auscultation positions AI-enabled digital stethoscope in Healthcare based and Telemedicine applications Reading material Your Microbiology text books such as Murray & others Harrison's Principles of Internal Medicine, 19e Chapter 313: Cystic Fibrosis https://www.ecfs.eu/ https://www.cff.org/ https://www.uptodate.com/contents/cystic-fibrosis-overview-of-the-treatment-of-lungdisease?search=Cystic%20fibrosis&source=search_result&selectedTitle=2~150&usage_ty pe=default&display_rank=2 Clinical manifestations in Cystic Fibrosis FYI Pathophysiology of CFTR mutation Airway surface liquid Figure 1 Normally functioning CFTR determines airway surface fluid depth by regulating Cl − (and bicarbonate) secretion and Na + reabsorption (the latter indirectly through its influence on the epithelial Na channel [ENaC]). Notes: (A-C) CFTR dysfunction and the resulting abnormalities in ion transport lead to reduced airway surface fluid and pH, inhibiting mucociliary clearance and innate defenses to lead to chronic infection, and concentrating inflammatory mediators at the epithelial surface. DOI: 10.2147/TCRM.S147164 ChatGPT summary of virulence factors for CF pathogens FYI Prompt: Summarize virulence factors of the main pathogens causing CF lung disease The main pathogens associated with CF lung disease, their virulence factors and effects on the lung tissue are summarized below: Pseudomonas aeruginosa: This pathogen is able to form biofilms, which protect it from the host immune response and antibiotics. It produces toxins, including pyocyanin and exotoxin A, which contribute to inflammation and tissue damage in the lungs. P. aeruginosa also produces elastase, an enzyme that can break down lung tissue, leading to chronic lung damage, and alginate that contribute to infection persistence and enhance biofilm formation. Staphylococcus aureus: S. aureus produces a range of virulence factors, including toxins, enzymes, and surface proteins that help it evade the host immune response. It produces a protein called protein A that binds to antibodies, preventing them from opsonizing the bacteria and facilitating immune evasion. S. aureus also produces a variety of enzymes, including coagulase, lipase and protease that contribute to tissue damage. Burkholderia cepacia complex: This group of bacteria produces a range of virulence factors, including toxins and enzymes that contribute to tissue damage and inflammation. It also produces siderophores, which help it scavenge iron from the host, promoting bacterial growth. Haemophilus influenzae: H. influenzae produces a variety of virulence factors, including adhesins and lipooligosaccharides, which help it adhere to host cells and evade the host immune response. It also produces a enzyme called IgA protease, which can cleave immunoglobulin A (IgA), an important component of the host immune response. Aspergillus fumigatus: A. fumigatus produces a variety of virulence factors, including gliotoxin and other secondary metabolites, that can induce inflammation and tissue damage in the lungs. It can also produce allergens that can trigger an immune response in susceptible individuals.