Block 9 Week 2 Flashcards
Narrow spectrum antibiotic examples
Macrolides like erythromycin which targets the large ribosomal subunit and older penicillin such as benzylpenicillin
Sulfa drugs
Non antibiotic micrboial drugs which taret the folate synthesis pathway
Target of quinolone
DNA gyrase
What is DNA gyrase?
Enzyme for supercoiling of DNA for replicatio and transcription
Clostridium dificile
Anaerobic gram negative bacteria with spores. It is a commensal bacteria at low levels butin excess causes pseudomembranous colitis
When does innate resistance occur?
Bacteria lack suitable target or become impermeable to the drug
What are the issues with broad spectrum antibiotics?
Resistance of bacteria
What affects the microbiome-host relationship?
Diet, nutritional state and stress
Broad spectrum antibiotics
Aminoglycosides, quinolones, cephalosporins and synthetic pencillin
Tetracyclines
Targets both eukaryotic and prokaryotic of bacteriostatic 30s inhibitors
Bacteria found in the upper respiratory tract
Staphylcoccus pneumoniae, haemophilius influenzae, staphylcoccus epididermis, staphylcoccus aureus
Pneumonia
Infection of the lung tissues that results in inflammation where the alveoli fill with fluid/pus, causing pulomonary consolidation and results in respiratory distress. Nasopharyngeal colonisation is a prerequisite for the disease.
Pneumonia causes
Influenza virus or bacterial causative agent is staphylococcus aurea, streptococcus pneumoniae and haemophilius influenzae. There are normally defences in the upper respiratory tract such as the nostrils, mucociliary escalator and the alveolar macrophages, and commensal bacteria that prevent this occurring.
How is pneumonia acquired?
- Community acquired pneumonia is the most common type acquired outside of the hospital, caused by bacteria, viral and fungi.
- Hospital acquired pneumonia is acquired through biofilm present on ventilators and fungi.
- Aspiration pneumonia: inhaling a foreign object such as food or liquid which enters the airways causes the lung tissues to become inflamed. It occurs more in the right lung because it has greater lung capacity than the left lung.
Risk factors for pneumonia
Immunocompromised groups such as elderly and the very young
Frequent exposure to asbestos and cigarette smoke
Poor sanitation
Viral cause of pneumonia
Influenza virus can cause pneumonia because it weakens the immune system which increases susceptibility to infection by already present bacteria in the upper URT.
Pneumococcus pathogen
Pneumococcus is a gram positive cocci extracellular anaerobic bacteria with a peptidoglycan thick cell wall with lipoteichoic acid. It is absent in catalase enzyme for H202 -> H20 and O2. It is alpha haemolytic which means it partially breaks down RBC. Streptococcus pneumoniae is sensitive to bile
Why is catalase important?
Catalase is important to bacteria because it provides protection against damage from the host defence signalling molecule hydrogen peroxide.
Effects of pneumococcus
It inhibits the oxidative burst by neutrophils and induces activation of the classical-complement pathway. it releases the virulence factor pneumolysin to bind to cholesterol of endothelial cells and cause a pore to form. It causes partial breakdown of RBC.
What type of bacteria is pneumococcus?
Streptococcus is a fastidious bacteria and the target is the alveoli have nutrient rich fluid. This causes inflammation, leading to fluid build up/pulmonary consolidation. If it enters the bloodstream, it can travel to the brain and result in meningitis.
Ve+ bacteria
Gram + has thick peptidoglycan cell wall with teichoic acid. It is divided into cocci and bacilli. Cell membrane is below the cell wall.
What is teichoic acid?
Teichoic acid binds to fibronectin on endothelial cells for host colonisation. for hydrophobicity and maintaining structure.
Ve- bacteria
Outer membrane of lipopolysaccharide containing endotoxins such as polysaccharide O which maintains membrane integrity. It has a thin cell wall of peptidoglycan. It contains a periplasmic space between inner membrane and peptidoglycan cell wall.
What is the role of IL-1?
Acute inflammatory mediators
What is the role of TNF?
Recruiting WBC and activating endothelium
Meningitis
Caused by pneumococcus meningitis bacteria crossing the blood brain barrier through the release of the virulence factor pneumolysin. This results in the inflammation of the brain and spinal cord meningeal layers.
Meningitis symptoms
Fever, chills, hearing loss, vision loss, photosensitivity
Neisseria Meningitidis
Gram negative bacterium which causes meningitis in older children and adults commonly.
What is the most common cause of community acquired pneumonia?
Streptococcus pneumoniae which becomes pathogenic when immunosuppression occurs
What is the most common cause of pneumonia in infants?
Streptococcus agalctaei which is gram positive transmitted during birth
Macrolide
Bind to the P site of the subunit of the 50s ribosomal subunit. This prevents peptidyltransferase allowing attachment between peptide and another amino acid on tRNA.
Why has antibiotic resistance occurred?
Increased global availability, uncontrolled sale in low/middle income countries
During pharmaceutical manufacturing, antibiotic is released into environment
What is the choroid plexus?
Network of blood vessels in the brain which produce CSF
Which space is affected by meningitis?
Bacteria enter the subarachnoid space where the blood-brain barrier is vulnerable in the choroid plexus. Due to the immune response of inflammation, causes oedema of the brain called vasogenic cerebral oedema.
Which immune cells are present in the brain?
Astrocytes and microglia
What is the effect of meningitis on the brain?
Vasogenic cerebral oedema, cerebral vasculitis which reduces blood flow to the brain which both decreases BP and increases intracranial pressure, leading to brain cell apoptosis
What is the common bacterial cause of meningitis in infants?
E.Coli, listeria monocytogenes and Streptococcus agalactiae
What is the common bacterial cause of meningitis in children?
Streptococcus pneumonia, neisseria meningitidis
What is the common bacterial cause of meningitis in adult?
Streptococcus pneumonia, neisseria meningitidis, listeria monocytogenes
What are the viral causes of pneumonia?
Enterovirus, herpes and its subtype varicella zoster virus, HIV, mumps
How is meningitis transmitted?
Respiratory secretions from close contact only, not simply breathing the air near a person
What are the vaccinations for meningitis?
Pneumococcal vaccine, MenB, MMR.
What is the target of first gen cephalosporins?
Inhibiting cell wall synthesis of gram positive bacteria
What is the target of second gen cephalosporins?
Inhibiting cell wall synthesis of gram negative bacteria
Side effects of tetracyclines
Photosensitivity
