Diagnosis And Control Of Infection Flashcards
What affects spread of infection
Reservoirs and modes of transmission
What are reservoirs? Types of reservoirs
Habitat in which infectious agent lives/grows/multiplies, transmitted to host from here
Human
Animal (zoonotic disease spreads between human and animal)
Non living
What are emerging diseases? What can they be caused by
Unrecognised or previously recognised infection-> spread to new ecological niche-> significant change in pathogenicity
Caused by newly identified species/newly identified strains that have evolved from known infection/ecological changes that have changed size and composition of reservoirs/re-emerging infections/nocosmial infections
Types of disease transmission
Contact
Indirect
Horizontal
Types of contact transmission and their characteristics
Direct contact: touching/kissing/no intermediate object eg smallpox
Indirect contact: transferred by intermediate object eg herpes
Droplet: mucous droplets that travel short distances eg influenza
Types of indirect transmission and their characteristics
Vehicle: requiring a medium like food/air/water; can be waterborne/airborne(bacterial/fungal spores)/foodborne eg salmonella
Vector: via hosts; can be mechanical (passive transport of pathogens ON vectors body) or biological (pathogen spends lifecycle IN vector, transmission through a bite)
Horizontal/vertical transmission characteristics
Vertical: Mother to child
Horizontal: person to person
How are infections diagnosed and confirmed in a lab?
Direct detection: clinical specimen has microbes/its products Indirect detection (serological): blood/body fluids have antibodies against pathogen
4 examples of direct methods of detection of pathogens
Bacterial culture: types of medium include (defined medium-composition known; enrichment medium-has component that permits growth of specific bacterium; selective medium- supports growth of specific orgs while inhibiting growth of others; differential medium- distinguished closely related org by diff in colony apprentice)
Viral culture: host cells are PERMISSIVE; MOI- number of virions added per cell; virus infected cells-> dramatic change in appearance eg cell rounding/surface detachment/syncythia/inclusion bodies
Microscopy: morphology and staining
Nucleus acid detection: test presence of bacterial/viral DNA
Example of indirect method, what happens here
Serological tests determine presence of antibodies
Title refers to [antibody] in sample: number of times one can dilute sample and still detect antibody
Paired sera samples of igM and igG collected during acute phase (within a week) and convalescence phase (2-4 weeks)
At least 4 fold rise between and acute and convalescent sample-> diagnosis
Only IgM found in current active infection
What is selective toxicity, how is it achieved
Inhibit microbial growth while doing minimal damage to pt
Exploit diff between metabolism and structure of microorganisms
How are antibacterial agents classified
Bactericidal/bacteriostatic (inhibit bacterial growth)
Broad spectrum/narrow spectrum
Chemical structure and site of action: inhibit Cw synthesis/bacterial pm function/inhibit nuclei acids synthesis/inhibits synthesis of proteins
Targets of antibacterial agents
Cell wall: target peptidoglycans
Cell membrane: disrupt membrane potential/target LPS in gram -ve bact
Nucleic acid synthesis: block bacterial enzymes/metabolic pathways needed for synthesis
Protein synthesis: ribosomal proteins/RNA/ enzymes
Targets and actions of antiviral agents
Attachment and entry: inhibit fusion of viral envelope or attachment to receptor
Nucleic acid synthesis: DNA/RNA polymerase
Assembly and budding: inhibit viral proteins needed for virion maturation and release
Forms of bacterial resistance strategies
Reduce drug’s ability to penetrate cell
Inactivate drug via modification/degradation
Efflux pumps
Modify drug’s target site
