Basic Principles of Anti-infective Pharmacology Flashcards
Pathogens
microbes that can cause disease
Pathogenicity
qualitative ability of organism to cause disease, to infect organisms and to evade host defences
Virulence
quantitative measure of organism’s pathogenicity
Invasiveness
ability to grow rapidly and to cause damage to surrounding tissue
Production of toxins
toxins stimulate development of disease, main elements of pathogenicity
Exotoxins
proteins released by bacteria that inactivate or kill host cells
Endotoxins
non-protein released from cell wall of Gram-negative bacteria that elicit immune responses (cause macrophages to release cytokines leading to fever, inflammation and chills)
Classifying Bacteria: By staining properties
- gram positive - stay positive
- gram negative
Classifying Bacteria: by shape
- rod-shaped - bacillus
- spherical - coccus
- spiral
Classifying Bacteria: by ability to use oxygen
- Aerobic - thrive in O2 rich environment
- Anaerobic - do not require O2 to survive
Anti-Infectives
Drug that is effective against pathogens
Classification of Anti-Infectives
- susceptible organism (antibiotic, antiviral, antifungal, antiprotozoan)
- chemical structure of drug
- mechanism (bacteriocidal, bacteriostatic - inhibiting the bacterial protein synthesis pathways)
Mechanisms of Antibacterial Agents
- drugs that damage bacterial cell wall (beta-lactam antibiotics synthesis of bacterial cell wall; tend to be bacteriocidal)
- drugs that damage cell membrane
- drugs that inhibit protein synthesis
- Drugs that inhibit DNA replication or bacterial cell division
Acquired Resistance
- ability of organism to become insensitive to effects of anti-infective
- major clinical problem, worsened by improper use or anti-infectives
Mechanisms of Resistane
- pathogen destroys drug
- pathogen prevents drug entry or pumps drug out of itself
- pathogen alters target site of drug or undergoes mutation or adapts to drug
Bacteria change physiology to become resistant by:
- replicating rapidly
- mutating spontaneously and randomly
- acquiring resistance and promoting resistance to other bacteria via conjugation (transfer of small pieces of DNA called plasmids that contain resistance promoting gene)
Guidelines to help prevent resistant strains from developing
- preventing infections when possible
- diagnosing and treating the infection properly and specifically by identifying the bacteria
- limiting use of antibiotics where possible
- preventing the transmission of infections
Four main sources for spreading of HAIs
- patients flora
- invasive devices (catheters or endoscopes)
- medical personnel
- medical environment
Methicillin-resistant Staphylococcus aureus (MRSA)
- resistant to certain antibiotics
- at least 60% of MRSA infections resistant to penicillin
- most often acquired in hospital
- usually occurs in patients with weakened immune systems
- therapy options are limited
Vancomycin-resistant Enterococci (VRE)
- found in wounds and pressure ulcers in hospitals and nursing homes
- patients with weakened immune systems at most risk
use of correct antibiotic is key to effective treatment
- where possible, use testing culture and sensitivity to identify the organism, and then the appropriate antibiotic
- if not possible to do C&S begin with broad spectrum antibiotic then use a narrow-spectrum antibiotic
Guidelines for Antibiotic Therapy
- anitbiotics should not be used for viral infections or for cough
- if infection caused by one microbe, treatment with a single drug is usually best (combining antibiotics can decrease their effectiveness and promote resistant strains)
- Antibiotics are sometimes given (to prevent secondary infections, prophylactically for some surgeries, for patients with damaged heart valves)
Patient factors affect choice of anti-infective
- determine the hosts defences and immune system status
- local tissue conditions
- knowing patients allergy history and drug hypersensitivity
- pregnancy, age, and genetics
Superinfections
develop when host flora is damaged by antibiotic as nutrients and space become available for pathogens to grow
