9.1 Infection and Antimicrobials Flashcards
Normal Microbial Flora
- Protect host by occupying space and consuming nutrients inhibiting pathogens from proliferation
- Pathogens thrive if normal flora is supresssed
Antibiotic Therapy
- Necessary when host defense mechanisms are not adequate to ward off infection
- 1/3 - 1/2 hospitalized patients are treated with antimicrobials
- Used to treat/prevent infections caused by pathogens
Antimicrobial/Antibiotic
Antibiotic - Produced from one microbe that has the ability to harm other microbes.
Antimicrobial - Any agent capable of suppressing or killing microorganisms.
Chemotherapy - Use of chemical agents against invading organisms.
Antibacterial Drugs
- Can be broad or narrow spectrum
- Classified by kinds of organisms they are effective against
Antibacterial
- Bacterial infections
staphylococcus, streptococcus, gonorrhea
Antiviral
- Used for viral infections
Chicken pox, influenza, HIV
Antifungal
Used for fungal infections
Athletes foot, oral thrush, vaginal yeast, mucormycotic
Antiprotozoal
- Used for protozoal infections (parasite)
Malaria, amoebic dysentery
Anthelminthic Agent
Parasitic Infections
Tape worm, schistosomiasis
Antimicrobial Drug Classifications
- They are classified by their mechanism of action or what part of the target the drug acts on
Ribosome
Aminoglycosides, Macrolides, Ketolides, Tetracyclines, Linezolid, and Quinupristin/Dalfopristin
These drugs bind to ribosomes and inhibit production of essential proteins (Inhibition of Protein Synthesis)
Aminoglycosides (lethal)
Tetracyclines (non-lethal)
DNA
Fluoroquinolones - Inhibit DNA gyrase, enzyme required for reproduction (Inhibition of Nucleic Acid Synthesis)
- Inhibits DNA/RNA synthesis which affects transcription and replication of the bacteria.
Cell Wall
Penicillin, cephalosporin, vancomycin
- Inhibit formation of cell wall (inhibition of bacterial cell wall synthesis)
- Drugs produce defective cell wall which destroys microorganism.
- Fluid is drawn into cell until cell bursts.
- Immune system cleans debris and fights remaining infection.
- Works best when cell is replicating
Cell Membrane
- Inhibition of viral replication and disruption of cell wall permeability
- Inhibition of viral replication prevents virus entry into host cell
- Polymyxins disrupt cell wall permeability by binding to lipopolysaccharides.
Folic Acid
Sulfonamides block synthesis of components necessary for cell metabolism and growth
(Inhibition of metabolic pathways (Antimetabolites))
- Inhibition of folic acid and synthesis, which is essential for survival of pathogen.
- Human cells don’t need this because they get folic acid through dietary resources
Bacteriostatic Drugs
INHIBITS BACTERIA
- Reversible if drug is removed unless host mechanisms have eradicated the organism
- Sulfonamides, erythromycin, tetracyclines
Bactericidal Drugs
Antibiotics that kill bacteria
- Less dependence on bodies defense mechanisms.
- Penicillin, cephalosporins, aminoglycosides.
Selective Toxicity
- Ability to suppress/kill infecting microbe without injury to host.
- Achievable because cellular chemistry of mammals and microbes differ
- Disruption of cell walls, inhibition of enzymes unique to bacteria, disruption of bacterial protein synthesis.
Antimicrobial Resistance
- Pathogens change over time and stop responding to medications
- Infections caused by resistant pathogens require more toxic and expensive medications.
- Microbes acquire resistance through spontaneous mutations / random changes in microbial DNA transferred from 1 bacteria to another.
- Bodies normal flora can contribute to this.
Antimicrobial Resistance
- The more antibiotics used, the faster drug resistant microbes emerge.
- They grow and multiply while normal flora are suppressed by antimicrobials
- They emerge during or after broad spectrum therapy that suppress normal flora
- Interruption/inadequate use of antimicrobial treatment also promote this.
- Education is important to use antimicrobials exactly as ordered
Antibiotic Resistant Microbes
- Methicillin-Resistant Staphylococcus Aureus (MRSA)
- Penicillin-Resistant Streptococcus Pneumoniae
- Vancomycin-Resistant Enterococci (VRE)
- Multi-drug Resistant Enterococci (MDR-TB)
- Extensively Drug-Resistant TB (XDR-TB)
- Enterococcus Faecalis and Faecium
- Clostridium Difficile (C-Diff)
SuperInfection
- Occurs during or after treatment of earlier infection, especially infection treated with broad spectrum antibiotics.
- Usually caused by drug resistant microbes
- CDIFF, MRSA, Oral/Vaginal Candida Infection
Prevention of Antimicrobial Resistance
- Vaccinations - Prevent infection in the first place
- Remove Catheters (Indwelling such as urinary and IV)
- Target the pathogen (obtain cultures and sensitivities to identify the bacteria and target the specific bacteria)
- Use infectious disease experts to guide treatment
Use antimicrobials wisely
- Practice antimicrobial control
- Use local data
- Treat infection not contamination
(Infection is presence of pathogen, Contamination is unintended infectious material into area) - Treat infection not colonization
(Presence of pathogen without illness or symptoms) - Know when to say no to Vanco
(Vancomycin - attacks gram positive bacteria. Limit use if there is no evidence of gram positive bacteria) - Stop treatment when infection is cured or unlikely to be cured
Prevent Transmission
Isolate Pathogen - Standard precautions and isolation
Break chain of contagion - Wash Hands, appropriate PPE
Infectious Disease
- Presence of pathogens and clinical signs/symptoms
- Spread via direct contact or contaminated hands, food, water and objects
Opportunistic Pathogens
- Caused by normal flora that are non-pathogenic however become pathogenic with impaired defense mechanisms
- Situations include burns, cancer, HIV, indwelling IV/catheter, patients with antibiotics, corticosteroid therapy
- Bacterial infections are serious and can be life threatening.
Antimicrobial Therapy Principles
- Goal is to eliminate causative microorganism and return patient to full health
- Antimicrobials are the most frequent used medication worldwide
- Overuse leads to adverse effects, increased cost, increased drug resistant drugs, multi drug resistant infections
Therapy Use Guidelines
- Use older, cost-effective drug if it meets criteria
- Combination therapy of antimicrobials to treat infections caused by multiple microbes nosocomial infections, and serious infections
- May be given orally or IV dependent on patients condition, location, severity of infection, patients ability to take oral medication
Considerations when selecting Antimicrobial
- Match the drug with the bug.
- Initial therapy of severe infections provide wide coverage,
- Prophylactic use of antimicrobials 30-50% of use. Prevents infection before it happens.
Common Misuse of Antimicrobials
- Untreatable infections (colds, chicken pox, mumps)
- Improper dosage
- Treatment without adequate microbe information except in life threatening conditions
Monitoring Antimicrobial Therapy
- Monitor serum peak and trough levels. Hepatic and Renal Function, CBC,
- Duration of therapy depends on reason for use. Prophylaxis may be single dose,
- Acute infection may be 7-10 days or until patient is afebrile and asymptomatic for 48-72 hours
Beta-Lactum Antibacterials
- Work by inhibiting synthesis of bacterial wall
- Penicillin, Cephalosporins, Monobactams
Bacteria
- Cell walls and membranes either gram positive or gram negative
- Aerobic, Anaerobic, Facultative (adaptive)
Cocci - Round
Bacilli - Rod
Spirochetes - Corkscrew shaped
Adaptive mechanism of bacteria
- Some create mucous membranes or capsules that discourage phagocytosis by host WBC’s.
- Some secrete toxins which damage host neutrophils and macrophages
- Can survive and reproduce within phagocytes
- Enzymes that allow bacteria to escape detection
Fungal Infections
2 types - Yeast and Mold
Yeast - Single celled organism and mold with long, hollow branching filaments called hyphae
Fungi - Produce disease in humans only if they grow at temperature of infected body.
Yeast is usually on skin, mucous membranes, GI tract
Select Opportunistic Fungal Infections
Aspergillosis - Found in soil, water, decaying vegetation. Airborne
Candidiasis - Yeast like fungus almost always present in mouth, skin, intestines, vagina
Cryptococcosis - Most serious fungal infection in immunocompromised patients.
Mucormycotic - Infection in sinuses, brain, lungs, caused by Mucor or Rhizopus
Non-Opportunistic Fungal Infection
Blastomycosis - Chronic infection characterized by granulomatous and suppurative lesions
Coccidioidomycosis - Primary disease of lungs, common in southwest US and northwest Mexico
Dermatophytic Infection - Ringworm/Tinea caused by mold like fungi called dermatophytes.
Histoplasmosis - Fungal infection that effects lungs or other organs of dissemination. Acquired by breathing in fungal spores.
Virus
- Genetic material inside protein coating
- Cannot reproduce without assistance of host
- Insert genetic material into host and utilize human cell to reproduce viral particles
- Antiviral drugs inhibit viral reproduction but do not eliminate virus from tissues.
- Difficult to suppress viral replication without significantly harming host
- Suppress biochemical process unique to viral reproduction.
