Chapter 70: Basic Principles in Antimicrobial Flashcards
2017 LRI deaths
2.56 million
4th leading cause of death
selective toxicity
most important concept underlying antimicrobial therapy
selective inhibition of the growth of the microorganisms without damage to the host. the drug must be more toxic to a pathogen than a pathogens host
this is possible due to difference in structure or metabolism between pathogen and the host
3 main MOA of AB
inhibit cell wall synthesis or function
beta lactams: PCN, cephlosporins, carbapenems, monobactams, vancomycin, daptomycin, polypeptides
inhibit nucleic acid synthesis or function
inhibit DNA gyrase: topoisomerase, IV quinolones
inhibits folate synthesis: Bactrim
create free radials: metronidazole, nitrofurantoin
inhibit protein synthesis:
inhibit 50s subunit: macrolides, clindamycin, linezolid, streptogramins, chloramphenicol
inhibit 30s subunit: aminoglycosides, tetracycline, tigercycline
classifications of AB
based on MOA: bacteriostatic or bactericidal
based on spectrum: broad spectrum (work on larger group of bacteria) or narrow spectrum (work on limited group of bacteria)
broad can kill more of natural flora. often start patient on broad AB, then get C/S, then switch to NS AB -helps with AB resistance and less SE.
bacteriostatic
inhibits bacteria from reproducing, but does not otherwise kill them
bactericidal
actively kills bacteria
fast killing
note on bacteriostatic vs bactericidal
In reality there is not a sharp distinction between the two, as categorization depends upon drug concentration and bacterial species
narrow spectrum AB
act on a single, limit group of micro-organisms
ex. isoniazid given for mycobacterium
extended-spectrum AB
effective against gram + organisms and a significant number of gram - organism
ex. ampicillin
broad-spectrum AB
effective against a wide variety of microbial species
ex. tetracycline and chloramphenicol
can alter the nature of intestinal flora = super infection
microbes
Bacteria
Virus
Fungus
Parasites
Helminth
Protozoa
shapes of bacteria
cocci -tend to be gram +. staph & strep
bacilli (rods) -tend to be gram -.
vibrios, spirilla, spirochetes
can form spores or have flagella
gram stain
Determines gram + or gram -, helps determine what AB needed
Gram + has thick peptidoglycan wall –absorbs dye
Gram – has thin PG wall –does not absorb dye. Also has outer membrane. Hard to treat bc of outer membrane.
gram +
Thick peptidoglycan cell wall
Examples
Streptococcus
Staphylococcus
Enterococcus
Clostridium
Listeria
gram -
Outer plasma membrane with very thin peptidoglycan wall.
Examples
Neisseria
Moraxella
E Coli *
Klebsiella *
Enterobacter
Serratia
Citrobacter
Bordetella
Pseudomonas *
Proteus
Helicobacter *
Campylobacter
Salmonella
Shigella
Anaerobes
Anaerobes include all bacteria which grow and reproduce only in the absence of oxygen
The are predominately found in the GI tract (Including the oral cavity)*
Play a role in appendicitis, diverticulitis, aspiration pneumonias
While they are generally stainable via gram stain, they are rarely referred to as gram positive or negative in clinical practice
Examples
Clostridium
Bacteroides
Peptostreptococcus
Actinomyces
Fusobacterium
atypical bacteria
An inexact term applied to bacteria which are particularly unusual in cellular structure, morphology, biochemistry, or life cycle.
No cell wall
Examples
Mycoplasma
Chlamydia
Rickettsia
Legionella
atypical penumonia usually is caused by the influenza virus, mycoplasma, chlamydia, legionella, adenovirus, or other unidentified microorganism
typical penumonia
typical pneumonia usually is caused by bacteria such as streptococcus penumoniae
differentiating factor between typical and atypical
pt age
young adults are more prone to atypical causes
very young and older people are more predisposed to typical causes
antibiotics resistance
Develops with misuse of AB
Killing off weak bacteria and small % of strong survive. (95%/ 5%). Natural selection. These strong bacteria pass the trait to the offspring = resistant generation.
mechanism: both drug resistance and non-resistance bacteria exist in body -> pt takes Ab -> non resistant bacteria die. drug resistant AB take over -> thru replication and gene transfer, drug resistant bacteria can dominant and a new infection can occur
Teach:
Take AB only for infection. Not viruses. Build resistance.
Take entire prescription. Even when u feel better.
Don’t share BC u need the
Right AB!!
common SE of AB
- Hypersensitivity
mild- allergy -Benadyrl
anaphylactic shock -Epinepherine
Watch first dose! - GI-N/V D. Abdominal pain/ Liver tox
- CNS- confusion, headache
any AB that cross BBB
elderly at risk - Nephrotoxicity
AB in general
take full glass of water with AB - Secondary Infections ( 2 types)
C diff, Candidiasis “super infection “ opportunistic when normal flora is destroy by AB. Can happen during and after therapy.
Bacterial Infection after a viral infection
antimicrobial stewardship
enhancing infection prevention and control
controlling the source of infection
prescribing AB when they are truly needed
prescribing appropriate AB with adequate dosage
using the shortest duration of AB based on evidence
reassessing tx when culture results are back
supporting surveillance of AMR and HAIs and monitoring Ab consumption
educating staff
supporting an interdisciplinary approach
3 principles for the selection of AB
Identify the affecting organism
Match the drug with the Bug
Gram Stain
PCR Testing (polymerase chain reaction)
Drug Sensitivity of the infecting organism
Determine Drug Sensitivity
Host Factors such as the site of infection and the status of the host defenses
Host Defenses
Site of infection
Allergies
others
General Sites of Infection by Bacteria Type
Gram Positive Cocci → Skin, soft tissue, heart, lungs, bone, joint, hardware, indwelling lines
Gram Negative Rods → Lung (HCAP, HAP, VAP), any intraabdominal organ, GU System
Anaerobes → Lung (abscess), oral cavity, intraabdominal organ
Atypicals → Lung (CAP)
Most Common Broad Spectrum
Gram + AB
Vancomycin (bactericidal for severe bacterial infections(sepsis, pneumonia, endocarditis);C diff)
Tx of choice for HA MRSA
Gram – AB
Zosyn (piperacillin/tazobactam)
Bactericidal, piperacillin inhibits cell wall synthesis. Tazobactam added d/t resistance of PCN)
Including psueodmonas
Prophylactic Use of Antibiotics
Estimates indicate that between 30% and 50% of the antibiotics used in the US are administered for prophylaxis.
Surgery
Bacterial Endocarditis
Do not do as much as we used to
Neutropenia
Recurrent UTI’s
misuse of AB
Common
1/3 outpatient AB prescribed are either inappropriate or unnecessary
Treatment of Viral Infection
Treatment of Fever with unknown Origin
Improper Dosage
