Antimicrobial Resistance Flashcards
Antimicrobials & resistance (tendency)
MRSA
-What is driving resistance (6)
- As soon as antimicrobial deployed, resistance starts developing
- MRSA = Methicillin resistance staphlyococcus aureus
- Factors driving resistance;
- Over prescribing
- use for viral infections
- consumer demand
- use for viral infections
- use with no prescription
- over flooding of cheap generic drugs in developing countries (not as strong therefore give bacteria time to develop resistance)
Drugs that came out between 1930 and 1970s
- Sulfonamides
- Penicillin
- Streptomycin
- Chloramphenicol
- Tetracycline
- Trythromycin
- Vancomycin
- Cephalosporins
Drugs that came out recently (after 1980s)
- Linezod (2000)
- Daptomycin (2004)
Antibiotic
Antimicrobial
Chemotherapy
*Definitions
- Antibiotic: Substance produced or derived from living organism that can destroy or inhibit growth of other microorganisms (e.g. penicillin)
- Antimicrobial: Chemical agents capable of destroying or inhibiting growth of microorganism (an be made in the lab -> covers everything)
- Chemotherapy: Use of chemical agents to treat or control disease
e. g. antibacerial, antiviral, antiparasitic, antifungal
Definition of drug resistance
- Medicines for treating infection loses its efficicay due to the mutation or acquisition of resistance genes
- find it in nature too (bacteria grows in presence of fungi in enviro (therefore has resistance))
Development of antimicrobial resistance
- Lots of germs, few are resistant
- Antimicrobials kill bacteria causing the illness (as well as the good bacteria that protects the body from infection)
- Some drug resistant bacteria survive, now allowed to grow
- Causes more problems
Drug classes and level of importance
- Low importance (resistance widespread)
e. g. amoxycillin, erythromycin, penicillin, tetracyclines, neomycin - Medium importance;
- e.g. 2nd generation cephalosporins, gentamycin/Tobramiun, spectinomycin
- High importance (are critical -> need to preserve these as after these there are none)
- e.g. 3rd & 4th generation cephalosporins, carbapenems, fluoroquinodones
Types of bacteria;
- Wild Type
- Multidrug Resistant
- Extremely drug resistant
- Pandrug resistant
Wild type: Sensitive to all antimicrobials
MDR: resistant to 3 or more classes
XDR: resistant to most antimicrobials
PDR: Resistance to all antimicrobial agents
S. aureus
- Common widespread
- approximately 1/3 of population
- major human pathogen associate w/ variety of diseases (can be minor skin infection or serious post-surgery infection)
- typically resistant to penicillin
- SCCmec = transposable element that gives them resistant to mec and other beta lactams)
- is really a huge complex of clones
What is a clone?
Clone = bacteria that share a core genome, they are almost similar but with small variations
-belong to same multilocus sequence type
Multilocal sequence typing
- Is the gold standard
- 7 alleles that typically stable in bacterial genome are sequenced (“housekeeping” genes)
- sequence type = ST
- clone complex = CC
- ST5 and ST8 are huge clones
Health Care associated MRSA
- features
- where found
- Often multi-resistant -> very difficult to treat and some are untreatable
- most frequently found in patients undergoing invasive procedures (i.e. surgery)
- can be carried by patient or by healthcare workers
- most common hospital acquired infection
- also most commonly found on the nose
- in hospitals, major outbreaks are associated with certain clones
Staph aureus -features
-evolution as it jumps hosts
- excellent in jumping hosts
- can spread to pigs
- ST398 is actually a methyline sensitive organism
- phage goes into staph aureus, makes it more virulent
- then bacteria can pick up mecc gene in pigs, but loses its human evasion (evolves in hosts)
- phage goes into staph aureus, makes it more virulent
- transmission via direct contact w/ animals, enviro contamination and eating or handling contaminated meat
E. coli - features
-Lactose positive
-gram negative
facaultive aerobe
*normally part of commensal GI tract microbiota, but bad strains can cause diarrhoea; ugly strains can cause UTI and meningitis
