Antibiotic Resistance in Clinical Microbiology

Define antibiotic resistance.

failure of a bacterial strain to be growth-inhibited by a clinically relevant level of a specific antibiotic.

Define antibiotic breakpoint.

those concentrations (MICs) that separate strains where there is a high likelihood of treatment success from those bacteria where treatment is more likely to fail

How are antibiotic breakpoints determined?

based on MIC but are only determined for “problem” cases and most testing is done via disc diffusion. Current breakpoints take PK/PD into account.

How is antibiotic resistance spread?

dissemination of resistant strains or genes (such as plasmids or transposable elements), multiple points of mutational origin

What are beta-lactam antibiotics?

Beta-lactam antibiotics are a large class of antibiotics characterized by the presence of a beta-lactam ring in their chemical structure. They work by inhibiting bacterial cell wall synthesis, specifically targeting enzymes called penicillin-binding proteins (PBPs) that are involved in cross-linking peptidoglycans. This disruption of cell wall integrity leads to cell lysis and death of the bacterial cells. 

Give examples of beta-lactam antibiotics.

penicillin, cephalosporin, monobactam, carnapenem

What are beta lactamases?

enzymes produced by some bacteria that hydrolyse beta-lactam antibiotics

Give examples of B-lactamases?

penicillinases, cephalosporinases, extended spectrum B-lactamases (ESBL), carbapenemase

What are extended spectrum B-lactamases (ESBL)?

enzymes produced by certain bacteria that make them resistant to many common antibiotics, including penicillins and cephalosporins

What are ESBLs susceptible to?

B-lactamase inhibitors such as clavulanate sulbactam and tazobactam

What is the confirmatory method for antibiotic resistant?

combination disk using 2 disks of cephalosporin alone and combined with clavulanic acid.

How to prevent antibiotic resistance?

Implement appropriate prescribing practices, educate patients on proper antibiotic use, and promote infection control measures.

What are some mechanisms of resistance which aid in antibiotic resistance?

ESBLs which are encoded by plasmids, different expression levels, different biochemical characteristics such as activity against specific B-lactams, co-presence of other resistance mechanisms such as other B-lactamases, efflux or altered permeability

Define antimicrobial stewardship.

Antimicrobial stewardship (AMS) refers to an organisational or healthcare system-wide approach to promoting and monitoring judicious use of antimicrobials to preserve their future effectiveness.

How can antimicrobial stewardship be implemented?

Monitoring antimicrobial use and resistance in microbes, Consideration when developing new drugs, treatments, and diagnostics, Individuals' behaviour relating to infection prevention and control, antimicrobial use, and AMR, Healthcare professionals' prescribing decisions.