A susceptibility report guides effective treatment for infections by helping medical professionals choose the right antimicrobial medications. Understanding this report clarifies how treatment decisions are made.
What is a Susceptibility Report?
A susceptibility report is a laboratory test result that identifies which antimicrobial medications, such as antibiotics or antifungals, are likely to be effective against a specific microorganism causing an infection. This report helps doctors select the most appropriate treatment, supporting effective patient care and reducing drug resistance.
This document is generated after a sample from an infected site is sent to a laboratory to identify the pathogen and test its response to various drugs. The testing determines the potential effectiveness of an antimicrobial agent on the organism.
Decoding the Report’s Core Sections
A susceptibility report typically contains several distinct sections, each providing specific information about the infection and potential treatments.
The initial part of the report includes patient and sample details. This section confirms the patient’s name, the type of sample collected (such as blood, urine, or tissue), and the date the sample was obtained. These details ensure the results correspond to the correct individual and clinical context.
Following patient information, the report identifies the specific microbe or microbes causing the infection, such as bacteria or fungi, isolated from the collected sample. Sometimes, more than one organism might be listed if multiple pathogens were detected.
A key section is the antimicrobial agents list, presenting the various drugs tested against the identified microbe. These are the medications a healthcare provider might consider for treatment.
Next to each antimicrobial agent, the report indicates its susceptibility category: S (Susceptible), I (Intermediate), or R (Resistant). Susceptible means there is a high likelihood the drug will be effective at standard doses. Intermediate suggests the drug might be effective if higher doses are used or if it concentrates well at the infection site. Resistant signifies the drug is unlikely to be effective, even at increased exposure. These categories are based on established standards, such as those from the Clinical and Laboratory Standards Institute (CLSI).
The report also includes the Minimum Inhibitory Concentration (MIC) for each tested drug. The MIC is the lowest concentration of an antimicrobial agent that prevents visible growth of the microorganism in a laboratory setting. The S, I, or R category remains the primary guide for clinical use, determined by comparing the MIC value to specific “breakpoints” established for each drug and organism combination.
Understanding Your Results
Interpreting the results of a susceptibility report involves understanding the practical implications of the “S,” “I,” and “R” categories for treatment.
Susceptible (S)
The organism is likely inhibited by the drug at the usual recommended dosage, making it a suitable choice for treating the infection.
Intermediate (I)
The drug might still be effective, but often requires a higher dosage or more frequent administration to achieve sufficient concentration at the infection site. This category suggests the drug could be considered in certain situations, especially if other options are limited or if the drug is known to concentrate well in the affected body area.
Resistant (R)
The drug is unlikely to be effective against the microorganism, even at higher doses. In most cases, a healthcare provider will avoid using drugs in this category to treat the infection, as doing so would likely lead to treatment failure.
It is important to discuss your susceptibility report with your healthcare provider. While the report provides crucial laboratory data, a doctor considers many other factors when choosing a treatment. These include your overall health, other medications you are taking, potential drug side effects, and the specific location and severity of your infection. The report is a tool that helps guide informed treatment decisions tailored to your individual needs.