What do you mean by Bacitracin test?
A microbiological test called the Bacitracin test is used to identify specific types of bacteria, namely group A streptococci, which are also referred to as Streptococcus pyogenes.
What do you mean by Bacitracin ?
Although use in animals leads to antibiotic resistance, bacitracin is a polypeptide antibiotic used in human medicine that is “authorised by the US Food and Drug Administration (FDA) for use in hens and turkeys.”
As bacitracin zinc salt, it is used as a topical treatment for a range of localised skin and eye infections as well as for the prevention of wound infections. It is combined with other topical antibiotics (usually polymyxin B and neomycin) as an ointment known as “triple antibiotic ointment,” under the brand name Neosporin. For eye infections, there is also an ophthalmic solution that is not an ointment.
Table of Contents
A laboratory process called the bacitracin susceptibility test is performed to find out whether a particular type of bacteria is susceptible to the antibiotic bacitracin. The main purpose of this test is to detect Group A streptococci, also known as Streptococcus pyogenes, which is the cause of many diseases, including impetigo, scarlet fever, and strep throat.
Recognizing the Fundamental
A polypeptide antibiotic called bacitracin prevents bacteria from synthesizing their cell walls. It functions by obstructing the synthesis of peptidoglycan, an essential part of the bacterial cell wall. This damage results in weaker cell walls, which ultimately cause bacterial mortality and cell lysis.
Conditions to Pass the Test
Bacterial culture: The suspicious bacteria must be isolated and cultivated in a pure culture on the proper medium.
Bacitracin disks: Sterile disks that are commercially available and impregnated with bacitracin at a predetermined concentration (typically 0.04 units).
Culture media: Mueller-Hinton agar is the typical culture medium used for this test.
Sterile swabs: To distribute the bacterial culture around the agar plate, use sterile swabs.
Equipment for incubation: An incubator with a 35–37°C temperature range.
Measuring tool: A caliper or ruler to determine the inhibitory zones.
Method
The method for Bacitracin test,
Get the platter ready: A pure culture of the suspected bacteria should be added to a Mueller-Hinton agar plate for infection.
Application of the disk: Using sterile forceps, place a bacitracin disk onto the infected plate. Make sure the disk touches the agar surface all the way.
Incubation: For 18 to 24 hours, incubate the plate at 35 to 37°C.
Zone of inhibition measurement: Measure the width of the zone of inhibition, or the clear region around the disk where bacterial growth is blocked, in millimeters after incubation.
Interpretation of the Results
The interpretation of the Bacitracin test,
Sensitive
Bacteriophage susceptibility to bacitracin is indicated by a zone of inhibition that is 10 mm or more. This is a characteristic of streptococci in group A.
Resistant
Bacteriobacterium resistance to bacitracin is shown by a zone of inhibition less than 10 mm. Resistance in other bacterial species is possible.
Importance of Bacitracin test
In microbiology, the Bacitracin test is an easy, affordable, and trustworthy way to distinguish between various bacterial species, especially Streptococcus species.
Why this exam matters is as follows
Group A Streptococci (GAS) identification
One important diagnostic method for determining the presence of Streptococcus pyogenes, the bacteria that causes strep throat, scarlet fever, and other diseases, is the Bacitracin test.
Bacitracin inhibits the development of this bacteria because it is susceptible to it.
The zone of inhibition around the disc in a positive Bacitracin test strongly indicates the presence of GAS.
Distinguishing Between Streptococcus Species
There are several species of Streptococcus, some of which are pathogenic (cause sickness), and others of which are benign.
There are differences in bacitracin sensitivity throughout groups.
For example, certain streptococcal types, such as Group B streptococci (GBS), are resistant to Bacitracin, but Group A streptococci (GAS) are susceptible to it.
Significance for Clinical Practice
When treating strep throat, a positive Bacitracin test result from a throat swab sample might be helpful.
Additionally, it helps reduce complications by assisting in the early detection and treatment of additional GAS infections.
A positive test may assist in identifying the cause and directing therapy in cases such as meningitis or wound infections.
Significance for Public Health
By quickly identifying GAS, illness cannot spread further and may be treated and isolated.
This is especially crucial in places like nursery schools and schools where epidemics might happen.
Based on test findings, public health interventions such as antibiotic treatment and contact tracing may be successfully implemented.
Uses of Research
Research on streptococcal infections uses the Bacitracin test to better understand bacterial resistance and create novel therapies.
Test Restrictions
Not a conclusive test: The susceptibility of other bacterial species should not be ascertained with this test. The principal use for it is the detection of Group A streptococci.
False negatives: It’s possible that some Group A streptococci strains have an innate resistance to bacitracin.
Factors that interfere: The accuracy of the test may be impacted by certain compounds present in the culture medium.
Not a replacement for antimicrobial susceptibility testing: This test doesn’t tell you if the bacterium is susceptible to other antibiotics.
To sum up
One easy-to-use and trustworthy method for determining the presumed identity of Group A streptococci is the bacitracin susceptibility test. It should, however, be used in combination with other diagnostic techniques since it is not a conclusive test. More thorough techniques, such as the Kirby-Bauer disk diffusion test or broth dilution procedures, should be used for reliable antimicrobial susceptibility testing.
Frequently Asked Questions(FAQ)
Write about public health?
The well-being of entire populations is the main emphasis of the diverse discipline of public health. The goal should be to prevent diseases in the first place rather than only treat them as they arise. Imagine it as a sword fighting personal fights, but also as a shield shielding society from health risks.
What do you mean by Group A Streptococci (GAS)?
Many infections involving Streptococcus pyogenes, a group A streptococcus (GAS), are referred to as group A streptococcal infections. A form of beta-hemolytic Gram-positive bacterium known as S. pyogenes is the causative agent of a variety of infections, the majority of which are common and mild. An illness known as an invasive GAS (iGAS) can become serious and potentially fatal if the bacteria penetrate the bloodstream.
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