Increased selectivity of Mitis-Salivarius agar containing polymyxin

Area of Science:

• Microbiology
• Bacteriology
• Oral Health

Background:

• Mitis-Salivarius medium is crucial for enumerating oral streptococci.
• Overgrowth by gram-negative spreading organisms can compromise Mitis-Salivarius plate analysis.
• Accurate differentiation of streptococci is essential for oral microbiome studies.

Purpose of the Study:

• To evaluate the efficacy of polymixin B sulfate in Mitis-Salivarius medium.
• To determine if polymixin B sulfate inhibits gram-negative bacteria without affecting oral streptococci.
• To improve the reliability of streptococcal enumeration from oral samples.

Main Methods:

• Incorporation of polymixin B sulfate into Mitis-Salivarius medium at 100 U/ml.
• Inoculation of plates with oral samples.
• Observation of bacterial growth, specifically gram-negative organisms and streptococci.

Main Results:

• Polymixin B sulfate at 100 U/ml effectively suppressed gram-negative spreading organisms.
• The antibiotic did not inhibit the growth of oral streptococci.
• Typical colonial characteristics of oral streptococci remained unaffected.

Conclusions:

• Polymixin B sulfate is a valuable selective agent for Mitis-Salivarius medium.
• This method enhances the suitability of Mitis-Salivarius plates for streptococcal analysis.
• The findings support improved diagnostic and research capabilities in oral microbiology.