Evaluation of Adding Erythritol to Farrell Medium for Primary Isolation of the Brucella melitensis Strains

Abstract

This study aims to evaluate the addition of erythritol to Farrell medium (FM) for the primary isolation of B.melitensis strains. Selective media, particularly FM, is commonly used for Brucella isolation. Isolation is the gold standard for the diagnosis of brucellosis. The isolation success of selective media depends on their ingredients. Isolation rate may decrease particularly in contaminated samples; therefore, the addition of components like erythritol that augments the growth of Brucella species on media can support isolation. In this study, organ samples associated with 14 small ruminant abortion cases caused by B.melitensis strains were utilized. Organ suspensions were inoculated to FM and Farrel medium with erythritol (F+ER) simultaneously. The media's isolation and inhibition performance was observed during incubation. The addition of erythritol was evaluated based on whether it provides earlier isolation with the help of increasing the colony growth rate and colony size. According to the findings, F+ER is more advantageous for 12 samples among 14 through isolation as it enables faster colony growth and larger colonies. The results confirm the recommendation of adding erythritol particularly in the samples with inadequate contaminant inhibition. Therefore, high isolation performance can be achieved through erythritol addition to the selective media like FM.

Bru SIC: a novel selective medium for the primary isolation of Brucella in veterinary samples

“…Higher concentrations of activated charcoal were considered unsuitable, since they allowed the growth of contaminant microorganisms and impaired the translucence for Brucella colony identification. These facts, together with the faster growth of all brucellae colonies in Bru SIC than in FM, CM, and BSM, indicate that Bru SIC can be highly recommended as an alternative medium ( 34 , 37 , 49 ). Activated charcoal has been occasionally used in bacterial culture due to its detoxifying properties ( 30 , 51 , 52 ), but to our knowledge it has never been applied for the identification of Brucella .…”

“…In addition to a higher recovery of CFU, the activated charcoal promoted a faster growth of Brucella colonies in Bru SIC, avoiding false-negative results arising from insufficient incubation, as described for B. ovis or B. suis cultures in FM ( 17 , 19 ). Another previously proposed strategy to promote Brucella growth in selective culture media is the addition of enrichment components such as erythritol ( 34 , 49 ). Interestingly, we observed that the substitution of calf serum by activated charcoal in Bru SIC allowed the successful isolation of more demanding Brucella strains, such as B. ovis PA.…”

The Effect of Erythritol Injection in Decreasing of Abortion Rate in Local Breed Ewes

“…It was intriguing that, if erythritol could promote B. melitensis growth in broth culture, it did not also promote bacterial development inside macrophages [ 12 ]. Erythritol was found to be a suppressor of intracellular growth in earlier studies looking at how it affected intracellular B. abortus in cow trophoblasts, though these studies never compared growth with and without erythritol in the culture medium [ 32 ].…”

“…Te presence of a growthstimulatory substance, eventually identifed as the 4carbon sugar erythritol [11], in the fetal tissues was determined to be the cause of this abnormally high bacterial count. Te inability of the B. abortus vaccine strain S19 to use erythritol as a carbon source was formerly thought to be directly linked to the virulence of the organism [12]. Recent research [13][14][15] suggests there may be a relationship between erythritol and virulence, albeit this correlation was not as strong as frst thought.…”