GVPC Medium Manufactured without Oxygen Improves the Growth of Legionella spp. and Exhibits Enhanced Selectivity Properties

Abstract

Currently, GVPC is a recommended medium for the detection of Legionella spp. in water samples. However, recovery of Legionella spp. and selectivity properties can be improved.

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

“…(ii) The replacement of BSM serum by activated charcoal in Bru SIC allows normal growth of B. abortus bv1 and promotes early development of Brucella colonies. To understand whether the inhibition of B. abortus 2308 was due to charge instability, we studied the effect of replacing BSM serum with activated charcoal, as reported for other bacteria ( 30 ), since the negative surface of this component can interact with the cationic nature of polymyxins ( 31 ). In the presence of 1 to 4 g/L of activated charcoal, but not at lower concentrations, B. abortus 2308 grew at the levels of BAB.…”

“…As previously suggested, the synergy was probably due to vancomycin having increased access in the presence of colistin ( 32 ). The inhibitory effect of colistin against B. abortus bv1 disappeared progressively during storage of CM, attributable to their degradation in the presence of oxygen ( 31 ).…”

“…To solve the problem of B. abortus bv1 inhibition, we designed the new Bru SIC medium containing activated charcoal, whose key role as a radical and peroxide scavenger has been proposed in Legionella media, such as BCYE and GVPC ( 31 , 48 ). 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 ).…”

“…The presence of activated charcoal in Bru SIC had a positive action that could explain not only the stabilization of charges affecting antibiotic activity but also a detoxifying effect, allowing the growth of B. ovis PA in the absence of calf serum. Indeed, it has been suggested that activated charcoal can interact with reactive oxygen species secondarily generated by antibiotics or during medium preparation in a normal atmosphere, as well as with the positive charges of polymyxins and/or vancomycin, especially in the presence of oxygen ( 31 ). These free radicals could also partially degrade vancomycin, promoting the growth of the mildly resistant Gram-positive E. faecalis ( 31 ).…”

“…Indeed, it has been suggested that activated charcoal can interact with reactive oxygen species secondarily generated by antibiotics or during medium preparation in a normal atmosphere, as well as with the positive charges of polymyxins and/or vancomycin, especially in the presence of oxygen ( 31 ). These free radicals could also partially degrade vancomycin, promoting the growth of the mildly resistant Gram-positive E. faecalis ( 31 ). Hence, the addition of activated charcoal would explain the stabilization of both colistin and vancomycin, which we observed exerted a synergistic effect against the R-LPS mutant.…”