MexAB-OprM Efflux Pump of Pseudomonas aeruginosa Offers Resistance to Carvacrol: A Herbal Antimicrobial Agent.

Carvacrol is a herbal antimicrobial agent with in vitro activity against several bacterial pathogens. However, multidrug resistant strains of Pseudomonas aeruginosa are resistant to herbal antimicrobial compounds including carvacrol. Resistance of P. aeruginosa to carvacrol is not well studied. This study was aimed to identify the gene(s) associated with carvacrol resistance, thus to understand its mechanisms in P. aeruginosa. A herbal drug resistant strain was isolated from a hospital environment. Carvacrol sensitive mutant was generated using transposon mutagenesis. The inactivated gene in the mutant was identified as mexA, which is part of the mexAB-oprM operon. Inactivation of the mexA gene resulted in a >31-fold reduction in MIC of carvacrol, whereas a >80-fold reduction was observed in the presence of drug efflux inhibitor phenylalanine-arginine ß-naphthylamide (PAßN). The parental herbal-resistant strain was completely killed within 3 h of incubation in the presence of carvacrol and PAßN. The mexA inactivation did not affect the resistance to other herbal compounds used. The results demonstrate that resistance to carvacrol in P. aeruginosa is mediated by the MexAB-OprM efflux pump.

Effect of dietary n-3 polyunsaturated fatty acid rich fish oil on the endometrial prostaglandin production in the doe (Capra hircus).

Recently, we showed that dietary supplementation of n-3 PUFA rich fish oil (FO) decreased the metabolites of serum prostaglandin (PG) F2α and E2 during the window of pregnancy recognition in the doe. In this study, we investigated its effect on the changes on endometrial PG production in vitro. Cycling does (n = 12) of Rohilkhand region were divided into two equal groups and fed a concentrate diet supplemented with either FO containing 26% n-3 PUFA (TRT; n = 6) or palm oil (CON; n = 6) @ 0.6 mL/kg body weight for 57 days. Estrus was synchronized by two injections of PGF2α analogue viz, on day 25 and 36 of supplementation and laparo-hysterotomy was performed to obtain endometrial tissue on day 16 of the synchronized estrus. Endometrial explant culture was done using a defined medium.The basal PG production was assayed at 6 and 12 h. Endometrial explant was stimulated with oxytocin (OXT) and/or recombinant ovine interferon tau (roIFN-τ) and PGs were assayed at 3 and 12 h post-treatment. The relative expression of genes related to PG metabolism in the endometrium was done by Quantitative Real Time PCR technique (qRT-PCR). There was a significant (P < 0.05) decline in the basal production of PGF2α and PGE2 in the TRT as compared to the CON group. The cultured endometrial tissue produced PGF2α in a time- dependent fashion in both the groups (P < 0.05). Neither OXT nor roIFN-τ had a significant (P > 0.05) effect on the PGF2α and PGE2 production in the TRT group. Similarly, the PG production in the OXT and roIFN-τ was comparable with the control in TRT. Expression of mRNA for cyclooxygenase-2 (COX-2), cytosolic phospholipase A2 (cPLA2) and PGF synthase (PGFS) was lower (P < 0.05) whereas, PGE synthase and peroxisome proliferator-activated receptors such as PPAR-γ and δ was increased (P < 0.05) in n-3 PUFA fed doe. In conclusion, dietary supplementation of FO decreased the endometrial production of PGF2α and PGE2 by downregulating the COX-2, cPLA2 and PGFS transcripts in the doe. The findings suggest that n-3 PUFA influence embryo survival by modulating the endometrial PG.