The present study evaluated intracellular antibacterial efficacy of two short-chain cationic antimicrobial peptides (AMPs) namely, Cecropin A (1–7)-Melittin and lactoferricin (17–30) against three field strains of multi-drug resistant Salmonella Enteritidis. Initially, antimicrobial ability of both the AMPs was evaluated for their minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) against multi-drug resistant S. Enteritidis strains. Besides, the AMPs were evaluated for its in vitro stability (high-end temperatures, proteases, physiological concentrations of cationic salts and pH) and safety (haemolytic assay in sheep erythrocytes; cytotoxicity assay in murine macrophage RAW 264.7 cell line and human epithelioma HEp-2 cell line and beneficial gut lactobacilli). Later, a time-kill assay was performed to assess the intracellular antibacterial activity of Cecropin A (1–7)-Melittin and lactoferricin (17–30) against multi-drug resistant S. Enteritidis in RAW 264.7 and HEp-2 cells. The observed MBC values of Cecropin A (1–7)-Melittin and lactoferricin (17–30) against multi-drug resistant S. Enteritidis (128 μM; 256 μM) were generally twice or four-fold greater than the MIC values (64 μM). Further, both the AMPs were found variably stable after exposure at high-end temperatures (70 °C and 90 °C), protease treatment (trypsin, proteinase K, lysozyme), higher concentration of physiological salts (150 mM NaCl and 2 mM MgCl₂) and hydrogen ion concentrations (pH 4.0 to 8.0). Both the AMPs were found non-haemolytic on sheep erythrocytes, revealed minimal cytotoxicity in RAW 264.7 and HEp-2 cells, and was tested safe against beneficial gut lactobacilli (L. acidophilus and L. rhamnosus). Intracellular bacteriostatic effect with both cationic AMPs against multi-drug resistant S. Enteritidis was evident in RAW 264.7 cells; however, in both the cell lines, the significant bactericidal effect was not observed (P > 0.05) with both cationic AMPs understudy against multi-drug resistant S. Enteritidis. Based on the results of the present study, both the cationic AMPs understudy may not be useful for the intracellular elimination of multi-drug resistant S. Enteritidis; hence, further studies such as conjugation of these AMPs with either cell-penetrating peptides (CPP) and/or nanoparticles (NPs) are warranted.

本研究评估了两种短链阳离子抗菌肽（AMPs）Cecropin A（1-7）-蜂毒肽和乳铁蛋白（17-30）对三种对多药耐药肠炎沙门氏菌的田间菌株的细胞内抗菌作用。最初，这两个AMP的抗微生物能力的评价针对多重耐药其最低抑菌浓度（MIC）和最小杀菌浓度（MBC）S.肠炎菌株。此外，还对AMP进行了体外评估稳定性（高端温度，蛋白酶，阳离子盐的生理浓度和pH）和安全性（绵羊红细胞中的溶血分析；鼠巨噬细胞RAW 264.7细胞和人上皮瘤HEp-2细胞系以及有益的肠道乳杆菌的细胞毒性分析）。后来，进行了时间杀灭试验，以评估Cecropin A（1-7）-蜂毒肽和乳铁蛋白（17-30）对多重耐药S的细胞内抗菌活性。RAW 264.7和HEp-2细胞中的肠炎。观察到的天蚕素A（1-7）-蜂毒肽和乳铁蛋白（17-30）对耐多药S的MBC值。肠炎（128μM; 256μM）通常比MIC值（64μM）大两倍或四倍。此外，发现在高温（70°C和90°C），蛋白酶处理（胰蛋白酶，蛋白酶K，溶菌酶），较高浓度的生理盐（150 mM NaCl和2 mM MgCl）下暴露后，两种AMP均具有不同的稳定性。₂）和氢离子浓度（pH 4.0至8.0）。既在AMP被发现于羊红细胞非溶血，表明最小的细胞毒性在RAW 264.7和HEp-2细胞，并测试对有益肠道的乳杆菌（安全大号。嗜酸和大号。鼠李糖）。两种阳离子AMP对多药耐药S的细胞内抑菌作用。肠杆菌在RAW 264.7细胞中很明显。然而，在两种细胞系中， 两种阳离子AMPs均未针对多重耐药性S进行研究，未观察到明显的杀菌作用（P > 0.05）。肠炎。基于本研究的结果，无论是阳离子抗菌肽替补可能不是细胞内消除多重抗药性的有用小号。肠炎; 因此，需要进行进一步的研究，例如将这些AMP与细胞穿透肽（CPP）和/或纳米颗粒（NP）结合。