Many studies on the evaluation of the antimicrobial activity of natural products have been conducted against various microorganisms, but the exploit of natural products meditated antimicrobial activity against Enterobacter hormaechei has not been found in the literature. In this study, we set up to investigate vanillic acid (VA)-mediated antimicrobial activities and its modes of action against carbapenem-resistant E. hormaechei (CREH). Minimum inhibitory concentration (MIC) of VA against CREH was examined by the agar diffusion method. Antibacterial mode of VA against CREH was elucidated by measuring variations in intracellular ATP concentration, intracellular pH, membrane potential, and cell morphology. Moreover, anti-biofilm formation of VA and its damage to CREH cells embedded in biofilms were further explored. Our results show that VA was effective against CREH with MIC of 0.8 mg/mL. VA could rupture cell membrane integrity of CREH, as measured by a decrease of intracellular ATP, pH and membrane potential, along with distinctive alternations in cell morphology. In addition, VA exerted a remarkable inhibitory effect on the biofilm formation of CREH and killed CREH cells within biofilms. These findings display that VA has a potent antibacterial and anti-biofilm activity against CREH, and hence has the potential to be exploited in clinic as a novel candidate agent to treat CREH infections and in the food industry as food preservatives and surface disinfectants.
Seafood is often associated with foodborne illnesses, and Vibrio parahaemolyticus is the most common pathogen implicated in outbreaks in Taiwan. In this study, the microbiological quality of 300 raw or mixed ready-to-eat (RTE) and other cooking-needed seafood samples was examined. The total aerobic and coliform counts of the RTE samples were significantly higher than those of other cooking-needed samples. On average, 55.8 and 29.7% of the RTE samples failed to meet the local microbiological standards for total aerobic (5 log CFU/g) and coliform (3 log most probable number [MPN] per g), counts respectively; the corresponding percentages for the RTE samples from Taipei City were 9.1 and 18.2%, respectively. The total aerobic and coliform counts in the RTE samples from supermarkets and chain restaurants were significantly lower than those from traditional restaurants. The Vibrio species were more frequently identified in the cooking-needed samples than in RTE samples. Low incidences of V. parahaemolyticus (1.4%), V. vulnificus (1.9%), and V. cholerae (0%) were detected in most RTE samples. High densities of V. parahaemolyticus and V. vulnificus (1,200 MPN/g) were detected in a few RTE samples, only one of which contained toxigenic ( tdh + ) V. parahaemolyticus . The results of this investigation reveal that better hygiene of seafood providers such as chain restaurants, supermarkets, and traditional restaurants in Taipei City would effectively improve the microbiological quality of the seafood. The results will facilitate the establishment of measures for controlling the risks associated with seafood in Taiwan.