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Today, the general public has become increasingly aware of salmonellosis problems. Organic acids are known by their antimicrobial potential and commonly used for improving the quality of poultry feed. In this context, the present work evaluated the inhibitory effect of four organic acids, namely, acetic acid, citric acid, lactic acid, and tartaric acid, at different levels of contamination by Salmonella typhimurium. The neutralization of these organic acids in vitro and in the presence of one-day-old chick's organs was also investigated during the search for Salmonella serovars in birds as described in the Moroccan standard “NM 08.0.550.” The effect of four organic acids on Salmonella typhimurium was tested in vitro and in the presence of chick's organs at different concentrations set of strain and organic acids tested. The MIC results demonstrated that tartaric acid, citric acid, and acetic acid inhibited Salmonella typhimurium at concentrations of 0.312%, 0.625%, and 0.512% for the three levels of strain: 10, 100, and 103 CFU/ml, respectively, while lactic acid and depending on the amount of the strain introduced acts differently: 0.078% for 10 CFU/ml and 0.156% for 100 and 103 CFU/ml. The concentration of 0.04M of Na2HPO4 solution has proved, in vitro, in caecums and organs of chicks (in presence of organic acids) that strain introduced, even at low concentrations, can be recovered. The use of additives has beneficial effects in Salmonella control program. However, the present results recommend the amendment of Salmonella research standard, taking into account the probable presence of organic acids in digestive content of one-day-old chicks.

The development of multi-drug-resistant bacteria pushed the scientific community to look for new alternatives to solve the problem. Propolis is a beehive substance and one of the richest natural products in bioactive compounds with antibacterial activity. This study was aimed to investigate the possible synergistic interaction between propolis and antibacterial drugs, such as essential oils (EOs) and antibiotics, in order to find increased activity with decreased concentrations. Two ethanol extracts of propolis were used for the test, which were collected from the north of Morocco. The chemical composition was determined by UHPLC-MS. The synergistic effect of propolis extracts with EOs and antibiotics was tested using the checkerboard technique. The chemical analysis showed the presence of more that 100 compounds in propolis extracts, belonging mainly to flavonoids. The combination of propolis with the other antibacterial drugs showed different types of interactions with FIC index values varied from 0.18 to 1, but no antagonist effect was noticed. With FICI<0.5, the synergistic effect was obtained with essential oils as well as with antibiotics. These results indicate that propolis can be a promising source of molecules with medical interest to treat bacterial infection and/or to increase the action of antibiotics.

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