Effect of Acid Shock with Hydrochloric, Citric, and Lactic Acids on the Survival and Growth of Salmonella Typhi and Salmonella Typhimurium in Acidified Media

Abstract

The effect of acid shock with hydrochloric, citric, or lactic acid on the survival and growth of Salmonella Typhi and Salmonella Typhimurium in acidified broth was evaluated. Salmonella serovars were acid shocked (1 h at 35 degrees C) in Trypticase soy broth acidified with hydrochloric, citric, or lactic acid at pH 5.5. Unshocked cells were exposed to the same media that had been neutralized before use to pH 7.0. Shocked and unshocked cells were inoculated into broth acidified with hydrochloric acid (pH 3.0), citric acid (pH 3.0), or lactic acid (pH 3.8), and growth and survival ability were evaluated. The acid shock conferred protection to Salmonella against the lethal effects of low pH and organic acids. The adaptive response was not specific to the anion used for adaptation. The biggest difference in reduction of survival between shocked and unshocked strains (approximately 2 log CFU/ml) was observed when the microorganisms were shocked with lactic acid and then challenged with citric acid. Salmonella Typhi was more tolerant of citric acid than was Salmonella Typhimurium, but Salmonella Typhimurium had higher acid tolerance in response to acid shock than did Salmonella Typhi. The acid shock decreased the extension of the lag phase and enhanced the physiological state values of Salmonella Typhi and Salmonella Typhimurium when the pH of growth was 4.5. This increased ability to tolerate acidity may have an important impact on food safety, especially in the case of Salmonella Typhi, given the very low infectious dose of this pathogen.

Internalization ofSalmonella typhimuriuminto mango pulp and prevention of fruit pulp contamination by chlorine and copper ions

“…There is a need for data to establish whether levels of human pathogens capable of causing illness potentially occur on or within mangos. Under natural conditions, even a low level of bacterial contamination could present a significant human health risk, since the infectious dose of some Salmonella strains is very low (Arvizu-Medrano & Escartin 2005). According to the USEPA (1997) scientific advisory panel, both chlorine and copper ions met the standard of 2-Log 10 reduction, thus the mango processors would be free to choose alternative disinfectant methods, such as those presented in this study, that are adequate for their settings.…”

The Acid Tolerance Response of Salmonella spp.: An adaptive strategy to survive in stressful environments prevailing in foods and the host

“…Several studies have shown a wide variation in acid tolerance among Salmonella serovars and even among strains of a given serovar (Arvizu-Medrano & Escartín, 2005;Bacon et al, 2003;Berk et al, 2005;de Jonge et al, 2003;Jørgensen et al, 2000;Malheiros et al, 2009;Tiwari et al, 2004;Yuk & Schneider, 2006). Some of these studies have suggested a relationship between the intrinsic acid resistance and the pathogenic capacity of the bacterial strain.…”

“…Bacon et al (2003) described a low-pH-inducible ATR for S. Agona, S. Anatum, S. Mbandaka, S. Reading and S. Saintpaul after a long-term acid adaptation through bacterial growth in the presence of glucose; however, these authors did not find an ATR following a short-term acid shock at pH 4.3. Tiwari et al (2004) and Arvizu-Medrano and Escartín (2005) reported that survival of an adapted S. Typhi culture (pH 5.5) was significantly higher as compared to a control, non-adapted culture after an acid shock at pH 3.3 and pH 3.0, respectively. Yuk and Schneider (2006) assessed the acid tolerance of five Salmonella serovars (S. Agona, S. Gaminara, S. Michigan, S. Montevideo and S. Poona) in simulated gastric fluid after their adaptation at 7 and 20°C in apple, orange and tomato juices.…”

“…The first description was made by Leyer and Johnson (1992), who showed that S. Enteritidis, S. Heidelberg and S. Javiana displayed an increased acid tolerance against lactic acid at pH 3.85 after their adaptation to mild acid (pH 5.8) with hydrochloric acid for one doubling, with S. Javiana and S. Enteritidis showing the most marked response. Since then, an ATR has been observed in several occasions for a wide variety of Salmonella enterica serovars (Álvarez-Ordóñez et al, 2009b;Álvarez-Ordóñez et al, 2009c;Arvizu-Medrano & Escartín, 2005;Bacon et al, 2003;Malheiros et al, 2009;Perez et al, 2010;Tiwari et al, 2004;Yuk & Schneider, 2006). Bacon et al (2003) described a low-pH-inducible ATR for S. Agona, S. Anatum, S. Mbandaka, S. Reading and S. Saintpaul after a long-term acid adaptation through bacterial growth in the presence of glucose; however, these authors did not find an ATR following a short-term acid shock at pH 4.3.…”

Efficacy of chlorinated and ozonated water in reducingSalmonella typhimuriumattached to tomato surfaces

“…Under natural conditions, even a low level of bacterial contamination could present a significant human health risk, since the infective dose of some Salmonella strains is very low (Arvizu-Medrano & Escartin 2005).…”