S. Infantis: an emerging serotype that became resident? Part II

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High temperature resistance.

Some Salmonella spp serotypes can survive after heat treatment of feed and litter. The survival of S. infantis after heat treatment of feed is not very clear.

However, some studies have demonstrated its presence in finished feed for broilers, but it is possible that this is due to post-treatment recontamination, rather than the heat resistance characteristic (Pulido, 2019).

Survival in conditions of low humidity, low water activity.

Outbreaks of S. infantis that occurred in the United States in 2012 were associated with dry pet food (CDC, 2012).

In this outbreak, it brought the attention that this bacterium could survive under low humidity conditions.

It has also been shown that S. infantis can survive on dry food (pasta) for up to 12 months (Finn et al., 2013; Burgess et al., 2016).

Resistance to low humidity conditions has been studied in detail for the Tennessee and Typhimurium serotypes, finding that they use a cell contraction strategy (going from a rod shape to a coccoid shape) that gives them a strong resistance to desiccation (greater in S. Tennessee than in S. Typhimurium LT2). (Grusdev et al., 2011).

S. infantis may be able to survive on dry food, use these and other strategies to survive in environments with low water activity.

Another aspect worth noting is that Salmonella spp serotypes that are resistant to desiccation may exhibit cross-tolerance to other unfavorable conditions.

• The studies carried out by Grusdev et al. in 2011 showed that S. Typhimurium, S. Newport, S. Enteritidis and S. Infantis could survive the presence of NACL in bile salts, ethanol (30%, 5 min), dry heat (100°C, 1h) and UV irradiation (125 W/cm2 , 25 min).
• Additionally, dried cells of all these serotypes survived exposure to
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