Note on correction: the headline has been corrected. Four of nine plants tested positive.
Researchers have estimated the prevalence of Listeria monocytogenes in beef from the Brazilian state of Mato Grosso, which is the largest producer and exporter of beef in the country.

From 50 samples analyzed, Listeria spp. was isolated in 18 and Listeria monocytogenes was confirmed in six of them, according to the study published in the journal Microorganisms.

Nine of 13 processing plants evaluated were positive for Listeria spp.

“These findings cause concern as they indicate that these positive plants are also suitable for Listeria monocytogenes growth,” said researchers.

Despite international regulations being followed by export-authorized plants, Brazilian internal rules only require the control of Listeria monocytogenes in ready-to-eat products.

More than 70 countries import fresh beef from Brazil including China, the Netherlands, Italy and Turkey. A ban is currently in place in the U.S. on fresh beef imports from Brazil.

Cleaning and disinfection
During a six-month period, 50 beef samples from 13 different export-authorized processing plants in Mato Grosso were obtained from regular material used in the pathogen monitoring program of the official inspection service.

Listeria isolates came from beef in nine different processing plants, but Listeria monocytogenes was confirmed in only four of them.

The serotype 4b, 4d or 4e was isolated in samples from processing plants in Várzea Grande exclusively. Serotypes 1/2b, 3b or 7 were isolated from samples in processing plants in Colíder and Matupá.

Listeria monocytogenes isolates were susceptible to most assessed antibiotics, although high rates of resistance were detected to sulfonamides, cefoxitin and cefepime.

All isolates presented minimal inhibitory concentrations (MICs) below the recommended concentrations of benzalkonium chloride, chlorhexidine, peracetic acid and quaternary ammonium.

However, two isolates exhibited MIC of sodium hypochlorite three times higher than its recommended concentration. The high availability and affordable price of sodium hypochlorite make it one of the most used disinfectants by industry and production farms.

Researchers said more intensive measures of cleaning and disinfection must be adopted by the beef processing industry of Mato Grosso.

“This situation puts at risk not only the Brazilian customer, but also the population of the countries that import beef from those processors.”

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