Researchers in Spain have revealed Listeria monocytogenes in various pork and poultry meat products.

184 meat samples were collected from different retailers in La Rioja. Listeria spp. and  monocytogenes were detected in 45 and 19 samples, respectively. 

The dominant Listeria species depended on the meat type, said researchers in the International Journal of Food Science and Technology.

Listeria monocytogenes was the top Listeria type found in chicken, quail, and pork meat, while Listeria innocua and Listeria welshimeri were the predominant species in duck and turkey meat, respectively.

Meats included 35 chicken, 37 quail, 31 duck, 37 turkey, and 39 pork samples from different retailers in La Rioja. In 30 of 45 samples, more than one species of Listeria was identified. A total of 164 strains were isolated from the 45 positive samples.

Positives by meat type
Listeria was detected in nine of 35 chicken samples, 13 of 31 duck samples, seven of 37 quail samples, seven of 51 turkey samples, and nine of 30 pork samples

Listeria monocytogenes was found in six of 35 chicken samples, seven of 37 quail samples, two of 51 turkey samples, and four of 30 pork samples.

“Special measures should be taken to reduce meat contamination such as adequate handling, correct preparation (enough cooking), and cleaning and disinfection to avoid cross-contamination,” said scientists.

Of 59 Listeria strains, 33 were multi-drug resistant, so they were resistant to more than three families of antibiotics. The highest multi-drug resistant rates were observed in Listeria monocytogenes at 14 of 19 strains.

The highest resistance rates were found in quail with six of seven strains multi-drug resistant, followed by chicken with six of 12, duck with nine of 19, turkey with four of nine, and pork with four of 12.

One Listeria monocytogenes strain from turkey was resistant to five antibiotics, and one from chicken was resistant to six antibiotics.

No strain was resistant to any antibiotic tested from the aminoglycoside or glycopeptide family. Resistance to ampicillin and trimethoprim–sulfamethoxazole was found in Listeria monocytogenes strains isolated from chicken, which is of concern since these antibiotics are used in treating listeriosis, said scientists.

Symptoms of Listeria infection can include vomiting, nausea, persistent fever, muscle aches, severe headache, and neck stiffness. Specific laboratory tests are required to diagnose Listeria infections, which can mimic other illnesses. 

Pregnant women, the elderly, young children, and people such as cancer patients who have weakened immune systems are particularly at risk of serious illnesses, life-threatening infections, other complications, and death. Although infected pregnant women may experience only mild, flu-like symptoms, their infections can lead to premature delivery, infection of the newborn, or even stillbirth.