Salmonella Resistant to Different Antibiotics

Salmonella, a common bacteria that causes foodborne diseases, are resistant to several antibiotics used to treat infections, suggests new research.

For the study, the researchers sequenced and investigated the genomes of 90 strains of a specific serological variant (serovar) of Salmonella enterica known as S. Typhimurium.

When the action of antibiotics in each of the 90 strains was tested, it was discovered that the vast majority were resistant to different classes of antibiotics that are part of the arsenal of medicine.

The study, published in the journal PLOS ONE, also identified 39 genes responsible for resistance to antibiotics.

"It is striking that S. Typhimurium is resistant to antibiotics that can be used to treat the disease. These drugs are available to physicians for use in combating infections that display resistance," said Amanda Aparecida Seribelli from the University of Sao Paulo in Brazil.

Salmonella comprises two species, S. bongori and S. enterica. The latter is the type species, with a large number of subspecies and serovars that cause more foodborne infections than any other species in Brazil and worldwide.

The human and animal intestinal tract is the main natural reservoir for this pathogen, with poultry, pork and related food products serving as major transmission vectors.

The six subspecies of S. enterica are subdivided into 2,600 serovars.

The most important subspecies of S. enterica from the epidemiological standpoint is S. enterica subspecies enterica, which causes the foodborne infection known as salmonellosis. The symptoms are diarrhoea, fever, stomach cramps and vomiting.

The most frequently isolated serovars of this subspecies are S. Typhimurium and S. Enteritidis.

All the 90 strains analysed in the study belonged to S. Typhimurium.

Whole-genome sequencing of the main bacteria that cause acute diarrohea was the focus of the research.

According to the study, 65 of the strains proved resistant to sulfonamides, 44 to streptomycin, 27 to tetracycline, 21 to gentamicin and seven to ceftriaxone, a cephalosporin antibiotic.