Resistance to β-lactams in Bacteria Isolated from Different Types of Portuguese Cheese

The purpose of this study was to investigate the presence of β-lactam-resistant bacteria in six different types of Portuguese cheese. The numbers of ampicillin resistant (AMP(r)) bacteria varied from 4.7 × 10(2) to 1.5 × 10(7) CFU/g. Within 172 randomly selected β-lactam-resistant bacteria, 44 resistant phenotypes were found and 31.4% were multidrug resistant. The majority (85%) of the isolates identified belonged to the Enterobacteriaceae family. The presence of the bla(TEM) gene was detected in 80.9% of the tested isolates. The results suggest that without thermal processing of the milk and good hygienic practices, cheese may act as a vehicle of transfer of β-lactam-resistant bacteria to the gastrointestinal tract of consumers.