Bacteria producing extended spectrum β-lactamases (ESBLs) are the major cause of hospital-acquired infection, with the majority of ESBL producers being isolated from critical care patients. ESBLs remain one of the major causes of failure of therapy with cephalosporin-type antibiotics, which are one of the most widely used human and veterinary antibiotics around the world. It is becoming increasingly clear that antibiotic resistant bacteria (ARB) and genes (ARGs) are not confined to the clinical environment; they have been found in natural environments, suggesting that those environments and especially soils are reservoirs of ARB and ARGs that play an important role in the spread of AR in clinical environments.
Some of the questions addressed in our research are: i) if third generation cephalosporin antibiotics, affect microbial activity and bacterial community composition of undisturbed soils; ii) if ESBLs genes are present in such soils; and iii) if the ARGs can be transfer to human pathogenic bacteria. Our results suggest that a large fraction of the natural soil microbiome is highly resistant to ceftriaxone and many other antibiotic families. Also, the microbial activity in undisturbed soils is not affected by soil irrigation with clinical doses of ceftriaxone. We discovered that this stems from high soil β-lactamase activity, which is supported by the ubiquitous presence of ESBL genes in three different soil types analyzed, implying a very close relation between AR in clinical environments and AR in undisturbed soil environments. Finally, preliminary results show that AR is transfer in vitro to E. coli cv 601.
