Thursday, 11 April 2013

Antibiotic resistance mechanisms

Tufts University School of Medicine microbiologists and colleagues have identified the unique resistance mechanisms of a clinical isolate of E. coli resistant to carbapenems, according to Newswire. Carbapenems are a class of antibiotics used as a last resort for the treatment of disease-causing bacteria, including E. coli and Klebsiella pneumonia.

The study, published in the April issue of Antimicrobial Agents and Chemotherapy, demonstrates the the changes that bacteria undergo to become resistant to antibiotics.

Resistance to carbapenems usually emerges through the acquisition of an enzyme, carbapenemase, which destroys the antibiotic intended to treat infection. Resistance may also block entry of the drug into the E. coli bacteria. The current research sought to determine what made this a clinical isolate of E. coli resistant to carbapenem in the absence of carbapenemase (from the sputum of a patient at Peking Union Medical College Hospital in Beijing, China).

The bacteria  carried a mutation of the regulatory protein marR, which controls how bacteria react in the presence of antibiotics. The isolate further achieved resistance by increasing expression of a multidrug efflux pump. Moreover, the researchers discovered that the E. coli was expressing a new protein, called yedS, which helped the drug enter the cell, but whose expression was curtailed by the marR mutation.

To read more, see Antimicrobial Agents and Chemotherapy

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