Background: The increasing problem of infections due to multidrug-resistant Gram-negative bacteria has led to re-use of polymyxins in several countries. However, there are already clinical isolates of Gram-negative bacteria that are resistant to all available antibiotics, including polymyxins.
Methods: We present a case series of patients with infections due to pathogens resistant to all antimicrobial agents tested, including polymyxins. An isolate was defined as pandrug-resistant (PDR) if it exhibited resistance to all 7 anti-pseudomonal antimicrobial agents, i.e. antipseudomonal penicillins, cephalosporins, carbapenems, monobactams, quinolones, aminoglycosides, and polymyxins.
Results: Clinical cure of the infection due to pandrug-resistant (PDR) Gram-negative bacteria, namely Pseudomonas aeruginosa or Klebsiella pneumoniae was observed in 4 out of 6 patients with combination of colistin and beta lactam antibiotics.
Conclusion: Colistin, in combination with beta lactam antibiotics, may be a useful agent for the management of pandrug-resistant Gram-negative bacterial infections. The re-use of polymyxins, an old class of antibiotics, should be done with caution in an attempt to delay the rate of development of pandrug-resistant Gram-negative bacterial infections.