Effect of Ceftaroline, Ceftazidime/Avibactam, Ceftolozane/Tazobactam, and Meropenem/Vaborbactam on Establishment of Colonization by Vancomycin-Resistant Enterococci and Klebsiella pneumoniae in Mice.

BACKGROUND

The potential for promotion of intestinal colonization with healthcare-associated pathogens by new antibiotics used to treat infections due to multidrug-resistant Gram-negative bacilli is unclear.

METHODS

Mice treated for 3 days with daily subcutaneous phosphate-buffered saline (control), ceftazidime/avibactam, ceftolozane/tazobactam, ceftaroline, and meropenem/vaborbactam were challenged with 10,000 colony-forming units (CFU) of vancomycin-resistant Enterococcus (VRE) resistant to each of the antibioics or carbapenemase-producing Klebsiella pneumoniae 1 day after the final treatment dose. The concentrations of VRE or K. pneumoniae in stool were measured on days 1, 3, 6, and 15 after challenge.

RESULTS

Control mice had transient low levels of VRE or K. pneumoniae (<3 log10 CFU/g) detected in stool with negative cultures on days 6 and 15 after challenge. In comparison to control mice, each of the antibiotics promoted establishment of high-density colonization with VRE (mean concentration, >8 log10 CFU/g of stool on day 1 after challenge) that persisted at >4 log10 CFU/g of stool through day 15 (P<0.01). In comparison to control mice, meropenem/vaborbactam and ceftaroline promoted high-density colonization with K. pneumoniae (peak concentration, >8 log10 CFU/g of stool) (P<0.01), ceftolozane/tazobactam promoted colonization to a lesser degree (peak concentration, >5 log10 CFU/g of stool), and ceftazidime/avibactam did not promote colonization (P>0.05).

CONCLUSIONS

Our results suggest that several beta-lactam antibiotics recently developed for treatment of infections with resistant Gram-negative bacilli have the potential to promote colonization by healthcare-associated pathogens. Additional studies are needed to examine the impact of these agents in patients.