Colistin, rifampicin, and meropenem administered as single agents in a model of pneumonia caused by a carbapenem-resistant Acinetobacter baumannii

Use of colistin with rifampicin, trimethoprim-sulfamethoxazole and teicoplanin in acinetobacter mouse infection model

Background: Infections with multidrug-resistant Gram-negative bacteria such as Acinetobacter baumannii are major cause of morbidity and mortality. Colistin is used commonly to treat these infections. In this study, we evaluated the efficacy of different colistin combinations in a A. baumannii infection mouse model. Materials & methods: An A. baumannii mouse infection model was developed in 150 experimental animals. Treatment groups were as follows: colistin, colistin + rifampicin, colistin + trimethoprim/sulfamethoxazole, colistin + teicoplanin and a control group. The outcome was bacterial burden in the lung and liver tissues. The treatment groups were subdivided into 24-, 48- and 72-h groups. Results: Colistin and combinations reduce the A. baumannii burden significantly in lung and liver tissues compared with the control group. Compared with colistin alone colistin + rifampicin and colistin + TMP-SMX provided significantly better reduction in the bacterial burden. Conclusion: These results may suggest that rifampicin and TMP-SMX combination with colistin may have a potential role in the treatment of A. baumannii infections.

Colistin-glycopeptide combinations against multidrug-resistant Acinetobacter baumannii in a mouse model of pneumonia

Aim: To assess the effect of colistin-glycopeptide combination against a multidrug-resistant strain of Acinetobacter baumannii. Materials & methods: We used in vitro procedures (Etest method, checkerboard test and kill-time assays) and a mouse model of a carbapenem-resistant A. baumannii pneumonia. Results: The colistin-teicoplanin combination allowed a 74% increase of the survival in the mouse model within the 4 days following bacterial inoculation as compared with saline or colistin alone (p = 0.06). Concurrently, the colistin-vancomycin combination presented a similar efficacy as compared with saline or colistin alone in the mouse model. Conclusion: According to those preliminary results, using the colistin-teicoplanin combination in therapeutic deadlocks encountered in certain multiresistant A. baumannii pneumonia could be envisaged if the results are confirmed.

Mouse model of colonization of the digestive tract with Acinetobacter baumannii and subsequent pneumonia

AIM

Implementing a mouse model of Acinetobacter baumannii (AB) digestive colonization and studying the propensity of an intestinal reservoir of AB to be at the origin of pneumonia.

MATERIALS & METHODS

After a disruption of the digestive flora by piperacillin-tazobactam, two multidrug-resistant AB strains were intranasally inoculated to two cohorts of ten mice daily. For each strain, five mice were rendered transiently neutropenic.

RESULTS & CONCLUSION

One strain persisted several weeks in the digestive tract, even after stopping piperacillin-tazobactam injections, leading to the hypothesis that some AB strains can authentically colonize the gut. Most of the immunocompromised mice experienced clinical signs and positive lung cultures, which were associated with positive spleen cultures, an argument in favor of bacterial translocation.