Impact of minimal inhibitory concentration breakpoints on local cumulative bacterial susceptibility data and antibiotic consumption

Antibiotic-Eluting Envelopes to Prevent Cardiac-Implantable Electronic Device Infection: Past, Present, and Future

Objective: Cardiac-implantable electronic device (CIED) infections are associated with significant morbidity and mortality. In this review, we describe the risk factors and pathogenesis of CIED infections and review the rationale and the evidence for the use of antibiotic-eluting envelopes (ABEs) in patients at increased risk for CIED infections.

Findings: The majority of CIED infections are caused by staphylococci that involve generator pocket and occur due to contamination of the device or the pocket tissues at the time of implantation. Clinical trials have shown that extending the duration of post-operative systemic antibacterial therapy is not beneficial in reducing CIED infection rate. However, ABEs that reduce device migration after implantation and provide sustained local delivery of prophylactic antibiotics at the pocket site, may provide benefit in reducing infection. Currently, there are two types of commercially available CIED envelope devices in the United States. The first ABE device (TYRX™, Medtronic Inc., Monmouth Junction, NJ) is composed of a synthetic absorbable mesh envelope that elutes minocycline and rifampin and has been shown to reduce CIED pocket infections in a large multi-center randomized clinical trial. The second ABE device (CanGaroo-G™, Aziyo Biologics, Silver Spring, MD) is composed of decellularized extracellular matrix (ECM) and was originally designed to stabilize the device within the pocket, limiting risk for migration or erosion, and providing a substrate for tissue ingrowth in a preclinical study. This device has shown promising results in a preclinical study with local delivery of gentamicin. Compared with artificial materials, such as synthetic surgical mesh, biologic ECM has been shown to foster greater tissue integration and vascular ingrowth, a reduced inflammatory response, and more rapid clearance of bacteria.

Conclusions and Relevance: ABE devices provide sustained local delivery of antibiotics at the generator pocket site and appear beneficial in reducing CIED pocket infections. Given the continued increase in the use of CIED therapy and resultant infectious complications, innovative approaches to infection prevention are critical.

Preclinical evaluation of efficacy and pharmacokinetics of gentamicin containing extracellular-matrix envelope

BACKGROUND

Using synthetic antibiotic-eluting envelope (ABE) is an effective intervention for prevention of cardiovascular implantable electronic device (CIED) infection. The biologic extracellular-matrix envelope (ECME), may offer potential advantages over the synthetic ABE. To further minimize the risk of infection, the ECME can be hydrated in gentamicin prior to CIED implantation. We aimed to evaluate the efficacy and pharmacokinetics (PK) of gentamicin containing ECME in an animal model.

METHODS

For all experiments, the ECME was hydrated in gentamicin (40 mg/Ml) (treatment) for 2 min. In vitro antimicrobial efficacy against six different bacterial species was assessed. In vivo experiments were conducted using a rabbit model of CIED pocket infection. Serum and ECM gentamicin concentrations were measured. Five different organisms were inoculated into the device pocket of control (ECME hydrated in 0.9% saline) and treatment groups. Macroscopic appearance and colony forming units from CIED, ECME, and tissue were determined.

RESULTS

No bacteria were recovered from any culture after 12 h of exposure to the gentamicin containing ECME. Serum gentamicin levels dropped below the limit of quantification at 15 h after implant. Gentamicin concentration in the ECME remained relatively stable for up to 7 days. Signs of clinical infection were observed in the control but not in the treatment group. In the presence of gentamicin, statistically significant reduction was demonstrated across all tested bacterial species.

CONCLUSIONS

In this preclinical animal infection model, gentamicin containing ECME was highly effective in reducing bacterial burden in the implant pocket, while systemic exposure after implantation remained low.

Surveillance of Antibiotic Use and Resistance in Intensive Care Units (SARI)

BACKGROUND

The project entitled Surveillance of Antibiotic Use and Resistance in Intensive Care Units (SARI) was initiated in Germany in 2000. In this article, we describe developments in antibiotic use and resistance rates in the participating intensive care units over the years 2001-2015.

METHODS

The intensive care units supplied monthly figures on patient days, antibiotic use (in defined daily doses, DDD), and resistance data for 13 pathogens. The density of antibiotic use per 1000 patient days was calculated on the basis of antibiotic use, DDD, and patient days, and the resistance density per 1000 patient days was calculated from the number of resistant pathogens.

RESULTS

In the years 2001-2015, data on 2 920 068 patient days were collected in 77 intensive care units. The average overall antibiotic use rose by 19% over this period, with a marked increase in the density of carbapenem use (from 76 to 250 DDD per 1000 patient days, +230%) and piperacillin-tazobactam use (from 42 to 146 DDD per 1000 patient days, +247%). The proportion of Escherichia coli and Klebsiella pneumoniae isolates that were resistant to third-generation cephalosporins increased markedly initially, then remained stable over the remainder of the observation period. The proportion of methicillin-resistant Staphylococcus aureus was stable over the entire period. The rates of vancomycin resistance among Enterococcus faecium isolates and imipenem resistance among gram-negative pathogens increased from 2.3% to 13.3% and from 0.1% to 0.3%, respectively.

CONCLUSION

The resistance density of gram-negative multiresistant pathogens in the participating intensive care units increased markedly. The rise in imipenem-resistant pathogens arouses particular concern. The increased use of broad-spectrum/reserve antibiotics may well have contributed to this development. Efforts to use antibiotics rationally, e.g., with the support of multidisciplinary "antibiotic stewardship" teams, are therefore vitally important. As participation in SARI is voluntary, these surveillance data cannot be considered representative of Germany as a whole.