Orthopedic-Implant Associated Infection due to Gram-Negative Bacilli: The Worrisome Impact of Acinetobacter baumannii Multidrug Resistance in a Brazilian Center

Abstract

Background. Orthopedic implant-associated surgical site infection (SSI) is a severe complication presenting a treatment challenge. Recently, Gram-negative bacteria orthopedic infections have become a global concern. Objective(s): To describe the bacterial profle of orthopedic implant-associated Gram-negative infections and specifc outcome of Acinetobacter baumannii infections. Methods. A single-center, retrospective cohort study analyzing the infection control database on the year 2016. Cases selected were those osteosynthesis or prosthetic joint, which evolved with SSI and Gram-negative bacterial growth in bone tissue or periprosthetic cultures. Results. In 2016, 4001 clean surgeries with orthopedic implant placement were performed; of which 84 fulfllled the criteria for SSI, according to CDC/NHSH defni-tions (54 cases of open fracture reduction, 24 of hip arthroplasty, five of knee arthro-plasty). Main agent of infections was Staphylococcus aureus (29.9%); Gram-negative bacteria however were responsible for 57.3% of infections (Enterobacter ssp. 22.4%; Acinetobacter baumannii 14.9%; Klebsiella pneumoniae 10%; Pseudomonas aeruginosa 10%). Among them, 100% Enterobacter ssp. were sensitive to carbapenems and 75% to ciprofoxacin. Klebsiella pneumoniae showed sensitivity to carbapenems in 85.7%, Pseudomonas aeruginosa showed sensitivity in 85.7% to carbapenems and 100% to ciprofoxacin. However, Acinetobacter baumannii showed the least favorable profle amongst Gram-negatives since only 12.5% of strains were sensitive to carbapenems, 28.6% to Ampicilin-sulbactam, 22.2% to ciprofoxacin, while showing 100% sensitivity to polymyxins. From 13 patients in whom Acinetobacter baumannii was isolated, none presented sepsis related to this infection, yet four of them died as result of hospital-ization-related complications (30.7% mortality rate). Among these deaths, two were related to total hip arthroplasty, one to knee arthroplasty and one to open fracture fxation. Among the survivors, two remain in antimicrobial use and seven showed remission/cure. Conclusion. SSI caused by carbepenem-resistant Acinetobacter baumannii represents great impact on morbi-mortality in patients who undergo surgery with placement of orthopedic implants.