The evolving threat of carbapenem‐resistant infections after liver transplantation: The case of A cinetobacter baumannii

Abstract

Postoperative bacterial infections have shifted from predominantly gram-positive to gram-negative organisms in liver transplantation (LT) recipients.(1) Of concern is the increasing incidence of difficult to treat multidrug resistant (MDR) infections due to extended spectrum b-lactamases and carbapenemresistant Enterobacteriacae. The high mortality rate (40%-70%) associated with post-LT carbapenemresistant Klebsiella pneumoniae (CRKP) infections is a sobering example of the impact of MDR infection in this population. (2,3) In this issue of Liver Transplantation, Freire et al. (4) provide compelling evidence that an additional organism, carbapenem-resistant Acinetobacter baumannii (CRAB), is also associated with very high morbidity and mortality after LT. In a prospective 2-year cohort study, the authors routinely surveyed colonization with A. baumannii at 3 body sites (rectum, throat, and axilla) immediately prior to LT and weekly thereafter until hospital discharge. Of the 196 LT recipients evaluated, 105 (54%) were found to have acquired CRAB, most often (n 5 81) during the post-LT period. Similarly, although 60 recipients developed CRAB infection, the majority of these (n 5 56) occurred post-LT and usually early in the post-LT course (median time, 9 days; range, 1-43 days). The likelihood of post-LT CRAB acquisition increased with retransplantation within 60 days after LT and prior use of piperacillintazobactam or a carbapenem. Most notably, 60-day mortality in the recipients with CRAB infection was 46.4%. Risk factors associated with 60-day mortality included LT for acute liver failure, need for post-LT dialysis, prolonged cold ischemia time, and a trend toward significance for pre-LT CRAB acquisition. Molecular typing by pulsed-field gel electrophoresis (PFGE) analysis revealed that 71% of infected recipients had 1 predominant strain, suggesting a clonal outbreak in the LT unit or across the hospital. Importantly, a series of infection control measures including weekly surveillance cultures, contact precautions, contact isolation of CRAB-colonized patients, hand hygiene training, and systematic discussions of CRAB cases attributed to the unit resulted in the incidence of CRAB acquisition dropping from 12.2/1000 patient-days in 2009 to 5.5/1000 patient-days by 2014.Although these findings are remarkable, some aspects of the conclusions should be interpreted with caution. For instance, this study was performed during an outbreak, perhaps limiting its applicability. It also remains unclear if this was solely an outbreak in the LT unit or represented a hospital-wide outbreak. In addition, although the crude 60-day mortality was very high, determining the attributable mortality of post-LT CRAB infections is difficult. In prior studies that rigorously controlled for severity of illness, A. baumannii infection was not independently associated with increased mortality, raising the possibility that this organism is a marker of increased severe underlying illness rather than an independent predictor of mortality. (5,...

Genomic Surveillance Reveals Diversity of Multidrug-Resistant Organism Colonization and Infection: A Prospective Cohort Study in Liver Transplant Recipients

“…We screened 998 stool samples and 119 rectal swabs (median, 8 [IQR, [4][5][6][7][8][9][10][11][12] samples per patient). Rectal swabs were taken predominantly in the early posttransplant period and were associated with less MDRO recovery than stool specimens ( In the cohort, 23 of 97 (23%) bacterial infection episodes were due to MDRO (Supplementary Table 1).…”

“…Multidrug-resistant organisms (MDROs) represent an important cause of morbidity and mortality after solid organ transplantation (SOT) [1][2][3]. SOT recipients colonized with MDROs may serve as important reservoirs of MDRO transmission across the healthcare setting [4]. Elucidating mechanisms of MDRO colonization, infection, and transmission in SOT recipients is thus an urgent priority.…”

Colonizing multidrug-resistant bacteria and the longitudinal evolution of the intestinal microbiome after liver transplantation

“…We and others have demonstrated a critical role for intestinal MDRB colonization prior to the development of infection 4,5 . MDRB infections, in turn, significantly impact post-LT survival 4–6 , making colonization by MDRB a critical factor in the transplant-related clinical course. Recipients of LT receive frequent and sustained antibiotic regimens and routinely experience adverse clinical events after transplantation 4,7 .…”

Incidence, mortality, and risk factors associated with carbapenem‐resistant Acinetobacter baumannii bacteremia within 30 days after liver transplantation

“…In addition, the 30-day mortality rate calculated in our study was higher than the previously reported 60-day mortality rate (46.4%) for LT recipients with CRAB infections. 21 Furthermore, in our study, the initial mortality rate was high after CRAB-B detection, with a cumulative incidence of 58.6% at 5 days, which can be attributed to the high fatality of CRAB-B among CRAB infections after LT. Therefore, timely optimal treatment for CRAB-B, such as proper antibacterial and immunosuppression modification, is necessary.…”