Choosing antibiotics for intra-abdominal infections: what do we mean by "high risk"?
BACKGROUND
The definition of "high risk" in intra-abdominal infections remains vague. The purpose of this study was to investigate patient characteristics associated with a high risk of isolation of resistant pathogens from an intra-abdominal source.


METHODS
All complicated intra-abdominal and abdominal organ/space surgical site infections treated over a ten-year period in a single hospital were analyzed. Infections were categorized by pathogen(s). Organisms designated "resistant" were those that had a reasonable probability of being resistant to the broad-spectrum agents imipenem/cilastatin and piperacillin/tazobactam, and included non-fermenting gram-negative bacilli (e.g., Pseudomonas aeruginosa), resistant gram-positive pathogens, vancomycin-resistant enterococci, and fungi. Patient characteristics were analyzed to define associations with the risk of isolation of "resistant" pathogens.


RESULTS
A total of 2,049 intra-abdominal infections were treated during the period of study, of which 1,182 had valid microbiological data. The two genera of pathogens isolated from more than 25% of health care-associated infections and more commonly than from community-acquired infections were Enterococcus spp. (29%) and Candida spp. (33%). Health care association, corticosteroid use, organ transplantation, liver disease, pulmonary disease, and a duodenal source all were associated with resistant pathogens. By multivariable analysis, several acute and chronic measures of disease were predictive of death, with a strong interaction between solid organ transplantation, resistant pathogens, and death. Other links between specific pathogens and patient characteristics were documented, for example, between fungal infection and a gastric, duodenal, or small bowel source, and between liver transplantation and vancomycin-resistant enterococci.


CONCLUSIONS
On the basis of clinical characteristics, it may be possible to identify patients with intra-abdominal infections caused by pathogens that are potentially resistant to broad-spectrum antibacterial agents. Under these circumstances, and if warranted clinically, broadened coverage probably ought to include specific anti-enterococcal and anti-candidal therapy.
Swenson
Brian R
BR
Department of Surgery, University of Virginia, Charlottesville, Virginia 22908-0709, USA.
Metzger
Rosemarie
R
Hedrick
Traci L
TL
McElearney
Shannon T
ST
Evans
Heather L
HL
Smith
Robert L
RL
Chong
Tae W
TW
Popovsky
Kimberley A
KA
Pruett
Timothy L
TL
Sawyer
Robert G
RG
D034841:Abdominal Cavity; D000890:Anti-Infective Agents / Q000627:therapeutic use*; D001424:Bacterial Infections / Q000188:drug therapy; D003428:Cross Infection / Q000188:drug therapy* / Q000382:microbiology; D024881:Drug Resistance, Bacterial; D025141:Drug Resistance, Fungal; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009181:Mycoses / Q000188:drug therapy; D012189:Retrospective Studies; D013530:Surgical Wound Infection / Q000188:drug therapy* / Q000382:microbiology; D019737:Transplants / Q000009:adverse effects / Q000382:microbiology
D000890:Anti-Infective Agents