Foot Osteomyelitis Caused by Multidrug- and Extensively Drug-Resistant Gram-Negative Bacteria

Abstract

There are scarce data regarding foot osteomyelitis (FO) caused by multidrug-resistant (MDR) and extensively drug-resistant (XDR) Gram-negative bacteria (GNB). This study investigates the causative organisms, the diagnostic and therapeutic approach and the outcome of these infections. All patients with FO caused by MDR and/or XDR GNB who received treatment in the Department of osseous infectious diseases of the "Attikon" University Hospital of Athens, Greece, were recorded and evaluated during a six-year-period. Seventeen patients, of which 64.7% females, with a mean age of 54.06 years were studied. There were nine cases with diabetic (DFO), and 76.5% of patients reported previous use of antimicrobials. Pathogens were isolated from soft-tissue biopsies or intra-operative tissue samples (n=12) and/or affected bone samples (n=5). In most cases, E. coli and P. aeruginosa were isolated (each 29.4%), followed by P. mirabilis (11.7%), while polymicrobial infection was detected in nine patients (53%). Most cases were given antimicrobial monotherapy (88.2%) with a mean duration of 90.05 days, while surgery significantly promoted cure of the infection. Foot and DFO cases represent a challenging to treat disease, requiring a multidisciplinary approach. Surgical treatment remains the cornerstone of treatment, while it is of utmost importance to isolate the causative organisms. MDR and XDR GNB represent an emerging threat and more data are needed to better understand these infections.

TABLE 1.

Clinical characteristics, treatment and outcome in MDR vs XDR FO cases. MDR=multidrug-resistant; XDR=extensively drug-resistant; FO=foot osteomyelitis

TABLE 2.

Antimicrobial resistance profile of Gram-negative causative pathogens. MDR=multidrug-resistant; XDR=extensively drug-resistant

TABLE 3.

Medical and surgical treatment of 17 patients with MDR/XDR GNB foot osteomyelitis. GNB=Gram-negative bacteria; MDR=multidrug-resistant; XDR=extensively drug-resistant; MER=meropenem; ERT=ertapenem; IMI/CL=imipenem/cilastatin; CIPR=ciprofloxacin; AMOX/CLAV=amoxicillin/clavulanate; CEFT=ceftazidime; PIP/TAZ=piperacillin/tazobactam; TYG=tigecycline; AZT=aztreonam; MIN=minocycline; COTR=cotrimoxazole; COL=colistin; antimicrobials linked by “+” correspond to combination treatment; if separated by “,” consecutive administration is indicated

TABLE 4.

Univariate analysis for factors associated with lack of cure in patients with FO by MDR/XDR GNB. MDR GNB=multidrug-resistant Gram-negative bacteria; XDR GNB=extensively drug-resistant Gram-negative bacteria; FO=foot osteomyelitis

FIGURE 1.

Kaplan-Meier survival analysis presenting the impact of surgery on foot osteomyelitis outcome