Alcaligenes faecalis: An Emerging Extensively Drug-Resistant Bacterium

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Retrospective analysis was conducted to assess the presence of A faecalis infection, extensively drug-resistant A faecalis infection, and the susceptibility of commonly used antibiotics for the treatment of A faecalis and XDR A faecalis.

Alcaligenes faecalis (A faecalis) has shown a decreasing susceptibility to commonly used antibiotics with an emergence of extensively drug-resistant A faecalis infections, according to study results published in BMC Infectious Diseases.

This 6-year retrospective analysis between 2014 and 2019 included 61 adult patients with A faecalis infections. Of the 61 patients, 37 (60.7%) had a history of intravenous antibiotic use within the past 90 days. A total of 52 patients had community-acquired infections with 59.6% (31/52) had a history of previous hospitalization within 90 days.

The majority of patients had cystitis (n=25), followed by diabetic foot ulcer (n=9), pneumonia (n=8), acute pyelonephritis (n=7), bacteremia (n=3), and the remaining had infection at specific sites (n=9). Polymicrobial infection was evident in 83.6% of patients and the most common mixed infection pathogens included Enterococcus species (n=9), Proteus vulgaris (n=9), and Pseudomonas aeruginosa (n=8). While patients with A faecalis infections also had other bacterial infections, the author stressed that A faecalis be viewed as a pathogen and not a contaminant, except in cases where A faecalis infection was resolved without use of active treatment.

Antibiotic susceptibility test revealed that imipenem, meropenem, and ceftazidime had the best sensitivity rate to A faecalis (66.7%). The sensitivity rate was less than 50% for ciprofloxacin and piperacillin/tazobactam.

There were 4 cases of extensively drug-resistant A faecalis infection (2 in patients with pneumonia and 2 in patients with diabetic foot ulcers). The overall treatment failure rate was 11.5%.

Limitations of the study included a small sample size, and reports of misidentification of Acinetobacter baumannii as A faecalis by the antimicrobial susceptibility testing with the VITEK 2 system.

Combining the results of this study with a literature review of 130 reported cases of A faecalis infection mostly in newborns and infants, the most frequent A faecalis infection site, in order, were bloodstream, urinary tract, skin and soft tissue (56.5% were diabetic foot ulcers), and middle ear.

“With adequate intravenous antibiotic therapy, patients with A faecalis infection will typically experience a positive treatment outcome,” the author concluded.


Huang C. Extensively drug-resistant Alcaligenes faecalis infection. BMC Infect Dis. 2020;20(1):833. doi:10.1186/s12879-020-05557-8