Abstract
Objective: The majority of patients with anaerobic bloodstream infections (BSIs) do not receive appropriate empirical antimicrobial treatment as this infection remains unsuspected on clinical basis. This study determines the incidence rate, the prevalence and antibiotic susceptibility pattern of anaerobes causing BSIs in East Sussex Healthcare Trust, England.
Methods: It is a retrospective study from July 2007 to July 2017. Demographic and laboratory data were collected on all microbiologically proven anaerobic BSIs.
Results: During the study period, 106,905 blood cultures were processed in the laboratory. A total of 324 anaerobic organisms were isolated from 312 blood cultures on 310 patients (167 males), representing a positivity rate of 0.30% of total blood cultures and 2.41% of total positive blood cultures (13,425). Approximately 76% (238 episodes) of anaerobic bacteremia occurred in >60 years old (236) patients. The admitting services were: emergency department (ED) (42%), medical (25%), surgical (16%) critical care unit (7%), and hematology (5%). The most frequent isolates were Bacteroidesspp. (42%), Clostridium spp. (24%), and Propionibacterium spp. (9%). Polymicrobial bloodstream infections were recorded in 45 episodes. Amoxicillin/clavulanic acid, metronidazole, clindamycin remained most effective antibiotics against anaerobes with a sensitivity rate of 93%, 92%, and 81% respectively. Penicillin was least sensitive (43%) against anaerobes.
Conclusions: This study highlights a low rate of anaerobic bacteremia during 10 years with Bacteroidesspp. as the predominant organism. This study also confirms that the empirical antibiotic therapy used in our hospital remains appropriate as more than 92% isolates were sensitive to amoxicillin/clavulanic acid and metronidazole. J Microbiol Infect Dis 2018; 8(4): 135-139

Key words: Anaerobes, antibiotics, bloodstream infections, susceptibility