Bacterial spectrum and antimicrobial-resistance pattern of bloodstream infections in neutropenic and non-neutropenic adult cancer patients

Background: Bloodstream infections (BSI) in cancer patients remain associated with significant morbidity and mortality. The choice of an empirical antibiotic regimen is usually based on the local epidemiology of the microorganisms and their antimicrobial susceptibility profile. We present the spectrum and the antimicrobial susceptibility of the causative agents of BSI in adult cancer patients in East Sussex Healthcare Trust (ESHT), UK. Materials and Methods: This retrospective study was conducted at ESHT from January 2006 to December 2015. Demographic and laboratory data were collected from the pathology information system. Results: A total of 640 episodes of BSI occurred in 297 patients (159 male). Of the 297 patients, 239 (80%) had haematology malignancies, whereas 54 (18%) had solid organ tumours. Four patients had both. Majority of BSI (383, 60% episode) occurred in neutropenic patients. A total of 802 organisms (477 [59%] and 325 [41%] organisms from neutropenic and non-neutropenic patients, respectively) were isolated. Of 802, 406 (51%) Gram-positive and 386 (49%) Gram-negative organisms were isolated. Seven Mycobacterium species and three Candida species were isolated. Most common organisms in neutropenic patients were coagulase-negative Staphylococcus (CoNS) (22%), Klebsiella species (14%), Escherichia coli (13%), Streptococcus species (10%) and Pseudomonas species (10%). In non-neutropenic patients, CoNS (29%), E. coli (11%), Pseudomonas species (8%), Streptococcus species (7%) and Klebsiella species (5%) were isolated. Twelve glycopeptide-resistant Enterococci (26% of total 47 Enterococcus species) were isolated. Four methicillin-resistant Staphylococcus aureus (14% of total 28 S. aureus) were isolated. Furthermore, 15 extended-spectrum β-lactamase producing Gram-negative bacilli were isolated. Among Gram-negative organisms, more than 91% isolates were sensitive to piperacillin/tazobactam, ceftazidime and ciprofloxacin and higher sensitivity rates (>95%) were recorded in gentamicin, polymyxin B and meropenem. Conclusion: This study highlights an ongoing trend towards Gram-positive organisms causing BSI in cancer patients. The antimicrobial regimens used in our institution are highly effective against commonly isolated organisms. The identification and the antimicrobial susceptibility of the microorganisms causing BSI in cancer patients remain important to develop antimicrobial treatment strategies including antimicrobial guidelines as well as infection control and to prevent the spread of antimicrobial resistance.