gms | German Medical Science

Background: While antibiotic resistance is increasing worldwide, the epidemiology of multiresistant organisms (MROs) within specific immunocompromised patient populations is poorly described.

Aims: To describe the epidemiology of MROs isolated during episodes of bacteraemia in patients with a haematological malignancy or haematopoietic stem cell transplant (HSCT) at a quarternary hospital in Sydney, Australia over a 24-month period.

Methods: A retrospective review of microbiology databases was undertaken to identify positive blood cultures from patients admitted under a haematologist with a haematological malignancy or HSCT between January 1 2012-December 31 2013 at Westmead Hospital, Sydney, Australia. Haematology and pathology databases were accessed for patient information, diagnoses, HSCT status, microbiological data and admission dates. CDC/NHSN bacteraemia definitions were applied. Instituitional ethics approval was granted. SPSS v21 was used for analysis.

Results: 150 patients had at least one positive blood culture, 92 males (61%) and 58 females (39%). The most frequent haematological diagnosis was acute myeloid leukaemia (AML, 64, 43%) followed by non-Hodgkins lymphoma (28, 19%). The majority of patients with bacteraemias had received HSCT (allogeneic 75 (50%), autologous 19 (13%), nil HSCT 56 (34%)). The median age at first positive blood culture was 57.0 years (25^th percentile 41.2, 75^th percentile 6.1, range 18.6-88.6 years).

There were 154 episodes of infection with bacteraemia, including 42 (27%) with polymicrobial infection, and 67 episodes of contamination. Within infection, there were 91 Gram negative organisms, 93 Gram positive organisms and 9 Candida non-albican species identifid. The most frequent pathogens were E. coli (n=34), P. aeruginosa (n=18), low-pathogenic Streptococci (n=33), coagulase negative staphylocci (n=22), S. aureus (n=15) and enterococci (n=15). MROs were identified in 23% of all bacteraemia infection episodes : 9 MRSA, 1 VISA, 10 VRE (all E. faecium Van B), 14 ESBL (7 E. coli, 4 P. aeruginosa, 2 K. pneumonia, 1 Enterobacter) and 1 carbapenemase producing P. aeruginosa. MROs had increased from 18% to 29% of all bacteraemic infections between 2012 and 2013 (p=0.1). The following factors were associated with MRO bacteraemia compared to bacteraemia without MRO: diagnosis with acute leukaemia (ALL 41%, AML 27%, other diagnoses 14%, p=0.03) and MRSA colonization (63% and 21%, p=0.006). Colonization with multi-resistant Gram negatives (MRGN) or VRE were not associated. Following multivariate analysis, the adjusted RR for ALL was 4.5 (1.3-15.3), AML was 1.9 (95% CI 0.8-4.7), and MRSA colonization was 5.5 (1.2-25.4) (p=0.002). Bacteraemia with a MRGN reduced mortality at 30 days (73% and 86%, HR 3.2 (1.3-7.9), p=0.007) but did not alter the risk for ICU admission; other MROs did not alter outcomes.

Conclusion: MROs were identified in 23% of all bacteraemic infections in patients with haematological malignancy or HSCT. Presence of acute leukaemia and MRSA colonization were associated with MRO bacteraemia. Ongoing surveillance and further assessment of predictive risks factors are required.