Polymicrobial and Multiple Microbiologically Proven Infections in HSCT Recipients

Microbiologically confirmed infections(MCI) which occur during stem cell transplantation(HSCT) increase morbidity and mortality.  HSCT recipients  who develop  polymicrobial or multiple  microbiologically confirmed infections(MMCI)  may be at increased risk for unfavorable outcomes, yet data is limited.  Herein we report the incidence, risk factors and survival associated for polymicrobial and multiple microbiologically confirmed infections (MMCI) in  901 HSCT recipients.   

Electronic databases were used for HSCT recipients treated at Northwestern Memorial Hospital between 2004-09.  Infection data was recorded from the time of admission through discharge. Any single CONS or VRE BAL culture was excluded from analysis. Patients received acyclovir, azole antifungal, and  flouroquinolone for prophylaxis.  Polymicrobial infection was defined as the occurrence of 2  MCI’s from different organisms within 72hours of the 1^stpositive culture. Fischers Exact test and Chi-Square was used for analysis of continuous and discreet variables. This study is IRB approved.

 Amongst  905 HSCT recipients, 59 patients(6.8%) developed MMCI’s. Polymicrobial  infection was identified in 30(3.4%) patients.  17 patients had > 2MCI’s. Most  MCI’s(55%) were blood stream infections. The duration of time which transpired between positive cultures was as follows: Concommitant cultures (n=13),<24h(n=9),48hr(n=8),<72hr(n=5),< 96hr(n=4), <120hr(n=3), <144hr(n=5), >7days(n=12).    When  MMCI’S cases were compared to patients without any positive cultures using bivariate   analysis,  statistically significant differences included : female gender(0.0377), diagnosis of myeloma(p<0.0133 ) or AML(p<0.0497), receipt of  allo-HSCT(p<0.0001),  vancomycin(p<0.0004)or cefepime(p<0.0005) use,  and positive VRE surveillance cultures(p<0.0001) . When MMCI cases were compared to single MCI cases, significant differences included: female gender (p<0.0349), receipt of allo-HSCT(p<0.0373),  vancomycin(p<0.0012) and cefepime(p<0.0009) use. There was no difference in the number of patients who experienced neutropenic fever between MMCI, MCI(p<0.275) or culture negative cases(p<0.1247)0. Strept mitis or C.difficileinfection occurred concommitantly or preceded the second MCI in 29(47%) cases.   Overall mortality was significantly higher in MMCI cases when compared to cases without any positive cultures(p<0.001) or  patients with a single MCI(p<0.0197). There was no difference in overall  mortality for patients who developed MMCI <72hours(polymicrobial) versus MMCI>72(non-polymicrobial;P<0.2990).   

MMCI are an infrequent but serious cause of  adverse events which occur during HSCT. Patients who are at high risk for developing MMCI require increased vigilance and early aggressive antibiotic therapy.