Assessing Bacterial Isolates in Bloodstream Infections and Trend of the Antimicrobial Resistance in the Hematological and Solid Malignancies

Introduction: Infection is a common cause of morbidity and mortality in hemato-oncologic patients receiving chemotherapy. The empiric broad spectrum antibiotic given to patients with fever and features of sepsis has reduced infection related complications and shortened hospital stay. However, the use of empirical antibiotic prophylaxis has caused changes in the spectrum of organisms and emergence of drug resistance. We evaluated the type of bacterial isolates and the resistance patterns in cancer patients.

Method: We examined data from cancer patients aged 18 years and older with positive blood cultures from 2012-2014. We estimated the frequency and percentage of blood culture positives bacteria and resistance pattern in hematological and solid malignancy and compared hospital stay and death during admission.

Results: 1334 patients were admitted 2012 to 2014 who received at least one course of chemotherapy. We found 167 positive blood cultures among 122 patients from137 admissions. Of these 122 patients, 72.7% had solid malignancy and 27.3% had hematological malignancy. Patients with hematological malignancy had 81.8% gram positive cultures and 19.2% gram negative cultures compared to 78.4% and 21.6%, respectively for patients with solid malignancies. Out of the gram positives, 22.2% were Staphylococcus aureus and 33.3% were coagulase negative staphylococcus in patients with hematological malignancies as opposed to 17.4% and 15.9% respectively in patients with solid malignancies. Among the gram negative positive blood cultures 17.6% grew Escherichia coli and 27.7% grew Klebsiella in patients with hematological malignancies. These numbers were 35.2% and 44.4% in patients with solid malignancies. 59.9% of culture positive bacteria developed resistance to one or more antibiotics in hematological malignancy group where as 56.9% developed it in in solid malignancy group. The percentage of bacterial resistance to 1, 2 and 3 or more antibiotics in hematological and solid malignancies were 18.8 Vs 21.9, 15.9 Vs 13.8 and 22.7 Vs 21.9 respectively. Percentage of extended-spectrum β-lactamases (ESBL), methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant enterococci (VRE) were 6.6%, 3.6 and 4.7% respectively. Having positive blood cultures was associated with increased length of hospital stay - 56.3% of patients with hematological malignancies spent 10 or more days in the hospital as compared to 48.8% of patients with solid malignancy. More deaths were seen in patients with positive blood cultures with hematological malignancies (15.6%) as compared to patients with positive blood cultures with solid malignancies (14.5%).

Conclusion: We observed that gram positive bacteremia was more common in our patient population. There seems to be no difference in the incidence and pattern of bacteremia between solid and hematological malignancies. Bacteremia is associated with increased length of stay and mortality. More than one third of bacteria are resistant to 2 or more antibiotics. Therefore, the careful analysis of the types of organisms and pattern of antimicrobial resistance of the isolates at each particular institution is important to develop strategy for empiric antimicrobial therapy for patients with febrile neutropnia and treatment of bacteremia.