Survey of Enteric Pathogens Causing Bacteremia in Cancer Patients

1Dietary Supplement and Probiotic Research Center, Alborz University of Medical Sciences, Karaj, IR Iran 2Department of Microbiology and Immunology, School of Medicine, Alborz University of Medical Sciences, Karaj, IR Iran 3Department of Nursing, School of Nursery and Midwifery, Alborz University of Medical Sciences, Karaj, IR Iran 4Nursing and Midwifery Care Research Center, Tehran University of Medical Sciences, Tehran, IR Iran 5Educational Supervisor Cancer Institute, Imam Khomeini Hospital, Tehran University of Medical Sciences, Tehran, IR Iran 6Department of Oncology, Madani Hospial, Alborz University of Medical Sciences, Karaj, IR Iran 7Vice-Chancellor Office, Alborz University of Medical Sciences, Karaj, IR Iran


Background
One of the most serious medical complications causing significant morbidity and mortality among cancer patients is bacteremia (1,2).Therefore, rapid diagnosis of this kind of bacterial infections can lead to better treatment; as a result, the morbidity and mortality of patients will decrease.Many investigations have reported that among blood born infections, gram-negative bacteria are associated with more mortality than gram-positive bacteria (3,4).On the other hand, many scientists also report that the causative agents of bacteremia are changing (5,6); therefore, obtaining a better understanding of the spectrum of pathogens causing bacteremia is vital for prompt treatment.

Objectives
The aim of this study was to determine the burden of enteric pathogens causing bacteremia among cancer patients in Cancer Institute, Imam Khomeini Hospital, Tehran University of Medical Sciences, Tehran, Iran and Shahid Kamali Hospital, Karaj during April 2013 to October 2013.

Patients and Methods
All patients with various kinds of cancer and different types of chemotherapy/radiotherapy prescribed by attending physicians were enrolled in this study after written informed consent.The study proposal was approved by the Ethical Committee of Alborz University of Medical Sciences.From most of the patients, two 10 ml blood samples were withdrawn under aseptic conditions.The blood specimens were added to the blood culture bottles and incubated at 37°C.The bacterial isolates from these samples were identified by routine biochemical reactions (7).

Results
During the study period (April 2013 to October 2013), 57 and 11 blood samples from cancer patients were taken from Cancer Institute, Tehran and Shahid Kamali Hospital, Karaj, respectively and analyzed for bacteremia; overall, 68 cancer patients participated in this study; of which, six were female (8.82%) and 62 were male (91.18%); ages ranged from under 40 year to 85 years (mean, 63 years).
Gastro-intestinal cancers and cancers of head and neck were the most frequent cancer types in the studied group, accounting for 51 (75%) and 15 (22.1%) cases, respectively (Table 1).The mean weight of patients was 69.18 Kg (range: 49-100 Kg).Similarly, the mean length of hospital stay was 8 days (range: 4-12 days).Positive blood cultures were detected in only 12 (17.65%)and 11 (91.7%)blood specimens from the Cancer Institute, Tehran, compared with one (08.33%)from Shahid Kamali hospital, Karaj.
From these patients, 15 bacteria were isolated; E. coli alone outnumbered other species and accounted for 33.33% of episodes of bacteremia (Table 2).

Discussion
Bacteremia among cancer patients has considerable impact on health care costs (4).In our study 17.65% of all blood cultures yielded positive results; of which 08.33% were from Shahia kamali hospital.This low rate can be explained by the fact that most patients probably received clinical care (and antibiotic therapy) from Tehran which is very close to Karaj City.In an another Iranian study (8)the rate of positive blood culture among cancer patients was 23.5%, in contrast to the findings of the present study; however, also a high rate of positive blood cultures were seen in Meidani et al. study (9).Studies from the neighboring countries report that the rate of positive culture is more than our study (10,11) which could probably be because of different healthcare and sanitation systems.
Like other microbial systemic infections, the rate of bacteremia increases with age, decreasing immune system response, consuming specific antimicrobial drugs and is influenced by a variety of factors.For example, our study also reports that bacteremia is significantly more frequent in males than in females which is consistent with another study (6).Like other studies from Iran, the most common type of cancer in our study was gastric cancer (12,13).
In our study, E. coli was recovered most frequently from blood cultures which is consistent with other studies from Iran (14,15).Of interest, S. aureus, B. cereus and K. pneumonia were also found with the same frequency (20%).Although our study revealed that B. cereus accounted for 20% of the isolated bacteria which is a relatively uncommon cause of blood stream infections among cancer patients; recently, many investigations reported that B. cereus has emerged as one of the 'new' Gram-positive pathogens causing serious infections in cancer patients particularly among neutropenic patients (16,17).
In conclusion, our investigation revealed that cancers of GI tract are the most common cancer types causing bacteremia and also we identified that most common bacteria causing bacteremia in Cancer Institute, Tehran and Shahid Kamali Hospital, Karaj, are E. coli and S. aureus.

Table 1 .
Demographic Characteristics of Cancer Patients with Bacteremia