Bacterial blood stream infections and antibiogram among febrile patients at Bahir Dar Regional Health Research Laboratory Center, Ethiopia

Bacterial blood stream infections (BSIs) are a common cause of morbidity and mortality. Prevailing data on bacterial species causing BSI and their antibiogram are essential for proper management of patients. A retrospective study was conducted on blood culture results that had been processed from March 2013 to January 2015 at Bahir Dar Regional Health Research Laboratory Center. In January 2015, data on age, sex of patients and bacterial isolates with antibiogram were extracted from registration log book. Blood stream causing bacteria were identified according to standard operational procedure for blood culture. Antimicrobial susceptibility tests were performed according to Kirby-Bauer disc diffusion methods. A total of 561 blood specimens were requested for blood culture. Of these, 220 (39.2%, 95% CI: 35.3-43.4%) blood cultures had aerobic bacterial growth. Gram negative bacterial isolates constituted 115 (52.3%) of the isolated bacteria. Staphylococcus aureus 50 (22.7%), coagulase negative staphylococci 35(15.9%), Klebsiella pneumoniae 35 (15.9%), Escherichia coli 19 (8.6%), Pseudomonas aeruginosa 15 (6.8%) and Acinetobacter species 13(5.9%) were the most dominant isolates. Overall, drug resistance for gram positive bacteria were 7 to 61% and for gram negatives 6.9 to 82.6%. Among the gram positive bacteria, high resistance levels were observed against penicillin (61%) and oxacillin (52.9%). The gram negative bacterial isolates showed 66 to 82.6% resistance to ampicillin, ceftriaxone and trimethoprim-sulfamethoxazole. The present study revealed that bacterial blood stream infections linked with high levels of drug resistance would pose a challenge in treatment of patients with BSIs. Hence, blood culture with antibiotic susceptibility tests could play key role for appropriate treatment of patients with bacterial blood stream infection.


INTRODUCTION
Bloodstream infections (BSIs) cause self-limiting infections to life threatening sepsis and account for significant mortality and morbidity worldwide.
Blood stream infection accounts for 10-20% of all nosocomial infections and is the eighth leading cause of mortality (James et al., 2002).In sub-Saharan countries including Ethiopia BSI is an important cause of illness and death in children, the mortality rate approaches 53% which makes it a significant health problem in developing countries (Mehdinejad et al., 2009).have reported an increased antimicrobial resistance among bacterial isolates causing BSIs (Usha et al., 2007;Kaistha et al., 2009;Kingsley et al., 2013).
In different studies a wide range of organisms have been isolated in BSIs such as Acinetobacter species, Pseudomonas aeruginosa, Escherichia coli, Klebsiella pneumoniae and Neisseria meningitidis.Furthermore, gram positive bacteria such as coagulase negative staphylococci (CoNS), Staphylococcus aureus, enterococci, and alphahemolytic streptococci (Atul et al., 2007;Anu et al., 2010Kavitha et al., 2010).
Blood culture in order to isolate pathogens and determine drug sensitivity of the isolates remains the main stay of definitive diagnosis and management of BSIs (Shahla et al., 2009).Early identification of bacteria causing BSI and their antimicrobial susceptibility is essential for rapid administration of antimicrobial therapy to patients with BSIs.This has shown to improve treatment outcomes (Munson et al., 2003).
In Ethiopia, a few studies documented data on bacterial blood stream infections and antimicrobial resistance profiles of blood stream causing bacterial species (Tizazu Zenebe et al., 2011;Mulat Dagnew et al., 2013;Araya Gebreyesus et al., 2015).However, data on bacterial blood stream infections are not documented in the study area.
Therefore, this study was conducted to determine the bacterial gents and antimicrobial susceptibility profiles of blood stream infections among patients referred to Bahir Dar Regional Health Research Laboratory Center, North West Ethiopia.

Study settings
A retrospective study was conducted on blood culture results that had been processed from March 2013 to January 2015 at the Bahir Dar Regional

Culture and identification
According to the standard operational procedures for blood culture, 5ml and 2ml blood samples were aseptically collected from adults and children, respectively.The vein puncture sites were cleaned with 70% alcohol and dried before collection of blood sample.Collected blood samples were inoculated onto Tryptic Soy Broth (Oxoid, UK) in 1:5 to 1:10 proportions and incubated at 37ºC.
Overnight incubated culture bottles were subcultured onto sheep blood agar, chocolate blood agar and MacConkey agar.Negative blood culture results would be followed till fifth days up by examining the daily before issued results.
Preliminary identification of the isolates was made on agar based on macroscopic colony characteristics.Gram-negative rods were identified by series of biochemical tests such as Indole, Simon's citrate, Urea, Triple sugar iron (TSI), lysine iron, and motility.Gram-positives were identified based on their preference of growth on blood agar plate followed by catalase, coagulase, bacitracin and optochin tests (Wikler et al., 2007).

Antimicrobial susceptibility testing
The antimicrobial susceptibility testing was per-

Quality control
The standard reference strains S. aureus (ATCC 25923), E. coli (ATCC 25922) and P. aeruginosa (ATCC 27853) were used to check the potency of antimicrobial discs, to control drug susceptibility testing procedures and for identification of bacterial species.The absence of bacterial growth in un inoculated media was done by randomly taking the prepared culture media and incubating over nigh to see for any growth.

RESULTS
From March 2013 to January 2015, a total of 561 blood specimens were requested for culture and antimicrobial susceptibility tests.Among these, 289 (51.5%) were from females patients.The median age of patients was 15.5 years with a range of 4 days to 75 years.Overall, 220 (39.2%) of blood specimens had aerobic bacterial growth.Among aerobic culture positives, 203 (92.3%) were monomicrobial and 13 (5.9%)were polymicrobial growth.

DISCUSSION
Studies show that BSIs are frequently encountered by clinicians mainly in developing countries.BSI is one of the major infections for frequent antibiotic use (Vanitha et al., 2012;Mulat Dagnew et al., 2013).In the present study, blood culture was one of the frequently requested specimens for culture and antimicrobial susceptibility tests.This indicates that BSI is a common health problem of the community which could partly explained by 39% prevalence of blood stream infection.
The blood culture positivity rate in this study is higher compared to other studies in Ethiopia which reported 18.2% and 8.8% positivity rate (Tizazu Zenebe et al., 2011;Mulat Dagnew et al., 2013).The isolation rate of bacteria in the present study is also higher than studies reported in other parts of the world like in South India (8.39%), Iran 5.6%, Nigeria 19.3% and 20.02% and 9.44% in India (Usha et al., 2007;Kalantar et al., 2008;Mehdinejad et al., 2009;Ehwarieme et al., 2011;Vanitha et al., 2012;Sumita et al., 2014).The possible explanation for these differences could be differences in age range of patients, administration of antibiotics before blood culture, laboratory procedure, geographical location, seasonal variation and epidemiological difference of the etiological agent (Pitout and Laupland, 2008).
In the present study, gram negative bacteria were more frequently isolated than gram positives.This which is comparable with other studies (Vanitha et al., 2012;Kalpesh et al., 2014;Sumita et al., 2014).Coagulase negative staphylococci (CoNS) have been considered as non pathogens believed that it could be skin flora specially when isolated in a single blood culture.But, their role as pathogens was reported in different studies as an important cause of morbidity and mortality in immune suppressed individuals (Usha et al., 2007;Shahla et al., 2009;Tizazu Zenebe et al., 2011).
The rate of antibiotic resistance in this study is comparatively higher than previous reports in Ethiopia (Tizazu Zenebe et al., 2011;Mulat Dagnew et al., 2013) and other studies conducted elsewhere in the world (James et al., 2002;Amit et al., 2014).
A high prevalence of antibiotic resistance was noticed in this study especially among gram negative bacteria.This might be due to none judicious use of antibiotic in health facilities and easy availability of drugs in the market (Bayeh Abera et al., 2014).
Amongst the gram positive bacteria, high resistance was observed to penicillin (61%) and oxacillin (52.9%) which is almost consistent with a study by Kalantar et al. (2008) that recorded about 41% resistance to oxacillin and 60% for penicillin.Furthermore, high resistance among gram negative was seen against ampicillin (82%), ceftriaxone (68%) and thrimetoprim-sulfamethoxazole (66%) which is concordant with the study finding by Mehdinejad et al. (2009).
In Ethiopia, uncontrolled over the counter sale of antimicrobial agents, mainly for self treatment without health professionals prescription would inevitably lead to emergence and rapid dissemination of antibiotic resistance in the community (Bayeh Abera et al., 2014).

CONCLUSION
This study showed that bacterial blood stream infections are common in all age groups of febrile patients.However, bacterial blood culture positivity rate was higher in febrile children below 1 year than other age groups.Overall, bacterial isolates in blood culture showed high levels of antibiotic resistance against commonly prescribed antimicrobials.
Hence, blood culture with antibiotic susceptibility tests could play key role for appropriate treatment of patients with blood stream infection.

Table 2 .
Frequency of bacterial species isolates from blood culture(Mar 2013-Jan, 2015)

Table 1 .
The distribution of blood culture results by patients' age and sex(Mar 2013-Jan, 2015)

Table 3 .
Antimicrobial resistance profiles of gram positive bacteria from blood cultures (Mar 2013-Jan,

Table 4 .
Antimicrobial resistance profiles of gram negative isolates from blood cultures (Mar 2013-Jan,