The awareness of bacterial contamination among blood products which are used for blood transfusion as well as their sources of contamination is imperative for setting up the preventive measure at blood bank centers and blood transfusion centers. Moreover, it is significant to offer action and improve the blood collection practice, education and policy.
In our study, the overall prevalence of bacterial contamination among blood products was 4.5% (N = 17/376). Blood group type O + 35.3% (N = 6/17,) showed the most contaminated one. Studies from Debre Markos, Ethiopia carried out by Esmael A et al  also agreed with this study.
The prevalence of bacterial contamination among those blood products which were collected with non-diverging donor blood collection method was 7.4% (n = 14/188) and almost close to previous studies reported from Africa countries like Ghana by Adjei A A et al 9% (n = 28/303)  and Nigeria by Bolarinwa R A et al 8.8%, (n = 14/162) . The bacterial contamination of blood products collected with diverging done in this study is more or less similar to another finding like in Malaysia carried out by Jumaah N et al was 1.7% (n = 12 /702) .
Among the blood products, the highest bacterial contamination was observed in whole blood and PRBC. Another study was done in Ghana by Adjei A A. et al also supported that whole blood became the first to be contaminated in equal proportion except that PRBC is not included in their study .
The isolated bacteria in this study were both gram-positive bacteria (Staphylococcus aureus, Staphylococcus epidermidis, Listeria monocytogenes, and Listeria species) and gram-negative bacteria (Klebsiellae species, Proteus mirabilis and Pseudomonas aeruginosa). Our finding was agreed with different studies like in Nigeria by Bolarinwa R A et al  and India conducted by Barot T et al .
However, our finding was lower than studies done in Debre Markos, Ethiopia 12.5% ( n = 15/120) ( and Gondar 15.3% (n = 21/137)  and also in Ghana 16.5% (n = 16/97) , 17.5% (n = 14/80) , this difference may be due to the difference in sample size, sample taken from only whole blood, the present study on the other hand higher in prevalence of bacterial contamination than other studies done in Zimbabwe 3.1% (n = 6/196) , Uganda 3.5% (n = 18 /510) . The reason for increased prevalence may be in our countries the disinfection type is focused on application of 70% alcohol only.
The prevalence of bacterial contamination in the diverging method of the current study is higher than different countries finding such as New zealand done by Dickson M and Dinesh D was 0.04% (n = 2378/59461) . The difference may be the implementation of a compressive activity like proper donor screening, double disinfection, closed processing system and the existence of national haemovigilance programme in New zealand.
From this study; when we compared the bacterial contamination between blood donor collection methods of blood and blood components, the non-diverging method was higher than the diverging method one. In addition, the calculated adjusted odd ration became 7.8 so that the non-diverging blood donor collection method was likely more exposed to bacterial contamination by 7.8 times than diverging one.
Those blood products which were collected in both method share same conditions like application of single disinfection method, the absence of bacterial contamination screening and active national haemovigilance programme except changing the direction of the first 30–40 ml of blood into the diverging pouch. So, switching the first flow of blood reduced the contamination rate by 5.8%. This concept is also supported by the reviewed study in Italy by Liumbruno G M et al. The purpose of diverting the first 40–50 ml of donated blood to reduce the microbes or skin fragments especially comes from donor skin entering into the collection bag . In addition, other study in Japan by Satake M et al also maintained that the positivity rate of bacterial contamination were 36/21786 (0.17%) and 11/21783 (0.05%) without and with diversion method in that order. Even if this study done in platelet concentrates only, used different methodology, sample volume and include anaerobic bacteria detection .
As opposed to the current study, a study done in Zimbabwe by Makuni N et al the finding of the highest contaminated among blood products was platelet 10.3% (n = 4/36) followed by PRBC 1.3% (n = 2/149). There was no unit of whole blood was contaminated by bacteria. The difference may be they took unequal amount of from each blood products by Makuni N et al .
Considering the drug resistance pattern, the finding s of this study was agreed with a study from Nigeria and they also reported that gram-positive bacteria were sensitive for Gentamicin and Ceftriaxone but the majority of the antibiotics were resistant . The only antibiotic that showed resistant to the Pseudomonas aeruginosa was Gentamicin. Majority of the antibiotics were sensitive for Klebsiella spp and Proteus mirabilis. But a study from Debremarko indicated that all the gram-negative organisms isolated were resistant to Cotrimoxazole and susceptible to Ciprofloxacin and Cefoxicitin . The levels of Multi drug resistant for one grouped drug spectrum (MDR ≥ 2 drugs) were 5(29.4%). In our study gram-positive bacteria showed MDR for chemically different drugs. Our finding was lower than Study done here in Gondar (66.7%), Ethiopia by Wondimu H et al .
In conclusion, our study showed that the prevalence of bacterial contamination of stored blood products was higher in those collected with non-diverging method than diverging one. So, there was a difference between diverging and non-diverging blood collection method. Furthermore, Staphylococci epidermidis became the most commonly isolated bacteria. A considerable level of resistant bacteria and MDR organisms were observed. Therefore, blood bank should improve blood donor collection method from non-diverging to diverging method.
This study couldn’t identify anaerobic bacteria.