Multidrug-resistant bacterial infection becomes a real threat in developing countries including Ethiopia. In the study area the majority of pathogenic bacteria isolated from various clinical specimens such as wound, urine, stool, ear and urethral discharge were drug resistant.
In the present study, Gram negative bacteria were the dominant isolates similar to previous studies in other areas of Ethiopia [14,15,16,17] and elsewhere . However, S. aureus was the most frequent isolate followed by E. coli, P. aeruginosa and Salmonella spp. This trend agrees with reports of other studies in Ethiopia [14,15,16,17]. The possible reason for the high frequency is that majority of these isolates are normal flora on skin and gut of healthy individuals. When they get breach on skins and soft tissues and displaced from their resident to other sterile sites they can easily disseminate. Moreover, most of these bacteria are commonly found in the hospital environment which might increase the proportion of wound, ear and urinary tract infection and cross contamination among admitted patients.
The high proportion of S. aureus followed by P. aeruginosa in wound infection in this study might be because of endogenous source of infection or contamination from the environment such as contamination of surgical instruments with the disruption of natural skin barrier as these bacteria are a common bacterium on surfaces, easily finds their way into wounds . Moreover, the high frequency of P. aeruginosa in ear infection could be related to the ability of P. aeruginosa to survive in competition with other organisms and resist antibiotics.
In this study N. gonorrhoeae was most frequently isolated in patients with the age groups of 15–18 years compared to other age groups. This is in agreement with a study done in other part of Ethiopia . This might be because individuals at this age are key populations of higher risk for sexually transmitted infections like gonorrhea acquisition or transmission. Hence between these ages young individuals undergo transition in life style, maturity and legal rights which will place them at different vulnerabilities at different time points.
Salmonella and Shigella spp. were the most common isolates in stool in children less than 5 years of age, which is in line with studies conducted in Ethiopia  and China . It is true that children with in this age group are more susceptible to shigellosis and salmonellosis primarily because of lack of resistance, previous exposure to infections, poor personal hygiene and higher exposure to contaminated environments.
In this study, overall high levels of resistance were demonstrated against amoxicillin, clindamycin, erythromycin and penicillin. These were consistent with resistance rates obtained from previous studies in Ethiopia [6, 16] and India . However, majority of bacteria isolates revealed lower levels of resistance against ciprofloxacin, ceftriaxone, norfloxacin and chloramphenicol. Moreover, Gram positive bacteria showed high levels of resistance (82.1–98.5%) to ampicillin, gentamicin, cotrimoxazole, amoxicillin, penicillin and clindamycin. This finding is similar with studies carried out in Ethiopia  and India  where 75–100% resistance to the above antibiotics reported. Similarly, S. aureus isolates revealed high levels of resistance (81.3–96.8%) to the above mentioned antibiotics. These results are in agreement with the reports from Ethiopia and other countries [6,7,8,9, 17, 22].
In the present study, N. gonorrhoeae isolates revealed 100% resistant to ciprofloxacin, norfloxacin and tetracycline. This agrees with studies carried out in Ethiopia [19, 24], Uganda , Port Elizabeth  and Iran . This might be because of easy availability, over and indiscriminate use of these drugs outside the hospitals. In contrast, N. gonorrhoeae exhibited low level of resistance to ceftriaxone. This was coherent with reports of other studies elsewhere [19, 24, 28, 29].
In the present study Salmonella spp. showed high levels of resistance (85.7–100%) against amoxicillin and ampicillin. These were consistent with previous studies done in Ethiopia [6, 20, 30] and Madagascar . In the current study, it was found that Shigella spp. revealed high level of resistance to cotrimoxazole (100%). This was in agreement with reports from other studies [6, 31,32,33,34]. This might be due to the indiscriminate drug prescription by clinicians in the study area since culture and susceptibility testing were not employed in the previous years.
In the present study, E. coli was the most frequently isolated bacteria in urinary tract infection and a common isolate in bacteremia. This shows that urosepsis is a major cause of infection. Majority of E. coli resisted the antimicrobials gentamicin and tetracycline. A similar result was documented from other studies [16, 35].
In the case of P. aeruginosa, high level of resistance (87.5%) to gentamicin and considerable level of resistance (57%) to tetracycline were recorded. This was consistent with studies conducted in other parts of Ethiopia [7, 15]. However, the rate of resistance of P. aeruginosa against gentamicin is different from other studies [9, 15, 16]. On the other hand, P. aeruginosa was 100% susceptible to ceftriaxone and norfloxacin. A similar result was documented from other studies [8, 14].
The overall MDR (two and above drugs tested) of the isolates in this study was 76.1% which was coherent with studies conducted in other parts of Ethiopia [3, 14] where 63.3–85% MDR rate was reported. In this study, 85% of Gram positive bacteria (S. aureus, S. pyogenes and S. pneumoniae) demonstrated MDR. This was similar with the 77 and 65.2% MDR rate documented for these bacteria in Ethiopia [23, 35]. However, it was lower than 98.6 and 100% MDR reported in other places of Ethiopia [7, 36]. The possible explanation for such disparity might be difference in type of organism isolated, study population, antimicrobial prescription pattern, study area in terms of laboratory infrastructure, infection prevention practices and up to-date knowledge of clinicians on AMR . About 90% of S. aureus also became MDR of which 12% were resisted to seven drugs tested.
The overall MDR rate of Gram negative bacteria tested for seven types of drugs was 68.5% in this study. This finding is higher than studies conducted in other parts of Ethiopia where 51–59.3% MDR Gram negative bacterial isolates from different types of infections were reported [23, 32]. This might be due to the drugs having been in use for much longer time.
Concerning species specific MDR profiles, Salmonella and Shigella spp. showed MDR, 88 and 60%, respectively. This was consistent with previous studies done in Ethiopia [6, 20, 30, 32, 33] and Madagascar . It was also found that 61.5% of E. coli was MDR. A similar result was documented from other studies [16, 35]. However, Godebu et al. documented 23.3% rate of MDR E. coli in Ethiopia. In the case of P. aeruginosa, 75.9% was MDR. This was consistent with studies conducted in Ethiopia [7, 15] where 100% MDR rate reported. Lastly, 62.5% of gonococci isolates in the present study revealed multidrug-resistance that needs further large scale study on antibiogram of N. gonorrhoeae to control the alarming spread of N. gonorrhoeae and other pathogenic species.
Because of retrospective nature of the study, detail information on patient profiles could not be obtained. For some of the pathogen and antibiotic combination, numbers tested were small and this limits the interpretation of the data. Furthermore, anaerobic bacteria were not isolated due to limited laboratory infrastructure.