Selection of studies
A total of 346 articles searched through the electronic searches of which 86 duplicated articles were excluded. From the remaining 260 articles, 235 articles were excluded after reading of titles and abstracts. One article was removed because of an availability of full text. Finally, 24 full text articles were accessed for eligibility criteria. Based on the predefined criteria and after critical appraisal 18 were included in the final analysis (Figure 1).
Characteristics of included studies
The total of eighteen articles was included in this meta-analysis and systematic reviews that met the inclusion criteria. All the included studies were conducted between 2009 and 2018. They were also published from 2011 up to July, 2019.
The articles those fulfill eligibility criteria for this systematic review and meta analysis were conducted on four regions and in the Federal capital city of Ethiopia, Addis Ababa, but no study on SSI was obtained from other regions (Afar, Benishangul-Gumuz, Gambela and Somali). Five studies at South Nations Nationalities and Peoples of Ethiopia national regional state (SNNP) [16, 17, 27–29]; four studies were conducted in Addis Ababa [15, 30–32]; similarly four studies at Tigray national regional state [33–36]; three studies at Amhara national regional state [37–40] and lastly two study at Oromia regional state[41, 42].
Fourteen of the studies were done using primary data[15–17, 27–34, 36, 37, 41] while the rest were done using secondary data [35, 38, 40, 42]. Most of the studies (16) were done by cross sectional study design and other two done through Co-hort study design (Table 1). Five of the studies were conducted only on women’s who give birth through cesarean section[28, 32, 34, 35, 41] and the other thirteen studies were conducted on patients which undergo different type of surgery.
Quality of studies
The JBI quality appraisal criteria established for cross-sectional and cohort studies were used. Since all the studies that fulfill the eligibility criteria of this systematic review and meta-analysis had got 50% and above, all of them were considered [15–17, 27–38, 40–42].
Pooled prevalence of Surgical site infection in Ethiopia
Pooled prevalence of Surgical site infection rate
The pooled prevalence of Surgical site infection rate in Ethiopia based on CDC criteria was 11.58 (95% CI 9.78, 13.38) (Figure 2). As shown in the forest plot below, substantial heterogeneity was identified (I2 = 82.1; p < 0.001) indicating that the use of random effects models for estimating the pooled estimates is applicable. Moreover, it also suggests the need to conduct subgroup analysis to identify the sources of heterogeneity.
Subgroup analysis was done based on study area (regions), study years and sampling design to identify the possible source of heterogeneity across studies (Table 2). The subgroup analysis result directed that the source of heterogeneity was due to the study area, but not due to sampling design and study years (p < 0.001) (Table 2). According to the result the pooled prevalence of SSI in Amhara and Oromia region was 9.16 and 10.63, respectively.
The sensitivity analysis shown that all of the studies were found within the confidence interval limit, hadn’t an impact on the overall estimation (Figure 3 ).
A funnel plot showed an asymmetrical distribution (Figure 4). Egger’s regression test p-value was 0.007, which indicated the presence of publication bias.
Trim and fill analysis
Due to the presence of significant publication bias through egger test further trim and fill analysis was conducted. As shown in figure 5, this analysis was filled five studies. According to trim and fill analysis, the pooled prevalence of SSI rate was 13%.
Pooled prevalence of culture positive Surgical site infection
Seven studies were included to determine the pooled prevalence and to identify bacterial profile of culture positive surgical site infection. A shown in Figure 6, the pooled prevalence of culture positive SSI infection among patients who develop clinical sign and symptoms of SSI was 80.42% (95% CI 70.86, 89.99)( I2 = 9.4; p >0.05) (Figure 6).
Bacterial profile of culture positive Surgical site infection
From bacterial isolates that cause SSI in Ethiopia, the pooled prevalence of Gram-negative bacteria isolates (60.2%) was higher than that the Gram positive isolates (39.9%) which were obtained from patients who develop SSI. But When we come to each individual isolates, the pooled prevalence of Staphylococcus aureus (28.47%)was higher followed by Escherichia coli(15.93%), Klebsiella species(15.62%), Coagulase-negative staphylococci (CoNs)(8.99%), Proteus species(8.20%), Pseudomonas aeruginosa(7.17%), Entrobacter species (1.94%) and Citrobacter species(1.93%) (Table 3). Although they had very low prevalence, Morganella spp, Enterococcus species, Acinetobacter spp . Providencia stuartii  and Streptococcus spp  were also etiologies of SSI in Ethiopia.
Pooled effect of associated risk factors on SSI
Although in primary studies study variables such as duration of surgery greater than one hour, drinking an alcohol [15, 36], chorioaminities[35, 38, 42], residence [35, 42], previous surgery [15, 27], HIV [27, 35], anemia [28, 32], prolonged labor [28, 34, 35, 38], rupture of membrane >12 hour [15, 28, 32, 34, 35, 42] and duration of surgery > 1hour [15, 27–29, 38, 40] had shown significant association with the SSI, when the odds those associated risk factors of two or more studies become pooled only drinking an alcohol, chorioaminities, residence, previous surgery and rupture of membrane >12 hour were significantly associated with SSI in Ethiopian context.
As shown in Figure 7, patients drinking an alcohol (AOR = 6.28; 95%CI: 2.9–13.3) as compared to those didn’t drink an alcohol; women’s having chorioaminities (AOR = 8.67; 95%CI: 4.63–16.27) as compared to those hadn’t chorioaminities; patients living in rural areas (AOR = 3.10; 95%CI: 1.57–6.14) as compared to those living in urban areas; patients who undergo previous surgery (AOR = 3.94; 95%CI: 1.7–7.17) as compared to those didn’t undergo previous surgery and women’s who had rupture of membrane >12 hour (AOR = 5.29; 95%CI: 2.73–10.25) as compared to women’s who had rupture of membrane < 12 hour were more likely to develop surgical site infection.