In this cross-sectional study among diarrheal patients in Gondar teaching hospital, northwest Ethiopia, the overall prevalence of intestinal parasites in stool samples was found to be 36.5%. This finding was consistent with previous study conducted in southwest Ethiopia  and with a report from Yemen . However, our finding was lower compared to the studies undertaken in central Ethiopia and South Africa [21, 22]. These could be due to the differences in hygiene practices of the populations, environmental and host factors. The methods used for detection of the parasites could also attribute to the observed difference.
E. histolytica/dispar was the predominant protozoan parasite (7.3%) isolated from stool of the diarrheic subjects. This report was comparable to the study conducted by Al-Mohammed et al . The occurrences of A. lumbricoides (5.5%), G. lamblia (5%) and S. stercoralis (3.1%) detected in the current study were in agreement with a study conducted in southwest Ethiopia . The rate of protozoan opportunistic infections: C. parvum (1.8%) and I. belli (1.3%) in the present study were low compared with previous study done in central Ethiopia . This discrepancy could be due to the methods used to detect the parasites and/or low rate of those parasites in the study area. However, similar rate of C. parvum was reported in a study done by Lee et al .
The rate of S. mansoni (3.1%) and hookworm infection (1.8%) observed in the study are in line with reports done elsewhere [25, 26]. Similarly, the 1.6% of Hymenolepis species diagnosed in the study was also in accordance with a study conducted in Yemen . Multiple infections with intestinal parasites occurred in 6.3% of patients and this rate was comparable with a report from Nigeria .
Our result revealed that significantly higher parasitic infections were observed in patients who live in rural than those who live in urban area. This difference may occur due to lack of awareness towards general hygiene practices in rural compared to patients who live in urban area. A similar result was also found in a study undertaken in Yemen . With respect to water sources for household consumption, patients who were using well and spring water for daily household consumption had higher rate of intestinal parasites and Shigella species than patients who were using pipe water. This variation may be due to the fact that those water sources were not protected, which pose significant health problems to acquire the infections. Patients who used to wash their hands after visiting toilet either irregularly with soap and without soap or not at all had significant higher intestinal parasites and this finding was consistent with a study conducted in Uganda .
In the study, Shigella species were isolated from 15.6% of the diarrheal patients. This result was consistent with studies done in Kenya and Tanzania where 16% and 14% Shigella isolates have been reported, respectively [29, 30]. However, our finding was lower compared to a 34.6% prevalence of Shigella species isolated from a study done in Awassa, southern Ethiopia . The difference might be due to the nature of the public water supply scheme in the setting which is from Lake Awassa and supposed to be more contaminated than the public water supply system of Gondar town which is a protected surface water system. Similarly, the 1.6% isolation rate of Salmonella species in our report was comparable with previous reports in northwest and northern Ethiopia in which 1% and 2.01% of Salmonella isolates reported, respectively [32, 33].
Antimicrobial resistance to one or more antibiotics was very high among the Shigella species isolated in the study (88%). Multiple resistances (resistance for two up to six commonly used antibiotics) were observed in 80% of the Shigella species isolated. This finding was in line with a study conducted in southern Ethiopia where 82% isolates were found to be multi drug resistant . Other studies from Ethiopia also showed increased antibiotic resistance among Shigella isolates [32, 34, 35]. In the current study, Shigella isolates were resistant to TTC (85%), AMP (80%), SXT (76.7%) and CAF (48.3%) and these findings were comparable with previous studies conducted in Ethiopia [31, 34, 35] and other African countries [36, 37]. Ten percent of the Shigella isolates were resistant to GEN and this result was in agreement with a study conducted in Nigeria . Comparatively high rate of resistance to CIP (8.3%) was observed in the present study as compared to previous report in which 3.1% of Shigella isolates were resistant to CIP . This high resistance rate might reflect the indiscriminate and widespread uses of the antibiotics in public health practices since the society in the setting have easy access to different antibiotics and could buy the antibiotics without prescription . However, 16% and 28.3% of Shigella isolates resistance to CIP were reported in South Africa and Nepal, respectively [22, 40]. The patterns of resistance for the isolated Salmonella species in this study were consistent with previous studies conducted in South Africa, Ethiopia and Mexico [22, 34, 41]. The absence of Salmonella isolates resistance for CIP in the present study suggests that CIP could be used as a drug of choose for treating Salmonella infections in the absence of drug susceptibility test.
The absence of E. coli O157:H7 in our study subjects was comparable with study conducted in Uganda . This absence might be due to the feeding habit of the study population. E. coli O157:H7 strains were first detected following the ingestion of hamburgers in the United States in 1982  and out breaks were occurred in United States relating in acidic foods such as mayonnaise and apple cider have underscored the unusual acid tolerance of this organism [44, 45]. It is worthy to note that, many of the outbreaks that had occurred around the world were more or less related with fast foods like hamburger and acid foods such as apple-cider and mayonnaise, which are not commonly consumed by our study population and inaccessible of these foods to the study subjects. Absence of E. coli O157:H7 also reported from studies conducted in Spain and Italy [46, 47]. On the contrary a single case and 5.4% of E. coli O157:H7 identified from reports done in South Africa and Nigeria, respectively [48, 49].