This study aimed to elucidate the microbiological quality and food safety of bottle food collected from children under five attending three health institutions in Arba Minch, southern Ethiopia. To the best of our knowledge, this study is the first to provide unique insights into the microbial quality and safety of bottle food in the study area. In addition, the study was designed to identify significant differences in contamination versus socioeconomic characteristics, knowledge of food safety, and food safety practices.

The overall findings of this study revealed that 57.3 and 60.5% of the food samples had bacterial counts above the maximum standard values set for TVC and TCC, respectively, and were therefore deemed unacceptable in terms of microbial quality. In addition, approximately 8.6% (n = 19) of the samples contained foodborne pathogens and were considered potentially hazardous if consumed. The overall microbial contamination of baby feeding bottle food in this study was in line with food safety risk highlighted in previous study from Gambia in which contamination ranges from 5 to 70% [14], Kenya (14.4 to 62% of contamination) [19], Nigeria (microbial load ranges from 3.3 to 5.02 log10 CFU/mL [12, 17], Thailand [20], and Bangladesh in which the rate of contamination was estimated as 41% [9, 34, 35] and Ethiopia (contaminations ranges from 14.2% and 31.2%) [16].

The aerobic mesophilic bacteria among baby feeding bottle foods were estimated to be in the range of 1.0 to 8.1 log10 CFU/ml. The finding was in line with the results of previous studies conducted in Ethiopia (7.29 log10 CFU/mL) [16], Nigeria (5.02 log10 CFU/mL) [17], and Korea (2–5 log10 CFU/mL) [18]. This value point out that the baby bottle food in the current study area supported the growth of microorganisms due to a conducive environment [36] suggesting the high risk of microbial spoilage in baby feeding bottle foods particularly cereal blend and fruit juice samples.

On the one hand, the overall mean TVC in the food samples was 5.3 ± 2.3 log10 CFU/mL, which was lower than the findings reported in a couple of studies done in Ethiopia (8.07 log10 CFU/mL) [32], and Thailand (6 log10 CFU/mL in about ten percent of the samples) [20]. In comparison to the study conducted in Ethiopia, the lower count observed in the current study may be partly explained by the time in which these studies were conducted and the improvement in attitude and practice of child feeding practices, while socioeconomic and geographical differences may explain the differences from the study conducted in Thailand. On the other hand, it exceeds the value previously reported in a study done in Brazil [6]. Variations may be attributed to differences in food characteristics, caregiver knowledge and practices, and sociodemographic factors. Our study revealed that about 60.5% of the food samples were potentially contaminated with feces, which is vis-à-vis the results of a series of previously published studies [14, 16, 19, 20]. Moreover, the reported load of microbial contamination was higher than the earlier study done in Korea (2–5 log10 CFU/mL) [18]. The presence of TCC higher than the permissible level set for the acceptable quality standard of ready-to-eat foods has been typically used to measure the effectiveness of disinfection and to indicate the possible presence of enteric bacterial pathogens [37].

Consequently, 59.1% of the food samples in this study with TCC above the maximum allowable limit (> 102) suggest an unhygienic processing of baby feeding bottle food is common in the study area. Furthermore, the finding also suggest the source of contamination of complementary food in baby feeding bottle could be more likely to be feaces contamination as indicated in previous study [8]. However, this observation can also be explained by the fact that improper human practices can cause extrinsic contamination during food processing, handling, and storage or as a result of using contaminated water. In addition, the high level of TCC detected in our study suggests that the equipment and utensils used to prepare and store baby bottle food must be subjected to rigorous hygiene and cleaning procedures.

The proportion of microbiologically unacceptable quality of bottle food using the TCC parameter was 60.5%, and this was lower than the results reported from South Africa (84.6%) [28], Indonesia (88%) [31], and Thailand (66%) [38]. The observed variations in the contamination levels may be attributed to differences in the food type, sample size, the time of the study conducted, laboratory protocols employed, cleaning and disinfection practices, bottle and nipple sterilization practices, sociocultural characteristics, baseline prevalence of foodborne pathogens, seasonality, and geographical location [17].

In the present study, a high proportion (i.e., 79%) of Gram-negative bacteria belonging to the family Enterobacteriaceae contaminated food samples at the point of consumption. The result validates the conclusion of a previous study conducted in Jimma, Ethiopia [22]. The predominant microflora of the food sample in this study was Citrobacter sp., followed by Klebsiella spp. and E. coli. The presence of these bacteria in the samples denotes that the food had been handled and stored in a poorly hygienic manner [25] and could also be linked to cross-contamination in the food processing chain or from food handlers. Furthermore, the higher isolation rates of members of the Enterobacteriaceae family and the Gram-positive Staphylococci (Enterococcus spp. and S. aureus) intimate that bottle food may serve as a vector for the transmission of both pathogenic and opportunistic pathogens. The findings agree with similar studies done in Pakistan [7] and Nigeria [12, 17, 21].

The hygiene criteria tested in this study, such as TVC, TCC, and Enterobacteriaceae, per se, indicate the possibility of fecal contamination of food due to poor hygiene practices, insufficient processing, and storage [6, 15]. Additionally, the findings indicate non-compliance with food hygiene criteria, necessitating corrective actions, such as implementing food safety measures during food production [9, 17, 33].

The higher percentage of contaminated food samples with Enterococcus spp., S. aureus, Salmonella spp., and diarrheagenic E. coli was another significant public health concern revealed in our study [10, 39]. Food contamination, for example, has been identified as a substantial contributor to diarrhea in low-income settings, with up to 70% of diarrheal episodes linked to pathogen-contaminated water and food [11, 15, 21]. Furthermore, the detection of Salmonella spp., S. aureus, and diarrheagenic E. coli in 8.5% of food samples at the time of consumption reflects the magnitude of exposure to the foodborne pathogens among bottle-fed babies in the study settings [10, 34].

In addition, the prevalence of skin and mucosal microflora on baby bottle food samples may indicate contamination by food handlers after preparation or during handling practices [24]. However, the isolation of S. aureus rate in the current study was lower than the results reported from two cities in Ethiopia [22, 37] and Sudan [40]. The results specify the importance of improved hand washing and sterilization of feeding bottles by caregivers. The isolation rate of Salmonella spp. and diarrheagenic E. coli in the food samples was only 1.36% (3/220). However, a higher rate of Salmonella spp. was reported from studies done in other Ethiopian cities, Jimma [22] and Addis Ababa [37]. The low-level detection of diarrheagenic E. coli (1.36%) in food samples in our study is in parity with the results reported from Thailand (1.2%) [38] and Ethiopia (3.7%) [32]. At the same time, it is lower than the results reported elsewhere (61.4%) [41]. However, the detection level of the foodborne pathogens (Salmonella spp. and S. aureus) sharply contrasts with an earlier study [18]. Interestingly, Shigella spp. was not detected in the food samples tested in this study. Similarly, Shigella spp. is not recovered in food samples in other studies conducted in Thailand [38], Ethiopia [37] and Egypt [33, 42]. According to previous study Shigella spp. are not as persistent as Salmonella spp. or are  most likely eliminated during cooking [41, 43]. However, studies from Ethiopia [32], Sudan [40], and India [44] successfully recovered Shigella spp. in baby foods. These fluctuations may also be attributed to differences in the type of food ingredient and food source, the water level of the food, the level of compliance with the standard preparation and handling techniques, and other environmental factors [36].

There is considerable evidence that shows diverse organisms can multiply rapidly on food and are relatively resistant to routine cleansing and disinfection. Therefore, without additional risk-based and decisive measures to improve food hygiene and safety practices, the burden of foodborne disease in children could not be controlled [10, 12, 20]. Accordingly, we identified the type of supplementary food, mothers’ or caregivers’ source of information for food preparation, hand washing practices before food preparation, the type of water used for baby food preparation, the handling of leftover baby food, storage conditions (temperature and duration), as well as sterilization and disinfection of the feeding bottle as critical control points using ANOVA. The observations suggest systematic planning and management of food hygiene practices in the study setting. Furthermore, the identified factors are indicators of the critical control points to implement food safety measures that can reduce exposure risk and improve children’s health outcomes [6, 17, 29, 31].

In this study, after adjusting all the confounding factors, the types of baby feeding bottle food, caregiver hand washing practices before food preparation, and methods of bottle sterilization and disinfection were identified as independent predictors of the microbial quality of home-prepared baby bottle food. The identified factors were broadly consistent with the results of a couple of other quantitative studies done elsewhere [17, 26]. In this study, the TCC on the baby feeding bottle food was found to be significantly related to the types of bottle food [β = 0.4 (95% CI 0.2–0.5), p < 0.001]. The mean TCC in the cereal blends or fruit juice was significantly higher than that of PIF and cow milk by 0.41 log10 CFU/mL. The type of food was also associated with microbial quality (load) in a prior study conducted elsewhere [15]. The current finding shows that babies who consume cereal blend or fruit juice foods in feeding bottles are at higher risk of being exposed to foodborne pathogens than those who use powdered infant formula [18, 34]. The high bacterial count observed in the cereal blends could be attributed to inadequate heat penetration during its preparation or contamination that occurred after cooking from the hands of the caregiver or feeding bottle [18]. The high load of coliform contamination in fruit juice in this study indicates this is a global problem, as several other studies have also revealed the high level of TCC in fruit [8, 9, 24, 35]. In the current study, significantly low levels of coliform bacteria were observed among the foods sampled from caregivers who habitually sterilized the feeding bottles (p < 0.001). The linear regression model results revealed that the TCC increased by 0.7 log10 CFU/mL each time mothers or caregivers did not sterilize or disinfect baby feeding bottles. This observation resembles the results of previous studies done in Nigeria [17], South Africa [13], Mali [10], Kenya [39], Brazil [6], and elsewhere [24]. The finding provides a fascinating insight into the potential control measures for contamination and ensuring food safety in childcare practices [45]. However, studies from Brazil and UK failed to demonstrate the relationship between median TCC versus washing or disinfection practices [6, 46]. Additionally, a previous study could not detect a significant correlation between cleaning methods and bacterial contamination of foods [47].

On the other hand, hand washing by the caregiver or mother before handling and preparing food was associated with a lower risk of contamination [β = 0.8, 95% CI 1.1–0.4). While preparing baby bottle food, every additional hand wash decreases the mean TCC by 0.8 log10 CFU/mL (p 0.0001) (Table 5). The findings confirmed that the protective effect of practicing good hand hygiene during food preparation is a critical control point to reduce the contamination rate [9, 48].

The findings have implications for current baby feeding methods and childcare practices. The high microbiologically unacceptable quality and unsafe food for consumption in supplementary baby food in this study suggest that bottle feeding practice should be considered with all precautions since the food in baby feeding bottles supports the growth of different indicators and pathogenic bacteria. The critical point of baby supplementary food contamination and the pathogens identified in this study should be used for evidence-based decision-making and to improve childcare practices for reducing diarrhea caused by the most common enteric pathogens. Improved bottle feeding practice would include multi-disciplinary action in planning and implementing an effective intervention to prevent and control pathogen transmission through supplementary food. This could be accomplished by improving education about bottle feeding practices. They are promoting alternate feeding methods, better cleaning of utensils, sterilization of baby feeding bottles, and improved preparation techniques by increasing awareness of caregivers and mothers on the microbial quality and safety of supplementary foods and educating them on the best practices of washing, preparation, handling, and storage of supplementary nutrition, as well as the country-wide implementation of microbial monitoring and evaluation of supplementary foods under the principle of hazard analysis and critical control point. The estimates could be used as inputs by government sectors, non-governmental organizations, and policymakers to enforce food safety and childcare regulations. The finding can be used as a baseline for future studies. Large-scale research using molecular techniques would be required to prove the transmission of bacterial diseases from supplementary food via bottle feeding practice. Further work is warranted to provide a complete picture of the extent of the contamination of other types of supplementary foods in the community and to assess the risk of prevalent foodborne diseases. Given that bottle feeding of baby is the common practice throughout low-income countries and the common type of complementary food used is also predominantly similar as it was recommended by the health care professional and WHO guideline, the food safety risk identified in this study can be generalizable for other similar setting especially in low-income countries. In addition to this, food quality and food safety are the priority agenda in reduce child morbidity and mortality. As food microbial contaminations are continued to contribute for the high burden of diarrhea, the finding from this study will interest   the global effort planning in controlling the foodborne disease especially among the most vulnerable group of population such as children less than five years of age.

Although this study covered essential issues, it has some limitations. First, this study relied on self-reported data on bottle handling and hygiene practices, which may have resulted in overestimating positive bottle handling and hygiene practices. The second limitation relates to this study was spectrum of foodborne bacterial pathogens were not studied using molecular techniques and pathogens