Bread sold in Ouagadougou shows widespread contamination from post-baking handling

Bread sold in the capital of Burkina Faso is frequently contaminated with bacteria after it leaves the oven, according to a study that tested loaves from bakeries and street vendors in Ouagadougou and audited hygiene conditions at one of the city’s largest industrial bread producers. The research, published in the journal Food Safety and Risk, found that nine out of ten loaves exceeded acceptable limits for Staphylococcus species and that presumptive Salmonella was detected in more than a quarter of samples, with all positive cases coming from street vendors.

The study was conducted between March and September 2022 at the Laboratory of Microbiology of the Food Technology Department at the Institute of Research in Applied Sciences and Technology in Ouagadougou. Researchers collected thirty bread samples from seven sites across the city using a randomized approach. Twenty-four samples, or eighty percent, came from bakeries and their associated shops and kiosks, while six samples, or twenty percent, came from street vendors operating along the national highways RN1 and RN2. The researchers note that this distribution reflected the relative accessibility of each type of sales point during the sampling period, since bakeries were more numerous while street vending of bread was practiced by a more limited number of vendors.

Samples were collected aseptically, placed individually in sterile stomacher bags, transported under refrigeration with ice packs, and analyzed the same day. In the laboratory, twenty-five grams of each bread sample were suspended in buffered peptone water and homogenized to prepare decimal dilutions. The team used the pour plate method to enumerate six groups of microorganisms: total aerobic mesophilic flora as a general hygiene indicator, total coliforms, thermotolerant coliforms, yeasts and molds, Staphylococcus species, and Salmonella species. Each analysis followed a corresponding international standard, including ISO 4833-1 for the mesophilic flora, ISO 4832 for coliforms, ISO 21527-1 adapted for yeasts and molds, ISO 6888-2 for staphylococci, and ISO/TS 6579-2 for the three-step Salmonella detection procedure involving pre-enrichment, selective enrichment in Rappaport Vassiliadis Soy Broth and Mueller-Kauffmann Tetrathionate-Novobiocin broth, and final isolation on Salmonella-Shigella and Xylose Lysine Deoxycholate agar.

Microbiological quality was judged against reference values from a 1979 French ministerial decree and the French Bakery and Pastry Good Hygiene Practices Guide, which use a three-class sampling plan. Under this scheme, a value below the threshold m is considered satisfactory, a value between m and M is marginally acceptable, and a value above M is unacceptable or potentially hazardous. The results were striking in their unevenness. No samples were non-compliant for total aerobic mesophilic flora or for yeasts and molds, suggesting that the basic baking process itself was not the problem. In contrast, fifteen samples, or fifty percent, were non-compliant for total coliforms, and twelve samples, or forty percent, were non-compliant for thermotolerant coliforms, a group that includes fecal indicator bacteria.

The pathogen indicators were more alarming. Staphylococcus species exceeded the maximum acceptable limit in twenty-seven of the thirty samples, a ninety percent non-compliance rate, with only one sample rated satisfactory and two rated acceptable. Counts ranged from ninety to twenty thousand colony-forming units per gram. Presumptive Salmonella species was detected in eight samples, or 26.7 percent. Two of these came from bakeries, while six came from street vendors, meaning that every one of the six street-vendor samples tested positive for presumptive Salmonella. Statistical comparisons showed that total coliforms, thermotolerant coliforms, Staphylococcus species, and Salmonella detection were all significantly higher in street vendor samples than in bakery samples, with p values of 0.003, 0.004, 0.03, and less than 0.001 respectively. Total aerobic mesophilic flora, which ranged from eight thousand to three hundred thousand colony-forming units per gram, and yeasts and molds showed no significant difference between the two retail settings.

The authors interpret these patterns as evidence of recurrent post-processing contamination rather than a failure of baking. Freshly baked bread is generally considered microbiologically safe because its low water activity and the high temperatures reached during baking eliminate most pathogenic microorganisms. However, once bread leaves the oven it passes through cooling, slicing, packaging, transport, and display, stages at which it can be re-exposed to contaminated hands, surfaces, water, dust, and insects. The study argues that the presence of microorganisms in the finished products is more plausibly linked to this post-processing exposure than to survival of the heat treatment, and describes the situation as a breakdown in post-lethality hygienic barriers.

To identify where contamination enters the chain, the researchers carried out a diagnostic of prerequisite programs, the foundational hygiene requirements that underpin food safety management systems, at a single industrial bread production unit selected as a case study because it represents the largest bakery chain operating in Ouagadougou. The assessment used the framework of the Canadian Food Inspection Agency’s Food Safety Enhancement Program, which organizes requirements into five domains: premises; transportation, receiving and storage; equipment; personnel; and sanitation and pest control. Each of the applicable criteria was rated through direct observation, examination of documents and records, and staff interviews on a scale from full compliance to no implementation, with non-applicable criteria excluded from scoring.

The production unit achieved an overall compliance score of 65.2 percent, calculated as 535 of a possible 820 points across forty-one applicable criteria, indicating a moderate level of implementation. Equipment, at 91.67 percent, and premises, at 77.63 percent, were the best-controlled domains, followed by transportation, receiving and storage at 75 percent and sanitation and pest control at 68.75 percent. The personnel domain was by far the weakest at 27.5 percent compliance, with eight of its ten criteria rated at the two lowest implemented levels. The most critical deficiencies included the absence of any water-potability analysis, the lack of staff training in food hygiene and good manufacturing practices, and the absence of a procedure requiring employees to report transmissible illnesses. Major deficiencies also included inadequate personal-hygiene and wound-covering policies, the lack of a documented cleaning and sanitation program, and weaknesses in pest control.

The authors draw connections between these operational gaps and the contamination profile of the bread, while stressing that the relationship is associative rather than causal. The absence of a personal hygiene policy and of measures to exclude ill staff or cover wounds may help explain the very high prevalence of Staphylococcus species, bacteria commonly carried on the skin, in the nasal cavities, and on the hands of food handlers. The lack of water potability monitoring and of a formal cleaning program could plausibly contribute to the elevated coliform counts. The study also places its findings in a wider context, noting that Staphylococcus aureus is a major foodborne hazard in Africa, with reported average contamination rates of 27.8 percent in raw foods and 25.1 percent in ready-to-eat foods, and that a study of bread in Alexandria, Egypt linked staphylococcal contamination to the non-use of gloves and the display of bread outside shops.

The researchers are careful to state the limitations of their work. The sample size was modest at thirty loaves, the split between bakery and street vendor samples was unequal at twenty-four versus six, and the presumptive Salmonella findings were not confirmed biochemically. The prerequisite program assessment covered a single production unit, so it may not capture the diversity of practices across the bakery sector, and the street-vendor category was small enough that its one hundred percent presumptive Salmonella rate should be read with caution. Nevertheless, the convergence of inadequate staff hygiene, insufficient sanitation, and absent water quality control points, in the authors’ view, to a systemic failure of fundamental food safety barriers rather than isolated lapses. Given that daily bread consumption in Burkina Faso is estimated at about six hundred thousand loaves, with Ouagadougou accounting for nearly half, even occasional contamination events could affect a large number of consumers. The team calls for strengthening prerequisite programs, particularly around personnel hygiene, sanitation, and water quality control, and for further studies involving a broader range of production sites and larger, more balanced samples to better characterize contamination pathways and inform targeted food safety interventions.

Subject of Research: Microbiological contamination of bread sold in Ouagadougou, Burkina Faso, and hygiene deficiencies along its production chain

Article Title: Microbiological quality of bread and identification of critical contamination points along the production chain in Ouagadougou, Burkina Faso

Article References: Ouédraogo, N., Samandoulougou, S., Ibrahim, H. B., Koalaga, J. P., Bouda, S. C., Dembélé, R., & Barro, N. (2026). Microbiological quality of bread and identification of critical contamination points along the production chain in Ouagadougou, Burkina Faso. Food Safety and Risk, 13(1), Article 43. https://doi.org/10.1186/s40550-026-00163-z

Image Credits: AI Generated

DOI: 10.1186/s40550-026-00163-z

Keywords: food safety, bread, microbiology, Ouagadougou, Burkina Faso, Salmonella, Staphylococcus, coliforms, street food, prerequisite programs, post-baking contamination, hygiene practices