The research focused on children under five years of age, the group in which Campylobacter infections hit hardest. In this age band, diarrheal disease remains a major contributor to illness and death worldwide, and Campylobacter jejuni is frequently implicated alongside better-known culprits such as Salmonella and pathogenic Escherichia coli. Infection typically produces fever, abdominal cramps and bloody or watery diarrhea, and while most cases resolve on their own, severe episodes in malnourished or very young children can demand antibiotic treatment. That is precisely where resistance matters most: when clinicians in resource-limited hospitals must choose a drug empirically, without laboratory guidance, the local resistance landscape determines whether a child recovers quickly or deteriorates while ineffective therapy is administered.

To capture that landscape, the team collected stool samples from children under five presenting with diarrhea at six hospitals in Sana’a: Al Zahrawi Hospital, Algamohory Hospital, Alkowit Hospital, Al-Sabeen Hospital, Al-Thowraha Hospital and Ibn Khaldun Hospital. Samples were processed using culture methods optimized for Campylobacter, a fastidious organism that requires reduced oxygen, elevated carbon dioxide and selective media to grow reliably in the laboratory. Isolates were then subjected to antimicrobial susceptibility testing following standards set by the Clinical Laboratories Standards Institute, using Mueller-Hinton agar as the testing medium. In parallel, the researchers turned to molecular identification, sequencing the 16S rRNA gene, a slowly evolving component of the bacterial ribosome whose sequence serves as a molecular fingerprint for species-level identification, and constructing phylogenetic trees to compare their isolates with reference strains held in international databases.

The headline number from the study is a prevalence of 2.8 percent, with 11 of 389 children testing positive for Campylobacter jejuni. That figure may appear modest, but in the context of a single-city hospital survey of a pathogen that is notoriously difficult to culture, it represents a meaningful baseline for a country that has lacked systematic campylobacteriosis surveillance. The researchers also broke the results down by demographic and behavioral factors, and the patterns that emerged read like a map of transmission routes. Prevalence was higher among girls, at 3.5 percent, and among children aged 36 to 47 months, where it reached 6.2 percent. Children living in rural areas showed a prevalence of 3.5 percent, and infections clustered in the summer months, when 7.2 percent of sampled children in that season carried the bacterium.

The behavioral and environmental associations were particularly telling. Children who had contact with animals showed a prevalence of 4.3 percent, those who drank water from tap sources 5.6 percent, and those who consumed unpasteurized milk 3.7 percent. Each of these routes is well established in the international literature: Campylobacter jejuni colonizes the intestines of poultry, cattle and other animals without making them sick, contaminates water supplies through fecal shedding, and survives in raw milk, where even small doses can cause infection. In Yemen, where household animal keeping is common, municipal water treatment is inconsistent, and unpasteurized dairy remains part of traditional diets, these findings point to concrete, actionable interventions, from hand hygiene after handling animals to water treatment and safer food handling practices.

The antimicrobial results are the study’s most consequential contribution. The isolates displayed high resistance to macrolides, the drug class that includes erythromycin and azithromycin, which are internationally regarded as first-line treatments for severe campylobacteriosis, especially in children, for whom fluoroquinolones are often restricted. High resistance to aminoglycosides was also documented. Macrolide resistance in Campylobacter is particularly worrying because it arises through mutations in the ribosomal target and, once established in a population, tends to persist and spread. In many high-income surveillance systems, macrolide resistance in human Campylobacter isolates remains comparatively low, so the pattern observed in Sana’a signals a local treatment crisis: the drugs most likely to be prescribed for a sick child may simply not work.

By contrast, the isolates remained relatively susceptible to several other agents, with resistance recorded at 18.2 percent for ciprofloxacin, 27.3 percent for tetracycline and 27.3 percent for nalidixic acid. While these figures still represent substantial resistance by global standards, they suggest that, at present, some therapeutic options retain activity against Campylobacter jejuni circulating in Sana’a. The authors caution, however, that susceptibility patterns can shift rapidly under continued antibiotic pressure, and that fluoroquinolone resistance in Campylobacter has risen steeply in many parts of the world following the use of these agents in poultry production. Sustained local susceptibility testing, they argue, is essential to keep empirical treatment guidelines aligned with reality on the ground.

The molecular arm of the study added a layer of confidence that culture alone cannot provide. Sequencing of the 16S rRNA gene confirmed the identity of the isolates as Campylobacter jejuni with sequence identity of at least 99.6 percent against reference sequences, and phylogenetic analysis placed the Yemeni isolates in clusters closely related to established reference strains. This matters for two reasons. First, phenotypic identification of Campylobacter can be ambiguous, and molecular confirmation guards against misclassification that would distort prevalence and resistance statistics. Second, phylogenetic context allows researchers to begin tracing how strains circulate between animals, food, water and humans, a prerequisite for understanding transmission dynamics in a setting where such data have been almost entirely absent. The authors note that future work should employ advanced techniques to detect the antibiotic resistance genes themselves, and should use specialized genetic primers capable of differentiating between Campylobacter subspecies, alongside larger samples drawn from more diverse populations and methods such as multi-locus sequence typing and whole-genome sequencing.

The study was conducted with formal ethical oversight, receiving approval from the Research Ethics Review Committee at the Faculty of Science, Sana’a University under number BM-02-23, dated 11 April 2021, and complying with Yemeni Public Health Law No. 4 of 2009 and the Declaration of Helsinki. Because all participants were children under five, written informed consent was obtained from their parents or legal guardians before enrollment. The research team spanned several Yemeni institutions, including Sana’a University’s Faculty of Science, Hajjah University, Al-Razi University, Al Mahwit University and Ibb University, a collaboration that reflects both the country’s scientific capacity and the logistical challenges of conducting microbiological research amid prolonged instability. The work was published open access, with the article accepted on 21 September 2026 and published on 24 September 2026.

For global health observers, the Sana’a study is a reminder that antimicrobial resistance is not a problem confined to wealthy nations with dense surveillance networks; it evolves wherever antibiotics are used, and it is most dangerous precisely where the capacity to detect it is weakest. The authors close with a call that is as much public health as laboratory science: raising community awareness of hand hygiene after contact with animals, promoting safe food handling, encouraging water treatment, and curbing imprudent antibiotic use. Those measures, combined with expanded epidemiological studies and molecular surveillance, would give Yemeni clinicians something they currently lack, namely an evidence base for treating the youngest and most vulnerable patients with the right drug the first time, while slowing the further march of resistance in a pathogen that thrives at the intersection of animals, water, food and childhood.

Subject of Research: Molecular detection and antimicrobial resistance of Campylobacter jejuni in children with diarrhea in Sana'a City, Yemen

Article Title: Molecular detection and antibiotic susceptibility patterns of Campylobacter jejuni isolated from children under five years in Sana’a City, Yemen

Article References: Molecular detection and antibiotic susceptibility patterns of Campylobacter jejuni isolated from children under five years in Sana’a City, Yemen. (n.d.). https://doi.org/10.1186/s12879-026-14520-y

Image Credits: AI Generated

DOI: 10.1186/s12879-026-14520-y

Keywords: Campylobacter jejuni, diarrhea, children under five, antimicrobial resistance, 16S rRNA sequencing, Yemen, Sana'a City, macrolide resistance, foodborne pathogens, public health, phylogenetic analysis, water and food safety