Cronobacter sakazakii and related enterobacteria from dry baby food: a profile of antibiotic resistance

Introduction. Cronobacter sakazakii (C. sakazakii) is an obligate pathogen in neonates, causing necrotizing enterocolitis, meningitis, and sepsis. The main transmission factor for these infections is powdered infant formula. Along with C. sakazakii, other Enterobacteriaceae spp., some of which are opportunistic pathogens, have been detected in dry foods for infants. Since all these bacteria are capable of exhibiting thermoresistance, surviving a technological stress such as the high-temperature drying process, there is a possibility that they also have other altered properties, in particular, antimicrobial resistance (AMR).

Objective. To evaluate the AMR profile, including resistance to clinically significant antimicrobial drugs, in C. sakazakii and other associated Enterobacteriaceae spp. isolated from dry foods for infants available on the Russian market.

Materials and Methods. A total of one hundred seventy seven samples of dry foods for infants and their production components were analyzed using bacterial culture with two-stage enrichment followed by biochemical identification of the isolates. The phenotypic AMR profile of the isolated Gram-negative and associated isolates was studied using the disk-diffusion method. For C. sakazakii, Klebsiella spp., and Acinetobacter baumannii isolates, minimum inhibitory concentrations (MICs) were additionally determined. DNA extracts from the isolated strains were analyzed by PCR for genes encoding extended-spectrum β-lactamases (tem, shv, ges, kpc, ctx), carbapenemases (ges, kpc, oxa), and metallo-β-lactamases (imp, vim) and the multidrug efflux pump gene adeF.

Results. Among dry foods for infants, 8.5% were contaminated with Cronobacter spp. and 38.4% - with other thermoresistant Enterobacteriaceae. A total of 65 strains were studied – 15 Cronobacter spp. and 49 associated Enterobacteriaceae spp. Phenotypically, all Cronobacter spp., as well as Klebsiella spp. and A. baumannii strains exhibited high levels of AMR to β-lactam antibiotics, including carbapenems as a priority class, and possessed multidrug resistance to 2–13 antibiotics.Analysis of the genetic potential of AMR to β-lactam antibiotics in Cronobacter and other thermoresistant bacteria from dry foods for infants revealed the presence of extended-spectrum β-lactamase (ESBL) genes in the opportunistic pathogens Klebsiella pneumoniae and Acinetobacter baumannii, which are classified as the ESKAPE group.

Limitations. The mechanisms underlying gene potential for resistance that would support the transmissible nature of AMR, have not been investigated.

Conclusion. When monitoring Cronobacter spp. in dry foods for infants, it is advisable to identify accompanying thermoresistant Gram-negative bacteria. If representatives of the ESKAPE group are detected among them, it is important to study their AMR to clinically significant antimicrobial drugs and their virulence factors. The data obtained will be useful for future recommendations on the quality control of ingredients and the effectiveness of production modes for dry foods for infants and cereals against thermoresistant non-spore-forming bacteria to reduce the risk for contamination with pathogens.

Compliance with ethical standards. The study did not require approval from the biomedical ethics committee.

Contributions:
Smotrina Yu.V. – data collection and processing, writing and editing;
Markova Yu.M., Stetsenko V.V., Bykova I.B., Polyanina A.S., – data collection and processing;
Sheveleva S.A., Efimochkina N.R. – conceptualization, study design, editing.
All authors are responsible for the integrity of all parts of the manuscript and approval of the manuscript final version.

Conflict of interest. The authors declare no conflict of interest.

Funding. The study was supported by grant No. 23-16-00163 from the Russian Science Foundation, https://rscf.ru/project/23-16-00163/

Received: December 7, 2025 / Accepted: June 18, 2026 / Published: July 31, 2026

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