Bacteria are unicellular microorganisms lacking a true nucleus; they reproduce by binary fission, colonize virtually all ecosystems, and can become significant human pathogens  [1] . Healthcare-associated infections (HAIs) remain a major burden worldwide: according to the WHO’s Global Report on Infection Prevention and Control (2024), millions of patients contract an HAI daily, which prolongs hospital stays, increases healthcare costs, and contributes to antimicrobial resistance. The burden is particularly severe in low- and middle-income countries such as Cameroon, where patients are up to twenty times more likely to acquire such infections compared to high-income countries  [2] .

Hemodialysis units are especially vulnerable to HAIs due to the frequent use of invasive procedures and direct blood access. A multicenter study across nine hemodialysis centers reported 1.98 infectious events per 100 patient-months, with Staphylococcus aureus bloodstream infections being the most common  [3] . Outbreaks linked to contaminated water or dialysate by Gram-negative bacilli are still being reported, underlining the critical importance of environmental hygiene and water quality  [4] . In Nigeria, all water outlets sampled from three hemodialysis centers were contaminated with Pseudomonas spp. or Moraxella spp.  [5] . Similarly, a South African cohort found that 23.9% of hemodialysis patients were colonized by multidrug-resistant organisms, particularly extended-spectrum β-lactamase-producing Klebsiella pneumoniae  [6] .

In Cameroon, and specifically in Douala, the situation is equally alarming. At the Douala General Hospital, infections at vascular access sites have been associated with a near doubling of mortality rates among patients with chronic kidney disease  [7] . Despite this significant risk, published data on the microbiological profile of hemodialysis units in the region remain scarce. A recent study in Rwanda also highlighted the high incidence of catheter-related bloodstream infections, mostly caused by Gram-negative bacilli  [8] . These findings reinforce the urgent need for strict adherence to international standards such as ISO 23500-1:2024, which defines microbiological requirements for the quality of water and dialysate in hemodialysis systems  [9] .

In this context, our study aims to bridge the global awareness of HAIs with the localized reality of Douala, by identifying the bacteria isolated from 411 samples collected within the hemodialysis unit of Douala General Hospital. The results will contribute to building a reference framework for ongoing microbiological surveillance and inform targeted infection prevention and control strategies tailored to our local setting.

Our results confirm that the hemodialysis unit represents a highly conducive environment for the transmission of opportunistic microorganisms. The surface positivity rate of 98.8% exceeded proportions reported in other dialysis or hospital isolation settings, where frequently touched surfaces (door handles, tables, bed headboards) are recognized as major vectors of healthcare-associated infections [10] [11] .

The predominance of Burkholderia cepacia (64.8 % of all isolates) is particularly alarming. Members of the Burkholderia cepacia complex are non-fermenting Gram-negative bacilli able to form chlorine- and quaternary-ammonium-resistant biofilms, and have repeatedly caused dialysis-related outbreaks through contamination of reverse-osmosis (RO) water, dialysate loops, dressings, or catheter exit sites [12] [13] . Their massive and repeated recovery from benches, machine consoles, and drain ports in our unit suggests 1) a persistent reservoir within the hydraulic circuit or carbon filters, and/or 2) cross-transmission via staff hands or inadequately disinfected shared equipment (blood-pressure cuffs, stethoscopes). To determine whether this reflects a single clonal strain or successive introductions, we plan to genotype representative isolates by recA sequencing or multilocus sequence typing (MLST)—and, if resources permit, whole-genome sequencing—while comparing them with isolates from water, dialysate, and any clinical infections. These data will guide targeted remediation measures such as shock disinfection or replacement of suspect pipework, reinforcement of hand-hygiene compliance, and stricter reprocessing of reusable accessories.

Among patients, the high frequency of fermentative Gram-negative bacilli—Escherichia coli, Klebsiella pneumoniae, and Proteus mirabilis—isolated from urine and blood cultures is consistent with observations from multicenter studies, where K. pneumoniae was the most common agent of hemodialysis-associated bloodstream infections [14] [15] . The concomitant isolation of Pseudomonas aeruginosa and Acinetobacter baumannii highlights the risk of infections with multidrug-resistant non-fermentative bacilli in this immunocompromised population.

The simultaneous detection of Staphylococcus aureus among patients and on surfaces suggests potential cross-transmission between skin colonization and environmental contamination, whereas coagulase-negative staphylococci (S. cohnii, S. xylosus) were almost exclusively environmental, reflecting their strong affinity for inert surface biofilms.

These findings call for strengthened prevention strategies: systematic disinfection of high-touch surfaces, regular audits of water and dialysate quality, active screening of patients colonized by Burkholderia cepacia or S. aureus, and a re-evaluation of cleaning protocols according to CDC guidelines for specialized units, including dialysis facilities [16] . Implementing continuous microbiological surveillance would allow for early detection of contamination and adjustment of control measures to reduce infectious burden and improve patient safety. In summary, the high level of contamination by Burkholderia cepacia and other non-fermenting Gram-negative bacilli requires, within the dialysis unit, the implementation of weekly environmental monitoring of water, dialysate, and critical surfaces, a revision of disinfection protocols using agents active against biofilms, and systematic antibiotic susceptibility testing to guide therapy and feed a national resistance registry. At the public-health level, these findings argue for the formal integration of dialysis centers into Cameroon’s national infection prevention program, the creation of a sentinel laboratory network capable of genotyping epidemic strains, and the development of Cameroonian guidelines on water quality, invasive-device management, and maintenance of hydraulic circuits, with the ultimate goal of sustainably improving the safety of patients with renal failure.

The hemodialysis unit showed extensive contamination: almost all surfaces and the majority of patient samples harbored bacteria, dominated by Burkholderia cepacia in the environment and by fermentative Gram-negative bacilli (notably E. coli and K. pneumoniae) in patients, while Staphylococcus aureus circulated between the two. These findings highlight a high risk of cross-transmission and bloodstream infections, emphasizing the urgent need to strengthen targeted disinfection practices, microbiological surveillance, and staff training to reduce the infectious burden and prevent the emergence of resistant strains.

We express our gratitude to all the individuals who voluntarily participated in the study and to the staff of the haemodialysis department at the General Hospital for their unwavering support throughout the research process.

The study received administrative authorisation and ethical approval from the General Hospital of Douala. Written informed consent to participate in this study was provided by the legal guardians/next of kin of the participants.

The original data supporting the conclusions of this article will be made available by the authors without undue reservation.

The authors state that the research was conducted in the absence of any external funding.

ENLPJ designed the experimental approach and the writing plan. ENLPJ and NNE recruited the participants and conducted the laboratory analyses. ENLPJ performed the statistical analysis and prepared all the figures. ENLPJ drafted the manuscript. ENLPJ, NNA, and FMEHD reviewed the manuscript. All the authors made substantial, direct, and intellectual contributions to the work and approved it for publication.