Clinical and Environmental Reservoirs of Pseudomonas aeruginosa in Rural Tanzania: Implications for Diagnostics and Antimicrobial Stewardship
Article information
Abstract
Purpose
Antimicrobial resistance (AMR) is making urinary tract infections (UTIs) and surgical site infections (SSIs) increasingly difficult to treat, especially in low-resource settings where self-medication and limited laboratory services are common. This study explored knowledge and practices related to AMR and investigated Pseudomonas aeruginosa from clinical and environmental reservoirs in Kilombero, rural Tanzania.
Materials and Methods
A cross-sectional study was conducted over 9 months at St. Francis Regional Referral Hospital and selected community markets. Questionnaires were used to assess AMR awareness and antibiotic-use practices among community members and healthcare providers. Urine samples from pregnant women, SSI swabs, and fresh fish samples were collected. Fish were included as indicators of environmental reservoirs and possible foodborne exposure to P. aeruginosa. Presumptive isolates were confirmed using polymerase chain reaction targeting the OprI and OprL genes. Antimicrobial susceptibility testing followed EUCAST (European Committee on Antimicrobial Susceptibility Testing) 2021 guidelines.
Results
Only 34% of community participants correctly identified bacteria as causes of infection, while 19% had no knowledge of bacterial infections or AMR. Ciprofloxacin was the most commonly used antibiotic (49%), and self-diagnosis was frequently reported (35%), particularly among fish vendors. Poor hygiene practices, including hand-washing without soap, were also common. A total of 271 P. aeruginosa isolates were confirmed. Gentamicin showed the highest effectiveness across all sample sources, while resistance to meropenem and ciprofloxacin was substantial, especially among fish and SSI isolates.
Conclusions
Knowledge gaps, self-medication, and inconsistent hygiene coexist with the presence of P. aeruginosa in both clinical samples and fish representing environmental reservoirs Tanzania. Improved diagnostics, antimicrobial stewardship, hygiene practices, and community education are needed to strengthen AMR control using a One Health approach.
HIGHLIGHTS
Pseudomonas aeruginosa is a multisource bacterium which included: clinical samples represented by urine and surgical site infections and environmental samples presented by fresh fish, indicating widespread environmental and human reservoirs in rural Tanzania. High levels of resistance to commonly used antibiotics were observed, raising concerns for treatment efficacy and antimicrobial stewardship. Findings underscore interconnected human-food transmission pathways, supporting integrated surveillance and control strategies.
INTRODUCTION
Pseudomonas aeruginosa is a gram-negative bacterium widely distributed in the environment and recognized as an important opportunistic pathogen. It exhibits intrinsic resistance to many commonly prescribed antibiotics and disinfectants, complicating its management in both hospital and community settings [1,2]. The species has a relatively large genome (5.5–7 Mbp) consisting of a highly conserved core and a variable accessory genome. This genomic plasticity contributes to its remarkable metabolic capacity and supports horizontal gene transfer (HGT), allowing it to acquire and disseminate antimicrobial resistance (AMR) determinants across microbial communities [3-5].
Because of these traits, P. aeruginosa has become a major cause of healthcare-associated infections, including surgical site infections (SSIs), urinary tract infections (UTIs), and ventilator-associated pneumonia. In Tanzania, P. aeruginosa has been repeatedly reported among the most common multidrug-resistant pathogens isolated from hospital settings. Manyahi et al. [6] documented rising AMR trends in bloodstream infections at Muhimbili National Hospital, where P. aeruginosa showed resistance to cephalosporins and carbapenems. Earlier, Subedi et al. [7] and Pang et al. [8] had highlighted its role in nosocomial infections, while Moremi et al. [9] and Hokororo et al. [10] further confirmed its significance in urinary and wound infections. Collectively, these findings underscore its persistence in Tanzanian hospitals as a pathogen of concern.
Outside clinical settings, P. aeruginosa is widespread in water, soil, and food, with fish and other aquatic products serving as potential environmental reservoirs and routes of human exposure [11-13]. This is especially relevant in Tanzania’s Kilombero Valley, where close human- animal-environment interactions are common. Despite its importance, community-associated P. aeruginosa infections remain poorly understood in many low- and middle-income countries. The challenge is intensified by irrational antimicrobial use, including self-prescription, incomplete dosing, and easy over-the-counter access [14-17]. These behaviors promote the emergence and persistence of resistant strains. Addressing this requires integrated efforts combining hospital surveillance, community education, and environmental monitoring.
Accurate identification of P. aeruginosa is essential for effective surveillance, diagnosis, and infection control. Conventional biochemical methods, including oxidase testing, motility assessment, and pigment production, remain valuable for preliminary identification. However, molecular confirmation techniques offer higher sensitivity and specificity for accurate detection of the organism. In this study, isolates were characterized using the outer membrane lipoprotein I (OprI) and peptidoglycan-associated lipoprotein (OprL) gene makers for genus and species-specific level confirmation of P. aeruginosa [12,13]. Incorporating molecular methods enhances the accuracy of reporting and provides reliable evidence that can be used both locally and globally to inform AMR monitoring efforts.
This study investigated the prevalence and resistance profiles of P. aeruginosa isolated from SSIs, urine samples from pregnant women, and fish collected in the Kilombero Valley. By combining clinical, community, and environmental data, it aimed to shed light on transmission pathways beyond hospitals and document antimicrobial use practices, including inappropriate access and self-medication. The findings address key local knowledge gaps and support the World Health Organization’s call for evidence on multidrug-resistant priority pathogens. Ultimately, the results will inform Tanzania’s National Action Plan on AMR (2023–2028) by strengthening stewardship, infection prevention, and policy efforts to limit the spread of resistant P. aeruginosa.
MATERIALS AND METHODS
1. Study Area and Design
The study was conducted in Kilombero District in South-Eastern Tanzania. The Kilombero Valley is characterized by an extensive wetland system fed by the Kilombero River and its tributaries. Its low-lying location below sea level makes it one of the most humid regions in the country, creating ecological conditions that support close interactions between humans, animals, and the environment. A cross-sectional study was carried out over 9 months (January–September 2025). Samples were collected from 3 main sources: (1) patients with SSIs, (2) pregnant women attending antenatal clinics, and (3) fresh fish sold at local markets.
2. Sample Size Determination and Isolation Procedures
The sample size was determined using a 95% confidence level (Z=1.96), an assumed prevalence of 50% for P. aeruginosa resistance due to limited baseline data, and a margin of error of 5%, giving a minimum required sample size of 384 specimens. To increase statistical power and account for possible losses during microbiological and molecular analyses, the final target was rounded to 400 specimens. These comprised 150 SSI swab specimens, 200 urine specimens from pregnant women, and 50 fresh fish specimens collected from local markets. Fish samples were included to represent environmental reservoirs and potential foodborne exposure pathways for P. aeruginosa. The calculated sample size referred to the number of biological specimens collected and not the final number of bacterial isolates recovered. During microbiological culture, a single specimen could yield more than one presumptive P. aeruginosa isolate because multiple colonies with similar or distinct morphological characteristics could be present within the same sample. To improve detection of strain diversity and AMR patterns, up to three presumptive colonies from a single specimen were subcultured and analyzed separately.
3. Study Participant Recruitment and Sampling Strategy
Participants for the questionnaire survey were recruited from groups involved in healthcare delivery, antimicrobial use, and laboratory diagnostics within the study area. These included pregnant women attending antenatal clinics, medical students, drug prescribers, drug dispensers, laboratory technicians, and fish vendors. A purposive and convenience sampling strategy was used to recruit participants who were readily available and directly involved in activities related to antimicrobial use and infection control. Pregnant women attending antenatal clinics and patients with SSIs were recruited consecutively during the study period. On the other hand, fish vendors were recruited in the local market where they always sell the fish. The overall positive response rate of the participants in all categories was 95% of the target population.
4. Inclusion and Exclusion Criteria
Inclusion criteria included individuals aged 18 years or older who belonged to one of the targeted participant groups and were willing to provide informed consent. Individuals who declined participation or were unable to complete the questionnaire were excluded. A total of 424 participants completed the questionnaire. Nonparticipation was mainly due to lack of time or refusal, resulting in a high response rate among eligible individuals approached.
5. Clinical Sampling
1) Urine samples from pregnant women
Urine samples were collected from apparently healthy pregnant women attending Maternal and Child Health clinics at St. Francis Referral Hospital in Ifakara. Eligible participants were provided with sterile containers and instructed to collect midstream urine samples. Only women who provided written informed consent were included. Pregnant women were included in the study because pregnancy increases susceptibility to bacteriuria and UTIs. In addition, antenatal clinics provide an opportunity for systematic and standardized urine sample collection, while the presence of resistant uropathogens in this population has important implications for maternal and neonatal health outcomes and antimicrobial stewardship (AMS).
2) Surgical site infections
SSI samples were planned to be obtained from patients whose surgical wounds showed clinical signs of infection at least 72 hours after surgery. A SSI was defined as an infection occurring at or near the surgical incision within 30 days of surgery, or within 90 days for implant-related procedures. Swabs were collected under aseptic conditions by trained healthcare personnel. Patients with fresh wounds or infections attributed to non-surgical causes were excluded. The calculated sample size for the SSI component was 150 patients. However, the actual number of enrolled participants was 14 during the study period. This difference reflects the application of strict eligibility criteria, particularly the requirement for clinically confirmed postoperative infections occurring ≥ 72 hours after surgery, as well as participant consent considerations.
Given these constraints, the SSI component was implemented as an exploratory subgroup within the broader study. The reduced sample size was anticipated to limit statistical power; therefore, analyses involving SSI data were interpreted descriptively and with caution. Included SSI cases comprised clean-contaminated and contaminated wounds, mainly from abdominal and obstetric procedures, representing the most common surgical infection types observed at the study facility.
3) Fish samples
Environmental reservoirs were represented by fresh fish purchased from local vendors in Ifakara Township. Sterile swabs were taken from fish surfaces and immediately inoculated into double-strength nutrient broth to preserve bacterial viability. Only freshly caught fish were included in the study; frozen fish and fish sourced from lakes or oceans were excluded.
4) Sample collection and processing
Fresh fish samples were swabbed from 3 anatomical sites: the outer surface, gills, and intestines. For human samples, approximately 5 mL of midstream urine was self-collected in sterile containers, stored at 4°C, and processed within 6 hours. SSI swabs were collected aseptically by trained healthcare personnel. All samples (fish swabs, SSI swabs, and urine) were first enriched in peptone water broth and incubated for 24 hours, followed by subculture on cetrimide agar for selective isolation of P. aeruginosa. Presumptive isolates were identified based on standard phenotypic characteristics, including motility, positive oxidase and catalase reactions, gelatin hydrolysis, arginine dihydrolase activity, citrate utilization, and growth at 42°C, following established laboratory protocols.
To enhance representativeness while minimizing duplication, 2 to 3 morphologically distinct colonies were selected from each positive fish and SSI sample for further processing. For urine samples, where growth was typically more homogeneous, one representative colony per positive culture was selected. Each selected colony was treated as a presumptive isolate and subjected to further confirmation and antimicrobial susceptibility testing. Where multiple colonies from a single sample exhibited similar morphology, only one isolate was included in the final analysis to avoid overrepresentation. Conversely, morphologically distinct colonies were processed separately to capture potential within-sample diversity. For the SSI subgroup, given the limited number of enrolled patients, all eligible isolates meeting the selection criteria were included in the analysis. All confirmed isolates were stored at -20°C prior to downstream analyses.
6. Molecular Confirmation of P. aeruginosa
Presumptive P. aeruginosa isolates were refreshed in tryptone/tryptic soy broth for 6 hours at 37°C and subsequently subcultured on blood agar plates for 18 hours at 37°C. Genomic DNA was extracted from biochemically confirmed isolates and the reference strain P. aeruginosa ATCC 27853 using the Quick-DNA Miniprep Kit (Zymo Research Corp., USA), according to the manufacturer’s instructions. Species confirmation was performed by polymerase chain reaction (PCR) targeting the OprI gene, a genus marker for Pseudomonas, and the OprL gene, a species-specific marker for P. aeruginosa, following the protocol described by De Vos et al. [13].
Each 25-μL PCR reaction contained PCR master mix, forward and reverse primers, nuclease-free water, and 5 μL of template DNA. Amplification was performed in a thermocycler under the following conditions: initial denaturation at 95°C for 5 minutes, followed by 35 cycles of denaturation at 94°C for 30 seconds, annealing at 58° C for 30 seconds, and extension at 72°C for 45 seconds, with a final extension at 72°C for 5 minutes. PCR products were separated by electrophoresis on a 1.5% agarose gel at 100 V for approximately 40 minutes, stained, and visualized under ultraviolet illumination. Fragment sizes were determined using a 100-bp DNA ladder. Positive (P. aeruginosa ATCC 27853) and negative controls were included in all PCR runs. The primer sequences adopted in this confirmation are presented in Table 1.
Set of primers used to confirm Pseudomonas isolates
7. Antimicrobial Susceptibility Testing
Antimicrobial susceptibility testing was performed using the Kirby-Bauer disk diffusion method described by Bauer et al. [18] and interpreted according to European Committee on Antimicrobial Susceptibility Testing (EUCAST) guidelines [19]. The antibiotics tested were ciprofloxacin (5 μg), gentamicin (10 μg), meropenem (10 μg), and ceftriaxone (5 μg). These agents were selected to represent commonly used antimicrobial classes in the study setting. Ceftriaxone was included to reflect local empirical prescribing practices, where it is frequently used for the treatment of severe infections despite its limited activity against P. aeruginosa, particularly in situations where antimicrobial susceptibility testing is not routinely performed. For testing, isolates were subcultured on blood agar and incubated at 37°C for 24 hours. Three to 5 colonies from each plate were suspended in sterile distilled water and adjusted to 0.5 McFarland turbidity. The suspension was evenly inoculated onto Mueller- Hinton agar plates, after which antibiotic discs were applied. Plates were incubated at 37°C for 18–24 hours. The zones of inhibition were measured using a Vernier caliper, and results were interpreted using EUCAST breakpoint criteria to classify isolates as susceptible or resistant.
8. Questionnaire Survey
A structured questionnaire was administered to collect information on participants’ awareness of UTI and SSI symptoms, perceived causes of infection, diagnostic practices, and commonly used treatments. Additional health and behavioral questions were included to contextualize AMR patterns. Participants included 200 pregnant women, 100 medical students, 14 SSI patients, 20 fish vendors, 30 drug prescribers, 40 drug dispensers, and 20 laboratory technicians from years 2 to 5 were randomly selected. Medical students were included because, they are the future healthcare providers, their knowledge and practices are expected to influence prescribing behavior, infection control, and AMS efforts in Tanzania.
9. Data Analysis
Data were entered into Microsoft Excel (Microsoft Corp., USA), cleaned, and analyzed using Epi Info (Centers for Disease Control and Prevention, USA). Continuous variables were summarized using means and standard deviations, while categorical variables were presented as frequencies and percentages. Differences between groups were assessed using the chi-square test. When the assumptions for the chi-square test were not met, Fisher exact test or the Mann-Whitney U-test was applied as appropriate. Antimicrobial susceptibility patterns across sample sources were compared using 2×3 chi-square tests, and Wilson 95% confidence intervals (CIs) were calculated for proportions. To examine factors associated with self-medication practices, bivariate analysis was conducted using 2×2 contingency tables, and crude odds ratios (ORs) with 95% CIs were calculated. These comparisons assessed differences in self-medication among selected participant groups, including fish vendors, pregnant women, and medical versus nonmedical participants. A p-value <0.05 was considered statistically significant.
RESULTS
The study combined a questionnaire survey with laboratory analysis of specimens collected from clinical and environmental sources. A total of 400 biological specimens were targeted during study planning, including urine specimens from pregnant women, SSI swab specimens, and fresh fish samples. However, the number of eligible patients with confirmed SSIs presenting during the study period was lower than anticipated, resulting in fewer SSI specimens being collected than initially planned.
Overall, 271 P. aeruginosa isolates were confirmed by PCR and included in the final analysis. These comprised 144 isolates (53.1%) from urine specimens of pregnant women, 85 isolates (31.4%) from fish-derived environmental specimens, and 42 isolates (15.5%) from SSI specimens. The 42 SSI isolates were recovered from 14 patients with confirmed SSIs. During laboratory processing, multiple presumptive P. aeruginosa colonies were isolated from a single clinical specimen; therefore, up to three isolates from each SSI specimen were subcultured and analyzed separately to capture potential strain diversity and AMR variation within individual patient samples. Consequently, the 42 SSI isolates do not represent 42 independent patients but rather multiple isolates recovered from 14 SSI specimens. In addition, 424 participants completed a structured questionnaire assessing knowledge, attitudes, and practices related to antimicrobial use, self-medication, hygiene, and awareness of bacterial infections and AMR.
1. Community Knowledge, Care-Seeking, and Treatment for UTIs
Knowledge of UTI causative agents varied significantly across participant groups (Table 2). Most nonmedical respondents were unable to name specific pathogens, reporting “bacteria” (34%) or “don’t know” (19%). Among medical participants, Escherichia coli was the most frequently cited pathogen (26%), while Staphylococcus aureus (8%) and P. aeruginosa (4%) were rarely mentioned. Ciprofloxacin was the most commonly reported treatment (49%), followed by amoxicillin-clavulanic acid (21%), while gentamicin (13%) and ceftriaxone (6%) were less frequently cited. Diagnosis was largely informal, with 35% of respondents reporting self-diagnosis and only 15% seeking care at hospitals or 14% at registered laboratories. Microscopy (28%) was the most commonly cited diagnostic method, while culture-based testing was rarely reported. A summary of the results presented in this section is provided in Table 2.
Participant’s responses on pathogens, drugs, and diagnosis of UTIs
2. Participants’ Responses on IPC Practices, Stewardship Awareness, and Self-medication
Infection prevention and control (IPC) practices differed significantly across participant groups (chi-square test, p<0.001). Pregnant women (53.3%), SSI patients (80%), and fish vendors (60%) most frequently reported washing hands without soap, indicating suboptimal hygiene practices. In contrast, laboratory technicians (80%) and drug prescribers (50%) more commonly reported using soap or hand sanitizers, reflecting better adherence to recommended IPC practices. The results of this section are summarized in Table 3.
Participants’ responses on IPC, self-medication and AMR stewardship practices
Self-medication practices also varied across groups. The highest prevalence was observed among fish vendors (80%), followed by pregnant women (53.3%) and SSI patients (40%). Bivariate analysis showed that fish vendors had significantly higher odds of self-medication compared with other participants combined (OR, 3.41). In contrast, no meaningful difference was observed between medical and nonmedical participants (OR, 0.88). Awareness of AMS also differed significantly across groups (p<0.001). Nonmedical participants frequently reported having no formal source of stewardship information, whereas medical cadres commonly cited standard treatment guidelines and prescription forms as their primary sources of guidance. Table 4 summarizes the factors associated with self-medication among study participants.
Factors associated with self-medication
3. Biochemical and Molecular Confirmation of Bacterial Isolates
A total of 400 samples were collected from clinical and environmental sources, including fish, urine samples from pregnant women, and SSI specimens. After culture and biochemical screening, 295 isolates were identified as presumptive P. aeruginosa. These isolates were then confirmed using PCR targeting 2 markers: OprI, a genus-level marker for Pseudomonas, and OprL, a species-specific marker for P. aeruginosa. Of the 295 isolates, 282 (95.6%) were positive for OprI and 271 (91.9%) were positive for OprL. Only isolates positive for both genes were retained, yielding 271 confirmed P. aeruginosa isolates for analysis as shown in Table 5. In addition, Fig. 1 shows the agarose gel electrophoresis results of PCR amplification and molecular confirmation of P. aeruginosa isolates.
Conventional and molecular identification of bacterial isolates
Agarose gel electrophoresis showing polymerase chain reaction (PCR) amplification of the OprL (504 bp) and OprI (249 bp) genes used for molecular confirmation of Pseudomonas aeruginosa isolates. Lane L: 100–1,500 bp DNA ladder; Lane 1: negative control (PCR mixture without DNA template); Lanes 2–6: positive P. aeruginosa isolates showing amplification of the target genes; Lane 7: positive control using a reference strain of P. aeruginosa.
4. Antimicrobial Susceptibility Patterns
Marked differences in AMR were observed between environmental (fish) and clinical (urine and SSI) isolates (Table 6). Ciprofloxacin resistance was highest among SSI isolates (34 of 42, 81.0%), followed by fish isolates (57 of 85, 67.1%) and urine isolates (50.0%) (χ²=9.6, p=0.008). Meropenem resistance was highest in fish isolates 78 of 85 (91.8%), compared with SSI isolates (29 of 42, 69.1%) and urine isolates (44.4%) (χ²=38.2, p<0.001). Ceftriaxone resistance was near universal across all sources, with resistance rates of 88.2% in fish isolates and 100% in both urine and SSI isolates (p<0.001), indicating very limited clinical utility. Gentamicin showed the highest overall effectiveness, with susceptibility rates of 88.9% in urine isolates, 80.0% in fish isolates, and 73.8% in SSI isolates (p=0.03). Correspondingly, resistance was highest in SSI isolates (11 of 42, 26.2%), followed by fish isolates (17 of 85, 20.0%) and urine isolates (16 of 144, 11.1%). Overall, antimicrobial susceptibility patterns varied significantly by source of isolation, with environmental isolates demonstrating particularly high resistance to meropenem, and SSI isolates showing elevated resistance to ciprofloxacin and gentamicin. The detailed distribution of susceptibility and resistance is presented in Table 6. In addition, Fig. 2, shows the antimicrobial susceptibility patterns of P. aeruginosa isolates among samples
Antimicrobial sensitivity test of 271 Pseudomonas aeruginosa isolates
Antimicrobial susceptibility patterns of Pseudomonas aeruginosa isolates from fish, surgical site infections (SSI), and urine samples.
DISCUSSION
This study integrates community knowledge, clinical practice, and laboratory evidence to characterize drivers of UTI management and AMR in a rural Tanzanian setting. Three key themes emerged: (1) substantial knowledge and diagnostic gaps among community members, (2) uneven infection prevention and AMS practices with heavy reliance on self-medication, and (3) laboratory confirmation of P. aeruginosa across clinical and environmental samples with variable susceptibility to commonly used antibiotics. Together, these findings highlight the interconnected biological, behavioral, and health system factors sustaining AMR in low-resource contexts.
1. Knowledge and Diagnosis of UTIs in Global Context
Knowledge regarding the causes of urinary tract infections (UTIs) was generally limited among nonmedical participants, with many respondents unable to identify specific bacterial pathogens. Similar findings have been reported in Tanzania and other low- and middle-income countries (LMICs), where limited awareness of infectious diseases and restricted access to diagnostic services contribute to inappropriate healthcare-seeking behavior and empiric antibiotic use [17,20-24]. Although medical participants were more likely to identify Escherichia coli as a common uropathogen, awareness of other clinically important organisms, including P. aeruginosa, remained low.
The findings also revealed heavy reliance on self-diagnosis and limited utilization of laboratory-based diagnostics. This pattern is concerning because accurate diagnosis is essential for appropriate antimicrobial selection and effective stewardship. The World Health Organization (WHO) has emphasized that strengthening diagnostic capacity is a key component of AMR control, particularly in resource-constrained settings where empirical prescribing remains common [25]. Limited access to culture and susceptibility testing may contribute to inappropriate antibiotic use and accelerate the emergence of resistant pathogens.
2. Treatment Patterns and Self-medication Across Regions
Ciprofloxacin was the most frequently reported antibiotic used by participants, and self-medication was common, particularly among fish vendors. Similar patterns of inappropriate antibiotic use have been documented in Tanzania and elsewhere in sub-Saharan Africa, where antibiotics are often obtained without prescriptions and used without microbiological confirmation [21,25-28]. Self-medication may be driven by financial constraints, perceived convenience, previous treatment experiences, and inadequate access to healthcare facilities. The high prevalence of self-medication observed in this study raises concerns regarding inappropriate antibiotic exposure and selection pressure for resistant organisms. Previous studies have demonstrated that irrational antimicrobial use contributes significantly to the emergence and dissemination of AMR in both healthcare and community settings [17,23,29]. These findings underscore the need for community-targeted stewardship interventions, improved public awareness, and stronger regulation of antibiotic dispensing practices.
3. IPC, Stewardship Practices, and Global Stewardship Standards
Poor hand hygiene practices were common among nonclinical participants, particularly pregnant women and fish vendors. Inadequate hand hygiene has consistently been associated with increased transmission of infectious agents and antimicrobial-resistant organisms. Previous studies in Tanzania have similarly reported challenges in adherence to IPC measures among both healthcare workers and community populations [14,23]. The WHO identifies hand hygiene as one of the most effective interventions for preventing infection transmission and reducing healthcare-associated infections [30-33]. The findings suggest that community-based IPC interventions should complement facility-based stewardship programs. Educational campaigns focusing on hand hygiene, food handling practices, and infection prevention may contribute to reducing both infection rates and antibiotic consumption within the community.
4. P. aeruginosa in Fish: Contamination or Ecological Reservoir?
A major finding of this study was the detection of P. aeruginosa in urine specimens, surgical site infections, and fish samples. The occurrence of P. aeruginosa across multiple ecological niches supports its recognized role as both an opportunistic pathogen and an environmental organism capable of persisting in diverse habitats [1,12,34]. The recovery of isolates from fish suggests that environmental reservoirs may contribute to the maintenance and dissemination of resistant organisms within the community. Previous studies have demonstrated that aquatic environments can serve as important reservoirs of P. aeruginosa and other resistant bacteria [12]. Exposure to wastewater, agricultural runoff, and other sources of environmental contamination may facilitate bacterial persistence and the exchange of resistance determinants through horizontal gene transfer [4,5,35]. Although this study did not investigate transmission pathways directly, the findings reinforce the importance of incorporating environmental surveillance into national AMR monitoring frameworks.
5. Susceptibility Patterns and Global Clinical Implications
Antimicrobial susceptibility testing revealed substantial resistance to ciprofloxacin, meropenem, and ceftriaxone, whereas gentamicin retained comparatively higher activity across isolates from all sample sources. These findings are consistent with reports from Tanzania and other African settings describing increasing resistance among P. aeruginosa and other gram-negative pathogens [6,20,36]. The widespread resistance observed to ceftriaxone was expected because P. aeruginosa possesses intrinsic resistance mechanisms that limit the clinical effectiveness of many cephalosporins.
Particularly concerning was the high level of resistance to meropenem among environmental isolates. Carbapenems are often regarded as last-line agents for the treatment of severe infections caused by multidrug-resistant gram-negative bacteria. Increasing resistance to these agents threatens the availability of effective therapeutic options and has been identified as a global public health concern [28,29,37]. The findings highlight the need for routine antimicrobial susceptibility testing, development of local antibiograms, and implementation of stewardship interventions aimed at preserving the effectiveness of critically important antimicrobials.
6. Programmatic and Global Policy Relevance
The coexistence of resistant P. aeruginosa in human and environmental reservoirs illustrates the importance of a One Health approach to AMR control. The WHO, Food and Agriculture Organization, World Organisation for Animal Health, and United Nations Environment Programme have emphasized that AMR cannot be effectively addressed through healthcare interventions alone but requires coordinated action across human, animal, and environmental sectors [38,39]. The findings of this study support the objectives of Tanzania’s National Action Plan on Antimicrobial Resistance (2023–2028), which prioritizes surveillance, stewardship, infection prevention, and multisectoral collaboration [37]. Strengthening diagnostic services, promoting rational antimicrobial use, improving IPC practices, and integrating environmental surveillance into AMR monitoring systems may contribute substantially to reducing the burden of resistant infections.
7. Strengths and Limitations
A key strength of this study is the integration of community behavioral data with molecular identification and antimicrobial susceptibility testing across clinical and environmental samples, using a One Health approach. Limitations include the cross-sectional design, reliance on self-reported behaviors, and absence of genotypic relatedness analyses (e.g., multilocus sequence typing or whole-genome sequencing), which prevents confirmation of direct transmission between environmental reservoirs (fish) and human isolates. The heterogeneous study population may reduce comparability across groups, although it reflects real-world complexity.
CONCLUSION
Knowledge gaps, self-medication, and uneven IPC/AMS practices coexist with confirmed P. aeruginosa across human and environmental reservoirs and worrisome susceptibility patterns in clinical isolates. Pragmatic, nurse-anchored education, basic diagnostic stewardship, and integrated One Health surveillance are feasible, high-yield steps to reduce inappropriate antibiotic use and slow AMR in Tanzanian communities and hospitals.
Notes
Funding/Support
This study was funded by the Danish Fellowship Centre (DFC) under the Knowledge in Action Grant (Grant ID - 21-EC02-KU).
Research Ethics
Ethical approval was obtained from a recognized institutional ethics review committee (Ref. No. SFUCHAS/IRB/Vol.I/2023/0121). Written informed consent was obtained from pregnant women and fish vendors aged 18 years and above. The participation was voluntary, and respondents were informed of their right to withdraw at any stage without penalty. Confidentiality and anonymity were strictly maintained by using unique identification codes instead of personal identifiers, while the data were securely stored and accessible only to the research team.
Conflict of Interest
The authors have nothing to disclose.
Acknowledgments
The authors would like to acknowledge the medical officers for their administrative support, St. Francis Referral hospital staff, the fish vendors and the patients in the surgical wards for their consent to participate in the study.
Author Contribution
Conceptualization: PBM; Data curation: TAK; Formal analysis: PBM; Funding acquisition: PBM; Methodology: PBM; Project administration: SBA; Writing - original draft: PBM, TAK; Writing - review & editing: SBA.