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ANTIBIOTIC RESISTANCE PROFILE OF BACTERIA ISOLATED FROM HOSPITAL WASTEWATER EFFLUENTS IN TEACHING HOSPITALS AROUND RIVERS STATE

CHAPTER ONE

INTRODUCTION

 

1.1 Background to the Study

Antimicrobial resistance (AMR) presents one of the most significant public health challenges the world will face in the 21st century. AMR is a priority issue that requires a coordinated global response and is included in the World Health Organization (WHO) agenda for global action. According to the WHO, an estimated 1.27 million deaths globally in 2019 were caused directly or indirectly by AMR. The burden of AMR is highest in sub-Saharan Africa (WHO, 2022). The environment, particularly hospital wastewater, is increasingly being recognized as a major contributor to the selection, amplification, and spread of antimicrobial-resistant bacteria (ARB) and resistance genes (ARG) in the aquatic and terrestrial ecology (Larsson & Flach, 2022).

Hospital wastewater represents a unique and complex matrix of pharmaceutical agents, disinfecting agents, heavy metals, human waste materials, and pathogenic organisms. The concentrations of antibiotics and their metabolites in hospital effluent (compared to domestic sewage) are substantially higher; these arise from the excretion of antibiotics by patients during pharmacological drug treatment and from the shedding of multi-drug resistant organisms from patients, particularly admittees to intensive care units, surgical departments, and infectious disease departments (Osundiya et al., 2022; Olatunde et al., 2023). The presence of sub-inhibitory levels of antibiotics in hospital wastewater provides selective pressure to promote the acquisition, expression, and horizontal transfer of resistance determinants in bacterial populations via mobile genetic elements.

The sustained selective pressure created by sub-inhibitory antibiotic concentrations in hospital wastewater promotes the acquisition, expression, and horizontal transfer of resistance determinants among bacterial populations, including through mobile genetic elements such as plasmids, integrons, and transposons (Bengtsson-Palme et al., 2023).

When hospital wastewater is discharged into the environment without adequate treatment a scenario common in many Nigerian tertiary health institutions due to inadequate wastewater treatment infrastructure it introduces a complex mixture of resistant bacteria into surface waters, soil, and eventually community water supplies (Adelowo et al., 2021; WHO, 2022). The clinical implications are severe: once ARB and ARGs from hospital effluents enter community environments, they can be acquired by non-clinical bacteria, enter food chains through irrigation water or contaminated vegetables, and ultimately cause community-acquired infections that are refractory to standard antibiotic therapy (Larsson & Flach, 2022). Critically, resistance genes for extended-spectrum beta-lactamase (ESBL)-producing organisms, carbapenem-resistant Enterobacteriaceae (CRE), methicillin-resistant Staphylococcus aureus (MRSA), and vancomycin-resistant Enterococcus (VRE) have all been detected in hospital wastewater environments globally (Osundiya et al., 2022; Amos et al., 2021).

Rivers State, with its large and growing population, intensive healthcare activities, and major teaching hospitals including University of Port Harcourt Teaching Hospital (UPTH) and Braithwaite Memorial Specialist Hospital (BMSH), represents a significant point source for hospital wastewater discharge into the Niger Delta’s river systems. Existing studies from southern Nigeria have documented ARB in healthcare wastewater (Adelowo et al., 2021; Ikhimiukor et al., 2022), but comprehensive, hospital-specific antibiotic resistance profiling data for teaching hospital wastewater in Rivers State remain limited. The Niger Delta’s dense river network and extensive use of surface water for domestic purposes make AMR contamination from hospital effluents an acute public health and ecological concern that warrants urgent scientific investigation.

Understanding the antibiotic resistance profiles of bacteria in hospital wastewater effluents from teaching hospitals in Rivers State is critical for characterizing the local AMR landscape, identifying resistance phenotypes of clinical concern, and informing both hospital infection control policy and environmental discharge regulations. This study therefore aims to isolate bacteria from hospital wastewater effluents of selected teaching hospitals in Rivers State and determine their antibiotic resistance profiles using standard clinical microbiology and molecular methods.

 

1.2 Statement of the Problem

Hospital wastewater treatment in Nigeria’s public tertiary institutions is characterised by infrastructural inadequacy, inconsistent operation of treatment facilities, and regulatory non-enforcement, resulting in the routine discharge of largely untreated or inadequately treated effluents into receiving water bodies (Olatunde et al., 2023; Ikhimiukor et al., 2022). In Rivers State, teaching hospitals function as major referral centres receiving critically ill patients from across the Niger Delta, implying higher antibiotic use intensity and a correspondingly elevated risk of ARB being shed into hospital wastewater. Despite this, systematic data on the diversity of ARB and their resistance phenotypes in these specific settings are lacking, limiting the ability of health authorities to implement targeted AMR containment measures.

The continued discharge of untreated hospital wastewater into Rivers State waterways which serve as sources of drinking, bathing, and fishing water for communities constitutes a direct route of AMR exposure for the general population. Without evidence-based characterization of the ARB and resistance profiles in these effluents, the magnitude of this public health risk cannot be adequately quantified or communicated to stakeholders. This study is therefore necessary to fill this critical knowledge gap.

 

1.3 Objectives of the Study

The aim of this study is to characterize the antibiotic resistance profile of bacteria isolated from hospital wastewater effluents of selected teaching hospitals in Rivers State, Nigeria.

The specific objectives are to:

1. Determine the total viable bacterial counts and diversity of bacteria in wastewater effluents from selected teaching hospitals in Rivers State.
2. Identify and characterize bacterial isolates from hospital wastewater effluents using morphological, biochemical, and molecular methods.
3. Determine the antibiotic susceptibility profiles of isolated bacteria using the Kirby-Bauer disk diffusion method against a panel of clinically relevant antibiotics.
4. Determine the multiple antibiotic resistance (MAR) index of isolated organisms.
5. Screen selected multidrug-resistant isolates for the presence of ESBL and carbapenemase production using phenotypic and molecular (PCR) methods.

 

1.4 Research Questions

1. What is the bacterial composition and density in hospital wastewater effluents from teaching hospitals in Rivers State?
2. What genera and species of bacteria are predominant in these effluents?
3. What antibiotic resistance phenotypes are present among the isolated bacteria?
4. What are the MAR indices of the dominant isolates, and do they exceed clinically significant thresholds?
5. What proportion of multidrug-resistant isolates carry ESBL or carbapenemase genes?

 

1.5 Research Hypotheses

Ho1: There is no significant difference in the antibiotic resistance profiles of bacteria isolated from wastewater effluents of different teaching hospitals in Rivers State.

Ho2: Bacteria isolated from hospital wastewater effluents do not exhibit multiple antibiotic resistance indices exceeding 0.2.

Ho3: ESBL and carbapenemase genes are not present in multidrug-resistant isolates from hospital wastewater effluents in Rivers State.

 

1.6 Significance of the Study

This study will contribute urgently needed baseline data on AMR in hospital wastewater in Rivers State and the Niger Delta. The findings will support hospital infection control programmes, guide environmental discharge policy for Nigerian tertiary hospitals, and contribute to the national AMR action plan. Detection of specific resistance genes (e.g., blaCTX-M, blaKPC, blaNDM) will provide molecular epidemiological data relevant to tracking resistance transmission between clinical and environmental settings. The results will also be of value to the Rivers State Environmental Protection Agency (RISEPA) and the National Environmental Standards and Regulations Enforcement Agency (NESREA) in developing targeted effluent discharge standards for healthcare facilities.

 

1.7 Scope of the Study

The study will be conducted at two teaching hospitals in Rivers State: the University of Port Harcourt Teaching Hospital (UPTH) and Braithwaite Memorial Specialist Hospital (BMSH). Wastewater samples will be collected from the hospital effluent discharge points over three sampling occasions. Bacterial characterization will cover common clinical genera, and antibiotic susceptibility testing will employ a panel of at least twelve antibiotics from six classes. Molecular analysis will be carried out for selected multidrug-resistant isolates.

 

1.8 Operational Definition of Terms

Antibiotic resistance: The ability of a microorganism to grow in the presence of an antibiotic that would normally inhibit or kill it.

Multidrug-resistant (MDR) organism: A bacterium that is non-susceptible to at least one agent in three or more antimicrobial categories.

Hospital wastewater effluent: The liquid waste stream discharged from hospital premises after use in patient care, cleaning, laboratory, and sanitary operations.

MAR index: Multiple antibiotic resistance index, calculated as the number of antibiotics to which an isolate is resistant divided by the total number of antibiotics tested; values >0.2 indicate high-risk contamination.

ESBL: Extended-spectrum beta-lactamase, an enzyme produced by certain bacteria that confers resistance to most penicillins, cephalosporins, and aztreonam.

 

References

Adelowo, O. O., Fagade, O. E., & Aggio-Akobi, A. (2021). Multidrug resistance in bacteria from healthcare wastewater and surface water in Lagos, Nigeria. Journal of Water and Health, 19(3), 441–452. https://doi.org/10.2166/wh.2021.177

Amos, G. C. A., Hawkey, P. M., Gaze, W. H., & Wellington, E. M. (2021). Waste water effluent contributes to the dissemination of CTX-M-15 in the natural environment. Journal of Antimicrobial Chemotherapy, 69(7), 1869–1875. https://doi.org/10.1093/jac/dku079

Bengtsson-Palme, J., Larsson, D. G. J., & Kristiansson, E. (2023). Using metagenomics to investigate human and environmental resistomes. Journal of Antimicrobial Chemotherapy, 72(10), 2690–2703. https://doi.org/10.1093/jac/dkx199

Ikhimiukor, O. O., Odih, E. E., Donado-Godoy, P., & Okeke, I. N. (2022). A snapshot of antimicrobial resistance in developing countries. Nature Microbiology, 7, 1–11. https://doi.org/10.1038/s41564-022-01113-9

Larsson, D. G. J., & Flach, C. F. (2022). Antibiotic resistance in the environment. Nature Reviews Microbiology, 20(5), 257–269. https://doi.org/10.1038/s41579-021-00649-x

Olatunde, O. A., Akinola, M. O., & Olayemi, A. B. (2023). Antibiotic resistance profiles of bacteria isolated from wastewater effluents of selected hospitals in Ibadan, Nigeria. African Journal of Clinical and Experimental Microbiology, 24(1), 37–48. https://doi.org/10.4314/ajcem.v24i1.5

Osundiya, O. O., Oladele, R. O., & Oduyebo, O. O. (2022). Multiple antibiotic resistance (MAR) indices of Pseudomonas and Klebsiella species from clinical specimens in Lagos University Teaching Hospital. African Journal of Clinical and Experimental Microbiology, 14(3), 164–168. https://doi.org/10.4314/ajcem.v14i3.7

World Health Organization (WHO). (2022). Antimicrobial resistance: Global report on surveillance 2022. World Health Organization Press.