Hospital wastewater (HWW) treatment in low- and middle-income countries: A systematic review of microbial treatment efficacy

BACKGROUND

Proper treatment of hospital wastewater (HWW) is crucial to minimize the long-term effects on human health and aquatic ecosystems. However, the majority of HWW generated in low and middle-income countries (LMICs), is discharged without adequate treatment. This systematic review aims to fill the knowledge gap in LMICs by examining the efficacy of HWW treatment and the types of technologies used.

METHODS

Studies included in the review offered valuable insights into the current state of HWW management in LMICs. Between 2000 and 2022, only 36 research studies focused on hospital-based wastewater treatment within LMICs. Data were extracted on wastewater treatment technologies in hospitals or healthcare settings in LMICs. Data on sampling techniques, effectiveness, microorganisms and risk of bias of included studies were recorded.

RESULTS

A total of 36 articles met the eligibility criteria: mentioned about 1) hospitals 2) wastewater treatment 3) LMICs and 4) treatment efficacy. Twenty-two studies were conducted in Asia (22/36), 17 were conducted in countries with high Human Development Index. Constructed wetland, and activated sludge process were the most common technologies used in LMICs. A few studies utilized membrane bioreactors and ozone/UV treatment. Fourteen studies reported the concentration reduction to assess the microbial efficacy of the treatment process, 29/36 studies did not meet the national standards for effluent discharge. Reporting on sampling methods, wastewater treatment processes and efficacy of HWW treatment were at high risk of bias. Extreme heterogeneity in study methods and outcomes reporting precluded meta-analysis.

CONCLUSIONS

The existing evidence indicates inadequate microbial treatment in low- and middle-income country hospitals, with this systematic review emphasizing the need for improvement in healthcare waste management. It underscores the importance of long-term studies using innovative treatment methods to better understand waste removal in LMIC hospitals and calls for further research to develop context-specific healthcare waste treatment approaches in these regions.

Detection of metallo-beta-lactamase-producing genes blaSPM and blaNDM in Pseudomonas aeruginosa isolated from wastewater in Southern Brazil

Pseudomonas aeruginosa is commonly associated with the ability to acquire antimicrobial resistance. The surveillance of resistance genes in various environmental matrices has gained prominence in recent years, being seen as a potential threat to public health. The objective of this study was to investigate genes encoding metallo-beta-lactamases (MBLs), which confer resistance to carbapenems, in wastewater. Fifteen isolates of P. aeruginosa were collected for five months from samples obtained from a municipal wastewater treatment plant in Rio Grande do Sul. These isolates were subjected to disk diffusion testing using 10 different antimicrobials. Phenotypic enzymatic tests for MBLs were conducted, and positive isolates underwent DNA extraction and gene detection using the polymerase chain reaction. The resistance rate to ceftazidime was 100%, cefepime 73.3%, piperacillin-tazobactam 66.67%, imipenem 53.30%, levofloxacin 46.67%, tobramycin 40%, and ciprofloxacin and amikacin 13.33%. Both meropenem and aztreonam resistances were rare accounting for 6.60% of the tested isolates. Among these isolates, 20% were classified as multidrug-resistant and were found to carry the blaNDM and blaSPM genes. The results suggest that evaluating resistance genes in bacteria from urban raw sewage can provide data that assist in surveillance, as this environment can stimulate increased bacterial resistance.

Surveillance of multidrug-resistant tuberculosis in sub-Saharan Africa through wastewater-based epidemiology

The spread of multidrug-resistant tuberculosis (MDR-TB) is a serious public health issue, particularly in developing nations. The current methods of monitoring drug-resistant TB (DR-TB) using clinical diagnoses and hospital records are insufficient due to limited healthcare access and underreporting. This study proposes using Wastewater-Based Epidemiology (WBE) to monitor DR-TB in six African countries (Ghana, Nigeria, Kenya, Uganda, Cameroon, and South Africa) and examines the impact of treated wastewater on the spread of TB drug-resistant genes in the environment. Using droplet-digital polymerase chain reaction (ddPCR), the study evaluated untreated and treated wastewater samples in selected African countries for TB surveillance. There was a statistically significant difference in concentrations of genes conferring resistance to TB drugs in wastewater samples from the selected countries (p-value<0.05); South African samples exhibited the highest concentrations of 4.3(±2,77), 4.8(±2.96), 4.4(±3,10) and 4.7(±3,39) log copies/ml for genes conferring resistance to first-line TB drugs (katG, rpoB, embB and pncA respectively) in untreated wastewater. This may be attributed to the higher prevalence of TB/MDR-TB in SA compared to other African countries. Interestingly, genes conferring resistance to second-line TB drugs such as delamanid (ddn gene) and bedaquiline (atpE gene) were detected in relatively high concentrations (4.8(±3,67 and 3.2(±2,31 log copies/ml for ddn and atpE respectively) in countries, such as Cameroon, where these drugs are not part of the MDR-TB treatment regimens, perhaps due to migration or the unapproved use of these drugs in the country. The gene encoding resistance to streptomycin (rrs gene) was abundant in all countries, perhaps due to the common use of this antibiotic for infections other than TB. These results highlight the need for additional surveillance and monitoring, such as WBE, to gather data at a community level. Combining WBE with the One Health strategy and current TB surveillance systems can help prevent the spread of DR-TB in populations.

The African Wastewater Resistome: Identifying Knowledge Gaps to Inform Future Research Directions

Antimicrobial resistance (AMR) is a growing global public health threat. Furthermore, wastewater is increasingly recognized as a significant environmental reservoir for AMR. Wastewater is a complex mixture of organic and inorganic compounds, including antibiotics and other antimicrobial agents, discharged from hospitals, pharmaceutical industries, and households. Therefore, wastewater treatment plants (WWTPs) are critical components of urban infrastructure that play a vital role in protecting public health and the environment. However, they can also be a source of AMR. WWTPs serve as a point of convergence for antibiotics and resistant bacteria from various sources, creating an environment that favours the selection and spread of AMR. The effluent from WWTPs can also contaminate surface freshwater and groundwater resources, which can subsequently spread resistant bacteria to the wider environment. In Africa, the prevalence of AMR in wastewater is of particular concern due to the inadequate sanitation and wastewater treatment facilities, coupled with the overuse and misuse of antibiotics in healthcare and agriculture. Therefore, the present review evaluated studies that reported on wastewater in Africa between 2012 and 2022 to identify knowledge gaps and propose future perspectives, informing the use of wastewater-based epidemiology as a proxy for determining the resistome circulating within the continent. The study found that although wastewater resistome studies have increased over time in Africa, this is not the case in every country, with most studies conducted in South Africa. Furthermore, the study identified, among others, methodology and reporting gaps, driven by a lack of skills. Finally, the review suggests solutions including standardisation of protocols in wastewater resistome works and an urgent need to build genomic skills within the continent to handle the big data generated from these studies.

Antibiotic resistomes and their chemical residues in aquatic environments in Africa

The aquatic environment is a hotspot for the transfer of antibiotic resistance to humans and animals. Several reviews have put together research efforts on the presence and distribution of antibiotic resistant bacteria (ARB), antibiotic resistance genes (ARGs), and antibiotic chemical residue (ACRs) in food, hospital wastewater, and even in other aquatic environments. However, these reports are largely focused on data from developed countries, while data from developing countries and especially those in Africa, are only marginally discussed. This review is the first effort that distills information on the presence and distribution of ARGs and ACRs in the African aquatic environments (2012-2021). This review provides critical information on efforts put into the study of ARB, ARGs, and ACRs in aquatic environments in Africa through the lens of the different sub-regions in the continent. The picture provided is compared with those from some other continents in the world. It turns out that the large economies in Africa (South Africa, Nigeria, Tunisia, Kenya) all have a few reports of ARB and ARGs in their aquatic environment while smaller economies in the continent could barely provide reports of these in their aquatic environment (in most cases no report was found) even though they have some reports on resistomes from clinical studies. Interestingly, the frequency of these reports of ARB and ARGs in aquatic environments in Africa suggests that the continent is ahead of the South American continent but behind Europe and Asia in relation to providing information on these contaminants. Common ARGs found in African aquatic environment encode resistance to sulfonamide, tetracycline, β-lactam, and macrolide classes of antibiotics. The efforts and studies from African scientists in eliminating ARB and ARGs from the aquatic environment in Africa are also highlighted. Overall, this document is a ready source of credible information for scientists, policy makers, governments, and regional bodies on ARB, ARGs, and ACRs in aquatic environments in Africa. Hopefully, the information provided in this review will inspire some necessary responses from all stakeholders in the water quality sector in Africa to put in more effort into providing more scientific evidence of the presence of ARB, ARGs, and ACRs in their aquatic environment and seek more efficient ways to handle them to curtail the spread of antibiotic resistance among the population in the continent. This will in turn, put the continent on the right path to meeting the United Nations Sustainable Development Goals #3 and #6, which at the moment, appears to be largely missed by most countries in the continent.

Multidrug-Resistant Bacteria in Hospital Wastewater of the Korle Bu Teaching Hospital in Accra, Ghana

BACKGROUND

Antimicrobial resistance (AMR) is one of the top 10 public health threats. One approach to tackling the AMR menace could involve expanding the range of AMR surveillance domains to include hospital wastewater (HWW), a domain that has largely been overlooked by researchers.

AIM

To evaluate the occurrence of multidrug-resistant bacteria in hospital wastewater of the Korle Bu Teaching Hospital (KBTH).

METHODOLOGY

This was a longitudinal study involving 288 HWW samples consecutively collected across 12 weeks from the pool of wastewater emanating from 2 critical care units of KBTH-The Child Health Unit and the Maternity Unit-on Mondays and Thursdays, each week. The samples were cultured for bacteria, which were identified using the Matrix-Assisted Laser Desorption/Ionization-Time of Flight (MALDI-TOF) technique and subjected to antimicrobial susceptibility testing via the Kirby-Bauer method.

RESULTS

In total, 294 bacteria of 23 different types, all being Gram-negative, were isolated from the 288 samples. The predominant ones were Escherichia coli (30.6%, n = 90), Klebsiella pneumoniae (11.2%, n = 33), Citrobacter freundii (10.9%, n = 32), Alcaligenes faecalis (5.8%, n = 17), and Pseudomonas mendocina (5.4%, n = 16). The prevalence of multidrug resistance among the isolates was 55.4% (n = 163). Moreover, the prevalence of extended-spectrum beta-lactamase (ESBL) producers was 15.6% (n = 46). E. coli accounted for the most ESBL-producing organisms (28.9%, n = 26).

CONCLUSION

The wastewater generated by the Maternity and Child Health Units of KBTH harbored a wide range of multidrug resistant bacteria, with a good proportion of these being ESBL producers, and the predominant one being E. coli. The study thus identifies the wastewater of KBTH as an important source of multidrug resistant organisms, and underscores the significance of appropriate treatment of wastewater of the hospital and other clinical, and related settings prior to its discharge.

Occurrence and anti-microbial susceptibility pattern of extended spectrum beta-lactamase producing Enterobacteriaceae in governmental hospitals wastewater in Addis Ababa, Ethiopia

Background

Worldwide, come out and dissemination of extended-spectrum beta-lactamases (ESBLs) producing Enterobacteriaceae has been warning the efficacy of antibiotics to treat an infection. Hospital wastewaters were a reservoir of such kind of resistant bacteria. Currently, the predominant antibiotics used for the treatment of hospitalized patients infected by Gram-negative bacteria are the β-lactam antibiotics. Therefore, it is an important source to investigate the magnitude of ESBLs producing bacteria and their antimicrobial susceptibility pattern. This study aimed to determine the occurrence of ESBLs producing Enterobacteriaceae (ESBLs-pE) and their antibiotic susceptibility pattern in wastewater released from five governmental hospitals in Addis Ababa, Ethiopia.

Methods

A cross-sectional study was conducted from April 1 to May 31, 2020. A total of 100 wastewaters were collected from five governmental hospitals in Addis Ababa using a grap-sampling technique. All Enterobacteriaceae were screened for ESBLs production using cefotaxime and ceftazidime as per 29th CLSI guideline. Each screen positive for ESBLs production was confirmed by the combination disk method (CDT) and their antibiotic susceptibility pattern was done using the Kirby–Bauer disk diffusion method on Muller Hinton agar (MHA). Data were entered and summarized using SPSS version 20 software.

Results

Of all Enterobacteriaceae, 48.3% were confirmed ESBLs-pE. The highest ratio of ESBLs-PE was observed in the adult ward (66.7%) and laundry unit effluent (58.8%). The highest ESBL producers were E. coli (21.8%) and K. pneumoniae (4.8%). The most elevated resistance level of ESBL producers were observed to cefotaxime (95.8%) and amoxicillin/clavunalate (93%). 64% of tested Enterobacteriaceae isolates were multi drug resistant (MDR).

Conclusions

Higher magnitude of MDR and ESBLs-pE were present in the hospital wastewater. The majority of them were in the adult ward and laundry unit effluents. The most frequent ESBLs-pE was among E.coli and K. pneumoniae. Hence, Consistent infection prevention and control procedures should be in practice at each ward/unit.

Characterization of antibiotic resistance genes and bacteria in a municipal water resource recovery facility

Municipal water resource recovery facilities (WRRFs) are important sources of antibiotic-resistant bacteria and genes (ARB and ARGs). In this study, antibiotic-resistant total heterotrophic bacteria (THB_R ) counts (CFU/ml) cultivated from influent, effluent of activated sludge process, and outflow of disinfection unit of an urban WRRF were investigated for the presence of 16, 32, 64, and 128 μg/ml of nine antibiotics. The isolates of Pseudomonas spp., Acinetobacter spp., and Escherichia coli obtained from effluent of activated sludge process were subjected for molecular identification by detecting the 16S rRNA gene sequences. Additionally, using the polymerase chain reaction method (PCR), the isolates were investigated for the presence of bla_SHV , bla_TEM , bla_CTX-M , bla_VIM , sul1, and qnrS genes. According to the results, the abundance of THB_R counts was not significantly reduced by the biological treatment except for cefixime and sulfamethoxazole; it also increased for some antibiotics after disinfection unit. The average removal efficiency of THB_R resistant to ciprofloxacin, sulfamethoxazole, and ceftazidime were 7.9 ± 1.7%, 41.8 ± 2.1%, and 14.4 ± 6.2%, respectively. Also, all the tested isolates were resistant to at least four antibiotics. For all antibiotics, the resistance ratio (THB_R /THB) significantly increased in the effluent and after chlorination unit. Among 12 resistant isolates, bla_TEM and sul1 genes were the most frequently detected ones involved in 92% and 83% of the isolates, respectively. Both bla_TEM and sul1 genes were found in 100% of E. coli, and 83% and 67% of Pseudomonas spp. isolates, respectively. Further efforts are necessary to limit the transmission of ARB and ARGs from WRRFs into the environment and prevent human health threats. PRACTITIONER POINTS: The ratio of resistance significantly increased after biological treatment. Up to 40% of heterotrophic bacteria in the effluent was antibiotic resistant. bla_TEM and sul1 genes were more prevalent (92%) in all isolates of bacteria. Both bla_TEM and sul1 genes were found in 100% of E. coli isolates. Pseudomonas spp. holds bla_TEM and sul1 genes in 83% and 67% of isolates, respectively.

Antibiotic resistance of Pseudomonas aeruginosa isolated from hospital wastewater in the Czech Republic

Resistant bacteria may leave the hospital environment through wastewater. The opportunistic pathogen Pseudomonas aeruginosa, due to its intrinsic resistance to many antibiotics and its ability to easily acquire antibiotic resistance determinants, poses a significant threat to public health. The aim of this study was to evaluate the antibiotic resistance profiles of cultivated P. aeruginosa in untreated hospital effluents in the Czech Republic. Fifty-nine P. aeruginosa strains isolated from six hospital wastewaters were tested for antimicrobial susceptibility through the disc diffusion method against seven antimicrobial agents. Resistance was found in all antibiotics tested. The highest resistance values were observed for ciprofloxacin (30.5%), gentamicin (28.8%), and meropenem (27.2%). The P. aeruginosa isolates also exhibited resistance to ceftazidime (11.5%), amikacin (11.5%), piperacillin-tazobactam (11.5%), and aztreonam (8.5%). Seventeen strains of P. aeruginosa (28.8%) were classified as multidrug-resistant (MDR). The results of this study revealed that antibiotic-resistant strains are commonly present in hospital wastewater and are resistant to clinically relevant antipseudomonal drugs. In the absence of an appropriate treatment process for hospital wastewater, resistant bacteria are released directly into public sewer networks, where they can serve as potential vectors for the spread of antibiotic resistance.

Performance evaluation of ozonation for removal of antibiotic-resistant Escherichia coli and Pseudomonas aeruginosa and genes from hospital wastewater

The performance of ozonation for the removal of antibiotic-resistant bacteria (ARB) and antibiotic resistance genes (ARGs) using Escherichia coli and Pseudomonas aeruginosa carrying ARGs from hospital wastewaters was evaluated in this study. Bacterial inactivation was determined using plate count methods and real time PCR for ARG damage (Sul1, bla_tem, bla_ctx, bla_vim and qnrS). The reduction rate of bacterial cells and ARGs was increased by different amounts of transferred ozone dose from 11 to 45 mg/L. The concentration of 10⁸ cfu/ml bacteria was reduced  to an acceptable level by ozone treatment after a 5 min contact time,  Although the removal rate was much higher for concentrations of 10⁶ cfu/ml and 10⁴ cfu/ml bacteria. Overall, the tendency of gene reduction by ozonation from more to less was 16S rRNA > sul1 > bla_tem > bla_ctx > qnrS > bla_vim. Given that plasmid-borne ARGs can potentially be transferred to other bacteria even after the disinfection process, our results can provide important insights into the fate of ARGs during hospital wastewater ozonation.

High burden of multidrug resistant bacteria detected in Little Akaki River

Spread of antimicrobial-resistant bacteria between humans and animals occurs when the environment is contaminated with animal and human wastes. A total of 30 samples were collected from the Akaki river to identify antimicrobial-resistant bacteria. Bacterial enumeration and characterization was done by spreading serially diluted water samples on MacConkey agar. Sixty four bacterial isolates were identified and susceptibility tested using VITEK 2. The most frequently identified bacteria were Providencia alcalifaciens 10 (15.6%), Kluyvera cryocrescens 9 (14.1%) and Citrobacter freundii 7(10.9%), respectively. Multiple drug resistant bacteria were identified, constituting 17 (28%) of the 64 identified isolates. Multiple antimicrobial resistance (MAR) index of the six sites laid in the range 0.13-0.27, being the highest score located downstream of all the sampling sites. Species MAR index varied from 0.12 to 0.40. Out of 64 isolates, 54 (84.4%) of them were resistant to Ampicillin. On the contrary, most of the isolates were sensitive to Amikacin and meropenem. In conclusion, our findings indicated E.coli count was above the WHO permissible levels. The predominant isolates were P. alcalifaciens, and C. freundii. The MAR index of major isolates was greater than two, implying the study sites were exposed to high-risk sources of human or animal contamination.

Knowledge, attitudes and practices of animal farm owners/workers on antibiotic use and resistance in Amhara region, north western Ethiopia

Inappropriate use of antibiotics in animal and human plays a role in the emergence and spread of bacteria resistant to antibiotics which threatens human health significantly. Although extensive use of these antibiotics could contribute to the development of drug resistance, information on the knowledge, attitude and practice of antimicrobial resistance and use among animal farm owners/workers in north western Ethiopia is rare. The objective of the present study was to assess knowledge, attitude and practice of animal farm owner/workers towards antibiotic resistance and use in Amhara regional state north western Ethiopia. A cross sectional study was conducted in selected cities of Amhara regional state from January to February, 2020. Data was collected from 91 participants using structured questionnaire and analyzed using SPSSS version 23. The results showed that 96.7% of respondents gave antibiotics to treat their livestock from different sources. Most of the respondents bought their antibiotics from private pharmacies without prescription and the most frequently mentioned antibiotics used to treat animal diseases was tetracycline (76.9%), followed by ampicillin (72.5%). Although, 90.1% of the animal farm owners heard about antibiotics and antibiotic resistance from different sources, they did not know the factors contributing to the transmission of resistant bacteria to humans and the impact of antibiotic resistance on human and animals' health. Using the mean score 4.44 ± 0.15 as the cut-off, half of the animal farm owners/workers had good knowledge about antimicrobial resistance and use. 52.5% of animal farm owners/workers had positive attitudes towards wise antibiotic use and resistance with a mean score of 28.4 ± 0.5. However, 52.75% participants had poor practice with the mean score of practice 4.95 ± 0.17. Better knowledge, positive attitudes and better practices on antibiotic use and resistance were associated with farm owners/workers who engaged in higher education. Although poor awareness on antimicrobial resistance was perceived by 76.9% of respondents as very important factors that contribute to increasing antibiotic resistance, increasing the use of complementary treatments was perceived by the majority of respondents as very important strategies that contribute to reduce antibiotic use and resistance. The current study disclosed that there is low level of awareness among animal farm owners about the correct use of antibiotics and resistance. It is necessary to raise awareness, develop and implement interventions to reduce antimicrobial use and antibiotic resistance in the study area.

Taxonomic and Functional Distribution of Bacterial Communities in Domestic and Hospital Wastewater System: Implications for Public and Environmental Health

The discharge of untreated hospital and domestic wastewater into receiving water bodies is still a prevalent practice in developing countries. Unfortunately, because of an ever-increasing population of people who are perennially under medication, these wastewaters contain residues of antibiotics and other antimicrobials as well as microbial shedding, the direct and indirect effects of which include the dissemination of antibiotic resistance genes and an increase in the evolution of antibiotic-resistant bacteria that pose a threat to public and environmental health. This study assessed the taxonomic and functional profiles of bacterial communities, as well as the antibiotic concentrations in untreated domestic wastewater (DWW) and hospital wastewater (HWW), using high-throughput sequencing analysis and solid-phase extraction coupled to Ultra-high-performance liquid chromatography Mass Spectrometry (UHPLC–MS/MS) analysis, respectively. The physicochemical qualities of both wastewater systems were also determined. The mean concentration of antibiotics and the concentrations of Cl⁻, F⁻ and PO₄³ were higher in HWW samples than in DWW samples. The phylum Firmicutes was dominant in DWW with a sequence coverage of 59.61% while Proteobacteria was dominant in HWW samples with a sequence coverage of 86.32%. At genus level, the genus Exiguobacterium (20.65%) and Roseomonas (67.41%) were predominant in DWW and HWW samples, respectively. Several pathogenic or opportunistic bacterial genera were detected in HWW (Enterococcus, Pseudomonas and Vibrio) and DWW (Clostridium, Klebsiella, Corynebacterium, Bordetella, Staphylocccus and Rhodococcus) samples. Functional prediction analysis indicated the presence of beta-lactam resistance, cationic antimicrobial peptide (CAMP) resistance and vancomycin resistance genes in HWW samples. The presence of these antibiotic resistance genes and cassettes were positively correlated with the presence of pathogens. These findings show the risk posed to public and environmental health by the discharge of untreated domestic and hospital wastewaters into environmental water bodies.

Distribution and antimicrobial resistance profile of bacteria recovered from sewage system of health institutions found in Hawassa, Sidama Regional State, Ethiopia: A descriptive study

Objectives

The aim of the study was to determine the distribution and antimicrobial susceptibility profile of bacteria recovered from the sewage systems of health institutions found in Hawassa, Sidama Regional State, Ethiopia.

Methods

A cross-sectional study was conducted from 20 October 2020 to 1 December 2020. A total of 27 sewage samples were collected at two points, namely, before entering the septic tank and from the septic tank of seven health institutions. Samples were inoculated onto Mannitol salt agar, Blood agar, and MacConkey agar, and incubated for 24 h at 37°C. Bacteria were identified using colony morphology, Gram staining, and biochemical tests. An antimicrobial susceptibility test was performed using the Kirby-Bauer disk diffusion method. Data were analyzed by SPSS, version 25, and results were presented in text and tables.

Results

All sewage samples (n = 27) examined in the current study contained potential pathogenic bacteria. Overall, 129 different types of bacteria were identified. Of isolated bacteria, 14 (10.8%) were Gram positive, while 115 (89.2%) were Gram negative. The most prevalent bacteria were Escherichia coli (n = 27, 20.9%) followed by Shigella species (n = 26, 20.2%), Pseudomonas species (n = 25, 19.4%), Salmonella species (n = 25, 19.4%), Staphylococcus aureus (n = 14, 10.9%), and Klebsiella species (n = 12, 9.3%). All bacteria were susceptible to azithromycin. About 80% of bacteria were resistant to ampicillin, whereas greater than 80% of bacteria were susceptible to norfloxacin, ciprofloxacin, and gentamicin.

Conclusion

All sewage systems of health institutions included in the current study contained different types of pathogenic bacteria, which are resistant to commonly prescribed antibiotics.

High Burden of Antibiotic-Resistant Bacteria from Wastewater in Ethiopia: A Systematic Review

Background

Currently, antibiotic-resistant bacteria (ARB) have become a serious global problem and considered as One Health challenge. Despite, wastewater contains a wide range of microbial pathogens and plays a significant role in the dissemination of ARB in the environment. However, it is the most overlooked in developing countries, particularly in Ethiopia.

Methods

Different article searching devices like PubMed, Web of Science, Scopus, and Google Scholar were used to select research article by using the key terms. Hand search using a reference list is also used to retrieve the article. Preferred reporting items for systematic review and meta-analysis (PRISMA) guideline was used for literature search strategy, selection of publications, data extractions, and reporting result for the review process.

Results

A total of seven original research articles were included from a total of 35,999 research articles obtained from the different searching techniques. The selected articles were used, the same study design and laboratory methods to isolate different types of resistant bacteria. All studies isolate pathogenic bacteria and highlighted the presence of resistant bacteria for multiple antibiotics.

Conclusion

Multidrug resistance (MDR) bacteria were isolated from wastewater. This is an indication for the possible presence of pathogenic organisms that are discharged into the receiving environment probably waterbodies (lake and revers) posing risk to public health, animal, and environment. In Ethiopia the coverage of safe water supply is poor.  This obligated the society to use untreated water from rivers, lakes and others. The outlet of most urban sewage from hospital, hotels, and industries are directly running to those water bodies due to lack of proper wastewater management system.  Therefore ARB is a direct threat to those people that use those water bodies.

Hospital wastewater treatment reduces NDM-positive bacteria being discharged into water bodies

New Delhi metallo-β-lactamase-1 (NDM-1) is a novel type of metallo-β-lactamase (MBL) associated with Enterobacteriaceae constitutes an important growing public health threat. The present study aims to characterize the NDM-1 producing Gram-negative bacteria (GNB) from the effluents of two tertiary care hospitals in Mangalore, South India and to profile their antibiotic resistance pattern. A total of 134 GNB were isolated from 30 hospital wastewater samples (treated and untreated) and analyzed. High-level resistance among untreated effluent sample was found toward nalidixic acid (74.52%), followed by cefotaxime (72.64%) and ampicillin (66.03%). Among the treated effluent isolates, the high resistance was found toward ampicillin (85.71%) followed by cefotaxime (85.71%) and piperacillin-tazobactam (53.57%). From untreated effluent isolates, 9 were NDM-1 positive by PCR; no isolates from treated effluent samples harbored bla_NDM-1 . Untreated hospital wastewater is found to be important reservoirs of antibiotic-resistant bacteria carrying bla_NDM-1 , and the presence of such bacteria in the effluents is a matter of great concern because they can contribute the antibiotic resistance to the natural environment. However, the absence of NDM in treated effluents emphasizes the importance of effluent treatment in reducing the dissemination of antibiotic-resistant bacteria. PRACTITIONER POINTS: Hospital wastewater is the important reservoir of antibiotic-resistant bacteria especially metallo-β-lactamase producers (NDM-1). Wastewater treatment procedures in hospitals reduce the NDM isolates in the treated effluent. Thereby reduces the risk of resistance spread in the environment.

Photo-inactivation of bacteria in hospital effluent via thiolated iron-doped nanoceria

Hospital wastewater is a major contributor of disease-causing microbes and the emergence of antibiotic resistant bacteria. In this study, thiolated iron-doped nanoceria was synthesised and tested for killing of microbes from hospital effluent. These particles were designed to inhibit the efflux pumps of the bacteria found in hospital effluent with further ability to activate in visible light via iron doping thus generating tunable amount of reactive oxygen species (ROS). The quantum yield of the ROS generated by the nanoceria was 0.67 while the ROS types produced were singlet oxygen (36%), hydroxyl radical (31%) and hydroxyl ions (32%), respectively. The particles were initially synthesised through green route using Foeniculum vulgare seeds extract and were annealed at 200°C and further coated with thiolated chitosan to enhance the solubility and efflux pump inhibition. X-ray diffraction confirmed the polycrystalline nature of nanoparticles and uniform spherical shape with 30 nm size, confirmed by scanning electron microscope. The nanoparticles exhibited 100% bactericidal activity at 100 µg/mL against all the isolated bacteria. The enhanced bactericidal effect of iron-doped nanoceria could be attributed to efflux inhibition via thiolated chitosan as well as the production of ROS upon illumination in visible light, causing oxidative stress against microbes found in hospital effluent.

Microbiology of hospital wastewater

The study of hospital wastewater (HWW) microbiology is important to understand the pollution load, growth of particular pathogenic microbes, shift and drift in microbial community, development and spread of antibiotic resistance in microbes, and subsequent change in treatment efficiencies. This chapter investigates the potential microbes such as bacteria, viruses, fungi, and parasites present in HWW along with the diseases associated and methods of treatment used. Due to the indiscriminate release of antibiotics from hospitals, HWW serves as a hotspot for emergence of antibiotic-resistance genes (ARGs) and antibiotic-resistance bacteria. This chapter discusses the ARGs occurrence in HWW, their prevalence in the environment, the molecular tools used for identification, and different mechanisms of horizontal gene transfer. Thus better understanding of the microbiology of HWW could further help in development of advanced treatment technologies for effective removal of microbes and their bioproducts (toxins and infectious nucleic acid) from HWW and contaminated water.