Presence of carbapenem-resistant bacteria in soils affected by illegal waste dumps

Hospital and municipal wastewater as a source of carbapenem-resistant Acinetobacter baumannii and Pseudomonas aeruginosa in the environment: a review

The increase in the prevalence of carbapenem-resistant Gram-negative bacteria, in particular Acinetobacter baumannii (CRAB) and Pseudomonas aeruginosa (CRPA), poses a serious threat for public health worldwide. This article reviews the alarming data on the prevalence of infections caused by CRAB and CRPA pathogens and their presence in hospital and municipal wastewater, and it highlights the environmental impact of antibiotic resistance. The article describes the key role of antibiotic resistance genes (ARGs) in the acquisition of carbapenem resistance and sheds light on bacterial resistance mechanisms. The main emphasis was placed on the transfer of ARGs not only in the clinical setting, but also in the environment, including water, soil, and food. The aim of this review was to expand our understanding of the global health risks associated with CRAB and CRPA in hospital and municipal wastewater and to analyze the spread of these micropollutants in the environment. A review of the literature published in the last decade will direct research on carbapenem-resistant pathogens, support the implementation of effective preventive measures and interventions, and contribute to the development of improved strategies for managing this problem.

High Prevalence of Antibiotic Resistance Bacteria Isolated From Bahir Dar City Municipal Solid Waste Dumpsite, North West Ethiopia

The emergence and spread of antibiotic resistance (ABR) have been a public health challenge globally. The burden is even higher in low-income countries where there is a lack of appropriate healthcare systems, and inappropriate antibiotic disposal practices and utilization. Due to poor solid waste disposal practices in developing nations, municipal solid waste dumpsite (MSWDS) can be a reservoir for ABR bacteria. However, only a few studies demonstrated the prevalence of ABR in non-clinical environments such as MSWDS. This study assessed the prevalence of ABR bacteria at Bahir Dar City MSWDS, to understand the public health risks related to poor solid waste disposal systems. Nine soil samples were collected from the dumpsite. Bacteria were isolated, identified and tested for ABR. Seventy-one distinct colonies were isolated from all samples and identified into 10 bacterial genera based on morphological features and biochemical tests. For ABR tests, gentamicin (GN, 10 μg), streptomycin (ST, 30 μg), tetracycline (TE, 30 μg), ciprofloxacin (CIP, 5 μg), nalidixic acid (NAA, 30 μg), sulfonamide (SA, 250 μg), chloramphenicol (C, 30 μg), erythromycin (E, 15 μg), vancomycin (V, 30 μg), and amoxicillin (AMX, 25 μg) were used. The most frequently isolated bacteria were Staphylococcus (23%) followed by Escherichia species (17%). Ten isolates related to Bacillus spp. were excluded from the antibiotic sensitivity test as there is no standard regarding this genus in the Clinical and Laboratory Standards Institute. The overall antibiotic résistance rate was 95.08%, and most isolates were found to be resistant to amoxicillin (100%), nalidixic acid (75.5%), and vancomycin (75%). Substantial proportions of the isolates were also resistant to tetracycline (55.35%), streptomycin (54.5%), and sulfonamide (50%). The overall multidrug resistance (MDR) rate was 36.06%. This high level of ABR calls for urgent intervention in waste management systems and regular surveillance programs.

Soil-specific responses in the antibiotic resistome of culturable Acinetobacter spp. and other non-fermentative Gram-negative bacteria following experimental manure application

Acinetobacter spp. and other non-fermenting Gram-negative bacteria (NFGNB) represent an important group of opportunistic pathogens due to their propensity for multiple, intrinsic, or acquired antimicrobial resistance (AMR). Antimicrobial resistant bacteria and their genes can spread to the environment through livestock manure. This study investigated the effects of fresh manure from dairy cows under antibiotic prophylaxis on the antibiotic resistome and AMR hosts in microcosms using pasture soil. We specifically focused on culturable Acinetobacter spp. and other NFGNB using CHROMagar Acinetobacter. We conducted two 28-days incubation experiments to simulate natural deposition of fresh manure on pasture soil and evaluated the effects on antibiotic resistance genes (ARGs) and bacterial hosts through shotgun metagenomics. We found that manure application altered the abundance and composition of ARGs and their bacterial hosts, and that the effects depended on the soil source. Manure enriched the antibiotic resistome of bacteria only in the soil where native bacteria had a low abundance of ARGs. Our study highlights the role of native soil bacteria in modulating the consequences of manure deposition on soil and confirms the potential of culturable Acinetobacter spp. and other NFGNB to accumulate AMR in pasture soil receiving fresh manure.

Characterization of Burkholderia cepacia complex from environment influenced by human waste

The natural environment is a primary source of infections caused by members of Burkholderia cepacia complex (BCC), but the release of human waste may in return enrich the natural environment with clinically relevant BCC. Seven BCC isolates from environment influenced by human liquid or solid waste across Croatia, and one clinical isolate was characterised. B. multivorans recovered from the soil at illegal dumpsite belonged to sequence type (ST)19; B. ambifaria from the agricultural soil fertilized with swine or poultry manure to ST927 or new ST; B. cenocepacia from creek sediment, river water and wound swab to new STs. Antimicrobial susceptibility of isolates ranged from sensitive to multidrug-resistant. A variety of bla_TEM genes was confirmed in isolates. Isolates expressed the virulence factors and survived in river water during 50 days. The BCC present natural environments influenced by the human waste are of clinical relevance and a potential source of sporadic infections.

Assessment of Physicochemical, Microbiological and Toxicological Hazards at an Illegal Landfill in Central Poland

This study aimed to assess the physicochemical, microbiological and toxicological hazards at an illegal landfill in central Poland. The research included the analysis of airborne dust (laser photometer), the number of microorganisms in the air, soil and leachate (culture method) and the microbial diversity in the landfill environment (high-throughput sequencing on the Illumina Miseq); the cytotoxicity (PrestoBlue) and genotoxicity (alkaline comet assay) of soil and leachate were tested. Moreover, an analysis of UHPLC-Q-ToF-UHRMS (ultra-high-performance liquid chromatography-quadrupole-time-of-flight ultrahigh-resolution mass spectrometry) was performed to determine the toxic compounds and microbial metabolites. The PM₁ dust fraction constituted 99.89% and 99.99% of total dust and exceeded the threshold of 0.025 mg m⁻³ at the tested locations. In the air, the total number of bacteria was 9.33 × 10¹–1.11 × 10³ CFU m⁻³, while fungi ranged from 1.17 × 10² to 4.73 × 10² CFU m⁻³. Psychrophilic bacteria were detected in the largest number in leachates (3.3 × 10⁴ to 2.69 × 10⁶ CFU mL⁻¹) and in soil samples (8.53 × 10⁵ to 1.28 × 10⁶ CFU g⁻¹). Bacteria belonging to Proteobacteria (42–64.7%), Bacteroidetes (4.2–23.7%), Actinobacteria (3.4–19.8%) and Firmicutes (0.7–6.3%) dominated. In the case of fungi, Basidiomycota (23.3–27.7%), Ascomycota (5.6–46.3%) and Mortierellomycota (3.1%) have the highest abundance. Bacteria (Bacillus, Clostridium, Cellulosimicrobium, Escherichia, Pseudomonas) and fungi (Microascus, Chrysosporium, Candida, Malassezia, Aspergillus, Alternaria, Fusarium, Stachybotrys, Cladosporium, Didymella) that are potentially hazardous to human health were detected in samples collected from the landfill. Tested leachates and soils were characterised by varied cyto/genotoxins. Common pesticides (carbamazepine, prometryn, terbutryn, permethrin, carbanilide, pyrethrin, carbaryl and prallethrin), quaternary ammonium compounds (benzalkonium chlorides), chemicals and/or polymer degradation products (melamine, triphenylphosphate, diphenylphtalate, insect repellent diethyltoluamide, and drugs (ketoprofen)) were found in soil and leachate samples. It has been proven that the tested landfill is the source of the emission of particulate matter; microorganisms (including potential pathogens) and cyto/genotoxic compounds.

Environmental and Pathogenic Carbapenem Resistant Bacteria Isolated from a Wastewater Treatment Plant Harbour Distinct Antibiotic Resistance Mechanisms

Wastewater treatment plants are important reservoirs and sources for the dissemination of antibiotic resistance into the environment. Here, two different groups of carbapenem resistant bacteria-the potentially environmental and the potentially pathogenic-were isolated from both the wastewater influent and discharged effluent of a full-scale wastewater treatment plant and characterized by whole genome sequencing and antibiotic susceptibility testing. Among the potentially environmental isolates, there was no detection of any acquired antibiotic resistance genes, which supports the idea that their resistance mechanisms are mainly intrinsic. On the contrary, the potentially pathogenic isolates presented a broad diversity of acquired antibiotic resistance genes towards different antibiotic classes, especially β-lactams, aminoglycosides, and fluoroquinolones. All these bacteria showed multiple β-lactamase-encoding genes, some with carbapenemase activity, such as the bla_KPC-type genes found in the Enterobacteriaceae isolates. The antibiotic susceptibility testing assays performed on these isolates also revealed that all had a multi-resistance phenotype, which indicates that the acquired resistance is their major antibiotic resistance mechanism. In conclusion, the two bacterial groups have distinct resistance mechanisms, which suggest that the antibiotic resistance in the environment can be a more complex problematic than that generally assumed.

Status quo of illegal dumping research: Way forward

Due to the rapid social and economic development, the past decades have witnessed the improvement of human being's quality of life and the speedy development of the construction industry. Meanwhile, the illegal dumping of solid waste has presented a significant issue. By using the method of systematic review, this study critically examined the literature related to illegal dumping that were published since 1990, and analyzed the current status and future trends of related research. Results show that the current studies on illegal dumping mainly focus on four perspectives: environmental science and toxicology, economics, management, and the use of emerging technologies. This critical review revealed that although the issue of illegal dumping has been widely recognized in recent years, some questions remain unanswered. Therefore, a future research agenda is proposed. These include: (1) Identifying the migration of pollutants in the food chain during the illegal dumping; (2) Implementing targeted treatment of illegal dumping pollutants; (3) Improving the stakeholder decision analysis model; (4) Expanding the scope of research on stakeholders of illegal dumping; (5) Formulating an unified evaluation standard for the related costs of illegal dumping; (6) Strengthening the evaluation of the interaction effects of influencing factors; (7) Comparing the effects of different types of factors; (8) the exploration of other influencing factors; (9) Analyzing illegal dumping by combining big data with the amount of solid waste; (10) Combining with monitoring to analyze the illegal dumping of household waste.

Metal-loaded zeolite remediation of soils contaminated with pandrug-resistant Acinetobacter baumannii

Due to the development of resistance to antimicrobial agents, bacterium Acinetobacter baumannii is nowadays a leading cause of nosocomial outbreaks. Clinically relevant A. baumannii outside hospital settings including natural soils affected by human waste represents a public-health risk for humans and animals. The aim of this study was to investigate the potential of metal-loaded zeolites to eliminate viable A. baumannii from artificially contaminated natural soils. A. baumannii isolate was subjected to the activity of natural zeolitised tuff (NZ) and Cu-modified (CuNZ) or Ag-modified zeolite (AgNZ) in wet, slightly acidic terra rossa and slightly alkaline red palaeosol. A. baumannii survived in terra rossa and red palaeosol supplemented with 1 wt% of NZ for seven days and four months, respectively. The addition of 1 wt% of CuNZ to terra rossa and red palaeosol shortened the survival of A. baumannii to three and 14 days, respectively. The addition of 0.1 wt% of AgNZ to both soils resulted in complete removal of viable A. baumannii within 1 h of contact, while the total native heterotrophic bacterial counts remained high. Since AgNZ is prepared with a simple modification of cost-effective and environmentally friendly natural zeolite, it is a promising material for the remediation of soils contaminated with pandrug-resistant A. baumannii.

Urban and agricultural soils in Southern California are a reservoir of carbapenem-resistant bacteria

Carbapenems are last‐resort β‐lactam antibiotics used in healthcare facilities to treat multidrug‐resistant infections. Thus, most studies on identifying and characterizing carbapenem‐resistant bacteria (CRB) have focused on clinical settings. Relatively, little is still known about the distribution and characteristics of CRBs in the environment, and the role of soil as a potential reservoir of CRB in the United States remains unknown. Here, we have surveyed 11 soil samples from 9 different urban or agricultural locations in the Los Angeles–Southern California area to determine the prevalence and characteristics of CRB in these soils. All samples tested contained CRB with a frequency of <10 to 1.3 × 10⁴ cfu per gram of soil, with most agricultural soil samples having a much higher relative frequency of CRB than urban soil samples. Identification and characterization of 40 CRB from these soil samples revealed that most of them were members of the genera Cupriavidus, Pseudomonas, and Stenotrophomonas. Other less prevalent genera identified among our isolated CRB, especially from agricultural soils, included the genera Enterococcus, Bradyrhizobium, Achromobacter, and Planomicrobium. Interestingly, all of these carbapenem‐resistant isolates were also intermediate or resistant to at least 1 noncarbapenem antibiotic. Further characterization of our isolated CRB revealed that 11 Stenotrophomonas, 3 Pseudomonas, 1 Enterococcus, and 1 Bradyrhizobium isolates were carbapenemase producers. Our findings show for the first time that both urban and agricultural soils in Southern California are an underappreciated reservoir of bacteria resistant to carbapenems and other antibiotics, including carbapenemase‐producing CRB.

Removal of emerging pathogenic bacteria using metal-exchanged natural zeolite bead filter

Hospital wastewaters can become a route for dissemination of antibiotic-resistant bacteria to the environment if not properly treated. Some of these bacteria are able to survive conventional disinfection treatments (e.g. chlorination, UV irradiation), which evokes the need for novel disinfection methods. The metal-exchanged zeolites were tested as novel antibacterial agents for wastewater treatment. The natural zeolite clinoptilolite enriched with silver (AgNZ) showed far better antibacterial activity towards hospital pathogenic bacterium Acinetobacter baumannii when compared with copper-exchanged zeolite (CuNZ), with minimal bactericidal concentration of 0.25-2 (AgNZ) compared with 32-64 mg L^-1 (CuNZ) in a batch system and respective log 5.6 reduction compared with log 0.5 reduction in a flow system with pure bacterial culture. In the flow system with real effluent wastewater from the treatment plant, the removal of carbapenem-resistant bacteria using AgNZ was 90-100% during the 4 days of the experimental run. These results indicate that the AgNZ efficiently removes pathogenic bacteria from the wastewater, including A. baumannii, and is promising as a disinfectant material in a bead filter system.