Wastewater surveillance of antibiotic resistance and class 1 integron-integrase genes: Potential impact of wastewater characteristics on genes profile

Antibiotic resistance (AR) is a major global health concern, but current surveillance efforts primarily focus on healthcare settings, leaving a lack of understanding about AR across all sectors of the One Health approach. To bridge this gap, wastewater surveillance provides a cost-effective and efficient method for monitoring AR within a population. In this study, we implemented a surveillance program by monitoring the wastewater effluent from two large-scale municipal treatment plants situated in Isfahan, a central region of Iran. These treatment plants covered distinct catchment regions and served a combined population about two million of residents. Furthermore, the effect of physicochemical and microbial characteristics of wastewater effluent including biological oxygen demand (BOD), chemical oxygen demand (COD), total suspended solids (TSS), temperature, total coliforms and Escherichia coli concentration on the abundance of ARGs (blaCTX-M, tetW, sul1, cmlA, and ermB) and class 1 integron-integrase gene (intI1) were investigated. Sul1 and blaCTX-M were the most and least abundant ARGs in the two WWTPs, respectively. Principal Component Analysis showed that in both of the WWTPs all ARGs and intI1 gene abundance were positively correlated with effluent temperature, but all other effluent characteristics (BOD, COD, TSS, total coliforms and E. coli) showed no significant correlation with ARGs abundance. Temperature could affect the performance of conventional activated sludge process, which in turn could affect the abundance of ARGs. The results of this study suggest that other factors than BOD, COD and TSS may affect the ARGs abundance. The predicted AR could lead to development of effective interventions and policies to combat AR in the clinical settings. However, further research is needed to determine the relationship between the AR in wastewater and clinical settings as well as the effect of other influential factors on ARGs abundance.

Human viral pathogens in the wastewater-source water-drinking water continuum: Evidence, health risks, and lessons for future outbreaks in low-income settings

Human viral pathogens, including SARS-CoV-2 continue to attract public and research attention due to their disruption of society, global health, and the economy. Several earlier reviews have investigated the occurrence and fate of SARS-CoV-2 in wastewater, and the potential to use such data in wastewater-based epidemiology. However, comprehensive reviews tracking SARS-CoV-2 and other viral pathogens in the wastewater-water-drinking water continuum and the associated risk assessment are still lacking. Therefore, to address this gap, the present paper makes the following contributions: (1) critically examines the early empirical results to highlight the occurrence and stability of SARS-CoV-2 in the wastewater-source water-drinking water continuum, (2) discusses the anthropogenic and hydro(geo)logical processes controlling the circulation of SARS-CoV-2 in the wastewater-source water-drinking water continuum, (3) discusses the risky behaviour, drivers and high-risk settings in the wastewater-source water-drinking water continuum, (4) uses the available empirical data on SARS-CoV-2 occurrence in the wastewater-source water-drinking water continuum to discuss human health risks from multiple exposure pathways, gendered aspects of SARS-CoV-2 transmission via shared on-site sanitation systems, and (5) develops and risk mitigation strategy based on the available empirical evidence and quantitative human risk assessment data. Finally, it presents a comprehensive research agenda on SARS-CoV-2/COVID-19 to guide the mitigation of future similar outbreaks in low-income settings.

Combating antibiotic resistance using wastewater surveillance: Significance, applications, challenges, and future directions

The global increase of antibiotic resistance (AR) and resistant infections call for effective surveillance methods for understanding and mitigating (re)-emerging public health risks. Wastewater surveillance (WS) of antibiotic resistance is an emerging, but currently under-utilized decision-support tool in public health systems. Recent years have witnessed an increase in evidence linking antibiotic resistance in wastewaters to that of the community. To date, very few comprehensive reviews exist on the application of WS to understand AR and resistant infections in population. Current and emerging AR detection methods, and their merits and limitations are discussed. Wastewater surveillance has several merits relative to individual testing, including; (1) low per capita testing cost, (2) high spatial coverage, (3) low requirement for diagnostic equipment, and (4) detection of health threats ahead of real outbreaks. The applications of WS as an early warning system and decision support tool to understand and mitigate AR are discussed. Wastewater surveillance could be a tool of choice in low-income settings lacking resources and diagnostic facilities for individual testing. To demonstrate the utility of WS, empirical evidence from field case studies is presented. However, constraints still exist, including; (1) lack of standardized protocols, (2) the clinical utility and sensitivity of WS-based data, (3) uncertainties in relating WS data to pathogenic and virulent bacteria, and (4) whether or not AR in stools and ultimately wastewater represent the complete human resistome. Finally, further prospects are presented, include knowledge gaps on; (1) development of low-cost biosensors for AR, (2) development of WS protocols (sampling, processing, interpretation), (3) further pilot scale studies to understand the opportunities and limits of WS, and (4) development of computer-based analytical tools to facilitate rapid data collection, visualization and interpretation. Therefore, the present paper discusses the principles, opportunities, and constraints of wastewater surveillance applications to understand AR and safeguard public health.

Incidence of co-resistance to antibiotics and chlorine in bacterial biofilm of hospital water systems: Insights into the risk of nosocomial infections

The presence of biofilms in drinking water distribution systems (DWDS) in healthcare settings poses a considerable risk to the biological security of water, particularly when the biofilm bacteria demonstrate antimicrobial resistance characteristics. This study aimed to investigate the occurrence of antibiotic-resistant bacteria (ARB) in biofilms within DWDS of hospitals. The chlorine resistance of the isolated ARB was analyzed, and then chlorine-resistant bacteria (CRB) were identified using molecular methods. Additionally, the presence of several antibiotic resistance genes (ARGs) was monitored in the isolated ARB. Out of the 41 biofilm samples collected from hospitals, ARB were detected in 32 (78%) of the samples. A total of 109 colonies of ARB were isolated from DWDS of hospitals, with β-lactam resistant bacteria, including ceftazidime-resistant and ampicillin-resistant bacteria, being the most frequently isolated ARB. Analyzing of ARGs revealed the highest detection of aac6, followed by sul1 gene. However, the β-lactamase genes blaCTX-M and blaTEM were not identified in the ARB, suggesting the presence of other β-lactamase genes not included in the tested panel. Exposure of ARB to free chlorine at a concentration of 0.5 mg/l showed that 64% of the isolates were CRB. However, increasing the chlorine concentration to 4 mg/l decreased the high fraction of ARB (91%). The domi‌‌nant CRB identified were Sphingomonas, Brevundimonas, Stenotrophomonas, Bacillus and Staphylococcus with Bacillus exhibiting the highest frequency. The results highlight the potential risk of biofilm formation in the DWDS of hospitals, leading to the dissemination of ARB in hospital environments, which is a great concern for the health of hospitalized patients, especially vulnerable individuals. Surveillance of antimicrobial resistance in DWDS of hospitals can provide valuable insights for shaping antimicrobial use policies and practices that ensure their efficacy.

The bacterial biofilm resistome in drinking water distribution systems: A systematic review

Antibiotic resistance in drinking water systems poses human health risks. Earlier studies, including reviews on antibiotic resistance in drinking water systems are limited to the occurrence, behaviour and fate in bulk raw water and drinking water treatment systems. By comparison, reviews on the bacterial biofilm resistome in drinking water distribution systems are still limited. Therefore, the present systematic review investigates the occurrence, behaviour and fate and, detection methods of bacterial biofilm resistome in the drinking water distribution systems. A total of 12 original articles drawn from 10 countries were retrieved and analyzed. Antibiotic resistant bacteria and antibiotic resistance genes detected in biofilms include those for sulfonamides, tetracycline, and beta-lactamase. The genera detected in biofilms include Staphylococcus, Enterococcus, Pseudomonas, Ralstonia, Mycobacteria, as well as Enterobacteriaceae family and other gram-negative bacteria. The presence of Enterococcus faecium, Staphylococcusaureus, Klebsiella pneumoniae, Acinetobacterbaumannii, Pseudomonas aeruginosa, and Enterobacter species (ESKAPE bacteria) among the detected bacteria points to potential human exposure and health risks especially for susceptible individuals via the consumption of drinking water. Besides, the effects of water quality parameter and residual chlorine, the physico-chemical factors controlling the emergence, persistence and fate of the biofilm resistome are still poorly understood. Culture-based methods, and molecular methods, and their advantages and limitations are discussed. The limited data on the bacterial biofilm resistome in drinking water distribution system points to the need for further research. To this end, future research directions are discussed including understanding the formation, behaviour, and fate of the resistome and the controlling factors.

Microbial indicators in municipal solid waste compost and their fate after land application of compost

Despite the extensive agricultural use of municipal solid waste (MSW) compost, there is little information about microbial characteristics of the MSW compost and fate of microorganisms following land application. This study was designed to determine the microbial quality and germination index (GI) of the MSW compost as well as fate of indicator microorganisms after application of MSW compost. The results showed a high fraction of samples are immature (GI < 80). In 27% and 16% of samples fecal coliforms and Salmonella were detected in a range exceeding the recommended value for unrestricted application of compost, respectively. HAdV was also detected in 62% of samples. Fecal enterococci were detected with relatively high concentrations in all samples and showed higher survival rate than other indicators in land-applied MSW compost. The results showed that climate condition significantly contributed to the decline of indicator bacteria in land-applied compost. The results highlight the need for further quality monitoring of compost to ensure that its application does not lead to environmental or human health problems. Furthermore, because of the high concentrations and high survival rate of enterococci in compost samples, they can be specifically proposed as an indicator microorganism for MSW compost quality monitoring.

Occurrence of enteric and non-enteric microorganisms in coastal waters impacted by anthropogenic activities: A multi-route QMRA for swimmers

The purpose of this study was to evaluate the microbial characteristics of coastal waters which are impacted by anthropogenic pollution as well as estimate the health risks associated with exposure to enteric and non-enteric microorganisms during swimming. Fecal indicator bacteria were highly detected in samples. Moreover, pathogenic and opportunistic microorganisms were found, with the highest frequency for Pseudomonas aeruginosa followed by Adenovirus 40/41, Acanthamoeba spp., Salmonella enterica, and Cryptosporidium parvum. The median risk of gastrointestinal illness through ingestion of water was estimated to be above the benchmark value of 0.05 per event recommended by WHO. Cryptosporidium followed by Adenovirus, showed higher illness risks than Salmonella. The potential risks of Acanthamoeba and P. aeruginosa were estimated to be low for both dermal and ocular exposure routes. However, there are uncertainties about the infectious fraction of pathogens existing in coastal waters and the delivered dose of microorganisms from dermal/ocular exposure during recreational activities.

Health Risk Assessment of Exposure to Bisphenol A in Polymeric Baby Bottles

In recent decades, paying attention to bisphenol A (BPA), as one of the endocrine disruptor compounds, has increased due to its harmful effects. Although, scattered studies have been conducted in order to measure BPA concentration migrated into polymeric baby bottles in different countries of the world, there are no review studies and evaluation with a global perspective in the field of BPA risk. Some of these studies indicated the potential risks and estrogenic effects associated with BPA in babies' daily intake. For this purpose, we reviewed the information on the migration levels of BPA into baby bottles has been reported in 10 countries. The potential risks associated with BPA through the daily intake as well as the estrogenic effect on 3 age groups of babies which include 0 to 6, 6 to 12, and 12 to 24 months were analyzed using the Monte Carlo simulation. Also, kinetic models were applied to predict the kinetics of the migration process of BPA. The median daily intake for 3 age groups was obtained as 191.1, 161.37, and 153.76 µg/kg/day, respectively; which indicated Hazard Index (HI) > 1. The median estrogenic effect for the 3 groups was estimated to be 0.021 ngE₂/L. The kinetics of contaminant transfer with Polynomial model at 2 temperatures of 24°C and 40°C showed a better fit with R ² = 0.99 and 0.91, respectively. Based on the risk assessment analysis conducted in the present study, the BPA migration in baby bottles appeared to be a health concern for babies. Therefore, it is needed to increase the safety level of bottles for babies as they are sensitive and vulnerable members of every society. Furthermore, in this study, only the investigation of the global situation of BPA in polymeric baby bottles was stated; therefore, more investigation about another potential sources of BPA in food chain is needed.

Quantification of human adenovirus in irrigation water-soil-crop continuum: are consumers of wastewater-irrigated vegetables at risk?

Because of health concerns regarding the presence of enteric viruses in wastewater effluents, this study was designed to investigate the occurrence of human adenovirus (HAdV) in the irrigation water-soil-crop continuum. Viral particles were extracted from wastewater and wastewater- or water-irrigated soil and crop samples and analyzed using real-time PCR. Concentration of fecal indicator bacteria (FIB) were also determined. Quantitative microbial risk assessment was performed to determine the HAdV illness risk associated with the consumption of wastewater-irrigated vegetables. HAdV-F was detected in 74% of wastewater effluent samples with a mean concentration of 38 Genomic Copy (GC)/mL. HAdV was also detected in wastewater-irrigated soil (2 × 102 GC/g) and crop (< 10 GC/g) samples, with no statistically significant difference in concentrations between wastewater- and freshwater-irrigated samples. The results showed no correlation between concentrations of FIB and HAdV in the analyzed samples. Mean probability of illness risk from consumption of wastewater-irrigated vegetables was 4 × 10-1 per person per year (pppy) which was about two orders of magnitude higher than the proposed value by WHO (10-3 pppy) for safe reuse of wastewater. This finding suggests that the wastewater reuse for irrigation of vegetables eaten raw could pose a threat to human health with respect to the risk of viral illness, signifying stricter management of wastewater reuse. However, because of uncertainties in the QMRA model, particularly the ratio of infectious to non-infectious virus particles, more data is required to validate the predicted risk. This information is especially important in arid and semi-arid regions where high temperatures, UV radiation intensity, and desiccation can efficiently inactivate microorganisms in the environment.

Occurrence of viruses in sewage sludge: A systematic review

Enteric viruses are of great importance in wastewater due to their high excretion from infected individuals, low removal in wastewater treatment processes, long-time survival in the environment, and low infectious dose. Among the other viruses, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) surveillance in wastewater systems has received particular attention as a result of the current COVID-19 epidemic. Viruses adhering to solid particles in wastewater treatment processes will end up as sewage sludge, and therefore insufficient sludge treatment may result in viral particles dissemination into the environment. Here, we review data on viruses' presence in sewage sludge, their detection and concentration methods, and information on human health issues associated with sewage sludge land application. We used combinations of the following keywords in the Scopus, Web of Science (WOS), and PubMed databases, which were published between 2010 and January 21th, 2022: sludge (sewage sludge, biosolids, sewage solids, wastewater solids) and virus (enteric virus, viral particles, viral contamination, SARS-CoV-2, coronavirus). The sources were searched twice, once with and then without the common enteric virus names (adenovirus, rotavirus, norovirus, enterovirus, hepatitis A virus). Studies suggest adenovirus and norovirus as the most prevalent enteric viruses in sewage sludge. Indeed, other viruses include rotavirus, hepatitis A virus, and enterovirus were frequently found in sewage sludge samples. Untreated biological sludge and thickened sludge showed more viral contamination level than digested sludge and the lowest prevalence of viruses was reported in lime stabilized sludge. The review reveals that land application of sewage sludge may pose viral infection risks to people due to accidently ingestion of sludge or intake of crops grown in biosolids amended soil. Moreover, contamination of groundwater and/or surface water may occur due to land application of sewage sludge.

Microbial characteristics of municipal solid waste compost: Occupational and public health risks from surface applied compost

Land application of MSW compost promotes the soil fertility and productivity, but there is concern about its chemical and microbial quality. Although, current microbial indicators of MSW compost are generally considered to be protective of human health, the use of these indicators doesn't adequately represent the presence of pathogens that might be more resistant to inactivation during composting process. This work aims evaluation of the microbial characteristics of MSW compost and estimation of the health risks associated with exposure to pathogens of potential concern in MSW compost. Although the recommended standards for fecal coliforms and Salmonella were met in a relatively high percentage of samples, there were detectable levels of microbial pathogens. The highest daily infection risk was estimated for Cryptosporidium (1.25 × 10^-3 per person) followed by Salmonella and Campylobacter, while the lowest related to adenovirus. Infection risks were low for both farmers and children in one-time exposure and all pathogen risks were decreased with increasing waiting time to near insignificant levels. However, the median annual risk of cryptosporidiosis or gastroenteritis was above the recommended value of 10^-3 per person per year. Because of potential presence of pathogens in MSW compost, some level of pathogen monitoring beyond conventional indicators may be required to estimate potential risks. The findings of this study could provide information to governments and local authorities in making decisions on measures to reduce risk from application of MSW compost. Further research is needed to obtain the reliable information about the inactivation of microorganisms in environment.

The air-borne antibiotic resistome: Occurrence, health risks, and future directions

Antibiotic resistance comprising of antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs) is an emerging problem causing global human health risks. Several reviews exist on antibiotic resistance in various environmental compartments excluding the air-borne resistome. An increasing body of recent evidence exists on the air-borne resistome comprising of antibiotic resistance in air-borne bioaerosols from various environmental compartments. However, a comprehensive review on the sources, dissemination, behavior, fate, and human exposure and health risks of the air-borne resistome is still lacking. Therefore, the current review uses the source-pathway-receptor-impact-mitigation framework to investigate the air-borne resistome. The nature and sources of antibiotic resistance in the air-borne resistome are discussed. The dissemination pathways, and environmental and anthropogenic drivers accounting for the transfer of antibiotic resistance from sources to the receptors are highlighted. The human exposure and health risks posed by air-borne resistome are presented. A health risk assessment and mitigation strategy is discussed. Finally, future research directions including key knowledge gaps are summarized.

Melting curve-based assay as an alternative technique for the accurate detection of SARS-CoV-2

Background:

Early and cost-effective diagnosis and monitoring of the infection caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are critically important to anticipate and control the disease. We aimed to set up a SYBR Green-based one-step real-time polymerase chain reaction (PCR) as a lower-cost alternative method to detect the virus.

Materials and Methods:

An in-house SYBR Green-based PCR assay targeting the envelope (E) and RNA-dependent RNA polymerase (RdRp) genes, was set up to diagnose the infection, and was compared with the reference probe-based PCR method.

Results:

When the commercial probe-based assay was considered as the reference method, SYBR Green-based PCR had a slightly lower sensitivity (81.98% and 86.25% for E and RdRp targets, respectively) and a good specificity (100% and 94.44% for E and RdRp targets, respectively). For both gene targets, three different melting temperature (Tm) patterns were found in the PCRs of the nasopharyngeal/oropharyngeal swab samples, but no size polymorphism was seen in agarose gel electrophoresis.

Conclusion:

Further studies to improvement of the assay are needed to make it an inexpensive and reliable tool for the diagnosis of COVID-19.

Isolation and molecular characterization of clinical and environmental dematiaceous fungi and relatives from Iran

Background and Purpose:

The frequency and genetic diversity of black fungi in environmental and clinical settings have not been fully studied in Iran. This study aimed to identify and evaluate intra- and inter-species DNA sequence variation and also understand the phylogenetic relationships of melanized fungi and relatives isolated from different geographical regions of Iran.

Materials and Methods:

In total, 111 clinical and environmental strains of dematiaceous fungi were isolated, and their internal transcribed spacer ribosomal DNA (rDNA) regions were sequenced and analyzed.

Results:

An inter-species nucleotide sequence diversity rate of 1 to 464 nucleotides was observed between the species. Intra-species differences were found in the strains of Alternaria alternata, Cladosporium cladosporioides, Alternaria tenuissima, Curvularia spicifera, Aureobasidium pullulans, Curvularia hawaiiensis, Neoscytalidium dimidiatum, Alternaria terricola, Alternaria chlamydospora, Didymella glomerata, and Drechslera dematioidea by 0–59, 0–22, 0–4, 0–4, 0–3, 0–2, 0–2, 0–2, 0–2, 0–1, and 0–1 nucleotide, respectively.

Conclusion:

The internal transcribed spacer rDNA is useful for the discrimination of several taxa of dematiaceous fungi. However, a better understanding of the taxonomy of species of Alternaria requires a larger rDNA region or a library of other gene sequences.

Antibiotic resistance and class 1 integron genes distribution in irrigation water-soil-crop continuum as a function of irrigation water sources

The increasing demand for fresh water coupled with the need to recycle water and nutrients has witnessed a global increase in wastewater irrigation. However, the development of antibiotic resistance hotspots in different environmental compartments, as a result of wastewater reuse is becoming a global health concern. The effect of irrigation water sources (wastewater, surface water, fresh water) on the presence and abundance of antibiotic resistance genes (ARGs) (bla_CTX-m-32, tet-W, sul1, cml-A, and erm-B) and class 1 integrons (intI1) were investigated in the irrigation water-soil-crop continuum using quantitative real-time PCR (qPCR). Sul1 and bla_CTX-m-32 were the most and least abundant ARGs in three environments, respectively. The abundance of ARGs and intI1 significantly decreased from wastewater to surface water and then fresh water. However, irrigation water sources had no significant effect on the abundance of ARGs and intI1 in soil and crop samples. Principal component analysis (PCA) showed that UV index and air temperature attenuate the abundance of ARGs and intI1 in crop samples whereas the air humidity and soil electrical conductivity (EC) promotes the ARGs and intI1. So that the climate condition of semi-arid regions significantly affects the abundance of ARGs and intI1 in crop samples. The results suggest that treated wastewater might be safely reused in agricultural practice in semi-arid regions without a significant increase of potential health risks associated with ARGs transfer to the food chain. However, further research is needed for understanding and managing ARGs transfer from the agricultural ecosystem to humans through the food chain.

Tracking antibiotic resistance genes and class 1 integrons in Escherichia coli isolates from wastewater and agricultural fields

Considering high concentrations of multidrug-resistant bacteria and antibiotic resistance genes (ARGs) in wastewater, agricultural reuse of treated wastewater may be a public health threat due to ARG dissemination in different environmental compartments, including soil and edible parts of crops. We investigated the presence of antibiotic-resistant Escherichia coli as an indicator bacterium from secondary treated wastewater (STWW), water- or wastewater-irrigated soil and crop samples. ARGs including bla_CTX-m-32, bla_OXA-23, tet-W, sul1, cml-A, erm-B, along with intI1 gene in E. coli isolates were detected via molecular methods. The most prevalent ARGs in 78 E. coli isolates were sul1 (42%), followed by bla_CTX-m-32 (19%), and erm-B (17%). IntI1 as a class 1 integrons gene was detected in 46% of the isolates. Cml-A was detected in STWW isolates but no E. coli isolate from wastewater-irrigated soil and crop samples contained this gene. The results also showed no detection of E. coli in water-irrigated soil and crop samples. Statistical analysis showed a correlation between sul1 and cml-A with intI1. The results suggest that agricultural reuse of wastewater may contribute to the transmission of antibiotic-resistant bacteria to soil and crop. Further research is needed to determine the potential risk of ARB associated with the consumption of wastewater-irrigated crops.

COVID-19 infection risk from exposure to aerosols of wastewater treatment plants

Fecal shedding of SARS-CoV-2 from COVID-19 patients and presence of the viral RNA in wastewater have extensively been reported. Some wastewater treatment plant (WWTP) processes generate aerosols which have the potential to transmit pathogenic microorganisms and present a health risk for exposed individuals. We analyzed the presence of viral RNA of SARS-CoV-2 in raw wastewater and air samples of WWTPs. The risk that may arise from exposure to virus-contaminated aerosols of wastewater was estimated by developing a quantitative microbial risk analysis (QMRA) method. SARS-CoV-2 was detected in 9 of 24 (37.5%) wastewater samples with a concentration about 10⁴ genomic copies L^-1. The viral RNA was also detected in 40% (6/15) of air samples. QMRA analysis showed a relatively high risk of SARS-CoV-2 infection for wastewater workers via exposure to the viral aerosols. The estimated annual infection risk ranged from 1.1 × 10^-2 to 2.3 × 10^-2 per person per year (PPPY) for wastewater workers which was higher than the reference level recommended by WHO (10^-3 pppy). However, due to the lack of data on survival of SARS-CoV-2 in wastewater and its fate in aerosolized state, more research is needed to determine the importance of wastewater in transmission of COVID-19.

Direct Detection and Identification of the Most Common Bacteria and Fungi Causing Otitis Externa by a Stepwise Multiplex PCR

Background

Considering the importance of differential diagnosis of infectious otitis externa (OE), a stepwise PCR-based assay using universal and genus- or species-specific primers for the detection/identification of the most prevalent bacterial and fungal OE was developed and evaluated on the ear aspiration specimens of clinically suspected patients.

Methods and Materials

A total of 120 ear aspiration specimens with otomycosis suspicion were subjected to manual DNA extraction using phenol–chloroform extraction after tissue digestion with a lysis buffer. The multiplex PCR was initially performed using pan-fungal and bacterial homemade primers. Pseudomonas and Staphylococcus specific primers were simultaneously used in one reaction mixture to identify the bacterial genera. Furthermore, for the identification of fungal agents, Candida species-specific multiplex primers targeting the most clinically important Candida species causing OE (i.e., C. albicans, C. parapsilosis, and C. auris), as well as Aspergillus related multiplex PCR identifying the most prevalent Aspergillus species were used in two separate reaction mixtures. All the results of multiplex PCR were interpreted based on the amplicon size.

Results

The overall multiplex PCR-based detection rate of bacterial (n = 88; 73.3%) and fungal (n = 97; 81%) OE was documented to be 100% along with and complete consistency with the results of direct examination and Giemsa staining. Double amplicon bands of bacterial and fungal pathogens were evidenced in 76 specimens (63.3%). Moreover, the positivity rate of pan-fungal PCR was higher than that of the culture result. Out of 88 pan-bacterial positive PCR specimens, 66 and 47 ones were positive for Staphylococcus and Pseudomonas, respectively. In addition, 30 samples exhibited mixed infection of both, and five specimens remained negative. Out of 97 pan-fungal positive PCR specimens, 67 and 51 ones contained Candida and Aspergillus species, respectively. It should be noted that dual amplicon bands of Candida and Aspergillus-related multiplex PCR were yielded in 30 specimens.

Conclusion

The stepwise multiplex PCR assay proved to be more sensitive, more rapid, as well as less cumbersome in detection and identification of fungal and bacterial OE, compared to culture.

Asymptomatic carriers of coronavirus disease 2019 among healthcare workers in Isfahan, Iran

Aim: This study aimed to investigate the prevalence of coronavirus disease 2019 (COVID-19) among healthcare workers (HCWs) in Isfahan, Iran. Materials & methods: HCWs in COVID-19 wards of three referral COVID-19 hospitals in Isfahan were screened and tested for COVID-19 infection. Results: In total, 102 HCWs were screened whose median age was 43 years old. Moreover, 21 (20.5%) of them had a history of suspected infection with SARS-CoV2, mostly (66.6%) without any symptoms while six (28.5%) of them suffered from relatively mild diseases and one (4.7%) was diagnosed with pulmonary embolism. Conclusion: It was found that HCWs were prone to be asymptomatic carriers while their computed tomography images were normal. Therefore, it is recommended that reverse-transcriptase real-time-PCR be essential for the diagnosis of infections.

PM2.5-associated bacteria in ambient air: Is PM2.5 exposure associated with the acquisition of community-acquired staphylococcal infections?

Particulate matter (PM), a major component of air pollution, is an important carrier medium of various chemical and microbial compounds. Air pollution due to PM could increase the level of bacteria and associated adverse health effects. Staphylococci as important opportunistic pathogens that cause hospital- and community-acquired infections may transmit through air. This study aimed to obtain knowledge about the concentration of airborne bacteria as well as staphylococci associated with particulate matter with a diameter of less than 2.5 micrometers (PM_2.5) in ambient air. The impact of meteorological factors including ultraviolet (UV) index, wind speed, temperature, and moisture on microbial concentrations was also investigated. Quartz filters were used to collect PM_2.5 and associated bacteria in ambient air of a semiarid area. Airborne bacteria were quantified by culture method and Staphylococcus species identified by molecular methods. The mean (SD) concentration of PM_2.5 and airborne bacteria was 64.83 (24.87) µg/m³ and 38 (36) colony forming unit (CFU)/m³, respectively. The results showed no significant correlation between the levels of PM_2.5 and concentrations of bacteria (p < 0.05). Staphylococcus species were detected in 8 of 37 (22%) samples in a concentration from 3 to 213 CFU/m³. S. epidermidis was detected with the highest frequency followed by S. gallinarum and S. hominis, but S. aureus and methicillin-resistant Staphylococcus aureus (MRSA) were not detected. No significant correlation between the concentrations of bacteria with meteorological parameters was observed (p < 0.05). Our finding showed that, although the study area is sometimes subject to air pollution from PM_2.5, the concentration of PM_2.5- associated bacteria is relatively low. According to the results, PM_2.5 may not be a source of community-associated staphylococcal infections.

Campylobacter risk for the consumers of wastewater-irrigated vegetables based on field experiments

Water scarcity is emerging as a major problem in water stressed regions such as Middle East countries which highlights the importance of agricultural reuse of wastewater as a valid alternative source. However, consumption of wastewater-irrigated crops has been implicated as a vehicle for transmission of bacterial infections such as campylobacteriosis. Understanding and minimizing public health threats associated with agricultural reuse of treated wastewater (TWW) are crucial elements in sustainable water resource management. To address this need, the present study was carried out to determine Campylobacter risk for the consumers of TWW-irrigated vegetables by field experiments as well as quantitative microbial risk assessment (QMRA) model. Campylobacter was monitored in secondary treated wastewater, TWW-irrigated soil and harvested vegetables by nested real-time PCR assay. Campylobacter was detected in 64% (16/25) of TWW samples, whereas analysis of TWW-irrigated soil and vegetable samples yielded no positive result for Campylobacter. The estimated mean annual Campylobacter disease burden ranged from 2.37 × 10^-5 to 6.6 × 10^-5 disability-adjusted life years (DALYs) per person per year (pppy) for vegetable consumers which was lower than the less stringent reference level of 10^-4 DALYs pppy has been recommended by world health organization (WHO). Our results in regard to the QMRA estimates and field experiments suggest that the reuse of TWW for irrigation of vegetables doesn't pose a considerable risk to human health from the viewpoint of Campylobacter infections in a semi-arid area.

Correction to: Improved degradation of n-hexane vapours using a hybrid system, a photoreactor packed with TiO2 coated-scoria granules and a multilayer biofilter

[This corrects the article DOI: 10.1007/s40201-019-00416-4.].

Improved degradation of n-hexane vapours using a hybrid system, a photoreactor packed with TiO2 coated-scoria granules and a multilayer biofilter

Biofiltration of hydrophobic and/or recalcitrant volatile organic compounds such as n-hexane is imperfect. In the present study, we applied a hybrid system consisting of a photoreactor packed with scoria granules coated with TiO₂ and a biofilter to improve the removal efficiency of n-hexane from the air stream. The experimental results showed that the hybrid system provided higher removal efficiencies than the single biofilter process with an inlet n-hexane concentration range of 0.11-1 g^-3 for empty bed residence times (EBRTs) of 30-120 s in the hybrid system. The removal efficiency of the single biofilter in EBRTs of 30, 60 and 120 s was 10.06%, 21.45%, and 45.98%, respectively. When the photoreactor was included as a pretreatment system (with residence time of 7-27 s) and the overall EBRTs of the system was adjusted to 30, 60 and 120 s, the removal efficiency of the hybrid system was increased to 39.79%, 63.08%, and 92.6%, respectively. The mass ratio of carbon dioxide produced as an indicator for n-hexane degradation in the hybrid system and the biofilter alone was 1.9 and 1.28, respectively. Bacterial community analysis with sequence analysis of 16S rDNA in the biofilter biomass revealed that Pseudomonas and Bacillus as predominant bacterial species were responsible for n-hexane biodegradation. Therefore, the application of the hybrid system is advantageous in enhanced n-hexane removal from the air stream.

Potential transmission sources of Helicobacter pylori infection: detection of H. pylori in various environmental samples

PURPOSE

Helicobacter pylori is one of the most common human infectious agents which may be transmitted via water. This study was designed to test H. pylori presence via molecular methods in various aquatic environments as well as sewage sludge (SS) to understand the role of these environments in the pathogen's transmission.

METHODS

specific primers for the 16S rRNA and ureA genes of H. pylori were used in a nested and semi-nested PCR, respectively. Detection sensitivity of H. pylori in environmental samples by semi-nested PCR was also compared with real-time PCR. Analysis of fecal coliforms (FC) as pollution indicator bacteria was also performed.

RESULTS

H. pylori 16S rRNA gene was detected in 36% (14/39) of wastewater samples and 8% (2/25) of water samples, while amplification of ureA gene yielded only two positive results. None of the SS samples were positive for H. pylori and real-time PCR could not identify H. pylori in any of the samples. The results showed no correlation between the presence of H. pylori and FC.

CONCLUSIONS

Our result revealed the widespread presence of H. pylori in wastewater samples which indicates wastewater may be a source for dissemination and transmission of H. pylori infection. Further research is needed to determine the risk of H. pylori in wastewater reuse for irrigation of crops.

Effects of irrigation with secondary treated wastewater on physicochemical and microbial properties of soil and produce safety in a semi-arid area

Water scarcity is becoming one of the largest problems worldwide. Agricultural reuse of wastewater has been considered a valuable and reliable alternative, alleviating the pressure on freshwater resources in arid and semi-arid regions such as the Middle East. Inadequate microbial quality of treated wastewater is a challenge for developing countries, which limits agricultural reuse of wastewater. This study assessed the impact of irrigation with secondary treated wastewater (STWW) on soil properties as well as the safety of various types of crops as compared with tap water (TW) irrigation through a furrow system. Total and fecal coliforms and Escherichia coli were monitored as indicator bacteria in STWW, irrigated soil and harvested crops. The presence of pathogenic E. coli O157, Salmonella and Shigella was also monitored in all samples using a combination of culture and molecular methods. The microbial quality of wastewater in terms of E. coli concentration (4.18 Log MPN/100 ml) failed to meet the world health organization (WHO) recommendation for irrigation of root and leafy crops (≤103 and ≤ 104E. coli per 100 ml for root and leafy crops, respectively). No significant effects on physicochemical properties of the soil irrigated with STWW was found in comparison with control plots, except for electrical conductivity (EC) and sodium adsorption ratio (SAR), which were slightly higher in STWW soil samples. Although the microbial quality of soil was affected by STWW irrigation, a relatively low concentration of E. coli was detected in soil. No microbial contamination in terms of E. coli was found on harvested maize and onion. E. coli contamination of lettuce and spring onion was found for both irrigation schemes. No STWW, soil or crop samples were found positive for pathogenic bacteria. According to the analyzed parameters, STWW could be safely used as an alternative source for irrigation of root and leafy crops.

Coupling of bioaugmentation and phytoremediation to improve PCBs removal from a transformer oil-contaminated soil

This study was carried out to assess the dissipation of 17 selected polychlorinated biphenyl (PCB_i) congeners in a transformer oil-contaminated soil using bioaugmentation with 2 PCB-degrading bacterial strains, i.e., Pseudomonas spp. S5 and Alcaligenes faecalis, assisted or not by the maize (Zea mays L.) plantation. After 5 and 10 weeks of treatment, the remaining concentrations of the target PCB_i congeners in the soil were extracted and measured using GC-MS. Results showed that the bacterial augmentation treatments with Pseudomonas spp. S5 and A. faecalis led to 21.4% and 20.4% reduction in the total concentration of the target PCBs (ΣPCB_i), respectively, compared to non-bioaugmented unplanted control soil. The ΣPCB_i decreased by 35.8% in the non-bioaugmented planted soil compared with the control. The greatest degradation of the PCB congeners was observed over a 10-week period in the soil inoculated with Pseudomonas spp. S5 and cultivated with maize. Under this treatment, the ΣPCB_i decreased from 357 to 119 ng g^-1 (66.7% lower) and from 1091 to 520 ng g^-1 (52.3% lower). Overall, the results suggested that the combined application of phytoremediation and bioaugmentation was an effective technique to remove PCBs and remediate transformer oil-contaminated soils.

Estimation of health risks caused by exposure to enteroviruses from agricultural application of wastewater effluents

Agricultural reuse of wastewater is a common practice worldwide, especially in arid and semiarid area due to the freshwater scarcity. Wastewater irrigation in the Middle East, one of the most water-stressed regions in the world, could be a key factor for socio-economic development, but the microbial contamination of untreated or partially treated wastewater is a serious public health concern. Potential transmission of enteric viral infections through wastewater reuse in agricultural activities represents a true health risk for exposed individuals. Accordingly, it is important to assess the health risks associated with wastewater reuse. A quantitative microbial risk assessment (QMRA) with Monte-Carlo simulation was used to estimate the annual risk of enterovirus (EV) infection and disease burden for farmers and consumers of wastewater-irrigated lettuce in Iran, a semiarid country in the Middle East region. Risk analysis was performed based on the measured concentrations of EV in effluent of two activated sludge wastewater treatment plants (WWTP). Wastewater effluent sampling was carried out over a nine-month period, and the presence of total and fecal coliforms and EV was determined. Fecal coliform bacteria were found at a high level exceeded the guideline limit for wastewater reuse in agriculture. EVs were detected in 40% of samples with the highest frequency in summer with a mean of 12 and 16 pfu/ml for WWTP-A and B, respectively. Statistical analysis showed no correlation between the concentration of fecal coliforms and EV. The estimated infection risk for EVs was 8.8 × 10-1 and 8.2 × 10-1 per person per year (pppy) for farmers of WWTP-A and -B, respectively which was about 2 log higher than the tolerable infection risk of 2 × 10-3 pppy. The estimated risk for lettuce consumers exhibited a lower level of infection and disease burden but higher than the guideline limits. The median disease burden for consumption of lettuce irrigated with activated sludge effluents was about 10-3 Disability Adjusted Life Years (DALY) pppy which exceeded the WHO guideline threshold of 10-4 DALY pppy. The results of study indicated that the activated sludge effluents require an additional reduction of EVs to achieve the acceptable level of risk for agricultural reuse of wastewater.

Detection of antibiotic resistant Acinetobacter baumannii in various hospital environments: potential sources for transmission of Acinetobacter infections

Background

Antibiotic resistant Acinetobacter baumannii has emerged as one of the most problematic hospital acquired pathogens around the world. This study was designed to investigate the presence of antibiotic resistant A. baumannii in various hospital environments.

Methods

Air, water and inanimate surface samples were taken in different wards of four hospitals and analyzed for the presence of A. baumannii. Confirmed A. baumannii isolates were analyzed for antimicrobial susceptibility and also screened for the presence of three most common OXA- type carbapenemase-encoding genes.

Results

A. baumannii was detected in 11% (7/64) of air samples with the highest recovery in intensive care units (ICUs). A. baumannii was also detected in 17% (7/42) and 2% (1/42) of surface and water samples, respectively. A total of 40 A. baumannii isolates were recovered and analysis of antimicrobial susceptibility showed the highest resistance towards ceftazidime (92.5%, 37/40). 85% (34/40) and 80% (32/40) of the isolates were also resistant to imipenem and gentamicin, respectively. Resistance genes analysis showed that 77.5% (31/40) strains contained OXA-23 and 5% (2/40) strains contained OXA-24, but OXA-58 was not detected in any of the strains.

Conclusion

Detection of antibiotic resistant A. baumannii in various samples revealed that hospital environments could act as a potential source for transmission of A. baumannii infections especially in ICUs. These results emphasize the importance of early detection and implementation of control measures to prevent the spread of A. baumannii in hospital environments.

Occurrence of airborne vancomycin- and gentamicin-resistant bacteria in various hospital wards in Isfahan, Iran

BACKGROUND

Airborne transmission of pathogenic resistant bacteria is well recognized as an important route for the acquisition of a wide range of nosocomial infections in hospitals. The aim of this study was to determine the prevalence of airborne vancomycin and gentamicin (VM and GM) resistant bacteria in different wards of four educational hospitals.

MATERIALS AND METHODS

A total of 64 air samples were collected from operating theater (OT), Intensive Care Unit (ICU), surgery ward, and internal medicine ward of four educational hospitals in Isfahan, Iran. Airborne culturable bacteria were collected using all glass impingers. Samples were analyzed for the detection of VM- and GM-resistant bacteria.

RESULTS

The average level of bacteria ranged from 99 to 1079 CFU/m(3). The highest level of airborne bacteria was observed in hospital 4 (628 CFU/m(3)) and the highest average concentration of GM- and VM-resistant airborne bacteria were found in hospital 3 (22 CFU/m(3)). The mean concentration of airborne bacteria was the lowest in OT wards and GM- and VM-resistant airborne bacteria were not detected in this ward of hospitals. The highest prevalence of antibiotic-resistant airborne bacteria was observed in ICU ward. There was a statistically significant difference for the prevalence of VM-resistant bacteria between hospital wards (P = 0.012).

CONCLUSION

Our finding showed that the relatively high prevalence of VM- and GM-resistant airborne bacteria in ICUs could be a great concern from the point of view of patients' health. These results confirm the necessity of application of effective control measures which significantly decrease the exposure of high-risk patients to potentially airborne nosocomial infections.

Hospital air: A potential route for transmission of infections caused by β-lactam-resistant bacteria

BACKGROUND

The emergence of bacterial resistance to β-lactam antibiotics seriously challenges the treatment of various nosocomial infections. This study was designed to investigate the presence of β-lactam-resistant bacteria (BLRB) in hospital air.

METHODS

A total of 64 air samples were collected in 4 hospital wards. Detection of airborne bacteria was carried out using culture plates with and without β-lactams. BLRB isolates were screened for the presence of 5 common β-lactamase-encoding genes. Sequence analysis of predominant BLRB was also performed.

RESULTS

The prevalence of BLRB ranged between 3% and 34%. Oxacillin-resistant bacteria had the highest prevalence, followed by ceftazidime- and cefazolin-resistant bacteria. The frequency of β-lactamase-encoding genes in isolated BLRB ranged between 0% and 47%, with the highest and lowest detection for OXA-23 and CTX-m-32, respectively. MecA had a relatively high frequency in surgery wards and operating theaters, whereas the frequency of blaTEM was higher in intensive care units and internal medicine wards. OXA-51 was detected in 4 wards. Acinetobacter spp, Acinetobacter baumannii, and Staphylococcus spp were the most predominant BLRB.

CONCLUSIONS

The results revealed that hospital air is a potential route of transmission of BLRB, such as Acinetobacter and Staphylococcus, 2 important causative agents of nosocomial infections. Therefore, improvement of control measures against the spreading of airborne bacteria in hospital environments is warranted.

Assessment of the Physicochemical Quality of Drinking Water Resources in the Central Part of Iran

The aim of the study described in this article was to assess the physicochemical quality of water resources in Isfahan province, located in the central part of Iran, from June to November 2012. Comparison of the results with the acceptable limits recommended by the World Health Organization (WHO) for drinking water showed that nitrate, chloride, iron, and fluoride concentrations exceeded the maximum acceptable level in 12.3%, 9.2%, 6.8%, and 1.5% of samples, respectively. Total dissolved solids (TDS) and turbidity values also exceeded the maximum acceptable level in 9.2% and 3.1% of samples, respectively. In general, the quality of drinking water resources in the central part of Iran at present is mostly acceptable and satisfactory. It may be deteriorated in the future, however, because water quantity and quality in arid and semiarid areas are highly variable over time. Therefore, continued monitoring of the water resources quality is extremely important to environmental safety.

Fluoride exposure and its health risk assessment in drinking water and staple food in the population of Dayyer, Iran, in 2013

AIMS

The aims of this study were to determine fluoride concentration in drinking water and staple foods consumed by residents of Dayyer port (Bushehr province, south of Iran) and to assess its health risk via human intake in 2013.

MATERIALS AND METHODS

Health risk assessment due to fluoride exposure via consumption of drinking water, date, vegetables and fish was conducted in spring and summer of 2013 using the US-EPA (United States-Environmental Protection Agency) method, which considers hazard quotient (HQ) as a ratio of the estimated dose of a contaminant to the reference dose. A fluoride ion-selective electrode (ISE) measured the fluoride contents of food samples. The sodium-2-(parasulfophenyl largo)-1,8-dihydroxy-3,6-naphtnalene disulfonate colorimetric method (SPADNS) was used to determine fluoride concentration in water samples.

RESULTS

The total estimated oral intake of fluoride for children in summer and spring were 120.6 and 145.6 µg/kg/day, respectively. These values for adults were 99.2 and 112 µg/kg/day. This survey demonstrated that drinking water was the most important contributor of dietary fluoride intake in the study area.

CONCLUSION

HQ values for adults and children were >1 which approves that a potential health risk of fluorosis can exist. The recommendations for the study area are supplying drinking water from alternative sources and defluoridation of drinking water by an adsorption technique and membrane filtration, respectively. Furthermore, people are suggested to have a good nutrition (especially rich of vitamin C) to reduce the risk of fluorosis.

Sewage sludge composting: quality assessment for agricultural application

In order to use sewage sludge (SS) composts in agriculture, it is extremely important to estimate the quality of compost products. The aim of this study was to investigate the quality of composted SS as a fertilizer and soil amendment especially in semi-arid areas. To determine the quality and agronomic value of the SS compost products, analyses on pH, electrical conductivity, organic matter content, C/N ratio, phytotoxicity, microbial load, and heavy metal content of composted anaerobically digested SS, with different proportions (1:1, 1:2, and 1:3 v/v) of green and dry plant waste, as bulking agents, were performed. The 1:2 and 1:3 mixtures of SS and green/dry plant waste were the most beneficial for composting, with final composts attaining high organic matter degradation and exhibiting low amounts of heavy metals, a relatively high germination index, and significant reduction of pathogens, suggesting the agricultural relevance of composted SS and green/dry plant waste at 1:2 and 1:3 (v/v) proportions. pH and electrical conductivity were also within the permissible limits. With respect to international standards, it appears that composted SS and green/dry plant waste at 1:2 and 1:3 proportions pose no threat to soil or plant quality if used in agriculture or land restoration.

Occurrence of Clostridium difficile in two types of wastewater treatment plants

Wastewater is a potential environmental source of Clostridium difficile, although a direct link with community-acquired C. difficile infection (CA-CDI) in humans has not yet been established. The present study was performed to determine the occurrence of C. difficile in two types of wastewater treatment plants (WWTPs) in Isfahan, Iran. A total of 95 samples were taken from a conventional activated sludge treatment plant and a waste stabilization ponds system, and analyzed for the presence of C. difficile. C. difficile was found in 13.6% (3/22) of digested sludge samples. However, no C. difficile was detected in inlet and outlet samples or in raw sludge of activated sludge. C. difficile was also detected in 5% (2/40) of the samples from waste stabilization ponds. Polymerase chain reaction (PCR) analysis showed that all strains of C. difficile detected were toxigenic (tcdB gene positive). This study shows that C. difficile was present in WWTPs, which might constitute a potential source of community-acquired C. difficile infection.

Respiration and enzymatic activities as indicators of stabilization of sewage sludge composting

The objective of this work was to study the evolution of physico-chemical and microbial parameters in the composting process of sewage sludge (SS) with pruning wastes (PW) in order to compare these parameters with respect to their applicability in the evaluation of organic matter (OM) stabilization. To evaluate the composting process and organic matter stability, different microbial activities were compared during composting of anaerobically digested SS with two volumetric ratios, 1:1 and 3:1 of PW:SS and two aeration techniques including aerated static piles (ASP) and turned windrows (TW). Dehydrogenase activity, fluorescein diacetate hydrolysis, and specific oxygen uptake rate (SOUR) were used as microbial activity indices. These indices were compared with traditional parameters, including temperature, pH, moisture content, organic matter, and C/N ratio. The results showed that the TW method and 3:1 (PW:SS) proportion was superior to the ASP method and 1:1 proportion, since the former accelerate the composting process by catalyzing the OM stabilization. Enzymatic activities and SOUR, which reflect microbial activity, correlated well with temperature fluctuations. Based on these results it appears that SOUR and the enzymatic activities are useful parameters to monitor the stabilization of SS compost.

Resazurin reduction assay, a useful tool for assessment of heavy metal toxicity in acidic conditions

Almost all bioassays have been designed only for pH levels around 7; however, some toxicant characteristics may be different at lower pH values. In this study, a modified resazurin reduction method was used to evaluate the toxicity of heavy metals and metal plating wastewater on acid-tolerant (AT) and conventional bacteria at the natural and acidic pH conditions. According to our optimized protocol, resazurin was rapidly reduced by both conventional and AT active microorganisms. Considering the 30-min median effective concentration (30 min EC₅₀) values, conventional bacteria were comparatively more resistant than the acid-tolerant bacteria (ATB) in the case of exposure to Cd, Pb, Cr, and Zn, but the reverse case was found for Hg. After an exposure of 30 min, Cr and Hg showed the highest toxicity to ATB (30 min EC₅₀ values were 0.34 and 17.02 μmol/L, respectively), while Zn and Pb had a considerably lower toxicity. The modified resazurin reduction method successfully assessed the impact of metal plating wastewaters on the activities of conventional and AT bacteria. According to the findings where the wastewaters contain heavy metals, wastewater treatment facilities, which are dependent on ATB activity, should use bioassays at acidic pH values for better understanding of the effects of toxicants.

Acute toxicity of Hg, Cd, and Pb towards dominant bacterial strains of sequencing batch reactor (SBR)

One of the most important factors that affect the operation efficiency of sequencing batch reactor (SBR) technology is bacterial viability and biomass activity. The acute toxicity of three heavy metals to four dominant strains of sequencing batch reactor (Pseudomonas, Aeromonas, Enterobacter, and Bacillus) was investigated using a resazurin bioassay. After exposing the bacterial strains to soluble compound of Hg, Cd, and Pb, at more than five selected concentrations, the median effective concentration (EC50) and the mortality rate values were calculated. Large differences were observed in sensitivities of the four bacterial strains to the metals. Pseudomonas showed the highest sensitivity for Cd (EC₅₀ = 0.06 μmol/L) and Hg (EC₅₀ = 11.75 μmol/L), while Aeromonas showed the highest sensitivity for Pb (EC₅₀ = 48.27 μmol/L). Considering the EC50 test results, it was concluded that Pseudomonas and Aeromonas are excellent and reliable bioindicators for assessing the toxicity of water and wastewaters polluted by Cd, Hg, and Pb. The rapidity (30 min) and simplicity of the resazurin bioassay procedure enable this enzymatic test to be used in toxicity assessment of small and decentralized wastewater treatment plants (WWTPs).

Detection of Legionella spp. by a nested-PCR assay in air samples of a wastewater treatment plant and downwind distances in Isfahan

Background:

Wastewater contains a variety of pathogens and bio -aerosols generated during the wastewater treatment process, which could be a potential health risk for exposed individuals. This study was carried out to detect Legionella spp. in the bio -aerosols generated from different processes of a wastewater treatment plant (WWTP) in Isfahan, Iran, and the downwind distances.

Materials and Methods:

A total of 54 air samples were collected and analyzed for the presence of Legionella spp. by a nested- polymerase chain reaction (PCR) assay. A liquid impingement biosampler was used to capture bio -aerosols. The weather conditions were also recorded.

Results:

Legionella were detected in 6% of the samples, including air samples above the aeration tank (1/9), belt filter press (1/9), and 250 m downwind (1/9).

Conclusion:

The result of this study revealed the presence of Legionella spp. in air samples of a WWTP and downwind distance, which consequently represent a potential health risk to the exposed individuals.

Monitoring of airborne bacteria and aerosols in different wards of hospitals - Particle counting usefulness in investigation of airborne bacteria

INTRODUCTION AND OBJECTIVE

The presence of airborne bacteria in hospital environments is of great concern because of their potential role as a source of hospital-acquired infections (HAI). The aim of this study was the determination and comparison of the concentration of airborne bacteria in different wards of four educational hospitals, and evaluation of whether particle counting could be predictive of airborne bacterial concentration in different wards of a hospital.

MATERIALS AND METHOD

The study was performed in an operating theatre (OT), intensive care unit (ICU), surgery ward (SW) and internal medicine (IM) ward of four educational hospitals in Isfahan, Iran. A total of 80 samples were analyzed for the presence of airborne bacteria and particle levels.

RESULTS

The average level of bacteria ranged from 75-1194 CFU/m (3) . Mean particle levels were higher than class 100,000 cleanrooms in all wards. A significant correlation was observed between the numbers of 1-5 µm particles and levels of airborne bacteria in operating theatres and ICUs. The results showed that factors which may influence the airborne bacterial level in hospital environments should be properly managed to minimize the risk of HAIs especially in operating theaters.

CONCLUSIONS

Microbial air contamination of hospital settings should be performed by the monitoring of airborne bacteria, but particle counting could be considered as a good operative method for the continuous monitoring of air quality in operating theaters and ICUs where higher risks of infection are suspected.

Applicability of universal Bacteroidales genetic marker for microbial monitoring of drinking water sources in comparison to conventional indicators

Water quality monitoring is essential for the provision of safe drinking water. In this study, we compared a selection of fecal indicators with universal Bacteroidales genetic marker to identify fecal pollution of a variety of drinking water sources. A total of 60 samples were collected from water sources. The microbiological parameters included total coliforms, fecal coliforms, Escherichia coli and fecal streptococci as the fecal indicator bacteria (FIB), Clostridium perfringens and H2S bacteria as alternative indicators, universal Bacteroidales genetic marker as a promising alternative fecal indicator, and Salmonella spp., Shigella spp., and E. coli O157 as pathogenic bacteria. From 60 samples analyzed, Bacteroidales was the most frequently detected indicator followed by total coliforms. However, the Bacteroidales assay failed to detect the marker in nine samples positive for FIB and other alternative indicators. The results of our study showed that the absence of Bacteroidales is not necessarily an evidence of fecal and pathogenic bacteria absence and may be unable to ensure the safety of the water. Further research, however, is required for a better understanding of the use of a Bacteroidales genetic marker as an indicator in water quality monitoring programs.

Surveillance of Legionella species in hospital water systems: the significance of detection method for environmental surveillance data

Monitoring of hospital water systems to prevent and control nosocomial legionellosis is important from a public health perspective. This study was conducted to survey the prevalence of Legionella contamination of hospital waters. A total of 44 water samples from the hot-water system of 11 hospitals were tested for Legionella by a culture method and a nested polymerase chain reaction (PCR) assay with Legionella-specific primers to identify the more sensitive method. Some physicochemical parameters and heterotrophic plate counts of water samples for possible association with Legionella contamination were also determined. The contamination rate of hospitals in our study varied between 64% (eight of 11)-100% based on culture method and nested PCR, respectively. Of the 44 water samples examined, 23% were positive for Legionella spp. by the culture method, while the nested PCR assay using the primers LEG448-JRP revealed 66% of the water samples being positive. Given the importance of monitoring hospital water systems for the presence of Legionella spp., the present PCR assay proved highly applicable for practical and sensitive surveillance of Legionella in such water systems. In addition, rapid monitoring of Legionella contamination could eliminate the potential exposure of high-risk patients through effective control measures.

Rapid monitoring of Pseudomonas aeruginosa in hospital water systems: a key priority in prevention of nosocomial infection

Pseudomonas aeruginosa has emerged as a major pathogen in nosocomial infections. Biofilm formation allows the microorganism to persist in hospital water systems for extended periods, which have been associated with nosocomial infections. The aim of this study was to evaluate the frequency of P. aeruginosa colonization of hospital tap waters by nested PCR assay. A total of 44 water samples were collected from 11 hospitals and analyzed for the presence of Pseudomonas spp. and P. aeruginosa by specific primer sets of 16S rRNA gene. Some physicochemical parameters and heterotrophic plate count (HPC) of samples for possible association with P. aeruginosa contamination were also determined. The nested PCR revealed 32% of the water samples being positive for P. aeruginosa. From the 11 hospitals surveyed, 82% (9 of 11) of the hospitals water systems were positive for P. aeruginosa. No correlation was seen between the presence of P. aeruginosa and HPC as well as physicochemical parameters. Identification of contaminated sources could be a key priority in waterborne nosocomial infections. PCR assay was used in the study provides simple, rapid, and reliable identification of P. aeruginosa in hospital water systems, which could eliminate the infections of P. aeruginosa through implementation of immediate control measures.

Application of cigarette filter rods as biofilm carrier in an integrated fixed-film activated sludge reactor

Bio-carriers are an important component of integrated fixed-film activated sludge (IFAS) processes. In this study, the capability of cigarette filter rods (CFRs) as a bio-carrier in IFAS processes was evaluated. Two similar laboratory-scale IFAS systems were operated over a 4-month period using Kaldnes-K3 and CFRs as IFAS media. The process performance was studied by using chemical oxygen demand (COD). The organic loading rate was in the range 0.5-2.8 kgCOD/(m(3)·d). The COD average removal efficiencies were 89.3 and 93.9% for Kaldnes-K3 (reactor A) and cigarette filters (reactor B), respectively. The results demonstrate that the performance of the IFAS reactor containing CFRs was comparable to the reactor using Kaldnes. The CFRs, which have a high porous surface area and entrapment ability for microbial cells, could be successfully used in biofilm reactors as a bio-carrier.

Ultraviolet irradiation: An effective inactivation method of Aspergillus spp. in water for the control of waterborne nosocomial aspergillosis

Invasive aspergillosis is the second most common cause of nosocomial fungal infections and occurring mainly by Aspergillus fumigatus, Aspergillus flavus, and Aspergillus niger. There is evidence that nosocomial aspergillosis may be waterborne. This study was conducted to evaluate the ultraviolet (UV) irradiation efficiency in terms of inactivating the most important Aspergillus species in water since these are potential sources for nosocomial aspergillosis. A continuous flow UV reactor which could be used as a point-of-use (POU) system was used to survey Aspergillus inactivation by UV irradiation. The inactivation efficiency of UV fluence (4.15-25 mJ/cm(2)) was measured by determination of fungal density in water before and after radiation. Because turbidity and iron concentration are two major water quality factors impacting UV disinfection effectiveness, the potential influence of these factors on UV inactivation of Aspergillus spp. was also measured. The 4 log inactivation for A. fumigatus, A. niger and A. flavus at a density of 1000 cfu/ml was achieved at UV fluences of 12.45 mJ/cm(2), 16.6 mJ/cm(2) and 20.75 mJ/cm(2), respectively. The inactivation efficiency for lower density (100 cfu/ml) was the same as for the higher density except for A. flavus. The removal efficiency of Aspergillus spp. was decreased by increasing the turbidity and iron concentration. UV disinfection could effectively inactivate Aspergillus spores from water and eliminate potential exposure of high-risk patients to fungal aerosols by installation of POU UV systems.

Performance evaluation of cigarette filter rods as a biofilm carrier in an anaerobic moving bed biofilm reactor

Biocarriers are an important component of anaerobic moving bed biofilm reactors (AMBBRs). In this study, the capability of cigarette filter rods (CFRs) as a biocarrier in an anaerobic moving bed biofilm reactor was evaluated. Two similar lab-scale anaerobic moving bed biofilm reactors were undertaken using Kaldnes-K3 plastic media and cigarette filter rods (wasted filters from tobacco factories) as biofilm attachment media for wastewater treatment. Organic substance and total posphours (TP) removal was investigated over 100 days. Synthetic wastewater was prepared with ordinary water and glucose as the main sources of carbon and energy, plus balanced macro- and micro-nutrients. Process performance was studied by increasing the organic loading rate (OLR) in the range of 1.6-4.5 kg COD/m3 x d. The COD average removal efficiency were 61.3% and 64.5% for AMBBR with cigarette filter rods (Reactor A) and AMBBR with Kaldnes plastic media (Reactor B), respectively. The results demonstrate that the performance of the AMBBR containing 0.25 litres of cigarette filters was comparable with a similar reactor containing 1.5 litres of Kaldnes plastic media. An average phosphorus removal of 67.7% and 72.9% was achieved by Reactors A and B, respectively.