Abundance of sewage-pollution indicator and human pathogenic bacteria in a tropical estuarine complex

The escalating threat of human-associated infectious bacteria in surface aquatic resources: Insights into prevalence, antibiotic resistance, survival mechanisms, detection, and prevention strategies

Anthropogenic activities and climate change profoundly impact water quality, leading to a concerning increase in the prevalence and abundance of bacterial pathogens across diverse aquatic environments. This rise has resulted in a growing challenge concerning the safety of water sources, particularly surface waters and marine environments. This comprehensive review delves into the multifaceted challenges presented by bacterial pathogens, emphasizing threads to human health within ground and surface waters, including marine ecosystems. The exploration encompasses the intricate survival mechanisms employed by bacterial pathogens and the proliferation of antimicrobial resistance, largely driven by human-generated antibiotic contamination in aquatic systems. The review further addresses prevalent pathogenic bacteria, elucidating associated risk factors, exploring their eco-physiology, and discussing the production of potent toxins. The spectrum of detection techniques, ranging from conventional to cutting-edge molecular approaches, is thoroughly examined to underscore their significance in identifying and understanding waterborne bacterial pathogens. A critical aspect highlighted in this review is the imperative for real-time monitoring of biomarkers associated with waterborne bacterial pathogens. This monitoring serves as an early warning system, facilitating the swift implementation of action plans to preserve and protect global water resources. In conclusion, this comprehensive review provides fresh insights and perspectives, emphasizing the paramount importance of preserving the quality of aquatic resources to safeguard human health on a global scale.

Preliminary assessment of the water quality of Rushikulya estuary based on the abundance of pathogenic bacteria

Estuaries are among the most dynamic ecosystems in coastal regions and are facing serious threats due to increasing anthropogenic activities. The aim of the present study is to evaluate the water quality of the Rushikulya estuary by analyzing the abundance of pathogenic bacteria in both its water and sediment. Water and sediment samples were collected from five different stations at the mouth of the Rushikulya estuary during the monsoon and post-monsoon seasons. These samples were analyzed to assess the abundance of pathogenic bacteria and environmental parameters. The results revealed that bacterial abundance is significantly higher in the sediment than in the water, possibly due to a longer residence time of pathogenic bacteria in the sediment. Seasonal observations indicated an increase in pathogenic bacterial abundance during the monsoon season, suggesting an impact from monsoonal discharge. Escherichia coli-like organism, faecal coliforms, Shigella-like organisms, and Vibrio cholera-like organisms were the dominant pathogenic bacteria in both the water and sediment of the Rushikulya estuary. The higher abundance of these pathogens and the results of statistical analysis, which showed a strong correlation between Total Streptococci and BOD (r = 0.79), indicate the influence of human settlement and the mixing of untreated sewage in the Rushikulya estuary. The elevated levels of E. coli, faecal coliforms, and Shigella-like organisms in the Rushikulya estuary raise significant concerns that require immediate attention.

Food wastes as a potential hotspot of antibiotic resistance: synergistic expression of multidrug resistance and ESBL genes confer antibiotic resistance to microbial communities

This study investigated antibiotic resistance (ABR) and extended-spectrum ß-lactamases (ESBL) patterns in bacterial isolates collected from the dairy, hotel, meat, and canteen food waste samples. A total of 144 bacterial strains were collected and screened for resistance against 9 standard antibiotics belonging to three generations and ESBL production. The ABR profile of the bacterial isolates was observed against all four major antibiotic groups (aminoglycosides, β-lactams, quinolone, and others), where resistance against cefotaxime (> 70%) and methicillin (> 50%) was high. Though the ABR pattern of strains from dairy waste (> 50%) was high against first-generation antibiotics, the strains from meat waste (> 50%) showed considerable resistance against second- and third-generation antibiotics. ESBL-producing isolates were screened (> 60%, n = 144) through primary identification tests (combined disk test and double disk synergy tests) and further confirmed through Hexa G-minus 23 and 24 and MIC E-stripe following CLSI guidelines. Genes conferring ESBL resistance bla_CTX-M, bla_SHV, bla_OXA, bla_TEM, bla_KPC genes and multidrug resistance (MDR) mexF gene were detected in the selected isolates with ABR and ESBL traits. Isolates with multidrug ABR and ESBL phenotype were further genotypically identified through 16 s rRNA gene sequencing. The synergy of ABR was detected through the co-expression of ESBL and MDR in isolates with a high occurrence of ABR and ESBL. The results demonstrate the significance of food waste as a natural reservoir of ABR and ESBL-producing pathogens, highlighting the importance of resistance monitoring and its interventions.

Anthropogenic impact and antibiotic resistance among the indicator and pathogenic bacteria from several industrial and sewage discharge points along the coast from Pydibhimavaram to Tuni, East Coast of India

Increasing urbanisation and industrialisation of the Visakhapatnam region have brought domestic sewage and industrial wastewater discharge into the coastal ocean. This study examines the indicator and pathogenic bacteria's quantitative abundance and antibiotic susceptibility. This study collected surface and subsurface water samples from ten different regions (147 stations; 294 samples), including 12 industrial discharge points, surrounding stations and two harbours from the coast of Pydibheemavaram to Tuni. Physicochemical parameters like salinity, temperature, fluorescence, pH, total suspended matter, nutrients, chlorophyll-a and dissolved oxygen showed a difference between regions. We noticed the presence of indicator (Escherichia coli and Enterococcus faecalis) and pathogenic (Aeromonas hydrophila, Klebsiella pneumoniae, Proteus mirabilis, Pseudomonas aeruginosa, Salmonella and Shigella, Vibrio cholera and Vibrio parahaemolyticus) bacteria among the samples. Waters from the near harbour and Visakhapatnam steel plant showed lower bacterial load with no direct input from industries to the coastal water. Samples collected during the industrial discharge period had a higher bacterial load, including E. coli. Enteric bacteria were found in higher numbers at most stations. Some isolates were resistant to multiple antibiotics with higher antibiotic resistance and multiple antibiotic resistance indexes compared with the other coastal water habitats in the Bay of Bengal. The occurrence of these bacteria above the standard limits and with multiple antibiotic resistance in the study region may pose a potential threat to the local inhabitants. It can create an alarming situation in the coastal waters in the study region.

Assessment on impact of sewage in coastal pollution and distribution of fecal pathogenic bacteria with reference to antibiotic resistance in the coastal area of Cape Comorin, India

Sewage is one of the biggest contributors to coastal pollution. The study was aimed to assess the impact of sewage on coastal water quality of Kanyakumari, the southernmost part of India. A bacteriological survey was made on distribution and abundance of fecal indicators and human pathogenic bacteria and seasonal influence on the bacterial load and antibiotic resistance of the isolates. Samples were collected from sewage discharge point along the eastern shore of Kanyakumari Coast from February 2019 to January 2020. Nine pollution indicator bacteria and pathogenic species such as Escherichia coli, Klebsiella spp., Enterococcus faecalis, Aeromonas spp., Proteus mirabilis, Salmonella typhi, Vibrio cholerae, Shigella spp. and Flavobacterium spp. were isolated from the samples. These isolates were tested against 10 antibiotics, using Kirby Bauer method. All the isolates were resistant to at least two antibiotics. The presence of antibiotic resistant bacteria has been used as bio-indicators of pollution. Hence it is clear that the domestic sewage entering the coast is untreated which might lead a serious impact on human and marine wildlife along coastlines.

Seasonal variations in the water quality and antibiotic resistance of microbial pollution indicators in the Mandovi and Zuari estuaries, Goa, India

The two adjacent estuaries of the rivers Mandovi and Zuari, along the Goa coast in the central west coast of India, are a large complex aquatic system hosting diverse natural habitats. The water quality in these habitats is affected by various anthropogenic activities as they are extensively used for transportation, fisheries and various recreational activities. In the present study, changes in the water quality and levels of microbial pollution during the pre-monsoon, monsoon and post-monsoon seasons were determined. The water quality index was estimated based on the parameters: temperature, salinity, pH, dissolved oxygen, biochemical oxygen demand and nutrients. The seasonal changes in the microbial pollution load were also assessed based on the abundance of pollution indicator organisms and their resistivity towards multiple antibiotics. Results show that the water quality index status was 'poor' in the pre-monsoon and post-monsoon seasons and it was 'good' only in the monsoon period. Levels of pollution indicator organisms determined show that the counts were the highest in the pre-monsoon season, which reduced in the monsoon and further declined during the post-monsoon season. However, the estimated multiple antibiotic resistance (MAR) index suggests that bacterial isolates in monsoonal water and sediment samples have maximum resistance towards antibiotics. This shows that, though the basic water quality improved during the monsoon, possibly due to substantial dilution, the increased terrestrial inputs brought harmful pathogens into these estuarine waters, which may be of potential health risk. Understanding the ecological status of the estuarine habitats is important for successful environmental management and sustainable development.

Indian coastal waters: a concoction of sewage indicator bacteria! An assessment on recreational beaches

Coastal water quality assessment is important to maintain a healthy environment for various uses including fisheries and recreation. Microbial populations are used as biological indicators of contamination to monitor water quality and are considered by the government to be one of the critical features for issuing safety guidelines. Different bacterial groups (pathogenic, vibrio and faecal) from five major recreational beaches of Chennai, India, were monitored for the assessment of coastal water quality. Faecal coliforms (FC) were high at all the beaches, with up to 4.2 × 10⁵ CFU/mL and exceeding the normal standard limits of 100 CFU/100 mL set by the Central Pollution Control Board (CPCB) of India. Rainfall was found to have a role in the variability and distribution of indicator and pathogenic bacteria. The seasonal dry period witnessed elevated FC, while dilution in the wet period reduced Escherichia coli-like organisms (ECLO). High microbial counts were detected near the beach situated close to the river mouth, mainly due to discharges of untreated domestic sewage and industrial wastes. Similarly, the biological oxygen demand (BOD) was also high, 0.32 to 10.32 mg/L. Dissolved inorganic nitrogen (DIN) ranged from 2.21 to 134.53 μmol/L and inorganic phosphate (IP) ranged from 0 to 57.53 μmol/L. These values indicated the presence of significant untreated sewage in the coastal water. This study revealed that Chennai coastal waters carry high levels of faecal and pathogenic bacteria, detrimental for recreational and other contact activities. The quantitative and qualitative analyses will be useful for modelling and prediction of coastal water quality and management of other recreational beaches in India.

Effect of Tidal Cycle on Escherichia coli Variability in a Tropical Estuary

A faecal indicator bacteria, Escherichia coli (E. coli), is widely used in monitoring health of estuaries, where tidal amplitude plays a critical role in its variability. Mahanadi estuary, formed at the mouth of a major tropical river Mahanadi, has large socio-economic importance. This anthropogenically stressed estuary remains understudied with respect to E. coli. Hence, this study addressed E. coli variability in Mahanadi estuary with novel sampling strategy that can be implemented at other tropical estuaries. The sampling strategy includes simultaneous measurements, at lesser-saline upper-estuary and higher-saline lower-estuary, over a tidal cycle. Although no significant variability of E. coli was observed between upper and lower-estuary, overall average count was higher during low tide and lower during high tide attributed to salinity fluctuations. Intermittent surpass of E. coli counts above recommended limits in Mahanadi estuary, indicated potential health risk, thus demands for frequent water quality monitoring and management strategies.

Microbial contamination and its associations with major ions in shallow groundwater along coastal Tamil Nadu

Microbes in groundwater play a key role in determining the drinking water quality of the water. The study aims to interpret the sources of microbes in groundwater and its relationship to geochemistry. The study was carried out by collecting groundwater samples and analyzed to obtain various cations and anions, where HCO₃^-, Cl^- and NO₃^- found to be higher than permissible limits in few samples. Microbial analysis, like total coliform (TC), total viable counts (TVC), fecal coliforms (FC), Vibrio cholera (V. cholerae) and total Streptococci (T. streptococci) were analyzed, and the observations reveal that most of the samples were found to be above the permissible limits adopted by EU, BIS, WHO and USEPA standards. Correlation analysis shows good correlation between Mg²⁺-HCO₃^-, K⁺-NO₃^-, TVC- V. cholerae and T. streptococci-FC. Major ions like Mg⁺, K⁺, NO₃, Ca²⁺ and PO₄ along with TS and FC were identified to control the geochemical and microbial activities in the region. The magnesium hardness in the groundwater is inferred to influence the TVC and V. cholerae. The mixing of effluents from different sources reflected the association of Cl with TC. Population of microbes T. streptococci and FC was mainly associated with Ca and Cl content in groundwater, depicting the role of electron acceptors and donors. The sources of the microbial population were observed with respect to the land use pattern and the spatial distribution of hydrogeochemical factors in the region. The study inferred that highest microbial activity in the observed in the residential areas, cultivated regions and around the landfill sites due to the leaching of sewage water and fertilizers runoff into groundwater. The concentrations of ions and microbes were found to be above the permissible limits of drinking water quality standards. This may lead to the deterioration in the health of particular coastal region.

Influence of anthropogenic activities on the spatial distribution of heterotrophic, indicator and pathogenic bacteria around Andaman and Nicobar Islands

To examine the influence of anthropogenic activities on the marine ecosystem around the Andaman and Nicobar Islands, a study was conducted to investigate the abundance of heterotrophic, indicator and pathogenic bacteria during the monsoon season. We noticed the higher abundance of heterotrophic, indicator (Escherichia coli and Enterococcus faecalis) and pathogenic bacterial counts (Aeromonas hydrophila, Enterobacter aerogens, Escherichia coli strain O157:H7, Shigella dysenteriae and Vibrio parahaemolyticus) near the 10^o channel, which is the principal route to reach Andaman mainland. Most of the stations are offshore (chosen to cover shipping tracks) at a distance ranging from 41 to 266 km from the coast. The nearest station to the coast was at 21 km away. Apart from those mentioned above, several other pathogenic bacteria were also detected such as Klebsiella pneumoniae, Salmonella paratyphi, Vibrio cholera and Vibrio vulnificus but they are sparsely detected at few stations only.

Prevalence of indicator and potential pathogenic bacterial groups in the Chapora bay-estuarine system, Goa, central west coast of India

This paper describes the prevalence of indicator and pathogenic bacterial groups in water and sediments in OSZ-offshore, ISZ-inshore, IEZ-inner estuary, and UEZ-upper estuary along the river Chapora, central west coast of India, which is influenced by anthropogenic inputs. The abundance of indicator bacterial groups such as total coliforms and Escherichia coli-like organisms in water ranged from non-detectable (ND) to 10³ colony-forming units (CFU)/mL. In contrast, their abundance in the sediments was six orders magnitude higher than water (ND to 10⁹ CFU/g). The abundance of potential pathogenic bacteria in water and sediment samples ranged from ND to 10³ CFU/mL and from ND to 10⁹ CFU/g respectively, with Shigella-like organisms (SHLO) being the most abundant. In the surface waters, SHLO and Pseudomonas aeruginosa-like organisms (PALO) and in bottom waters, Vibrio parahaemolyticus-like organism and PALO increased progressively from OSZ to UEZ. In contrast, Proteus/Klebsiella-like organisms (PKLO) showed a reverse trend. Amongst all four zones, IEZ was the most contaminated in terms of the higher abundance of indicator and potential pathogenic bacterial populations as corroborated by significantly lower water quality index value. Principal component analysis performed using physico-chemical variables and bacterial groups to reduce data set variability revealed that a different set of parameters contributed differently to the total variation in each zone. Considering the eco-sensitivity of the river Chapora, the results of the present study call for precautionary measures to minimize the degree of anthropogenic inputs.

Persistence of fecal indicator bacteria associated with zooplankton in a tropical estuary-west coast of India

In a study carried out during 2014, bacteria associated with zooplankton in the Zuari estuary were three to four orders of magnitude higher in abundance than in seawater. The live zooplankton carried much more bacterial load compared with the carcasses, and the fecal pellets harbored the highest density of bacteria, i.e., 8 × 10¹³ CFU cm^-3. The diversity of bacteria was higher in live zooplankton and also in seawater. But the activity of the zooplankton-associated bacteria was much higher compared with the free-living ones. Most of the associated bacteria belonged to the genus Enterobacter, Pseudomonas, Aeromonas, and Bacillus. In growth experiments, Aeromonas and Bacillus were found to have lower salinity optima than Enterobacter (20 psu) and Vibrio and Pseudomonas (normal seawater salinity). Better growth of bacteria was observed in the medium containing the diatom Chaetoceros sp. than Navicula sp. Bacterial isolates were also able to survive in oligotrophic conditions and produce optimum biomass in 2 days at salinity 5 psu, but in freshwater, the bacteria took a week's time to attain the optima. At salinities 0-35, the bacteria survived even for 3 months without nutrient addition, indicating resilience in these bacteria and mechanisms to persist in the estuaries even in adverse conditions.

Mesozooplankton characterization surrounding anthropogenic sewage inputs in the southeastern eutrophic Brazilian estuary of Guanabara Bay

Zooplankton assembly was characterized during the spring tide near a submarine outfall that discharges raw sewage directly into the southeastern portion of Guanabara Bay, near the Niterói, a highly urbanized center. The rain period directly influences water surface temperature and salinity, as has been previously observed in this bay. Dissolved oxygen (DO) and biochemical oxygen demand (BOD) were within the concentrations stipulated by the Brazilian legislation. The low chlorophyll a values observed herein may be associated with a nutritional imbalance to which phytoplankton may be subjected, observed through the carotenoid/chlorophyll ratio, which probably reflects zooplankton community composition. Twenty major zooplanktonic taxonomic groups were recorded, with a predominance of holoplanktonic taxa, mainly copepods. Mean zooplankton density and composition were in agreement with other studies in the region, however, these community characteristics at each of the sampling stations appear to be related to the urbanization degrees of each Niterói neighborhood.

Waterborne Diseases Arising From Climate Change

As a result of increased frequency and intensity of heat waves, increased floods and droughts, change in climate will affect biological, physical, and chemical components of water through different paths thus enhancing the risk of waterborne diseases. Identifying the role of weather in waterborne infection is a priority public health research issue as climate change is predicted to increase the frequency of extreme precipitation and temperature events. This chapter provides evidence that precipitation and temperature can affect directly or indirectly water quality and consequently affect the health human. This chapter also highlights the complex relationship between precipitation or temperature and transmission of waterborne disease such as diarrheal disease, gastroenteritis, cryptosporidiosis, giardiasis, and cholera.

Perennial occurrence of heterotrophic, indicator and pathogenic bacteria in the coastal Bay of Bengal (off Visakhapatnam) - Impact of physical and atmospheric processes

In order to examine the health of the coastal waters off Visakhapatnam in terms of prevalence and abundance of heterotrophic (H), indicator and pathogenic (P) bacterial counts (BC) and influence of physical processes on them, time-series observations were conducted during January (winter), March (spring), July (summer) and October (post-monsoon). We noticed the impact of physical forces on substantial variations in abundance and distribution of the HBC, total coliforms, Enterococcus faecalis and Pseudomonas aeruginosa in the study region. Based on our results Escherichia coli and other PBC were not much influenced by the physical conditions. It has been noticed that the perennial existence of the high abundance of IBC and PBC above the standard limits during the entire study period leading to an alarming situation in the coastal waters off Visakhapatnam.

Diversity of culturable yeasts associated with zoanthids from Brazilian reef and its relation with anthropogenic disturbance

Some of the main threats to coral reefs come from human actions on marine environment, such as tourism, overfishing and pollution from urban development. While several studies have demonstrated an association between bacteria and corals, demonstrating how these communities react to different anthropogenic stressors, yeast communities associated with corals have received far less attention from researchers. The aim of this work was therefore to describe cultivable yeasts associated with three coral species and to evaluate the influence of sewage discharge on yeasts community. We obtained 130 isolates, mostly belonging to phylum Ascomycota and many of them had previously been isolated from human samples or are considered pathogens. The mycobiota was more similar among corals collected from the same reef, indicating that the composition of reef yeast community is more influenced by environmental conditions than host species. We suggest further studies to elucidate which factors are most influential on the composition of the coral-associated yeast community.

Elucidation of the tidal influence on bacterial populations in a monsoon influenced estuary through simultaneous observations

The influence of tides on bacterial populations in a monsoon influenced tropical estuary was assessed through fine resolution sampling (1 to 3 h) during spring and neap tides from mouth to the freshwater end at four stations during pre-monsoon, monsoon and post-monsoon seasons. Higher abundance of total bacterial count (TBC) in surface water near the river mouth, compared to the upstream, during pre-monsoon was followed by an opposite scenario during the monsoon When seasonally compared, it was during the post-monsoon season when TBC in surface water was highest, with simultaneous decrease in their count in the river sediment. The total viable bacterial count (TVC) was influenced by the depth-wise stratification of salinity, which varied with tidal fluctuation, usually high and low during the neap and spring tides respectively. The abundance of both the autochthonous Vibrio spp. and allochthonous coliform bacteria was influenced by the concentrations of dissolved nutrients and suspended particulate matter (SPM). It is concluded that depending on the interplay of riverine discharge and tidal amplitude, sediment re-suspension mediated increase in SPM significantly regulates bacteria populations in the estuarine water, urging the need of systematic regular monitoring for better prediction of related hazards, including those associated with the rise in pathogenic Vibrio spp. in the changing climatic scenarios.

Biomonitoring along the Tropical Southern Indian Coast with Multiple Biomarkers

We assessed the spatial and temporal variations of pollution indicators and geochemical and trace metal parameters (23 in total) from water and sediment (144 samples) of three different eco-niches (beach, fishing harbor, and estuary) in larger coastal cities of southern India (Cuddalore and Pondicherry) for one year. A total of 120 marine Pseudomonas isolates were challenged against different concentrations of copper solutions and 10 different antibiotics in heavy metal and antibiotic resistance approaches, respectively. The study shows that 4.16% of the isolates could survive in 250 mM of copper; 70% were resistant to minimum concentrations. Strains were resistant (98.4%) to at least one antibiotic in Cuddalore compared to the Pondicherry (78.4%) region. Pollution index (PI) (0-14.55) and antibiotic resistance index (ARI) (0.05-0.10) ratio indicated that high bacterial and antibiotic loads were released into the coastal environment. The degree of trace metal contamination in sediments were calculated by enrichment factor (EF), contamination factor (CF), pollution load index (PLI), and geo-accumulation index (Igeo). Statistical parameters like two-way analysis of variance (ANOVA), correlation, factor analysis and scatter matrix tools were employed between the 23 parameters in order to find sources, pathways, disparities and interactions of environmental pollutants. It indicates that geochemical and biological parameters were not strongly associated with each other (except a few) and were affected by different sources. Factor analysis elucidated, 'microbe-metal' interaction (Factor 1-48.86%), 'anthropogenic' factor (Factor 2-13.23%) and 'Pseudomonas-Cadmium' factor (Factor 3-11.74%), respectively.

Modeling and kinetic characterization of wastewater disinfection using chlorine and UV irradiation

Sewage disinfection has the primary objective of inactivating pathogenic organisms to prevent the dissemination of waterborne diseases. This study analyzed individual disinfection, with chlorine alone, ultraviolet radiation alone, and a combined disinfection process (chlorine-UV radiation). Pseudomonas aeruginosa ATCC 15442, Escherichia coli ATCC 11229, Salmonella typhi ATCC 14028, and Clostridium perfringens were selected to evaluate the efficiency of different disinfection processes. The aim of the present study was to characterize the kinetics of chlorine (as NaHOCl) consumption, to evaluate responses of these bacterial species to the chlorination, the ultraviolet (UV) radiation, and the chlorine/UV disinfection processes in secondary wastewater using a batch laboratory reactor. Another target of this work was to study the modeling of the kinetic of water disinfection by chlorination and/or UV irradiation. Two kinetic models (Chick-Watson and Hom) were tested as to ability to scale disinfection of these bacterial species by different ultraviolet and/or chlorine doses. The results of the kinetics of chlorine consumption showed that monochloramines and trichloramines were the most important forms of residual chlorine as compared to free chlorine and dichloramines. The kinetics of inactivation of all examined bacterial strains showed that the application of the model of Hom in its original form was not representative of this kinetics of inactivation. Modification of this model, considering an initial decline of bacteria during the contact of water with chlorine, improved the results of the model. By the same, results revealed that the involved processes of UV irradiation were too complex to be approached by a simplified formulation, even in the case of specific strains of microorganisms and the use of nearly constant UV radiation intensity. In fact, the results have pointed out that the application of the Chick-Watson law is known to be inadequate to describe microbial inactivation with tailing or shoulder behavior. However, the UV kinetic studies also revealed that the first instants of exposure (2 to 10 s) to a UV intensity of 5 to 8 mW.cm-2 appeared as the deciding factors in disinfection with UV irradiation. It was shown that the combination of chlorine with UV yielded additive effects on the inactivation of bacterial strains and spectacular disinfection efficiency at a short contact time and less dose. In contrast to most studies, UV irradiation alone and chlorine alone exhibited low disinfection efficiency in inactivation of tested bacterial strains.

Diversity, community structure, and bioremediation potential of mercury-resistant marine bacteria of estuarine and coastal environments of Odisha, India

Both point and non-point sources increase the pollution status of mercury and increase the population of mercury-resistant marine bacteria (MRMB). They can be targeted as the indicator organism to access marine mercury pollution, besides utilization in bioremediation. Thus, sediment and water samples were collected for 2 years (2010-2012) along Odisha coast of Bay of Bengal, India. Mercury content of the study sites varied from 0.47 to 0.99 ppb irrespective of the seasons of sampling. A strong positive correlation was observed between mercury content and MRMB population (P < 0.05) suggesting the utilization of these bacteria to assess the level of mercury pollution in the marine environment. Seventy-eight percent of the MRMB isolates were under the phylum Firmicutes, and 36 and 31% of them could resist mercury by mer operon-mediated volatilization and mercury biosorption, respectively. In addition, most of the isolates could resist a number of antibiotics and toxic metals. All the MRMB isolates possess the potential of growth and survival at cardinal pH (4-8), temperature (25-37 °C), and salinity (5-35 psu). Enterobacteria repetitive intergenic consensus (ERIC) and repetitive element palindromic PCR (REP-PCR) produced fingerprints corroborating the results of 16S rRNA gene sequencing. Fourier transform infrared (FTIR) spectral analysis also revealed strain-level speciation and phylogenetic relationships.

An appraisal of biological responses and network of environmental interactions in non-mining and mining impacted coastal waters

The coastal waters of Goa and Ratnagiri lying on the West coast of India are influenced by terrestrial influx. However, Goa is influenced anthropogenically by iron-ore mining, while Ratnagiri is influenced by deposition of heavy minerals containing iron brought from the hinterlands. We hypothesize that there could be a shift in biological response along with changes in network of interactions between environmental and biological variables in these mining and non-mining impacted regions, lying 160 nmi apart. Biological and environmental parameters were analyzed during pre-monsoon season. Except silicates, the measured parameters were higher at Goa and related significantly, suggesting bacteria centric, detritus-driven region. At Ratnagiri, phytoplankton biomass related positively with silicate suggesting a region dominated by primary producers. This dominance perhaps got reflected as a higher tertiary yield. Thus, even though the regions are geographically proximate, the different biological response could be attributed to the differences in the web of interactions between the measured variables.

Daily variations in pathogenic bacterial populations in a monsoon influenced tropical environment

Changing climatic conditions have influenced the monsoon pattern in recent years. Variations in bacterial population in one such tropical environment were observed everyday over two years and point out intra and inter annual changes driven by the intensity of rainfall. Vibrio spp. were abundant during the monsoon and so were faecal coliforms. Vibrio alginolyticus were negatively influenced by nitrate, whereas, silicate and rainfall positively influenced Vibrio parahaemolyticus numbers. It is also known that pathogenic bacteria are associated with the plankton. Changes in the abundance of plankton, which are governed mainly by environmental changes, could be responsible for variation in pathogenic bacterial abundance during monsoon, other than the land runoff due to precipitation and influx of fresh water.

The effects of precipitation, river discharge, land use and coastal circulation on water quality in coastal Maine

Faecal pollution in stormwater, wastewater and direct run-off can carry zoonotic pathogens to streams, rivers and the ocean, reduce water quality, and affect both recreational and commercial fishing areas of the coastal ocean. Typically, the closure of beaches and commercial fishing areas is governed by the testing for the presence of faecal bacteria, which requires an 18-24 h period for sample incubation. As water quality can change during this testing period, the need for accurate and timely predictions of coastal water quality has become acute. In this study, we: (i) examine the relationship between water quality, precipitation and river discharge at several locations within the Gulf of Maine, and (ii) use multiple linear regression models based on readily obtainable hydrometeorological measurements to predict water quality events at five coastal locations. Analysis of a 12 year dataset revealed that high river discharge and/or precipitation events can lead to reduced water quality; however, the use of only these two parameters to predict water quality can result in a number of errors. Analysis of a higher frequency, 2 year study using multiple linear regression models revealed that precipitation, salinity, river discharge, winds, seasonality and coastal circulation correlate with variations in water quality. Although there has been extensive development of regression models for freshwater, this is one of the first attempts to create a mechanistic model to predict water quality in coastal marine waters. Model performance is similar to that of efforts in other regions, which have incorporated models into water resource managers' decisions, indicating that the use of a mechanistic model in coastal Maine is feasible.

Influence of river discharge on abundance and dissemination of heterotrophic, indicator and pathogenic bacteria along the East Coast of India

In order to examine the influence of discharge from different rivers from peninsular India and urban sewage on intensity and dissemination of heterotrophic, indicator and pathogenic bacteria, a study was carried out during peak discharge period along coastal Bay of Bengal. The coastal Bay received freshwater inputs from the river Ganges while Godavari and Krishna contributed to the south. Contrasting difference in salinity, temperature, nutrients and organic matter was observed between north and south east coast of India. The highest heterotrophic, indicator and pathogenic bacterial abundance was observed in the central coastal Bay that received urban sewage from the major city. Intensity and dissemination of heterotrophic, indicator and pathogenic bacteria displayed linear relation with magnitude of discharge. The coliform load was observed up to 100km from the coast suggesting that marine waters were polluted during the monsoon season and its impact on the ecosystem needs further studies.

Prevalence and genetic profiles of Escherichia coli from mangroves and mangrove associated foods off Goa, India

A total of 120 samples comprising of water (45), sediment (45) and mangrove originated food (30) collected from mangrove ecosystems of Goa were screened for Escherichia coli employing ISO-16654 method. Seventy-one (59.16%) samples were positive for E. coli. The E. coli isolates were further characterized by serotyping, virulence gene profiling and pulsed field gel electrophoresis (PFGE). Water and sediment samples were analyzed for physico-chemical parameters. The serotypes reported were O1, O10, O13, O17, O36, O41, O50, O68, O105, O116, O141, O148, O159, O162 and rough types while, 23 strains could not be typed. The stx1 and stx2 genes were detected in 33(46.47%) and 16(22.53%) isolates, respectively. The XbaI restriction digestion patterns of the stx positive strains were diverse. Interestingly, few strains isolated from diarrheal patients and from water, sediment and food from mangrove sources were genetically similar. The study showed that the mangrove ecosystem could be a potential reservoir for pathogenic E. coli.

Physicochemical parameters aid microbial community? A case study from marine recreational beaches, Southern India

A total of 176 (water and sediment) samples from 22 stations belonging to four different (urban, semi-urban, rural, and holy places) human habitations of Tamil Nadu beaches were collected and analyzed for physiochemical and microbial parameters during 2008-2009. Bacterial counts were two- to tenfold higher in sediments than in water due to strong bacterial aggregations by dynamic flocculation and rich organic content. The elevated bacterial communities during the monsoon explain rainfalls and several other wastes from inlands. Coliform counts drastically increased at holy and urban places due to pilgrimage and other ritual activities. Higher values of the pollution index (PI) ratio (>1) reveals, human fecal pollutions affect the water quality. The averaged PI ratio shows a substantial higher microbial contamination in holy places than in urban areas and the order of decreasing PI ratios observed were: holy places > urban areas > semi-urban areas > rural areas. Correlation and factor analysis proves microbial communities were not related to physicochemical parameters. Principal component analysis indicates 55.32 % of the total variance resulted from human/animal fecal matters and sewage contaminants whereas 19.95 % were related to organic contents and waste materials from the rivers. More than 80 % of the samples showed a higher fecal coliform and Streptococci by crossing the World Health Organization's permissible limits.

Microbiological composition of native and exotic clams from Tagus estuary: effect of season and environmental parameters

The influence of seasonal and environmental parameters on the occurrence of bacteria was investigated in two clam species (Venerupis pullastra and Ruditapes philippinarum), water and sediment from the Tagus estuary. Total viable counts (TVC), Escherichia coli, Salmonella spp. and Vibrio spp. were evaluated during one-year. Overall, significant seasonal variations were found in both sampling sites, especially for E. coli and Vibrio spp. levels. In summer, significantly higher Vibrio spp. levels were found in R. philippinarum and sediment samples, but not in V. pullastra clams and water samples. In contrast, significantly higher TVC and E. coli levels were observed in winter months in water and sediment samples. Salmonella spp. was generally isolated when higher levels of E. coli were detected, particularly in R. philippinarum. This study is useful for authorities to develop monitoring strategies for coastal contamination and to estimate human health risks associated with the consumption of bivalves.

Prevalence, antimicrobial resistance and relation to indicator and pathogenic microorganisms of Salmonella enterica isolated from surface waters within an agricultural landscape

During a 12 month period (June 2007-May 2008), the prevalence and susceptibility of Salmonella serovars and their relation to specific pathogenic and indicator bacteria in river and coastal waters was investigated. A total of 240 water samples were collected from selected sites in Acheron and Kalamas Rivers and the Ionian Sea coast in north western Greece. The samples were analyzed for Salmonella spp., Listeria spp., Campylobacter spp., Escherichia coli O157, Staphylococci, Pseudomonas spp., Total Coliforms, Fecal Coliforms, Fecal Streptococci, Total Heterotrophic Flora at 20°C and at 37°C, fungi and protozoa (Cryptosporidium, Giardia). Susceptibility tests to nine antimicrobials (ampicillin, amikacin, amoxicillin/clavulavic acid, cefuroxime, ciprofloxacin, cefoxitin, tetracycline, ticarcillin/clavulanic acid, ampicillin/sulbactam) were performed using the disk diffusion method for Salmonella isolates. We isolated 28 serovars of Salmonella spp. identified as Salmonella enteritidis (23), Salmonella thompson (3) and Salmonella virchow (2). Multi-drug resistant Salmonella serovars were isolated from both river and marine waters, with 34.8% of S. enteritidis and 100% of S. virchow being resistant to more than 3 antibiotics. Also we isolated 42 strains of Listeria spp. identified as L. monocytogenes (20), L. innocua (9), L. seeligeri (2) and L. ivanovii (11). All the Listeria isolates were susceptible to the tested antibiotics. No Campylobacter spp., E. coli O157, Cryptosporidium and Giardia were detected. The overall ranges (and average counts) of the indicator bacteria were: Total Coliforms 0-4×10(4)cfu/100ml (3.7×10(3)cfu/100ml), Fecal Coliforms 0-9×10(3)cfu/100ml (9.2×10(2)cfu/100ml), Fecal Streptococci 0-3.5×10(4)cfu/100ml (1.4×10(3)cfu/100ml), Total Heterotrophic Flora at 20°C 0-6×10(3)cfu/ml (10(3)cfu/ml) and at 37°C 0-5×10(3)cfu/ml (4.9×10(2)cfu/ml). Weak or non significant positive Spearman correlations (p<0.05, rs range: 0.13-0.77) were obtained between Salmonella, Listeria, fungi and indicator bacteria. The results underline the complexity of the interrelations between pathogens and indicator bacteria, and the necessity to assess the presence of resistant bacteria in the aquatic environments.