The relationships between salmonellas and faecal indicator concentrations in two pools in the Australian wet/dry tropics

S.A. TOWNSEND. 1992. The relationships between total coliform, faecal coliform, enterococci and salmonella concentrations were investigated at Berry and Howard Pools in the Australian wet/dry tropics. Both pools have catchments with minimal human activity and no major point source of faecal pollution. Forty-five indicator and salmonella enumerations were made from each pool over a 1 year period. Salmonellas were isolated from 69% and 96% of samples collected from Howard and Berry Pools respectively, the maximum (MPN) concentration was 110/100 ml. Native fauna were the primary salmonella source. Spearman rank correlations between indicator organisms and salmonella at Howard Pool were significant at the 5% level and approximated 0.6. At Berry Pool, total coliform and enterococci Spearman rank correlations with salmonella were also statistically significant, approximating 0.3; faecal coliforms and salmonella rankings, however, were unrelated. The higher correlation coefficients at Howard Pool were attributed to its small catchment (4 km²) and the more recent nature of faecal contamination compared with Berry Pool which has a catchment of 130 km². The results highlight the spatial variability of the indicator/pathogen numerical relationship. Total coliform and enterococci counts, as indicators of faecal pollution, were similar and more consistent than faecal coliforms.     

Indicator organism sources and coastal water quality: a catchment study on the Island of Jersey

Compliance monitoring of bathing waters at La Grève de Lecq on the North coast of Jersey revealed a significant deterioration in water quality between 1992 and 1993, as indexed by presumptive coliform, presumptive Escherichia coli and streptococci concentrations. During the 1993 bathing season the beach failed to attain the compliance with the EC Guideline criteria for presumptive E. coli and streptococci. A bacteriological survey of the stream catchment draining to the beach revealed that: (i) concentrations of faecal indicator organisms were enhanced at high discharge after rainfall; and (ii) a captive water fowl population, which expanded between 1990 and 1993, was a potential source of faecal pollution. Strategies for catchment management are discussed.     

Preliminary study of microbiological parameters in eight inland recreational waters

A pilot survey of the counts of total coliform bacteria, thermotolerant coliform bacteria, Escherichia coli and faecal streptococci was carried out at eight inland recreational waters at weekly intervals during July 1991. The aims were to assess the feasibility of determining candidate indicators of recreational water quality and to assess the possible scale of variability of these parameters. The numbers of total coliforms were difficult to determine reliably because of interference from the background bacterial flora. There was a strong correlation between thermotolerant coliforms and E. coli and faecal streptococci. The average counts of the indicator organisms varied between and within the eight recreational waters by up to 10000-fold. The greatest variation was between the eight recreational waters. At any one water, the greatest source of variation was time but there was substantial variation between sample points at one time. Counts in samples collected 1 m apart exhibited greater than random variation. Counts from surface samples tended to be higher than those at 30 cm or 100 cm depth. The proportion of thermotolerant coliforms confirmed to be E. coli varied from water to water between 60% and 96%.     

Investigation of human sewage pollution and pathogen analysis at Florida Gulf coast beaches

Aims: Water quality at two Florida beaches was compared using faecal indicator bacteria measurements, microbial source tracking (MST) methods for detecting human source pollution and the assessment of pathogen presence. These values were also compared before and after remediation of wastewater infrastructure at one beach. Methods and Results: Faecal coliforms, Escherichia coli and enterococci were enumerated in estuarine water and sediment samples. PCR assays for the human‐associated esp gene of Enterococcus faecium and human polyomaviruses (HPyVs) were used to detect human sewage. Culturable Salmonella and enteric viruses were also analysed. MST identified human sewage contamination at one beach, leading to repair of a sewer main and relocation of portable restrooms. Exceedances of Florida recreational water regulatory standards were significantly reduced after remediation (by 52% for faecal coliforms and 39% for enterococci), and the frequency of detection of MST markers decreased. Coxsackie virus B4 and HPyVs were codetected following a major sewage spill, but Salmonella was not detected during the study. Conclusions: These data indicate that infrastructure remediation significantly reduced pollution from human sewage at the impacted beach. Significance and Impact of the Study: A comprehensive microbial water quality study that can identify contamination sources through the use of MST markers and close collaboration with local/and state agencies can result in tangible actions to improve recreational water quality and safety.     

Sanitary quality of marine sediments and sands from an Italian beach

Microbiological surveys were carried out on marine sands and sediments collected at a sandy beach along a coastal area close to Rome, Italy. Low densities of faecal indicator bacteria were recovered, and among them enterococci outnumbered the coliforms. The group of staphylococci was in a fairly constant concentration throughout the period of sampling. Some statistically significant correlations were calculated between yeasts and moulds, Escherichia coli and enterococci and between the latter and Clostridium spores. The data obtained could be a reference point for further studies.     

Higher prevalence of Alternaria spp. in marine and river waters than in potable samples

Alternaria species have been recognized as important cause of allergic diseases and are considered opportunistic pathogens for immunocompromised individuals. In order to assess the contribution of waters to the spread of Alternaria, we examined 390 water samples of various origin for the presence of these microorganisms in parallel with the standard pollution indicator bacteria, i.e. total coliforms, faecal coliforms and enterococci. Alternaria spp. were isolated from 42 out of 196 (21.4%) marine water samples, from 13 out of 68 (19.1%) river samples, whereas out of 126 potable waters only two (1.6%) were found positive. The incidence of Alternaria was significantly higher (p < 0.001) in marine and river samples than in potable waters. The mean values of the colony-forming units of the pollution indicator bacteria did not significantly differ between Alternaria-positive and Alternaria-negative samples.     

Soil: the environmental source of Escherichia coli and Enterococci in Guam's streams

We have previously documented that faecal indicator bacteria (Escherichia coli, faecal coliform, enterococci) recommended by the U.S. Environmental Protection Agency (USEPA) to establish recreational water quality standards are naturally found in high concentrations in the surface and subsurface of soils in Hawaii. Rain, the source of all streams in Hawaii, washes the soil sources of faecal bacteria into all the streams of Hawaii, at concentrations which consistently exceed the USEPA recreational water quality standards. The objective of this study was to test the hypothesis that faecal bacteria are able to establish themselves in the soil environments of tropical islands by conducting the same study in Guam, a tropical pacific island with warmer temperatures and higher humidity than Hawaii. The same methods and study design used in Hawaii was used in Guam. The results of the study conducted in Guam revealed that all streams contain consistently high concentrations of faecal coliform, E. coli, and enterocci which exceeded the old USEPA recreational water quality standard of 200 faecal coliform/100 ml as well as the new water quality standards of 126 E. coli/100 ml or 33 enterococci/100 ml. These same faecal indicator bacteria were recovered in high concentrations in surface and subsurface (18-36 cm depth) soil samples in Guam. Limited coastal water analysis showed that most coastal marine waters contain low concentrations of faecal bacteria but coastal waters impacted by stream run-off showed elevated levels of faecal bacteria. The results of this study support the hypothesis that environmental conditions in the tropical areas of the world can support the growth and establishment of populations of faecal bacteria in the soil. Thus, soil becomes an environmental, non-faecal source of faecal indicator bacteria. These results indicate that USEPA water quality standards may not be directly applicable to tropical island environments.     

Contamination of milk by enterococci and coliforms from bovine faeces

AIM: To determine the contribution of enterococci and coliforms from bovine faeces and teats to contamination of raw milk. Methods: Putative enterococci (n = 301) and coliforms (n = 365) were isolated from bovine faeces (n = 20), cows' teats (n = 20), the raw milk (n = 1) and the milking environment (n = 4) on one farm. The clonal relationships of each bacterial group were investigated using Pulsed-Field Gel Electrophoresis of genomic macrorestriction fragments. Representatives of the different clusters of enterococci were identified by molecular techniques including rep-PCR, SDS protein profiling, Fluorescent Amplified Fragment Length Polymorphism (FAFLP), phenylalanyl-tRNA synthase (pheS) sequence analysis and/or 16S rDNA gene sequencing. Coliforms were identified by API 20E strips. RESULTS: The majority of the bovine faecal enterococcal isolates were identified as a potential new species of Aerococcus (100 isolates); E. faecium (28 isolates), and Aerococcus viridans (28 isolates) were also found. All coliform isolates from the bovine faeces were identified as Escherichia coli. The coliforms present in the milk were Hafnia alvei, Serratia liquefaciens, Yersinia enterocolitica and Enterobacter amnigenus. No E. coli, Enterococcus or Aerococcus from the bovine faeces were found in the milk. A single clone of H. alvei was found in the water, the milking equipment and the milk, suggesting that the water was the source of the organism in the milk. No vancomycin-resistant aerococci or enterococci were found while most of the isolates tested showed the presence of at least one virulence gene. The milk-sock retained strains that adhered to particulate faecal material. Coliforms were present at approx. 2 orders of magnitude greater than enterococci in the bovine faeces. CONCLUSIONS: The results imply that bovine faeces are not an important source of contamination of raw milk with enterococci or coliforms. SIGNIFICANCE AND IMPACT OF THE STUDY: The results confirm those of two previous studies (Gelsomino et al. 2001, Int J Food Microbiol71, 177-188 and Kagkli et al. 2007, Int J Food Microbiol114, 243-251) on two other farms. The three studies show that contamination of milk by enterococci, lactobacilli and coliforms of bovine faecal origin is extremely low. The results also suggest that where raw milk is implicated in food infection, other factors in addition to faecal contamination must be involved.     

Occurrence and densities of bacteriophages proposed as indicators and bacterial indicators in river waters from Europe and South America

AIMS: To evaluate the feasibility of bacteriophages as a complementary tool for water quality assessment in surface waters from different parts of the globe. METHODS AND RESULTS: Faecal coliform bacteria, enterococci, spores of sulphite-reducing clostridia, somatic coliphages, F-specific RNA bacteriophages and bacteriophages infecting Bacteroides fragilis were determined by standardized methods in raw sewage and in 392 samples of river water from 22 sampling sites in 10 rivers in Argentina, Colombia, France and Spain, which represent very different climatic and socio-economic conditions. The results showed that the indicators studied maintained the same relative densities in the raw sewage from the different areas. Classifying the river water samples according to the content of faecal coliform bacteria, it can be observed that the relative densities of the different bacterial indicators and bacteriophages changed according to the concentration of faecal coliform bacteria. There was a relative increase in the densities of all groups of bacteriophages and sulphite-reducing clostridia with respect to faecal coliforms and enterococci in the samples with low counts of faecal coliform bacteria. CONCLUSIONS: The numbers of bacterial indicators and bacteriophages were similar in the different geographical areas studied. Once released in rivers, the persistence of the different micro-organisms differed significantly. Bacteriophages and spores of sulphite-reducing clostridia persisted longer than faecal coliforms and enterococci. SIGNIFICANCE AND IMPACT OF THE STUDY: Bacteriophages in river water samples provide additional information to that provided by bacteria about the fate of faecal micro-organisms in river water. The easy, fast and cheap methods for phage determination are feasible both in industrialized and developing countries.     

Virus occurrence in municipal groundwater sources in Quebec, Canada

A 1 year study was undertaken on groundwater that was a source of drinking water in the province of Quebec, Canada. Twelve municipal wells (raw water) were sampled monthly during a 1 year period, for a total of 160 samples. Using historic data, the 12 sites were categorized into 3 groups: group A (no known contamination), group B (sporadically contaminated by total coliforms), and group C (historic and continuous contamination by total coliforms and (or) fecal coliforms). Bacterial indicators (total coliform, Escherichia coli, enteroccoci), viral indicators (somatic and male-specific coliphages), total culturable human enteric viruses, and noroviruses were analyzed at every sampling site. Total coliforms were the best indicator of microbial degradation, and coliform bacteria were always present at the same time as human enteric viruses. Two samples contained human enteric viruses but no fecal pollution indicators (E. coli, enterococci, or coliphages), suggesting the limited value of these microorganisms in predicting the presence of human enteric viruses in groundwater. Our results underline the value of historic data in assessing the vulnerability of a well on the basis of raw water quality and in detecting degradation of the source. This project allowed us to characterize the microbiologic and virologic quality of groundwater used as municipal drinking water sources in Quebec.     

Modelling faecal indicator concentrations in large rural catchments using land use and topographic data

AIMS: To characterize and model spatial variations in faecal-indicator organism concentrations in watercourses draining a large rural catchment during the bathing season. METHODS AND RESULTS: Presumptive coliform (PC), presumptive Eschericia coli (PE) and presumptive enterococci (PEnt) concentrations were determined under base- and high-flow conditions at 24 monitoring points in the Rheidol/Ystwyth catchment, Wales. Relationships with land use and topographic variables within their 'subcatchments' were investigated. Geometric mean (GM) concentrations typically increase more than 10-fold at high flow. The proportion of improved pasture within subcatchments explains 81.6, 73.0 and 85.8%, respectively, of the variance in high-flow GM PC, PE and PEnt concentrations. Distributed modelling suggests that organisms derived from more distant parts of subcatchments may be lost through die-off and sedimentation along watercourses at base flow, although not at high flow. Reductions in concentrations are also evident downstream of reservoir impoundments. CONCLUSIONS: Large rural catchments may contribute substantially to faecal indicator loadings in coastal waters. Indicator concentrations can be modelled successfully using land use and topographic data. SIGNIFICANCE AND IMPACT OF THE STUDY: Development of a modelling approach that provides valuable insight into faecal indicator sources and the transport and survival of these organisms within large catchments.     

Quantitative microbial faecal source tracking with sampling guided by hydrological catchment dynamics

The impairment of water quality by faecal pollution is a global public health concern. Microbial source tracking methods help to identify faecal sources but the few recent quantitative microbial source tracking applications disregarded catchment hydrology and pollution dynamics. This quantitative microbial source tracking study, conducted in a large karstic spring catchment potentially influenced by humans and ruminant animals, was based on a tiered sampling approach: a 31-month water quality monitoring (Monitoring) covering seasonal hydrological dynamics and an investigation of flood events (Events) as periods of the strongest pollution. The detection of a ruminant-specific and a human-specific faecal Bacteroidetes marker by quantitative real-time PCR was complemented by standard microbiological and on-line hydrological parameters. Both quantitative microbial source tracking markers were detected in spring water during Monitoring and Events, with preponderance of the ruminant-specific marker. Applying multiparametric analysis of all data allowed linking the ruminant-specific marker to general faecal pollution indicators, especially during Events. Up to 80% of the variation of faecal indicator levels during Events could be explained by ruminant-specific marker levels proving the dominance of ruminant faecal sources in the catchment. Furthermore, soil was ruled out as a source of quantitative microbial source tracking markers. This study demonstrates the applicability of quantitative microbial source tracking methods and highlights the prerequisite of considering hydrological catchment dynamics in source tracking study design.     

Removal and inactivation of indicator bacteriophages in fresh waters

AIMS: The removal and inactivation of faecal coliform (FC) bacteria, enterococci (ENT), sulphite-reducing clostridia (SRC), somatic coliphages, F-specific RNA bacteriophages and bacteriophages infecting Bacteroides fragilis in fresh waters. METHODS AND RESULTS: Removal was studied in two areas of a river. The results showed different removal of each group of microbes. Faecal coliform bacteria were removed faster than any other, whereas SRC and bacteriophages infecting Bact. fragilis were the most persistent. Inactivation was measured by 'in situ' experiments, which showed significant differences in survival of the different groups of bacterial and bacteriophage indicators. The SRC and bacteriophages were more resistant than faecal coliforms and enterococci, with the exception of F-specific RNA bacteriophages in the summer. Inactivation experiments with pure cultures of bacteriophages confirmed that phage B40-8 of Bact. fragilis was the most resistant. CONCLUSIONS: Bacteria and bacteriophages show different resistance to natural inactivation. The use of phages allows information to be obtained in addition to that provided by bacterial indicators. Somatic coliphages and phages infecting Bact. fragilis might supply that indicator function. SIGNIFICANCE AND IMPACT OF THE STUDY: Confirmation was obtained that bacteriophages provided additional information to that provided by bacterial indicators to monitor the natural inactivation of viruses and/or pathogens.     

Relation between Aeromonas and faecal coliforms in fresh waters

A possible correlation between the presence of mesophilic aeromonads and the number of faecal coliforms present in three fresh-water habitats subject to differing levels of faecal pollution was investigated. Concentration of Aeromonas spp. between 10²–10⁹ cfu/100 ml and faecal coliforms of between 9–10⁷ cfu/100 ml were found in the waters. In water free from faecal pollution there was no correlation but in polluted waters there was a significant relationship between the numbers of aeromonads, faecal coliform and the concentration of organic matter measured by biological oxygen demand.     

Magnitude of pollution indicator organisms in rural potable water.

A total of 460 water samples were randomly drawn from the potable water supply sources of rural communities in three counties of South Carolina. About 10% of the population, not incorporated in municipalities, was sampled. The samples were tested for total coliforms, Escherichia coli, and fecal streptococci. Significant levels of these pollution indicator organisms were detected in almost all the water supplies. Total coliforms were the most common, and only 7.5% of the water supplies were uncontaminated. E. coli, considered a reliable indicator of recent and dangerous pollution, was observed in 43% of the water supplies. Statistical analyses indicated that the bacterial populations, especially E. coli, were associated with the supply source depth and its distance from the septic tank. Total coliform counts were also weakly correlated to the pH of the water.     

Magnitude of pollution indicator organisms in rural potable water.

A total of 460 water samples were randomly drawn from the potable water supply sources of rural communities in three counties of South Carolina. About 10% of the population, not incorporated in municipalities, was sampled. The samples were tested for total coliforms, Escherichia coli, and fecal streptococci. Significant levels of these pollution indicator organisms were detected in almost all the water supplies. Total coliforms were the most common, and only 7.5% of the water supplies were uncontaminated. E. coli, considered a reliable indicator of recent and dangerous pollution, was observed in 43% of the water supplies. Statistical analyses indicated that the bacterial populations, especially E. coli, were associated with the supply source depth and its distance from the septic tank. Total coliform counts were also weakly correlated to the pH of the water.     

Escherichia coli and enterococci are sensitive and reliable indicators for human,livestock and wildlife faecal pollution in alpine mountainous water resources

Aims: This study evaluated the applicability of standard faecal indicator bacteria (SFIB) for alpine mountainous water resources monitoring. Methods and Results: Escherichia coli, enterococci (ENTC) and Clostridium perfringens were investigated by standard or frequently applied phenotypic and genotypic methods in a broad range of animal and human faecal sources in a large alpine mountainous area. Clostridium perfringens occurred only in human, livestock and carnivorous source groups in relevant average concentrations (log 4·7–7·0 CFU g^?1) but not in herbivorous wildlife sources. Escherichia coli proved to be distributed in all faecal source groups with remarkably balanced average concentrations (log 7·0–8·4 CFU g^?1). Except for single faecal samples from the cattle source group, prevalence rates for ENTC source groups were generally >87% with average concentrations of log 5·3–7·7 CFU g^?1. To test the faecal indication capacity in the environment, faecal prevalence data were comparatively analysed with results from the concurrently performed multi‐parametric microbial source tracking effort on karst spring water quality from the investigated alpine mountainous catchment ( Reischer et al. 2008 ; Environ Microbiol 10:2598–2608). Conclusion: Escherichia coli and enterococci are reliable faecal indicators for alpine mountainous water resources monitoring, although E. coli is the more sensitive one. Clostridium perfringens did not prove to be an indicator of general faecal pollution but is suggested a conservative microbial source tracking marker for anthropogenic faecal influence. Significance and Impact of the Study: Applicability of SFIB is currently hotly debated. This is the first study providing comprehensive information on the applicability of SFIB at alpine mountainous habitats.     

Antibiotic resistance of bacteria in raw and biologically treated sewage and in groundwater below leaking sewers

More than 750 isolates of faecal coliforms (>200 strains), enterococci (>200 strains) and pseudomonads (>340 strains) from three wastewater treatment plants (WTPs) and from four groundwater wells in the vicinity of leaking sewers were tested for resistance against 14 antibiotics. Most, or at least some, strains of the three bacterial groups, isolated from raw or treated sewage of the three WTPs, were resistant against penicillin G, ampicillin, vancomycin, erythromycin, triple sulfa and trimethoprim/sulfamethoxazole (SXT). Only a few strains of pseudomonads or faecal coliforms were resistant against some of the other tested antibiotics. The antibiotic resistances of pseudomonads, faecal coliforms and enterococci from groundwater varied to a higher extent. In contrast to the faecal coliforms and enterococci, most pseudomonads from all groundwater samples, including those from non-polluted groundwater, were additionally resistant against chloramphenicol and SXT. Pseudomonads from sewage and groundwater had more multiple antibiotic resistances than the faecal coliforms or the enterococci, and many pseudomonads from groundwater were resistant to more antibiotics than those from sewage. The pseudomonads from non-polluted groundwater were the most resistant isolates of all. The few surviving faecal coliforms in groundwater seemed to gain multiple antibiotic resistances, whereas the enterococci lost antibiotic resistances. Pseudomonads, and presumably, other autochthonous soil or groundwater bacteria, such as antibiotic-producing Actinomyces sp., seem to contribute significantly to the gene pool for acquisition of resistances against antibiotics in these environments.     

Bacteriological water quality effects of hydraulically dredging contaminated upper Mississippi River bottom sediment.

Bacteriological effects of hydraulically dredging polluted bottom sediment in the navigation channel of the Upper Mississippi River (river mile 827.5 [about 1,332 km] to 828.1 [about 1,333 km]) were investigated. Bottom sediment in the dredging site contained high total coliform densities (about 6,800 most-probable-number total coliform index per g [dry weight] and 3,800 membrane filter total coliforms per g [dry weight]), and fecal coliforms comprised an average 32% of each total coliform count. Total coliform and fecal coliform densities in water samples taken immediately below the dredge discharge pipe were each approximately four times corresponding upstream values; fecal streptococcus densities were approximately 50 times corresponding upstream values. Correlation analysis indicated that mean turbidity values downstream to the dredging operation were directly and significantly (r greater than 0.94) related to corresponding total coliform, fecal coliform, and fecal streptococcus densities. Salmonellae and shigellae were not recovered from either upstream or downstream water samples. Turbidity and indicator bacteria levels had returned to predredge values within less than 2 km below the dredge spoil discharge area at the prevailing current velocity (about 0.15 m/s).     

Application of microbial source tracking methods in a Gulf of Mexico field setting

Aims:  Microbial water quality and possible human sources of faecal pollution were assessed in a Florida estuary that serves shellfishing and recreational activities.
Methods and Results:  Indicator organisms (IO), including faecal coliforms, Escherichia coli and enterococci, were quantified from marine and river waters, sediments and oysters. Florida recreational water standards were infrequently exceeded (6–10% of samples); however, shellfishing standards were more frequently exceeded (28%). IO concentrations in oysters and overlaying waters were significantly correlated, but oyster and sediment IO concentrations were uncorrelated. The human-associated esp gene of Enterococcus faecium was detected in marine and fresh waters at sites with suspected human sewage contamination. Lagrangian drifters, used to determine the pathways of bacterial transport and deposition, suggested that sediment deposition from the Ochlockonee River contributes to frequent detection of esp at a Gulf of Mexico beach.
Conclusions:  These data indicate that human faecal pollution affects water quality in Wakulla County and that local topography and hydrology play a role in bacterial transport and deposition.
Significance and Impact of the Study:  A combination of IO enumeration, microbial source tracking methods and regional hydrological study can reliably inform regulatory agencies of IO sources, improving risk assessment and pollution mitigation in impaired waters.