Speciation and frequency of virulence genes of Enterococcus spp. isolated from rainwater tank samples in Southeast Queensland, Australia

White Teeth and Healthy Skeletons for All: The Path to Universal Fluoride-Free Drinking Water in Tanzania

Fluorosis has been prevalent in the great East African Rift Valley (EARV) since before this region was given a name. In the Tanganyika days, Germans reported elevated fluoride concentrations in natural waters. In the 1930s, the clear relationship between high fluoride level and mottling of teeth was established. Since then, the global research community has engaged in the battle to provide fluoride-free drinking water, and the battle is not yet won for low-income communities. An applicable concept for fluoride-free drinking water in the EARV was recently presented, using the Kilimanjaro as a rainwater harvesting park. The Kilimanjaro concept implies that rainwater is harvested, stored on the Kilimanjaro mountains, gravity-transported to the point of use, eventually blended with natural water and treated for distribution. This article provides a roadmap for the implementation of the Kilimanjaro concept in Tanzania. Specifically, the current paper addresses the following: (i) presents updated nationwide information on fluoride contaminated areas, (ii) discusses the quality and quantity of rainwater, and current rainwater harvesting practices in Tanzania, (iii) highlights how low-cost water filters based on Fe0/biochar can be integrating into rainwater harvesting (RWH) systems to provide clean drinking water, and (iv) discusses the need for strict regulation of RWH practices to optimize water collection and storage, while simplifying the water treatment chain, and recommends strict analytical monitoring of water quality and public education to sustain public health in the EARV. In summary, it is demonstrated that, by combining rainwater harvesting and low-cots water treatment methods, the Kilimanjaro concept has the potential to provide clean drinking water, and overcome fluorosis on a long-term basis. However, a detailed design process is required to determine: (i) institutional roles, and community contributions and participation, (ii) optimal location and sizing of conveyance and storage facilities to avoid excessive pumping costs, and (iii) project funding mechanisms, including prospects for government subsidy. By drawing attention to the Kilimanjaro concept, the article calls for African engineers and scientists to take the lead in translating this concept into reality for the benefit of public health, while simultaneously increasing their self-confidence to address other developmental challenges pervasive in Africa.

A Review of Roof Harvested Rainwater in Australia

To address concern regarding water sustainability, the Australian Federal Government and many state governments have implemented regulatory mechanisms and incentives to support households to purchase and install rainwater harvesting systems. This has led to an increase in rainwater harvesting in regional and urban Australia. This review examines the implementation of the regulatory mechanisms across Australia. In addition, the literature investigating the potential health consequences of rainwater consumption in Australia was explored. Studies demonstrated that although trace metals such as arsenic, cadmium, chromium, lead, and iron were present in Australian rainwater, these metallic elements were generally found below the health limit guideline, except in high industrial areas. In addition, pathogenic or indicator microorganisms that include, but are not limited to, Escherichia coli, total and faecal coliforms, Campylobacter, Salmonella, Legionella, Pseudomonas, Cryptosporidium, Enterococci, Giardia, Aeromonas, and Mycobacterium avium Complex (MAC) have been detected in rainwater collected in Australia. However, epidemiological evidence suggests that drinking rainwater does not increase the risk of gastrointestinal disease. It was also identified that there is a need for further research investigating the potential for rainwater to be a source of infection for opportunistic pathogens.

Virulence Genes among Enterococcus faecalis and Enterococcus faecium Isolated from Coastal Beaches and Human and Nonhuman Sources in Southern California and Puerto Rico

Most Enterococcus faecalis and E. faecium are harmless to humans; however, strains harboring virulence genes, including esp, gelE, cylA, asa1, and hyl, have been associated with human infections. E. faecalis and E. faecium are present in beach waters worldwide, yet little is known about their virulence potential. Here, multiplex PCR was used to compare the distribution of virulence genes among E. faecalis and E. faecium isolated from beaches in Southern California and Puerto Rico to isolates from potential sources including humans, animals, birds, and plants. All five virulence genes were found in E. faecalis and E. faecium from beach water, mostly among E. faecalis. gelE was the most common among isolates from all source types. There was a lower incidence of asa1, esp, cylA, and hyl genes among isolates from beach water, sewage, septage, urban runoff, sea wrack, and eelgrass as compared to human isolates, indicating that virulent strains of E. faecalis and E. faecium may not be widely disseminated at beaches. A higher frequency of asa1 and esp among E. faecalis from dogs and of asa1 among birds (mostly seagull) suggests that further studies on the distribution and virulence potential of strains carrying these genes may be warranted.

Screening probiotic strains for safety: Evaluation of virulence and antimicrobial susceptibility of enterococci from healthy Chinese infants

The aim of this study was to evaluate the safety of enterococci isolated from Chinese infants and screen out potential probiotic candidates. One hundred eight strains were isolated from feces of 34 healthy infants, and 38 strains of Enterococcus spp. were categorized as follows: E. faecalis (22), E. faecium (10), E. hirae (3), E. durans (2), and E. casseliflavus (1). Of these, 72.7% of E. faecalis came from infants delivered by cesarean and 62.5% of E. faecium from infants delivered vaginally. For safety evaluation of strains, we determined presence of virulence genes; production of hemolysin, gelatinase, and biofilm; and antimicrobial susceptibility of enterococci. Six out of 14 virulence genes were detected with a distribution of gelE (26.3%), cylA (39.4%), esp (15.8%), efaA (63.2%), asa1 (50.0%), and ace (50.0%). In phenotype analysis, 36.8% of the strains exhibited positive hemolytic activity and 17.5% were positive for production of gelatinase. Results of antimicrobial susceptibility showed that different percentages of the strains were resistant to ciprofloxacin (5.2%), vancomycin (7.8%), rifampicin (10.5%), erythromycin (52.6%), and gentamycin (52.6%); remarkably, none of the strains were resistant to ampicillin or chloramphenicol. In total, 10 strains, including 6 E. faecium, which are free of virulence determinants and sensitive to common antimicrobial agents (e.g., ampicillin and vancomycin), were further assessed for their probiotic properties. All strains survived well in simulated gastric fluid and intestinal tract, with maximum reductions of 0.600 and 0.887 log cfu/mL, respectively. Six strains of E. faecium could resist 0.3 to 1.0% bile salt, of which E. faecium WEFA23 presented the highest growth (75.06%) at 1.0% bile salt. All strains showed bile salt hydrolase activity on glycodeoxycholic acid, but only 3 of E. faecium showed activity on taurodeoxycholic acid. These results deliver useful information on the safety of enterococci in infants in China, and provide a protocol to screen probiotics for absence of virulence and antimicrobial susceptibility of enterococci.

Virulence determinants and production of extracellular enzymes in Enterococcus spp. from surface water sources

Virulence factors in Enterococcus may be indicative of potential pathogenicity. The aim of this study was to determine the relationship between the presence of clinically relevant virulence genes, in Enterococcus spp. from environmental water, and their in vitro expression. One hundred and twenty-four Enterococcus isolates (seven species), from five surface water systems in the North West Province, South Africa, were screened for the presence of asa1, cylA, esp, gelE and hyl using polymerase chain reaction. The expression of cylA, hyl and gelE was determined by phenotypic assessments. Sixty-five percent of the isolates were positive for one virulence gene and 13% for two or more. Most frequently detected genes were gelE (32%) and cylA (28%). Enterococcal surface protein was absent in all isolates screened. The presence of virulence genes was correlated with their extracellular enzyme production. The results show that a large percentage of these environmental Enterococcus spp. possess virulence factors that could be expressed in vitro. This is a cause for concern and could have implications for individuals using this water for recreational and cultural purposes. Further investigation is required into the sources of these potential pathogenic Enterococcus isolates and measures to minimize their presence in water sources.

Antimicrobial activity and the presence of virulence factors and bacteriocin structural genes in Enterococcus faecium CM33 isolated from ewe colostrum

Screening of lactic acid bacteria (LAB) isolated from ewe colostrum led to the identification and isolation of Enterococcus faecium CM33 with interesting features like high survival rates under acidic or bile salts condition, high tolerance for the simulated gastrointestinal condition, and high adhesive potential to Caco-2 cells. According the inhibition of pathogen adhesion test results, this strain can reduce more than 50% adhesion capacity of Escherichia coli, Shigella flexneri, Klebsiella pneumoniae, Listeria monocytogenes, and Staphylococcus aureus to Caco-2 cells. Based on the antibiotic sensitivity test findings, E. faecium CM33 was susceptible to gentamycin, vancomycin, erythromycin, ampicillin, penicillin, tetracycline, and rifampicin, but resistant to chloramphenicol, clindamycin, and kanamycin. Upon assessment of the virulence determinants for E. faecium CM33, this strain was negative for all tested virulence genes. Furthermore, the genome of this strain was evaluated for the incidence of the known enterocin genes by specific PCR amplification and discovered the genes encoding enterocins A, 31, X, and Q. Based on this study findings, the strain E. faecium CM33 can be considered as a valuable nutraceutical and can be introduced as a new potential probiotic.

Opportunistic pathogens in roof-captured rainwater samples, determined using quantitative PCR

In this study, quantitative PCR (qPCR) was used for the detection of four opportunistic bacterial pathogens in water samples collected from 72 rainwater tanks in Southeast Queensland, Australia. Tank water samples were also tested for fecal indicator bacteria (Escherichia coli and Enterococcus spp.) using culture-based methods. Among the 72 tank water samples tested, 74% and 94% samples contained E. coli and Enterococcus spp., respectively, and the numbers of E. coli and Enterococcus spp. in tank water samples ranged from 0.3 to 3.7 log₁₀ colony forming units (CFU) per 100 mL of water. In all, 29%, 15%, 13%, and 6% of tank water samples contained Aeromonas hydrophila, Staphylococcus aureus, Pseudomonas aeruginosa and Legionella pneumophila, respectively. The genomic units (GU) of opportunistic pathogens in tank water samples ranged from 1.5 to 4.6 log₁₀ GU per 100 mL of water. A significant correlation was found between E. coli and Enterococcus spp. numbers in pooled tank water samples data (Spearman's rs = 0.50; P < 0.001). In contrast, fecal indicator bacteria numbers did not correlate with the presence/absence of opportunistic pathogens tested in this study. Based on the results of this study, it would be prudent, to undertake a Quantitative Microbial Risk Assessment (QMRA) analysis of opportunistic pathogens to determine associated health risks for potable and nonpotable uses of tank water.

Prevalence of enterococcus species and their virulence genes in fresh water prior to and after storm events

Enterococcus spp. isolates (n = 286) collected from six surface water bodies in subtropical Brisbane, Australia, prior to and after storm events, were identified to species level and tested for the presence of seven clinically important virulence genes (VGs). Enterococcus faecalis (48%), Enterococcus faecium (14%), Enterococcus mundtii (13%), and Enterococcus casseliflavus (13%) were frequently detected at all sites. The frequency of E. faecium occurrence increased from 6% in the dry period to 18% after the wet period. The endocarditis antigen (efaA), gelatinase (gelE), collagen-binding protein (ace), and aggregation substance (asa1) were detected in 61%, 43%, 43%, and 23% of Enterococcus isolates, respectively. The chances of occurrence of ace, gelE, efaA, and asa1 genes in E. faecalis were found to be much higher compared to the other Enterococcus spp. The observed odds ratio of occurrence of ace and gelE genes in E. faecalis was much higher at 7.96 and 6.40 times, respectively. The hyl gene was 3.84 times more likely to be detected in E. casseliflavus. The presence of multiple VGs in most of the E. faecalis isolates underscores the importance of E. faecalis as a reservoir of VGs in the fresh water aquatic environment. Consequently, if contaminated surface water is to be used for production of potable and nonpotable water some degree of treatment depending upon intended use such as detention in basins prior to use or chlorination is required.

Development of quantitative PCR assays targeting the 16S rRNA genes of Enterococcus spp. and their application to the identification of enterococcus species in environmental samples

The detection of environmental enterococci has been determined primarily by using culture-based techniques that might exclude some enterococcal species as well as those that are nonculturable. To address this, the relative abundances of enterococci were examined by challenging fecal and water samples against a currently available genus-specific assay (Entero1). To determine the diversity of enterococcal species, 16S rRNA gene-based group-specific quantitative PCR (qPCR) assays were developed and evaluated against eight of the most common environmental enterococcal species. Partial 16S rRNA gene sequences of 439 presumptive environmental enterococcal strains were analyzed to study further the diversity of enterococci and to confirm the specificities of group-specific assays. The group-specific qPCR assays showed relatively high amplification rates with targeted species (>98%), although some assays cross-amplified with nontargeted species (1.3 to 6.5%). The results with the group-specific assays also showed that different enterococcal species co-occurred in most fecal samples. The most abundant enterococci in water and fecal samples were Enterococcus faecalis and Enterococcus faecium, although we identified more water isolates as Enterococcus casseliflavus than as any of the other species. The prevalence of the Entero1 marker was in agreement with the combined number of positive signals determined by the group-specific assays in most fecal samples, except in gull feces. On the other hand, the number of group-specific assay signals was lower in all water samples tested, suggesting that other enterococcal species are present in these samples. While the results highlight the value of genus- and group-specific assays for detecting the major enterococcal groups in environmental water samples, additional studies are needed to determine further the diversity, distributions, and relative abundances of all enterococcal species found in water.

Escherichia coli and Enterococcus spp. in rainwater tank samples: comparison of culture-based methods and 23S rRNA gene quantitative PCR assays

In this study, culture-based methods and quantitative PCR (qPCR) assays were compared with each other for the measurement of Escherichia coli and Enterococcus spp. in water samples collected from rainwater tanks in Southeast Queensland, Australia. Among the 50 rainwater tank samples tested, 26 (52%) and 46 (92%) samples yielded E. coli numbers as measured by EPA Method 1603 and E. coli 23S rRNA gene qPCR assay, respectively. Similarly, 49 (98%) and 47 (94%) samples yielded Enterococcus spp. numbers as measured by EPA Method 1600 and Enterococcus spp. 23S rRNA gene qPCR assay, respectively. The mean E. coli (2.49 ± 0.85) log(10) and Enterococcus spp. (2.72 ± 0.32) log(10) numbers as measured by qPCR assays were significantly (P < 0001) different than E. coli (0.91 ± 0.80) log(10) and Enterococcus spp. (1.86 ± 0.60) log(10) numbers as measured by culture-based method. Weak but significant correlations were observed between both EPA Method 1603 and the E. coli qPCR assay (r = 0.47, P = 0.0009), and EPA Method 1600 and the Enterococcus spp. qPCR assay (r = 0.42, P = 0.002). Good qualitative agreement was found between the culture-based method and the Enterococcus spp. qPCR assay in terms of detecting fecal pollution in water samples from the studied rainwater tanks. More research studies, however, are needed to shed some light on the discrepancies associated with the culture-based methods and qPCR assays for measuring fecal indicator bacteria.