Improved Salmonella recovery from moderate to highly polluted waters

A new enrichment procedure for the recovery of salmonellas from aquatic environments is proposed. It has been tested in a eutrophic lake showing moderate to high faecal contamination levels (the Albufera lake near Valencia, Spain), and in effluents coming into a wastewater treatment plant. The new method consists of the addition of sodium novobiocin to a modification of Rappaport's medium (R10/43°C). The new medium (NR10/43°C) allows a better recovery of salmonellas from water than selenite broth.     

Evaluation of several selective media for recovery of Aeromonas hydrophila from polluted waters

Eleven media were studied for their suitability in the selective isolation of Aeromonas hydrophila. Preliminary results showed that five of them (inositol-brilliant green-bile salts agar, bile salts-brilliant green agar, Rimler-Shotts agar, xylose-sodium deoxycholate-citrate agar, and dextrin-fuchsin-sulfite agar) allowed the growth of several microorganisms that are usually present in the same samples in which A. hydrophila is found. Six media (mA agar, modified Rimler-Shotts agar, DNase-toluidine blue-ampicillin agar, Pril-xylose-ampicillin agar, MacConkey-trehalose agar, and starch-bile salts agar) were selected for evaluation as recovery selective media on the basis of their efficiency in the isolation of A. hydrophila from natural water samples. mA agar showed the best recovery rate and also an acceptable specificity, but its selectivity was low. Another medium that can be considered is DNase-toluidine blue-ampicillin agar, which showed good accuracy, but its specificity was low.     

Evaluation of several selective media for recovery of Aeromonas hydrophila from polluted waters.

Eleven media were studied for their suitability in the selective isolation of Aeromonas hydrophila. Preliminary results showed that five of them (inositol-brilliant green-bile salts agar, bile salts-brilliant green agar, Rimler-Shotts agar, xylose-sodium deoxycholate-citrate agar, and dextrin-fuchsin-sulfite agar) allowed the growth of several microorganisms that are usually present in the same samples in which A. hydrophila is found. Six media (mA agar, modified Rimler-Shotts agar, DNase-toluidine blue-ampicillin agar, Pril-xylose-ampicillin agar, MacConkey-trehalose agar, and starch-bile salts agar) were selected for evaluation as recovery selective media on the basis of their efficiency in the isolation of A. hydrophila from natural water samples. mA agar showed the best recovery rate and also an acceptable specificity, but its selectivity was low. Another medium that can be considered is DNase-toluidine blue-ampicillin agar, which showed good accuracy, but its specificity was low.     

Persistence and diversity of faecal coliform and enterococci populations in faecally polluted waters

Aim: To assess the persistence and diversity of faecal bacterial populations (faecal coliforms and enterococci) that have recently been included in microbial source tracking (MST) predictive models. Methods and Results: The analysed bacterial populations included members of the enterococci group (ENT) [Enterococcus faecium (FM), Enterococcus faecalis (FS) and Enterococcus hirae (HIR)] and the faecal coliform group (FC) [diverse Escherichia coli phenotypes (ECP) and cellobiose‐negative faecal coliforms (CNFC)]. The inactivation of these distinct groups was monitored over time on‐site in river by biochemical fingerprinting, and diversity indices were calculated. Among the different analysed species belonging to the ENT group, HIR persisted longer and was able to replicate in the environment at a higher rate. On the other hand, ECP and NCFC showed a similar persistence throughout the different seasons. The diversity index (Di) for FC increased substantially in the summer after 96 h to a maximum value of 0·96. On the other hand, the Di for ENT diminished over the same period to a value of 0·86, suggesting a different persistence for the different species integrating this group. Conclusions: The persistence of ECP, CNFC, FM and FS in the aquatic environment is high, particularly for the members of the FC and in the summer season. On the contrary, HIR is able to replicate in the environment at a high rate even in winter, and therefore, its inclusion in MST predictive models is discouraged. Significance and Impact of the Study: ECP, CNFC, FMFS and HIR have been proposed as additional variables in MST predictive models. However, the different persistence of HIR compared with the other variables should be taken into account for the development of such models.     

Studies on faecal streptococci in the river Tigris

Six hundred water samples collected from the river Tigris at Mosul City were investigated for faecal streptococci. Human faecal streptococci were predominant, and animal faecal streptococci were also detected. Eight species and varieties were identified, viz Streptococcus faecalis, atypical Streptococcus faecalis, Streptococcus bovis, Streptococcus equinus, Streptococcus faecalis var. liquefaciens, Streptococcus faecalis var. zymogenes, Streptococcus durans and Streptococcus faecium. The incidence of these species and varieties were 43.32%, 13.18%, 11.47%, 11.30%, 9.76%, 5.30%, 3.76% and 1.88%, respectively.     

Chemical methods to detect S-nitrosation

Nitric oxide (NO) is a cell-signaling molecule involved in a number of physiological and pathophysiological processes. Modification of cysteine residues by NO (or NO metabolites), that is S-nitrosation, changes the function of a broad spectrum of proteins. This reaction represents an important post-translational modification that transduces NO-dependent signals. However, the detection and quantification of S-nitrosation in biological samples remain a challenge mainly because of the lability of S-nitrosation products: S-nitrosothiols (SNO). In this review we summarize recent developments of the methods to detect S-nitrosation. Our focus is on the methods which can be used to directly conjugate the site(s) of S-nitrosation.     

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.     

Evaluation of four membrane filter media in anaerobic-MF recovery of faecal coliforms from freshwater in Nigeria

M.T. OGAN. 1992. MacConkey (MC), membrane lauryl sulphate (MIS), membrane faecal coliform amended with rosolic acid (MFC + R) and without the acid (MFC — R) were evaluated in the anaerobic membrane filtration (anaerobic-MF) recovery of faecal coliform populations (FCs), genera and faecal coliform positive (FC-positive) strains isolated from various sources of freshwater, i.e. rivers, rural wells, unchlorinated distributive supplies and hand pumps. Mean counts (x 10²/100 ml) of presumptive (typical) FCs varied from 13.69 (MC) to 40.81 (MLS) in river samples, and from 2.0 (MC) to 4.19 (MFC + R) in wells. The proportion of FC-positive, typical FCs ranged from 48.66 (MIS) to 66.67% (MC) in rivers, and from 50 (MC) to 90.22% (MFC + R) in wells. More than 30% of the typical FCs from all sources on each medium was FC-negative. These usually formed small ( ca 1.0 mm diam.) colonies on the test agar, and were prevalent in wells. Typical FCs and FC-positive strains were not recovered from piped supplies and hand pumps. In spite of anaerobic incubation, non-faecal coliforms (NFCs) were often higher than the FCs; the FC: NFC ratios for rivers ranged from 1.65 (MC) to 7.65 (MLS) and (MFC + R) but were < 1.0 for wells on each medium. Escherichia coli, Klebsiella and Enterobacter species were recovered on all media: approximately 35–64% of the strains confirmed as FCs were E. coli, 20–42% were Kl. pneumoniae. The FC counts on the media were variable, but the overall performance in recovering 'true' FCs was similar; < 70% of strains per medium were FC-positive. None could count E. coli exclusively.     

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 10(2)-10(9) cfu/100 ml and faecal coliforms of between 9-10(7) 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.     

Real-time molecular methods to detect infectious viruses

Waterborne transmitted viruses pose a public health threat due to their stability in aquatic environment and the easy transmission with high morbidity rates at low infectious doses. Two major challenge of virus analysis include a lack of adequate information in infectivity and the inability to cultivate certain epidemiologically important viruses in vitro. The use of fluorescent probes in conjunction with fluorescence microscopy allows us to reveal dynamic interactions of the viruses with different cellular structures in living cells that are impossible to detect by immunological or PCR-based experiments. Real-time viral detection in vivo provides sufficient information regarding multiple steps in infection process at molecular level, which will be valuable for the prevention and control of viral infection.     

Evaluation of four membrane filter media in anaerobic-MF recovery of faecal coliforms from freshwater in Nigeria.

MacConkey (MC), membrane lauryl sulphate (MIS), membrane faecal coliform amended with rosolic acid (MFC + R) and without the acid (MFC - R) were evaluated in the anaerobic membrane filtration (anaerobic-MF) recovery of faecal coliform populations (FCs), genera and faecal coliform positive (FC-positive) strains isolated from various sources of freshwater, i.e., rivers, rural wells, unchlorinated distributive supplies and hand pumps. Mean counts (x 10(2)/100 ml) of presumptive (typical) FCs varied from 13.69 (MC) to 40.81 (MLS) in river samples, and from 2.0 (MC) to 4.19 (MFC + R) in wells. The proportion of FC-positive, typical FCs ranged from 48.66 (MIS) to 66-67% (MC) in rivers, and from 50 (MC) to 90.22% (MFC + R) in wells. More than 30% of the typical FCs from all sources on each medium was FC-negative. These usually formed small (ca 1.0 mm diam.) colonies on the test agar, and were prevalent in wells. Typical FCs and FC-positive strains were not recovered from piped supplies and hand pumps. In spite of anaerobic incubation, non-faecal coliforms (NFCs) were often higher than the FCs; the FC:NFC ratios for rivers ranged from 1.65 (MC) to 7.65 (MLS) and (MFC + R) but were < 1.0 for wells on each medium. Escherichia coli, Klebsiella and Enterobacter species were recovered on all media: approximately 35-64% of the strains confirmed as FCs were E. coli, 20-42% were Kl. pneumoniae. The FC counts on the media were variable, but the overall performance in recovering 'true' FCs was similar; < 70% of strains per medium were FC-positive. None could count E. coli exclusively.