Microbiological Quality and Genotypic Speciation of Heterotrophic Bacteria Isolated from Potable Water Stored in Household Tanks

Abstract Upon storage, a statistically significant increase in heterotrophic plate count (HPC) was detected in samples from household tanks. The most consistent correlate of regrowth was found to be storage time, however, temperature and the microbiological quality of the influent water were also important. Total and fecal coliforms were detected in the influent water and in the household storage tanks. Coliforms growing at 37°C were a small but significant part (about 0.002%) of the total heterotrophic population. In the influent, 92% of the coliforms (11 colony forming units/100 mL) at 44°C were Escherichia coli, while in the household tanks it was 86%. The majority of isolates from the influent and the household tanks recovered on R2A agar formed pigmented colonies and were Gram-negative belonging to the α-, β-, and γ-subclasses of Proteobacteria. Overall, the α-subclass was the dominant type representing 61% of the recovered HPC, and 40 to 50% of the organisms based on 16S rDNA sequence analysis were members of the family Sphingomonadaceae. The presence of E. coli and the isolation of opportunistic pathogens as a significant part of the HPC population from both influent and household tanks indicated a potential health hazard to consumers.</jats:p

Phenotypic and genotypic identification of Aeromonas spp. isolated from a chlorinated intermittent water distribution system in Lebanon

Aeromonas spp. were detected in samples collected from both untreated groundwater and treated drinking water in Lebanon. Aeromonas spp. levels ranged between 2 and 1,100 colonies per 100 ml in the intake underground well and between 3 and 43 colonies per 100 ml in samples from the distribution system. Samples positive for Aeromonas spp. from the network had a free chlorine level ranging between 0 and 0.4 mg l −1. Multiple antibiotic-resistance was common among the isolated aeromonads; all were resistant to amoxycillin while 92% showed resistance to cephalexin. Haemolysis on blood agar was detected in 52% of the isolates recovered from the distribution network and 81% of isolates from the untreated underground source. The Biolog microbial identification system assigned identities to all of the isolated presumptive aeromonads (at least at the genus level), which was not the case with the API 20NE strips. Differences at the species level were observed when results from the Biolog system were compared with identification based on the MicroSeq 500 16S rDNA sequence analysis. The presence of Aeromonas spp. in drinking water can be an important threat to public health, thus greater awareness of Aeromonas strains as potential enteropathogens is warranted.</jats:p

Identification of Sphingomonads on the Basis of Polymerase Chain Reaction Amplified 16S rRNA Gene

Abstract Sphingomonas is a genus that is basically of environmental origin but can also be associated with health hazards, especially in the hospital environment where there is a great need to properly monitor water sources. The abundance and frequent isolation of derivatives of yellow pigmented colonies from drinking water samples in Lebanon—where an intermittent mode of supply is employed, and which induces frequent biofilm sloughing—necessitated the establishment of a rapid and feasible assay to screen specifically for sphingomonads. In this study, 50 isolates recovered from drinking water with yellow- to orange-pigmented colonies were used to establish a polymerase chain reaction-based (PCR-based) screening assay. The use of sphingomonad specific modified primers gave one common band with a size of 320 bp in all resumptive and sequence confirmed sphingomonads. However, no amplification was observed with Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa. Applying the PCR-based assay described in this paper increased both the efficiency and the reliability of screening for sphingomonads in water samples, thereby minimizing related risk factors.</jats:p

Use of the 16S-23S ribosomal genes spacer region for the molecular typing of sphingomonads

The ability of sphingomonads in drinking water to cause community- and hospital-acquired opportunistic infections has raised the need to establish reproducible identification assays. In this study, a total of 129 isolates recovered from drinking water with yellow- to orange-pigmented colonies were distributed among 10 biotypes on the basis of colony morphology. Polymorphisms, based on the amplification and restriction digestion of the intergenic transcribed spacer (ITS) region within the 10 assigned biotypes and 18 ATCC reference strains, were used to investigate the ability of this approach to differentiate closely related sphingomonads. ITS size, which ranged between 400 and 1100 bp, did not vary enough among the different genera. However, 16 distinct banding patterns within the ATCC reference strains and 9 within the 10 biotypes were obtained through ITS restriction digestion, and the majority of the tested biotypes produced patterns similar to those generated by the ATCC strains. To our knowledge, this study is not only the first comprehensive record of the size of the ITS region in sphingomonads, it is also the first study that describes the use of ITS restriction digestion to subtype those isolates

emm typing, antibiotic resistance and PFGE analysis of Streptococcus pyogenes in Lebanon

One hundred and threeStreptococcus pyogenesisolates recovered mainly from streptococcal throat infections in Lebanon were characterized byemmand PFGE typing. Thirty-threeemmtypes and subtypes were detected among the isolates. PFGE was more discriminatory as a typing method. The prevalentemmtypes wereemm1(12.6 %),emm22(8.7 %),emm28(7.7 %),emm88(7.7 %) andemm4(6.8 %) and all isolates were susceptible to vancomycin and penicillin G. Ten per cent of the isolates were resistant to erythromycin and 3 % were resistant to erythromycin and clindamycin, showing the macrolide–lincosamide–streptogramin B phenotype. Theemmsequences and PFGE pattern database that were generated in this study will serve as a basis for information for long-term evolutionary and epidemiological studies of localS. pyogenesrecovered not only in Lebanon, but also in neighbouring countries.</jats:p

Sulfate assimilation in Rhodopseudomonas globiformis

Rhodopseudomonas globiformis is able to grow on sulfate as sole source of sulfur, but only at concentrations below 1 mM. Good growth was observed with thiosulfate, cysteine or methionine as sulfur sources. Tetrathionate supported slow growth. Sulfide and sulfite were growth inhibitory. Growth inhibition by higher sulfate concentrations was overcome by the addition of O-acetylserine, which is known as derepressor of sulfate-assimilating enzymes, and by reduced glutathione. All enzymes of the sulfate assimilation pathway. ATP-sulfurylase, adenylylphosphate-sulfotransferase, thiosulfonate reductase and O-acetylserine sulfhydrylase are present in R. globiformis. Sulfate was taken up by the cells and the sulfur incorporated into the amino acids cysteine, methionine and homocysteine. It is concluded, that the failure of R. globiformis to grow on higher concentrations of sulfate is caused by disregulation of the sulfate assimilation pathway. Some preliminary evidence for this view is given in comparing the activities of some of the involved enzymes after growth on different sulfur sources and by examining the effect of O-acetylserine on these activities

Geographical Structure of the Y-chromosomal Genetic Landscape of the Levant: A coastal-inland contrast

We have examined the male-specific phylogeography of the Levant and its surroundings by analyzing Y-chromosomal haplogroup distributions using 5874 samples (885 new) from 23 countries. The diversity within some of these haplogroups was also examined. The Levantine populations showed clustering in SNP and STR analyses when considered against a broad Middle-East and North African background. However, we also found a coastal-inland, east-west pattern of diversity and frequency distribution in several haplogroups within the small region of the Levant. Since estimates of effective population size are similar in the two regions, this strong pattern is likely to have arisen mainly from differential migrations, with different lineages introduced from the east and west