Effects of sunlight and Synechocystis sp. (picocyanobacterium) on the incidence of antibiotic resistance in wastewater enteric bacteria

Experimental study of the effects of sunlight and Synechocystis sp. (picocyanobacterium) on the incidence of antibiotic resistance in Salmonella sp. and faecal coliforms (FC), was carried out in wastewaters of Marrakesh stabilization ponds (Morocco). The effect of sunlight was found to be important on the incidence of antibiotic resistance of these enteric bacterial populations. In microcosms seeded with the mixed inoculum (40 different strains) of Salmonella or FC and exposed to sunlight, the overall resistance of these bacteria (72.5 and 57.5% respectively) was significantly higher than that noted in the dark (45 and 32.5% respectively). In microcosms seeded with a monobacterial inoculum, some FC isolates became resistant to the antibiotics cephalothin, amoxicillin or sulphamethoxazole, after their incubation in sunlight. Synechocystis appeared to have no significant effect on the incidence of bacterial antibiotic resistance. The ecological significance of sunlight and Synechocystis sp. in reducing densities and increasing antibiotic resistance of pathogenic bacteria through wastewater stabilization ponds is discussed.     

Prevalence of Salmonella serotypes in environmental waters and their relationships with indicator organisms

The incidence of serotypes of Salmonella in three types of environmental water (sea, river and fresh reservoirs) from north-east Spain was investigated. The study was performed at specific sampling locations during the summer for a period of five years (1992–1996). A total of 823 strains were isolated and 55 different serotypes were identified, 42 were recovered from sea water, 32 from river water and 12 from freshwater reservoirs. The most frequently isolated serotypes coincided with those involved in clinical cases in the area studied. Salmonella enteritidis was the most common (111 isolates), it was found in all types of water, although most predominantly in sea water (16.1% of the isolates). This serotype, together with S. hadar, significantly increased in frequency during the five year study period. The most frequent serotypes in river water and freshwater reservoirs were S. virchow (9.5%) and S. mikawasima (23.8%) respectively. Significant differences were assessed in the indicator organism densities between the samples with serotypes of clinical significance (S. enteritidis, S. infantis, S. typhimurium, S. virchow and S. paratyphi B) and those without clinical significance. Therefore their presence in all environmental waters may be of epidemiological significance.     

Faecal microbial biomarkers in early diagnosis of colorectal cancer

Colorectal cancer (CRC) is ranked as the second most common cause of cancer deaths and the third most common cancer globally. It has been described as a ‘silent disease’ which is often easily treatable if detected early—before progression to carcinoma. Colonoscopy, which is the gold standard for diagnosis is not only expensive but is also an invasive diagnostic procedure, thus, effective and non-invasive diagnostic methods are urgently needed. Unfortunately, the current methods are not sensitive and specific enough in detecting adenomas and early colorectal neoplasia, hampering treatment and consequently, survival rates. Studies have shown that imbalances in such a relationship which renders the gut microbiota in a dysbiotic state are implicated in the development of adenomas ultimately resulting in CRC. The differences found in the makeup and diversity of the gut microbiota of healthy individuals relative to CRC patients have in recent times gained attention as potential biomarkers in early non-invasive diagnosis of CRC, with promising sensitivity, specificity and even cost-effectiveness. This review summarizes recent studies in the application of these microbiota biomarkers in early CRC diagnosis, limitations encountered in the area of the faecal microbiota studies as biomarkers for CRC, and future research exploits that address these limitations.     

Microbial population dynamics in the faeces of wood‐eating loricariid catfishes

Catfishes of the genus Panaque are known for their ability to feed on wood and hence to process cellulose fibres in their digestive systems. The paper industry uses cellulose fibres and thus has an interest in exploiting this property biomimetically: it could be employed as a pretreatment to lessen the energy required by the mechanical production stage of manufacturing nanocellulose fibres. Here, we characterize the diet‐associated in situ microbial diversity and population dynamic in the faeces of catfish (Panaque sp.) exposed to consecutive diets of pellet food and then wood. Fish faeces samples were collected and investigated by parallel DNA deep amplicon sequencing of the bacterial 16S rRNA SSU for both diet conditions. The most frequently occurring bacterium in the faeces was Cetobacterium sp. The dominant cellulolytic bacterial genera found in ascending relative abundance were as follows: Aeromonas sp., Flavobacterium sp., Bacteroides sp., Pseudomonas sp. and Cellvibrio sp. Diet‐associated changes in the faeces microbiome were noted for Flavobacterium sp. Extensive microbial diversity was found in catfish faeces, evidenced using culture‐independent molecular techniques. No significant diet‐associated effects on the microbiome in terms of biodiversity were observed in the catfish faeces, but diet‐associated changes in the microbial population structure were observed.

Significance and Impact of the Study

Although catfishes are not classified as true xylivores, inhabiting their faeces are bacteria that may provide a novel source of cellulolytic enzyme. Based on this first microbiology study, the faeces and thus the gastrointestinal microbiome of Panaque catfishes are an unexplored reservoir of microbial extracts with enhanced polysaccharide transforming enzyme activity. The biomimetical exploitation of this cellulolytic activity in the form of novel enzymes or by applying a mixture of cellulolytic micro‐organisms could accomplish a pretreatment to the mechanical production process of nanocellulose fibres, thus could reduce the energy consumption costs significantly.     

Occurrence of a human-associated microbial source tracking marker and its relationship with faecal indicator bacteria in an urban estuary

One of the main impacts of urban sprawl in rapidly growing countries has been contamination of coastal environments by waterborne pathogens, posing a critical risk to ecosystem and human health. Microbial source tracking (MST) has been a robust tool to identify the origin of these pathogens globally. This study compared the occurrence of a human-associated Bacteroides marker (BT-α) with faecal indicator bacteria (FIB) in an urban estuary (Golden Horn, Istanbul, Turkey). Faecal coliform (culture method), enterococci (both culture and qPCR method) concentrations and physicochemical variables were compared with the BT-α concentrations in monthly collected samples for a year (n = 108). Enterococci concentrations detected by culture and qPCR were positively correlated (r = 0·86, P < 0·01) suggesting that qPCR can be an alternative method for monitoring. BT-α marker was positive for 30% of the samples and positively correlated with enterococci (r = 0·61 and r = 0·64 for culture and qPCR methods respectively, P < 0·01). Rainfall had a moderate positive correlation with all faecal/MST indicators suggesting combined sewer overflows also severely impacted estuarine water quality. The high FIB and BT-α concentrations at upper estuary suggested that faecal pollution mainly originated from the peri-urban settlements around two creeks entering the estuary.