Competition for hydrogen between sulphate-reducing bacteria and methanogenic bacteria from the human large intestine

Sulphate-reducing activity in human faecal slurries was followed by measuring sulphide production. Sulphate-reducing bacteria (SRB) were found to outcompete methanogenic bacteria (MB) for the mutual substrate hydrogen in faecal slurries from methane- and non-methane-producing individuals mixed together. When molybdate (20 mmol/l) was added to these slurries, sulphate reduction was inhibited and methanogenesis became the major route of electron disposal. Sulphide production was stimulated by the addition of 20 mmol/l sulphate in non-methanogenic but not in methanogenic slurries. In methanogenic slurries that contained the methanogen inhibitor 2-bromoethanesulphonic acid (BES), hydrogen accumulated whilst sulphide levels were unaffected, confirming the absence of SRB in methanogenic faeces. The addition of nitrate (10 mmol/l) to faecal slurries completely inhibited methanogenesis but only slightly reduced sulphate reduction. The sulphated mucopolysaccharides, chondroitin sulphate and mucin, strongly stimulated sulphide production in non-methanogenic faecal slurries only, suggesting that these substances may be a potential source of sulphate in the large gut.     

Competition for hydrogen between sulphate-reducing bacteria and methanogenic bacteria from the human large intestine

Sulphate-reducing activity in human faecal slurries was followed by measuring sulphide production. Sulphate-reducing bacteria (SRB) were found to outcompete methanogenic bacteria (MB) for the mutual substrate hydrogen in faecal slurries from methane- and non-methane-producing individuals mixed together. When molybdate (20mmol/l) was added to these slurries, sulphate reduction was inhibited and methanogenesis became the major route of electron disposal. Sulphide production was stimulated by the addition of 20 mmol/1 sulphate in non-methanogenic but not in methanogenic slurries. In methanogenic slurries that contained the methanogen inhibitor 2-bromoethanesulphonic acid (BES), hydrogen accumulated whilst sulphide levels were unaffected, confirming the absence of SRB in methanogenic faeces. The addition of nitrate (10 mmol/l) to faecal slurries completely inhibited methanogenesis but only slightly reduced sulphate reduction. The sulphated mucopolysaccharides, chondroitin sulphate and mucin, strongly stimulated sulphide production in non-methanogenic faecal slurries only, suggesting that these substances may be a potential source of sulphate in the large gut.     

Biodegradation of the synthetic pyrethroid cypermethrin in used sheep dip

AIMS: To investigate the breakdown of cypermethrin synthetic pyrethroid (SP) insecticide-based used sheep dip (USD), with its indigenous microbial community and two previously isolated SP-degrading microorganisms. METHODS AND RESULTS: Cultures of USD (50 ml) containing 250 ml l(-1) cypermethrin were inoculated with the SP-degrading organisms and incubated at 25 degrees C with agitation at 80 rev min(-1) for 14 days. The viable cell counts and concentration of cypermethrin were monitored. A non-stimulated control was also carried out. The previously isolated bacteria were the most effective at degrading cypermethrin, leaving approximately two-thirds the concentration of SP as was found in the control. The non-stimulated cultures showed negligible breakdown of SP over the experimental period. CONCLUSIONS: The previously isolated SP-degrading bacteria could have a use in the treatment of SP USD. SIGNIFICANCE AND IMPACT OF STUDY: In situ treatment of SP-based USDs to detoxify the active ingredient before disposal could be very useful in helping to deal with agricultural pesticide waste. Such an approach, or by ex situ treatment would be more preferable to current methods, such as those of incineration and disposal to land.     

Eugenol stimulates lactate accumulation yet inhibits volatile fatty acid production and eliminates coliform bacteria in cattle and swine waste

AIM: To determine how eugenol affects fermentation parameters and faecal coliforms in cattle and swine waste slurries stored anaerobically. METHODS AND RESULTS: Waste slurries (faeces:urine:water, 50:35:15) were blended with and without additives and aliquoted to triplicate 1-l flasks. Faecal coliforms were eliminated in cattle and swine waste slurries within 1 or 2 days with additions of eugenol at 10.05 mm (0.15%) and 16.75 mm (0.25%). At these concentrations volatile fatty acids (VFA) were reduced ca 70 and 50% in cattle and swine waste, respectively, over 6-8 weeks. Additionally, in cattle waste, eugenol stimulated the accumulation of lactate (>180 mm) when compared with thymol treatment (20 mm lactate). In swine waste, lactate accumulation did not occur without additives; eugenol and thymol stimulated lactate accumulation to concentrations of 22 and 32 mm, respectively. CONCLUSIONS: Eugenol added to cattle waste may be more beneficial than thymol because not only does it effectively control faecal coliforms and odour (VFA production), it also stimulates lactate accumulation. This in turn, causes the pH to drop more rapidly, further inhibiting microbial activity and nutrient emissions. SIGNIFICANCE AND IMPACT OF THE STUDY: Plant essential oils have the potential to solve some of the environmental problems associated with consolidated animal feeding operations. Thymol and eugenol reduce fermentative activity, thus, have the potential to reduce emissions of greenhouse gases and odour, and curtail transmission of pathogens in cattle and swine wastes.     

Reduction of indicator and pathogenic microorganisms by psychrophilic anaerobic digestion in swine slurries

The objective of this study was to evaluate the efficiency of a low temperature anaerobic treatment to reduce viable populations of indicator microorganisms (total coliforms, Escherichia coli) and the presence of selected pathogens (Salmonella, Yersinia enterocolitica, Cryptosporidium and Giardia) in swine slurries from different sources. Experiments were carried out in 40 l Sequencing Batch Reactors (SBRs). Experimental results indicated that anaerobic digestion of swine manure slurry at 20 degrees C for 20 days in an intermittently fed SBR: (1) reduced indigenous populations of total coliforms by 97.94-100%; (2) reduced indigenous populations of E. coli by 99.67-100%; (3) resulted in undetectable levels of indigenous strains of Salmonella, Cryptosporidium, and Giardia. It can be considered as a promising method for reducing indigenous indicator and pathogenic microorganisms populations in liquid swine manure slurries.     

Isolation of faecal coliform bacteria from the American alligator (Alligator mississippiensis)

Aims: To determine whether American alligators (Alligator mississippiensis) are an unrecognized poikilothermic source of faecal coliform and/or potential pathogenic bacteria in South Carolina’s coastal waters. Methods and Results: Bacteria from the cloaca of American alligators, as well as bacteria from surface water samples from their aquatic habitat, were isolated and identified. The predominant enteric bacteria identified from alligator samples using biochemical tests included Aeromonas hydrophila, Citrobacter braakii, Edwardsiella tarda, Escherichia coli, Enterobacter cloacae, Plesiomonas shigelloides and putative Salmonella, and these were similar to bacteria isolated from the surface waters in which the alligators inhabited. Based on most‐probable‐number enumeration estimates from captive alligator faeces, faecal coliform bacteria numbered 8·0 × 10⁹ g^?1 (wet weight) of alligator faecal material, a much higher concentration than many other documented endothermic animal sources. Conclusions: A prevalence of enteric bacteria, both faecal coliforms and potential pathogens, was observed in American alligators. The high faecal coliform bacterial density of alligator faeces may suggest that alligators are a potential source of bacterial contamination in South Carolina coastal waters. Significance and Impact of the Study: These findings help to increase our understanding of faecal coliform and potential pathogenic bacteria from poikilothermic reptilian sources, as there is the potential for these sources to raise bacterial water quality levels above regulatory thresholds.     

The effect of a sewage treatment plant effluent on the faecal coliforms and enterococci populations of the reception river waters

AIMS: A rural sewage treatment plant and the effect of its effluent on the enterococci and faecal coliforms populations of the receiving river waters was evaluated. METHODS AND RESULTS: The enumeration of bacteria was performed by membrane filtration. Diversity and population similarity were analysed using the PhP-plates system. The treatment plant reduces the number of enterococci and faecal coliforms to values similar to those observed upstream. All water samples showed a high diversity for both bacterial populations. A high similarity in the composition and structure, was detected among all the samples. CONCLUSIONS: The impact of the disposal of treated sewage on the river did not modify the composition of either bacterial populations in the river water. SIGNIFICANCE AND IMAPCT OF THE STUDY: The biochemical phenotyping of bacterial populations is a reliable tool for ecological and biodiversity studies. The obtained results provide a better understanding of the sewage treatment process and the impact of the treated sewage effluents in the environment.     

Comparison of composting, storage and urea treatment for sanitising of faecal matter and manure

To close the loop of nutrients in a safe way, the loop of pathogens has to be broken. By sanitising organic fertilisers derived from faeces and manure, the first step in the disease transmission chain is broken. Two alternatives for this treatment, thermophilic composting and ammonia-based treatment, were evaluated and compared to storage treatment. Thermal composting of faecal matter and food waste resulted in a treatment temperature of over 65 degrees C in a 90 L reactor. By using insulation and turning the compost three times during the high temperature period, it is possible to ensure a 5 log(10) reduction of pathogens. Small scale composting of the same material indicated less efficient reduction of faecal bacteria at temperatures around 50 degrees C. In the chemical treatment tested, an addition of 3% N-NH(3) increased the pH to above 9 within 1h and resulted in a good reduction in the indicator organisms for bacteria (Salmonella spp. and faecal coliforms D(r)<0.7 days, Enterococcus spp. D(r)<3 days). Lower addition rates resulted in a longer treatment period needed. The storage period tested resulted in slow reduction of faecal coliforms, Salmonella spp. and Enterococcus spp.     

The Effect of Cadmium on Indicator Bacteria in Sewage

The effect of cadmium (Cd) on the number of different faecal indicator bacteria in sewage, and on species composition of different indicator bacteria, was studied. Different amounts of Cd were added to aliquots of a sewage sample, and after 0, 4% and 24 h of Cd exposure at 20°C conforms, faecal coliforms, faecal streptococci and Clostridium perfringens were enumerated by the membrane filter method. The Cd-induced reduction in the number of coliforms and faecal coliforms during exposure was found to be greater than the decrease in the number of faecal streptococci. In the case of C. perfringens the Cd concentrations used produced no observable effect on the cell number. The addition of Cd changed the faecal coliforms and faecal streptococci density relationship. Escherichia coli seems to be more resistant to Cd than other coliforms and Streptococcus faecalis var. liquefaciens and Streptococcus durans more resistant to Cd than other faecal streptococci. No influence of Cd on gas production by faecal coliforms was observed. Faecal streptococci and C. perfringens seem to be better indicator bacteria than coliforms and faecal coliforms in evaluating the hygienic quality of Cd polluted sewage.     

Salmonella in animal slurry can be destroyed by aeration at low temperatures

Cattle and other animals infected by Salmonella can emit high numbers of these bacteria. To determine an effective means for reducing this bacterial group in animal slurry, samples were subjected to aeration in laboratory experiments and in farm-scale slurry tanks. A clear reduction in Salmonella levels was found in laboratory experiments at temperatures from 4 to 40 °C. Aeration in farm-scale slurry tanks increased the temperature above the ambient temperatures (often less than 0 °C) to maxima ranging between 19 and 40 °C. Farm-scale aeration resulted in similar reductions in Salmonella as those achieved in laboratory experiments. Thus, reductions, ranging from greater than 99% of the initial number to no detectable Salmonella , could be reached after 2–5 weeks using aeration processes with cattle slurries contaminated by Salm. infantis or pig slurry contaminated by Salm. typhimurium . These results suggest that farmers can control the spread of Salmonella from slurry to agricultural fields. The reduction mechanisms remain unknown, though the increase in pH (to 7·6–9·0) found in slurries after aeration might exert a decreasing effect on these bacteria.     

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.     

Effects of chilling on sampling of bacteria attached to swine carcasses

Two microbiological sampling techniques, excision and sponge swabbing, were compared by determining counts of aerobic bacteria, coliforms and injured coliforms from 20 de-haired swine carcasses before and after chilling. Excised jowl skin produced significantly greater counts of the three types of bacteria than sponge swabs. Aerobic bacteria, coliforms and injured coliforms recovered by sponge swabbing carcasses before chilling were 11.6%, 0.9% and 11.0% of excised samples, respectively; the corresponding percentages recovered after chilling were 23.9%, 11.1% and 5.0%. Numbers of all bacteria present on the post-chill carcasses were substantially lower than on the pre-chill carcasses. Excision usually produced more countable plates for coliforms and injured coliforms on chilled carcasses than sponge swabbing and therefore, is more suitable in estimating low numbers of faecal bacteria on chilled carcasses. To explore the possible structural bases for these findings, skin samples were inoculated with 10(2)-10(7) cfu cm(-2) faecal bacteria and examined by scanning electron microscopy. Chilled samples showed bacteria and biofilm embedded in superficial crevices, which underlies a possible reason for the lower recovery of bacterial cells by the sponge swabbing. The study indicates that the differences between sampling techniques may be a result of the chilling process of swine carcasses.     

The significance of testing for Pseudomonas aeruginosa in recreational seawater beaches.

The occurrence of Pseudomonas aeruginosa and faecal coliforms in Mediterranean sea water from beaches was investigated. Water samples (1,598 in toto) were tested and P. aeruginosa was found in 222 samples (14%). In 31% of samples where P. aeruginosa was detected, faecal coliforms of less than ten bacteria per 100 ml were found. In a group of 98 samples which had > 500 faecal coliforms per 100 ml, 41% had no detectable P. aeruginosa. The inclusion of P. aeruginosa as an additional parameter for approving beaches for recreational activity is recommended.     

Increased frequency of drug-resistant bacteria and fecal coliforms in an Indiana Creek adjacent to farmland amended with treated sludge

Many studies indicate the presence of human pathogens and drug-resistant bacteria in treated sewage sludge. Since one of the main methods of treated sewage disposal is by application to agricultural land, the presence of these organisms is of concern to human health. The goal of this study was to determine whether the frequency of drug-resistant and indicator bacteria in Sugar Creek, which is used for recreational purposes, was influenced by proximity to a farmland routinely amended with treated sludge (site E). Surface water from 3 sites along Sugar Creek (site E, 1 upstream site (site C) and 1 downstream site (site K)) were tested for the presence of ampicillin-resistant (Amp(R)) bacteria, fecal and total coliforms over a period of 40 d. Site E consistently had higher frequencies of Amp(R) bacteria and fecal coliforms compared with the other 2 sites. All of the tested Amp(R) isolates were resistant to at least 1 other antibiotic. However, no isolate was resistant to more than 4 classes of antimicrobials. These results suggest that surface runoff from the farmland is strongly correlated with higher incidence of Amp(R) and fecal coliforms at site E.     

Microbial characterization during composting of municipal solid waste

This study investigates the prevailing physico-chemical conditions and microbial community; mesophilic bacteria, yeasts and filamentous fungi, bacterial spores, Salmonella and Shigella as well as faecal indicator bacteria: total coliforms, faecal coliforms and faecal Streptococci, present in a compost of municipal solid waste. Investigations were conducted in a semi-industrial pilot plant using a moderate aeration during the composting process. Our results showed that: (i) auto-sterilization induced by relatively high temperatures (60–55°C) caused a significant change in bacterial communities. For instance, Escherichia coli and faecal Streptococci populations decreased, respectively, from 2×10⁷ to 3.1×10³ and 10⁷ to 1.5×10³ cells/g waste dry weight (WDW); yeasts and filamentous fungi decreased from 4.5×10⁶ to 2.6×10³ cells/g WDW and mesophilic bacteria were reduced from 5.8×10⁹ to 1.8×10⁷ bacteria/g WDW. On the other hand, the number of bacterial spores increased at the beginning of the composting process, but after the third week their number decreased notably; (ii) Salmonella disappeared completely from compost by the 25th day as soon as the temperature reached 60°C; and (iii) the bacterial population increased gradually during the cooling phase. While Staphylococci seemed to be the dominant bacteria during the mesophilic phase and at the beginning of the thermophilic phase, bacilli predominated during the remainder of the composting cycle. The appearance of gram-negative rods (opportunistic pathogens) during the cooling phase may represent a serious risk for the sanitary quality of the finished product intended for agronomic reuse. Compost sonication for about 3 min induced the inactivation of delicate bacteria, in particular gram-negatives. By contrast, gram-positive bacteria, especially micrococcus, spores of bacilli, and fungal propagules survived, and reached high concentrations in the compost.     

A multiple logistic model for predicting the occurrence of Campylobacter jejuni and Campylobacter coli in water

A multiple logistic regression model was established to predict the occurrence of Campylobacter jejuni/coli , related to index bacteria such as faecal coliforms, faecal streptococci, and sulphite-reducing clostridia, in a water source in southern Norway. The fitted model indicated that faecal coliforms were strong predictors for C. jejuni/coli , although the water temperature also had a strong influence on results. Sulphite-reducing clostridia, faecal streptococci, and season of the year had no significant influence on the results, in spite of their apparent predictor value as separate variables. The model employed offers a new approach to the relationship between index bacteria and the occurrence of pathogenic bacteria in water. Similar models can also be established in general food microbiology.     

A multiple logistic model for predicting the occurrence of Campylobacter jejuni and Campylobacter coli in water.

A multiple logistic regression model was established to predict the occurrence of Campylobacter jejuni/coli, related to index bacteria such as faecal coliforms, faecal streptococci, and sulphite-reducing clostridia, in a water source in southern Norway. The fitted model indicated that faecal coliforms were strong predictors for C. jejuni/coli, although the water temperature also had a strong influence on results. Sulphite-reducing clostridia, faecal streptococci, and season of the year had no significant influence on the results, in spite of their apparent predictor value as separate variables. The model employed offers a new approach to the relationship between index bacteria and the occurrence of pathogenic bacteria in water. Similar models can also be established in general food microbiology.     

The microbiological quality of drinking water sold on the streets in Kumasi,Ghana

AIM: The aim of this study was to assess the microbiological quality of Ghanaian bottled and plastic-bagged drinking water sold on the streets of Metropolitan Kumasi, Ghana. METHODS AND RESULTS: Eight bottled, 88 factory-filled plastic sachet and 40 hand-filled hand-tied polythene-bagged drinking waters were examined for the presence of heterotrophic bacteria total viable counts (TVCs), indicators of faecal contamination (total coliforms, faecal coliforms and enterococci) and for lead, manganese and iron. Heterotrophic bacteria were found in all three types of water with TVCs per millilitre ranging from 1 to 460 for bottled water, 2-6.33 x 10(5) for factory-bagged sachet water and 2.33 x 10(3)-7.33 x 10(12) for hand-filled hand-tied bagged water. None of the microbial indicators of faecal contamination were detected in bottled water, whereas 4.5% of the factory-bagged sachets contained total coliforms and 2.3% faecal coliforms, and 42.5% of the hand-filled hand-tied bags contained total coliforms, 22.5% faecal coliforms and 5% enterococci. Iron was found in all three types of drinking water but at concentrations well within the WHO recommendations. Lead and manganese were not detected. CONCLUSION: Ghanaian bottled water is of good microbiological quality but some factory-bagged sachet and hand-filled hand-tied polythene-bagged drinking water are of doubtful quality. SIGNIFICANCE AND IMPACT OF THE STUDY: Factory-bagged sachets and hand-filled hand-tied bags of drinking water sold in Ghana should be monitored for microbiological contamination, with the aim of raising standards in the industry and re-assuring the public.     

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.     

In situ determination of slurry nutrient content by electrical conductivity

Land application of animal slurries has both agronomic and environmental implications. It can be supported by the quantification of available nutrients in the field. A prototype device for indirect measurement of the nutrient content of slurry based on electrical conductivity (EC) was calibrated on manure samples collected from farms with different livestock typologies. The resulting correlations between EC and nutrient contents of slurries from laboratory analyses have shown good agreement (r(2) from 0.73 to 0.95) with total and ammoniacal nitrogen and, with some exception, Potassium, but failed to demonstrate any significant relationship with total phosphorous. The mean errors obtained using the device in field conditions for nitrogen content were always lower or equal to 10%, while the standard deviations were 12-13% for pig and calf slurries, and 20-21% for dairy cow slurry. The results obtained suggest that the equipment, provided the regression line used to convert EC readings to nutrient contents is related to the livestock typology under observation, can provide good support to practical slurry spreading, even though it does not reach an accuracy comparable to laboratory methods and does not give reliable information on phosphorus.