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Water Treatment and Purification
Published in P.K. Tewari, Advanced Water Technologies, 2020
Bacteria are single-cell prokaryotes (without nucleus) ranging in size from 0.3 to 100 micron (μm) long. Many of these pathogenic bacteria belong to the family Enterobacteriaceae. They include the human pathogen; Salmonella typhi, which is typically present in all kinds of food grown in polluted environments. Another type of bacterium in this family, Yersinia enterocolitica (certain strains) causes acute gastroenteritis with diarrhea. Y. enterocolitic bacteria are present in sewage and fecal-contaminated surface water. A special feature of Y. enterocolitica is their ability to grow even at low temperatures (say 4°C). Therefore, these organisms can survive for long periods in water habitats. Shigella, also part of Enterobacteriaceae, causes dysentery in humans and is usually transmitted through direct contact. Other bacteria species of significance but not part of this family include Vibrio cholerae, specifically the serogroup 01, which causes cholera, an acute intestinal disease with massive diarrhea, vomiting and dehydration, at times leading to death. Some other pathogenic bacteria include campylobacter and opportunistic pathogens such as Legionella pneumophila and aeromonas.
Biological Fundamentals
Published in Roger T. Haug, of Compost Engineering, 2018
A wide variety of pathogenic bacterial, viral, protozoan, and metazoan forms occur in sewage, hence, in sludges of sewage origin and refuse contaminated with fecal matter. However, the types of pathogens present, as well as the concentration, may vary considerably from community to community. Enteric bacterial (Enterobacteriaceae) pathogens include the causative agents for cholera, typhoid and paratyphoid fever, and various dysentery-related diseases. Numerous viruses are excreted by man including poliovirus (3 types), coxsackievirus (25 types), echovirus (25 types), reovirus (3 types), and adenovirus (33 types).14 Even though numerous types are excreted, the only viral disease definitely known to be waterborne is hepatitis A (infectious hepatitis).
Microbiological Hazards
Published in Dag K. Brune, Christer Edling, Occupational Hazards in the Health Professions, 2020
The Gram-negative enteric bacteria belonging to the Enterobacteriaceae family (Escherichia coli, Klebsiella spp., Enterobacter spp., Proteus spp., Citrobacter spp., Serratia spp., etc.) are the etiologic agents of a large proportion of nosocomial infections. They are also a common cause of many community-acquired infections. Despite this, most infectious disease specialists would probably deny that this group of organisms poses a significant risk to health care personnel. There are, however, few studies on this subject, and most of these deal with colonization and not clinical disease. Rahal et al.92 reported that upper respiratory tract carriage of Gram-negative enteric bacilli by hospital personnel was not different from that among personnel without patient contact. Several workers have reported carriage rates of Gram-negative bacilli around 20% on the hands of hospital personnel.93–96 Maki found 44.5% of 348 hand cultures from 25 medical personnel to be positive for Gram-negative bacilli, all 25 being positive at least once during a 4-month period.97 However, studies comparing hand carriage of Gram-negative bacteria have in fact shown significantly lower carriage rates among hospital personnel than among controls without patient contact.96,98,99The reason for this seems to be that medical personnel wash their hands more frequently. The use of handwashing agents with antiseptics was also very common among the hospital personnel in these studies. In general, because of their low virulence, carriage of Gram-negative enteric bacilli on the hands of health care workers is a much larger hazard to their patients than to themselves.
Effects of Ozone Treatment on Microbiological Quality and Physicochemical Properties of Turkey Breast Meat
Published in Ozone: Science & Engineering, 2020
Ufuk Gokce Ayranci, Orhan Ozunlu, Haluk Ergezer, Hakan Karaca
The Enterobacteriaceae counts in ozone-treated and untreated turkey meat samples are shown in Figure 2. It seems that ozone effectively reduced the counts of Enterobacteriaceae in turkey meat samples. Around 1.0–1.5 log reductions were observed after 2 and 4 h treatments. Reductions of 2.3 and 2.0 log were obtained with ozone treatments for 6 and 8 h, respectively, and there was no significant difference between the Enterobacteriaceae counts of the samples from these treatments (p > .05). Accordingly, maximum Enterobacteriaceae reduction was observed after treatment for 6 h and no more reductions were obtained by 8 h treatment. Since ozone has a superficial effect (Tabakoglu and Karaca 2015), our results show that Enterobacteriaceae present on the surface of the samples were inactivated by 6-h treatment and even if ozone treatment was prolonged, ozone could not reach the depths of the meat and did not cause further microbial inactivation. Enterobacteriaceae is a diverse group of bacteria including various human pathogens such as Salmonella, E. coli, Shigella, etc. Raw meat can be contaminated with those bacteria during slaughtering, dressing and evisceration if these operations are not implemented properly. Treatments that are effective in inactivating Enterobacteriaceae are important in order to ensure food safety. In parallel with our results, effectiveness of ozone in inactivating Enterobacteriaceae was reported by other researchers in its gaseous form (Cho et al. 2015; Muhlisin et al. 2016) and also in aqueous form (Pohlman et al. 2002; Stivarius et al. 2002). Novak and Yuan (2003) treated inoculated beef samples with aqueous ozone (3 ppm) for 5 min. They observed 1.28, 0.85 and 1.09 log reductions in the counts of Clostridium perfringens, E. coli O157:H7 and Listeria monocytogenes, respectively. Castillo et al. (2003) sprayed beef surfaces with an aqueous ozone solution containing 95 mg of ozone per liter. They observed that reductions of E. coli O157:H7 and Salmonella serotype typhimurium were not significantly different from those achieved with water was alone.
Biosynthesis of copper nanoparticles using symbiotic bacterium Xenorhabdus sp, isolated from entomopathogenic nematode and its antimicrobial and insecticidal activity against Spodoptera litura
Published in Inorganic and Nano-Metal Chemistry, 2022
Balasubbiramaniyan Guru Bharathi, Kandhasamy Lalitha, Muthugounder Subramanian Shivakumar
Spodoptera litura is an important lepidopteran agricultural pest.[1] It is polyphagous and feeds on several types of crop plants,[2] which include tobacco, groundnut, chilies, cole crops, sunflower and cotton.[3] Chemical pesticides are used for reducing the damage caused by insect pests to crops.[4] Despite many benefits of synthetic pesticides, there are several undesirable effect on human health and environment.[5] Their extensive has resulted in development of insecticide resistance among insects S. litura.[6] Use of biopesticides of biological origin are thought to very important in pest control. Biopesticides developed from living organisms like plants, animals, and microorganisms such as bacteria, fungi, virus, protozoa and nematodes are mainly used to control pest in the field of agriculture.[7] Entomopathogenic nematodes are naturally present in soil in large numbers. Bacterial metabolites are obligate parasites which infect and kill insects.[8,9] Entomopathogenic nematodes (EPNs) from Steinernematidae and Heterorhabditidae families are used as biopesticides for insect control.[10] Bacteria from Xenorhabdus and Photorhabdus genera have mutualistic relationship with Steinernematids and Heterorhabditidae nematodes respectively.[9]Xenorhabdus sp. is a gram-negative bacteria belonging to the Enterobacteriaceae family. It exist in symbiotic relationship with the EPN Steinernema spp. They are widely associated with insect pathogenecity following infections with EPNs.[10]Xenorhabdus sp, are known to be highly effective in causing pathological conditions in host. This leads to host insect mortality, the insect mortality is thoughts to be caused by toxic metabolites produced by Xenorhabdus sp., hence in the present study Xenorhabdus sp., was used.