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With the exception of the Streptococcus anginosus group order 200mg red viagra with amex, they generally possess little invasive potential (8) buy red viagra discount. Instead 200mg red viagra for sale, they are able to adhere to and promote the growth of the fibrin/platelet thrombus discount 200mg red viagra visa. They do so by their ability to stimulate local production of tissue factor by monocytes and to promote platelet aggregation. Examples require nutritionally variant streptococci variant streptococci) active forms of vitamin B6 for growth. Characteristically produce large valvular vegetations with a high rate of embolization and relapse. Groups A, C, G streptococci More frequently seen in the elderly (nursing homes) and diabetics. Cases usually require the combination of ampicillin and gentamicin, with or without surgery, for cure. They are very invasive and abscess producing in both myocardium and valvular structures. Its mortality rate may be as high as 40% due to metastatic infection, severe valvular damage, and congestive heart failure. The silaic acid component of its capsule is a major virulence factor that inhibits the activation of the alternative complement pathway (14–16, 16a). Its connection with chronic liver disease has been more recently appreciated (21) Most isolates are quite sensitive to penicillin (22). The teichoic acid component of the cell wall facilitates its attachment to the nasal mucosa from which it may set up a “beachhead” on the skin of the patient. Any break in the dermis promotes the entry for the staphylococcus into the microcirculation. Most notable among these are fibronectin-binding proteins and various clumping factors. Staphylococci may remain dormant within the endothelial Infective Endocarditis and Its Mimics in Critical Care 221 cells but are eventually released back into the circulation. Once this pathogen is in the bloodstream, it makes effective use of its unique abilities to invade the endothelium and propagate the platelet fibrin thrombus (27–30). It resides on the skin of both the healthy and the ill as well as being colonizer of the nares. Among these are protein A; catalase; alpha, beta, and gamma toxins; leukocidins and its capsule. Upon the death of the white cell, the viable staphylococci are deposited into the surrounding tissue or return to the intravascular space. It also possesses a superb ability to infect prosthetic devices of all kinds including intravascular devices/catheters by means of its production of the glycocalix biofilm. This environment protects the organisms from the host’s defenses as well as from most antimicrobial agents (32). It is quite difficult for the clinical laboratory to differentiate them from other coagulase-negative organisms. Pseudomonas aeruginosa adheres to the endothelium the most effectively of any of the gram-negative rods. It elaborates several virulence factors, extracellular proteases, elastase alkaline proteases. These produce necrosis in a range of tissues especially in the elastic layer of the lamina propria of all caliber is the blood vessels. These toxins also disrupt the function of polymorphonuclear leukocytes, K- and T-cells, as well as the structure of complement and immunoglobulins. Exotoxin A disrupts protein synthesis and is the factor that is best correlated with systemic toxicity and mortality. Its polysaccharide capsule interferes with phagocytosis and the antibacterial effect of the aminoglycosides (35,36). These are genetically unrelated gram-negative bacilli/cocobacilli that share the oropharynx as the primary site of residence. They usually produce subacute disease that is notable for its massive arterial emboli (40). Most often, these infections are ventilator or intravascular catheter associated (43). What makes their treatment so difficult is the multiplicity of their defensive mechanisms that make them resistant to many classes of antibiotics. Risk factors for its development include exposure to broad-spectrum antibiotics and to cytotoxic agents (46). They enter the bloodstream from the injection site directly or from contamination of the drug paraphernalia (38). This rate may be higher in some areas in the world in which hard to grow organisms, such as Coxiella burnetti, are fairly common. The reason for so doing is well expressed by Friedland, “nosocomial endocarditis occurs in a definable subpopulation of hospitalized patients and is potentially preventable. It is defined as a valvular infection that presents either 48 hours after an individual has been hospitalized or one that is associated with a health-care facility procedure that has been performed within four weeks of the development of symptoms. The typical patient is older with a higher rate of underlying valvular abnormalities. The ever-expanding field of cardiovascular surgery and the increasing employment of various intravascular devices accounting great deal for this phenomenon. In a study of patients in the 1990s, the mean age was 50 with 35% more than 60 years of age. Individuals with congenital heart disease are living longer and frequently require heart surgery (4). In addition, rheumatic heart disease has essentially disappeared from the developed world. Change in the underlying valvular pathology: rheumatic heart disease <20% of cases b. The incidence ratio of men to women ranges up to 9/1 at 50 to 60 years of age (68). Although there are many types of valvular infections, they all share a common developmental pathway. Leukocytes adhere more readily to it and platelets become more reactive when in contact with it. As the infection progressed, the adherent bacteria were covered by successive layers of deposit fibrin. Within the thrombus, there is a tremendous concentration of organisms 9 (10 colony forming units per gram of tissue) (75). The endocardium of this area may be damaged by the force of the jet of blood hitting it (Mac Callums patch) (77). Bacterial infection of intravascular catheters depends on the response of the host to the presence of the foreign body, the pathogenic properties of the organisms, and the site of Table 5 Risk of Bacteremia Associated with Various Procedures Low (0%–20%) Moderate (20%–40%) High (40%–100%) Organism Tonsillectomy Bronchoscopy (rigid) Bronchoscopy (flexible) Streptococcal sp. Within a few days of its placement, a sleeve of biofilmconsisting of fibrin and fibronectin, along with platelets, albumin, and fibrinogen is deposited on the extraluminal surface of the catheter. This composite biofilm protects the pathogens from the host antibodies and white cells as well as administered antibiotics (86). For catheters that are left in place for less than nine days, contamination of the intracutaneous tracts by the patient’s skin flora is the most common source of infection (87). The bacteria migrate all the way from the insertion point to the tip of the catheter. It is the bacterial flora of health care workers hands that contaminate the hubs of the intravascular catheters as they go about their tasks of connecting infusate solutions or various types of measuring devices. The bacteria then migrate down the luminal wall and adhere to the biofilm and/or enter the bloodstream. For long-term catheters (those in place for more than 100 days), the concentration of bacteria that live within the biofilm of the luminal wall of the catheter is twice that of the exterior surface (88). Gram-negative aerobes such as Enterobacter, Pseudomonas, and Serratia species are the most likely to be involved because they are able to grow rapidly at room temperature in a variety of solutions. Because of its hypertonic nature, the solutions of total parenteral nutrition are bactericidal to most microorganisms except Candida spp.

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The signal from the microphone is sent of 10 months attain normal speech and are along the cable to the speech processor red viagra 200 mg amex. The speech processor acts on the signal younger the child order red viagra cheap, the greater the potential for according to coding strategies develop to language development and speech percep- enable optimal hearing with the cochlear tion order red viagra 200 mg amex. In response the auditory nerve carries out its natural function and conducts nerve impulses to the brain cheap red viagra 200 mg. The brain receives the nerve impulses and interprets them as sound, which the implant user hears. The whole process takes place within a few milliseconds, corresponding to the processing time in the normally functioning ear. There is an improved level of auditory sensa- tion and the ability to detect the presence of different sounds. Environmental Sounds: There is immediate detection of normal everyday sounds in the environment such as knock on the door or a door bell, horns of cars and motors, tele- phone ringing, dogs barking, background music and pleasurable sounds such as cooing of babies and rustling of leaves. Understanding of Speech: Implanted patients have limited speech discrimination (understanding). The transmitter transfers the signal toge- implant he can improve his speech ther with the energy required by the production because voice and articulation implanted electronic through the intact can be better controlled. The implanted receiver and stimulator is improvement with lip reading as the decodes the signal and sends a pattern of sound signal from the implant and visual small electrical impulses to the electrodes information work together. The small pulses conducted by the take part in everyday conversation more electrode contacts stimulate the spinal easily and can avoid to write things down. Hearing Aids and Cochlear Implant 129 Most implant users can tell the difference parents. After six months of use, a majo- between a man and a woman’s voice and rity of children respond to their names in they describe speech as sounding natural, quiet environment and spontaneously mechanical, clangy or muffled (like a radio recognise common sounds in the class- not tuned accurately to a station). Children implanted before the age patients enjoy the sound of music and of 3 years develop vocabulary within 3 some interpret music as noise. If there telephone but, in general are not able to are no contraindications, the patient is invited understand words, and for this reason they to take part in further assessments. They are able to the medical assessment so as to ensure that determine if there is a dial tone a busy there are no middle or inner ear problems signal, a ringing tone or whether someone that can interfere with the implantation. Tinnitus (Noises in the ear): These usually standard hearing tests, hearing aid fitting diminish or decrease after implantation. The hearing loss should be implant cannot fully restore nomal profound and an aided audiogram should hearing, adult clinical trials indicate 80 per not show any significant hearing. Child Benefits: Children also show comparison with average cochlear implant significant gains in sound awareness and performance. In small children it is speech uderstanding as reported by their particularly important to evaluate if the 130 Textbook of Ear, Nose and Throat Diseases child can be helped with a conventional receiver/stimulator. The electrode array is hearing aid before considering a cochlear inserted through an opening into the cochlea. Counselling: This is carried out to ensure construction of the electrode array helps it to proper motivation and realistic expecta- be placed into the cochlea and conform to its tions. The ground electrode is placed participate in regular programming and on the bone under the muscle. When the speech processor adjustment visits during incision is closed and the skin heals, the the first couple of years after implantation. Some specific risks intensive rehabilitation with the cochlear include possible strong interaction of strong implant. Psychological assessment: This is carried out Switch on Speech Therapy and to ensure that the patient is well-motivated Rehabilitation for this kind of treatment and has realistic Four to six weeks after surgey the patient expectations. He/she must also show returns to the hospital for the initial switch willingness to take part in auditory and on of the speech processor. In small children the person might be a candidate, then the initial switch on may require several days. Assessments of partici- rank these signals from very soft to comfort- pation of patient’s relatives in the cochlear ably loud. At the end of the programming implant programme is also done prior to session the information will be stored in the surgery. The begins in which the patient learns to associate surgeon forms a small depression in the speech with the patterns of sound which come mastiod bone behind the ear to hold the from the implant. Hearing Aids and Cochlear Implant 131 The programme involves both the patient facial expressions, gestures and hand and the family. Auditory training: Through an auditory as improvement in communication ability and trainer the deaf person is exposed to speech production. The success of this therapy various listening situations with different depends in large measure on the co-operation degrees of difficulty and are taught selec- of the patient who should also be prepared to tively to concentrate on speech sounds. Speech conservation: It is useful in persons can be increased by logopedic training or having sudden severe hearing loss who speech therapy at regular intervals usually a can’t monitor his own speech produc- couple of hours a week. Here tactile and proprioceptive that is needed can vary widely from case to feedback is used to monitor the speech case. Many postlingually Other Facilities for Severely deafened adults with period of deafness of less Deaf Patients can be than 5 years find speech therapy necessary i. Alerting devices to hear a telephone or therapy is required for deaf born children, door bell or baby cry. These devices who had no spoken language before receiv- produce extra loud signals. Telecommunication devices, where a tally deaf child is at the time of implantation, telephone amplifier is attached to a the more therapy will be necessary in trying telephone to increase the sound or a to make up for the time that was lost regarding telecommunication device for deaf speech and language acquisition. For example, one for sound signals back into type written noise, another for quiet and a third for music. Closed caption television decoders can Training of Deaf-mutes be attached to television sets to provide i. Speech reading or lipreading: Here patient cues for news, dramas and other is trained to study the movements of lips programmes. Sound is made up of either Acoustics involve the study of sound dealing simple harmonic motion (the pure tone) or with vibratory motion perceptible through the complex harmonic motion in which there are organ of hearing. Frequency: A vibrating body produces sound waves at a particular rate per second (cycles/second), called frequency. The range of frequencies to which the normal ear is sensitive is usually said to extend from 20 to 20,000 cycles/second covering approximately ten octaves. The variation in the velocity of propogation of sound waves is very wide, varying with the density and elasticity of the medium through which it passes. Principles of Audiometry 133 It involves one positive and one negative The formula for decibel (dB) estimation is excursion. Intensity: It is the physical measure of Where t1 is the intensity in watts of the amplitude of mass movement and is the existing sound and t2 the intensity in watts of measure of loudness of sound. Loudness: It is the physiological counterpart P ____1 Alternatively, dB = 20 log of the intensity. The unit of loudness is P 2 called, decibel which is 1/10 of a bel, the Where P1 is the sound pressure in dynes/ unit called after Graham Bell, inventor of cm2 of the existing sound and P the sound the telephone. Jet plane with burner 160 When comparing intensities of two diffe- Pain 140 rent sounds, it is often convenient to use in Limit of endurance 130 place of a simple ratio, decibel (dB) which is Discomfort (thunder) 120 equal to ten times the logarithm of a sound Boiler shop 100 under consideration to a reference sound. The Noisy street 80 reference sound usually taken is an intensity Normal conversation 60 which is very close to the normal threshold of Average office 40 hearing of the human ear at 1000 Hz. Quiet street 30 The reason for notation is to reduce a rather Whisper 20 larger ratio to a small usable number. This is Faintest audible sound 0 necessary primarily because of the tremen- Room Acoustics dous capability of the ear to hear over a large dynamic range. It is by reflection on hard walls and by absorp- In noting the degree of hearing at two tion in loose material that one can control the different frequencies, it would be a bit awk- acoustic properties of a room. Reflective walls ward to say that a person hears 1000 units at keep energy from spreading beyond the one frequency and 40000 units at another. However, such rooms are highly The sound intensity can be expressed as reverberant, that is, each signal causes sound pressure in dynes/cm2, or as particle multiple echoes which last for some time velocity is cm/s or as power in watts. There is little or no reverberation but sound does not “carry” either, so that low intensity sounds are lost in such rooms.

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Combined chlorine in water supplies may be formed in the treatment of raw waters containing ammonia or by the addition of ammonia or ammonium salts cheapest generic red viagra uk. Chlorinated wastewater effluents generic red viagra 200 mg fast delivery, as well as certain chlorinated industrial effluents generic 200 mg red viagra overnight delivery, normally contain only combined chlorine order red viagra in india. Historically the principal analytical problem has been to distinguish between free and combined forms of chlorine. Waterborne Diseases ©6/1/2018 481 (866) 557-1746 Waterborne Diseases ©6/1/2018 482 (866) 557-1746 Sodium Hypochlorite Section Physical Properties - Sodium Hypochlorite Description: Clear greenish yellow liquid. Warning properties: Chlorine odor; inadequate warning of hazardous concentrations. Sodium hypochlorite has a variety of uses and is an excellent disinfectant/antimicrobial agent. When sodium hypochlorite is used, it must be counterbalanced by a strong acid like sodium bisulfate or muriatic acid to keep the pH within the ideal range. Sodium hypochlorite differs from chlorine gas in two respects: method of feed and hydrolization properties. In large concentrations it may artificially elevate pH, leading to precipitation of calcium carbonate. Many of the other problems associated with chlorine remain present with sodium hypochlorite. Waterborne Diseases ©6/1/2018 483 (866) 557-1746 When was Sodium Hypochlorite Discovered? Around 1785 the Frenchman Berthollet developed liquid bleaching agents based on sodium hypochlorite. Characteristics of Sodium hypochlorite Sodium hypochlorite is a clear, slightly yellowish solution with a characteristic odor. As a bleaching agent for domestic use it usually contains 5% sodium hypochlorite (with a pH of around 11, it is irritating). If it is more concentrated, it contains a concentration 10-15% sodium hypochlorite (with a pH of around 13, it burns and is corrosive). Chlorine evaporates at a rate of 0,75 gram active chlorine per day from the solution. This also happens when sodium hypochlorite comes in contact with acids, sunlight, certain metals and poisonous and corrosive gasses, including chlorine gas. Sodium hypochlorite is a strong oxidator and reacts with flammable compounds and reductors. These characteristics must be kept in mind during transport, storage and use of sodium hypochlorite. When sodium hypochlorite dissolves in water, two substances form, which play a role in oxidation and disinfection. Sulfuric acid is a strong acid that strongly reacts with bases and is very corrosive. Sodium hypochlorite can be produced in two ways: - By dissolving salt in softened water, which results in a concentrated brine solution. In households, hypochlorite is used frequently for the purification and disinfection of the house. Salt Electrolysis System The advantage of the salt electrolysis system is that no transport or storage of sodium hypochlorite is required. Another advantage of the onsite process is that chlorine lowers the pH and no other acid is required to lower pH. The hydrogen gas that is produced is explosive and as a result ventilation is required for explosion prevention. The maintenance and purchase of the electrolysis system is much more expensive than sodium hypochlorite. Because sodium hypochlorite is used both to oxidize pollutants (urine, sweat, cosmetics) and to remove pathogenic microorganisms, the required concentration of sodium hypochlorite depends on the concentrations of these pollutions. Especially the amount of organic pollutants helps determine the required concentration. If the water is filtered before sodium hypochlorite is applied, less sodium hypochlorite is needed. Waterborne Diseases ©6/1/2018 485 (866) 557-1746 Theory Disinfection with chlorine is very popular in water and wastewater treatment because of its low cost, ability to form a residual, and its effectiveness at low concentrations. Although it is used as a disinfectant, it is a dangerous and potentially fatal chemical if used improperly. Despite the fact the disinfection process may seem simple, it is actually a quite complicated process. When free chlorine is added to the wastewater, it takes on various forms depending on the pH of the wastewater. It is important to understand the forms of chlorine which are present because each has a different disinfecting capability. The graph below depicts the chlorine fractions at different pH values (Drawing by Erik Johnston). Ammonia present in the effluent can also cause problems as chloramines are formed, which have very little disinfecting power. Some methods to overcome the types of chlorine formed are to adjust the pH of the wastewater prior to chlorination or to simply add a larger amount of chlorine. An adjustment in the pH would allow the operators to form the most desired form of chlorine, hypochlorus acid, which has the greatest disinfecting power. Adding larger amounts of chlorine would be an excellent method to combat the chloramines because the ammonia present would bond to the chlorine but further addition of chlorine would stay in the hypochlorus acid or hypochlorite ion state. Waterborne Diseases ©6/1/2018 486 (866) 557-1746 Recommendations for Preparing/Handling/Feeding Sodium Hypochlorite Solutions As a result of the pressures brought to bear by Health and Safety requirements, some users of gas have chosen to seek alternative forms of disinfectants for their water and wastewater treatment plants. Product Stability The oxidizing nature of this substance means that it should be handled with extreme care. Waterborne Diseases ©6/1/2018 487 (866) 557-1746 Waterborne Diseases ©6/1/2018 488 (866) 557-1746 Exposure There is no threshold value for to sodium hypochlorite exposure. After swallowing sodium hypochlorite the effects are stomach ache, a burning sensation, coughing, diarrhea, a sore throat and vomiting. Routes of Exposure Inhalation Hypochlorite solutions can liberate toxic gases such as chlorine. Chlorine is heavier than air and may cause asphyxiation in poorly ventilated, enclosed, or low-lying areas. Children exposed to the same levels of gases as adults may receive a larger dose because they have greater lung surface area/body weight ratios and higher minute volumes/weight ratios. Children may be more vulnerable to corrosive agents than adults because of the smaller diameter of their airways. In addition, they may be exposed to higher levels than adults in the same location because of their short stature and the higher levels of chlorine found nearer to the ground. Skin/Eye Contact Direct contact with hypochlorite solutions, powder, or concentrated vapor causes severe chemical burns, leading to cell death and ulceration. Because of their relatively larger surface area/weight ratio, children are more vulnerable to toxicants affecting the skin. Ingestion Ingestion of hypochlorite solutions causes vomiting and corrosive injury to the gastrointestinal tract. Household bleaches (3 to 6% sodium hypochlorite) usually cause esophageal irritation, but rarely cause strictures or serious injury such as perforation. Commercial bleaches may contain higher concentrations of sodium hypochlorite and are more likely to cause serious injury. Metabolic acidosis is rare, but has been reported following the ingestion of household bleach. Pulmonary complications resulting from aspiration may also be seen after ingestion. Sources/Uses Sodium and calcium hypochlorite are manufactured by the chlorination of sodium hydroxide or lime. Sodium and calcium hypochlorite are used primarily as oxidizing and bleaching agents or disinfectants. They are components of commercial bleaches, cleaning solutions, and disinfectants for drinking water and waste water purification systems and swimming pools. Sodium Hypochlorite as a Disinfectant has the Following Advantages: It can be easily stored and transported when it is produced on-site. Waterborne Diseases ©6/1/2018 489 (866) 557-1746 Disadvantages Sodium hypochlorite is a dangerous and corrosive substance.

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Abdominal abscesses in patients having surgery: an application of Ga-67 scintigraphic and computed tomographic scanning order red viagra without a prescription. Postoperative enterococcal infection after treatment of complicated intra-abdominal sepsis buy red viagra. Determinants for successful percutaneous image-guided drainage of intra-abdominal abscess buy cheap red viagra online. Percutaneous postoperative intra-abdominal abscess drainage after elective colorectal surgery buy red viagra 200mg amex. Open management of the abdomen and planned reoperations in severe bacterial peritonitis. Planned reoperations and open management in critical intra-abdominal infections: prospective experience in 52 cases. Clostridium difficile-associated diarrhea: risk factors, diagnostic methods, and treatment. Ultrasound is not a useful screening tool for acute acalculous cholecystitis in critically ill trauma patients. Diagnosis, treatment and prophylaxis of spontaneous bacterial peritonitis: a consensus document. Review article: spontaneous bacterial peritonitis—diagnosis, treatment and prevention. Primary pneumococcal peritonitis in patients with cardiac ascites: report of 2 cases. Spontaneous bacterial peritonitis by campylobacter fetus in Budd- Chiari syndrome without liver cirrhosis. Abdominal compartment syndrome in patients with severe acute pancreatitis in early stage. Intraabdominal sepsis: newer interventional and antimicrobial therapies for infected necrotizing pancreatitis. Antibiotic therapy for prophylaxis against infection of pancreatic necrosis in acute pacreatitis. Accurate diagnosis of infarction of omentum and appendices epiploicae by computed tomography. Blood stream infections of abdominal origin in the intensive care unit: characteristics and determinants of death. Hjalmarson Division of Geographic Medicine and Infectious Diseases, Department of Medicine, Tufts Medical Center, Boston, Massachusetts, U. Gorbach Nutrition/Infection Unit, Department of Public Health and Family Medicine, Tufts University School of Medicine, and Division of Geographic Medicine and Infectious Diseases, Department of Medicine, Tufts Medical Center, Boston, Massachusetts, U. Staphylococcus aureus was the suspected pathogen since it was frequently recovered from patients stool culture samples. With increased use of cephalosporins in the 1980 to 2000, it became the antibiotic class most commonly associated with C. The incidence among hospitalized patients increased from 3 to 12/1000 persons in 1991 to 2001 to 25 to 43/1000 persons in 2003 to 2004. In addition, there were increased rates of more serious disease that was refractory to therapy. Symptomatic and asymptomatic infected patients are the major reservoirs and sources for environmental contamination. A study from 2004 showed that incidence is higher during winter months, which may reflect increased patient census, severity of illness, and antibiotic use due to high rates of respiratory infections (16). It persists as a highly resistant spore that may survive for months in the environment. The gastrointestinal tract of young mammals, including humans, appears to be a reservoir. Most cases of disease appear to be caused by acquisition of the organism from an exogenous source, rather than from endogenous colonization. In fact, colonization with either toxigenic or nontoxigenic strains appears to protect from clinical disease (20). Antibiotic Exposure 12 In healthy adults, the colon contains as many as 10 bacteria/g of feces, the majority of which are anaerobic organisms (21). This flora provides an important host defense by inhibiting colonization and overgrowth with C. An animal model (22) showed that agents that disrupt the intestinal flora and lack activity against C. In general, however, antibiotics with significant antianaerobic activity, and to which C. Fluoroquinolones (ciprofloxacin) were approved for use in the United States 1987 and has been frequently used to treat inpatient and outpatient infections. In addition, patient clustering, a greater likelihood of antibiotic use, and a larger proportion of elderly patients may facilitate transfer of the organism (1). The rates of colonization in the feces among hospitalized patients are 10% to 25% and 4% to 20% among residents of long-term facilities as opposed to 2% to 3% among healthy adults in the general population. Other factors that increase the vulnerability of the elderly are underlying severe disease, nonsurgical gastrointestinal procedures, and poor immune response to C. In addition, there is a higher likelihood of comorbidities in older patients that may lead to more frequent hospitalizations and exposure to antibiotics compared with the younger population. Immunity Host immune response plays an essential role in determining whether patients become colonized with C. As mentioned previously, most patients remain asymptomatic following acquisition of C. Patients with a normal immune system who are exposed to toxin A, mount serum IgG antitoxin A antibody in response to C. In elderly patients and patients with severe underlying illnesses, the immunologic response may be blunted leading to lower serum antibody response to toxin A. In the colon, the spores convert to their vegetative, toxin-producing form and become susceptible to killing by antimicrobial agents. Toxin A is a 308-kDa enterotoxin that produces acute inflammation, leading to intestinal fluid secretion and mucosal injury (33). Toxin B is a 270-kDa cytotoxin that is 10 times more potent than toxin A in mediating mucosal damage in vitro. Both toxins act intracellularly by inactivating proteins in the Rho subfamily, which regulate the F-actin cytoskeleton. This results in disaggregation of actin, opening the tight junctions between cells, and resulting in cell retraction and apoptosis manifested as characteristic cell rounding in tissue culture assays and shallow ulceration on the intestine mucosal surface (17,34). Both toxins are also proinflammatory, inducing release of cytokines, phospholipase A2, platelet-activating factor (33), tumor necrosis factor-a, and substance P. This results in the activation of the enteric nervous system, leading to neutrophil chemotaxis and fluid secretion. While most strains produce both toxins, some produce toxin B only but can be equally virulent as strains with both toxins. Colonization rates of 25% to 80% are seen in healthy infants and neonates but clinical illness is rare (3). For unclear reasons, colonization appears to wane with advancing age, and 276 Hjalmarson and Gorbach Table 2 Definition of Clostridium difficile infection 1. Presence of symptoms >3 unformed stools over 24 hours for at least 2 days in the absence of ileus and 2. Positive stool test for the presence of toxigenic Clostridium difficile or its toxins or 3. Colonization increases to 20% to 30% of hospitalized adults (26), but clinical symptoms develop in only one-third of those who become colonized (34). However, colonized individuals shed pathogenic organisms and serve as a reservoir for environmental contamination. Symptoms can begin as early as the first day of antibiotic use or as late as eight weeks after completion of the precipitating antibiotic course (25). For mild disease, the diarrhea is usually the only symptom, involving <10 episodes a day without systemic symptoms. The diarrhea is frequently watery with a characteristic foul odor, but it can also be mucoid or mushy. Moderate disease, defined as <10 bowel movements per day, leukocytosis <15,000 cells/mL, and creatinine <1. Severe disease defined as >10 bowel movements per day, leukocytosis >15,000 cells/mL, elevated creatinine (>1.

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