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The spectrum of infectious agents changes with the passage of time and the introduction of drugs and chemicals designed to destroy them. The advent of antibiotics and the resultant development of resistant strains of bacteria have introduced new types of pathogens little known or not previously thought to be significantly dangerous to man. A few decades ago, gram-positive organisms were the most common infectious agents. Today the gram-negative microorganisms, and Proteus, Pseudomonas, and Serratia are particularly troublesome, especially in the development of hospital-acquired infections. It is predicted that in future decades other lesser known pathogens and new strains of bacteria and viruses will emerge as common causes of infections.
The development of resistant strains of pathogens can be limited by the judicious use of antibiotics. This requires culturing and sensitivity testing for a specific antibiotic to which the identified causative organism has been found to be sensitive. If the patient has been receiving a broad-spectrum antibiotic prior to culture and sensitivity testing, this should be discontinued as soon as the specific antibiotic for the organism has been found. It would be helpful, too, if the general public understood that antibiotics are not cure-alls and that there is danger in using them indiscriminately. In some instances an antibiotic can upset the normal flora of the body, thus compromising the body's natural resistance and making it more susceptible to a second infection (superinfection) by a microorganism resistant to the antibiotic.
Although antibacterials have greatly reduced mortality and morbidity rates for many infectious diseases, the ultimate outcome of an infectious process depends on the effectiveness of the host's immune responses. The antibacterial drugs provide a holding action, keeping the growth and reproduction of the infectious agent in check until the interaction between the organism and the immune bodies of the host can subdue the invaders.
Intracellular infectious agents include viruses, mycobacteria, Brucella, Salmonella, and many others. Infections of this type are overcome primarily by T lymphocytes and their products, which are the components of cell-mediated immunity. Extracellular infectious agents live outside the cell; these include species of Streptococcus and Haemophilus. These microorganisms have a carbohydrate capsule that acts as an antigen to stimulate the production of antibody, an essential component of humoral immunity.
Infection may be transmitted by direct contact, indirect contact, or vectors. Direct contact may be with body excreta such as urine, feces, or mucus, or with drainage from an open sore, ulcer, or wound. Indirect contact refers to transmission via inanimate objects such as bed linens, bedpans, drinking glasses, or eating utensils. Vectors are flies, mosquitoes, or other insects capable of harboring and spreading the infectious agent.
Special precautions for prevention of the spread of infection can vary from strict isolation of the patient and such measures as wearing gloves, mask, or gown to simply using care when handling infective material. No matter what the diagnosis or status of the patient, handwashing before and after each contact is imperative.
Unrecognized or subclinical infections pose a threat because many infectious agents can be transmitted when symptoms are either mild or totally absent.
In the care of patients for whom special precautions have not been assigned, gloves are indicated whenever there is direct contact with blood, wound or lesion drainage, urine, stool, or oral secretions. Gowns are worn over the clothing whenever there is copious drainage and the possibility that one's clothes could become soiled with infective material.
When a definitive diagnosis of an infectious disease has been made and special precautions are ordered, it is imperative that everyone having contact with the patient adhere to the rules. Family members and visitors will need instruction in the proper techniques and the reason they are necessary.
Physiologic support entails bolstering the patient's external and internal defense mechanisms. Integrity of the skin is preserved. Daily bathing is avoided if it dries the skin and predisposes it to irritation and cracking. Gentle washing and thorough drying are necessary in areas where two skin surfaces touch, for example, in the groin and genital area, under heavy breasts, and in the axillae. Lotions and emollients are used not only to keep the skin soft but also to stimulate circulation. Measures are taken to prevent pressure ulcers from prolonged pressure and ischemia. Mouth care is given on a systematic basis to assure a healthy oral mucosa.
The total fluid intake should not be less than 2000 ml every 24 hours. Cellular dehydration can work against adequate transport of nutrients and elimination of wastes. Maintenance of an acid urine is important when urinary tract infections are likely as when the patient is immobilized or has an indwelling urinary catheter. This can be accomplished by administering vitamin C daily. Nutritional needs are met by whatever means necessary, and may require supplemental oral feedings or total parenteral nutrition. The patient will also need adequate rest and freedom from discomfort. This may necessitate teaching her or him relaxation techniques, planning for periods of uninterrupted rest, and proper use of noninvasive comfort measures, as well as judicious use of analgesic drugs.
Having an infectious disease can alter patients' self-image, making them feel self-conscious about the stigma of being infectious or “dirty,” or making them feel guilty about the danger they could pose to others. Social isolation and loneliness are also potential problems for the patient with an infectious disease.
Patients also can become discouraged because some infections tend to recur or to involve other parts of the body if they are not effectively eradicated. It is important that they know about the nature of their illness, the purposes and results of diagnostic tests, and the expected effect of medications and treatments.
Patient education should also include information about the ways in which a particular infection can be transmitted, proper handwashing techniques, approved disinfectants to use at home, methods for handling and disposing of contaminated articles, and any other special precautions that are indicated. If patients are to continue taking antibacterials at home, they are cautioned not to stop taking any prescribed medication even if symptoms abate and they feel better.
Practitioners in infection control are often nurses employed by hospitals. They have titles such as Infection Control Officer and Infection Control Nurse, and they function as liaisons between staff nurses, physicians, department heads, the infection control committee, and the local health department. Such practitioners also assume some responsibility for teaching patients and their families, as well as employees of the hospital.
The centers for disease control and prevention is an excellent source of information related to infection control; their web site is http://www.cdc.gov. Another source of help and support for infection control practitioners is the Association for Practitioners in Infection Control and Epidemiology, 1275 K St., NW, Suite 100, Washington, DC 20005-4006.
infectionEpidemiology The presence of a pathogen in a host which may or may not be associated with clinical disease. See Acute HIV infection, Atypical mycobacterial infection, Breakthrough infection, Chronic symptomatic HIV infection, Close contact infection, Congenital CMV infection, Cross-infection, Danger space infection, Ear infection, Emerging infection, Exit-site infection, Fungal infection, HIV-1 superinfection, Hyperinfection, Latent clostridial infection, Mixed wound infection, Multiple infection, Multiplicity of infection, Mycobacterial infection, Nail infection, Nonprogressive HIV infection, Nosocomial infection, Occult infection, Opportunistic infection, Parasitic infection, Perivascular inflammation, Ping pong infection, Pocket infection, Reemerging infection, Respiratory tract infection, Satellite infection, Silent infection, Spillover infection, Sterile infection, Subclinical infection, Superinfection, Surgical site infection, Tap water infection, Tunnel infection, Urinary tract infection. Cf Disinfection.
infection(in-fek'shon) [L. infectio, discoloration, dye]
The most common pathogenic organisms are bacteria (including mycobacteria, mycoplasmas, spirochetes, chlamydiae, and rickettsiae), viruses, fungi, protozoa, and helminths. Life-threatening infectious disease usually occurs when immunity is weak or suppressed (such as during the first few months of life, in older or malnourished persons, in trauma or burn victims, in leukopenic patients, and in those with chronic illnesses such as diabetes mellitus, renal failure, cancer, asplenia, alcoholism, or heart, lung, or liver disease). Many disease-causing agents, however, may afflict vigorous persons, whether they are young or old, fit or weak. Some examples include sexually transmitted illnesses (such as herpes simplex or chlamydiosis), respiratory illnesses (influenza or varicella), and food or waterborne pathogens (cholera, schistosomiasis).
Systemic infections cause fevers, chills, sweats, malaise, and occasionally, headache, muscle and joint pains, or changes in mental status. Localized infections produce tissue redness, swelling, tenderness, heat, and loss of function.
Pathogens can be transmitted to their hosts by many mechanisms, namely, inhalation, ingestion, injection or the bite of a vector, direct (skin-to-skin) contact, contact with blood or body fluids, fetomaternal contact, contact with contaminated articles (fomites), or self-inoculation.
In health care settings, infections are often transmitted to patients by the hands of professional staff or other employees. Hand hygiene before and after patient contact prevents many of these infections.
The body's defenses against infection begin with mechanisms that block entry of the organism into the skin or the respiratory, gastrointestinal, or genitourinary tract. These defenses include chemicals, e.g., lysozymes in tears, fatty acids in skin, gastric acid, and pancreatic enzymes in the bowel; mucus that traps the organism; clusters of antibody-producing B lymphocytes, e.g., tonsils, Peyer's patches; and bacteria and fungi (normal flora) on the skin and mucosal surfaces that destroy more dangerous organisms. In patients receiving immunosuppressive drug therapy, the normal flora can become the source of opportunistic infections. Also, one organism can impair external defenses and permit another to enter; e.g., viruses can enhance bacterial invasion by damaging respiratory tract mucosa.
The body's second line of defense is the nonspecific immune response, inflammation. The third major defensive system, the specific immune response, depends on lymphocyte activation, during which B and T cells recognize specific antigenic markers on the organism. B cells produce immunoglobulins (antibodies), and T cells orchestrate a multifaceted attack by cytotoxic cells. See: B cell; T cell; inflammation for table
Once pathogens have crossed cutaneous or mucosal barriers and gained entry into internal tissues, they may spread quickly along membranes such as the meninges, pleura, or peritoneum. Some pathogens produce enzymes that damage cell membranes, enabling them to move rapidly from cell to cell. Others enter the lymphatic channels; if they can overcome white blood cell defenses in the lymph nodes, they move into the bloodstream to multiply at other sites. This is frequently seen with pyogenic organisms, which create abscesses far from the initial entry site. Viruses or rickettsiae, which reproduce only inside cells, travel in the blood to cause systemic infections; viruses that damage a fetus during pregnancy (such as rubella and cytomegalovirus) travel via the blood.
Although many infections (such as those that cause characteristic rashes) are diagnosed clinically, definitive identification of infection usually occurs in the laboratory. Carefully collected and cultured specimens of blood, urine, stool, sputum, or other body fluids are used to identify pathogens and their susceptibilities to treatment.
Many infections, like the common cold, are self-limited and require no specific treatment. Understanding this concept is crucial because the misuse of antibiotics does not help the affected patient and may damage society by fostering antimicrobial resistance, e.g., in microorganisms such as methicillin-resistant Staphylococcus aureus. Many common infections, such as urinary tract infections or impetigo, respond well to antimicrobial drugs. Others, like abscesses, may require incision and drainage.
bladder infectionSee: urinary tract infection
cytomegalovirus infectionAbbreviation: CMV infection
During pregnancy, the woman can transmit the virus transplacentally to the fetus with devastating results. Approx. 10% of infected infants develop CMV inclusion disease, marked by anemia, thrombocytopenia, purpura, hepatosplenomegaly, microcephaly, and abnormal mental or motor development; more than 50% of these infants die. Most fetal infections occur when the mother is infected with CMV for the first time during this pregnancy, but they may also occur following reinfection or reactivation of the virus. Patients with AIDS or organ transplants may develop disseminated infection that causes retinitis, esophagitis, colitis, meningoencephalitis, pneumonitis, and inflammation of the renal tubules.
CMV is transmitted from person to person by sexual activity, during pregnancy or delivery, during organ transplantation, or by contaminated secretions; rarely, (5%) blood transfusions contain latent CMV. Health care workers caring for infected newborns or immunosuppressed patients are at no greater risk for acquiring CMV infection than are those who care for other groups of patients (approx. 3%). Pregnant women and all health care workers should strictly adhere to standard infection control precautions.
Primary infection in the healthy is usually asymptomatic, but some people develop mononucleosis-type symptoms (fever, sore throat, swollen glands). Symptoms in immunosuppressed patients are related to the organ system infected by CMV and include blurred vision progressing to blindness; severe diarrhea; and cough, dyspnea, and hypoxemia. Antibodies seen in the blood identify infection but do not protect against reactivation of the virus.
Antiviral agents such as ganciclovir and foscarnet are used to treat retinitis, colitis, and pneumonitis in immunosuppressed patients; chronic antiviral therapy has been used to suppress CMV, but this protocol has not been effective in preventing recurrence of CMV or development of meningoencephalitis. Ganciclovir has limited effect in congenital CMV. No vaccine is available.
Health care providers can help prevent CMV infections by advising pregnant women and the immunocompromised to avoid exposure to contact with people who have confirmed and or suspected cases of CMV. The virus spreads from one person to another as a result of exposure to blood (as in transfusions) and other body fluids including feces, urine, and saliva. Contact with the diapers or drool of an infected child may result in infection of a person who has previously been unexposed to the infection. CMV is the most common congenital infection, affecting about 35,000 newborns each year. CMV infection that is newly acquired during the first trimester of pregnancy can be esp. hazardous to the developing fetus. As a result, young women who have no antibodies to CMV should avoid providing child care to infected youngsters. In the U.S., nurses who have failed to advise infected patients of the risk that CMV may pose to others have been judged to be negligent by the courts. Parents of children with severe congenital CMV require support and counseling. Although CMV infection in most nonpregnant adults is not harmful, it can cause serious illnesses or death in people with HIV/AIDS, organ transplants, and those who take immunosuppressive or cancer chemotherapeutic drugs. Infected immunosuppressed patients with CMV should be advised about the uses of prescribed drug therapies, the importance of completing the full course of therapy, and adverse effects to report for help in managing them. Family caregivers for infected people should be taught to observe standard precautions when handling body secretions. Since asymptomatic people may have and secrete the virus, standard precautions should be maintained by health care professionals at all times when such secretions are present or being handled.
deep neck infection
diabetic foot infection
fungal infection of nail
health-care associated infectionAbbreviation: HAI
hospital-acquired infectionNosocomial infection.
Hospital-acquired infections result from the exposure of debilitated patients to the drug-altered environment of the hospital, where indwelling urinary catheters, intravenous lines, and endotracheal tubes enter normally sterile body sites and allow microbes to penetrate and multiply. Over 2 million nosocomial infections occur in the U.S. annually. Antibiotic-resistant organisms such as Enterobacter spp., Pseudomonas spp., staphylococci, enterococci, Clostridium difficile, and fungi often are responsible for the infectious outbreaks that result. Standard precautions and infection control procedures limit the incidence of nosocomial infections.
opportunistic infectionAbbreviation: OI
reproductive tract infectionAbbreviation: RTI
risk for infection
slow virus infection
surgical site infection
surgical wound infectionSurgical site infection.
transfusion-associated bacterial infectionTransfusion-transmitted bacterial infection.
transfusion-transmitted bacterial infectionAbbreviation: TTBI.
Viruses may also be transmitted from blood donors to transfusion recipients. They may include cytomegalovirus, encephalitis viruses, and, rarely, hepatitis viruses or human immunodeficiency virus.
upper respiratory infectionAbbreviation: URI
urinary tract infectionAbbreviation: UTI
Escherichia coli causes about 80% of all UTIs. In young women, Staphylococcus saprophyticus is also common. In men with prostate disease, enterococci are often responsible. The small remaining percentage of infections may be caused by Klebsiella species, Proteus mirabilis, Staphylococcus aureus, Pseudomonas aeruginosa, or other virulent organisms.
The presenting symptoms of UTI vary enormously. Young patients with bladder infections may have pain with urination; urinary frequency or urgency, or both; pelvic or suprapubic discomfort; low-grade fevers; or a change in the appearance or odor of their urine (cloudy, malodorous, or rarely bloody). Older patients may present with fever, lethargy, confusion, delirium, or coma caused by urosepsis. Patients with pyelonephritis often complain of flank pain, prostration, nausea, vomiting, diarrhea, and high fevers with shaking chills. UTI may also be asymptomatic, esp. during pregnancy. Asymptomatic UTI during pregnancy is a contributing factor to maternal pyelonephritis, or fetal prematurity and stillbirth.
Urinalysis (obtained either as a clean catch or catheterized specimen) and subsequent urinary culture are used to determine the presence of UTI, the suspect microorganism, and the optimal antibiotic therapy. A dipstick test may identify leukocyte esterase and nitrite in a urinary specimen, strongly suggesting a UTI. The presence of more than 8 to 10 white blood cells per high-power field of spun urine also strongly suggests UTI, as does the presence of bacteria in an uncentrifuged urinary specimen.
Sulfa drugs, nitrofurantoin, cephalosporins, or quinolones may be used for the outpatient treatment of UTIs while the results of cultures are pending. Patients sick enough to be hospitalized may also be treated with intravenous aminoglycosides, medicine to treat nausea and vomiting, and hydration. The duration of therapy and the precise antibiotics used depend on the responsible organism and the underlying condition of the patient. Patients with anatomical abnormalities of the urinary tract, e.g., children with ureteropelvic obstruction or older men with bladder outlet obstruction, may sometimes require urological surgery.
The following conditions predispose sexually active women to development of UTI: the use of a contraceptive diaphragm, the method of sexual intercourse, (greatly prolonged or cunnilingus), and failure to void immediately following intercourse.
Prevention of UTI in Young Women
Fluid intake should be increased to and maintained at to six to eight glasses daily. Although cranberry and other fruit juices are often recommended for patients with UTI, there is little objective evidence to show they have an impact. The urinary tract anesthetic phenazopyridine and sitz baths may provide relief from perineal discomfort. The anal area should be wiped from front to back or wipe the front first to prevent carrying bacteria to the urethral area; the bladder should be emptied shortly before and after intercourse; the genital area should be washed before intercourse; if vaginal dryness is a problem, water-soluble vaginal lubricants should be used before intercourse; a contraceptive diaphragm, cap, shield, or sponge should not remain in the vagina longer than necessary. An alternative method of contraception should be considered.
Instructing the patient should emphasize self-care and prevention of recurrences. The antibiotic regimen should be explained, and the patient should be aware of signs and symptoms and, when they occur, should report them promptly to the primary caregiver.
|Superficial Fungal Infections|
|Disease||Causative Organisms||Structures Infected||Microscopic Appearance|
|Epidermophytosis (e.g., dhobie itch)||Epidermophyton, (e.g., floccosum)||Inguinal, axillary, and interdigital folds; hairs not affected||Long, wavy, branched, and segmented hyphae and spindle-shaped cells in stratum corneum|
|Favus (tinea favosa)||Trichophyton schoenleinii||Epidermis around a hair; all parts of body; nails||Vertical hyphae and spores in epidermis; sinuous branching mycelium and chains in hairs|
|Ringworm (tinea, otomycosis)||Microsporum (e.g., audouinii)||Horny layer of epidermis and hairs, chiefly of scalp||Fine septate mycelium inside hairs and scales; spores in rows and mosaic plaques on hair surface|
|Trichophyton (e.g., tonsurans)||Hairs of scalp, beard, and other parts; nails||Mycelium of chained cubical elements and threads in and on hairs; often pigmented|
|Thrush and other forms of candidiasis||Candida albicans||Tongue, mouth, throat, vagina, and skin||Yeastlike budding cells and oval thick-walled bodies in lesion|
|Systemic Fungal Infections|
|Aspergillosis||Aspergillus fumigatus||Lungs||Y-shaped branching of septate hyphae|
|Blastomycosis||Blastomyces brasiliensis, B. dermatitidis||Skin and lungs||Yeastlike cells demonstrated in lesion|
|Candidiasis||Candida albicans||Esophagus, lungs, peritoneum, mucous membranes||Small, thin-walled, ovoid cells|
|Coccidioidomycosis||Coccidioides immitis||Respiratory tract||Nonbudding spores containing many endospores, in sputum|
|Cryptococcosis||Cryptococcus neoformans||Meninges, lungs, bone, skin||Yeastlike fungus having gelatinous capsule; demonstrated in spinal fluid|
|Histoplasmosis||Histoplasma capsulatum||Lungs||Oval, budding, uninucleated cells|
infectionthe invasion of tissues by microorganisms with or without disease production.
infectioninvasion and multiplication of microorganisms or parasites within tissue; signs of infection are masked in subclinical infection, or the immunocompromised; Table 1; see sepsis; Table 2
|Strategy||Examples of actions|
|Elimination of sources and reservoirs of infection||Care with exposure of infected lesions to avoid cross-contamination to adjacent tissues or the environment|
Use of appropriate disposable barrier clothing
Decontamination of instruments following a recognized protocol
Thorough hand-cleansing routines and the use of disposable gloves, especially if there are any cuts or infections on the clinician's hands
Avoiding patient contact if the clinician shows signs of infection
Maintaining personal vaccination programmes
Thorough cleaning of all parts of the clinical environment, appropriate disposal of clinical waste and elimination of chronically wet areas (such as soap dishes)
|Disruption of routes of transmission||Frequent and regular decontamination of all:|
Hand-held equipment by scrubbing under running water or by immersion in an ultrasonic cleaning bath followed by exposure to pressurized steam by processing through an autoclave (immersion in disinfecting solutions and exposure to heat are no longer considered adequate)
Large items of equipment by washing with water and detergent, drying then swabbing with alcohol wipes
Use of elbow-operated liquid soap dispensers rather than bars of soap
Use of single-use nail brushes
Use of disposable paper towels
Use of hypochlorite disinfectant solutions to clean up spillages of body fluids, according to the manufacturer's instructions
|Promoting host resistance||Preoperative preparation of the patient's skin with chlorhexidine (0.5% chlorhexidine gluconate in 70% IMS) or povidone-iodine (10% povidone-iodine in water or IMS, releasing 1% active iodine), left in situ for 5 minutes|
Postoperative skin dressing of chlorhexidine or povidone-iodine
Use of antimicrobial agents, such as silver, iodine, antibiotic or antifungal agents when frank infection is noted or suspected
Advice to diabetic and immunocompromised patients on general care and health
IMS, industrial methylated spirit.
|Identified microorganism||Example of antimicrobial drug|
|Streptococci||Oral amoxicillin 500mg tds (or IV amoxicillin 500mg 8-hourly)|
|Staphylococci||Oral flucloxacillin 500mg qds (or IV flucloxacillin 500mg 6-hourly)|
|Anaerobes||Oral metronidazole 400mg tds (or IV metronidazole 500mg 8-hourly)|
|Gram-negatives||Oral ciprofloxacin 500mg bd (or IV ceftazidime 1g 6-hourly)|
2. an infection caused by streptococci that produce a toxic substance (hemolysin) that will lyse the erythrocytes and liberate hemoglobin from red blood cells.
Patient discussion about infection
Q. Yeast infection in bloodstream How to get rid of yeast infection systemically.
Q. Is this an infection or pregnancy? I am worried with the white odorless mucus discharge. My hubby and I are also trying for baby. I have browsed the web and found that this could be possible infection also. Is this an infection or pregnancy?
Q. What are the symptoms of salmonella infection?