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wn, UNIT III, , INFECTION & ITS, TRANSMISSION, , 1, INSIDE:, , A. Sources & Types of infection, nosocomial Infection, , 8, Factors affecting growth of microbes, , C. Cycle of transmission of infection, portals of entry & exit, modes of transfer, D. Mechanism of resistance to infection, , E.Collection of specimens, , , , , , , , IMPORTANT DEFINITIONS, , Asepsis: A state of being free from disease causing microorganisms., Aseptic technique: Aseptic technique is a general term involving practices that minimize the introduction, of microorganisms to patients during patient care., , Atypical infection: where in which the typical or characteristic clinical manifestations of the particular, infectious disease are not seen or do not have proper clinical manifestations., , Antiseptic: The disinfectant that is applied to living tissue is referred to as an antiseptic., , Carrier: The person who harbors the pathogenic microorganisms without suffering from any ill effect, because of it., , Chronic infection: Has a long duration. E.g. Tuberculosis., Commensals: Organisms that live in an intimate, non parasitic relationship, Contagious infection: Diseases transmitted by direct contact., , Cross infection: When a patient already suffering from an infection acquires another infection from, another patient or any other external source., , Endogenous sources: Sources within the body of an individual, , Fomites: Inanimate objects like contaminated towels, utensils that may transmit infection, Generalized infection: Affects many or all parts of the body. ex. Blood infection like typhoid fever., latrogenic infection: This term refers to physician-induced infections resulting from investigative,, therapeutic or other procedure like surgery., , Infection: Invasion & multiplication of pathogenic microorganisms in bodily parts or tissues which may, produce subsequent tissue injury & progress to disease through a variety of cellular or toxic mechanisms., , Latent infection: Infection wherein remains in the tissues in the latent or hidden form proliferating and, producing clinical disease when the host resistance is lowered., Localization infection: Restricted to a limited area of the body. Ex. Urinary tract infection cause by, , E.coli., , 59)

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- es —, 60 i4) BIOLOGICAL SCIENCE (MICROBIOLOGY), 5 6 to the infection., Mixed or polymicrobial Infection; More than one kind of microorganism contribute, Eg. Gaseous gangrene, » sta f patient.|t is also, Nosocomial infection: These are infections acquired in hospitals during the stay of p, , called hospital induced infection, Primary infection: Initial or first time infection with a host., Re-infection: Subsequent infection by the same parasite in the host., ither directly or indirectly via a vector., , Zoonosis: Infectious diseases transmitted from animals to man e, , A. SOURCES & TYPES OF INFECTION, NOSOCOMIAL INFECTION, I.CLASSIFICATION OR TYPES OF INFECTION, , 1. Primary Infection: The initial or first infection caused by an infecting organism., , Secondary Infection; When the body resistance of host is lowered by pre-existing infectious disease,, , a new organism may set up a disease, called secondary infection., , Reinfection: Subsequent infection by the same organism is called reinfection., , Inapperant or subclinical infection ; An infection that does not cause or produce any detectable, , nN, , manifestation is known as inapperant or subclinical infection., y remain in dormant (latent) form in, , 5. Latent infection: Following infection, some pathogenes ma n ) ', host tissues & when host resistance is lowered, they multiply & produce clinical disease. Such infection, , is called latent infection., Cross infection; When a new infection from patient or healthy staff carrier is set up an already, , diseased person, it is called cross infection., Hospital acquired or nosocomial infection: Cross infection acquired in hospitals is called nosocomial, , infection., Atypical infection: Infection where the typical or characteristic clinical manifestations of a disease, , are lacking is called atypical infection., Focal infection: A condition in which an infection at localised sites produces a general effect in body, , is called focal infection., , latrogenic or physician induced infection: The infection that results from unsterilized, , 10., instrumentation, drug therapy, handling infective specimen or any diagnostic procedure by laboratory, , staff., 11. Acute infection; An infection which lasts for a relatively short time (few days to few weeks) e.g.,, measles., , Chronic infection: An infection which lasts for a long time (over months & years) e.g. TB., , 12., Auto infection: An infection that occurs between two sites on the same host., , 73;, 14., 15., 16., , Mixed infection: An infection caused by two or more organism., , Masked infection: An infection is known to occur but the infectious agent cannot be demonstrated., Opportunistic infection: An infection with organisms which are normally harmless but become, pathogenic when the body’s defense mechanisms are compromised.

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INFECTION AND iTS TRANSMISSION, , ol, ent infection An infec, , ection in whi ; a, ve ch the infec tious, , 18. Supe, , , , 17. Pate, , agent can be demonstrated in disc harges of, rinfection Ase, , with another agent,, 19, Terminal infe., , cond infection Occurring, , ‘Nan animal which is already experiencing an infection, , ction: An, , acute infection occurring, 20. Transmissible, , near the end of a disease and often causing death, alled Contagious infection, , also c, , one animal to another An infection capable of being transmitted from, ae Person who harbors the Pathogenic organism without suffering from any disease is called, Types:, , 1. — carrier: q carrier who harbors the Pathogen but has never suffered from disease caused by, 2., , Temporary Carrier: a Carrier in whi, , Chroni ier: far . ; P es ;, Ps ad carrier in which carrier state lasts for indefinite period of several years or sometimes, rest of life., , ch carrier state lasts for less than 6 months., , Paradoxical carrier: q Carrier who acquires pathogen from another carrier., Contact carrier: 4 Carrier who acquires Pathogen from a patient., Convalescent carrier: Carrier who has recovered from the disease but continues to harbor pathogen, in his body., , ILSOURCES OF INFECTION, , Infection may be acquired endogenously (infection caused by body’s own normal flora) or exogenously, (infection caused by organism from source outside the body)., , A. Endogenous sources: These sources lead to endogenous or autoinfection. The source of infection is, , body’s own normal flora which may behave as pathogens outside their normal natural habitat e.g.,, , E.coli, a normal flora of intestinal tract may cause urinary tract infection, Strep. viridans, a normal flora, of mouth may cause infective endocarditis., , B. Exogenous sources:, , 1. Man (cases & carriers) : an is himself the commonest source of infectoin who may be a patient or, , a carrier., , Patient: Infections like AIDS, syphilis, gonorrhea, pulmonary tuberculosis, leprosy, Pertussis, hepatitis B,, mumps, measles, polio, influenza may be acquired exclusively from patients suffering from these diseases., , Carriers: Carriers also serve as important sources of infection €.g., meningococcal meningitis may be, acquired by a person which becomes contact carrier (carrier who acquires pathogens from patient)., , 2. Animals (cases & carriers) :There are some pathogens which are capable of causing disease in both, man & animals. Therefore, animals may act as source of infection of such diseases which may be, acquired by direct contact with animal, animal bite or ingestion of contaminated meat & milk from, such diseased animal. The infection in animals may be asymptomatic & these animals may serve as, reservoirs of human infection. Infectious diseases transmitted from animals to man (either directly, or indirectly via a vector) are called ‘zoonosis’ & include;

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an, , 62, , *U BIOLOGICAL SCIENCE (MICROBIOLOGY), , > , oisonin, Bacterial Bubonic plaque bovine tuberculosis, anthrax, salmonella food poisoning, , Viral Rabies, yellow fever, , Rickettsial Murine typhus, , Fungal Microsporium canies (Zoophilic dermatophytes), Protozoal Leishmaniasis, Helminthic Hydatid cyst In Echinococcosis (dog tape worm), , Insects: The diseases caused by insects are called arthropod borne diseases & the insects, transmitting pathogens are called ‘vectors’. Blood sucking insects like mosquito, ticks, mites, flies,, lice act as source of number of human & animal infection., , Soil: Soil may serve as important source of parasitic infection like round-worm & hook-worm infection., Spores of tetanus & gas gangrene remain viable in soil for several decades & serve as source of, infection. Histoplasma capsulatum causing histoplasmosis & some bacteria like Nocardia asteroides, , causing nocardiasis also survive in soil & then cause human infection., , Water: Water is also an important source of infections like Shigellosis (bacillary dysentery), cholera,, polio, hepatitis A & E, typhoid & number of parasitic diseases., , Food: Contaminated food acts as source of organisms causing food poisoning, gastroenteritis,, diarrhea, dysentery., , Ill. NOSOCOMIAL OR HOSPITAL-ACQUIRED INFECTION(HAI), , Hospital acquired or nosocomial infections are defined as infections developing in patients after admission, to the hospital, which were neither present nor in incubation at the time of hospitalization. Infection, that first appears between 48 hours & four days after admission are usually considered nosocomial, infections., , i., , COMMON HOSPITAL-ACQUIRED INFECTIONS, , Urinary tract infection: This is the most common nosocomial infection, 80% of infection are associated, , with catheterization or instrumentation of urethra, bladder or kidneys. The bacteria responsible, , arise from the gut flora (E.coli) or acquired in hospital (Klebsialla)., , Nosocomial pneumonia: It is the second most common type of HAI and occurs in several different, , patient groups. The most important are patients on ventilators in intensive care units. Microorganisms, , (Haemophilus influenza, Strep.pneumonia, Staph. aureus, Klebsiella, Proteus, Serratia, Enterobacter), are easily introduced into the throat by treatment procedures performed to treat respiratory illnesses., The infecting microorganisms can come from contaminated equipment or the hands of health care, workers as procedures are conducted such as respiratory intubation, suctioning of material from the, throat and mouth, and mechanical ventilation., , Surgical site infection (wound infection & skin sepsis) : Incidence of post-operative infection is, much higher in elderly patients. The infection is acquired usually during the operation itself; either, exogenously (e.g., from air, medical equipment, surgeon or other staff), endogenously from the skin, flora or rarely from blood used in surgery. Staph. aureus is the predominant pathogen followed by, E.coli, Proteus, Enterococcus, certain anaerobes & Staph. epidermis.

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INFECTION AND ITS ; ; *, TRANSMISSION 63 _ ail, , 4. Nosocomial bacteraemi, (approximately 596, intravascular de, , a: These infections repres, , sent a small proportion of nosocomial infections, ) but ease fatality rates, , sare high Infection may occur at the skin entry site of the, svice >, , ce, or in the subcutaneous path of the catheter (tunnel infection), SYMPTOMS OF HAs: Feveris often the, rapid breathing, ment, count. Patients with, , first sign of infection, Other symptoms and signs of infection are, al confusion, low blood pressure, reduced urine output, anda high white blood cell, emcee i 2 | may have pain while urinating and blood in the urine (uremia). Symptoms of, P ay include difficulty in breathing andinability to cough. A localized infection begins with, swelling, redness, and tender Ness on the skin or around a surgical wound or other open wounds, which, can progress rapidly to the destruction of deeper layers of muscle tissue, and eventually sepsis., , CAUSES OF HAls : All hospitalized patients are at risk of acquiring an infection from their treatment or, SHieSty Some patients are at Greater risk than others, especially young children, the elderly, and persons, with compromised immune systems. The risk factors for hospital-acquired infections in children include, parenteral nutrition (tube or intravenous feeding), the use of antibiotics for more than 10 days, use of, invasive devices, poor Post-operative status, and immune system dysfunction. Other risk factors that, increase the opportunity for hospitalized adults and children to acquire infections are:, , *A prolonged hospital stay., , * Severity of underlying illness., , ¢ Compromised nutritional or immune status., , * Use of indwelling catheters., , ¢ Failure of health care workers to wash their hands before procedures., , * Prevalence of antibiotic-resistant bacteria from the overuse of antibiotics., DIAGNOSIS OF HAls: Diagnosis of a hospital-acquired infection is determined by:, i. Evaluation of symptoms and signs of infection., , ii. Examination of wounds and catheter entry sites for redness, swelling, or the presence of pus or an, abscess., , ili. A complete physical examination and review of underlying illness., , iv. Chest X-ray may be done when pneumonia is suspected to look for the presence of white blood cells, and other inflammatory substances in lung tissue., , v. Laboratory tests including;, * Complete blood count to look for an increase in white blood cells., * Urine analysis (urinalysis) to look for white cells or evidence of blood in the urinary tract., , * Cultures of the infected area, blood, sputum, urine, or other body fluids or tissue to find the, causative organism., , TREATMENT OF HAls: Treatment depends upon the organisms responsible for infection which is, established in diagnosis and it varies for different organisms., ¢ Bacterial infections: The isolated organism is tested for sensitivity to a range of antibiotics., While waiting for these test results, treatment may begin with common broad spectrum, antibiotics such as penicillin, cephalosporins, tetracyclines or erythromycin. Since bacteria are