NOSOCOMIAL INFECTIONSNOSOCOMIAL INFECTIONS

Prof. Dr. N. Ribarova, MDProf. Dr. N. Ribarova, MD

DefinitionDefinition: Nosocomial infection (NI) : Nosocomial infection (NI) is every infectious process, appearing is every infectious process, appearing during hospital stay, despite its clinical during hospital stay, despite its clinical picture, carrier status and time of picture, carrier status and time of manifestation - during hospital treatment manifestation - during hospital treatment or after discharge.or after discharge.

Infections that develop in outpatient Infections that develop in outpatient departments, day clinics or other closed departments, day clinics or other closed human groups such as in nursing human groups such as in nursing houses or orphanages and are houses or orphanages and are associated to medical or dental associated to medical or dental procedures are nosocomial too.procedures are nosocomial too.

Acute infectious diseases that were Acute infectious diseases that were in incubation period before hospital in incubation period before hospital admittance are not considered as a NI.admittance are not considered as a NI.

Diseases, caused by opportunistic Diseases, caused by opportunistic microorganisms, without determined microorganisms, without determined incubation period, are regarded as a incubation period, are regarded as a NI, in case they developed 48-72 hours NI, in case they developed 48-72 hours after patient's admittance in the after patient's admittance in the hospital ward.hospital ward.

Nosocomial infections are topic of the Nosocomial infections are topic of the day of contemporary health care. Their day of contemporary health care. Their importance is determined by the relatively importance is determined by the relatively large number of patients with NI - 2-15 large number of patients with NI - 2-15 %of all admitted patients and significantly %of all admitted patients and significantly higher lethality - up to 80 %. Besides the higher lethality - up to 80 %. Besides the health costs, there are considerable health costs, there are considerable damages of economic, social and ethical damages of economic, social and ethical character.character.

Short historical review: Short historical review: The The problem with NI emerged with the problem with NI emerged with the appearance and development of hospital appearance and development of hospital institutions. The foun-dations of institutions. The foun-dations of contemporary manage-ment of NI was contemporary manage-ment of NI was laid by Hungarian doctor J. Semmelweis, laid by Hungarian doctor J. Semmelweis, 1846. N.I.Pirogov (1810-1881) recom-1846. N.I.Pirogov (1810-1881) recom-mended a system of "segregation" to mended a system of "segregation" to stop NI. J. Lister (1827-1921) is the stop NI. J. Lister (1827-1921) is the founder of antiseptics (usage of founder of antiseptics (usage of pulverized carbolic acid and gauzes with pulverized carbolic acid and gauzes with carbolic acid during operations).carbolic acid during operations).

With the invention of sulfonamides, and With the invention of sulfonamides, and later antibiotics, new opportunities for later antibiotics, new opportunities for antimicrobial therapy of NI appeared. antimicrobial therapy of NI appeared. However soon disappointment appeared However soon disappointment appeared because of bacterial antibiotic resistance. because of bacterial antibiotic resistance. The selection of resistant microorganisms The selection of resistant microorganisms in the course of antibiotic and other in the course of antibiotic and other current chemotherapy, combined with the current chemotherapy, combined with the outburst of various diagnostic and outburst of various diagnostic and therapeutic interventions lead to changes therapeutic interventions lead to changes in the nature of NI.in the nature of NI.

Etiology: Etiology: A typical feature of contemporary A typical feature of contemporary NI is that their etiological agents are NI is that their etiological agents are opportunistic microorganisms that are a part opportunistic microorganisms that are a part of patient's own microbial flora. of patient's own microbial flora.

Up to 50 % of NI in the last decades are Up to 50 % of NI in the last decades are caused by Gram-negative microorganisms caused by Gram-negative microorganisms from the family Enterobacteriaceae, genus from the family Enterobacteriaceae, genus Escherichia, Klebsiella, Enterobacter, Serratia, Escherichia, Klebsiella, Enterobacter, Serratia, Proteus, Providencia; genus Pseudomonas Proteus, Providencia; genus Pseudomonas and Acinetobacter from the group of Gram-and Acinetobacter from the group of Gram-negative non-fermenting aerobes.negative non-fermenting aerobes.

Gram-positive cocci from genus Gram-positive cocci from genus Staphylococcus and Streptococcus Staphylococcus and Streptococcus cause 20-50 % of NI, various viruses - cause 20-50 % of NI, various viruses - about 15-20 %, the rest NI are caused about 15-20 %, the rest NI are caused by non-spore rising anaerobes, fungi, by non-spore rising anaerobes, fungi, opportunistic bacteria and rarely by opportunistic bacteria and rarely by protozoa.protozoa.

The NI etiology is highly influenced by The NI etiology is highly influenced by the changes in microbial population, the changes in microbial population, caused by broad and not always caused by broad and not always reasonable antibiotic administration. reasonable antibiotic administration. Therefore in the "high risk" hospital wards Therefore in the "high risk" hospital wards (neonatology, obstetrics, general surgery, (neonatology, obstetrics, general surgery, urology, intensive care units) circulate the urology, intensive care units) circulate the so-called "hospital" strains, that are highly so-called "hospital" strains, that are highly virulent, invasive and with multiple virulent, invasive and with multiple resistance to the used antibiotics and resistance to the used antibiotics and disinfection solutions.disinfection solutions.

NI etiological agents are characterized NI etiological agents are characterized by significant stability in surrounding by significant stability in surrounding environment. Gram-positive cocci can environment. Gram-positive cocci can stand dehydration for long periods on stand dehydration for long periods on surfaces, while Gram-negative survive surfaces, while Gram-negative survive in humid conditions for months.in humid conditions for months.

Pathogenesis: Pathogenesis: The polietiology of The polietiology of NI creates prerequisites for various NI creates prerequisites for various changes in the host organism.changes in the host organism.

Entry siteEntry site for the infection can be the for the infection can be the skin and mucous membranes, respiratory skin and mucous membranes, respiratory and digestive system, the urogenital tract. and digestive system, the urogenital tract. Very often the etiology agent is a part of Very often the etiology agent is a part of the own bacterial flora (in cases with the own bacterial flora (in cases with endogenous infection). Typical for NI is endogenous infection). Typical for NI is the creation of additional, uncommon the creation of additional, uncommon entry sites of the infection as a result of entry sites of the infection as a result of multiple diagnostic and therapeutic multiple diagnostic and therapeutic invasive procedures.invasive procedures.

The incubation periodThe incubation period of of NI varies from few hours to 30 NI varies from few hours to 30 and more days according to the and more days according to the nosology unit.nosology unit.

Classification scheme of J.Gamer (1970), Classification scheme of J.Gamer (1970), according to which NI are separated into 7 according to which NI are separated into 7 groups based on clinical criteria:groups based on clinical criteria:

Infections of respiratory systemInfections of respiratory systemInfections of digestive systemInfections of digestive systemInfections of urogenital systemInfections of urogenital systemInfections of cardiovascular systemInfections of cardiovascular systemInfections of skin and subcutaneous tissuesInfections of skin and subcutaneous tissuesInfections of sensory organsInfections of sensory organsOther infections (classic acute infectious Other infections (classic acute infectious

diseases)diseases)

Sources of infection:Sources of infection: Sick or carriers among the medical staff, Sick or carriers among the medical staff,

students, residents, mothersstudents, residents, mothersof sick childrenof sick children

New patients, carriers or patients in New patients, carriers or patients in incubation period of an infectiousincubation period of an infectiousdiseasedisease

New patients with mixed or undistinguished New patients with mixed or undistinguished infectioninfection

Patients with evident infection or in carrier Patients with evident infection or in carrier statestate

In current NI 30-50 % of cases In current NI 30-50 % of cases represent endogenous infection represent endogenous infection (autoinfection). It is caused by (autoinfection). It is caused by microorganisms belonging to patient's microorganisms belonging to patient's own intestinal or skin flora that reached own intestinal or skin flora that reached normally sterile areas or were activated normally sterile areas or were activated by administered therapy (antibiotics, by administered therapy (antibiotics, corticosteroids, cytostatics).corticosteroids, cytostatics).

From an epidemiological standpoint From an epidemiological standpoint as a source for infection most as a source for infection most important is the medical personnel that important is the medical personnel that become carriers of highly virulent, become carriers of highly virulent, strongly invasive and with multiple strongly invasive and with multiple resistance "hospital" strains of resistance "hospital" strains of microorganisms.microorganisms.

Mechanisms to pass the infection: Mechanisms to pass the infection: The mechanisms are various. Practically The mechanisms are various. Practically in hospital environment all 4 mechanisms in hospital environment all 4 mechanisms to pass an infection are possible to pass an infection are possible (airborne, blood, fecal-oral and (airborne, blood, fecal-oral and contact). There are various factors for contact). There are various factors for transmitting the infection with transmitting the infection with predominance of the contact mechanism. predominance of the contact mechanism. Most important are the staffs' hands, Most important are the staffs' hands, medical equipment and instruments.medical equipment and instruments.

Population susceptibility and Population susceptibility and immunity: immunity: Typical for the current Typical for the current epidemic process of NI is that large epidemic process of NI is that large number of hospital population is number of hospital population is vulnerable to infections.vulnerable to infections.

Various etiology leads to different in Various etiology leads to different in terms of intensive immunity. Infections, terms of intensive immunity. Infections, caused by opportunistic bacterial flora, caused by opportunistic bacterial flora, the developed humoral and cell-the developed humoral and cell-mediated (phagocytic) immunity is of mediated (phagocytic) immunity is of short duration. Recurrences of the short duration. Recurrences of the infection are possible.infection are possible.

Characteristics of the Characteristics of the epidemiology process: epidemiology process: Current NI Current NI represent a problem for economically represent a problem for economically developed countries.developed countries.

NI prolong hospital stay, raise NI prolong hospital stay, raise treatment's cost, decrease the utilization treatment's cost, decrease the utilization of hospital services and effectiveness of of hospital services and effectiveness of health care system, cause suffering, health care system, cause suffering, disability and premature death. disability and premature death. Ultimately they significantly affect Ultimately they significantly affect national economy.national economy.

Among the registered NI most Among the registered NI most common are the infections of upper common are the infections of upper respiratory tract -40%, followed by respiratory tract -40%, followed by pulmonary NI - 13%, surgical pulmonary NI - 13%, surgical wound infections - 12 %, wound infections - 12 %, urogenital infections - 10 %, urogenital infections - 10 %, cutaneous NI - 8 %, intestinal cutaneous NI - 8 %, intestinal infections - 6 %.infections - 6 %.

Nowadays major prerequisites for the Nowadays major prerequisites for the appearance and development of NI are the appearance and development of NI are the following:following:

Constantly increasing stream of patients in Constantly increasing stream of patients in health care institutions as a result of health care institutions as a result of population aging, chronic diseases, population aging, chronic diseases, accessibility of medical care, broadened accessibility of medical care, broadened health culture.health culture.

Hospital overpopulationHospital overpopulation Concentration of multiple sources of Concentration of multiple sources of

infection and circulation of "hospital infection and circulation of "hospital strains" of microorganismsstrains" of microorganisms

Various artificial ways for additional Various artificial ways for additional contamination - diagnostic andcontamination - diagnostic andtherapeutic manipulations and therapeutic manipulations and interventionsinterventions

Status of the sanitary care and hygiene, Status of the sanitary care and hygiene, management, culture ofmanagement, culture ofmedical caremedical care

The intensity of epidemiological process The intensity of epidemiological process of NI is manifested by sporadic cases and of NI is manifested by sporadic cases and epidemic outbreaks, and rarely by epidemics.epidemic outbreaks, and rarely by epidemics.

AntiepidemicAntiepidemic measures:measures:2.2. Regarding the patientRegarding the patient

- Well-timed and proper diagnosis- Well-timed and proper diagnosis- Effective sanitary preparation before- Effective sanitary preparation before

admittance to the wardadmittance to the ward- Specific therapy- Specific therapy

3.3. Regarding the people in contactRegarding the people in contact- Microbiological, clinical and other tests- Microbiological, clinical and other tests- Active immunization- Active immunization- Specific means for passive prophylactics- Specific means for passive prophylactics

4.4. Regarding the surrounding environmentRegarding the surrounding environment- Disinfection, Sterilization- Disinfection, Sterilization

Measures for Prophylactics:Measures for Prophylactics: Detection, registration and report of NIDetection, registration and report of NI Improvement of hospital equipment and Improvement of hospital equipment and

utilities for treating patientsutilities for treating patients Antiseptics and aseptics of all medical Antiseptics and aseptics of all medical

proceduresprocedures Clinical and microbial service and Clinical and microbial service and

antimicrobial therapyantimicrobial therapy Organization and management of activities for Organization and management of activities for

prophylactics and treatment of NI, for training prophylactics and treatment of NI, for training of the medical staff about NI.of the medical staff about NI.