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Lesson 9 Nosocomial Infections “Healthcare-Related Infections” March 19, 2015.

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Presentation on theme: "Lesson 9 Nosocomial Infections “Healthcare-Related Infections” March 19, 2015."— Presentation transcript:

1 Lesson 9 Nosocomial Infections “Healthcare-Related Infections” March 19, 2015

2 Hospital Acquired Infections (Nosocomial Infections) Nosocomial infections—are infections whose development is favored by a hospital environment – Acquired by a patient during a hospital visit – Infections developing among hospital staff

3 Centers for Disease Control and Prevention Statistics CDC estimates that 1.7 million people acquire infections during their hospital stay – Affects between 5-15% of all hospital patients Roughly 100,000 deaths are associated with nosocomial infections – ~36,000 via pneumonia – ~31,000 via bloodstream infections – ~13,000 via urinary tract infections – ~9,000 via surgical site infections – ~11,000 via infections of other sites

4 The term nosocomial infections has been updated to health care-associated infections to include other care-giving places – Same day surgical centers – Ambulatory outpatient health care clinics – Nursing homes – Rehabilitation facilities – In-home health care environments

5 Joseph Lister developed antiseptic surgical practices and techniques. (Father of Modern Surgery) – Utilized phenol to sterilize equipment – “Scrubbing In” Greatly reduced the rate of nosocomial infections (commonly known as “ward fever”) In spite of the advances of sterilization techniques, the rate for nosocomial infection has increased in the past 20 years – What could account for this increase in infections in spite of increased sterilization practices?

6 Nosocomial infections are the result of three major factors 1.Microorganisms being present in the hospital environment 2.Compromised status of the host 3.Chain of transmission

7 Microorganisms in the Hospital Although typically sterile, the hospital can serve as a reservoir for several pathogens – Normal microbiota of the human body act as opportunistic pathogens to other patients Compromised immune systems Therapy that affect normal function (antibiotics killing natural flora) – Most nosocomial infections are caused by human microbiota!!!!

8 Nosocomial infections are mostly caused by a fungal or bacterial pathogen – S. aureus (most frequent cause of pneumonia) – Enterococcus spp. (Surgical wound infections) – E. coli (Pneumonia and surgical wound infections) – P. aeruginosa (Pneumonia and surgical wound infections) – Candida albicans (Urinary tract infection and sepsis)

9 The causative agents of hospital acquired infections have cycled through the years – During the 40-50’s, the most nosocomial infections were caused by gram (+) microbes S. aureus – In the 70’s gram (-) rods were the predominant cause of nocosomial infections E. coli and Pseudomonas aeruginosa – 1980’s antibiotic-resistant strains of gram (+) microbes were predominant S. aureus Enterococcus spp.

10 Antibiotic Resistance Antibiotic resistance has become a major concern regarding nosocomial infections – Organisms that are resistant to more than one antibiotic is referred to as a multi-drug resistant bacteria (MDR) – Resistance comes from repeated exposure of a microbe to antibiotics “More you use antibiotics; more resistance will form” 1.Spontaneous mutation of bacterium’s genome 2.DNA transfer from a antibiotic resistant bacterium to a antibiotic susceptible gene

11 Bacterial genomes mutate naturally – A subset of the bacterial population will develop resistance to antibiotics – Those not killed are now free to multiply without any competition from the sensitive strains.

12 DNA transfer also confers a bacteria with antibiotic resistance DNA can be transferred to bacteria via three mechanisms – Conjugation—transfer of bacterial DNA via direct contact or through an appendage (sex pili)

13 Conjugation

14 DNA transfer also confers a bacteria with antibiotic resistance DNA can be transferred to bacteria via three mechanisms – Conjugation—transfer of bacterial DNA via direct contact or through an appendage (sex pili) – Transduction—transfer of bacterial DNA via viruses (bacteriophages—viruses that infect bacteria)

15 Transduction

16 DNA transfer also confers a bacteria with antibiotic resistance DNA can be transferred to bacteria via three mechanisms – Conjugation—transfer of bacterial DNA via direct contact or through an appendage (sex pili) – Transduction—transfer of bacterial DNA via viruses (bacteriophages—viruses that infect bacteria) – Transformation—direct uptake of bacterial DNA through the cell membrane

17 Transformation

18 Affects of Antibiotics Antibiotics can also wipe out “friendly” bacteria, which would otherwise compete with the resistant strain for resources. Increase resistance in harmless bacteria which can, under certain conditions such as in an immune suppressed patient, become aggressive and cause infection.

19 Percentage of Total Infections Percentage Resistant to Antibiotics Coagulase-negative staphylococci 15%89% S. aureus15%80% Enterococcus10%4–71% Gram-negative rods15–25%3–32% C. difficile13%Not reported Nosocomial Infections and Their Antibiotic Resistance

20 Compromised Host Compromised host—a person whose resistance to infection is impaired – Disease – Therapy – Injury Two principal conditions that compromises the host – Broken skin/mucous membranes – Suppressed immune system

21 Skin and mucous membranes function as a physical barrier to pathogens – Compromise to this barrier allows the pathogen to enter the body Burns, wounds, and trauma when a patient checks in Injections, invasive diagnostic procedures, intravenous therapy, urinary catheters – Pathogens can proliferate on medical devices Results from inadequate cleaning of medical equipment

22 Patients that are immunocompromised are at a higher risk in contracting a hospital-acquired infection – Healthy individuals have T cells (T lymphocytes) that directly kill the bacteria – B cells (B lymphocytes) develop antibodies that ward off infections A weakened response to the pathogen allows the pathogen to grow and proliferate at rapid rates Drugs, radiation therapy, steroid therapy, burns, diabetes, leukemia, kidney disease, stress, and malnutrition all contribute to a weakened immune system

23 Chain of Transmission There are two principal routes of transmission of hospital-acquired infections 1.Direct contact from health-care provider to patient or patient to patient contact 2.Indirect contact transmission through fomites or ventilation system (airborne transmission)

24 Person-to-person contact – Hospital personnel can transmit microbes to a patient when changing dressing (wound care) Transmission via fomites – Kitchen workers carrying Salmonella, can transmit it to the patient’s food – Medical equipment can serve as fomites Urinary catheters Needles Respiratory aids (ventilators)

25 Microorganisms in hospital environment Chain of transmission Nosocomial infection Compromised host

26

27 Prevention of Nosocomial Infections Hospitals implement different techniques in an effort to control nosocomial infections – Sterilization of equipment Disinfecting is not sufficient – Proper Protective Equipment Aprons, face shields, gloves – Surface Sanitation Touch surfaces common vehicle of pathogen transmission Implementation of antimicrobial surfaces (usage of Copper) – Handwashing According to the CDC, hand-washing is the single most important means of preventing the spread of infection

28 Emerging Infectious Diseases Diseases that are new, increasing in incidence, or showing a “potential” to increase in incidence in the near future are labeled as Emerging Infectious Diseases – Roughly 75% of emerging diseases are zoonoses and are mainly viral in origin – Variety of factors that contribute to the emergence of new infectious diseases

29 Emerging Infectious Diseases Contributing factors – Genetic recombination E. coli O157, avian influenza (H5N1) – Evolution of new strains V. cholerae O139 – Inappropriate use of antibiotics and pesticides Antibiotic-resistant strains – Changes in weather patterns/climate Hantavirus

30 Emerging Infectious Diseases Modern transportation (traveling) – West Nile virus, Ebola, MERS (middle eastern respiratory syndrome) Ecological disaster, war, and expanding human settlement – Spread of V. cholera after earthquakes in Haiti Animal control measures – Over population of reservoirs (deers, raccoons, nutria rat) Public health failure – Failure of adults to get proper vaccination

31 EPIDEMIOLOGY Epidemiology—The study of where and when diseases occur and how they are transmitted in populations Epidemiologists uses three basic types of investigations when analyzing the occurrence of a disease – Descriptive – Analytical – Experimental

32 Descriptive: collection and analysis of data – Retrospective—looking “backward” after the episode has ended Ex. John Snow looking for the cause of the cholera outbreak in London in 1849 (water pump) – Prospective—looking “forward” to see if disease develops Epidemiologist looks at a disease-free group and monitors there habits to see if disease occurs

33 Analytical: analyzes a particular disease to determine its probable cause – Case control method—epidemiologist looks for factors that might have preceded the disease Age Sex Socioeconomic status Location – Cohort method—group of people who have the disease is compared to a group that is disease-free Comparison of one group of people who have received blood transfusions vs. a group that has not received blood transfusions. (incidence of hepatitis B virus)

34 Experimental: experiments to test the hypothesis regarding the characteristics of a particular disease – Assumed effectiveness of a drug Experimental drug vs. placebo (substance that has no effect)

35 Epidemiology Centers for Disease Control and Prevention (CDC) – Collects and analyzes epidemiological information in the United States – Publishes Morbidity and Mortality Weekly Report (MMWR) – www.cdc.gov

36 The CDC Morbidity: incidence of a specific disease Mortality: deaths from notifiable diseases – Notifiable diseases are diseases that are required to be reported to the government by law – http://www.cdc.gov/mmwr/preview/mmwrhtml/mm6053 a1.htm http://www.cdc.gov/mmwr/preview/mmwrhtml/mm6053 a1.htm Morbidity rate: number of people affected in relation to the total population in a given time period Mortality rate: number of deaths from a disease in relation to the population in a given time


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