Transcript Lesson - Lake–Sumter State College

Lesson 9
Nosocomial Infections
“Healthcare-Related Infections”
March 19, 2015
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
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
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~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
• 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
• 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?
• 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
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!!!!
• 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)
• 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.
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
• 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.
• 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)
Conjugation
• 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)
Transduction
• 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
Transformation
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.
Nosocomial Infections and Their
Antibiotic Resistance
Coagulase-negative
staphylococci
S. aureus
15%
Percentage
Resistant to
Antibiotics
89%
15%
80%
Enterococcus
10%
4–71%
15–25%
3–32%
13%
Not reported
Percentage of
Total Infections
Gram-negative rods
C. difficile
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
• 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
• 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
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)
• 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)
Microorganisms in
hospital environment
Compromised host
Nosocomial
infection
Chain of transmission
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
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
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
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
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
• 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
• Analytical: analyzes a particular disease to
determine its probable cause
– Case control method—epidemiologist looks for
factors that might have preceded the disease
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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)
• 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)
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
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
• 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