Bacteria 2 Flashcards
Biofilms - most bacteria live how
NOT planktnically - they are not freely moving
Most are sessile and adherent to a surface or to other bacteria as part of a biofilm
Biofilms are what
bacteria encased in a exopolymeric substance (polysaccharide, DNA, protein…) of their own making
Biofilms are found where
throughout nature on surfaces that are commonly moist/wet
Biofilms - cells
cells in a biofilm are different than planktonic cells
Biofilms - cells - how are they different
Altered metabolism, generally slower
Increased resistance to antibiotics
Increased genetic exchange (inc likelihood of antibiotic resistance transfer)
Resistant to disinfection - increased organic matter and decreased diffusion
Host-Microbe Interactions - Medical microbiology
Study of dynamic interaction between microbes and the human host
Host-Microbe Interactions - Symbiosis
Close and prolonged association between 2 or more organisms of different species
Host-Microbe Interactions - Commensalism
Shelter and food
Ex - Bacteroides spp - human large intestine
Host provides environment and nutrition
Bacteria ferment digested food
Large bacterial population
Harmful if tissue damaged, gut flora changes or immunity reduced
Host-Microbe Interactions - Mutualism
Reciprocal benefit Bacteroids spp - cattle rumen Host provides environment and nutrition Bacteria metabolize food into fatty acids/gasses Host uses fatty acids as energy source
Host-Microbe Interactions - Parasitism
Unilateral benefit
Helicobacter pylori - human stomach
Host provides environment
Local invasion of the stomach epithelium by bacteria leading to ulcers, stomach bleeding, potentially cancer
Niche - types
shelter (physical space in/on the body)
food (nutrients)
Niches and normal bacteria - normal micobiota (flora)
Often commensal or mutual symbionts adapted to specific niches
Tend to avoid directly injuring the host
Can be beneficial to the host - compete with pathogens for niche (competitive exclusion), can produce toxins that harm pathogenic microorganisms
Normal microbiota - fetus vs. neonate
Fetus - sterile
Neonate - if vaginal delivery is colonized with birth, if C section is rapidly colonized after birth with skin/skin contact
Normal microbiota - colonized sites
Skin
Mucosa
Intestine
Urogenital tract
Normal microbiota - normally sterile
Internal organs and tissue
Cervix
Middle ear
Urinary bladder
Normal microbiota - childhood vs. normal healthy adult vs. elderly
Child - developing immunity, exposure to new microbes
Healthy adult - developed immunity
Elderly - immune senescence, inc risk of infection
Resident vs. Transient Microbiota
Resident = long term members of the bodys normal microbiota Transient = organisms that attempt to colonize to body but are unable to remain
Transient microbiota - are unable to remain due to
Competition from resident microbiota
Elimination by body immune system
Physical or chemical changes within the body that discourage growth
Resident (normal) microbiota - Skin
Staphylococcus epidermidis - skin, nose, external ear canal
Gram pos cocci, in clusters
Infections associated with prosthetic devices and IV catheters
Common contaminant of blood cultues!!!
Transient microbiota - ex
Group A strep (GAS) - streptococcus pyogenes
Gram pos cocci, in chains
Transiently colonize oropharynx of children and young adults in absence of clinical disease
Causative agent of strep throat
Pathogens = what
any microorganism that has the capability to cause disease
Strict pathogens
Organisms always associated with disease
If in a person, it will cause disease
Ex - TB, gonorrhea, rabies
Opportunistic pathogens
tend to be members of the normal microbiota
take advantage of preexisting conditions such as immunosuppression to cause disease
Are most infectious disease of humans caused by strict pathogens or opportunistic?
OPPORTUNISTIC!
We are exposed to them all the time!
Ex of opportunistic infections
Contamination of IV cath Wound/surgical site infection Bacterial endocarditis Aspiration pneumonia UTI Pseudomembrane colitis Otitis media
Carrier state - carrier =
An asymptomatic individual who is host to a pathogen
Has the potential to transmit the pathogen to others
Condition of being a carrier may be transient or (semi) permanent depending on what one is carrying and how it can be cleared/removed
Pathogenicity and Virulence
Often used interchangeable
Pathogenicity = ability of a microorganism to cause disease
Virulence = a measurement of pathogenicity (how severe the disease might be)
Virulence factors
Factors (toxins) produced by organisms that enable it to infect, cause disease, and/or kill a host
Events associated with infection
entry into the host
adhesion and colonization
pathogenic action of bacteria
mechanisms for escaping hose defenses
Entry into the host (and shedding)
Transplacental (mother to fetus) Secretions Stool (fecal to oral) Skin (cuts) Blood Zoonotic (animal to human) Arthropod
Entry into host - barriers
Mechanical (skin, cilia) Enzymatic (lysozyme) Chemical (acidic pH) Immunity Commensals (niche environment) Physical (sheer forces, peristalsis)
Sterilization
Destroy all microbial forms including bacterial spores
Disinfection
Destroy most microbial forms
Bacterial spores and other resistant organisms (viruses, fungi) might remain viable
Subdivided into high, intermediate and low level agents
Antisepsis
Disinfectants used on skin or other living tissue to inhibit or eliminate microbes; no sporicidal action is implied
Pasteurization
Heating milk or other liquids to destroy microorganisms
Sterilization destruction of what
complete destruction or elimination of viable organisms
Nonselective and harsh! Inactivates mycobacteria sports, and prions
Sterilization - common methods
Heat - moist or dry
Radiation
Chemicals
Filtration
Sterilization - moist heat
Autoclaving (pressure cooker)
MOA - denatures proteins, causes single strand breaks in DNA, compromises membrane integrity
Kill spores
Is nontoxic
Used for items not damaged by hear, moisture, pressure
Sterilization - boiling
Boiling is NOT sterilization!!! It is a method of disinfection!
Sterilization - dry heat
MOA - protein denaturation, single stranded DNA breaks, compromises membrane integrity
Kills spores, non toxic
Used for metals, glass
Sterilization - ethylene oxide gas
Colorless, flammable gas
MOA - alkylates proteins, DNA and RNA
Kills spores, toxic/mutagenic - must dissipate gas
Used for moisture/heat sensitive items
Sterilization - radiation - UV light
Direct exposure required (only non-porous surface)
MOA - DNA damage
Sterilization - radiation - Ionizing radiation - irradiation
Exposure to radiation source
MOA - DNA damage, generation of oxidizing agents
Sterilization - filtration
Useful for removing bacteria and fungi from air, liquid
MOA - physical removal of bacteria
Disinfection
Killing most, but not all, viable organisms from surfaces
Disinfection - high class
Kills all microbial pathogens except large numbers of spores
Surfaces that cannot be sterilized (endoscope)
Disinfection - high class ex
Glutaridehyde
Concentrated hydrogen peroxide
Peracetic acid
Chlorine compounds (bleach)
Disinfection - intermediate class
Kills all mircrobial pathogens except spores
Surfaces unlikely to be contaminated with spores (laryngoscopes)
Disinfection - intermediate class - ex
Alcohols
Iodophors
Phenosis
Disinfection - low class
kills most bacteria and lipid enveloped viruses
Surface of non critical instruments - stethoscope
Disinfection - low ex
Quaternary ammonium compounds
Effectiveness of disinfectants - depends on
Surface/item to be disinfected Level of contamination Type of contamination Amount of organic matter present Concentration of disinfectant Duration and temperature of exposure
Antiseptics
Distinct subclass of disinfectants Does NOT kill bacterial spores
Reason for use - antiseptics
Reduce the number of microorganisms on the skin surface
Antiseptics - ex
Alcohols Phenolics Iodine Chlorhexidine Quaternary ammonium compounds Triclosan
Antiseptics - alcohol
Ethanol and Isopropanol - commonly used before venipuncture
MOA - denature proteins, cell membrane damage
Activity greater in presence of water (to a point)
Optimal range is 60-90% (hand sanitizer is in this range)
Antiseptics - Iodine
Most effective antiseptic
Recommended to be applied prior to vnipuncture or installation of IV cath
Antiseptic - Iodine - Iodophors
Iodine complexed with a solubilizing agent (povidone)
Considered the most stable/universally perferred iodine antiseptic
Antiseptic - Iodine - MOA
Quick penetration of cells, disruption of membrane and essential cell process
Antiseptic - Chlorhexadine
Broad antimicrobial activity - slow acting, residual activity
MOA - disrupts cell membranes
Newer solutions contain - alcohol, detergent
Some hospitals are using this over iodine for catheter installation
Antiseptic - Chlorhexadine - alcohol and detergent
Alcohol - inc effectiveness
Detergent - very effective for decontaminating skin, used commonly for surgical scrub in
Standard procedures
Assume every person is potentially infected or colonized
Hand hygiene before and after EVERY patient
Use protection when exposure to secretions is possible
Follow sharps guidelines
Hand hygiene
Avoid unnecessary contact with surfaces to avoid contamination
Visible hand contamination - wash with soap and water
Not visible - alcohol based hand sanitizer
Change gloves often if prolonged time with single pt
Do not wear artificial fingernails or have long nails
Washing hands vs. Alcohol based sanitizer
Washing hands will remove spores
Sanitizer will not kill spores
