Microbial Control

what is sterilization

destroys all microbes

• including endospores

• important in lab and medical procedures

what is disinfection

treat inanimate items

• destroys vegetative cells

• not endospores typically

what is antiseptic

treat living tissue

• external use (cut on the skin)

• minimize infection

what is an antibiotic used for

killing bacteria

• often internal but some topical

sanitize

lowers microbial numbers to safe public health levels

• not enough microbes present to cause a disease

• restaurants, hands, daycares, hotels

steps for cleaning

clean than sanitize

• remove visible dirt first

how does soup work

1. dissolves in water

2. surfactant ions orientate themselves in grease and water

3. process continues

4. cleaning complete

physical methods of microbes (5)

• heat (dry heat, boiling, pasteurize, autoclave)

• dessication (drying)

• cold

• radiation (uv, xray, gamma ray)

purpose of physical methods of microbes

minimizes microbial growth

• not necessarily sterile

• it’s okay if we eat some microbes

what is chemical methods

measures how resistant microbes are to chemicals

• not drug-resistance

what are the 3 top of microbes that are most resistant to chemicals

1. prions

2. endospores of bacteria

3. mycobacteria (acid-fast)

what are the 3 microbes that are least resistant to chemicals

1. Viruses without envelopes

2. Gram-positive bacteria

3. Viruses with lipid envelope

which would mean a microbes is easier to inhibit or kill with a certain chemical

more resistant - less resistant

more sensitive - less sensitive

more susceptible - less susceptible

more effective - less effective

what is antimicrobial therapy

how to treat the infection once it occurs

chemotherapeutic agents

• antimicrobial agents

antibiotics

• naturally made by microbes

chemotherapeutic agents

• synthetic drugs

made in the lab

what is selective toxicity

harm the microbes without harming the host too much

• destroy infection, not harm host

• magic bullet

broad spectrum

kills a broad range of bacteria

• used when we don’t know what the bacteria is

narrow spectrum

kills a specific bacteria

• know bacteria causing the problem

what is mode of action

• 5 ways

how the chemical kills the microbe

• inhibits cell wall synthesis

• disrupts the cell membrane’s function

• inhibits protein synthesis

• inhibits nucleic acid synthesis

• acts as antimetabolites

Antibiotic - Associated Diarrhea

• etiological agent

Clostridium difficile

• C diff

• Gram +

• anaerobe

• endospores

• exotoxins

• knocks out normal flora of gut

Antibiotic - Associated Diarrhea (C. diff)

• reservoir

endogenous

• in person’s gut

• normal flora doesn’t get it grow

environmental endospores

Antibiotic - Associated Diarrhea (C. diff)

• pathogenicity

opportunistic

• superinfection → destruction of normal flora allowing pathogens to flourish

• following broad-spectrum antibiotics

• loss of normal flora

• endospores survive and geminate (not affected by antibiotics)

Antibiotic - Associated Diarrhea (C. diff)

• pathogenesis

two exotoxins

1. inflammation

2. fluid loss (diarrhea)

Antibiotic - Associated Diarrhea (C. diff)

• pseudomembranous colitis

inflammation and damage of the colon

• can be fatal

• especially elderly

Antibiotic - Associated Diarrhea (C. diff)

• epidemiology

#1 cause of nosocomial diarrhea

Antibiotic - Associated Diarrhea (C. diff)

• symptoms

• diarrhea

• cramps

• fever

• perforation of colon possible (holes in colon)

Antibiotic - Associated Diarrhea (C. diff)

• diagnosis

isolate organism from stool

• identify toxins

• endoscopic observations of pseudomembranous in colon (colonoscopy)

Antibiotic - Associated Diarrhea (C. diff)

• treatment

stop antibiotics and see if symptoms resolve

• problem is caused by antibiotics

• normal flora can re-establish again

Antibiotic - Associated Diarrhea (C. diff)

• treatment (antibiotics)

targets active, veg cells (not the endospores)

1. metronidazole

   • targets anaerobes

2. vancomycin

Antibiotic - Associated Diarrhea (C. diff)

• treatment (exceptional cases)

fecal transplant

• restores normal flora

Antibiotic - Associated Diarrhea (C. diff)

• recurrences

due to germination of residual spores

• still spores left

• not due to drug resistance

• 25%

drug resistance

how the microbe evades

what is “drug resistance”

how the microbe evades the drug

• microbe > drugs

• microbe is not destroyed

different types of drug resistance

• microbe destroys the drug

• prevent the drug from entering the cell

• microbe pumps drug back out of the cell

• microbe changes its cellular target

how do microbes develop drug resistance

• gene may be acquired by mutations

mutations

• just occur, not on purpose

• antibiotics do not induce mutations

• antibiotics can create environment that favor the survival of mutant resistant organisms

gaining an R plasmid

• gain from other microbes

how does antibiotic misuse link to MDR

overuse of antibiotics leads to multiple-drug resistance

how can antibiotics be misused

antibiotics don’t help with viral infections

• ONLY take antibiotics for bacterial infections

prescription antibiotic misuse

• do not have a prescription

• not finishing the prescription

• using someone else’s leftover meds

antibiotic overuse with cattle

cattle were given antibiotics because they grew faster and had a higher weight gain

• lead to antibiotic-resistant bacteria

• found in meat, milk, etc

• EU and US banned this

Methicillin-Resistant Staphylococcus Aureus (MRSA)

• etiological agent

Staphylococcus aureus

• bacterial infection

• Gram + staphylococcus

MRSA

• resistance

resistant to beta-lactam drugs

• penicillin, amoxicillin, methicillin, cephalosporins

• very resistant to antibiotics

MRSA

• HA-MRSA

hospital associated

• occurs in healthcare settings

• higher risk of severe infections

• 85% of cases

MRSA

• CA-MRSA

community associated

• occurs outside healthcare settings

• can affect healthy individuals

• causes skin and soft tissue infections.

MRSA reservoir

25-30% → people colonized with S. aureus

• normal people who are infected by those with infection

1% → colonized with MRSA

MRSA transmission

• direct contact

• fomites

what increases the likelihood of getting MRSA

• 5 C’s

• crowding

• contact (skin to skin)

• compromised skin (cuts)

• contaminated items (fomites)

• cleanliness (lack of it)

MRSA symptoms

• red bumps

• quickly turn to deep abscesses

• gets worse rather than getting better

• deep infection

where in the body can MRSA spread to that is life-threatenin

MRSA

• virulence factors

has drug resistance genes

• resistant to antibiotics

• destroys tissues

• has leukocidin → associated with necrotizing pneumonia (flesh eating, holes)

MRSA treatment

• other antibiotics

• vancomycin (last resort)

• may try to drain abscess and take no drugs

HA-MRSA

• risk factors

• being in a hospitalization or care facility

• recently took antibiotics

HA-MRSA

• control

• handwashing

• use sterile IV’s and catheters

CA-MRSA

• risk factors

• younger, elderly, immunocompromised

• contact sports (wrestling)

• sharing towels, equipment

CA-MRSA

• control

• don’t share personal items

• keep wounds covered

• sanitize clothing & linens

• wash hands

• get tested if you have a skin infection that needs treatment

antimicrobial for viruses

antivirals

• doesn’t kill or destroy the virus

• inhibits replication

problems with treating viruses

• they are intracellular

• always mutating and causing variable strains

• viral resistance

• can be very expensive

antivirals

• HIV-HAART

recommended for ALL HIV patients

• highly active antiretroviral therapy

• decreases risk of disease progression and transmission

• NOT A CURE

antivirals

• HIV PrEP

• pre-exposure prophylactic

prevents contracting the virus

• if high risk individuals engage in unprotected sex

• reduces risk up to 99%

antimicrobials for eukaryotes

• antifungal

• antiprotozoan

• antihelminthic

why is treating eukaryotic microbes harmful

eukaryotic microbes and human cells share similar cellular structures

• both are eukaryotic

• need to have a magic bullet

what is phage therapy

using bacteriophages to treat bacterial infections

• viruses for bacteria

• specific to pathogens

• doesn’t harm the host and beneficial bacteria

• little resistance

history of phage therapy

• researched & used in former USSR countries

• clinical trials in Texas and London since 1917

how to you take phage therapy

either topically or oral administration

• injection of bacteriophage may trigger a host immune response to the phage

what is phage therapy used to treat

used for various wound and intestinal illnesses

• including MRSA (usually very resistant to antibiotics)

why is there no phage for C. difficile yet

due to its endospores

• virus can’t affect endospores

what are the safety concerns regarding phage therapy

• clinical trials not done yet

• phage might evolve

• don’t know how much to dose

• still experimental

what did the FDA approve regarding phage therapy

phage spray against Listeria

• kills bacteria

• makes food safer

• cold cuts, hot dogs

• virus dies off after Listeria is gone

other potential uses of phage therapy

• treating coral reefs

• honeybee diseases