chemical control part2
DESCRIPTION
For BIO120lec1 2011-2012TRANSCRIPT
Chemical control
Microbial control part 2
Lani Manahan January 27,2012
Chemical Agents
1. PHENOLICS
2. ALCOHOLS
3. HALOGENS
4. HEAVY METALS
5. QUATERNARY
AMMONIUM
COMPOUNDS
6. ALDEHYDES
7. STERILIZING GASES
Chemical Agents
Chemical agent Effectiveness against
Endospores Mycobacteria
Phenolics Poor Good
Quats None None
Chlorines Fair Fair
Alcohols Poor Good
Glutaraldehyde Fair Good
PHENOLICS
• First widely used antiseptic and disinfectant
• Joseph Lister (1867): reduced the risk of infection during
operations
• Act by denaturing proteins and disrupting cell membranes
• Phenol / Phenolics: Lysol
• Bisphenols: Hexachlorophene, Triclosan
PHENOLICS
• ADVANTAGES: effective in the presence of organic material
and remain active on surfaces long after application
• DISADVANTAGE: disagreeable odor and can cause skin
irritation and in some instances brain damage
(hexachlorophene)
PHENOLICS
• Ethanol, Isopropanol (70-80% concentration)
• Act by denaturing
proteins and possibly by
dissolving membrane
lipids
• 10-15 soaking in alcohol
is sufficient to disinfect
thermometers and small
instruments
ALCOHOLS
• Iodine
– Kills by oxidizing cell constituents and iodinating cell
proteins
– Kill spores at high concentrations
– DISADVANTAGE: a stain may be left (answer = iodophor)
• Chlorine
– Usually for water supply
– Kills by oxidation of cellular materials and destruction of
vegetative bacteria, fungi
– Will not kill spores
– Death within 30 minutes
HALOGENS
• Mercury, Arsenic, Zinc, Copper
• Used as germicides
• How do they Kill:
– Heavy metals combine with proteins, often with their
sulfhydryl groups and inactivate them
– May also precipitate cell proteins
HEAVY METALS
• DETERGENTS
– Amphipathic (both polar and non-polar ends)
– Kill by disrupting microbial membranes and denature
proteins
– ADVANTAGE: stable, non-toxic
– DISADVANTAGE: inactivated by hard water
QUATERNARY AMMONIUM COMPOUNDS
Soap Degerming
Acid-anionic
detergents Sanitizing
Quaternary ammonium compounds Cationic detergents
Bactericidal, Denature proteins, disrupt plasma membrane
• FORMALDEHYDES
– Very reactive molecules that combine with proteins and
inactivate them
– Sporicidal and can be used as sterilants
ALDEHYDES
PHENOL COEFFICIENT TEST
– Best-known disinfectant screening test
– Potency of a disinfectant is compared with that of phenol
– The highest dilution that killed bacteria after a 10 minutes
exposure are used to calculate phenol coefficient
– The higher the phenol coefficient value, the more effective
the disinfectant under this conditions
• The reciprocal of the appropriate test disinfectant dilution is
divided by that for phenol to obtain the coefficient
• Example: phenol dilution = 1/90 and the maximum effective
dilution for disinfectant X = 1/450
• Phenol coefficient = 5
EVALUATION OF ANTIMICROBIAL AGENT EFFECTIVENESS
THE USE DILUTION TEST
– Metal rings dipped in test bacteria are dried
– Dried cultures placed in disinfectant for 10 min at 20°C
– Rings transferred to culture media to determine whether
bacteria survived treatment
EVALUATION OF ANTIMICROBIAL AGENT EFFECTIVENESS
EVALUATION OF ANTIMICROBIAL AGENT EFFECTIVENESS
• Disk diffusion
Chemotherapy
Chemotherapeutic agent:
Antibiotic
• An antibiotic is a product produced by a microorganism or a
similar substance produced wholly or partially by chemical
synthesis, which in low concentrations, inhibits the growth of
other microorganisms
– Antibiotics are medicines used to treat infections caused by
bacteria only
– Infections are usually caused by bacteria or viruses
– Antibiotics, therefore, do not cure all infections
– Many infections like the common cold, flu, mild sore throat
or diarrhea are caused by viruses
ANTIBIOTICS
Susceptibility Tests
1. Broth dilution - MIC test
2. Agar dilution - MIC test
ANTIBIOTICS
32 ug/ml 16 ug/ml 8 ug/ml 4 ug/ml 2 ug/ml 1 ug/ml
Sub-culture to agar medium
MIC = 16 ug/ml
Minimal Inhibitory Concentration (MIC)
ANTIBIOTICS
Susceptibility Tests
3. Agar diffusion
Kirby-Bauer Disk Diffusion Test
ANTIBIOTICS
Susceptibility Tests “Kirby-Bauer Disk-plate test” Diffusion depends upon:
1. Concentration
2. Molecular weight
3. Water solubility
4. pH and ionization
5. Binding to agar
(cont’d)
ANTIBIOTICS
Susceptibility Tests “Kirby-Bauer Disk-plate test”
Zones of Inhibition (~ antimicrobial activity) depend upon:
1. pH of environment
2. Media components
– Agar depth, nutrients
3. Stability of drug
4. Size of inoculum
5. Length of incubation
6. Metabolic activity of organisms
(cont’d)
ANTIBIOTICS
Antibiotic Mechanisms of Action
Transcription
Translation
Translation
Alteration of Cell
Membrane
Polymyxins
Bacitracin
Neomycin
• When bacteria are exposed to an antibiotic, they either
die or adapt
• Those that survive carry genes that protect them
against the antibiotic and pass those genes on to other
bacteria
• Since bacteria multiply very quickly and can be easily
spread among people, resistant bacteria can easily
occur in places like hospitals and nursing homes, where
a lot of people are gathered and antibiotic use is high
ANTIBIOTICS
New Resistant Bacteria
Emergence of Antimicrobial Resistance
Susceptible Bacteria
Resistant Bacteria
Resistance Gene Transfer
Resistant Strains
Rare
Resistant Strains
Dominant
Antimicrobial
Exposure
Selection for Antimicrobial-
Resistant Strains
Resistance
Physiological Mechanisms
1. Lack of entry – tet, fosfomycin
2. Greater exit
– efflux pumps
– tet (R factors)
3. Enzymatic inactivation
– bla (penase) – hydrolysis
– CAT – chloramphenicol acetyl transferase
– Aminogylcosides & transferases
4. Altered target
– RIF – altered RNA polymerase (mutants)
– NAL – altered DNA gyrase
– STR – altered ribosomal proteins
– ERY – methylation of 23S rRNA
5. Synthesis of resistant pathway
– TMPr plasmid has gene for DHF reductase; insensitive to TMP
Resistance to β-Lactams – Gram pos.
Mechanism of Action CELL WALL SYNTHESIS INHIBITORS
(cont’d)
Resistance to β-Lactams – Gram neg.
Mechanism of Action CELL WALL SYNTHESIS INHIBITORS
(cont’d)
Danger of spread of antibiotic resistant bacteria
Danger of spread of antibiotic resistant bacteria
• Antibiotics revolutionised medicine
• The first antibiotic, penicillin, was discovered by Alexander
Fleming in 1929
• It took less than 20 years for, bacteria to show signs of
resistance
• Staphylococcus aureus, which causes blood poisoning and
pneumonia, started to show resistance in the 1950s
• Today there are different strains of S. aureus resistant to
every form of antibiotic in use (MRSA)
Danger of spread of antibiotic resistant bacteria
Where do we get antibiotic resistant bacteria
• If a patient taking a course of antibiotic treatment does not
complete it
• Or forgets to take the doses regularly, then resistant strains
get a chance to build up
• When antibiotics are used on a person, the numbers of
antibiotic resistant bacteria increase in other members of the
family
• In places where antibiotics are used extensively
e.g. hospitals and farms
antibiotic resistant strains increase in numbers
0
10
20
30
40
50
60
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
Perc
en
t R
esis
tan
ce
Methicillin (oxacillin)-resistant
Staphylococcus aureus
0
5
10
15
20
25
30
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
Perc
en
t R
esis
tan
ce
Vancomycin-resistant
enterococci
Non-Intensive Care Unit Patients
Intensive Care Unit Patients
Antimicrobial Resistance Among Pathogens Causing
Hospital-Acquired Infections
Source: National Nosocomial Infections Surveillance (NNIS) System
0
2
4
6
8
10
12
14
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
Perc
en
t R
esis
tan
ce
3rd generation cephalosporin-
resistant Klebsiella pneumoniae
0
5
10
15
20
25
30
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
Perc
en
t R
esis
tan
ce
Fluoroquinolone-resistant
Pseudomonas aeruginosa
Non-Intensive Care Unit Patients
Intensive Care Unit Patients
Antimicrobial Resistance Among Pathogens Causing
Hospital-Acquired Infections
Source: National Nosocomial Infections Surveillance (NNIS) System
Link to: NNIS Online at CDC
Myths & Facts about Antibiotics and Respiratory Illness
Myths and Facts
• Myth: Taking antibiotics means I or my child
can return to work or childcare sooner
• Fact: Antibiotics do not shorten the duration
of viral illnesses
Everyone should stay home until they are
fever-free and well enough to participate in
activities whether they have a viral or
bacterial illness.
Myths and Facts
• Myth: Cold and flu symptoms will feel better
or get better faster on antibiotics
• Fact: Antibiotics cannot ease the symptoms
of viral illnesses; these infections resolve on
their own
Children and adults need extra rest and care,
extra fluids…not antibiotics, symptomatic
relief is helpful
Myths and Facts
• Myth: Illnesses with the same symptoms
require antibiotics
• Fact: Illnesses with similar symptoms can be
caused by different germs
Let a healthcare provider decide if the illness is
caused by a virus or bacteria - and if antibiotics
are needed
Myths and Facts
• Myth: If I take an antibiotic, I won’t spread my
illness to others
• Fact: Viral illnesses (colds, flu, etc.) usually
spread from person to person before the onset
of symptoms; before a person appears ill
Antibiotics cannot stop the spread of viral
illnesses
How do we Stop Antibiotic Misuse?
• Don’t ask for antibiotics – let your doctor
decide if you need them
• Always take antibiotics exactly as prescribed
• Finish the whole prescription - do not stop
when you feel better
• Never save antibiotics for a future illness –
or share with others
ANTIMICROBIAL RESISTANCE: KEY PREVENTION STRATEGIES
Optimize Use
Prevent
Transmission
Prevent
Infection
Effective
Diagnosis
and
Treatment
Pathogen Antimicrobial-Resistant Pathogen
Antimicrobial
Resistance
Antimicrobial Use
Infection
Susceptible Pathogen
12 Steps to Prevent Antimicrobial Resistance: Hospitalized Adults
1. Vaccinate
2. Get the catheters out
3. Target the pathogen
4. Access the experts
5. Practice antimicrobial control 6. Use local data 7. Treat infection, not
contamination 8. Treat infection, not colonization 9. Know when to say “no” to vanco 10. Stop treatment when infection
is cured or unlikely 11. Isolate the pathogen 12. Contain the contagion
Diagnose and Treat
Infection Effectively
Prevent Infection
Use Antimicrobials Wisely
Prevent Transmission