Download In The Name of Allah Miscellaneous Antimicrobial Agents By

In The Name of Allah
Miscellaneous
Antimicrobial Agents
By:
Dr. M. Minaiyan
Isfahan University of Medical Science
Linezolid
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It is active against staphylococci, streptococci,
enterococci, and gram-positive rods such as
corynebacteria and Listeria monocytogenes
It is primarily a bacteriostatic agent (Protein
Synthesis Inhibitor) except for streptococci, for
which it is bactericidal
The recommended dosage for most indications
is 600 mg twice daily, either orally or
intravenously
Linezolid (ADR and Toxicity)
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Thrombocytopenia is the most common
manifestation (seen in approximately 3% of
treatment courses)
Anemia and neutropenia
Optic and peripheral neuropathy and lactic
acidosis have been reported with prolonged
courses of linezolid
Interactions with MAOI and SSRIs
Linezolid (Clinical Uses)
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Vancomycin-resistant enterococcal infections
Nosocomial pneumonia
Community-acquired pneumonia
Skin infections, complicated or uncomplicated.
It should be reserved for treatment of infections
caused by multidrug-resistant gram-positive
bacteria.
Teicoplanin
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A glycopeptide similar to vancomycin
Its mechanism of action is also similar to
vancomycin but it can be used in MRSA
strains
are
sometimes
resistant
to
vancomycin
It is used IV and IM with a long half life (4070 h)
Mupirocin
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It is isolated from P. fluoresence
(Psudomonic acid)
Topical use is only justified because of rapid
inactivation within the circulation
Inhibits Isoleucyl-tRNA synthase specially in
Staphylococcus aurous
Mupirocin
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It is effective to treat Staphyloccocal
infections both methicillin-susceptible and
methicillin-resistant species
More than 95% of S. aurous isolates are still
susceptible
Impetigo and minor skin lesions are main
clinical indications
It might be used for nasal staphylococcal
carriage eradication
Polymyxins
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They are basic peptides which act as cationic
detergents and damage cell membrane
Two common type are: polymyxin B and polymyxin
E (Colistin)
Gram negative aerobes are usually susceptible
Gram positive aerobes, Proteus and Neisseria
species are usually resistant.
Because of significant toxicity, their clinical uses are
limited to topical uses.
Nalidixic Acid
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It is a quinolone but not fluorinated congener
Gram negative bacteria is the main spectrum
of action
P. aeroginosae and Proteus strains are
resistant
Only in urinary tract, it reaches to bactericidal
levels
Nitrofurantoin
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A urinary antiseptic with specific action on E.coli
in lower urinary infections
Cross resistance and acquired resistance are
usually uncommon but P. aeroginosa and
Proteous sp are resisatnt
It is contraindicated in patients with renal
insufficiency
Undergone redox reactions to produce active
metabolite and exert toxic reactions with DNA
Nitrofurantoin
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The best antibacterial efficiency is attained in
urine pH of 5.5 and lower
It should not be used for upper UTIs
It is very suitable for prevention of recurrent
UTIs in women.
Nitrofurantoin antagonise the action of
Nalidixic acid and might causes neurophathy
and hemolytic anemia in patients with G6PD
deficiency.
Methenamine Mandelate
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Produces formaldehyde as well as mandelic
acid in acidic medium of urine (pH 5.5)
It should not be used concurrently with
Sulfonamides
because
of
insoluble
metabolite
production
and
resultant
antagonism
Proteus species are usually resistant
Patients taking this drug may have false
positive results for urine catecholamine tests.
Disinfectants and Antiseptics
Definition
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Disinfectants are strong chemical agents that
inhibit or kill micro-organisms
Antiseptics are disinfectants with sufficiently
lower toxicity that they can be used directly
on skin and mucus membranes.
Sterillants kill both the vegetative and spores
of microorganisms.
Products are devoid of any vital or vegetative
microorganism and their residues are named
sterile and pyrogen free.
Alcohols (60-90%)
(Ethanol-Isopropyl Alcohol)
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Advantages
Rapid action
Effective on vegetative
bacteria specially gram
+, Tuberclosis, Fungi,
Lipophylic viruses
Low cost
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Disadvantages
Inactive
on
spores,
hydrophilic viruses
Without residual effect
Skin drying properties
Flammable and must be
allowed
to
evaporate
before cautery, electrosurgery
and
laser
surgery.
Chlorhexidine gluconate (2-%)
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Advantages
Most activity against
gram+ bacteria
With residual effect
Moderate
activity
against
fungi
and
viruses
Spore generation might
be inhibited by the
presence of detergent
Safe as mouth wash
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Disadvantages
Intercats with non-ionic
and anionic detergents
e.g. soaps, surfactants
It should not be used
during the surgery of
middle
ear
and
neurosurgery
Slower action rather
than alcohols
Halogens
(Iodine, Iodophores, Chlorine)
Iodine
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Tincture of iodine contains 2% iodine & 2.4%
NaI dissolved in alcohol
The most rapid acting detergent on intact skin
(1min for bacteria and 15 min for spores)
It is effective on all forms of microorganisms
Hypersensitivity reactions and coloring
properties are most common limitations
Ionophores (Betadin, PVP)
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Complex of iodine and surface active agent
(Ionophore) with disinfectant and antiseptic
properties
It is used as antiseptic, disinfectant and scrub
solution
Better activity of iodine with less hypersensitivity
reactions
The amount of available free iodine depends on
degree of dilution
More concentrated solutions are suitable for
disinfection.
Chlorine
(Hypochlorite Na, 5.25%)
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House hold bleach and the most common
disinfectant and oxidizing agent
A 1/10 dilution produces 5000ppm chlorine
which is enough for killing spores
Dilution with tap water causes a pH of 7.5-8
which retains its activity for several months
Surface proteins, blood, serum and feces
interact with it and causes inactivation
Chlorine
(Hypochlorite Na, 5.25%)
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Chlorine interacts with formaldehyde and
produces bis-chloromethyl molecules which
are carcinogenic and must be avoided
Hypochlorite sodium is corrosive for metal
surfaces
Its mixing with acids and urine should be
avoided because of chlorine gas production
Benzalkanium Chloride
(Cetrimide, Savlon, Cetavlon, Detol,..
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Quaternary ammonium compound which acts as
cationic detergent
Precipitates proteins, inactivates enzymes and
disrupts cell membranes
They are bacteriostatic, fungistatic virustatic and
sporostatic agents.
Gram positives are more susceptible than gram
negatives (Tubercle and P. aeroginosa are
exceptions)
Inactivated in the presence of anionic detergents
and surfactants as well as Ca, Mg, Fe, & Al ions
Aldehydes
(Formaldehyde-Glutaraldehyde)
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Are suitable disinfectants and sterillants for
instruments (dialysis, spirometery, endoscopy,
dentistry apparatus, …)
They are not corrosive for metal, plastic and rubber
materials
They alkylate chemical groups in proteins and
nucleic acids
Formaldehyde 40%= Formalin 100%
Formaldehyde 4%= Formalin 10%
Formaldehyde 8%= Formalin 20%
Aldehydes
(Formaldehyde-Glutaraldehyde)
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Formalin 10% is quite suitable for tissue fixation
Formalin 20% is preferable as germicide &
sporocidal
Glutaraldehyde
Solutions of 2% W/V are most common.
It should be alkalinized to pH 7.7-8.5 for maximum
efficacy
Once activated, solutions are stable for 14 days
after which polymerization reduces its activity
Formaldehyde has pungent odor and is irritant.
They are allergic and carcinogenic so exposure
limitations should be critically considered
Hydrogen Peroxide
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Strong oxidizing agent with bactericidal,
fungicidal, virucidal and sporocial effects
The decomposed by-products are not toxic
and pollutant for environment
In concentrations of 10-25% are sporocial
In concentrations of 3-6% are disinfectants
for medical devices, soft lenses, prosthetic
devices and cartons containing milk or juices
Heavy Metals
(Mercury and Sliver)
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Disadvantages:
Biological
toxicity,
Environmental pollution, Acquired resistance,
Hypersensitivity reactions, Surface absorption
(rubber-plastic)
Thiomersal (0.001-0.004%) is used as
preservative in vaccines, antitoxins and immune
sera
Silver nitrate (0.1%) in ophthalmic drops for
preventing ophthalmic gonococcal infections.
Silver sulfadiazine slowly releases silver for
suppressing bacterial growth in burn wounds
Notes
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Hand washing with soap and warm water is
the most important means of preventing
infection transmission
Usage of skin disinfectants and detergents as
surgical scrabs are recommended only
before the surgical operations
Good luck