1 - TOPICAL ANTIBACTERIAL AGENTS Flashcards
Bacitracin is a topical antibacterial agent used for wound care and minor bacterial infections
True (can be combined with Polymyxin B and possibly also Neomycin to provide a wider spectrum of bacterial coverage)
Polymixin B is a topical antibacterial agent used for wound care and minor bacterial infections
True (not available as an individual product, usually in combination with Bacitracin as a ‘double antibiotic’/Bacitracin and Neomycin as a ‘triple antibiotic’ to broaden coverage against gram -Ve bacteria especially pseudomonas)
Mupirocin (Bactroban) is a topical antibacterial agent used for wound care and minor bacterial infections
True
Neomycin is a topical antibacterial agent used for wound care and minor bacterial infections
True (not available as an individual product, usually in combination with Bacitracin and Polymixin B as a ‘triple antibiotic’)
Retapamulin is a topical antibacterial agent used for wound care and minor bacterial infections
True
Gentamicin is a topical antibacterial agent used for wound care and minor bacterial infections
True
Silver sulfadiazine and iodoquinol are topical antibacterial agents used for wound care and minor bacterial infections
True
Iodoquinol is a topical antibacterial agent used for wound care and minor bacterial infections
True
Bacitracin is minimally effective for eliminating nasal carriage of S. Aureus
True (Mupirocin is superior)
A double-blind study comparing bacitracin with white petrolatum found no statistical difference in the postoperative infection rate in dermatologic surgery patients
True (90% of the wound infections in the petrolatum group were due to MSSA whereas the patients treated with bacitracin grew Ciprofloxacin-sensitive gram -Ve bacteria; given the higher cost of treating gram -Ve infections, the 0.9% risk of contact dermatitis and higher cost of bacitracin, It is less expensive to treat clean dermatologic surgical wounds with white petrolatum)
There is no systemic absorption of topical bacitracin
True
Common adverse effects with topical bacitracin include localised itching and burning
True
Bacitracin is a frequent allergen in patients with chronic stasis dermatitis or keratoconjunctivitis
True (barrier disruption in patients with stasis dermatitis and chronic leg ulcers may allow the development of contact dermatitis resulting in positive patch test results, thus long-term use on non-intact skin encountered in stasis ulcers or chronic inflammatory dermatoses may lead to an increased risk of contact allergy)
There have been a significant number of reported cases of anaphylactic shock due to topical bacitracin
True (most cases involved patients who had used bacitracin on non-intact skin such as ulcers)
Bacitracin often co-reacts (not a true cross-reaction as both are chemically unrelated) with Neomycin such that patch testing to both may uncover a Neomycin allergy which is the most common cause of postoperative allergic contact dermatitis
True (the co-reaction is believed to be due to coincidental sensitisation as Bacitracin is chemically unrelated to Neomycin but both antibacterial agents are commonly found in combination) - though Neomycin cross-reacts with other aminoglycosides such as streptomycin, kanamycin, gentamicin, tobramycin
Contact allergy to Polymyxin B in the absence of concomitant positive reactions to Neomycin and Bacitracin is very rare
True (usually combined with other antibacterial agents to broaden coverage against gram -Ve bacteria including pseudomonas)
Polymyxin B is not a significant allergen in postoperative wounds in dermatologic surgery patients
True
There is little systemic absorption and few systemic reactions even when Polymyxin B is applied to open wounds because Polymyxin B binds avidly to cell membranes
True
Because bacterial resistance to Neomycin has been reported in both gram +Ve and gram -Ve bacteria, Neomycin is virtually always used in combination with other topical antibacterial agents (Bacitracin and Polymyxin B to produce the ‘triple antibiotic’)
True
Bacitracin is typically added for its gram +Ve coverage
True (Polymyxin B is typically added to provide coverage for pseudomonas)
Polymyxin B is typically added to provide coverage for pseudomonas
True (whereas Bacitracin is typically added for its gram +Ve coverage)
Systemic toxicity to Neomycin (an aminoglycoside) includes ototoxicity and nephrotoxicity, although systemic absorption and toxicity do not occur when the antibacterial agent is used topically on minor skin lesions
True (Neomycin-related deafness has been reported but usually involving a Neomycin solution to irrigate a large wound, and rarely from ear drops containing Neomycin where this should not be used in patients with tympanic membrane perforation)
Bacitracin is bactericidal against gram +Ve and Neisseria species by interfering with bacterial cell wall synthesis
True (inhibition of phospholipid receptors involved in peptidoglycan synthesis)
Polymyxin B is bactericidal against gram -Ve bacteria and pseudomonas by increasing the permeability of bacterial cell membrane
True (occurs by interacting with phospholipid components of the cell membrane)
Neomycin (an aminoglycoside) is bactericidal against gram +Ve and gram -Ve bacteria by inhibiting protein synthesis, and is typically used for its gram +Ve coverage
True (occurs by binding to 30s subunit of ribosomal RNA)
Mupirocin (Bactroban) is bactericidal against MRSA and strep pyogenes by inhibiting bacterial RNA and protein synthesis
True (occurs by reversibly bonding to bacterial isoleucyl-tRNA synthetase) - Mupirocin is not active against anaerobic bacteria
Bacitracin is derived from Bacillus subtilis
True
Polymyxin B is derived from Bacillus polymyxa
True
Neomycin is derived from Streptomyces fradiae
True
Mupirocin is derived from P. fluorescens
True
Retapamulin is a semi-synthetic derivative of Clitopilus scyphoides
True
Gentamicin is derived from Micromonospora Purpurea
True
Silver sulfadiazine is synthesised from a reaction of silver nitrate and sodium sulfadiazine
True
Iodoquinol is a synthetic halogenated derivative of quinolone
True
Systemic absorption of Mupirocin is minimal and cutaneous metabolism is <3%, leaving most of the drug on the skin for antibacterial activity
True
95% of Mupirocin is protein bound, therefore it may be less effective on weeping wounds (drainage of serum/protein and clearance of the drug)
True
Mupirocin is used to treat skin infections frequently initiated by staph and strep, including impetigo, folliculitis, impetiginised eczema, burns, lacerations and leg ulcers
True
Mupirocin ointment is equivalent to PO erythromycin for the treatment of impetigo and is approved as a monotherapy
True (the higher cost of Mupirocin is offset by the increased incidence of adverse effects and lost production due to erythromycin)
Intranasal Mupirocin is effective for the elimination of staph, even MRSA from chronic carriers and most recent studies advocate BD application for 5 days, and prolonged suppression of nasal staph carriage is achieved by weekly dosing or monthly courses
True
Intranasal Mupirocin in combination with Chlorhexidine soap reduced nosocomial staph aureus surgical site infections in nasal carriers, whereas Intranasal Mupirocin alone is ineffective for this purpose
True
Among nasal MRSA carriers undergoing Mohs surgery, no postoperative MRSA infections occurred in patients who used Intranasal Mupirocin and PO Bactrim for 5-7 days
True
Most reactions associated with Mupirocin are localised pain, burning and itching which is attributed to the polyethylene glycol in the vehicle base because the incidence is no greater than with the vehicle alone
True (the nasal formulation is in WSP base and does not contain polyethylene glycol and so it is less irritating on mucosal surfaces)
Mupirocin does not cross-react with other topical antibacterials due to its unique structure
True
True allergic contact sensitivity to Mupirocin is extremely rare; and unlike Bacitracin and Neomycin, Mupirocin is an uncommon cause of postoperative allergic contact dermatitis following dermatologic surgery
True (Mupirocin is an uncommon sensitiser)
Retapamulin is bacteriostatic against strep pyogenes, Mupirocin-resistant staph aureus, MRSA and anaerobes by inhibiting bacterial protein synthesis
True (occurs by binding to protein L3 on the 50s ribosomal subunit)
Retapamulin has no clinically relevant cross-resistance with other antibacterials due to its unique structure
True
Retapamulin is FDA-approved for the treatment of primary impetigo due to methicillin susceptible staph aureus or strep pyogenes in adults and children 9 months of age and older
True (recommended BD for 5 days for the treatment of impetigo)
The most frequent adverse effects of Retapamulin are localised pruritus, paraesthesia, irritation or pain at the application site
True
Retapamulin may cause an allergic contact dermatitis with positive patch testing
True
Gentamicin is bactericidal against gram +Ve (excluding strep) and notably gram -Ve organisms including pseudomonas, by inhibiting bacterial protein synthesis
True (occurs by irreversibly binding to 30s ribosomal subunits)
Gentamicin is an uncommon sensitiser although rarely allergic contact dermatitis is found in patients with Rosacea thought to be secondary to prior antibiotic treatment of ocular disease
True
Neonatal patients who used gentamicin ointment for ocular infection prophylaxis developed periocular ulcerative dermatitis
True
Silver sulfadiazine is bactericidal against gram +Ve (including MRSA) and gram -Ve organisms (especially pseudomonas in burn wounds) by inhibiting bacterial replication
True
Silver sulfadiazine has a low toxicity profile although caution should be exercised with application to large burn sites and with prolonged use in bullous disorders as renal insufficiency has been reported with significant absorption
True
Silver sulfadiazine may cross-react with patients who have a sulfonamide allergy
True (due to the shared sulfa moiety)
Silver sulfadiazine may cause haemolytic anaemia in patients with G6PD deficiency due to the cross-reaction with sulfonamide
True
Iodoquinol is active against gram +Ve (including MRSA) and gram -Ve organisms (including pseudomonas) as well as being a broad spectrum agent against dermatophytes and may be useful in the treatment of fungal infections complicated by secondary bacterial involvement
True
Benzoyl peroxide is used as a topical antibacterial agent for acne and rosacea
True
Clindamycin is used as a topical antibacterial agent for acne and rosacea
True
Erythromycin is used as a topical antibacterial agent for acne and rosacea
True