Discussion re theory behind, and appropriateness of, antibiotic surgical prophylaxis

1. Antibioticsrevolutionisedmedicine.Infectionsthatroutinelykilledpatientscouldbe cured by Penicillin.
Overtime andwidespread, sometimesindiscriminate,use bacteriaevolvedandbecame resistanttothese
drugs.Thisnecessitatedthe developmentof new agentsbutthesetoolosttheirbacterialkillingpoweras
bacterial populations developed defences against them.
When I started in dermatology it was very common to see antibiotics to be prescribed ‘just in case’ or
used if the patient had a heart valve defect or artificial joint etc. This was often done regardless of the
surgery being performed. The intervention was premised on little data.
A recentreviewinthe AustralasianJournal of Dermatopathology(Volume 57,Issue 2May 2016 Pages83–
91) reviews prophylactic antibiotics in dermatological surgery.
A surgical site infectionisdefinedas“aninfectionthatoccursaftersurgeryinthe part of the body where
the surgerytookplace.Surgical site infectionscanbe superficial infectionsinvolvingthe skinonlyormore
serious infections, which can involve tissues under the skin, other organs, or implanted material.
Symptoms include erythema, tenderness and purulent exudate around the surgical site.”
This is a large and very important topic. Wound infections after surgery and systemic infections lead to
associated morbidity and may lead to worse cosmetic results. Prescription of preoperative and
postoperative antibioticsinan attemptto preventsurgical site infections canleadto increasedbacterial
resistance, increased morbidity and costs.
Wound infections after skin surgery are uncommon and the incidence varies depending on the surgical
site, the type and length of the procedure, the type of surgical repair,the definitionused for a surgical
site infection,the patient'smedical history,andwhetherprophylacticantibioticswere used. The authors
quote a numberof studieswithinfection rates ranging from 0.5% to 11% after simple or Mohs surgery.
The big fearis not of woundinfectionperse but causinginfective endocarditisorjointinfections.These
occur through bacteraemia.
Happily, bacteraemia is not a usual accompaniment of skin surgery of course. In a study of 149
immunocompetent patients with non-infected cutaneous lesions, the incidence of postoperative
(biopsies, flaps, grafts and micrographically controlled surgery) bacteraemia was reported to be 0.7%.

2. Everytime we prescribeantibioticsweputthe patientatriskof anadverseevent. A studyof 142 000 visits
to the emergency department for drug-related adverse events demonstrated that 19% were due to
antibiotics.One-half of these visitswere attributabletoPenicillinsandCephalosporins.Thiswasnot just
drug side effects and allergic reactions but also Clostridium difficile infections.
The prevalence of Clostridium difficile infection is related to total antibiotic usage and, in particular,
extendedspectrum generation cephalosporins. An orthopaedic study demonstratedthat three doses of
cefuroxime increased the risk of C. difficile diarrhoea (4%) compared with one dose of Cefuroxime and
Gentamicin (2%). Patients with C. difficile infection had a statistically significant increase in antibiotic
exposure,inpatientstay,morbidityandmortality. Anotherstudydemonstratedasignificantreductionin
C. difficile-associated diarrhoea when the amount of Cephalosporins administered was reduced.
We wantto avoidthe developmentof antibioticresistantbacteria.The prevalence of antibioticresistance
isrelatedtothe proportionof the populationthatreceivesantibioticsandthe total antibiotic exposure.
A studyof patientswhohadfree flapreconstructionsof headandneckdefectscomparedthe acquisition
of Methicillin-resistantStaphylococcusaureus(MRSA)inthosewhoreceived24 hof antibioticswiththose
whowere administereda5-daycourse of antibiotics.There were significantlyfewerpatientswithwounds
infected with MRSA in the 24-h course group (4/33 compared to 13/31).
The evidence suggests that inappropriate prolonged postoperative antibiotic exposure contributes to
growing antibiotic resistance.
What are the principles of antibiotic prophylaxis for skin surgery?
1. Antibioticprophylaxisshouldbe consideredonlywhenthere isasignificantriskof postoperative
infection with significant morbidity.
2. Prophylacticantibioticsshouldbe directedagainstthe bacteriamostlikelytocause infectionand
it is not necessary to target all potential pathogens.
3. In choosing prophylactic antibiotic(s) the clinician should consider patient's factors, such as
colonisation with a multi-drug resistant organism or whether the patient has had a similar pre-
existing infection.
4. The narrowest spectrum antimicrobial should be used to treat the likely pathogen.
5. Surgical antibiotic prophylaxis is not the only strategy to minimise surgical site infections. A
holistic approach to the patient, such as maximising the patient's medical management
perioperatively and ensuring that operating staff adhere to strict theatre protocols to minimise
cross-infection between staff and patient as well as instrument and operating room
contaminants, is required.

3. What are the principles guiding management of a skin surgery wound infection?
1. If a diagnosisof asurgical site infectionismade,aswabof the woundformicroscopy,culture and
sensitivitiesshouldbe performed.Empiricantibiotictherapyshouldbeinitiatedandshouldreflect
the predominantpathogenatthat particularanatomical site andthen be modifiedbasedonthe
culture results once they are available.
Normal and transient bacteria vary among the different anatomical sites; thus the selection of an
antibiotic, if required, for a surgical site infection should reflect the predominant pathogen at that
particular anatomical site.
Skin
The primarypathogensonglabrousskin are S. aureusand beta-haemolyticstreptococci andpenicillinase
resistantantibioticssuchasDi-flucloxacillinorCephalexinare effectiveagainstboth.If allergictoPenicillin
and cephalosporins,clindamycin or vancomycin may be administered.If the patient is known to have
MRSA then Clindamycin, Trimethoprim-sulfamethoxazole or Doxycycline may be administered. S.
epidermidisis part of the normal skin flora; however, it is a low-virulence organism that causes disease
primarily in immunocompromised patients and in those with implants.
Oropharynx
The primarypathogensarisingfromthe oropharynx are Viridansgroupstreptococci andbacteriathatare
known to cause infective endocarditis.Antibiotics are generallyrecommended only for oropharyngeal
procedures inpatientswhohave anincreasedriskof infectiveendocarditis,suchasthose withprosthetic
valves, complicated congenital cardiac abnormalities and high-risk rheumatic heart disease. Where
antibiotics are indicated, Amoxicillin is the treatment of choice, with Clindamycin being a suitable
alternative for patients with Penicillin allergy.
Intertriginous sites
In addition to S. aureus and beta-haemolytic streptococci, the axillary, groin and perineal areas are also
colonised withgram negative bacilli such as Escherichia coli,which may cause surgical site infections. E.
coli are usually sensitive to Cephalosporins but this is variable.
Ear
S. aureus and beta-haemolytic streptococci are found in the ear and the antibiotic of choice for an
infectionis the same as forother skininfections.Pseudomonasisagram negative rodthatreadilygrows
in moist areas of the skin and thus is a potential pathogen in the ear and digital spaces. Acute localised
otitisexternaisusuallycausedbyS.aureusorS.pyogenesandisusuallyacomplicationof aninfectedhair

4. follicle. Acute diffuse otitis externa follows the maceration of the ear canal after water exposure. P.
aeruginosa and S. aureus may be implicated in this condition, which is usually treated with a topical
combination corticosteroidandantibiotic(FramycetinandGramicidin)eardrops.Malignantornecrotising
otitisexternaisaseverecomplicationof acute otitisexternausuallycausedbyP.aeruginosaandrequires
the involvement of an infectious disease specialist and aggressive therapy with i.v. antipseudomonal
antibiotics such as Piperacillin and Tazobactam.
Obviously,identifyingthe patientorwoundmore likelytobecomeinfectedisvitalindecidingwhetherto
give or withhold prophylactic antibiotics.
The authors explore the factors that make wound infection more likely. These include:
1. Diabetes is everyone’s first pick and a Queensland study showed that diabetes was significantly
correlatedwithahigherincidence of infection;withan incidenceof 18versus8% innon-diabetics.
2. Tobacco smokingis associatedwitha higherincidence of postoperative complications,including
wound dehiscence, flap or graft necrosis, prolonged healing time and infections.
3. Immunosuppression is a risk factor for surgical site infection following excisions with
reconstruction (full thickness skin grafts and flaps) rather than excisions alone.
4. The state of the skin where you are operating is important. A prospective study demonstrated
the risk of surgical site infection was significantly increased for scaly (12%), crusted (18%) and
ulcerated (33%) skin surfaces than with intact surfaces (4%).
5. Older patients were also more likely to have lesions with a broken skin surface.
6. Atopic dermatitis predisposes patients to wound infection.
7. Where youperformthe procedure isimportant,asshownin aprospectivestudyof patientswho
underwent a dermatological procedures (such as elliptical incisions, punch incisions, shave
biopsiesorcurettageandcautery) inthe warddemonstratedahighercomplicationrate (infection
and wound dehiscence) than those who had the procedures performed in an outpatient setting
(53 vs 17%). It is postulated that the dermatology ward inpatients were more likely than their
outpatientcounterpartstohave more widespreadskindisease,possiblycolonisedwithS.aureus,
tobe systemicallyunwellandtorequireintensive topical therapyfortheirunderlyingdermatoses.
8. Nasal carriage of S. aureus (30% of the population is colonised) is a risk factor for surgical site
infections, with carriers having three to sixfold the risk of surgical site infection of non-carriers
and low-level carriers. A study demonstrated that S. aureus strain isolated from the nares was
identical to the infected site in 85%.
9. The anatomical site isimportantwith the lowerextremities,groin,awedge excisionof the earor
lip, repair with skinflaps of the nose, skin grafts and those with extensive inflammatory disease
beingmore prone to woundinfection. Infectionratesof earsurgeryhave beenreportedtobe as
high as 13%, much greater than non-auricular sites. The infection rate of excision at the level of
cartilage is much greater (29%) than the infection rate of procedures without cartilage
involvement (6%).
10. The procedure performedisimportantwith skinflapshavingratesof infectionrangingfrom2 to
3% in the absence of antibiotic prophylaxis.

5. 11. Getting operators to remove hand jewellery, artificial nails and nail polish is recommended to
reduce infection.
12. Routine hairremoval shouldbe avoided.If the hairhastobe removedthenusingelectricclippers
with a single-use head on the day of surgery rather than a razor is recommended,as the latter
increases the risk of surgical site infection.
13. The operating team should wash their hands prior to the first operation using an antiseptic
surgical hand-wash and ensure that their hands and nails are visibly clean. Before subsequent
operations, the hands can be washedwith either an alcoholic hand rub or an antiseptic surgical
hand-wash.The skinatthe surgical site shouldbe preparedimmediatelybefore incisionusingan
antiseptic such as povidone-iodine or chlorhexidine.
14. Meticulous haemostasis, surgical technique, and the level of training of the dermatological
surgeon are important factors in minimising surgical site infections.
To give some order to this information Dermatological wounds can be classified into four categories.
 Class I: Wounds are clean, non-contaminated, closed by suturing and there are no breaks in
aseptic technique. The risk of infection in this class has been reported to be less than 5%.
 Class II: Wounds are clean-contaminated wounds, such as those in the oral cavity, axillary or
inguinal areas and wounds left to heal by secondary intention. In these wounds, the risk of
infection has been reported to be less than 10%.
 Class III: Wounds are contaminated and are acute, traumatic wounds that are non-purulent or
where there are major breaksinthe aseptictechnique.The riskof infectionin these woundshas
been reported to be 20–30%.
 Class IV: Wounds are infected wounds characterised by purulent inflammation, foreign body
contaminationordevitalisedtissue.In these the risk of infection has been reported to be 40%.
Both class III and IV wounds warrant antibiotic treatment.
So how can we use prophylactic antibiotics?
As we know that nasal staph carriage is common and can result in increased risk of wound
infection, an option is to swab patients noses and treat those with staph to try and rid them of
carriage prior to surgery. This has been done in studies with intranasal Mupirocin ointment and
chlorhexidine washes.
The data are most compelling in cardiac and orthopaedic surgery patients who, being nasal
carriers of S. aureus, were decolonised with prophylactic intranasal Mupirocin and had lower
rates of surgical site infections. In a randomised, double-blind, placebo-controlled trial of general
surgical, gynaecological, neurological and cardiothoracic patients there was no significant
difference in the rate of surgical site infections between the intranasal Mupirocin and placebo
groups (2.3 vs 2.4%). However, of the patients who had S. aureus in their anterior nares, 4% of
those who received intranasal Mupirocin had nosocomial S. aureus infections versus 8% in those

6. who received placebo. This study suggests that topical intranasal Mupirocin should be used only
in S. aureus carriers and not as a generalised prophylactic measure.
In a study of Mohs surgical cases, 738 cases underwent a nasal swab to determine their S. aureus
carriage; 203 tested positive for S. aureus. Of the 102 cases that received decolonisation with
Mupirocin and topical chlorhexidine gluconate wash for 5 days preoperatively, 4% developed a
surgical site infection versus 11% of the 101 patients who did not receive decolonisation. In this
study, 96% of all cases involved the head and neck, of which 39% involved the nose. Skin flaps
and grafts were utilised in 94% of the cases. The authors advocated that an alternative approach
would be to screen all patients for nasal carriage of S. aureus in patients undergoing
dermatological surgery and to subject them to decolonisation rather than place them on oral
systemic prophylactic antibiotics, if indicated.
A study of Mohs surgical patients who were stratified into nasal carriers or non-carriers of S.
aureus, based on a preoperative swab. Nasal carriers were randomised to receive either topical
decolonisation with intranasal Mupirocin twice daily plus chlorhexidine gluconate body wash for
5 consecutive days before surgery or to oral cephalexin 2g preoperatively and 1g postoperatively.
The infection rate for the group that had received oral antibiotic prophylaxis was 9% in contrast
to 0% in the group who received topical decolonisation. The infection rate was 6% in the non-
carrier group.
These studies suggest that screening and decolonising S. aureus nasal carriers with topical
Mupirocin and chlorhexidine washes may reduce the risk of surgical site infections. This raises
the question whether all preoperative patients should undergo topical decolonisation, given that
S. aureus also resides in areas such as the axillae and groin. At this stage the studies do not exist.
A concern in the use of Mupirocin is the development of resistance.This has been observed when
Mupirocin has been used for a prolonged period of time as a skin ointment. However, resistance
rarely develops when it is used for short periods in the preoperative setting, suggesting
appropriateness of use in a prophylactic setting.
The Australian therapeutic guidelines do not recommend antibiotic prophylaxis for routine sterile
dermatological surgery.

7. Prophylactic topical antibiotics in the postoperative phase
You will often see the use of topical antibiotics to the wound post operatively as a means of
reducing wound infection. Topical antibiotics can cause allergic contact dermatitis, cost to the
patient and the health-care systemin addition to emerging antibiotic resistance. Those problems
would be acceptable if topical antibiotics added anything to patient care.
A prospective randomised controlled study showed that the application of paraffin or Mupirocin
ointment under a moist occlusive dressing made no difference to infection rates, the pain
experienced, wound discomfort or long-term wound aesthetic outcomes compared with no
application of the ointment. There was no significantdifference in the infection rate between the
three comparator groups: 1.4% with no ointment, 1.6% for paraffin and 2.3% for Mupirocin
(P = 0.49). There were fewer scar complications in the no ointment group (0% versus 0.7% in the
paraffin group versus 1.2% in the Mupirocin group) largely due to skin necrosis.
A study of patients undergoing Mohs micrographic auricular surgery showed no statistically
significant difference between the use of Gentamicin ointment and petrolatum in the prevention
of postoperative auricular suppurative chondritis. Eight of the 144 wounds developed
suppurative chondritis; four received Gentamicin (5%) and four received petrolatum (7%). Twelve
of the 144 wounds developed inflammatory chondritis, 10 of which wounds received Gentamicin
(12%) and two received petrolatum (4%). This may represent allergiccontact dermatitis to topical
Gentamicin.
The Australian therapeutic guidelines specifically recommend against the application of topical
antibiotics to surgical incisions for the prevention of surgical site infection. primary intention to
reduce the risk of surgical site infection.
Then we come to the vexed question of when to prescribe antibiotics to prevent endocarditis or
joint infection by haematogenous spread.
The Australian antibiotic therapeutic guidelines recommend antibiotic prophylaxis for patients
with cardiac conditions associated with the highest risk of adverse outcomes from endocarditis
if they are undergoing a specified dental or other procedure. The high-risk group encompasses
those with a prosthetic cardiac valve or prosthetic material used for cardiac valverepair; previous
infective endocarditis; rheumatic heart diseases in high-risk patients and congenital heart
disease, but only if it involves: (i) unrepaired cyanotic defects including palliative shunts and
conduits, (ii) completely repaired defects with prosthetic material or devices, whether placed by
surgery or catheter intervention, during the first 6 months after the procedure (after which the
prosthetic material is likely to have been endothelialised), (iii) repaired defects with residual
defects at or adjacent to the site of a prosthetic patch or device (which inhibits

8. endothelialisation). The American Heart Associationdoes not recommend prophylaxis for cardiac
pacemakers and internal defibrillators.
The Australian antibiotic therapeutic guidelines recommend amoxicillin 2 g 1 hour prior to
undergoing a specified dental procedure that targets viridans streptococci, the primary oral
pathogen responsible for infective endocarditis. Patients allergic to penicillin may be prescribed
cephalexin 2 g or clindamycin 600 mg The Mayo Clinic advisory statement extends this area to
oral mucosa (defined as the non-glabrous oral tissue posterior to the junction where closed lips
meet).
No prospective randomised controlled studies exist on the use of
prophylactic antibiotics to prevent haematogenous joint infection in
patients who have undergone a dermatological procedure.
The Australian antibiotic therapeutic guidelines state that:
For patients with a pre-existing joint prosthesis in situ, there is a risk, though low, that seeding of
the prosthetic site, with subsequent infection, can follow an incidental bacteraemia during the
surgicalprocedure. Despitethis, neither the indication for prophylaxis nor the choice of antibiotic
regimen is altered by the presence of a joint prosthesis for dermatological procedures.
The American Dental Association, however, in conjunction with the American Academy of
Orthopaedic Surgeons, identifies a group of patients who are potentially at high risk of
haematogenous joint infection secondary to bacteraemia. These include patients who have
received a joint replacement in the preceding 2 years, those with a prior history of prosthetic
joint infection; immunocompromised or immunosuppressed patients, including those with
rheumatoid arthritis, systemic lupus erythematosus, drug-induced or radiation-induced
immunosuppression, HIV infection, malignancy, malnourishment, and haemophilia.
In contrast to the Australian therapeutic guidelines, the Mayo Clinic advisory statement advises
that if a high-risk patient is undergoing a dermatological procedure that involves or breaches the
oral mucosa, a non-infected site that is at high risk for a surgical site infection, then antibiotics
are recommended. The choices of antibiotics are the same as that for infective endocarditis.

9. So, if we are going to give antibiotic prophylaxis when should it be administered? Obviously, the
antibiotic has to be present at the surgical site prior to the infective organism establishing itself.
Thus, prophylactic antibiotics should be administered at a time that will produce serum and
tissue concentrations exceeding the minimum inhibitory concentration of likely pathogens for
the duration of the operation.
A prospective study of patients undergoing clean or clean-contaminated surgery (gynaecological,
gastrointestinal and orthopaedic) demonstrated that the preoperative administration of
antibiotics within two hours before surgical incision decreased the risk of surgical site infection
to 1%, compared with 4% for those administered antibiotics two to twenty-four hours prior to
surgicalincisionand 3% for any postoperative administration. A case-controlled study of patients
undergoing orthopaedic surgery showed that the timing of preoperative antibiotic prophylaxis
was an independent risk factor for surgical site infection. The rate of surgical site infection was
higher in those receiving antibiotic prophylaxis more than sixty minutes before incision (OR 2.2)
or after incision (OR 4.4) than in those who received antibiotic prophylaxis within sixty minutes
before the incision. Other large-scale studies of general surgical, cardiac, orthopaedic and
gynaecologicalpatients showed there was alower risk of surgicalsiteinfection with shorter times
between the administration of the antibiotic prophylactic and the skin incision.
Intraoperative redosing is required to ensure adequate serum and tissue concentrations of the
antibiotic if the duration of surgery exceeds two half-lives of the antibiotic. This may be
important in complex Mohs micrographic surgery where wounds may be open for an extended
period of time. For most dermatological procedures performed in the office,this is not a concern.
A single preoperativedose of antibiotic is a sufficient prophylaxisand evidence
suggests there is no additional benefit froma prolonged postoperativeantibiotic
administration greater than twenty-four hours.
The prevalence of antibiotic resistanceis relatedto the proportion of the population that receives
antibiotics and the total antibiotic exposure. In a study of coronary artery bypass graft surgery,
prolonged antibiotic prophylaxis (greater than forty-eight hours) instead of a shorter duration of
prophylaxis (less than forty-eight hours) failed to reduce the risk of surgical site infection.
Prolonged prophylaxis was also associated with an increased risk of acquired antimicrobial
resistance (OR 1.6). A study of cardiac patients receiving perioperative Vancomycin (one dose
preoperatively and two doses postoperatively) were screened for the emergence of VRE
colonisation. No patient was VRE-positive at baseline and 4% were positive at day seven. A study

10. of patients who had free flap reconstructions of head and neck defects compared the acquisition
of MRSA in those who received twenty-four hours of antibiotics with those who were
administered a five-day course of antibiotics. There were significantly fewer patients with
wounds infected with MRSA in the twenty-four hour course group (4/33 compared to 13/31).
The evidence suggests that inappropriate, prolonged postoperative antibiotic
exposure increases the risk of postoperative infection caused by multi-resistant
microorganisms and other complications such as Clostridium difficile infection.
The Australian therapeutic guidelines recommend that preoperative antibiotics should be
administered within the sixty minutes before surgical incision with the exception of i.v.
Vancomycin, where administration fifteen to thirty minutes before surgical incision is optimal.
Where an infusion is required, administration should ideally be finished before surgical incision.
Intraoperative redosing is required only if the duration of surgery exceeds two half-lives of the
antibiotic. Postoperative prophylactic antibiotics are not recommended. The continuation of
antibiotics while waiting for noninfected skin grafts or flaps to epithelialise is not recommended.

11. The authors conclude:
“One mustconsider the benefits and risks of prescribing antibiotics, which include
adverse events, allergies, costs to the health-care system and antimicrobial
resistance. Recent evidence-based guidelines on surgical prophylaxis recommend
no antibiotic prophylaxis for clean, uncomplicated dermatological surgery. When
risk factors for a surgical site are present a single preoperative dose is
recommended. There is no evidence for using topical antibiotics postoperatively,
with the risk of allergic contact dermatitis. The evidence-based guidelines
recommend more restricted indications for and a shorter duration of antibiotic
prophylaxis in situations where no clinical benefit of prolonged therapy has been
proven. This will help minimise the adverse clinical effects and the rise in
antimicrobial resistance that compromises the effectiveness of our current
armamentarium of antibiotics.
This review recommends the cautious use of prophylactic antibiotics in
dermatologicalsurgeryto help preventthe growingproblemof bacterialresistance
as well as other morbidity and health-care costs.”

12. Prophylactic antibiotics for dermatologic surgical procedures
Location or type of surgery
Antibiotic
restriction
Antibiotic
Adult dosage
One hour
preoperatively
1. IM = Intramuscular.
2. IV = Intravenous.
High risk for surgical site infection
No
penicillin
allergy
Di/Flucloxacillin (oral) 2 g
Cephazolin (IV) 2 g
Penicillin
allergy
Cephalexin (oral) or
Cephazolin (IV)
excluding immediate
hypersensitivity
2 g
Clindamycin (oral) or
vancomycin (IV) for
immediate
hypersensitivity
600 mg
15 mg/kg for
vancomycin
infusion
Oral (Mayo clinic advisory statement
extends this area to the non glabrous
oral tissue posterior to the junction
where closed lips meet) in patients at
high risk for infective endocarditis*
and haematogenous joint infection**
* Australian therapeutic and Mayo
clinic guidelines
** Mayo clinic guidelines
No
penicillin
allergy
Amoxycillin (oral) 2 g
Ampi/Amoxycillin (IM
or IV)
2 g
Penicillin
allergy
Cephalexin (oral) or
cephazolin (IM, IV)
excluding immediate
hypersensitivity
2 g
Clindamycin (oral or IV)
for immediate
hypersensitivity
600 mg