Diabetic Foot
Antibiotic Choice
Dr. Noura Al-Sweih
Antibiotic Choice
• Site of infection (SSTI) • Host factors • Type of causative organisms (NOT Isolated one) • Type of antibiotics
• Clinician Decision
To select the most appropriate antibiotic regimen, usually in the face of inadequate microbiological information
Diabetic Foot
• Site of Infection (skin & soft tissue infection)
• Skin and Underlying tissue form usually a defensive barrier against infection (physical defense) – Neuropathy Skin Breaks – Poor arterial perfusion affect infection outcome
Diabetic Foot
• Host factors
• Vascular supply may be so poor or infection so extensive antimicrobial administration is insufficient to ensure eradication of infection and ultimate healing
Diabetic Foot
• Wound healing is impaired when hypoxia is present. The presence of bacteria is a factor in poor healing because bacteria compete with normal cells for O2 and nutrients
Host Factor
Diabetic Foot Infection
Superficial
Deep, Limb threatening Infections
Diabetic Foot
Deep, Limb threatening Infections
Cellulitis
Septicemia Osteomyelitis +/- drainage sinuses
Diabetic Foot
Type of organism
Infections are frequently polymicrobial with both aerobic and anaerobic bacteria
Diabetic Foot
• Common causative organisms are • S. aureus & Streptococci • Less common are Proteus, E coli and Pseudomonas • Deep infections, Bacteriods
Diabetic Foot
• Bacteriologic cultures should be obtained from biopsy specimens to identify bacterial pathogens (not superficial swabs) • The choice of antibiotics should take into account
– Severity of infection – Types of organisms – Culture specific antibiotic sensitivity
• Topical antimicrobial therapy
– Result in the development of resistance – Fail to adequately penetrate the skin and underlying tissue – Development of hypersensitivity reactions
• Topical antiseptics e.g. povidone iodine or hydrogen peroxide have shown to have a cytotoxic effect on fibroblast and granulation tissue They impair wound-healing process and may be advised only if wound is heavily colonized
Guidelines
• Broad-spectrum antibiotics for patients with sever infections • Narrow- spectrum antibiotics for superficial infections • Therapy should always include coverage for aerobic-gram-positive cocci (S.aureus &β-haemolytic streptococci) not enterococci
Guidelines
• The time to target aerobic Gramnegative bacilli must be considered in patients with chronic infection and the predominant organism isolated from deep tissue specimen (60% of swabs will be + for Gram-negative bacilli especially in patients receiving antibiotics and these are not causing infection but colonizers)
Guidelines
• The role of obligate anaerobic bacteria should be considered if patient had necrosis or gangrenous ischemic limb. • After considering the likely pathogen and appropriate antibiotic choices, the route of therapy must be decided. Sever infections require parental therapy to achieve reliable blood levels quickly.
Guidelines
• Debridment
• Reduce bacterial load • Allow through examination of wound • Important for wound healing
Guide to select an empirical antibiotic regimen for a diabetic foor infection
Type of Infection Acute &low risk of MRSA High local rate of MRSA Chronic & previous antibiotic Likely pathogen (s) Class of Antibiotic GPC (staph & strep) MRSA GPC+GNB =/anerobes Cloxacillin, cephalothin Doxycycline, clindamycin, vancomycin, Linezolid Tazocin, ciprofloxacin, imipenem
Necrotic / gangrenous GPC+GNB +Anaerobe
Clindamycin+ ciprofloxacin Metronodazole + ciprofloxacin Tazocin, imipenem Tazocin, ceftazidime, ciprofloxacin
Green-blue pus
Pseudomonas aeruginosa
Diabetic Foot
• Conclusion
– Appropriate antibiotic therapy is a cornerstone of managing the infected foot which is a difficult task – Peripheral vascular insufficiency and increasing antibiotic resistance are primary barriers to successfully managing these infections