Surgical Infections and Antibiotic Selection
By: Masoud Salaran DVM, Resident in Veterinary Surgery
Introduction
golden age 1941
Antib
iotic
Prophylactic
therapeutic
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Bacterial survival in a host depends on:
bacterial virulence and numbershost immunocompetencewound factors that deactivate host defenses
presence of blood clots foreign material ischemic tissue pockets of fluid
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Destruction of Bacterial Cell Walls
Inhibition of Protein Synthesis
Inhibition of DNA Synthesis
MECHANISMS OF ANTIBIOTIC ACTION
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β-lactam ring antibiotics Penicillins
Vancomycin Cephalosporins
Bacitracin Carbapenems
Polymyxin Monobactams
Nystatin
Amphotericin B
Imidazoles
Destruction of Bacterial Cell Walls
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Aminopenicillins amoxicillin, ampicillinGram aerobes and some Gram and Gram anaerobes
Carboxypenicillins ticarcillinbetter Gram and anaerobe spectrums than the aminopenicillins
Ureidopenicillins piperacillin, mezlocillinbest Gram spectrums of all the penicillins
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Cephalosporins 7
Bind to bacterial ribosomes, causing reversible inhibition of protein synthesis
Chloramphenicol
Tetracycline
Erythromycin
Clindamycin
Inhibition of Protein Synthesis
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Chloramphenicol:
Broad-spectrum activity against streptococci, staphylococci, Salmonella spp., Brucella spp., Pasteurella spp., Ehrlichia spp., Rickettsia spp., and anaerobes, but it has poor activity against Pseudomonas spp.
Highly lipophilic
Inhibition of Protein Synthesis
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Tetracycline, Oxytetracycline, Doxycycline, Minocycline
Many Gram and Gram bacteria, including Chlamydia spp., Rickettsiae, Spirochetes, Mycoplasma spp., Bacterial L-forms, and some Protozoa
Staphylococci, Enterococci, Pseudomonas spp., and Enterobacteriaceae
Tetracyclines
Doxycycline fewer side effects
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Readily absorbedNarrow spectrum Clarithromycin New derivatives Azithromycin Dirithromycin
Azithromycin
Aerobic bacteria (e.g., Staphylococci, Streptococci, Helicobacter spp.) and anaerobes. Mycoplasma spp., Intracellular organisms (e.g., Bartonella spp. Toxoplasma spp.), and atypical Mycobacteria
Oral absorption of azithromycin is high, and it is well tolerated. The drug achieves extremely high tissue concentrations and needs to be given only once daily
Erythromycin
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LincomycinGram pathogens, including staphylococci, streptococci, clostridia, several Actinomyces spp., and some Nocardia spp.very effective against many anaerobic bacteria. Against Toxoplasma gondii, Neospora, and staphylococcal osteomyelitis but ineffective against Gram bacteria.
often is used to treat infections resistant to penicillins and erythromycin or patients that cannot tolerate those drugs.
Clindamycin
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Effective against Gram and Gram bacteria, including Enterobacteriaceae and pseudomonads, and have a synergistic effect with β-lactam antibiotics but …
Anaerobes Resistant
lipid insoluble but pleural fluid, bone, joints and peritoneal cavity
Dehydration, electrolyte loss, preexisting renal disease, and concurrent use of other nephrotoxic drugs increase nephrotoxicity of aminoglycosides and NSAID
Aminoglycosides
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Enrofloxacin DifloxacinFluoroquinolones Ciprofloxacin Ofloxacin Marbofloxacin
Potentiated sulfas Trimethoprim-sulfa
Inhibition of DNA Synthesis
Fluoroquinolones 15
Trimethoprim-sulfonamid : osteomyelitis, prostatitis, pneumonia, tracheobronchitis, pyoderma, urinary tract infections
Metronidazole
Anaerobic bacteria
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multidrug-resistant (MDR) Infections
Vancomycin, Carbapenems , Oxazolidinone Linezolid , Streptogramin combination of Dalfopristin and Quinupristin , Tigecycline , Lipopeptide Daptomycin , newest Fluoroquinolones Moxifloxacin fourth- and fifth generation Cephalosporins
DRUGS OF LAST RESORT
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Dosages of New or Commonly Used Antibiotics in Veterinary Medicine 18
Inappropriate dose frequency, or route of administrationinadequate length of treatmentinappropriate antibiotic selectionpersistence of the cause of infectionantibiotic resistance
incorrect diagnoses depressed host immunity Pharmacokinetics of the drug drug reactions antibiotic antagonism inability of the antibiotic to reach the target tissue
CAUSES OF FAILURE
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Classification of Surgical Wounds
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Classifications of Surgical Infections
1. with primary surgical disease (e.g., osteomyelitis that occurs secondary to an open fracture, pyometra, peritonitis that occurs secondary to gastrointestinal perforation, or prostatic abscessation)
2. as a complication of a surgical procedure not commonly associated with infection
3. as a complication of support procedures,with
4. prosthetic implants
Prevention of Surgical Infections
Primary objective of aseptic surgery
Factors host factors operating room characteristics of bacterial contaminantsProper atraumatic tissue handling and instrument use are also important in preventing infection
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PROPHYLACTIC USE OF ANTIBIOTICS 23
Antibiotic selectionPrevent or treat infection effective VS at least 80% of probable pathogens
Staphylococcus spp. (especially coagulase-positive S. aureus), E. coli, and Pasteurella spp.
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Antibiotic Selection System involved Cytologic studies Antibiotic reaches target tissue Least expensive, least toxic, and most
convenient to administer Timing of Antibiotic Administration Dose Routes of Antibiotic Administration Duration of Antibiotic Administration
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NOW WHAT ???
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