A 55-year-old patient is being brought to your trauma center via air rescue from the beach after being involved in a jet ski accident. Over the radio, you hear that the patient has stable vital signs and an obvious lower extremity deformity. Upon arrival, it is apparent that the patient has suffered a lower extremity open fracture. Due to the patient’s exposure to saltwater, which antibiotics should the patient receive?
Antibiotics in Trauma:
The EAST Practice Management Guidelines define an open fracture as a fracture that communicates with the environment through a break in the skin. Open fractures increase the risk of infection and soft tissue complications. Open fractures are described by the Gustilo Classification and are broken down by size of the associated laceration, degree of soft tissue injury, contamination, and presence of vascular compromise.
The EAST Practice Guidelines recommend systemic antibiotic coverage against gram-positive bacteria as soon as possible after injury in Type I and II open fractures. First-generation cephalosporins are typically indicated in this patient population. Patients experiencing a Type III open fracture should have their antibiotic coverage expanded to include gram-negative organisms (i.e. ceftriaxone monotherapy). When these injuries occur in an aquatic environment, antibiotic therapy should target possible aquatic pathogens.
Trauma, Antibiotics, and the Aquatic Environment:
Special considerations should be given to patients who experience an open fracture in an aquatic environment. Trauma-related wounds exposed to water have a higher infection rate than land-based traumatic injuries and should be assumed to be exposed to aquatic pathogens. Injuries may occur in saltwater or freshwater environments. Depending on the water source, the bacteriology of trauma-associated wounds varies. Vibrio species are most common in saltwater, while Aeromonas hydrophila is the most common organism in freshwater lakes, ponds, and streams. Although special attention is needed in covering these bacteria with the appropriate antibiotics, typical skin flora such as Staphylococcus aureus and Streptococcus pyogenes are still the most common pathogens overall in saltwater and freshwater exposed open fractures.
Vibrio bacteria are motile, halophilic, gram-negative pathogens, which are common in oceans and coastal waterways throughout the world. Vibrio species are also found in brackish water (a combination of saltwater and freshwater). They produce extremely virulent infections and have been associated with severe cellulitis, necrotizing fasciitis, osteomyelitis, and septicemia. Antibiotic regimens that cover most Vibrio species include the combination of a third or fourth-generation cephalosporin (i.e. ceftazidime 2 g intravenous (IV) every 8 hours) plus doxycycline 100 mg every 12 hours. In patients with contraindications to beta-lactam agents, alternatives include fluoroquinolones such as ciprofloxacin 400 mg IV or levofloxacin 500 mg IV ± doxycycline. In these injuries, antibiotics should be initiated as soon as possible. If left untreated, fatality rates for Vibrio vulnificus exceeds 30% at 24 hours and can reach 100% at 72 hours.
Aeromonas species are gram-negative rods found in warm soil, freshwater, and brackish waters. Aeromonas wound infections may occur following freshwater traumatic injuries such as alligators, fish, snakes, leech, and turtle bites. Inadequately treated infections have led to the development of necrotizing myositis, necrotizing fasciitis, and osteomyelitis. Aeromonas hydrophila is inherently resistant to first-generation cephalosporins and penicillins as it produces a chromosomally mediated beta-lactamase enzyme. Antibiotics directed at Pseudomonas coverage should be used empirically as Pseudomonas aeruginosa may also be present. Third or fourth-generation cephalosporins may be used (i.e. cefepime) with fluoroquinolones (i.e. ciprofloxacin, levofloxacin) as an alternative.
Injuries exposed to brackish water require coverage of both Vibrio species and Aeromonas hydrophila.
- Infection rates of wounds exposed to saltwater or freshwater are much higher than those of terrestrial injuries
- Always consider the environment in which an open fracture has occurred to assist in selecting the most optimal antibiotic regimen
- In patients exposed to a saltwater environment, antibiotic coverage should be aimed for Vibrio spp and consists of a third or fourth generation cephalosporin in addition to doxycycline
- In patients exposed to a freshwater environment, antibiotic coverage should be aimed for Aeromonas hydrophila and consists of agents that target Pseudomonas aeruginosa such as a third or fourth-generation cephalosporin or a fluoroquinolone (i.e. ciprofloxacin or levofloxacin)
- While special attention is needed in covering these bacteria with the appropriate antibiotics, typical skin flora such as Staphylococcus aureus and Streptococcus pyogenes are still the most common pathogens overall in saltwater and freshwater exposed open fractures
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