Which antibiotic should you prescribe to treat this condition?The mother of a 16-year-old girl calls you when you are on call on a Saturday afternoon. The mother states that her daughter was stung by a wasp about 2 hours ago on her left arm. The patient has no known history of previous allergic reactions to insect bites or stings. She is having no difficulty breathing or swallowing, nor has she been dizzy or light-headed. The mother’s primary concern is that the area of the sting is red and swollen. The daughter says that it hurts and itches. She says that the site of the injury was the midpoint of the forearm and there is now redness and swelling extending in a circular pattern that is about 3 in across. The red area is hot to the touch, so the mother is concerned that it is infected. She gave her daughter some ibuprofen for the pain and would like you to phone in some antibiotic and something to prevent the reaction from spreading.
Which antibiotic should you prescribe to treat this condition?
What other treatments might be beneficial at this point?
What immunization is appropriate for this patient?
Summary: A 16-year-old adolescent girl has been stung by a wasp and is having a painful, itchy local reaction. She has no history of previous allergic reactions. The patient’s mother is calling and asking you to manage the situation over the phone.
• Most appropriate antibiotic to use: No antibiotic treatment is indicated, as this is a local reaction.
• Other therapy that may be beneficial: Local applications of ice, nonsteroidal anti-inflammatory drug (NSAID) or acetaminophen for pain, and antihista-mine for itching.
• Immunization that is appropriate: Tetanus-diphtheria booster, if not up-to-date.
1. Know the insects that commonly cause bite and sting injuries.
2. Be able to differentiate local from systemic reactions to bites and stings.
3. Know the management of common animal-bite injuries.
This adolescent without allergies has received a wasp sting, and no therapy is needed other than symptomatic treatment. The insect order Hymenoptera includes wasps, yellow jackets, hornets, honeybees, bumblebees, and fire ants. These insects cause the majority of cases of sting- or bite-induced anaphylaxis and cause more mortality than all other types of insect bites and stings. Local reactions occur as a result of the toxic properties of the venom, whereas more severe reactions tend to be caused by allergic reaction to venom allergens.
Several types of bee stings result in retention of the stinger in the victim, which can result in continued injection of the bee venom. Stingers should be promptly removed. Grasping the base of the stinger may result in compression of a venom-containing sac, resulting in increased venom release. Thus, it is suggested that scraping or brushing the stinger off of the skin is preferable to grasping the stinger. However, rapidly removing the stinger is preferable to taking the time to locate a scraping implement if one (such as a credit card or driver’s license) is not immediately at hand.
HYMENOPTERA: Order of insects which includes wasps, yellow jackets, hornets, honeybees, bumblebees, and fire ants, and make up the majority of insect stings.
LARGE LOCAL ALLERGIC REACTIONS: Redness or warmth of the skin at the area of insect sting, mediated by immunoglobulin (Ig) E reactive to the Hymenoptera venom.
Almost all Hymenoptera stings will result in a local reaction, which includes redness, swelling, pain, and itching at the site of the injury. These reactions tend to occur almost immediately and last for a few hours. The local tissue response is a consequence of a histamine-like reaction caused by the venom that is released by the sting. Local reactions can be treated with ice and antihistamines for itching. Tetanus prophylaxis should be provided for those who have not been vaccinated.
Large local allergic reactions are mediated by immunoglobulin (Ig) E reactive to the Hymenoptera venom. These reactions are often confused with cellulitis, as large areas (≥10 cm in diameter) of redness and warmth develop over 24 to 48 hours. These reactions are not infectious and will not respond to antibiotics. These reactions are best treated with oral steroids initiated early after the sting. Tetanus prophylaxis should be reviewed and updated if necessary. A person with a history of a large local reaction to a bee sting is likely to have similar reactions to subsequent stings. However, the history of this type of reaction does not result in an increased risk of anaphylaxis to subsequent stings.
Up to 4% of the population may have a systemic reaction to a Hymenoptera sting. Those who have had a systemic reaction have a 50% or greater risk of having a systemic reaction to future stings. These systemic reactions can vary from milder symptoms of nausea, generalized urticaria, or angioedema to severe and life-threatening hypotension, shock, airway edema, and death. Severe immediate-hypersensitivity reactions usually occur within minutes of the sting.
Treatment of anaphylaxis should include assessment and management of the ABCs (airway, breathing, and circulation), with intubation, if necessary, IV access, and fluid resuscitation at 10 to 20 mg/kg (usually 500-1000 cc) as soon as possible. Subcutaneous or intramuscular injection of 0.3 to 0.5 mL of 1:1000 solution of epinephrine should be given as quickly as possible and repeated in 10 to 15 minutes if needed. Antihistamines, steroids (if severe), and bronchodilators may be required as well. Anyone with an anaphylactic reaction should be observed in a hospital setting for 12 to 24 hours, as the symptoms can recur. Persons with known anaphylactic reactions should be prescribed epinephrine injector kits to carry with them for immediate access at all times. They should be instructed to avoid wearing perfumes, bright clothing, and avoid walking barefoot. Desensitization therapy can also be offered to those with known anaphylaxis, as their risk of future severe reactions can be reduced by up to 50%.
Nearly five million animal bites occur in the United States each year. The most common animals involved are dogs, cats, and humans.
The initial management should focus, as always, on the ABCs and on protection of the current injury (splinting of fractures, protection of cervical spine, etc), as well as control of bleeding and assessment of the injuries incurred. History should be gathered on the type of animal involved in the bite, the situation regarding the bite (whether provoked or unprovoked), and the vaccination status of the animal, particularly to document rabies vaccination status. Almost all cases of human rabies in the United States since 1960 have been caused by bats, skunks, dogs, and foxes. Consultation with your local health department after animal bites is recommended.
Local cleaning of the wound(s) with soap and water, irrigation with saline, and debridement of devitalized tissue should take place as soon as possible. Often, for minor wounds, these treatments are all that is needed.
The risk of infection is dependent on numerous factors. Larger and deeper wounds are more likely to become infected than smaller, superficial wounds. Hand wounds also tend to have an increased risk of infection. Host factors, such as the presence of chronic illnesses or immune suppression, also play a role. The animal involved in the bite is important. Approximately 20% of dog-bite wounds become infected, whereas cat and human bites have a higher occurrence of infection.
Many different bacteria can be involved in bite wound infections. Both cats and dogs can carry staphylococci, streptococci, anaerobic species, and Pasteurella species. Humans carry staphylococci, streptococci, Haemophilus species, Eikenella species, and anaerobes.
The treatment of bite wounds starts with local care—cleaning, irrigation, and debridement. The primary closure of bite wounds is controversial and should be limited to lacerations less than 24 hours old. Deep puncture and wounds with signs of infection should not be primarily closed. Tetanus vaccination should be updated in those patients as needed. Animal control authorities should be contacted for guidance regarding rabies vaccination.
Although clear evidence of efficacy is lacking for dog and cat bites, current recommendations are for antibiotic prophylaxis for 5 to 7 days for patients with moderate to severe wounds from dog, cat, or human bites. Amoxicillin-clavulanate (Augmentin) given orally is an appropriate prophylaxis for most bite wounds. When cellulitis is present, longer courses of antibiotic, usually 7 to 14 days, are required. Hospitalization and surgical intervention may be required for more severe infections, osteomyelitis, joint infections, and in patients with complicating medical conditions.
43.1 Which of the following therapeutic options is useful in treating both bee stings and bite wounds?
A. Antibiotic prophylaxis with amoxicillin-clavulanate
B. Antihistamines for itching
C. Tetanus vaccination
D. Surgical wound debridement
43.2 A 22-year-old woman develops a progressively enlarging red, hot area on her leg following a yellow jacket sting. She states that the sting was sharp and of brief duration and she was able to fully remove the stinger with tweezers. She did not suffer from any systemic anaphylaxis. She has no previously known allergies. She sees you in the office a day after the sting and says that the lesion is still enlarging despite using over-the-counter corticosteroid cream and a first-generation antihistamine. Which of the following is the most appropriate treatment for this patient?
A. Oral prednisone
B. Topical corticosteroid
C. Antibiotic directed against gram-positive cocci
D. Portable epinephrine kit for future stings
E. Reassurance
43.3 You see a 7-year-old boy a day after he was bitten by his pet dog. According to the mother, the dog bit the child after he snuck up on the dog and grabbed its tail. The dog has had all its vaccinations, including rabies. The child has had no fever, has full movement of the injured limb, and has no sign of neurologic or vascular injury. The wound is on the child’s forearm, is not deep, and is not bleeding, but has developed about 2 cm of erythema surrounding the site. Which of the following is the most appropriate treatment?
A. Hospitalization for IV antibiotic
B. Oral amoxicillin-clavulanate for 3 to 5 days
C. Oral amoxicillin-clavulanate for 7 to 14 days
D. Local care without any antibiotic
43.4 You see a 43-year-old man who 2 days prior was in a fist fight and sustained a deep laceration wound around the knuckles from where he struck the face of another man. He was intoxicated at the time and upon return home he did not clean the wound and went straight to sleep. He now has purulent drainage, pain, erythema, and fever. There is no rash and he has not noted any spreading of the erythema. An x-ray of the hand shows a hairline fracture of the fifth metacarpal with swelling and bruising noted over the affected area. Which of the following is the most likely organism causing infection?
A. Staphylococcus aureus
B. Streptococci
C. Eikenella corrodens
D. Escherichia coli
E. Peptostreptococcus
43.5 A mother brings in her 6-year-old child, who was bitten on the hand while playing with a rabbit that was recently obtained from a neighbor. The child’s wound is on the volar surface of the right second finger just distal to the proximal interphalangeal joint. Which of the following steps in the management of bite wounds is most effective in preventing wound infection?
A. Tetanus prophylaxis
B. Rabies prophylaxis
C. Saline irrigation and wound care
D. Prophylactic antibiotics
E. Irrigation and primary closure
43.1 C. Tetanus vaccination is common to the management of both bee stings and bite wounds. Bee stings rarely become infected and do not require antibiotic therapy.
43.2 A. This patient is having a large, local reaction to her sting. This is an IgE-mediated reaction. It may respond to a course of oral steroids. There is at least a 50% chance that a similar reaction will occur if she were stung again, but she is unlikely to develop anaphylactic reactions in the future and does not need anaphylaxis prophylaxis. Her history of a sting makes cellulitis less likely.
43.3 C. This child is developing cellulitis from the bite wound. Based on his presentation, he does not appear to require hospitalization. He can be treated with oral antibiotics for 1 to 2 weeks.
43.4 C. While each of these bacteria can be isolated in injuries from human bites, Eikenella species appear to be most common in closed fist injuries.
43.5 C. Rodents and lagomorphs (rabbits) are neither reservoirs of the rabies virus nor have been shown to transmit the rabies virus to humans. The most important step in preventing the infectious complications of bite wounds is proper wound care with inspection, irrigation, and debridement. Tetanus prophylaxis should be considered in all bite wounds. Antibiotic prophylaxis may also be indicated especially in high-risk bites (those located on the hand, late presentation, cat bites) and should be directed against staphylococci, streptococci, anaerobes, and Pasteurella species as appropriate.
Anyone with a history of anaphylactic reactions should be given a prescription for an epinephrine injector kit and instructed in the importance of keeping it at hand. These prescriptions need to be updated often, as the medication expires in 6 to 12 months.
Amoxicillin-clavulanate (Augmentin) given orally is an appropriate prophylaxis for most bite wounds.
Local cleaning of the wound(s) with soap and water, irrigation with saline, and debridement of devitalized tissue should take place as soon as possible.
Human “bite” wounds are not always the result of a bite. A punch to the mouth can cause a serious inoculation and infection to the knuckles of the puncher.
Approximately 20% of dog-bite wounds become infected, whereas cat and human bites have higher rates of infection.
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Manning SE, Rupprecht CE, Fishbein D, et al. Human rabies prevention-United States 2008: recommendation of the Advisory Committee on Immunization Practices; CDC. MMWR Recomm Rep. 2008;57:1-28.
Tintinalli JE, Powers RD, Schwab RA, et al. Puncture wounds and bites. Bites and Stings. Tintinalli’s Emergency Medicine: A Comprehensive Study Guide. 7th ed. New York, NY: McGraw-Hill; 2011: Chapters 50 and 205. Available at www.accessmedicine.com. Accessed May 6, 2011.
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