Cellulitis case study

Case A 27-year-old man presents to the emergency room complaining of pain in his right hand. He was well until the previous day, when he sustained a deep scratch at the base of his right thumb while playing with his cat. He washed the wound and bandaged it tightly to stop the bleeding. Overnight, however, his palm began to swell, turned red, and became increasingly painful. His blood pressure is 120/70 mm Hg, heart rate is 90 beats per minute, respiratory rate is 12 per minute, and temperature is 38.5°C (101.3°F). Physical examination findings are notable for a laceration on the right thenar eminence that is 2 cm long and 0.5 cm deep. The wound is partially crusted over with blood, with a small amount of serosanguineous discharge. The surrounding tissue is erythematous, hot, and exquisitely tender. There are two red streaks ascending the lower half of his anterior forearm. He has a tender, mobile, 1-cm lymph node in the right axilla. There is full range of motion without discomfort in any of the digits or the wrist of his right upper extremity. Neurologic examination of the hand reveals normal findings, and Allen's test result is normal. The following laboratory data are found: white blood cell count, 15,000/mm 3 , with a differential count of 75% polymorphonuclear leukocytes, 5% band forms, 17% lymphocytes, 2% monocytes, and 1% eosinophils. His serum chemistry values are normal. A radiographic study of the hand reveals no evidence of a foreign body or subcutaneous emphysema. Gram's staining of the serosanguineous discharge from the wound reveals large numbers of small gram-negative rods and a few gram-positive cocci in chains. Samples of the discharge and blood are sent for culture. The patient was born and raised in the United States. He has been in good health before this illness and has no history of hospitalizations. He recalls having had a tetanus booster shot 7 years ago. He has no history of allergic reactions to medications. His 7-year-old cat was also born and raised in the United States, has received all appropriate vaccinations, and is apparently healthy.

Q . What infectious agents should be considered as possible causes of this patient's cellulitis?

Q . What would be the most appropriate antibiotic treatment for this patient?

Q . In addition to antibiotics, what other measures should be taken to treat this cellulitis?

Case Discussion

Q .What infectious agents should be considered as possible causes of this patient's cellulitis?
Group A streptococci and S. aureus must always be considered as potential causes of cellulitis because they are the most common etiologic agents. In the event of animal bites or scratches, the oral flora of the animal may be an important source of infection as well. Pasteurella multocida is found in the oropharynx of 50% to 70% of healthy cats and 12% to 60% of healthy dogs. This gram-negative rod is frequently implicated in infections resulting from cat bites or scratches, and is found less often in wounds inflicted by dogs. Other important animal oral flora to consider in patients with bites and scratch wounds include aerobic and anaerobic streptococcal organisms, as well as gram-negative anaerobes such as Bacteroides species and Fusobacterium. Organisms found in soil, such as Clostridia species, may also be transmitted by scratches or bites. The rapid tempo of this patient's illness, with the development of an exquisitely painful cellulitis within 24 hours of a cat scratch, is characteristic of P. multocida infection, although such a rapid course may also be seen in the setting of streptococcal infections. It would be unusual, however, for a staphylococcal infection to progress this rapidly. Moreover, the discharge from a staphylococcal infection would more likely be purulent than serosanguineous. The finding of many gram-negative rods on the Gram's-stained specimen of the wound discharge also suggests a P. multocida infection, or a gram-negative anaerobic infection. However, a few gram-positive cocci in chains were also found, making streptococcal infection a part of the differential diagnosis .

Q .What would be the most appropriate antibiotic treatment for this patient?
This patient has a serious hand infection, along with an impending systemic illness. Anyone with such a serious hand infection should be hospitalized and receive intravenous antibiotics to prevent advancing infection, as well as to avert the potentially devastating consequences of suboptimal therapy. Penicillin is the drug of choice for P. multocida infections, and would also be effective for the management of both streptococcal and anaerobic infections. Therefore, intravenous penicillin would be the best antibiotic in this case. For patients who are allergic to penicillin, tetracycline is the best alternative drug for the treatment of P. multocida infections. The patient should also be seen in consultation with a hand surgeon to be certain that surgical intervention for drainage or decompression is not required.

Q .In addition to antibiotics, what other measures should be taken to treat this cellulitis?
Overestimating the efficacy of antibiotics, and underestimating the critical roles played by debridement, drainage, wound elevation, and immobilization, are probably the most frequent mistakes made in the treatment of cellulitis. Drainage of a closed-space infection and removal of necrotic tissue are essential for curing any infection. Even when the appropriate antibiotics are administered, an infection can worsen if abscesses or necrotic tissue are not drained or removed. The reason for this is that abscesses and necrotic tissue are not well vascularized, making them inaccessible to both the antibiotics and the host immune mechanisms, such as polymorphonuclear leukocytes and complement, which are normally conveyed through the bloodstream. Therefore, in these inaccessible regions bacteria can freely multiply and, in some instances, such infection can result in sepsis and death despite an appropriate antibiotic regimen. Abscesses tend to develop in the setting of P. multocida infection. In addition, the hand contains several physiologic spaces, such as the thenar eminence, that can serve as pockets of infection. Therefore, a P. multocida cellulitis of the hand may require surgical debridement and drainage. Incision of a hand wound should not be performed by a novice, because there is a great potential for damaging internal structures or creating wounds that would result in serious contractures. A hand surgeon should be consulted for this purpose. The objective of elevation and immobilization in the treatment of cellulitis is to diminish the edema, which impedes the blood flow to an infected region. Elevation of the affected limb above the level of the heart is necessary to achieve optimal results. In the event of a lower extremity cellulitis, merely placing the affected limb on a chair while seated is not adequate because the abdominal contents still exert pressure on the lymphatic vessels in this position, thereby perpetuating the edema. In addition to the measures just described, this patient should receive a tetanus booster shot. Any patient with a bite or deep scratch wound who has not had a tetanus booster shot within the preceding 5 years should receive one.