Severe Streptococcal Infection Following Cat Scratch

Introduction. Cats can transmit bacterial infections to humans through biting and scratching. Streptococcal infections in wounds caused by cat bites or scratches rarely have been reported in the literature. Case Report. The case of severe streptococcal skin infection after a 2-day-old cat scratch of the right arm, elbow, and forearm in a 68-year-old woman is presented herein. Group A β-hemolytic streptococci (GABHS) was isolated from the wound of the patient as well as the oral cavity and claws of the cat; likewise, Escherichia coli also was isolated from the oral cavity and claws of the cat. She was successfully treated with intravenous tigecycline for 2 weeks at a starting dosage of 100 mg daily. Tetanus prophylaxis was performed. Complete remission was observed 3 weeks after beginning treatment. Follow-up visit at 32 months was negative for clinical manifestations. Conclusions. For the first time documented in the literature, GABHS were isolated from the wound of the patient and from the cat’s oral cavity and claws. 

Cats can transmit bacterial infections to humans through biting and scratching. Oropharynx and claws of cats may contain Pasteurella multocida, Bartonella henselae, Moraxella spp, Staphylococcus spp, Streptococcus spp, and anaerobes (eg, Bacteroides spp, Fusobacterium spp, Porphyromonas spp).^1,2 Furthermore, emerging methicillin-resistant S aureus causing infections in pets and humans can be found in the mouths of cats.¹ Other bacteria (eg, Francisella tularensis, Leptospira spp, Listeria spp, and Nocardia spp) are acquired from soil and water.² In addition, Capnocytophaga canimorsus belongs to the normal flora of cats and dogs. It can cause severe infections (cellulitis, endocarditis, meningitis, and sepsis), especially in patients in whom the spleen has been removed.³ 

Streptococcal infections in wounds caused by cat bites or scratches rarely have been reported in the literature. Herein, the authors describe a case of severe streptococcal skin infection in a woman 2 days after sustaining a cat scratch. Group A β-hemolytic streptococci (GABHS) was isolated from the wound of the patient as well as the oral cavity and claws of the cat.

A 68-year-old Caucasian woman was admitted to the Dermatology Unit of the University of Milan, Italy, with a clinical diagnosis of bacterial infection located on the right elbow and forearm. The patient stated that she was in good general health and was not taking any systemic drugs. She also declared that 2 days prior to presentation she sustained a cat scratch. 

About 8 hours after the scratch, an erythematous, infiltrated lesion with pain and fever (≤ 37.8°C) appeared. The patient washed the lesion with sodium hypochlorite and applied gentamicin cream (3 applications/day for 2 days). However, the lesion increased in size and some pustules appeared; likewise, the fever rose to 38.8°C. 

Dermatological examination revealed a wide, erythematous, infiltrated lesion. In the center of the lesion, several pustules of different morphology and size were visible. A round ulcer measuring 1.4 cm in diameter with fibrinous-purulent bed was present (Figure). The patient complained of severe pain and fever (≤ 39.6°C). 

General physical examination revealed right axillary lymphadenopathy. Laboratory examinations showed leukocytosis (23.200 leukocytes/mm³) and increased erythrocyte sedimentation rate (79 mm at the first hour), C-reactive protein (88 mg/dL), and α-1-acid glycoprotein (4.3 mg/mL). All other laboratory tests, including immunological tests, were within normal ranges or negative. 

Three cultures obtained by deep fine-needle aspiration in 3 different areas of the lesion were positive for GABHS. Three cultures for anaerobes were negative; GABHS and Escherichia coli were isolated from the oral cavity and claws of the cat.

The patient was treated with intravenous tigecycline for 2 weeks at a starting dosage of 100 mg daily. This dosage was reduced to 50 mg per day after 10 days. Tetanus prophylaxis was performed. Compresses with sodium hypochlorite also were used. Complete remission was observed 3 weeks after beginning treatment. The patient tested negative for GABHS at her follow-up visit at 3, 6, 9, 12, and 32 months. 

Although cat bites are not always followed by bacterial infections, Aghababian and Conte⁴ recorded bacterial infections in 11 out of 22 cat bites. P multocida was recovered from 6 wounds and S aureus and S viridans were isolated from the remaining wounds.⁴ Talan et al⁵ found that the wounds of 57 patients with cat bites yielded a median of 5 bacterial isolates per culture (range, 0–16). Aerobes and anaerobes were isolated from 56% of the wounds, aerobes alone from 36%, and anaerobes alone from 1%; 7% of cultures were negative. Pasteurella spp were the most frequent isolates (75%); in particular, P multocida subsp multocida and P multocida subsp septica were the most common isolates. Other aerobes included Moraxella spp and Neisseria spp. Anaerobes included Bacteroides spp, Fusobacterium spp, Porphyromonas spp, and Prevotella spp. Isolates not previously identified as human pathogens included Bacteroides tectum, Prevotella heparinolytica, and Riemerella anatipestifer. Erysipelothrix rhusiopathiae was isolated in 2 cases and group F β-hemolytic streptococci in 1 patient.⁵ Also, Bergeyella zoohelcum was associated with cellulitis following cat bites.⁶  

As previously reported, P multocida belongs to the normal oropharyngeal flora of cats^1,2 and are the source of P multocida wound infection and cellulitis in 60% to 80% of cases.⁷ Local and regional complications (abscess, tenosynovitis, bursitis, arthritis, osteomyelitis) are not rare.⁸P multocida subsp septica, P stomatis, and P dagmatis were recovered in skin infections caused by cat bites or scratches in Sweden in 1992.⁸ Three cases of acute necrotizing skin infections following a cat bite or scratch were published in France in 1996, where group A Streptococcus was isolated in 2 patients.⁹ 

Cat scratch disease is usually caused by B henselae. However, it was demonstrated that B henselae serotype Marseille¹⁰ and B clarridgeiae¹¹ are capable of causing cat scratch disease. In addition, Savini et al¹² described a boy who underwent a surgical excision of a cat scratch disease-related inguinal lymphadenopathy in which it was found that multidrug-resistant S pneumoniae grew from the wound. 

Although Streptococcus spp is cited in the literature as a possible cause of wound infections caused by cat bites and scratches, very rare cases of streptococcal infections actually have been reported: S viridans,⁴ groups A and F β-hemolytic streptococci (3 patients),^5,9 and S pneumoniae (1 patient).¹² In the patient reported herein, the authors have described for the first time where GABHS was isolated from the patient’s wound as well as the oral cavity and claws of the cat.  

Affiliation: Department of Pathophysiology and Transplantation, Università degli Studi di Milano, I.R.C.C.S. Foundation, Cà Granda Ospedale Maggiore Policlinico, Milan, Italy

Correspondence: Stefano Veraldi, MD, Dermatology Unit, University of Milan, Via Pace 9, 20122 Milan, Italy; stefano.veraldi@unimi.it 

Disclosure: The authors disclose no financial or other conflicts of interest.