MRSA infection

Sir, methicillin-resistant Staphylococcus aureus is no longer only a hospital-based infection. This infection is now arising from community-based sources, and there are many problems with treatment.¹ The following case describes an incidence of MRSA dental-cause infection of the submasseteric space arising in the community and discusses the implications of finding MRSA in an orofacial abscess.

A 49-year-old medically well male presented with a three week history of persistent facial swelling following uneventful local anaesthetic extraction of the lower left third molar by his dentist. There was marked trismus which created difficulty with intra-oral examination. An initial temperature was recorded of 38°C. A diagnosis was made of left submasseteric space infection, with systemic involvement.

Blood results showed an increase in white blood cells to 10.3 × 10⁹/L, and C-reactive protein level at 65 mg/L, confirming a systemic reaction to infection.

Treatment was instigated immediately with intravenous amoxicillin and metronidazole and IV fluids. The patient underwent incision and drainage of the abscess the following day under general anaesthesia, and a pus sample sent for microbiology. A drain was placed, which was removed two days later and the patient discharged on oral clindamycin and metronidazole.

Three days later microbiology reported a profuse growth of MRSA, sensitive to rifampicin, doxycycline, vancomycin, fusidic acid, gentamicin and resistant to flucloxacillin, erythromycin and trimethoprim. The antibiotic regimen was changed to metronidazole, rifampicin and doxycycline. The patient remained otherwise well, the swelling and trismus gradually resolving.

Methicillin-resistant Staphylococcus aureus (MRSA) is a growing concern around the world. The numbers of staphylococcal-related infections are increasing, as therefore are infection numbers with methicillin-resistant Staphylococcus aureus.² Some Scandinavian countries adopt a 'search and destroy' policy to prevent the spread of MRSA.³ Concern among the public is also growing, with many sensationalised and disproportionate claims in the media about this infective cause. Incidences of MRSA infection have been reported in the medical literature since 1961.

MRSA was previously regarded as a hospital-acquired/hospital-based infection. However, MRSA is now proliferating in the community, due to asymptomatic carriers and possibly preventable vector transmission.¹ Case reports are now emerging of MRSA infections in previously unrecognised situations. Even with new antimicrobial agents, these organisms are still difficult to treat, and carry a mortality rate of 21-23% when compared with methicillin-sensitive Staphylococcus aureus.⁴

This case highlights the importance of increasing awareness of the probability of MRSA infection in dental-related infections and abscesses even within a community setting. This type of infection has previously been unreported in literature searches.

It also illustrates the renewed importance of requesting culture and sensitivity. This allows adjustment of therapeutic agents to those which are most effective.