Cases 1 and 2 presented within two days of each other to the same facility. The diagnosis of NF in case 1 was histopathologically based, while the diagnosis of case 2 was based on necrosis of the superficial fascia at the time of exploration. The patients from cases 1 and 2 did not know each other and did not have any other social, work or environmental interactions. NF is a potentially limb- and life-threatening infection, with mortality rates for those receiving inpatient care reported to be as high as 33% (3
). As noted in our introduction, NF can be either mono- or polymicrobial in nature. Physical examination is unhelpful in differentiating between the two types, although a history of intra-abdominal surgery or a 'dirty' wound may serve as an indicator that a polymicrobial necrotizing infection might be occurring. Human bite injuries are often polymicrobial in nature, with the local flora of the mouth and skin, such as Clostridium
species, being the most common isolates (17
). There are a large number of reports concerning NF and its etiology, and an equally large number of reports surrounding the epidemiology of human bite injuries. Despite all of these reports, there are remarkably few accounts of bite-related NF or STSS (Table ). It has been reported that 2.3% of 15- to 44-year-old healthy individuals can asymptomatically carry GAS (18
). Such carriage rates present a possible mechanism of transmission of GAS in this setting.
Reports of necrotizing fasciitis from human bites
A MEDLINE search spanning from 1966 to December 21, 2004, using the search terms "bite" and "necrotizing fasciitis" revealed only four reported cases in addition to the present cases. Also found was one case of STSS without NF arising from a human bite to the penile shaft as a result of oral sex (14
). The paucity of search results could represent either an underreporting or a true rarity of these cases. From Table , it should be noted that for the cases where the time to seek medical attention was reported, the time ranged from 48 h to five days. GAS was recovered from five of the six reported cases; in the single case where GAS was not recovered, the patient had inadvertently bitten his own buccal mucosa, where Streptococcus
species, Bacteroides melaninogenicus
, Bacteroides oris
and Eubacterium aerofaciens
were recovered. With respect to this latter case, the true polymicrobial nature of the microorganisms recovered is comparable with the flora typically found in the mouth. The patients summarized in Table had the diagnosis of NF established clinically at the time of surgery, histopathologically or using a combination of the two techniques. These patients received a variety of different antimicrobial regimens, which likely reflect the vintage of the cases reported, the background of the treating physicians, and local therapeutic practices. All but one of these summarized patients survived; however, the patient who died had a course complicated by shock, extensive skin and soft tissue debridement, and respiratory failure. Why this patient had such a complex course with a poor outcome is unclear, particularly when the other cases had seemingly more limited infections arising from what appear to be similar injuries. This may be related to the intrinsic virulence of the pathogens involved in the cases; unfortunately, data about strain types are unavailable for these cases.
In both previous reports (11
) and the cases outlined in the present article, the source of the GAS is unclear; however, it is speculated that the organism originated from the throat/oropharynx of the person initiating the bite (assailant). In addition to GAS arising from the oropharynx of the assailant, there remains the possibility that GAS may have been on the skin of the person sustaining the bite injury (victim), with inoculation of the deep tissues occurring at the time of the bite. Unfortunately, the collection of GAS from the throat swabs of the assailant and victim was not attempted in previous reports (11
) or in the present cases; these specimens would have provided definitive support for oral pharyngeal carriage of GAS serving as the source for the microorganism responsible for the victim's NF.
Cases 1 and 2 are important reminders that GAS can be inoculated through bite wounds, possibly from the oropharynx of the assailant or, alternatively, from the skin of the person who was bitten. Therefore, it is important to consider NF as a potential complication of a bite injury, a complication which may have catastrophic consequences (15
). Bite wound infections are typically thought of as mixed with aerobes, particularly alpha-hemolytic streptococci, Staphylococcus aureus
and anaerobes, which is what was observed in the patient who bit his own cheek (13
). In a recent report (17
), 14% of 50 patients presenting with infected human bites had GAS recovered from their wounds. GAS may indeed play a larger role than had previously been suspected. In a recent comprehensive clinical and bacteriological analysis of infected human bites in patients presenting to emergency departments (17
), NF was not recorded among any of the 50 patients reviewed, which may represent underreporting or, alternatively, the true rarity of bite-related NF.
When initiating antibiotic treatment for suspected NF of GAS origin, it is important to ensure that penicillin - a highly effective agent against GAS - is included in the treatment regimen. Evidence for the concurrent use of clindamycin exists (primarily from animal models). However, human trials to validate the effect of antimicrobial agents in arresting protein synthesis with efficacy currently do not exist (22
). In addition to arresting toxin production by interfering with protein synthesis, the antibacterial spectrum of clindamycin targets S aureus
and anaerobes. When considering injuries of the perineum, it may be prudent to also include antimicrobial agents effective against Gram-negative organisms and anaerobic species because it is clinically impossible to establish the microbiology of complicated skin and soft tissue infections (2
). In case 2, the treating physician was concerned about the potential for a polymicrobial infection; as a result, therapy was initiated. Although this therapy may not have been optimal for targeting GAS (as penicillin was absent), it was still sufficient to target the majority of Gram-positive and Gram-negative organisms and anaerobic species that may have potentially caused polymicrobial infection.
Cases 1 and 2, along with those found after reviewing published reports, serve as a reminder that NF may indeed occur after bites, with the source of the inoculated microorganism being either the oropharynx of the assailant or the skin of the victim itself. NF should therefore be considered in the differential diagnosis of bite-related infections.