Necrotising fasciitis, invasive Group A Streptococcus (iGAS) infection; a case series of 8 patients requiring surgical debridement in one trauma unit within 9 months

Abstract

Necrotising fasciitis (NF) is a rare but life-threatening skin and soft tissue infection. It requires urgent surgical debridement. The most common cause of monomicrobial NF is invasive Group A Streptococcus (IGAS). We present eight patients who were all treated in a single trauma unit within a 9-month period. All cases required surgical debridement and had positive microbiology testing for IGAS. The eight patients did not present typically for NF, nor did they all have typical risk factors for the development of NF. The in-hospital mortality rate was 37.5%. This series represents an epidemiological spike of IGAS infections causing NF. The findings from this series could inform future practice if similar spikes were to be encountered.

Introduction

Necrotising fasciitis (NF) is a rare but life-threatening skin and soft tissue infection which requires urgent surgical debridement. Its incidence in the United Kingdom is estimated to be 500 cases a year with a global prevalence of 0.4 cases per 100 000 population [1, 2]. The variation of causative organisms can lead to difficulties in diagnosis but Group A Streptococcus is the most common cause of monomicrobial NF [3].

Group A Streptococcus is a human-specific facultative anaerobic bacterium that causes high morbidity infections in the skin and upper respiratory tract [4]. Invasive Group A Streptococcus (iGAS) infection is defined as cultures of Group A Streptococci from a normally sterile site. Infection can occur following a direct penetrating trauma or surgical incision. However, in up to 45% of cases, there is no direct injury [5, 6].

There are numerous comorbidities that can increase the risk of NF. These risk factors include immunosuppressive therapy, malignancy, peripheral vascular disease, liver disease, malnutrition and increasing age. Diabetes mellitus is the prevalent comorbidity associated with NF [7], and it is also three times more common in males than females [8].

Clinical diagnosis of NF is challenging with a range of manifestations which include localized pain, swelling and erythema. NF typically results in poorly defined margins of erythema which can rapidly spread within minutes to hours. It the later stages of NF other cutaneous features may be present such as crepitus on palpation, bullae and necrosis. Patients may also present with features of systemic infection and sepsis [9].

In cases where there is uncertainty in diagnosis there a number of clinical adjuncts which can be used. The Laboratory Risk Indicator for Necrotising Fasciitis (LRINEC) score consists of serum concentration CRP, haemaglobin, creatinine, white blood cells, glucose and sodium. A score of more than or equal to 6 indicates a high chance of NF with a positive predictive value of 92% [9]. The finger sweep test can also be performed. Under local anesthesia an incision is made down to fascia in the affected tissues. If the tissue can be dissected using the finger with minimal resistance, then a diagnosis of NF is likely [10].

By whichever means the diagnosis is made it is imperative that surgical debridement is undertaken expediently. NF carries an overall mortality rate of 34%, which increases to 70% once patients are diagnosed with symptoms of systemic toxicity. The mortality rate is nine times greater in patients who are not operated on within 24 hours of initial presentation [1].

Surgical debridement should include all the infected skin, fat and fascia at the first operation [11]. Intraoperative findings may include liquefied subcutaneous fat, dishwater fluid, muscle necrosis and venous thrombosis. Intravenous antibiotic therapy should be used in combination with surgical debridement and should be broad spectrum with adequate anaerobic cover [12]. Intravenous immunoglobulins (IVIg) should be used in the management of IGAS NF. IVIg can result in the binding of exotoxins produced by staphylococcal and streptococcal bacterial infection, thus reducing the complications of systemic toxicity [13].

The diagnosis of NF is largely considered to be rare and would typically affect those with identifiable risk factors. However, we present a series of eight patients who all presented within a short period of time in just one trauma unit. These presentations were not considered typical, but all were found to be positive for IGAS. The purpose of this series is to highlight an epidemiological spike in infections with the objective of informing future practice if further spikes are to be repeated.

Materials and methods

Eight patients (Table 1) required surgical debridement for NF in one trauma unit within a 9-month period between August 2022 an May 2023. This level II trauma department serves a population of approximately 60 000 people and is run by Orthopaedic surgeons without onsite Plastic surgeons. Cases were identified retrospectively using electronic patient records. All cases required Orthopaedic surgical debridement, and all grew IGAS from microbiological sampling. Cases were excluded if the streptococci were isolated from a mixed flora with more than two species or if the infection affected the trunk or genital area.

Results

Median age at presentation of NF caused by IGAS was 61.5 years (range 6–79 years). There were two males and six females. Six patients had NF affecting their upper limbs, and in two patients, it affected their lower limbs. Two patients were on immunosuppressive medications. One patient was an intravenous drug user and one patient had type II diabetes mellitus. Five out of the eight patients had no identifiable risks factors for developing NF. In fact, one patient was only 6 years old with no medical history at all. Three patients had a history of some form of trauma, while the remaining five cases were all atraumatic. Among the three instances of traumatic NF, one patient exhibited mild, non-penetrating trauma, while the remaining two cases were attributed to penetrating trauma.

Seven out of eight had an LRINIC laboratory score ≥ 6 (Table 2). All eight patients grew Group Strep A from tissue samples taken during surgical debridement. Only three patients had positive blood culture results for Group A Strep. Six patients presented with signs of staphylococcal toxic shock syndrome (STSS) defined as fever, rash, hypotension and end-organ damage [14]. Seven patients were found to have infection and necrosis extending from the subcutaneous tissue to the muscle.

Surgical treatment within 24 hours of admission was performed in seven out of eight patients (Table 3). The mean time to initial surgery was 16.5 hours (range 5.8–29.25 hours). Seven out of eight patients were treated with IVIG in addition to broad spectrum antibiotics. The in-hospital mortality rate was 37.5%. The surviving patients were all transferred to a different hospital after adequate debridement to undergo reconstructive plastic surgery. The mean age of the survivors was 13.4 years younger than the non survivors.

Discussion

The mortality rate of 37.5% within this series is consistent with the existing literature and further illustrates the gravity of this rare but life threatening condition [1] . In the post COVID-19 era, there appears to have been a national and international increase in other series forms of infection such as IGAS [15]. This series demonstrates how this this apparent spike can cause significant skin and soft tissue infection, which may not have previously been appreciated.

From a clinical point of view, this spike posed a number of operational challenges for the trauma unit in question. As aforementioned, NF is considered to be rare but the treatment is radical surgical debridement. This is therefore a significant clinical decision to be made and the frequency of presentation in the short time highlighted the importance of multi-disciplinary team working as the decision making was coordinated between Orthopaedic surgeons, Intensivists, Microbiologists and even Paediatricians in one case. In addition, from a practical sense during the spike of infections, it was found that there was a resultant depletion in the stock of Jelonet and gauze, which were necessary to dress post debridement wounds. Consequently, an ‘NF kit’ was developed to always be left in theatre for such cases. Furthermore, a Standard Operating Precure was introduced to aid in future diagnoses and management pathways.

Conclusion

What we wish to highlight in this case series is our experiences of this unexpected spike in infections, which affected patients who we may not previously have anticipated would suffer with such severe infections. It is hoped that our experiences would inform future practice to improve diagnosis and management of this significant condition and improve patient care.

Conflict of interest statement

None declared.

Funding

None declared.

References