Dynamic Changes in Microbial Composition During Necrotizing Soft-Tissue Infections in ICU Patients

Identifying patients with difficult-to-treat acute bacterial skin infections

PURPOSE OF REVIEW

The early recognition of acute bacterial skin infections (ABSIs) and their swift and adequate care are the major determinants of success. The features that can hamper or delay surgical and medical management can lead to 'difficult-to-treat' ABSIs.

RECENT FINDINGS

Delayed diagnosis and belated management are the key obstacles to be overcome. Clinicians should be careful about underestimating the severity of ABSIs and overlooking comorbidities, especially immunosuppression. Many conditions can lead to delayed source control, including a misdiagnosis, interhospital transfers, delayed re-exploration, or extensive injuries. Difficult therapeutic issues can occur, including rapidly destructive infections from highly pathogenic microorganisms (Group-A-streptococci, Vibrio spp., Clostridium spp. and Staphylococcus aureus ) or inadequate antibiotic therapy resulting from multidrug-resistant bacteria. Impaired pharmacokinetic capacities of antibiotic agents should also be considered as a source of clinical failure due to insufficient antimicrobial activity at the site of infection.

SUMMARY

Microbiological samples should be used for guiding antimicrobial therapy. Risk factors for multidrug-resistant bacteria should be considered, including local epidemiology and comorbidities. The optimization of antibiotic therapy should be achieved. Optimized care should be achieved through multidisciplinary management involving professionals with sufficient and appropriate training.

Toxic Shock Syndrome: A Literature Review

Toxic shock syndrome (TSS) is a rare, life-threatening, toxin-mediated infectious process linked, in the vast majority of cases, to toxin-producing strains of Staphylococcus aureus or Streptococcus pyogenes. The pathophysiology, epidemiology, clinical presentation, microbiological features, management and outcome of TSS are described in this review. Bacterial superantigenic exotoxins induces unconventional polyclonal lymphocyte activation, which leads to rapid shock, multiple organ failure syndrome, and death. The main described superantigenic exotoxins are toxic shock syndrome toxin-1 (TSST-1) and enterotoxins for Staphylococcus aureus and Streptococcal pyrogenic exotoxins (SpE) A, B, and C and streptococcal superantigen A (SsA) for Streptococcus pyogenes. Staphylococcal TSS can be menstrual or nonmenstrual. Streptococcal TSS is linked to a severe group A streptococcal infection and, most frequently, to a necrotizing soft tissue infection. Management of TSS is a medical emergency and relies on early detection, immediate resuscitation, source control and eradication of toxin production, bactericidal antibiotic treatment, and protein synthesis inhibiting antibiotic administration. The interest of polyclonal intravenous immunoglobulin G administration as an adjunctive treatment for TSS requires further evaluation. Scientific literature on TSS mainly consists of observational studies, clinical cases, and in vitro data; although more data on TSS are required, additional studies will be difficult to conduct due to the low incidence of the disease.

Severe skin infections

PURPOSE OF REVIEW

The incidence of necrotizing soft-tissue infections (NSTI) has increased during recent decades. These infections are still associated with high morbidity and mortality, underlining a need for continued education of the medical community. This review will focus on practical approaches to management of NSTI focusing on antibiotic therapies and optimizing the management of group A streptococcus (GAS)-associated NSTIs.

RECENT FINDINGS

Antibiotic therapy for NSTI patients faces several challenges as the rapid progression of NSTIs mandates broad-spectrum agents with bactericidal action. Current recommendations support using clindamycin in combination with penicillin in case of GAS-documented NSTIs. Linezolide could be an alternative in case of clindamycin resistance.

SUMMARY

Reducing the time to diagnosis and first surgical debridement, initiating early broad-spectrum antibiotics and early referral to specialized centres are the key modifiable factors that may impact the prognosis of NSTIs. Causative organisms vary widely according to the topography of the infection, underlying conditions, and geographic location. Approximately one third of NSTIs are monomicrobial, involving mainly GAS or Staphylococcus aureus . Data for antibiotic treatment specifically for necrotizing soft-tissue infections are scarce, with guidelines mainly based on expert consensus.

Rapid diagnostics for skin and soft tissue infections: the current landscape and future potential

PURPOSE OF REVIEW

Managing antimicrobial therapy in patients with complicated skin and soft tissue infections (SSTI) constitutes a growing challenge due to the wide spectrum of potential pathogens and resistance phenotypes. Today, microbiological documentation relies on cultural methods. This review summarizes the available evidence regarding the clinical input of rapid microbiological diagnostic tools (RMDT) and their impact on the management of antimicrobial therapy in SSTI.

RECENT FINDINGS

Accurate tools are already available for the early detection of methicillin-resistant Staphylococcus aureus (MRSA) in SSTI samples and may help avoiding or shortening empirical anti-MRSA coverage. Further research is necessary to develop and evaluate RMDT detecting group A streptococci (e.g., antigenic test) and Gram-negative pathogens (e.g., multiplex PCR assays), including through point-of-care utilization. Next-generation sequencing (NGS) methods could provide pivotal information for the stewardship of antimicrobial therapy, especially in case of polymicrobial or fungal SSTI and in the immunocompromised host; however, a shortening in the turnaround time and prospective data regarding their therapeutic input are needed to better appraise the clinical positioning of these promising approaches.

SUMMARY

The clinical input of RMDT in SSTI is currently limited due to the scarcity of available dedicated assays and the polymicrobial feature of certain cases. NGS appears as a relevant tool but requires further developments before its implementation in routine clinical practice.

Impact of prior antibiotic therapy on severe necrotizing soft-tissue infections in ICU patients: results from a French retrospective and observational study

Necrotizing soft-tissue infection (NSTI) is a life-threatening pathology that often requires management in intensive care unit (ICU). Therapies consist of early diagnosis, adequate surgical source control, and antimicrobial therapy. Whereas guidelines underline the need for appropriate routine microbiological cultures before starting antimicrobial therapy in patients with suspected sepsis or septic shock, delaying adequate therapy also strongly increases mortality. The aim of the present study was to compare the characteristics and outcomes of patients hospitalized in ICU for NSTI according to their antimicrobial therapy exposure > 24 h before surgery (called the exposed group) or not (called the unexposed group) before surgical microbiological sampling. We retrospectively included 100 consecutive patients admitted for severe NSTI. The exposed group consisted of 23(23%) patients, while 77(77%) patients belonged to the unexposed group. The demographic and underlying disease conditions were similar between the two groups. Microbiological cultures of surgical samples were positive in 84 patients and negative in 16 patients, including 3/23 (13%) patients and 13/77 (17%) patients in the exposed and unexposed groups, respectively (p = 0.70). The distribution of microorganisms was comparable between the two groups. The main antimicrobial regimens for empiric therapy were also similar, and the proportions of adequacy were comparable (n = 60 (84.5%) in the unexposed group vs. n = 19 (86.4%) in the exposed group, p = 0.482). ICU and hospital lengths of stay and mortality rates were similar between the two groups. In conclusion, in a population of severe ICU NSTI patients, antibiotic exposure before sampling did not impact either culture sample positivity or microbiological findings.

Antibiotics in Necrotizing Soft Tissue Infections

Necrotizing soft tissue infections (NSTIs) are rare life-threatening bacterial infections characterized by an extensive necrosis of skin and subcutaneous tissues. Initial urgent management of NSTIs relies on broad-spectrum antibiotic therapy, rapid surgical debridement of all infected tissues and, when present, treatment of associated organ failures in the intensive care unit. Antibiotic therapy for NSTI patients faces several challenges and should (1) carry broad-spectrum activity against gram-positive and gram-negative pathogens because of frequent polymicrobial infections, considering extended coverage for multidrug resistance in selected cases. In practice, a broad-spectrum beta-lactam antibiotic (e.g., piperacillin-tazobactam) is the mainstay of empirical therapy; (2) decrease toxin production, typically using a clindamycin combination, mainly in proven or suspected group A streptococcus infections; and (3) achieve the best possible tissue diffusion with regards to impaired regional perfusion, tissue necrosis, and pharmacokinetic and pharmacodynamic alterations. The best duration of antibiotic treatment has not been well established and is generally comprised between 7 and 15 days. This article reviews the currently available knowledge regarding antibiotic use in NSTIs.