Epidemiology and antimicrobial susceptibilities of wound isolates of obligate anaerobes from combat casualties

Targeted metagenomic assessment reflects critical colonization in battlefield injuries

IMPORTANCE

Microbial contamination in combat wounds can lead to opportunistic infections and adverse outcomes. However, current microbiological detection has a limited ability to capture microbial functional genes. This work describes the application of targeted metagenomic sequencing to profile wound bioburden and capture relevant wound-associated signatures for clinical utility. Ultimately, the ability to detect such signatures will help guide clinical decisions regarding wound care and management and aid in the prediction of wound outcomes.

Multidrug-Resistant and Virulent Organisms Trauma Infections: Trauma Infectious Disease Outcomes Study Initiative

INTRODUCTION

During the wars in Iraq and Afghanistan, increased incidence of multidrug-resistant (MDR) organisms, as well as polymicrobial wounds and infections, complicated the management of combat trauma-related infections. Multidrug resistance and wound microbiology are a research focus of the Trauma Infectious Disease Outcomes Study (TIDOS), an Infectious Disease Clinical Research Program, Uniformed Services University, research protocol. To conduct comprehensive microbiological research with the goal of improving the understanding of the complicated etiology of wound infections, the TIDOS MDR and Virulent Organisms Trauma Infections Initiative (MDR/VO Initiative) was established as a collaborative effort with the Brooke Army Medical Center, Naval Medical Research Center, U.S. Army Institute of Surgical Research, and Walter Reed Army Institute of Research. We provide a review of the TIDOS MDR/VO Initiative and summarize published findings.

METHODS

Antagonism and biofilm formation of commonly isolated wound bacteria (e.g., ESKAPE pathogens-Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter spp.), antimicrobial susceptibility patterns, and clinical outcomes are being examined. Isolates collected from admission surveillance swabs, as part of infection control policy, and clinical infection workups were retained in the TIDOS Microbiological Repository and associated clinical data in the TIDOS database.

RESULTS

Over the TIDOS study period (June 2009 to December 2014), more than 8,300 colonizing and infecting isolates were collected from military personnel injured with nearly one-third of isolates classified as MDR. At admission to participating U.S. military hospitals, 12% of wounded warriors were colonized with MDR Gram-negative bacilli. Furthermore, 27% of 913 combat casualties with ≥1 infection during their trauma hospitalization had MDR Gram-negative bacterial infections. Among 335 confirmed combat-related extremity wound infections (2009-2012), 61% were polymicrobial and comprised various combinations of Gram-negative and Gram-positive bacteria, yeast, fungi, and anaerobes. Escherichia coli was the most common Gram-negative bacilli isolated from clinical workups, as well as the most common colonizing MDR secondary to extended-spectrum β-lactamase resistance. Assessment of 479 E. coli isolates collected from wounded warriors found 188 pulsed-field types (PFTs) from colonizing isolates and 54 PFTs from infecting isolates without significant overlap across combat theaters, military hospitals, and study years. A minority of patients with colonizing E. coli isolates developed subsequent infections with the same E. coli strain. Enterococcus spp. were most commonly isolated from polymicrobial wound infections (53% of 204 polymicrobial cultures). Patients with Enterococcus infections were severely injured with a high proportion of lower extremity amputations and genitourinary injuries. Approximately 65% of polymicrobial Enterococcus infections had other ESKAPE organisms isolated. As biofilms have been suggested as a cause of delayed wound healing, wound infections with persistent recovery of bacteria (isolates of same organism collected ≥14 days apart) and nonrecurrent bacterial isolates were assessed. Biofilm production was significantly associated with recurrent bacteria isolation (97% vs. 59% with nonrecurrent isolates; P < 0.001); however, further analysis is needed to confirm biofilm formation as a predictor of persistent wound infections.

CONCLUSIONS

The TIDOS MDR/VO Initiative provides comprehensive and detailed data of major microbial threats associated with combat-related wound infections to further the understanding of wound etiology and potentially identify infectious disease countermeasures, which may lead to improvements in combat casualty care.

Infectious Disease Clinical Research Program: Building the Bench

The role of physicians in the U.S. Armed Forces is diverse, encompassing a wide array of skills and responsibilities to provide superior healthcare to their patients and to advance military medicine. In addition to healthcare delivery and medical education, military physicians are engaged in public health, operational medicine, and cutting-edge medical research. Thus, clinical research is a crucial component of Graduate Medical Education (GME) and supports critical thinking (knowledge, skills, and abilities) and the development of leadership skills among U.S. military physicians. The Infectious Disease Clinical Research Program (IDCRP) education mission was established in 2005 with the overall goal of supporting the development and training of the next generation of clinical researchers in infectious diseases and related public health disciplines in the Armed Forces using several strategies, including didactic learning, mentored research, and research engagement. Through involvement in the IDCRP, infectious disease fellows, residents (e.g., surgical, internal medicine, and pediatrics), and Master of Public Health (MPH) students have continued their education and gained valuable skills related to clinical research. Trainees either conduct research with IDCRP mentors or participate in IDCRP-led practicum experiences, with research projects ranging from epidemiologic studies to microbiological assessments. Consistent with the needs of the Military Health System (MHS), and in accordance with Accreditation Council for Graduate Medical Education goals, the IDCRP provides opportunities for medical and graduate students, residents, and infectious disease fellows to conduct mentored research within the MHS, as well as gain important leadership skills in the conduct of clinical research. Overall, IDCRP continues to further infectious disease research through the support and education of the next generation of active-duty infectious disease researchers in the MHS.

Bacteroides Fragilis Vertebral Osteomyelitis and Discitis: "Back" to Susceptibility Testing

Genetic testing of anaerobic isolates can be important for proper antimicrobial stewardship to identify the appropriate narrow-spectrum treatment for a polymicrobial infection.

Bacterial infection during wars, conflicts and post-natural disasters in Asia and the Middle East: a narrative review

Introduction: Bacterial infections resulting from wars and natural disasters represent a major public health problem. Over the past 50 years, Asia and the Middle East have suffered several wars. Moreover, East-Asian countries are considered the most natural disaster-prone countries in the world.Areas covered: This review focuses on bacterial infection occurring during wars and after natural disasters, among refugees, wounded citizens and soldiers as well as the prevention and control measures that must be taken.Expert opinion: During wars, refugees and soldiers represent the two main sources of bacterial infections. Refugees coming from countries with a high prevalence of antimicrobial resistance can spread these pathogens to their final destination. In addition, these refugees living in inadequate shelters can contribute to the spread of bacterial infections. Moreover, some factors including the presence of fixed imported fragments; environmental contamination and nosocomial transmissions, play a key role in the dissemination of bacteria among soldiers. As for natural disasters, several factors are associated with increased bacterial transmissions such as the displacement of large numbers of people into over-crowded shelters, high exposure to disease vectors, lack of water and sanitation. Here, we carry out a systematic review of the bacterial infections that follow these two phenomena.

Microbiology of combat-related extremity wounds: Trauma Infectious Disease Outcomes Study

We present extremity wound microbiology data from 250 combat casualties (2009-2012). Confirmed extremity wound infections (EWIs) were based on clinical and laboratory findings. Suspected EWIs had isolation of organisms from wound cultures with associated signs/symptoms not meeting clinical diagnostic criteria. Colonized wounds had organisms isolated without any infection suspicion. A total of 335 confirmed EWIs (131 monomicrobial and 204 polymicrobial) were assessed. Gram-negative bacteria were predominant (57% and 86% of monomicrobial and polymicrobial infections, respectively). In polymicrobial infections, 61% grew only bacteria, while 30% isolated bacteria and mold. Multidrug resistance was observed in 32% of isolates from first monomicrobial EWIs ±3 days of diagnosis, while it was 44% of isolates from polymicrobial EWIs. Approximately 96% and 52% of the suspected and colonized wounds, respectively, shared ≥1 organism in common with the confirmed EWI on the same patient. Understanding of combat-related EWIs can lead to improvements in combat casualty care.

Field Wound Care: Prophylactic Antibiotics

Adequate management of wounds requires numerous interventions, one of which is the appropriate use of antimicrobials to attempt to minimize the risk of excess morbidity or mortality without increasing toxicity or multidrug resistant bacterial acquisition. There are numerous recommendations and opinions for not only the use of systemic prophylactic antimicrobials, but also the agent, dose, route, and duration. To best address the implementation of systemic antimicrobials in a field scenario, one must weigh the factors that go into that decision and then determine the best agents possible. The epidemiologic triangle (ie, the host, the agent, and the environment) forms the basis for selecting the correct prophylactic antibiotic for field wound care. Extreme conditions can be encountered in both military and nonmilitary systems, requiring a unique selection process to make the right antibiotic choice. A modifiable weighted matrix, recommended previously for point of injury combat casualty care, assists in selecting the best oral and intravenous/intramuscular agent based on the epidemiologic risk determination.

Antibiotic efficacy in the complex infection environment

Accurate prediction of antimicrobial efficacy is essential for successful treatment of bacterial infection. Beyond genetically encoded mechanisms of antibiotic resistance, the determinants of antibiotic susceptibility during infection remain poorly understood, and treatment failure is common. Traditional antibiotic susceptibility testing fails to account for extrinsic determinants of antibiotic susceptibility present in the complex infection environment and is therefore a poor predictor of antibiotic treatment outcome. Here we discuss how host-pathogen interaction, microbial interspecies interaction, and metabolic heterogeneity contribute to the success or failure of antibiotic therapy. Consideration of these factors during the treatment of disease will improve our ability to successfully resolve recalcitrant bacterial infection and improve patient health.

Infection After Orthopaedic Trauma: Prevention and Treatment

Trauma to the extremities is disproportionately represented in casualties of recent conflicts, accounting for >50% of injuries sustained during operations in Iraq and Afghanistan. Infectious complications have been reported in >25% of those evacuated for trauma, and 50% of such patients were treated in the intensive care unit (ICU). Osteomyelitis has been reported in 9% (14% of intensive care unit patients), and deep-wound infection in 27% of type III open-tibia fractures. Infections complicating extremity trauma are frequently caused by multidrug-resistant bacteria and have been demonstrated to lead to failure of limb salvage, unplanned operative take-backs, late amputations, and decreased likelihood of returning to duty. Invasive fungal infections of extremities have also presented a unique challenge in combat-injured patients, particularly in those with blast injuries with massive transfusion requirements and high injury severity scores. Infection prevention should begin at the time of injury and, although context-specific depending on the level of care, includes appropriate irrigation, surgical debridement, wound care and coverage, fracture fixation, and antibiotic prophylaxis, in addition to basic infection prevention measures. Clinical practice guidelines to address infection prevention after combat trauma (including extremity infection) were developed in 2007 and revised in 2011, with endorsement from the Surgical Infection Society and the Infectious Disease Society of America. Nevertheless, significant challenges remain, including austere environments of care, multiple transitions of care, and lack of coordinated efforts in prevention. Treatment of established infections is optimally multidisciplinary, particularly when deep wounds, bone, and joints are involved. Surgical debridement of overtly infected or necrotic tissue is necessary, with particularly aggressive margins if invasive fungal infection is suspected. Infected nonunion frequently requires the use of prosthetic materials for fixation, potentiating biofilm formation, and complicating medical therapy. Antibiotic therapy should be targeted at results of deep wound and bone cultures. However, this is complicated by frequent contamination of wounds, requiring differentiation between potential pathogens in terms of their virulence and decreased culture recovery in patient who have frequently received previous antibiotics. Lessons learned in infection prevention and treatment of orthopaedic trauma from combat can serve to inform the care of patients injured in natural disasters and noncombat trauma.