Phenotypic and Genotypic Changes over Time and across Facilities of Serial Colonizing and Infecting Escherichia coli Isolates Recovered from Injured Service Members

Abstract

dEscherichia coli is the most common colonizing and infecting organism isolated from U.S. service members injured during deployment. Our objective was to evaluate the phenotypic and genotypic changes of infecting and colonizing E. coli organisms over time and across facilities to better understand their transmission patterns. E. coli isolates were collected via surveillance cultures and infection workups from U.S. military personnel injured during deployment (June 2009 to May 2011). The isolates underwent antimicrobial susceptibility testing, pulsed-field gel electrophoresis, and multiplex PCR for phylotyping to determine their resistance profiles and clonality. A total of 343 colonizing and 136 infecting E. coli isolates were analyzed, of which 197 (57%) and 109 (80%) isolates, respectively, produced extended-spectrum ␤-lactamases (ESBL). Phylogroup A was predominant among both colonizing (38%) and infecting isolates (43%). Although 188 unique pulsed-field types (PFTs) were identified from the colonizing isolates, and 54 PFTs were identified from the infecting isolates, there was a lack of PFT overlap between study years, combat zones, and military treatment facilities. On a per-subject basis, 26% and 32% of the patients with serial colonizing isolates and 10% and 21% with serial infecting isolates acquired changes in their phylogroup and PFT profiles, respectively, over time. The production of ESBL remained high over time and across facilities, with no substantial changes in antimicrobial susceptibilities. Overall, our results demonstrated an array of genotypic and phenotypic differences for the isolates without large clonal clusters; however, the same PFTs were occasionally observed in the colonizing and infecting isolates, suggesting that the source of infections may be endogenous host organisms.

Pathogens Present in Acute Mangled Extremities From Afghanistan and Subsequent Pathogen Recovery

“…They were all males with a median age 23 years (min-max, [19][20][21][22][23][24][25][26][27][28][29][30], and all were injured by dismounted improvised explo sive devices with three suffering minor bums of less than 2% full-thickness. All survived to discharge from military treatment facilities in the United States.…”

“…Initial screening for multidrug resistance (MDR) revealed an 11% colonization rate with ESBLproducing Escherichia coli among healthy deployed personnel in Afghanistan.2'1 Despite the introduction of MDR pathogens into the facility, there does not appear to be substantial clonality between infecting or colonizing E. coli isolates. 26,27 However, to date, no surveillance study has been performed in Afghanistan to replicate the acute wound colonization studies that were carried out during the Vietnam War or during the early years of the war in Iraq. 28,29 This study assessed wound colonization among patients with mangled lower extremities at the time of initial presentation to NATO Role 3 facilities with cultures preand postamputation and then serially through the patient's medical care until discharge from a Role 5 facility.…”

Lessons of war

“…(30, 34,51,54, 55, 72, 73) During OIF, an outbreak of ABC infections noted in U.S. military service members resulted in providers using increasingly broad spectrum antimicrobials, primarily imipenem, at the point of injury and continued through level II and III hospitalizations. (personal communication, Clinton K. Murray (CKM), (20, 74, 75)) Ultimately, outbreak investigations determined the source to be nosocomial transmission from a reservoir of host nation patients with prolonged hospitalizations, higher rates of pre-existing colonization with MDR gram-negative pathogens, and environmental contamination.…”

“…(80) Rates of MDR gram-negative colonization, increased from 7% at LRMC to 12% at participating CONUS institutions,(55) without evidence of clonality in these isolates. (54) Instead, this likely reflected an increase in pre-injury ESBL-producing E. coli colonization as well as antimicrobial selection pressure that accumulated along the evacuation chain. (30, 54, 81) In order to combat these increasing rates of resistance, a CPG was released in 2008 emphasizing the avoidance of unnecessarily broad-spectrum antimicrobials (especially imipenem) which resulted in an improved compliance rate in antimicrobial prescribing, especially in relation to penetrating abdominal wounds (increased from 10% to 68%) and closed injuries (from 52% to 80%).…”

Emerging Infectious Diseases and Antimicrobial Resistance (EIDAR)

“…[28][29][30][31][32] Colonization with and infections caused by multidrug-resistant organisms (MDROs) appear common and have a significant impact on military populations. [33][34][35][36][37] In addition, MDRO infections further complicate the care of wounded warriors, are associated with high morbidity and mortality, and add substantial and avoidable costs to the healthcare system due to prolonged and costlier treatments, longer hospital stays, and additional patient visits.…”