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Reports of organisms harboring multiple carbapenemase genes have increased since 2010. During October 2012-April 2019, the Centers for Disease Control and Prevention documented 151 of these isolates from 100 patients in the United States. Possible risk factors included recent history of international travel, international inpatient healthcare, and solid organ or bone marrow transplantation. [ABSTRACT FROM AUTHOR]

Summary: Disruption of homeostasis between the host immune system and the intestinal microbiota leads to inflammatory bowel disease (IBD). Whether IBD is instigated by individual species or disruptions of entire microbial communities remains controversial. We characterized the fecal microbial communities in the recently described T-bet −/− ×Rag2 −/− ulcerative colitis (TRUC) model driven by T-bet deficiency in the innate immune system. 16S rRNA-based analysis of TRUC and Rag2 −/− mice revealed distinctive communities that correlate with host genotype. The presence of Klebsiella pneumoniae and Proteus mirabilis correlates with colitis in TRUC animals, and these TRUC-derived strains can elicit colitis in Rag2 −/− and WT adults but require a maternally transmitted endogenous microbial community for maximal intestinal inflammation. Cross-fostering experiments indicated a role for these organisms in maternal transmission of disease. Our findings illustrate how gut microbial communities work in concert with specific culturable colitogenic agents to cause IBD. [Copyright &y& Elsevier]

CTX-M-type β-lactamases are increasing among US Enterobacteriaceae isolates. Of 2,165 non-Typhi Salmonella isolates submitted in 2007 to the National Antimicrobial Resistance Monitoring System, 100 (4.6%) displayed elevated MICs (≥2 mg/L) of ceftriaxone or ceftiofur. Three isolates (serotypes Typhimurium, Concord, and I 4,5,12:i:--) contained blaCTX-M-5, blaCTX-M-15, and blaCTX-M-55/57, respectively. [ABSTRACT FROM AUTHOR]

Colistin is increasingly being used to treat serious infections caused by multidrug-resistant Gram-negative bacteria. With the recent emergence of plasmid-mediated colistin resistance (mcr genes), screening for isolates with phenotypic colistin resistance has become clinically and epidemiologically relevant. However, antimicrobial susceptibility testing (AST) of colistin is associated with several technical challenges. Disk diffusion does not work because of poor diffusion of the large colistin molecule, Etest has been reported to underestimate minimum inhibitory concentration (MIC) values, and most clinical microbiology laboratories lack the capacity to perform broth microdilution (BMD). In this study, we compared the Etest method with the reference BMD method described by the Clinical and Laboratory Standards Institute (CLSI) for determining colistin MICs among Enterobacteriaceae. A total of 114 isolates of Enterobacteriaceae (51 carbapenem-resistant [CRE] and 63 carbapenem-susceptible [CSE]) were selected for colistin AST. One CRE isolate and 13 CSE isolates harbored a mcr gene. BMD testing was performed according to CLSI guidelines using a frozen reference panel with colistin concentrations ranging from 0.25 to 8 µg/mL. The Etest (BioMérieux, Durham, NC) method was performed on Mueller-Hinton agar (BBL, Becton Dickinson, Sparks, MD) according to the manufacturer's instructions. Interpretive criteria based on CLSI epidemiological cutoff values (non-wild-type ≥4 µg/mL; wild-type ≤2 µg/mL) were used to define resistance and susceptibility to colistin, respectively. By BMD, colistin MICs ranged from ≤0.25 to >8 µg/mL and 27% were determined to be colistin-resistant. The categorical agreement between Etest and BMD was 92%. All 14 mcr-positive isolates were categorized as colistin-resistant by BMD, while Etest classified 13/14 as resistant. In conclusion, clinical microbiology laboratories lacking capacity to perform BMD could implement the Etest method with BBL Mueller-Hinton agar for epidemiological purposes to help identify candidate isolates for mcr screening. To determine whether colistin can be used clinically, BMD would still be required. [ABSTRACT FROM AUTHOR]

Background Infections with metallo-β-lactamase (MBL)-producing organisms are emerging in the United States. Treatment options for these infections are limited. We describe MBL genes among carbapenemase positive carbapenem-resistant Enterobacteriaceae (CP-CRE) and Pseudomonas aeruginosa (CP-CRPA) isolates tested during the first two years of the Antibiotic Resistance Laboratory Network (AR Lab Network). Methods State and local public health laboratories tested CRE and CRPA isolates for organism identification, antimicrobial susceptibility, and PCR-based detection of bla KPC, bla NDM, bla OXA-48-like, bla VIM, and bla IMP carbapenemase genes. All testing results were sent to CDC at least monthly. Results Since January 2017, the AR Lab Network tested 21,733 CRE and 14,141 CRPA. CP-CRE were detected in 37% of CRE; 2% of CRPA were CP-CRPA. Among CP-CRE, 9% (686/8016) were MBL-producers (NDM, VIM, or IMP). Among MBL-producers, a bla NDM gene was detected most often (81%; 551/686). bla NDM were most common among Klebsiella spp. (47%; 261/551), bla IMP were most common among Providencia spp. (53%; 40/75), bla VIM was most common among Enterobacter spp. (19%; 25/62). Twelve percent (96) of MBL CP-CRE contained more than one carbapenemase gene. Among CP-CRPA, 73% (218/300) were MBL producers and bla VIM was the most common gene (62%; 186). Three (1%) MBL CP-CRPA contained more than one carbapenemase. Conclusion Increased testing of CRE and CRPA isolates through the AR Lab Network has facilitated early and rapid detection of hard-to-treat infections caused by MBL-producing organisms across the United States. The widespread distribution of MBL genes highlights the continued need for containment strategies that help prevent transmission between patients and among healthcare facilities. To support therapeutic decisions for severe infections caused by MBL-producing organisms, the AR Lab Network is now offering rapid susceptibility testing against aztreonam/avibactam, using digital dispenser technology. This testing program aims to close the gap between the availability of new drugs or drug combinations and the availability of commercial AST methods, thereby improving patient safety and antimicrobial stewardship. Disclosures All authors: No reported disclosures. [ABSTRACT FROM AUTHOR]