The changing epidemiology of resistance

Abstract

Antibiotic resistance is now a linked global problem. Dispersion of successful clones of multidrug resistant (MDR) bacteria is common, often via the movement of people. Local evolution of MDR bacteria is also important under the pressure of excessive antibiotic use, with horizontal gene transfer providing the means by which genes such as bla(CTX-M) spread amongst different bacterial species and strains. Beta-lactamase production is a common resistance mechanism in Gram-negative bacteria, and the rapid dissemination of novel genes reflects their evolution under the selective pressure of antibiotic usage. Many Enterobacteriaceae now carry broad-spectrum beta-lactamases such as CTX-M, with particular genotypes associated with different geographical regions. The spread of these enzymes has compromised the clinical utility of a number of beta-lactam classes and with the spread of genes such as bla(KPC), carbapenems may be increasingly compromised in the future. High-level fluoroquinolone resistance (mainly caused by gyrA mutations) has also been shown to be associated with CTX-M and CMY-type enzymes, commonly due to co-carriage on conjugative plasmids of the gene for the aminoglycoside-inactivating enzyme AAC-6(1)-Ib-cr and qnr genes (which confer low-level resistance), allowing the easy selection of gyrA mutants in the host strain. Resistance in Gram-positive bacteria is also widely distributed and increasing, with the emergence of community-associated methicillin-resistant Staphylococcus aureus (MRSA) blurring the distinction between hospital and community strains. Antibiotic use and environmental factors all have a role in the emergence and spread of resistance. This article reviews some of the new mechanisms and recent trends in the global spread of MDR bacteria.

Burden of Bloodstream Infection Caused by Extended-Spectrum β-Lactamase–Producing Enterobacteriaceae Determined Using Multistate Modeling at a Swiss University Hospital and a Nationwide Predictive Model

“…1,2 ESBLs threaten the utility of commonly used empiric antibiotic therapy and have been associated with both delayed initiation of appropriate antibiotic therapy and excess mortality. [3][4][5][6] It is important to gain an accurate appreciation of the economic burden of ESBLproducing bacteria to justify the prioritization of infection control and antibiotic stewardship interventions required to confront this problem.…”

Epidemiología de las infecciones bacterianas en pacientes con cirrosis hepática. Expericencia de un centro terciario español

“…Es importante saber que estos microorganismos se encuentran en el ámbito hospitalario y que su aislamiento en la población general es cada vez más frecuente (13,14).…”

The emerging problem of bacterial resistance in cancer patients; proceedings of a workshop held by MASCC “Neutropenia, Infection and Myelosuppression” Study Group during the MASCC annual meeting held in Berlin on 27–29 June 2013

“…Metallo-β-lactamases (NDM, VIM, IMP, OXA) are another group of plasmid-mediated carbapenemases that have emerged in K. pneumoniae and E. coli. P. aeruginosa-and Acinetobacter spp.-containing carbapenemases are often multidrug resistant [33]. Alarmingly, CREs and other carbapenemases can hydrolyze all penicillins, cephalosporins, and aztreonam, as well as the carbapenems.…”