Resistance integrons and super-integrons

Abstract

Integrons are genetic elements composed of a gene encoding an integrase, gene cassettes and an integration site for the gene cassettes (att). The integrase excises and integrates the gene cassettes from and into the integron, but integrons themselves are not mobile. Two groups of integrons are known: resistance integrons and super-integrons. Nearly all known gene cassettes from resistance integrons encode resistance to antibiotics or disinfectants. These integrons are found on transposons, plasmids and the bacterial chromosome. Gene cassettes in super-integrons encode a variety of different functions. Super-integrons are located on the bacterial chromosome. More than 100 gene cassettes may be present, in contrast to resistance integrons where less than ten cassettes are present. Many species harbour super-integrons, which are species-specific, whereas particular resistance integrons can be found in a variety of species. The gene cassettes in resistance integrons probably originated from super-integrons. In the last few years, a variety of new gene cassettes have been described. Many of these encode resistance against newer antibiotics such as cephalosporins and carbapenems. Resistance integrons have been found in isolates from a wide variety of sources, including food.

Screening of Class 1 and Class 2 Integrons in Clinical Isolates of Pseudomonas aeruginosa Collected from Seven Hospitals in Turkey: A Multicenter Study

“…The most frequent resistance gene found in our isolates was from the aadA family, aacA family followed by bla OXA . OXA β-lactamase family has been found in bacterial isolates from some European countries and Turkey [15]. According to obtained results, aadA1, aac(3)-Id-orf-aac(3")-Ia, aac(3)-Ie -bla oxa10 -aadA1, aadA6, aac(6')-I-orf-aadA2 genes or gene cassette arrays are seen common in clinical P. aeruginosa isolates in Turkey.…”

“…Five classes of multi-resistance integrons are known [15]. Class 1 and class 2 integrons are the most frequent ones in Gram-negative bacteria [16,17].…”

Wastewater reuse in irrigation: A microbiological perspective on implications in soil fertility and human and environmental health

“…The time elapsed between the emergence of a new resistance gene in clinical settings and its detection in municipal wastewater is frighteningly short (Szczepanowski et al, 2009). For instance, bacteria resistant to last resort antibiotics mainly or exclusively used in hospitals, such as carbapenems resistant Gram-negative bacteria, vancomycin resistant entereococci (VRE), or methicillin resistant Staphylococcus aureus (MRSA) are nowadays detected in municipal wastewater worldwide (Manaia et al, 2012;Rizzo et al, 2013;Baker-Austin et al, 2006;Fluit and Schmitz, 2004;Hernández et al, 1998;Miyahara et al, 2011). The wide contamination of the environment and the food chain with these genetic determinants may represent a public health calamity.…”

High prevalence of trimethoprim-resistance cassettes in class 1 and 2 integrons in Senegalese Shigella spp isolates

“…Integrons have a well-established role in the dissemination of resistance among Gram-negative pathogens and are thus a useful marker of antibiotic resistance [12]. Trimethoprim is widely used to treat several infectious diseases in Senegal, in combination with sulfonamides.…”