Abstract
Antibiotic resistance in bacteria still remains one of the leading concerns in global public health. Horizontal transfer of resistance genes is considered to be a major cause to facilitate the rapid spread of antibiotic resistance in microbes. In recent years, the role of integrons as mobile genetic elements playing a central role in horizontal transfer of antibiotic resistance have been well studied and documented. Nevertheless, up to date, most of the available investigations and studies on integron had focused on class 1 integrons of Gram-negative microorganisms. In the last decade, class 4 integrons (also known as super integrons) has been considered a major concern in antimicrobial resistance, as well as, a significant factor in bacterial genome evolution; however, most reports had been limited to Vibrio. Thus, this review is aimed at summarizing the occurrence and prevalence of integrons in bacterial isolates, with the focus on class 1 integron within Gram-positive bacteria, class 2 and 3 integrons. Key words: Antibiotic resistance, mobile genetic element, Class 1 integron, Class 2 integron, Class 3 integron, Gram-positive bacteria.
Highlights
Antibiotics are substances that kill or inhibit the growth of microorganisms
The indiscriminate use of existing antibiotics leads to the emergency of antibiotic resistance and poses a dilemma for the future treatment of bacterial infection, with an increasing number of clinical failures in bacterial mediated
Class 1 integron is defective for self-transposition, the transposons and conjugative plasmids associated can serve as vehicles for the intra- and interspecies transmission of genetic material (Rowe-Magnus and Mazel, 2001)
Summary
Antibiotics are substances that kill or inhibit the growth of microorganisms. Regarded as one of the greatest contributions to medicine and humanity in the 20th century, antibiotics had been used to treat a wide range of infectious diseases caused by bacteria, for both animals and humans. The attC sites are generally associated with a single ORF in a structure termed gene cassettes, which are not necessarily observed in integrons, but once integrated they become part of the integron (Fluit and Schmitz, 1999) These smallest known mobile genetic elements can exist in one of two forms, including the independent circular DNA molecule which is unable for stably maintain during cell division, and the linear form which is created by a highly orientation-specific insertion of the free circular element into the integron (Labbate et al, 2009). Class 1 integron is defective for self-transposition, the transposons and conjugative plasmids associated can serve as vehicles for the intra- and interspecies transmission of genetic material (Rowe-Magnus and Mazel, 2001) This site-specific recombination reaction can be mediated by either the Tn21 integrase or the integron integrase IntI1 when the integration sites conform to the consensus sequence GWTMW or GNT (Table 1), respectively (Fluit and Schmitz, 1999).
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