Tn 5253 Family Integrative and Conjugative Elements Carrying mef (I) and catQ Determinants in Streptococcus pneumoniae and Streptococcus pyogenes

Abstract

The linkage between the macrolide efflux gene mef(I) and the chloramphenicol inactivation gene catQ was first described in Streptococcus pneumoniae (strain Spn529), where the two genes are located in a module designated IQ element. Subsequently, two different defective IQ elements were detected in Streptococcus pyogenes (strains Spy029 and Spy005). The genetic elements carrying the three IQ elements were characterized, and all were found to be Tn5253 family integrative and conjugative elements (ICEs). The ICE from S. pneumoniae (ICESpn529IQ) was sequenced, whereas the ICEs from S. pyogenes (ICESpy029IQ and ICESpy005IQ, the first Tn5253-like ICEs reported in this species) were characterized by PCR mapping, partial sequencing, and restriction analysis. ICESpn529IQ and ICESpy029IQ were found to share the int Sp23FST81 integrase gene and an identical Tn916 fragment, whereas ICESpy005IQ has int 5252 and lacks Tn916. All three ICEs were found to lack the linearized pC194 plasmid that is usually associated with Tn5253-like ICEs, and all displayed a single copy of a toxin-antitoxin operon that is typically contained in the direct repeats flanking the excisable pC194 region when this region is present. Two different insertion sites of the IQ elements were detected, one in ICESpn529IQ and ICESpy029IQ, and another in ICESpy005IQ. The chromosomal integration of the three ICEs was site specific, depending on the integrase (int Sp23FST81 or int 5252 ). Only ICESpy005IQ was excised in circular form and transferred by conjugation. By transformation, mef(I) and catQ were cotransferred at a high frequency from S. pyogenes Spy005 and at very low frequencies from S. pneumoniae Spn529 and S. pyogenes Spy029.

Resistance Genes and Genetic Elements Associated with Antibiotic Resistance in Clinical and Commensal Isolates of Streptococcus salivarius

“…ICESpn529IQ and ICESpy029IQ also carry a Tn916 fragment with a silent tet(M) gene. Only ICESpy005IQ was found to excise itself and transfer by conjugation (35). No ICE was detected in the vicinity of the mef(E) and catQ genes in the genome of the commensal strain F4-20 that was analyzed, ruling out acquisition of this genetic element by conjugation.…”

“…This is the first description of this variant and the first description of an IQ-like element in S. salivarius. In S. pneumoniae and S. pyogenes, the IQ element is carried by larger genetic elements that harbor a conjugative module of the ICE Tn5252 family and either a recombination module similar to that of ICESp23FST81 (integration in the rplL gene for ICESpn529IQ and ICESpy029IQ) or the recombination module of Tn5252 (for ICESpy005IQ) (35). ICESpn529IQ and ICESpy029IQ also carry a Tn916 fragment with a silent tet(M) gene.…”

“…PCR was then carried out to search for antibiotic resistance genes and MGE in these strains. For MGE, the focus was on elements described in other streptococci: Tn916 [and variants carrying the erm(B) and mef(A/E) resistance genes] (27,28), ICESt3 (33,34), the macrolide efflux genetic assembly (MEGA) element (28), and the IQ element (15,35). In addition, some elements were tested by PCR for excision in order to evaluate their functionality.…”

Molecular mechanisms and epidemiology of resistance in Streptococcus pneumoniae in the Middle East region

“…Moreover, mefI was found to be located on the right-hand side of a newly characterized nonmobile composite structure, the 5216IQ complex, adjacent to the msr and catQ genes [41]. Recently, it was proved that this IQ element is actually inserted within a larger genetic element, conjugative transposon Tn5253, an integrative conjugative element [42].…”

“…A second cat gene, catQ, was reported for the first time in pneumococcal strains [41] and was later found to also be located on Tn5253. However, the strain harbouring Tn5253 with a catQ gene lacked the presence of pC194 , which is usually used as a cargo gene for Tn5253 [42]. catQ is an A-type cat gene with more than 90 % DNA similarity to the first catQ originally described in Clostridium perfringens [88].…”