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Composite mobile genetic elements disseminating macrolide resistance in Streptococcus pneumoniae.

Chancey ST, Agrawal S, Schroeder MR, Farley MM, Tettelin H, Stephens DS - Front Microbiol (2015)

Bottom Line: The results reported here include identification of novel insertion sites for Mega and characterization of the insertion sites of Tn916-like elements in the pneumococcal chromosome and in larger composite elements.The data indicate that integration of elements by conjugation was infrequent compared to recombination.Thus, it appears that conjugative mobile elements allow the pneumococcus to acquire DNA from distantly related bacteria, but once integrated into a pneumococcal genome, transformation and recombination is the primary mechanism for transmission of novel DNA throughout the pneumococcal population.

View Article: PubMed Central - PubMed

Affiliation: Division of Infectious Diseases, Department of Medicine, Emory University School of Medicine Atlanta, GA, USA ; Laboratories of Microbial Pathogenesis, Department of Veterans Affairs Medical Center Atlanta, GA, USA.

ABSTRACT
Macrolide resistance in Streptococcus pneumoniae emerged in the U.S. and globally during the early 1990's. The RNA methylase encoded by erm(B) and the macrolide efflux genes mef(E) and mel were identified as the resistance determining factors. These genes are disseminated in the pneumococcus on mobile, often chimeric elements consisting of multiple smaller elements. To better understand the variety of elements encoding macrolide resistance and how they have evolved in the pre- and post-conjugate vaccine eras, the genomes of 121 invasive and ten carriage isolates from Atlanta from 1994 to 2011 were analyzed for mobile elements involved in the dissemination of macrolide resistance. The isolates were selected to provide broad coverage of the genetic variability of antibiotic resistant pneumococci and included 100 invasive isolates resistant to macrolides. Tn916-like elements carrying mef(E) and mel on the Macrolide Genetic Assembly (Mega) and erm(B) on the erm(B) element and Tn917 were integrated into the pneumococcal chromosome backbone and into larger Tn5253-like composite elements. The results reported here include identification of novel insertion sites for Mega and characterization of the insertion sites of Tn916-like elements in the pneumococcal chromosome and in larger composite elements. The data indicate that integration of elements by conjugation was infrequent compared to recombination. Thus, it appears that conjugative mobile elements allow the pneumococcus to acquire DNA from distantly related bacteria, but once integrated into a pneumococcal genome, transformation and recombination is the primary mechanism for transmission of novel DNA throughout the pneumococcal population.

No MeSH data available.


Related in: MedlinePlus

Comparison of ICESp23FST81-like elements encoding macrolide resistance. The location of the Tn916-like element in each is indicated by the Tn5253 genes shown as arrows above each track. Green arrows, Tn916-genes; Blue arrows, mef(E) and mel; yellow arrows, tet(M); pink arrows, integrated plasmid pC194; red arrows, cat.
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Figure 6: Comparison of ICESp23FST81-like elements encoding macrolide resistance. The location of the Tn916-like element in each is indicated by the Tn5253 genes shown as arrows above each track. Green arrows, Tn916-genes; Blue arrows, mef(E) and mel; yellow arrows, tet(M); pink arrows, integrated plasmid pC194; red arrows, cat.

Mentions: The five ICESp23FST81-like elements contained Tn916-like insertions, including a Tn916-like, a Tn3872-like and four Tn2009-like elements (Table 3). Each of the smaller elements was integrated between orf9 and orf8 of Tn5253 and contained identical flanking and coupling sequences, indicating that each was derived from a single conjugation event and subsequent transfer of Mega-1 between Tn916 and Tn2009 (Figure 6). GA44378 containing Tn916 integrated into the ICESp23FST81-like element was macrolide resistant due to an unlinked Mega-1.III insertion (Table 3; Table S2). ICESp23FST81 was originally described in a 23F, ST81 isolate (Croucher et al., 2009). Five of six ICESp23FST81 family elements were also in CC81, however only two were serotype 23F (Table 3). The others were serotype 19A (n = 1) and 19F (n = 2) and represent capsule switching from a PCV7 vaccine serotype to a non-vaccine serotype and a different vaccine serotype, respectively. This conclusion is supported by the close relationship between the isolates, all but one of which was also serotype 23F and CC81 (Figure 6). The lone exception was GA13494, a serotype 14, CC156 isolate that contained Tn2009, indicating horizontal transfer of the composite element between the clones (Figure 6). These were isolated over a 9-year period spanning the pre-PCV7 and post-PCV7 eras (1995–2004). This demonstrated clonal expansion and the long-term stability of the clone and the Tn5253-like element harboring Tn2009.


Composite mobile genetic elements disseminating macrolide resistance in Streptococcus pneumoniae.

Chancey ST, Agrawal S, Schroeder MR, Farley MM, Tettelin H, Stephens DS - Front Microbiol (2015)

Comparison of ICESp23FST81-like elements encoding macrolide resistance. The location of the Tn916-like element in each is indicated by the Tn5253 genes shown as arrows above each track. Green arrows, Tn916-genes; Blue arrows, mef(E) and mel; yellow arrows, tet(M); pink arrows, integrated plasmid pC194; red arrows, cat.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4321634&req=5

Figure 6: Comparison of ICESp23FST81-like elements encoding macrolide resistance. The location of the Tn916-like element in each is indicated by the Tn5253 genes shown as arrows above each track. Green arrows, Tn916-genes; Blue arrows, mef(E) and mel; yellow arrows, tet(M); pink arrows, integrated plasmid pC194; red arrows, cat.
Mentions: The five ICESp23FST81-like elements contained Tn916-like insertions, including a Tn916-like, a Tn3872-like and four Tn2009-like elements (Table 3). Each of the smaller elements was integrated between orf9 and orf8 of Tn5253 and contained identical flanking and coupling sequences, indicating that each was derived from a single conjugation event and subsequent transfer of Mega-1 between Tn916 and Tn2009 (Figure 6). GA44378 containing Tn916 integrated into the ICESp23FST81-like element was macrolide resistant due to an unlinked Mega-1.III insertion (Table 3; Table S2). ICESp23FST81 was originally described in a 23F, ST81 isolate (Croucher et al., 2009). Five of six ICESp23FST81 family elements were also in CC81, however only two were serotype 23F (Table 3). The others were serotype 19A (n = 1) and 19F (n = 2) and represent capsule switching from a PCV7 vaccine serotype to a non-vaccine serotype and a different vaccine serotype, respectively. This conclusion is supported by the close relationship between the isolates, all but one of which was also serotype 23F and CC81 (Figure 6). The lone exception was GA13494, a serotype 14, CC156 isolate that contained Tn2009, indicating horizontal transfer of the composite element between the clones (Figure 6). These were isolated over a 9-year period spanning the pre-PCV7 and post-PCV7 eras (1995–2004). This demonstrated clonal expansion and the long-term stability of the clone and the Tn5253-like element harboring Tn2009.

Bottom Line: The results reported here include identification of novel insertion sites for Mega and characterization of the insertion sites of Tn916-like elements in the pneumococcal chromosome and in larger composite elements.The data indicate that integration of elements by conjugation was infrequent compared to recombination.Thus, it appears that conjugative mobile elements allow the pneumococcus to acquire DNA from distantly related bacteria, but once integrated into a pneumococcal genome, transformation and recombination is the primary mechanism for transmission of novel DNA throughout the pneumococcal population.

View Article: PubMed Central - PubMed

Affiliation: Division of Infectious Diseases, Department of Medicine, Emory University School of Medicine Atlanta, GA, USA ; Laboratories of Microbial Pathogenesis, Department of Veterans Affairs Medical Center Atlanta, GA, USA.

ABSTRACT
Macrolide resistance in Streptococcus pneumoniae emerged in the U.S. and globally during the early 1990's. The RNA methylase encoded by erm(B) and the macrolide efflux genes mef(E) and mel were identified as the resistance determining factors. These genes are disseminated in the pneumococcus on mobile, often chimeric elements consisting of multiple smaller elements. To better understand the variety of elements encoding macrolide resistance and how they have evolved in the pre- and post-conjugate vaccine eras, the genomes of 121 invasive and ten carriage isolates from Atlanta from 1994 to 2011 were analyzed for mobile elements involved in the dissemination of macrolide resistance. The isolates were selected to provide broad coverage of the genetic variability of antibiotic resistant pneumococci and included 100 invasive isolates resistant to macrolides. Tn916-like elements carrying mef(E) and mel on the Macrolide Genetic Assembly (Mega) and erm(B) on the erm(B) element and Tn917 were integrated into the pneumococcal chromosome backbone and into larger Tn5253-like composite elements. The results reported here include identification of novel insertion sites for Mega and characterization of the insertion sites of Tn916-like elements in the pneumococcal chromosome and in larger composite elements. The data indicate that integration of elements by conjugation was infrequent compared to recombination. Thus, it appears that conjugative mobile elements allow the pneumococcus to acquire DNA from distantly related bacteria, but once integrated into a pneumococcal genome, transformation and recombination is the primary mechanism for transmission of novel DNA throughout the pneumococcal population.

No MeSH data available.


Related in: MedlinePlus