The capsule biosynthesis locus of Haemophilus influenzae shows conspicuous similarity to the corresponding locus in Haemophilus sputorum and may have been recruited from this species by horizontal gene transfer

ABSTRACT Haemophilus influenzae colonizes the respiratory tract in humans and causes both invasive and noninvasive infections. Resistance to extended-spectrum cephalosporins in H. influenzae is rare in Europe. In this study, we defined acquired resistance gene loci and ftsI mutations in multidrug-resistant (MDR) and/or PBP3-mediated beta-lactam-resistant (rPBP3) H. influenzae strains, intending to understand the mode of spread of antibiotic resistance determinants in this species. Horizontal transfer of mobile genetic elements and transformation with resistance-conferring ftsI alleles were contributory. We found one small plasmid and three novel integrative conjugative elements (ICEs) which carry different combinations of resistance genes. Demonstration of transfer and/or ICE circular forms showed that the ICEs are functional. Two extensively MDR genetically unrelated H. influenzae strains (F and G) from the same geographical region shared an identical novel MDR ICE (Tn6686) harboring blaTEM-1, catA2-like, and tet(B). The first Nordic case of MDR H. influenzae septicemia, strain 0, originating from the same geographical area as these strains, had a similar resistance pattern but contained another ICE [Tn6687 with blaTEM-1, catP and tet(B)] with an overall structure quite similar to that of Tn6686. Comparison of the complete ftsI genes among rPBP3 strains revealed that the entire gene or certain regions of it are identical in genetically unrelated strains, indicating horizontal gene transfer. Our findings illustrate that H. influenzae is capable of acquiring resistance against a wide range of commonly used antibiotics through horizontal gene transfer, in terms of conjugative transfer of ICEs and transformation of chromosomal genes. IMPORTANCE Haemophilus influenzae colonizes the respiratory tract in humans and causes both invasive and noninvasive infections. As a threat to treatment, resistance against critically important antibiotics is on the rise in H. influenzae. Identifying mechanisms for horizontal acquisition of resistance genes is important to understand how multidrug resistance develops. The present study explores the antimicrobial resistance genes and their context in beta-lactam-resistant H. influenzae with coresistance to up to four non-beta-lactam groups. The results reveal that this organism is capable of acquiring resistance to a wide range of commonly used antibiotics through conjugative transfer of mobile genetic elements and transformation of chromosomal genes, resulting in mosaic genes with a broader resistance spectrum. Strains with chromosomally mediated resistance to extended-spectrum cephalosporins, co-trimoxazole, and quinolones combined with mobile genetic elements carrying genes mediating resistance to ampicillin, tetracyclines, and chloramphenicol have been reported, and further dissemination of such strains represents a particular concern.

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Horizontal Gene Transfer of ftsI, Encoding Penicillin-Binding Protein 3, in Haemophilus influenzae

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.01545-06 ◽

2007 ◽

Vol 51 (5) ◽

pp. 1589-1595 ◽

Cited By ~ 36

Author(s):

Sho Takahata ◽

Takashi Ida ◽

Nami Senju ◽

Yumiko Sanbongi ◽

Aiko Miyata ◽

...

Keyword(s):

Gene Transfer ◽

Horizontal Gene Transfer ◽

Haemophilus Influenzae ◽

Binding Protein ◽

Resistant Mutant ◽

Penicillin Binding Protein ◽

Genetic Transfer ◽

Complete Sequences

ABSTRACT Horizontal gene transfer has been identified in only a small number of genes in Haemophilus influenzae, an organism which is naturally competent for transformation. This report provides evidence for the genetic transfer of the ftsI gene, which encodes penicillin-binding protein 3, in H. influenzae. Mosaic structures of the ftsI gene were found in several clinical isolates of H. influenzae. To identify the origin of the mosaic sequence, complete sequences of the corresponding gene from seven type strains of Haemophilus species were determined. Comparison of these sequences with mosaic regions identified a homologous recombination of the ftsI gene between H. influenzae and Haemophilus haemolyticus. Subsequently, ampicillin-resistant H. influenzae strains harboring identical ftsI sequences were genotyped by pulsed-field gel electrophoresis (PFGE). Divergent PFGE patterns among β-lactamase-nonproducing ampicillin-resistant (BLNAR) strains from different hospitals indicated the potential for the genetic transfer of the mutated ftsI gene between these isolates. Moreover, transfer of the ftsI gene from BLNAR strains to β-lactamase-nonproducing ampicillin-susceptible (BLNAS) H. influenzae strains was evaluated in vitro. Coincubation of a BLNAS strain (a rifampin-resistant mutant of strain Rd) and BLNAR strains resulted in the emergence of rifampin- and cefdinir-resistant clones at frequencies of 5.1 × 10−7 to 1.5 × 10−6. Characterization of these doubly resistant mutants by DNA sequencing of the ftsI gene, susceptibility testing, and genotyping by PFGE revealed that the ftsI genes of BLNAR strains had transferred to BLNAS strains during coincubation. In conclusion, horizontal transfer of the ftsI gene in H. influenzae can occur in an intraspecies and an interspecies manner.

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A competence-regulated toxin-antitoxin system inHaemophilus influenzae

10.1101/633164 ◽

2019 ◽

Author(s):

Hailey Findlay Black ◽

Scott Mastromatteo ◽

Sunita Sinha ◽

Rachel L. Ehrlich ◽

Corey Nislow ◽

...

Keyword(s):

Gene Transfer ◽

Horizontal Gene Transfer ◽

Haemophilus Influenzae ◽

Gene Pair ◽

Carbon Sources ◽

Toxin Gene ◽

Dna Uptake ◽

Rna Seq ◽

Putative Toxin ◽

Species Deletion

ABSTRACTNatural competence allows bacteria to respond to environmental and nutritional cues by taking up free DNA from their surroundings, thus gaining both nutrients and genetic information. In the Gram-negative bacteriumHaemophilus influenzae, the genes needed for DNA uptake are induced by the CRP andSxytranscription factors in response to lack of preferred carbon sources and nucleotide precursors. Here we show that one of these genes,HI0659, encodes the antitoxin of a competence-regulated toxin-antitoxin operon (‘toxTA’), likely acquired by horizontal gene transfer from aStreptococcusspecies. Deletion of the putative toxin(HI0660)restores uptake to the antitoxin mutant. The fulltoxTAoperon was present in only 17 of the 181 strains we examined; complete deletion was seen in 22 strains and deletions removing parts of the toxin gene in 142 others. In addition to the expected Sxy-and CRP-dependent-competence promoter,HI0659/660transcript analysis using RNA-seq identified an internal antitoxin-repressed promoter whose transcription starts withintoxTand will yield nonfunctional protein. We propose that the most likely effect of unopposed toxin expression is non-specific cleavage of mRNAs and arrest or death of competent cells in the culture. Although the high frequency oftoxTandtoxTAdeletions suggests that this competence-regulated toxin-antitoxin system may be mildly deleterious, it could also facilitate downregulation of protein synthesis and recycling of nucleotides under starvation conditions. Although our analyses were focused on the effects oftoxTA, the RNA-seq dataset will be a useful resource for further investigations into competence regulation.ABBREVIATED SUMMARYThe competence regulon ofHaemophilus influenzaeincludes an unprecedented toxin/antitoxin gene pair. When not opposed by antitoxin, the toxin completely prevents DNA uptake but causes only very minor decreases in cell growth and competence gene expression. The TA gene pair was acquired by horizontal gene transfer, and the toxin gene has undergone repeated deletions in other strains.

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