Dataset Information

Extreme diversity and multiple SCCmec elements in coagulase-negative Staphylococcus found in the Clinic and Community in Beijing, China.

ABSTRACT:

Background

Coagulase-negative staphylococci (CoNS) are recognized as a large reservoir of staphylococcal cassette chromosome mec (SCCmec) harboured by Staphylococcus aureus. However, data of SCCmec in CoNS are relatively absent particularly in China.

Methods

Seventy-eight CoNS clinical and 47 community isolates were collected in Beijing. PCR was performed to classify SCCmec types. Under oxacillin treatment, quantitative real-time reverse transcription PCR (qRT-PCR) was performed to compare mecA mRNA levels and mRNA half-life between isolates with single SCCmec element and those with multiple one. Their growth curves were analysed. Their bacterial cell wall integrity was also compared by performing a Gram stain. All ccr complex segments were sequenced and obtained ccr segments were analysed by phylogenetic analyses.

Results

All 78 clinical isolates had mecA segments compared with 38% in community isolates (total 47). Only 29% clinical isolates and 33% community isolates (among mecA positive isolates) harboured a single previously identified SCCmec type; notably, 17% clinical isolates and 28% community isolates had multiple SCCmec types. Further studies indicated that isolates with multiple SCCmec elements had more stable mecA mRNA expression compared with isolates with single SCCmec elements. CoNS with multiple SCCmec elements demonstrated superior cell wall integrity. Interestingly, phylogenetic analyses of obtained 70 ccr segments indicated that horizontal gene transfer of the ccr complex might exist among various species of clinical CoNS, community CoNS and S. aureus.

Conclusions

CoNS recovered from patients carried extremely diverse but distinctive SCCmec elements compared with isolates from the community. More attention should be given to CoNS with multiple SCCmec not only because they had superior cell wall integrity, but also because CoNS and S. aureus might acquire multiple SCCmec through the ccr complex.

SUBMITTER: Chen XP

PROVIDER: S-EPMC5568392 | biostudies-literature | 2017 Aug

REPOSITORIES: biostudies-literature

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Publications

Extreme diversity and multiple SCCmec elements in coagulase-negative Staphylococcus found in the Clinic and Community in Beijing, China.

Chen Xiao-Ping XP Li Wen-Ge WG Zheng Hao H Du Hai-Yan HY Zhang Li L Zhang Lei L Che Jie J Wu Yuan Y Liu Shu-Mei SM Lu Jin-Xing JX

Annals of clinical microbiology and antimicrobials 20170822 1

<h4>Background</h4>Coagulase-negative staphylococci (CoNS) are recognized as a large reservoir of staphylococcal cassette chromosome mec (SCCmec) harboured by Staphylococcus aureus. However, data of SCCmec in CoNS are relatively absent particularly in China.<h4>Methods</h4>Seventy-eight CoNS clinical and 47 community isolates were collected in Beijing. PCR was performed to classify SCCmec types. Under oxacillin treatment, quantitative real-time reverse transcription PCR (qRT-PCR) was performed t ...[more]

PMID: 28830554

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Project description:SCCmec elements are very important mobile genetic elements in Staphylococci that carry beta-lactam resistance genes mecA/mecC, recombinase genes and a variety of accessory genes. Twelve main types and a couple of variants have yet been described. In addition, there are also other SCC elements harbouring other markers. In order to subtype strains of methicillin-resistant S. aureus (MRSA) based on variations within their SCCmec elements, 86 markers were selected from published SCC sequences for an assay based on multiplexed primer extension reactions followed by hybridisation to the specific probes. These included mecA/mecC, fusC, regulatory genes, recombinase genes, genes from ACME and heavy metal resistance loci as well as several genes of unknown function. Hybridisation patterns for published genome or SCC sequences were theoretically predicted. For validation of the microarray based assay and for stringent hybridisation protocol optimization, real hybridization experiments with fully sequenced reference strains were performed modifying protocols until yielded the results were in concordance to the theoretical predictions. Subsequently, 226 clinical isolates from two hospitals in the city of Dresden, Germany, were characterised in detail. Beside previously described types and subtypes, a wide variety of additional SCC types or subtypes and pseudoSCC elements were observed as well as numerous composite elements. Within the study collection, 61 different such elements have been identified. Since hybridisation cannot recognise the localisation of target genes, gene duplications or inversions, this is a rather conservative estimate. Interestingly, some widespread epidemic strains engulf distinct variants with different SCCmec subtypes. Notable examples are ST239-MRSA-III, CC5-, CC22-, CC30-, and CC45-MRSA-IV or CC398-MRSA-V. Conversely, identical SCC elements were observed in different strains with SCCmec IVa being spread among the highest number of Clonal Complexes. The proposed microarray can help to distinguish isolates that appear similar or identical by other typing methods and it can be used as high-throughput screening tool for the detection of putative new SCC types or variants that warrant further investigation and sequencing. The high degree of diversity of SCC elements even within so-called strains could be helpful for epidemiological typing. It also raises the question on scale and speed of the evolution of SCC elements.

Project description:RationaleAlthough frequently retrieved in tracheal secretions of critically ill patients on mechanical ventilation, the existence of pneumonia caused by coagulase-negative staphylococci (CoNS) remains controversial.ObjectiveTo assess whether Staphylococcus haemolyticus (S. haemolyticus) inoculated in mice's trachea can infect normal lung parenchyma, increasing concentrations of S. haemolyticus were intratracheally administered in 221 immunocompetent mice.MethodsEach animal received intratracheally phosphate-buffered saline (PBS) (n = 43) or live (n = 141) or inactivated (n = 37) S. haemolyticus at increasing load: 1.0 × 106, 1.0 × 107, and 1.0 × 108 colony forming units (CFU). Forty-three animals were sacrificed at 12 h and 178 were sacrificed at 36 h; 64 served for post-mortem lung histology, 157 served for pre-mortem bronchoalveolar lavage (BAL) analysis, and 42 served for post-mortem quantitative bacteriology of lung tissue. The distribution of biofilm-associated genes was investigated in the S. haemolyticus strain used in our in vivo experiment as well as among 19 other clinical S. haemolyticus strains collected from hospitals or nursing houses.Measurements and main resultsIntratracheal inoculation of 1.0 × 108 CFU live S. haemolyticus caused macroscopic and histological confluent pneumonia with significant increase in BAL white cell count, tumor necrosis factor-α (TNF-α), and macrophage inflammatory protein (MIP)-2. At 12 h, high concentrations of S. haemolyticus were identified in BAL. At 36 h, lung injury and BAL inflammation were less severe than at 12 h and moderate concentrations of species belonging to the oropharyngeal flora were identified in lung tissue. The inoculation of 1.0 × 106 and 1.0 × 107 CFU live S. haemolyticus caused histologic interstitial pneumonia and moderate BAL inflammation. Similar results were observed after inoculation of inactivated S. haemolyticus. Moreover, biofilm formation was a common phenotype in S. haemolyticus isolates. The low prevalence of the ica operon in our clinical S. haemolyticus strain collection indicated icaA and icaD independent-biofilm formation.ConclusionIn immunocompetent spontaneously breathing mice, inoculation of S. haemolyticus causes concentration-dependent lung infection that spontaneously recovers over time. icaA and icaD independent biofilm formation is a common phenotype in S. haemolyticus isolates.

Dataset Information

Extreme diversity and multiple SCCmec elements in coagulase-negative Staphylococcus found in the Clinic and Community in Beijing, China.

Background

Methods

Results

Conclusions

Publications

Extreme diversity and multiple SCCmec elements in coagulase-negative Staphylococcus found in the Clinic and Community in Beijing, China.

Similar Datasets

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