Molecular characterization of methicillin-resistant and -susceptible Staphylococcus aureus recovered from hospital personnel

Introduction. Methicillin-resistant Staphylococcus aureus (MRSA) is one of the major causes of hospital-acquired infections. Over the past two decades MRSA has become ‘epidemic’ in many hospitals worldwide. However, little is known about the genetic background of S. aureus recovered from hospital personnel in China. Hypothesis/Gap Statement. The diversity of S. aureus genotypes warrants further surveillance and genomic studies to better understand the relatedness of these bacteria to those recovered from patients and the community. Aim. The aim of this study was to determine the genetic diversity of MRSA and methicillin-susceptible S. aureus (MSSA) recovered from hospital personnel in Tianjin, North China. Methodology. Three hundred and sixty-eight hand or nasal swabs were collected from 276 hospital personnel in 4 tertiary hospitals in Tianjin, North China between November 2017 and March 2019. In total, 535 Gram-positive bacteria were isolated, of which 59 were identified as S. aureus . Staphylococcal cassette chromosome mec (SCCmec) typing, multi-locus sequence typing (MLST) and spa typing were performed to determine the molecular characteristics of S. aureus . Results. Thirty-one out of 276 (11 %) hospital personnel were S. aureus carriers, whereas 11/276 (4 %) carried MRSA. Fifty out of 59 (85 %) S. aureus isolates were resistant or intermediately resistant to erythromycin. The dominant genotypes of MRSA recovered from hospital personnel were ST398-t034-SCCmecIV/V and ST630-t084/t2196, whereas the major genotypes of MSSA included ST15-t078/t084/t346/t796/t8862/t8945/t11653 and ST398-t189/t034/t078/t084/t14014. Conclusion. Although the predominant genotypes of MRSA recovered from hospital personnel in this study were different from the main genotypes that have previously been reported to cause infections in Tianjin and in other geographical areas of China, the MRSA ST398-t034 genotype has previously been reported to be associated with livestock globally. The dominant MSSA genotypes recovered from hospital personnel were consistent with the those previously reported to have been recovered from the clinic.

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Busting biofilms: free-living amoebae disrupt preformed methicillin-resistant Staphylococcus aureus (MRSA) and Mycobacterium bovis biofilms

Microbiology ◽

10.1099/mic.0.000933 ◽

2020 ◽

Vol 166 (8) ◽

pp. 695-706 ◽

Cited By ~ 1

Author(s):

Kevin H. Martin ◽

Grace I. Borlee ◽

William H. Wheat ◽

Mary Jackson ◽

Bradley R. Borlee

Keyword(s):

Staphylococcus Aureus ◽

Mycobacterium Bovis ◽

Type Species ◽

Acanthamoeba Castellanii ◽

Methicillin Resistant ◽

Content Type ◽

Host Immune Responses ◽

Link Type ◽

Abiotic Surfaces ◽

Low Concentrations

Biofilm-associated infections are difficult to eradicate because of their ability to tolerate antibiotics and evade host immune responses. Amoebae and/or their secreted products may provide alternative strategies to inhibit and disperse biofilms on biotic and abiotic surfaces. We evaluated the potential of five predatory amoebae – Acanthamoeba castellanii, Acanthamoeba lenticulata, Acanthamoeba polyphaga, Vermamoeba vermiformis and Dictyostelium discoideum – and their cell-free secretions to disrupt biofilms formed by methicillin-resistant Staphylococcus aureus (MRSA) and Mycobacterium bovis . The biofilm biomass produced by MRSA and M. bovis was significantly reduced when co-incubated with A. castellanii, A. lenticulata and A. polyphaga, and their corresponding cell-free supernatants (CFS). Acanthamoeba spp. generally produced CFS that mediated biofilm dispersal rather than directly killing the bacteria; however, A. polyphaga CFS demonstrated active killing of MRSA planktonic cells when the bacteria were present at low concentrations. The active component(s) of the A. polyphaga CFS is resistant to freezing, but can be inactivated to differing degrees by mechanical disruption and exposure to heat. D. discoideum and its CFS also reduced preformed M. bovis biofilms, whereas V. vermiformis only decreased M. bovis biofilm biomass when amoebae were added. These results highlight the potential of using select amoebae species or their CFS to disrupt preformed bacterial biofilms.

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Thermonuclease test accuracy is preserved in methicillin-resistant Staphylococcus aureus isolates

Journal of Medical Microbiology ◽

10.1099/jmm.0.001166 ◽

2020 ◽

Vol 69 (4) ◽

pp. 548-551

Author(s):

Benjamin Canning ◽

Iskandar Mohamed ◽

Nimal Wickramasinghe ◽

Jonathan Swindells ◽

Matthew K. O'Shea

Keyword(s):

Staphylococcus Aureus ◽

Type Species ◽

Final Analysis ◽

Test Accuracy ◽

Coagulase Negative Staphylococci ◽

Methicillin Resistant ◽

Content Type ◽

Microbial Identification ◽

Gene Variation ◽

Link Type

Introduction. The nuc gene encodes a thermonuclease which is present in Staphylococcus aureus but not in coagulase-negative staphylococci (CoNS) and is the target of the rapid phenotypic thermonuclease test. The effect of nuc gene variation in methicillin-resistant S. aureus (MRSA) on the performance of PCR testing has been noted, although there are no reports about the effect of MRSA on the activity of the thermonuclease enzyme. Aim. Our goals were to examine the sensitivity and specificity of the thermonuclease test used to distinguish S. aureus from CoNS cultured from blood. In addition, we aimed to assess differences in the sensitivity, specificity and accuracy of the thermonuclease test between methicillin-sensitive S. aureus (MSSA) and MRSA isolates. Methodology. We performed a retrospective analysis of 1404 isolates. Each isolate from a positive blood culture was identified as a Gram-positive coccus by microscopy then analysed with the thermonuclease test (Southern Group Laboratory) prior to confirmatory identification using VITEK microbial identification platforms (bioMérieux) and cefoxitin disc diffusion testing. Results. Of 1331 samples included in the final analysis, 189 were thermonuclease-positive, of which 176 were identified as S. aureus . Of the 1142 thermonuclease-negative samples, 13 were finally identified as S. aureus , giving a sensitivity of 93.1 % (95 % confidence interval [CI] 88.5–96.3) and specificity of 98.9 % (95 % CI 98.1–99.4). Of the nine proven MRSA samples, eight were thermonuclease-positive, giving a sensitivity of 88.9 % (95 % CI 51.8–99.7). Thermonuclease test accuracy for MSSA and MRSA isolates was 98.1 % (95 % CI 97.2–98.8) versus 98.8 % (95 % CI 98.0–99.3), respectively. Conclusions. In the era of increasing use of molecular-based microbiology assays, the thermonuclease test remains a simple, inexpensive and robust test for the presumptive identification of S. aureus cultured from blood, irrespective of methicillin sensitivity.

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Disinfection of methicillin-resistant Staphylococcus aureus, vancomycin-resistant Enterococcus faecium and Acinetobacter baumannii using Klaran WD array system

Access Microbiology ◽

10.1099/acmi.0.000194 ◽

2021 ◽

Vol 3 (9) ◽

Author(s):

Richard M. Mariita ◽

Rajul V. Randive

Keyword(s):

Staphylococcus Aureus ◽

Acinetobacter Baumannii ◽

Enterococcus Faecium ◽

Type Species ◽

Scientific Evidence ◽

Reduction Factor ◽

Methicillin Resistant ◽

Content Type ◽

Link Type ◽

Vancomycin Resistant

Hospital-associated infections (HAIs) are a major burden in healthcare systems. In this study, UVC LEDs emitting radiation from 260 to 270 nm were evaluated for effectiveness in reducing methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant Enterococcus faecium and Acinetobacter baumannii . The array has four WD LEDs, each with 70 mW placed at 7 cm from test organisms. With 11.76 mJ cm−2, the study obtained 99.99% reduction (log10 reduction factor of 4) against MRSA and VRE. For A. baumannii , 9 mJ cm−2 obtained 99.999% reduction (log10 reduction factor of 5). These results present scientific evidence on how effective UVC LEDs can be used in the fight against HAIs.

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Comparative genomics of ST5 and ST30 methicillin-resistant Staphylococcus aureus sequential isolates recovered from paediatric patients with cystic fibrosis

Microbial Genomics ◽

10.1099/mgen.0.000510 ◽

2021 ◽

Vol 7 (3) ◽

Author(s):

María Sol Haim ◽

Rahat Zaheer ◽

Amrita Bharat ◽

Sabrina Di Gregorio ◽

José Di Conza ◽

...

Keyword(s):

Cystic Fibrosis ◽

Staphylococcus Aureus ◽

Antimicrobial Resistance ◽

Type Species ◽

Methicillin Resistant ◽

Content Type ◽

Airway Infection ◽

Synonymous Mutations ◽

Link Type ◽

Mrsa Strains

Staphylococcus aureus chronic airway infection in patients with cystic fibrosis (CF) allows this pathogen to adapt over time in response to different selection pressures. We have previously shown that the main sequence types related to community-acquired methicillin-resistant S. aureus (MRSA) infections in Argentina – ST5 and ST30 – are also frequently isolated from the sputum of patients with CF, but in these patients they usually display multi-drug antimicrobial resistance. In this study, we sequenced the genomes of MRSA from four paediatric CF patients with the goal of identifying mutations among sequential isolates, especially those possibly related to antimicrobial resistance and virulence, which might contribute to the adaptation of the pathogen in the airways of patients with CF. Our results revealed genetic differences in sequential MRSA strains isolated from patients with CF in both their core and accessory genomes. Although the genetic adaptation of S. aureus was distinct in different hosts, we detected independent mutations in thyA, htrA, rpsJ and gyrA – which are known to have crucial roles in S. aureus virulence and antimicrobial resistance – in isolates recovered from multiple patients. Moreover, we identified allelic variants that were detected in all of the isolates recovered after a certain time point; these non-synonymous mutations were in genes associated with antimicrobial resistance, virulence, iron scavenging and oxidative stress resistance. In conclusion, our results provide evidence of genetic variability among sequential MRSA isolates that could be implicated in the adaptation of these strains during chronic CF airway infection.

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Significant variability exists in the cytotoxicity of global methicillin-resistant Staphylococcus aureus lineages

Microbiology ◽

10.1099/mic.0.001119 ◽

2021 ◽

Vol 167 (12) ◽

Author(s):

Maisem Laabei ◽

Sharon J. Peacock ◽

Beth Blane ◽

Sarah L. Baines ◽

Benjamin P. Howden ◽

...

Keyword(s):

Staphylococcus Aureus ◽

Type Species ◽

Healthcare Setting ◽

Health Concern ◽

Accessory Gene ◽

Methicillin Resistant ◽

Content Type ◽

Link Type ◽

Accessory Gene Regulator ◽

Toxin Regulation

Staphylococcus aureus is a major human pathogen where the emergence of antibiotic resistant lineages, such as methicillin-resistant S. aureus (MRSA), is a major health concern. While some MRSA lineages are restricted to the healthcare setting, the epidemiology of MRSA is changing globally, with the rise of specific lineages causing disease in healthy people in the community. In the past two decades, community-associated MRSA (CA-MRSA) has emerged as a clinically important and virulent pathogen associated with serious skin and soft-tissue infections (SSTI). These infections are primarily cytotoxin driven, leading to the suggestion that hypervirulent lineages/multi-locus sequence types (STs) exist. To examine this, we compared the cytotoxicity of 475 MRSA isolates representing five major MRSA STs (ST22, ST93, ST8, ST239 and ST36) by employing a monocyte-macrophage THP-1 cell line as a surrogate for measuring gross cytotoxicity. We demonstrate that while certain MRSA STs contain highly toxic isolates, there is such variability within lineages to suggest that this aspect of virulence should not be inferred from the genotype of any given isolate. Furthermore, by interrogating the accessory gene regulator (Agr) sequences in this collection we identified several Agr mutations that were associated with reduced cytotoxicity. Interestingly, the majority of isolates that were attenuated in cytotoxin production contained no mutations in the agr locus, indicating a role of other undefined genes in S. aureus toxin regulation.

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Impact of pH on growth of Staphylococcus epidermidis and Staphylococcus aureus in vitro

Journal of Medical Microbiology ◽

10.1099/jmm.0.001421 ◽

2021 ◽

Vol 70 (9) ◽

Author(s):

Vidula Iyer ◽

Janhavi Raut ◽

Anindya Dasgupta

Keyword(s):

Staphylococcus Aureus ◽

Growth Kinetics ◽

Staphylococcus Epidermidis ◽

Type Species ◽

Ph Dependence ◽

Skin Microbiome ◽

Content Type ◽

Link Type ◽

Kinetics Of

The pH of skin is critical for skin health and resilience and plays a key role in controlling the skin microbiome. It has been well reported that under dysbiotic conditions such as atopic dermatitis (AD), eczema, etc. there are significant aberrations of skin pH, along with a higher level of Staphylococcus aureus compared to the commensal Staphylococcus epidermidis on skin. To understand the effect of pH on the relative growth of S. epidermidis and S. aureus , we carried out simple in vitro growth kinetic studies of the individual microbes under varying pH conditions. We demonstrated that the growth kinetics of S. epidermidis is relatively insensitive to pH within the range of 5–7, while S. aureus shows a stronger pH dependence in that range. Gompertz’s model was used to fit the pH dependence of the growth kinetics of the two bacteria and showed that the equilibrium bacterial count of S. aureus was the more sensitive parameter. The switch in growth rate happens at a pH of 6.5–7. Our studies are in line with the general hypothesis that keeping the skin pH within an acidic range is advantageous in terms of keeping the skin microbiome in balance and maintaining healthy skin.

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Fatal exudative dermatitis in island populations of red squirrels (Sciurus vulgaris): spillover of a virulent Staphylococcus aureus clone (ST49) from reservoir hosts

Microbial Genomics ◽

10.1099/mgen.0.000565 ◽

2021 ◽

Vol 7 (5) ◽

Author(s):

Kay Fountain ◽

Tiffany Blackett ◽

Helen Butler ◽

Catherine Carchedi ◽

Anna-Katarina Schilling ◽

...

Keyword(s):

Staphylococcus Aureus ◽

Type Species ◽

Small Ruminants ◽

Sciurus Vulgaris ◽

Red Squirrels ◽

Content Type ◽

Island Populations ◽

Link Type ◽

Bacterial Cell Membrane ◽

Reservoir Hosts

Fatal exudative dermatitis (FED) is a significant cause of death of red squirrels (Sciurus vulgaris) on the island of Jersey in the Channel Islands where it is associated with a virulent clone of Staphylococcus aureus, ST49. S. aureus ST49 has been found in other hosts such as small mammals, pigs and humans, but the dynamics of carriage and disease of this clone, or any other lineage in red squirrels, is currently unknown. We used whole-genome sequencing to characterize 228 isolates from healthy red squirrels on Jersey, the Isle of Arran (Scotland) and Brownsea Island (England), from red squirrels showing signs of FED on Jersey and the Isle of Wight (England) and a small number of isolates from other hosts. S. aureus was frequently carried by red squirrels on the Isle of Arran with strains typically associated with small ruminants predominating. For the Brownsea carriage, S. aureus was less frequent and involved strains associated with birds, small ruminants and humans, while for the Jersey carriage S. aureus was rare but ST49 predominated in diseased squirrels. By combining our data with publicly available sequences, we show that the S. aureus carriage in red squirrels largely reflects frequent but facile acquisitions of strains carried by other hosts sharing their habitat (‘spillover’), possibly including, in the case of ST188, humans. Genome-wide association analysis of the ruminant lineage ST133 revealed variants in a small number of mostly bacterial-cell-membrane-associated genes that were statistically associated with squirrel isolates from the Isle of Arran, raising the possibility of specific adaptation to red squirrels in this lineage. In contrast there is little evidence that ST49 is a common carriage isolate of red squirrels and infection from reservoir hosts such as bank voles or rats, is likely to be driving the emergence of FED in red squirrels.

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Detection and partial characterization of extracellular inducers of persistence in Staphylococcus epidermidis and Staphylococcus aureus

Journal of Medical Microbiology ◽

10.1099/jmm.0.001392 ◽

2021 ◽

Vol 70 (6) ◽

Author(s):

Elyse C. Curry ◽

Ryan G. Hart ◽

Danni Y. Habtu ◽

Neal R. Chamberlain

Keyword(s):

Molecular Weight ◽

Staphylococcus Aureus ◽

Staphylococcus Epidermidis ◽

Type Species ◽

Proteinase K ◽

Partial Characterization ◽

Content Type ◽

Link Type ◽

Inducing Factors

Introduction. This study describes the identification and partial characterization of persistence-inducing factors (PIFs) from staphylococci. Hypothesis/Gap Statement. Increases in persisters during mid-log phase growth indicate that quorum-sensing factors might be produced by staphylococci. Aim. To identify and partially characterize PIFs from Staphylococcus epidermidis RP62A and Staphylococcus aureus SH1000. Methodology. Others have demonstrated a significant increase in persister numbers during mid-log phase. Inducers of this mid-log increase have yet to be identified in staphylococci. Optical density at 600 nm (OD600) was used instead of time to determine when persister numbers increased during logarithmic growth. Concentrated culture filtrates (CCFs) from S. epidermidis and S. aureus were obtained at various OD600s and following incubation at 16 h. The CCFs were used to develop a PIF assay. The PIF assay was used to partially characterize PIF from S. epidermidis and S. aureus for sizing of PIF activity, temperature and protease sensitivity and inter-species communications. Results. The optimal OD600s for S. epidermidis and S. aureus PIF assays were 2.0 and 0.5, respectively. The highest PIF activity for both species was from CCF following incubation overnight (16 h). S. epidermidis ’ PIF activity was decreased by storage at 4 oC but not at 20 oC (16 h), 37 oC (1 h) or 100 oC (15 min). S. aureus ’ PIF activity was decreased following storage at 4 oC (2 weeks) and after boiling at 100 oC for 5 min but not after incubation at 37 oC (1 h). PIF activity from both species went through a 3000 molecular weight cutoff ultrafilter. Proteinase K treatment of S. aureus PIF decreased activity but did not decrease the PIF activity of S. epidermidis . PIF from S. epidermidis did not increase persisters when used to treat S. aureus cells and nor did PIF from S. aureus increase persisters when used to treat S. epidermidis cells. Conclusions. Attempts to discover PIFs for staphylococci were unsuccessful due to the time-based means used to identify mid-log. Both staphylococcal species produce extracellular, low-molecular-weight inducers of persistence when assayed using an OD600 -based PIF assay.

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Staphylococcus singaporensis sp. nov., a new member of the Staphylococcus aureus complex, isolated from human clinical specimens

INTERNATIONAL JOURNAL OF SYSTEMATIC AND EVOLUTIONARY MICROBIOLOGY ◽

10.1099/ijsem.0.005067 ◽

2021 ◽

Vol 71 (10) ◽

Author(s):

Ka Lip Chew ◽

Sophie Octavia ◽

Deborah Lai ◽

Raymond T. P. Lin ◽

Jeanette W. P. Teo

Keyword(s):

Staphylococcus Aureus ◽

Type Species ◽

Clinical Laboratory ◽

Core Gene ◽

Separate Species ◽

New Members ◽

Content Type ◽

Link Type ◽

Flight Mass Spectrometry ◽

Genotypic Analysis

Staphylococcus argenteus and Staphylococcus schweitzeri are the newest members of the Staphylococcus aureus complex. The number of clinical reports attributed to these new S. aureus complex members is limited. In a retrospective clinical laboratory study conducted over a 4-month period investigating the prevalence of S. argenteus and S. schweitzeri , a total of 43 isolates were selected. Phylogeny based on core-gene multilocus sequence typing (MLST) analysis confirmed that 37 were S. argenteus but a genetically distinct clade of six isolates was identified. Digital DNA–DNA hybridization (dDDH) and average nucleotide identity (ANI) analyses further supported the classification of these six isolates as a separate species. When compared to S. aureus complex reference genomes, the ANI values were ≤94 % and the dDDH values were <53 %. Based on the seven-gene S. aureus MLST scheme, the six isolates belong to five novel allelic profiles (ST6105, ST6106, ST6107, ST6108 and ST109). Their clinical infection features were similar to S. aureus . Skin and soft tissue infections presented in four out of the six cases. Routine clinical diagnostic identification using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and biochemical profiling does not differentiate these new members from the rest of the complex. Genotypic analysis suggests that the six isolates belong to a novel species, Staphylococcus singaporensis sp. nov. with isolate SS21T (=DSM 111408T=NCTC14419T) designated as the type strain.

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Geodermatophilus telluris sp. nov., an actinomycete isolated from Saharan desert sand

INTERNATIONAL JOURNAL OF SYSTEMATIC AND EVOLUTIONARY MICROBIOLOGY ◽

10.1099/ijs.0.046888-0 ◽

2013 ◽

Vol 63 (Pt_6) ◽

pp. 2254-2259 ◽

Cited By ~ 29

Author(s):

Maria del Carmen Montero-Calasanz ◽

Markus Göker ◽

Gabriele Pötter ◽

Manfred Rohde ◽

Cathrin Spröer ◽

...

Keyword(s):

Type Species ◽

Diaminopimelic Acid ◽

Molecular Characteristics ◽

Rrna Gene ◽

Content Type ◽

Link Type ◽

Desert Sand ◽

Diamino Acid ◽

Branched Chain ◽

Arid Desert

A novel Gram-positive, multiloculated thalli-forming, aerobic, actinobacterial strain, CF9/1/1T, was isolated in 2007 during environmental screening for xerophilic fungi in arid desert soil from the Sahara desert, Chad. The isolate grew best at a temperature range of 20–35 °C and at pH 6.0–8.5 and with 0–4 % (w/v) NaCl, forming black-coloured and irregular colonies on GYM agar. Chemotaxonomic and molecular characteristics of the isolate matched those described for members of the genus Geodermatophilus . The DNA G+C content of the novel strain was 75.4 mol%. The peptidoglycan contained meso-diaminopimelic acid as a diagnostic diamino acid. The main phospholipids were diphosphatidylglycerol, phosphatidylcholine, phosphatidylethanolamine, phosphatidylinositol, a not yet structurally identified aminophospholipid and a small amount of phosphatidylglycerol; MK-9(H4) was identified as the dominant menaquinone and galactose was a diagnostic sugar. The major cellular fatty acids were branched-chain saturated acids: iso-C16 : 0 and iso-C15 : 0. The 16S rRNA gene sequence of the isolate showed 94.6–97.0 % sequence similarities with those of five members of the genus: Geodermatophilus ruber DSM 45317T (94.6 %), Geodermatophilus obscurus DSM 43160T (94.8 %), Geodermatophilus siccatus DSM 45419T (96.2 %), Geodermatophilus nigrescens DSM 45408T (96.7 %) and Geodermatophilus arenarius DSM 45418T (97.0 %). Based on the evidence from this polyphasic taxonomic study, a novel species, Geodermatophilus telluris sp. nov., is proposed; the type strain is CF9/1/1T ( = DSM 45421T = CCUG 62764T).

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