Methicillin resistance in Staphylococcus pseudintermedius encoded within novel staphylococcal cassette chromosome mec (SCCmec) variants.

BACKGROUND: Staphylococcus pseudintermedius is a common opportunistic pathogen of companion dogs and an occasional human pathogen. Treatment is hampered by antimicrobial resistance including methicillin resistance encoded by mecA within the mobile genetic element SCCmec. OBJECTIVES: SCCmec elements are diverse, especially in non-Staphyloccocus aureus staphylococci, and novel variants are likely to be present in S. pseudintermedius. The aim was to characterize the SCCmec elements found in four canine clinical isolates of S. pseudintermedius. MATERIAL AND METHODS: Isolates were whole-genome sequenced and SCCmec elements were assembled, annotated and compared to known SCCmec types. RESULTS AND DISCUSSION: Two novel SSCmec are present in these isolates. SCCmec7017-61515 is characterized by a novel combination of a Class A mec gene complex and a type 5 ccr previously only described in composite SCCmec elements. The other three isolates share a novel composite SCCmec with features of SCCmec types IV and VI. CONCLUSIONS: S. pseudintermedius is a reservoir of novel SSCmec elements that has implications for understanding antimicrobial resistant in veterinary and human medicine.

Palaeomagnetic field intensity variations suggest Mesoproterozoic inner-core nucleation.

The Earth's inner core grows by the freezing of liquid iron at its surface. The point in history at which this process initiated marks a step-change in the thermal evolution of the planet. Recent computational and experimental studies have presented radically differing estimates of the thermal conductivity of the Earth's core, resulting in estimates of the timing of inner-core nucleation ranging from less than half a billion to nearly two billion years ago. Recent inner-core nucleation (high thermal conductivity) requires high outer-core temperatures in the early Earth that complicate models of thermal evolution. The nucleation of the core leads to a different convective regime and potentially different magnetic field structures that produce an observable signal in the palaeomagnetic record and allow the date of inner-core nucleation to be estimated directly. Previous studies searching for this signature have been hampered by the paucity of palaeomagnetic intensity measurements, by the lack of an effective means of assessing their reliability, and by shorter-timescale geomagnetic variations. Here we examine results from an expanded Precambrian database of palaeomagnetic intensity measurements selected using a new set of reliability criteria. Our analysis provides intensity-based support for the dominant dipolarity of the time-averaged Precambrian field, a crucial requirement for palaeomagnetic reconstructions of continents. We also present firm evidence for the existence of very long-term variations in geomagnetic strength. The most prominent and robust transition in the record is an increase in both average field strength and variability that is observed to occur between a billion and 1.5 billion years ago. This observation is most readily explained by the nucleation of the inner core occurring during this interval; the timing would tend to favour a modest value of core thermal conductivity and supports a simple thermal evolution model for the Earth.

Low prevalence of livestock-associated methicillin-resistant Staphylococcus aureus clonal complex 398 and mecC MRSA among human isolates in North-West England.

AIMS: Livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) is an important public health problem in many countries. Despite reports of such isolates being found in both animals and humans in the United Kingdom few data are available on the prevalence in humans of such isolates. A prevalence study was therefore undertaken in the north-west of England. METHODS AND RESULTS: One thousand two hundred and forty-two human MRSA isolates collected during 2015 were screened by PCR to detect two of the major forms of LA-MRSA: clonal complex (CC)398 and mecC MRSA. Isolates identified were further characterized by antimicrobial susceptibility testing and whole-genome sequencing using HiSeq technology. A single mecC MRSA isolate and three CC398 LA-MRSA were identified among the isolates screened. All four isolates were from MRSA screening. A phylogenetic analysis, including previously sequenced isolates from the United Kingdom, provided strong evidence for the genomic and epidemiological linkage between a pair of animal and human isolates of CC398 LA-MRSA in England. These data are indicative of animal and humans isolates of CC398 LA-MRSA being involved in the same transmission network and is the first demonstration of such closely linked animal and human isolates of this lineage in the UK. CONCLUSIONS: The study indicates there is a low prevalence of CC398 LA-MRSA and mecC MRSA among MRSA isolates in the sampled population. SIGNIFICANCE AND IMPACT OF THE STUDY: While the study demonstrates that LA-MRSA were rare among human MRSA isolates in the sampled population, the data provide a baseline for the future surveillance of what is a significant public health challenge in some regions. The demonstration of linked human and animal isolates of CC398 LA-MRSA, supported by genomic and epidemiological data, reinforces the need for such surveillance and for continued awareness of the risks that LA-MRSA may pose in the UK.

A mecC allotype, mecC3, in the CoNS Staphylococcus caeli, encoded within a variant SCCmecC.

BACKGROUND: Methicillin resistance in staphylococci is conferred by an alternative PBP (PBP2a/2') with low affinity for most ß-lactam antibiotics. PBP2a is encoded by mecA, which is carried on a mobile genetic element known as SCCmec. A variant of mecA, mecC, was described in 2011 and has been found in Staphylococcus aureus from humans and a wide range of animal species as well as a small number of other staphylococcal species from animals. OBJECTIVES: We characterized a novel mecC allotype, mecC3, encoded by an environmental isolate of Staphylococcus caeli cultured from air sampling of a commercial rabbit holding. METHODS: The S. caeli isolate 82BT was collected in Italy in 2013 and genome sequenced using MiSeq technology. This allowed the assembly and comparative genomic study of the novel SCCmec region encoding mecC3. RESULTS: The study isolate encodes a novel mecA allotype, mecC3, with 92% nucleotide identity to mecC. mecC3 is encoded within a novel SCCmec element distinct from those previously associated with mecC, including a ccrAB pairing (ccrA5B3) not previously linked to mecC. CONCLUSIONS: This is the first description of the novel mecC allotype mecC3, the first isolation of a mecC-positive Staphylococcus in Italy and the first report of mecC in S. caeli. Furthermore, the SCCmec element described here is highly dissimilar to the archetypal SCCmec XI encoding mecC in S. aureus and to elements encoding mecC in other staphylococci. Our report highlights the diversity of mecC allotypes and the diverse staphylococcal species, ecological settings and genomic context in which mecC may be found.

Anomalous Temperature Behavior of the Chiral Spin Helix in CrNb_{3}S_{6} Thin Lamellae.

Using Lorentz transmission electron microscopy and small-angle electron scattering techniques, we investigate the temperature-dependent evolution of a magnetic stripe pattern period in thin-film lamellae of the prototype monoaxial chiral helimagnet CrNb_{3}S_{6}. The sinusoidal stripe pattern appears due to formation of a chiral helimagnetic order (CHM) in this material. We found that as the temperature increases, the CHM period is initially independent of temperature and then starts to shrink above the temperature of about 90 K, which is far below the magnetic phase transition temperature for the bulk material T_{c} (123 K). The stripe order disappears at around 140 K, far above T_{c}. We argue that this cascade of transitions reflects a three-stage hierarchical behavior of melting in two dimensions.

Streptococcus hillyeri sp. nov., isolated from equine trachea.

Strain 28462T, which had Gram-stain-positive, catalase-negative coccus-shaped cells, was isolated from a routine tracheal sample from a 3 year old thoroughbred horse. 16S rRNA gene sequence analysis revealed it to be most closely related to, but distinct from, Streptococcus henryi (95.7 % identity), Streptococcusplurextorum (95.8 %), Streptococcusporci (96.4 %) and Streptococcus caprae (95.1 %). Similarity values derived from sequences from sodA and rpoB genes were consistent with strain 28462T belonging to a species distinct from these four streptococci. At the whole genome level, strain 28462T had an average nucleotide identity value <95 % and an inferred DNA-DNA hybridization value <70 % when compared to S. henryi, Streptococcus. plurextorum and S. porci with no S. caprae genome sequence being available. Finally, various phenotypic characteristics distinguish strain 28462T from each of these species. Based on the genotypic and phenotypic results, it is proposed that strain 28462T is a novel species, with the name Streptococcus hillyeri sp. nov. The type strain is 28462T (=DSM 107591T=CCUG 72762T).

Staphylococcus caeli sp. nov., isolated from air sampling in an industrial rabbit holding.

Strain 82T, a Gram-stain-positive, coagulase-negative staphylococcus was isolated from an air sample obtained from an industrial rabbit holding in Italy. It is phylogenetically closely related to the coagulase-negative species Staphylococcus saprophyticus, Staphylococcus xylosus and Staphylococcus edaphicus. However, it could be distinguished from these species by sequence differences between the 16S rRNA, hsp60, rpoB, dnaJ and gap genes. At the whole genome level, the isolate had an average nucleotide identity of <95 % and an inferred DNA-DNA hybridization of <70 % when compared to these species. Based on the genotypic results, it is proposed that this isolate is a novel species, with the name Staphylococcus caeli sp. nov. The type strain is 82BT (=NCTC 14063T=CCUG 71912T).

Staphylococcus pseudoxylosus sp. nov., isolated from bovine mastitis.

Strain S04009T, a Gram-stain-positive, coagulase-negative staphylococcus, was isolated from bovine mastitis in France. 16S rRNA gene analysis revealed it to be closely related to the coagulase-negative species Staphylococcusxylosus, Staphylococcussaprophyticus, Staphylococcuscaeli and Staphylococcus edaphicus. At the whole-genome level, strain S04009T had an average nucleotide identity value <95 % and an inferred DNA-DNA hybridization value <70 % when compared to these species. Furthermore, phenotypic characteristics distinguished S04009T from those species. From these related species only strain S04009T and S. xylosus are able to ferment xylose and these two can be distinguished by the inability of strain S04009T to express urease activity. Based on the genotypic and phenotypic results, it is proposed that this isolate is a novel species, with the name Staphylococcus pseudoxylosus sp. nov. The type strain is S04009T (=DSM 107950T=CCUG 72763T=NCTC 14184T).

Detection of livestock-associated meticillin-resistant Staphylococcus aureus CC398 in retail pork, United Kingdom, February 2015.

Livestock-associated meticillin-resistant Staphylococcus aureus belonging to clonal complex 398 (LA-MRSA CC398) is an important cause of zoonotic infections in many countries. Here, we describe the isolation of LA-MRSA CC398 from retail meat samples of United Kingdom (UK) farm origin. Our findings indicate that this lineage is probably established in UK pig farms and demonstrate a potential pathway for the transmission of LA-MRSA CC398 from livestock to humans in the UK.

Prevalence and properties of mecC methicillin-resistant Staphylococcus aureus (MRSA) in bovine bulk tank milk in Great Britain.

OBJECTIVES: mecC methicillin-resistant Staphylococcus aureus (MRSA) represent a newly recognized form of MRSA, distinguished by the possession of a divergent mecA homologue, mecC. The first isolate to be identified came from bovine milk, but there are few data on the prevalence of mecC MRSA among dairy cattle. The aim of this study was to conduct a prevalence study of mecC MRSA among dairy farms in Great Britain. METHODS: Test farms were randomly selected by random order generation and bulk tank samples were tested for the presence of mecC MRSA by broth enrichment and plating onto chromogenic agar. All MRSA isolated were screened by PCR for mecA and mecC, and mecC MRSA were further characterized by multilocus sequence typing, spa typing and antimicrobial susceptibility testing. RESULTS: mecC MRSA were detected on 10 of 465 dairy farms sampled in England and Wales (prevalence 2.15%, 95% CI 1.17%-3.91%), but not from 625 farms sampled in Scotland (95% CI of prevalence 0%-0.61%). Seven isolates belonged to sequence type (ST) 425, while the other three belonged to clonal complex 130. Resistance to non-ß-lactam antibiotics was uncommon. All 10 isolates produced a negative result by slide agglutination for penicillin-binding protein 2a. mecA MRSA ST398 was detected on one farm in England. CONCLUSIONS: mecC MRSA is widely distributed among dairy farms in Great Britain, but this distribution is not uniform across the whole country. These results provide an important baseline dataset to monitor the epidemiology of this emerging form of MRSA.

Prevalence and characterization of human mecC methicillin-resistant Staphylococcus aureus isolates in England.

OBJECTIVES: There are limited data available on the epidemiology and prevalence of methicillin-resistant Staphylococcus aureus (MRSA) in the human population that encode the recently described mecA homologue, mecC. To address this knowledge gap we undertook a prospective prevalence study in England to determine the prevalence of mecC among MRSA isolates. PATIENTS AND METHODS: Three hundred and thirty-five sequential MRSA isolates from individual patients were collected from each of six clinical microbiology laboratories in England during 2011-12. These were tested by PCR or genome sequencing to differentiate those encoding mecA and mecC. mecC-positive isolates were further characterized by multilocus sequence typing, spa typing, antimicrobial susceptibility profile and detection of PBP2a using commercially available kits. RESULTS: Nine out of the 2010 MRSA isolates tested were mecC positive, indicating a prevalence among MRSA in England of 0.45% (95% CI 0.24%-0.85%). The remainder were mecA positive. Eight out of these nine mecC MRSA isolates belonged to clonal complex 130, the other being sequence type 425. Resistance to non-ß-lactam antibiotics was rare among these mecC MRSA isolates and all were phenotypically identified as MRSA using oxacillin and cefoxitin according to BSAC disc diffusion methodology. However, all nine mecC isolates gave a negative result using three different commercial PBP2a detection assays. CONCLUSIONS: mecC MRSA are currently rare among MRSA isolated from humans in England and this study provides an important baseline prevalence rate to monitor future changes, which may be important given the increasing prevalence of mecC MRSA reported in Denmark.

Conjugative transfer frequencies of mef(A)-containing Tn1207.3 to macrolide-susceptible Streptococcus pyogenes belonging to different emm types.

UNLABELLED: The aim of this study was to examine the gene transfer potential of mef(A)-containing Tn120.3 to macrolide-susceptible Streptococcus pyogenes belonging to different emm types. Using the filter mating technique, Tn1207.3 was transferred by conjugation to 23 macrolide-susceptible recipients representing 11 emm types. PCR analysis confirmed the presence of the mef(A) gene and the comEC junction regions of the Tn1207.3 insertion in resultant transconjugants. Significant variation was found in the transfer frequency of Tn1207.3 to different Strep. pyogenes strains, and this phenomenon may contribute to the differences in mef(A) frequency observed among clinical isolates. SIGNIFICANCE AND IMPACT OF THE STUDY: The spread of antimicrobial resistance among pathogenic bacteria is an important problem, but the mechanisms of horizontal transfer between strains and species are often poorly understood. For instance, little is known on how macrolide resistance spreads between strains of the human pathogen Strep. pyogenes and why certain strains more commonly display resistance than others. Here, we show that Strep. pyogenes strains vary greatly in their ability to acquire a transposon encoding macrolide resistance by horizontal gene transfer in vitro. These data provide a novel insight into the transfer of antibiotic resistance between bacterial strains and offer an explanation for the differences in the frequency of resistance determinates and resistance seen among clinical isolates.

Short communication: biofilm production characterization of mecA and mecC methicillin-resistant Staphylococcus aureus isolated from bovine milk in Great Britain.

Staphylococcus aureus is an important cause of contagious intramammary infection in dairy cattle, and the ability to produce biofilm is considered to be an important virulence property in the pathogenesis of mastitis. The aim of this study was to characterize the biofilm formation capacity of methicillin-resistant Staph. aureus (MRSA), encoding mecA or mecC, isolated from bulk tank milk in Great Britain. For this purpose, 20 MRSA isolates were grown on microtiter plates to determine the biofilm production. Moreover, the spa-typing and the presence of the intercellular adhesion genes icaA and icaD were analyzed by PCR. All MRSA isolates tested belonged to 9 spa-types and were PCR-positive for the ica genes; 10 of them (50%) produced biofilm in the microtiter plate assay. This is also the first demonstration of biofilm production by mecC MRSA.

Not just in man's best friend: A review of Staphylococcus pseudintermedius host range and human zoonosis.

Staphylococcus pseudintermedius is one species in the commensal staphylococcal population in dogs. While it is commonly carried on healthy companion dogs it is also an opportunistic pathogen associated with a range of skin, ear, wound and other infections. While adapted to dogs, it is not restricted to them, and we have reviewed its host range, including increasing reports of human colonisation and infections. Despite its association with pet dogs, S. pseudintermedius is found widely in animals, covering companion, livestock and free-living species of birds and mammals. Human infections, typically in immunocompromised individuals, are increasingly being recognised, in part due to improved diagnosis. Colonisation, infection, and antimicrobial resistance, including frequent multidrug resistance, among S. pseudintermedius isolates represent important One Health challenges.

Learning safe practice by improving care: student-led intervention on oxygen prescribing in a respiratory ward.

BACKGROUND AND OBJECTIVE: The primary aim of this intervention was to improve oxygen prescribing in accordance with the 2008 British Thoracic Society guidelines for the prescription of emergency oxygen in adults. METHODS: Eight final year medical students reviewed the drug charts of all patients admitted to the respiratory ward on a daily basis in order to collect data on five audit questions: (1) Has oxygen (O2) been prescribed? (2) Has an O2 target saturation level been indicated? (3) Has O2 been prescribed as an 'as required' (PRN) or 'continuous therapy'? (4) Has the prescription been signed? (5) Has O2 been signed for in every drug round since the original prescription? Following an initial audit cycle an educational poster was distributed to all clinical staff via email and hard copies of the poster were placed strategically throughout the ward before its effectiveness was measured. RESULTS: During the pre-intervention phase, compliance with all five measures varied from 0 to 25%. There was an increase in the variation in compliance after the poster intervention to 14-44%; however, this masked better overall compliance with all five investigative questions with figures of 44%, 39% and 42% being recorded in three of the four post-intervention days. Overall there was increased compliance with four of the five audit questions. Indeed compliance with question 3 rose from 14% to 83%. CONCLUSIONS: The poster intervention was marginally effective while also showing that students can improve prescribing in a clinical setting.

The newly described mecA homologue, mecALGA251, is present in methicillin-resistant Staphylococcus aureus isolates from a diverse range of host species.

OBJECTIVES: A previously unidentified mecA homologue, mecA(LGA251), has recently been described in methicillin-resistant Staphylococcus aureus (MRSA) from humans and dairy cattle. The origin and epidemiology of this novel homologue are unclear. The objective of this study was to provide basic descriptive information of MRSA isolates harbouring mecA(LGA251) from a range of host animal species. METHODS: A number of S. aureus isolates from historical animal isolate collections were chosen for investigation based on their similarity to known mecA(LGA251) MRSA isolates. The presence of mecA(LGA251) was determined using a multiplex PCR and antimicrobial susceptibility testing performed by disc diffusion. RESULTS: MRSA harbouring mecA(LGA251) were found in isolates from a domestic dog, brown rats, a rabbit, a common seal, sheep and a chaffinch. All of the isolates were phenotypically MRSA, although this depended on which test was used; some isolates would be considered susceptible with certain assays. All isolates were susceptible to linezolid, rifampicin, kanamycin, norfloxacin, erythromycin, clindamycin, fusidic acid, tetracycline, trimethoprim/sulfamethoxazole and mupirocin. Five multilocus sequence types were represented (2273, 130, 425, 1764 and 1245) and six spa types (t208, t6293, t742, t6594, t7914 and t843). CONCLUSIONS: The discovery of MRSA isolates possessing mecA(LGA251) from a diverse range of host species, including different taxonomic classes, has important implications for the diagnosis of MRSA in these species and our understanding of the epidemiology of this novel mecA homologue.

First detection of livestock-associated meticillin-resistant Staphylococcus aureus CC398 in bulk tank milk in the United Kingdom, January to July 2012.

Livestock-associated meticillin-resistant Staphylococcus aureus belonging to clonal complex 398 (LA-MRSA CC398) is an important cause of zoonotic infections in several countries, but there is only a single published report of this lineage from the United Kingdom (UK). Here, we describe the isolation of LA-MRSA CC398 from bulk tank milk from five geographically dispersed farms in the UK. Our findings suggest that LA-MRSA CC398 is established in livestock in the UK. Awareness of the potential occupational risks and surveillance in other food-producing animal species should be promoted.

Rotationally elastic and inelastic dynamics of NO(X2Π, v = 0) in collisions with Ar.

A combined theoretical and experimental study of the depolarization of selected NO(X(2)Π, v = 0, j, F, ɛ) levels in collisions with a thermal bath of Ar has been carried out. Rate constants for elastic depolarization of rank K = 1 (orientation) and K = 2 (alignment) were extracted from collision-energy-dependent quantum scattering calculations, along with those for inelastic population transfer to discrete product levels. The rate constants for total loss of polarization of selected initial levels, which are the sum of elastic depolarization and population transfer contributions, were measured using a two-color polarization spectroscopy technique. Theory and experiment agree qualitatively that the rate constants for total loss of polarization decline modestly with j, but the absolute values differ by significantly more than the statistical uncertainties in the measurements. The reasons for this discrepancy are as yet unclear. The lack of a significant K dependence in the experimental data is, however, consistent with the theoretical prediction that elastic depolarization makes only a modest contribution to the total loss of polarization. This supports a previous conclusion that elastic depolarization for NO(X(2)Π) + Ar is significantly less efficient than for the electronically closely related system OH(X(2)Π) + Ar [P. J. Dagdigian and M. H. Alexander, J. Chem. Phys. 130, 204304 (2009)].

Salmonella enterica serovar typhimurium trxA mutants are protective against virulent challenge and induce less inflammation than the live-attenuated vaccine strain SL3261.

In Salmonella enterica serovar Typhimurium, trxA encodes thioredoxin 1, a small, soluble protein with disulfide reductase activity, which catalyzes thiol disulfide redox reactions in a variety of substrate proteins. Thioredoxins are involved as antioxidants in defense against oxidative stresses, such as exposure to hydrogen peroxide and hydroxyl radicals. We have made a defined, complete deletion of trxA in the mouse-virulent S. Typhimurium strain SL1344 (SL1344 trxA), replacing the gene with a kanamycin resistance gene cassette. SL1344 trxA was attenuated for virulence in BALB/c mice by the oral and intravenous routes and when used in immunization experiments provided protection against challenge with the virulent parent strain. SL1344 trxA induced less inflammation in murine spleens and livers than SL3261, the aroA mutant, live attenuated vaccine strain. The reduced splenomegaly observed following infection with SL1344 trxA was partially attributed to a reduction in the number of both CD4(+) and CD8(+) T cells and B lymphocytes in the spleen and reduced infiltration by CD11b(+) cells into the spleen compared with spleens from mice infected with SL3261. This less severe pathological response indicates that a trxA mutation might be used to reduce reactogenicity of live attenuated vaccine strains. We tested this by deleting trxA in SL3261. SL3261 trxA was also less inflammatory than SL3261 but was slightly less effective as a vaccine strain than either the SL3261 parent strain or SL1344 trxA.