Molecular epidemiology of methicillin-resistant S. aureus (MRSA) in veterinary medicine

Deckblatt-Impressum Inhaltsverzeichnis Abkürzungen Einleitung Schrifttum Material Methoden Ergebnisse Diskussion Zusammenfassung Summary Referenzen Danksagung SelbständigkeitserklärungEinige S. aureus-Populationen, die sich im hospitalassoziierten Milieu seit vielen Jahren etabliert haben, erlangen multiple Resistenzen durch die Akkumulation verschiedener Resistenzdeterminaten. Insbesondere Methicillin- resistente Staphylococcus aureus (MRSA) sind heute weltweit einer der häufigsten Verursacher von sporadischen sowie endemischen Infektionen in Krankenhäusern, anderen Gesundheitseinrichtungen und auch in ambulanten Bereichen. Seit den frühen 70er Jahren werden MRSA-Fälle auch bei Tieren berichtet. In den letzten Jahren kam es jedoch zu einem deutlichen Anstieg von Berichten über MRSA-infizierte Tiere, insbesondere bei Kleintieren und Pferden in klinischen Einrichtungen. Auch die Frage nach dem zoonotischen Charakter animaler MRSA wird zunehmend diskutiert. Diese Arbeit verfolgte deshalb vier wesentliche Ziele. Zunächst wurden vergleichend Untersuchungen zu verschiedenen phänotypischen Nachweisverfahren für die MRSA-Diagnostik in der Veterinärmedizin durchgeführt. Ein zweiter Punkt war die Erfassung von Daten über das Vorkommen, die Typisierung sowie die genetische Charakterisierung von MRSA-Isolaten von Pferden und Kleintieren. In Zusammenarbeit mit der Klinik und Poliklinik für kleine Haustiere der Freien Universität Berlin wurde das dritte Ziel verfolgt, die Aufdeckung von möglichen zoonotischen Transmissionswegen sowie die nosokomiale Verbreitung von MRSA in klinischen Einrichtungen der Veterinärmedizin unter Einbeziehung von Tieren, Menschen und Gegenständen. Das vierte angestrebte Ziel dieser Arbeit umfasste die Analyse der gesammelten Daten unter epidemiologischen Gesichtspunkten und Einordnung der untersuchten Isolate in die bislang bekannten S. aureus- Population sowie den Vergleich zu einigen häufig auftretenden humanen Epidemiestämmen. Um alle MRSA-Isolate zu typisieren, wurden verschiedene international gebräuchliche Methoden eingesetzt. Durch den Einsatz einer Pulsfeld-Gel-Elektrophorese (PFGE) nach Makrorestriktion mittels der Endonuklease SmaI war ein Vergleich der Restriktionsmuster des Gesamtgenoms aller Isolate realisierbar. Unter Anwendung der Multi-Locus-Sequenztypisierung (MLST) war eine Zuordnung der hier aufgetretenen mit bereits bekannten und in einer Online-Datenbank (www.mlst.net) hinterlegten Sequenztypen (ST) möglich. Die Typisierung des mobilen Staphylokokken-Austauschsystems (SCCmec), welches den mec-Komplex beinhaltet, wurde in dieser Arbeit mit einer bereits beschriebenen Multiplex- Strategie verfolgt, die jedoch nicht in jedem Fall zu einem eindeutigen Ergebnis führte. Insgesamt sind in dieser Arbeit 1544 Einzelproben (davon 144 vordifferenzierte Keimisolate aus anderen veterinärmedizinischen diagnostischen Laboren) von Tieren, Menschen und Gegenständen untersucht worden. Im ersten Abschnitt wurden die verschiedenen Verfahren für den phänotypischen Nachweis animaler MRSA vergleichend getestet, wobei festgestellt werden konnte, dass der Agardiffusionstest mit Cefoxitin (30µg) anderen Methoden, wie z.B. dem Agardiffusionstest mit Oxacillin 1 und 5µg sowie dem Einsatz eines Oxacillin-Screeningagars, deutlich unterlegen ist. Der Goldstandard für den Nachweis der Resistenzdeterminante mecA ist jedoch noch immer ein spezifischer Gennachweis mittels Polymerase-Kettenreaktion (PCR), möglichst verbunden mit einem eindeutigen Speziesnachweis. Zu diesem Zweck wurde eine Triplex-PCR erarbeitet, die neben dem für die ß-Lactamresistenz verantwortlichen Gen mecA gleichzeitig Spezies-spezifische Nachweise von S. aureus und S. intermedius ermöglicht. Im zweiten Teil der Ergebnisse wurden MRSA-Isolaten von Pferden und Kleintieren analysiert. In den insgesamt 135 untersuchten Proben (davon 70 S. aureus) von Pferden aus unterschiedlichen Bundesländern von verschiedenen klinisch infizierten Tieren konnte in 11 Proben (15,7%) ein MRSA-Nachweis geführt werden. Die dabei aufgetretenen Genotypen, welche in dieser Arbeit mit den Großbuchstaben "A", "B", "C" benannt wurden, erzielten in der Analyse dieser Muster aus der PFGE einen genetischen Übereinstimmungsgrad von ca. 86%, der sich auch in der engen Verwandtschaft der mittels MLST ermittelten Sequenztypen ST8 und ST254 widerspiegelt. Diese ST unterscheiden sich tatsächlich lediglich in einem Basenpaar im ersten Allel der für die Bestimmung herangezogenen definierten Abschnitte von sieben konservativen Haushaltsgenen. Leider schränkt die begrenzte Anzahl der untersuchten Isolate von Pferden die Aussagekraft der Daten ein. Alle Staphylokokken-Genkassetten (SCCmec) aus equinen MRSA-Isolaten waren Vertreter der bislang kleinsten bekannten Kassette vom Typ SCCmec IV. Weitere 6 MRSA-Isolate von Kleintieren aus anderen Bundesländern zeigten die PFGE- Muster: "F", "D" und "H" sowie Subtypen. Die hier durch MLST ermittelten Sequenztypen waren ST254, ST225 und ST239. Während bei fünf Isolaten ebenfalls SCCmec IV auftrat, zeigte sich ein Isolat aus Gießen (ST225) positiv für SCCmec II. Im dritten Abschnitt dieser Arbeit wurde S. aureus in der Kleintierklinik über einen Zeitraum von 20 Monaten in insgesamt 6,9% (60/866) der klinischen Proben gefunden. 26 von diesen waren mecA-positiv, darunter auch Isolate von so exotischen Tieren wie Papagei, Schildkröte oder Fledermaus. Außerdem wurden Nasentupfer von Hunden (257 Tupfer von 191 Tieren), von Menschen (dreimal n=62, n=62 und n=88) und Objekten (20) untersucht. Dabei wurde in 6 Fällen bei Hunden, bei 20 Personen und an 3 Objekten ein MRSA Nachweis geführt. Lokal dominierten hier überwiegend zwei verschiedene PFGE Typen, hier als "G" und "D" bezeichnet. Die MLST-Analyse zeigte zwei genetisch unterschiedliche MRSA-Klone: PFGE-Typ "G" entspricht dem ST22, der PFGE-Typ "D" hingegen entspricht dem ST239. Neben dem SCCmec IV, der generell bei PFGE Typ "D" nachzuweisen war, schlug die eindeutige Charakterisierung der Genkassette des PFGE-Typs "G" mit denen in dieser Arbeit eingesetzten Techniken fehl. Eine Auswertung der Daten aus der Kleintierklinik unter einigen epidemiologischen Aspekten zeigte, dass eine zeitweise nosokomiale Verbreitung der genannten Klone innerhalb dieser Institution angenommen werden darf. Den Abschluss dieser Arbeit bildete die Einordnung der bei animalen MRSA-Isolaten dieser Arbeit aufgetretenen STen in einen S. aureus-Populationszusammenhang, der hier unter Einbeziehung von Daten über bislang bekannte S. aureus-STen aus der Datenbank www.mlst.net durch die Erstellung eines Minimum-Spannig-Trees. Dabei konnte gezeigt werden, dass alle in dieser Arbeit aufgetreten STen (ST8, ST239, ST254, ST225, ST22) bereits häufig in der Humanmedizin als MRSA in Erscheinung getreten sind und etablierten klonalen Komplexen angehören, also keinesfalls "neue" genotypische Linien begründen oder vertreten. Die vorliegenden Daten belegen, dass sich nosokomiale Infektionen, insbesondere solche durch MRSA, sich in der Veterinärmedizin etabliert haben. Aufgrund der ständigen Anpassungsvorgänge der Infektionserreger an ihre Umgebung und ihr hohes Adaptionsvermögen an Wirtsorganismen anderer Spezies ist die Erarbeitung standardisierter Hygienerichtlinien, die der Transmission von Tier zu Tier aber auch zwischen Mensch und Tier entgegenwirken, auch für veterinärmedizinischen Praxen und Kliniken erforderlich. Die Bedeutung von MRSA-Infektionen bei Tieren als Quelle und / oder Reservoir für MRSA-Erkrankungen beim Menschen ist bislang noch vollkommen ungeklärt. Durch die nachweislich leichte Übertragbarkeit, insbesondere in einer Umgebung mit Selektionsdruck (Praxis, Klinik), ist jedoch davon auszugehen, dass das Risiko für Transmissionen zwischen Mensch und Tier bei engem Kontakt bzw. mangelnder Hygiene nicht zu unterschätzen ist.Various populations of S. aureus, which have established themselves in the hospital environment over the last decades, have acquired different resistance factors and are now difficult to combat, even in the field of veterinary medicine. In particular, Methicillin-resistant Staphylococcus aureus (MRSA) are one of the most predominant causes of sporadic and endemic infections in hospitals as well as in hospital-adapted institutions. Since the early `70s, infections due to MSRA have also been reported in animals. In the last years, however, there have been increasing reports about MRSA infections in small animals and horses. Recently published studies address the potential of interspecies transferability, or the zoonotic character of MRSA. The aim of this work was to compile data and knowledge about the occurrence and relevance of MRSA in the field of veterinary medicine. Therefore, four main goals were defined prior to this work. First of all, a comparative investigation of different methods for phenotypical identification of MRSA of animal origin was performed. A second point of interest was the recording of data concerning occurrence, patterns of resistance and characterization of relevant genetic markers. In close cooperation with the clinic and policlinic for small animals of the Free University of Berlin, a third goal was set: To pinpoint the zoonotic potential of some MRSA lineages and detection of potential nosocomial transmission pathways in a clinical setting. The last intention of this investigation was to analyze all recorded data from an epidemiological point of view. Therefore, isolates originating from animals were compared to a set of data from human MRSA strains and assigned to a database that provided information about several S. aureus-genotypes. International recommended methods were applied to characterize the MRSA isolates in this work. Clonal analysis was performed by employing endonuclease SmaI digestion, followed by pulsed-field gel-electrophoresis (PFGE) in order to compare the genomic marcrorestriction patterns of all isolates. Multilocus sequence typing (MLST), which is based on the sequence analysis of defined sections of seven housekeeping genes, enabled the assignment of sequence types (ST) to each MRSA and into the whole S. aureus population analysed so far (www.mlst.net). Typing of the mobile genetic element (SCCmec), which harbours the mec-complex in staphylococci, was carried out using a previously published Multiplex polymerase chain reaction (PCR) strategy. Unfortunately, this PCR typing did not always produce satisfying results. A total of 1,544 specimens (including 144 isolates from other veterinary facilities) from animals, humans and everyday objects were examined in this work. Comparing different phenotypical methods to diagnose MRSA from animal origin revealed that the agar diffusion test with Cefoxitin (30ug) seems to be superior to other methods, e.g. agar diffusion test with Oxacillin 1µg and 5µg as well as an Oxacillin screening agar. Despite these results, the best method for MRSA verification still is PCR, detecting the mecA gene that codes for the resistance determinant as well as a species-specific marker like the nuc gene and/or a specific 16S rDNA sequence. Samples from 135 S. aureus infected horses were sent in from different veterinary microbiological institutions in Germany. Upon examination, 70 samples proved to contain S. aureus, 11 of those turned out to be positive for MRSA (15.7%). By applying PFGE, three clonal types were identified and designated as "A", "B", "C". Surprisingly, these clonaltypes showed a degree of genetic similarity of 86%. A second examination emphasized these findings, proving this close relationship. The detected STs, determined by MLST, turned out to be the closely-related ST8 and ST254, which differ from each other only by substitution of a single base-pair (bp) in one of the seven housekeeping genes sequenced (arcC, aroE, glpF, gmk, pta, tpi, ypiL). Unfortunately, the restricted number of horse isolates investigated here is a limiting factor in the interpretation of these results. All recorded staphylococcal chromosomal cassettes (SCCmec) from equine MRSA isolates in this work proved to be SCCmec IV. Additional 6 MRSA isolates of small animals from different sources in Germany showed different PFGE types: "F", "D" and "H" as well as subtypes. The obtained sequence types determined by MLST were ST254, ST225 and ST239. While five isolates proved to contain SCCmec IV, one isolate (out of those related to ST225) was positive for SCCmec II. In the third part of this work, during an investigation period of 20 months, S. aureus was found in 6.9% (60/866) of all clinical samples being sent to our laboratory for diagnostic purposes from the small animal hospital. Twenty-six of these tested positive for mecA (including isolates from exotic animals such as parrots, turtles as well as a bat). In addition, we collected and investigated nasal specimens from dogs (257 specimens of 191 animals) and humans (tested three times: n=62; n=62; and n=88). Furthermore, 20 samples of everyday objects were analysed. MRSA was detected in six canine cases, in nasal specimens from 20 persons, and on 3 objects. Two different PFGE types dominated in this setting during the investigation period, namely type "G" and "D". MLST analysis showed two genetically different MRSA clones: PFGE type "G" corresponded to ST22, and PFGE type "D" was determined to ST239. Despite the SCCmec IV, which was found to be related to type "D", the utilized SCC-typing techniques used in this work failed in typing SCCmec in PFGE type "G". In regard to epidemiological aspects, evaluating data from this small animal hospital indicated that an occasional nosocomial spread of the aforementioned MRSA clones may have occurred within this institution. The final part of this investigation was to classify all MRSA ST which had been identified during this work, in an epidemical context by using additional data from www.mlst.net in performing a Minimum spanning tree analysis. This approach could demonstrate that all MRSA STs in this thesis (ST8, ST239, ST254, ST225, ST22) have also been frequently observed in isolates from human MRSA infections with an almost global occurrence. The data presented here are evidence of nosocomial infections due to MSRA in veterinary medicine facilities. Due to the constant adaptation processes of infectious agents to their environment and their high adaptability to host organisms of different (animal) species, the development of standardized hygienic guidelines for veterinary practice and hospitals should be enforced. Especially the potential nosocomial transmission of MRSA from animal to animal as well as between human and animal should be the focus of hygienic measures as well as future research. The current relevance of MRSA infections in animals as a potential source and/or reservoir for MRSA mediated infections in humans is still unknown. The apparent ready transferability of MRSA, in particular in an environment with a certain selection pressure (practice, hospital), showed that the risk for nosocomial transmission between human and animal with close contact and/or lack of hygienic measures must be taken seriously

Complete Genome Sequence of the Livestock-Associated Methicillin-Resistant Strain Staphylococcus aureus subsp. aureus 08S00974 (Sequence Type 398)

We report here the complete genome sequence of the livestock-associated methicillin-resistant Staphylococcus aureus strain 08S00974 from sequence type 398 (ST398 LA-MRSA) isolated from a fatting pig at a farm in Germany

Complete Genome Sequence of the Disinfectant Susceptibility Testing Reference Strain Staphylococcus aureus subsp. aureus ATCC 6538

We report here the complete genome sequence of the methicillin-sensitive Staphylococcus aureus subsp. aureus strain ATCC 6538 (FDA 209, DSM 799, WDCM 00032, and NCTC 10788)

Stationsprüfbericht Schaf 2010

Ergebnisse der 15. Mast- und Schlachtleistungsprüfung beim Schaf aus der Prüfstation Köllitsch 201

Effects of a Four-Week High-Dosage Zinc Oxide Supplemented Diet on Commensal Escherichia coli of Weaned Pigs

Strategies to reduce economic losses associated with post-weaning diarrhea in pig farming include high-level dietary zinc oxide supplementation. However, excessive usage of zinc oxide in the pig production sector was found to be associated with accumulation of multidrug resistant bacteria in these animals, presenting an environmental burden through contaminated manure. Here we report on zinc tolerance among a random selection of intestinal Escherichia coli comprising of different antibiotic resistance phenotypes and sampling sites isolated during a controlled feeding trial from 16 weaned piglets: In total, 179 isolates from “pigs fed with high zinc concentrations” (high zinc group, [HZG]: n = 99) and a corresponding “control group” ([CG]: n = 80) were investigated with regard to zinc tolerance, antimicrobial- and biocide susceptibilities by determining minimum inhibitory concentrations (MICs). In addition, in silico whole genome screening (WGSc) for antibiotic resistance genes (ARGs) as well as biocide- and heavy metal tolerance genes was performed using an in-house BLAST-based pipeline. Overall, porcine E. coli isolates showed three different ZnCl2 MICs: 128 μg/ml (HZG, 2%; CG, 6%), 256 μg/ml (HZG, 64%; CG, 91%) and 512 μg/ml ZnCl2 (HZG, 34%, CG, 3%), a unimodal distribution most likely reflecting natural differences in zinc tolerance associated with different genetic lineages. However, a selective impact of the zinc-rich supplemented diet seems to be reasonable, since the linear mixed regression model revealed a statistically significant association between “higher” ZnCl2 MICs and isolates representing the HZG as well as “lower ZnCl2 MICs” with isolates of the CG (p = 0.005). None of the zinc chloride MICs was associated with a particular antibiotic-, heavy metal- or biocide- tolerance/resistance phenotype. Isolates expressing the 512 μg/ml MIC were either positive for ARGs conferring resistance to aminoglycosides, tetracycline and sulfamethoxazole-trimethoprim, or harbored no ARGs at all. Moreover, WGSc revealed a ubiquitous presence of zinc homeostasis and – detoxification genes, including zitB, zntA, and pit. In conclusion, we provide evidence that zinc-rich supplementation of pig feed selects for more zinc tolerant E. coli, including isolates harboring ARGs and biocide- and heavy metal tolerance genes – a putative selective advantage considering substances and antibiotics currently used in industrial pork production systems

In situ characterization of polycaprolactone fiber response to quasi-static tensile loading in scanning electron microscopy

Microstructural responses to the mechanical load of polymers used in tissue engineering is notably important for qualification at in vivo testing, although insufficiently studied, especially regarding promising polycaprolactone (PCL). For further investigations, electrospun PCL scaffolds with different degrees of fiber alignment were produced, using two discrete relative drum collector velocities. Development and preparation of an adjusted sample geometry enabled in situ tensile testing in scanning electron microscopy. By analyzing the microstructure and the use of selected tracking techniques, it was possible to visualize and quantify fiber/fiber area displacements as well as local fractures of single PCL fibers, considering quasi-static tensile load and fiber alignment. The possibility of displacement determination using in situ scanning electron microscopy techniques for testing fibrous PCL scaffolds was introduced and quantified. © 2021 by the authors. Licensee MDPI, Basel, Switzerland

Sharing more than friendship - nasal colonization with coagulase-positive staphylococci (CPS) and co-habitation aspects of dogs and their owners

Background Since the relationship between dogs and their owners has changed, and dogs moved from being working dogs to family members in post-industrial countries, we hypothesized that zoonotic transmission of opportunistic pathogens like coagulase positive staphylococci (CPS) is likely between dogs and their owners. Methodology/Principal Findings CPS- nasal carriage, different aspects of human-to-dog relationship as well as potential interspecies transmission risk factors were investigated by offering nasal swabs and a questionnaire to dog owners (108) and their dogs (108) at a dog show in 2009. S. aureus was found in swabs of 20 (18.5%) humans and two dogs (1.8%), and spa types which correspond to well known human S. aureus lineages dominated (e.g. CC45, CC30 and CC22). Multilocus sequence typing (MLST) of the two canine strains revealed ST72 and ST2065 (single locus variant of ST34). Fifteen dogs (13.9%) and six owners (5.6%) harboured S. pseudintermedius, including one mecA-positive human isolate (MRSP). Pulsed field gel electrophoresis (PFGE) revealed that one dog/owner pair harboured indistinguishable S. pseudintermedius- isolates of ST33. Ten (48%) of the 21 S. pseudintermedius-isolates showed resistance towards more than one antimicrobial class. 88.9% of the dog owners reported to allow at least one dog into the house, 68.5% allow the dog(s) to rest on the sofa, 39.8% allow their dogs to come onto the bed, 93.5% let them lick their hands and 52.8% let them lick their face. Bivariate analysis of putative risk factors revealed that dog owners who keep more than two dogs have a significantly higher chance of being colonized with S. pseudintermedius than those who keep 1–2 dogs (p<0.05). Conclusions/Recommendations In conclusion, CPS transmission between dog owners and their dogs is possible. Further investigation regarding interspecies transmission and the diverse adaptive pathways influencing the epidemiology of CPS (including MRSA and MRSP) in different hosts is needed

High-Zinc Supplementation of Weaned Piglets Affects Frequencies of Virulence and Bacteriocin Associated Genes Among Intestinal Escherichia coli Populations

To prevent economic losses due to post-weaning diarrhea (PWD) in industrial pig production, zinc (Zn) feed additives have been widely used, especially since awareness has risen that the regular application of antibiotics promotes buildup of antimicrobial resistance in both commensal and pathogenic bacteria. In a previous study on 179 Escherichia coli collected from piglets sacrificed at the end of a Zn feeding trial, including isolates obtained from animals of a high-zinc fed group (HZG) and a corresponding control group (CG), we found that the isolate collection exhibited three different levels of tolerance toward zinc, i.e., the minimal inhibitory concentration (MIC) detected was 128, followed by 256 and 512 mu g/ml ZnCl2. We further provided evidence that enhanced zinc tolerance in porcine intestinal E. coli populations is clearly linked to excessive zinc feeding. Here we provide insights about the genomic make-up and phylogenetic background of these 179 E. coli genomes. Bayesian analysis of the population structure (BAPS) revealed a lack of association between the actual zinc tolerance level and a particular phylogenetic E. coli cluster or even branch for both, isolates belonging to the HZG and CG. In addition, detection rates for genes and operons associated with virulence (VAG) and bacteriocins (BAG) were lower in isolates originating from the HZG (41 vs. 65% and 22 vs. 35%, p < 0.001 and p = 0.002, resp.). Strikingly, E. coli harboring genes defining distinct pathotypes associated with intestinal disease, i.e., enterotoxigenic, enteropathogenic, and Shiga toxin-producing E. coli (ETEC, EPEC, and STEC) constituted 1% of the isolates belonging to the HZG but 14% of those from the CG. Notably, these pathotypes were positively associated with enhanced zinc tolerance (512 mu g/ml ZnCl2 MIC, p < 0.001). Taken together, zinc excess seems to influence carriage rates of VAGs and BAGs in porcine intestinal E. coli populations, and high-zinc feeding is negatively correlated with enteral pathotype occurrences, which might explain earlier observations concerning the relative increase of Enterobacterales considering the overall intestinal microbiota of piglets during zinc feeding trials while PWD rates have decreased

Frequency, Local Dynamics, and Genomic Characteristics of ESBL-Producing Escherichia coli Isolated From Specimens of Hospitalized Horses

Previous research identified veterinary clinics as hotspots with respect to accumulation and spread of multidrug resistant extended-spectrum β-lactamase (ESBL)-producing Escherichia coli (EC). Therefore, promoting the prudent use of antibiotics to decrease selective pressure in that particular clinical environment is preferable to enhance biosecurity for animal patients and hospital staff. Accordingly, this study comparatively investigated the impact of two distinct perioperative antibiotic prophylaxis (PAP) regimens (short-term versus prolonged) on ESBL-EC carriage of horses subjected to colic surgery. While all horses received a combination of penicillin/gentamicin (P/G) as PAP, they were assigned to either the “single-shot group” (SSG) or the conventional “5-day group” (5DG). Fecal samples collected on arrival (t0), on the 3rd (t1) and on the 10th day after surgery (t2) were screened for ESBL-EC. All isolates were further investigated using whole genome sequences. In total, 81 of 98 horses met the inclusion criteria for this study. ESBL-EC identified in samples available at t0, t1 and t2 were 4.8% (SSG) and 9.7% (5DG), 37% (SSG) and 47.2% (5DG) as well as 55.6% (SSG) and 56.8% (5DG), respectively. Regardless of the P/G PAP regimen, horses were 9.12 times (95% CI 2.79–29.7) more likely to carry ESBL-EC at t1 compared to t0 (p < 0.001) and 15.64 times (95% CI 4.57–53.55) more likely to carry ESBL-EC at t2 compared to t0 (p < 0.001). ESBL-EC belonging to sequence type (ST) 10, ST86, ST641, and ST410 were the most prevalent lineages, with blaCTX–M–1 (60%) being the dominant ESBL gene. A close spatio-temporal relationship between isolates sharing a particular ST was revealed by genome analysis, strongly indicating local spread. Consequently, hospitalization itself has a strong impact on ESBL-EC isolation rates in horses, possibly masking differences between distinct PAP regimens. The results of this study reveal accumulation and spread of multi-drug resistant ESBL-EC among horses subjected to colic surgery with different P/G PAP regimens, challenging the local hygiene management system and work-place safety of veterinary staff. Moreover, the predominance of particular ESBL-EC lineages in clinics providing health care for horses needs further investigation.Peer Reviewe

Silence as a way of niche adaptation: mecC-MRSA with variations in the accessory gene regulator (agr) functionality express kaleidoscopic phenotypes

Functionality of the accessory gene regulator (agr) quorum sensing system is an important factor promoting either acute or chronic infections by the notorious opportunistic human and veterinary pathogen Staphylococcus aureus. Spontaneous alterations of the agr system are known to frequently occur in human healthcare-associated S. aureus lineages. However, data on agr integrity and function are sparse regarding other major clonal lineages. Here we report on the agr system functionality and activity level in mecC-carrying methicillin resistant S. aureus (MRSA) of various animal origins (n = 33) obtained in Europe as well as in closely related human isolates (n = 12). Whole genome analysis assigned all isolates to four clonal complexes (CC) with distinct agr types (CC599 agr I, CC49 agr II, CC130 agr III and CC1943 agr IV). Agr functionality was assessed by a combination of phenotypic assays and proteome analysis. In each CC, isolates with varying agr activity levels were detected, including the presence of completely non-functional variants. Genomic comparison of the agr I–IV encoding regions associated these phenotypic differences with variations in the agrA and agrC genes. The genomic changes were detected independently in divergent lineages, suggesting that agr variation might foster viability and adaptation of emerging MRSA lineages to distinct ecological niches.Peer Reviewe