Publikationsdatenbank

Comparative genotypic characterization of Methicillin-resistant and- susceptible Staphylococcus pseudintermedius of feline and canine origin in Germany (2018)

Art

Hochschulschrift

Autor

Abou-Elnaga, Yassmin Sayed (WE 7)

Quelle

Berlin: Mensch und Buch Verlag, 2018 — vi, 92 Seiten

ISBN: 978-3-86387-868-9

Sprache

Englisch

Verweise

URL (Volltext): https://refubium.fu-berlin.de/handle/fub188/4021

Kontakt

Institut für Mikrobiologie und Tierseuchen

Robert-von-Ostertag-Str. 7-13
14163 Berlin
+49 30 838 51843 / 66949
mikrobiologie@vetmed.fu-berlin.de

Abstract / Zusammenfassung

Staphylococcus pseudintermedius, a member of the Staphylococcus intermedius- group, is known as a common colonizer of canine skin and mucosa, occasionally detected in specimens of other animal species and humans as well. Being a representative of a typical opportunistic pathogen, S. pseudintermedius is often associated with a wide variety of purulent or toxin-associated infectiouse diseases in animals as well as occasionally in humans. Despite increasing reports concerning the occurence of S. pseudintermedius, including its methicillin resistant variant (MRSP), in recent years, knowledge about the occurrence and distribution of genotypes together with important toxins in specimens from diseased dogs, cats and horses in Germany is scarce. MRSP are often associated with a multi-drug resistant phenotype, limiting effective antibiotic therapy options in veterinary medicine. In some cases, animals have to be put down due to reasons of animal welfare. The aim of this study was to investigate the genetic background and relationships among a predefined set of 220 S. pseudintermedius isolates representing different host origins (dog, cat, horse), various infected sites (e.g. surgical site infection (SSI), wound, otitis, skin and skin-associated structures) including methicillin- resistant (n=107) and -susceptible (n=113) variants. Genotypic characterization was performed by conducting pulsed-field gel electrophoresis (PFGE) for all S. pseudintermedius as well as multi-locus sequence typing (MLST) for 53 methicillin-susceptible (MSSP) and 55 methicillinresistant S. pseudintermedius (MRSP). In addition, the occurrence and distribution of important virulence factors such as exfoliative toxins (ExpA, ExpB) and leukotoxin (LukI) among the isolate collection was determined by PCR detection of the respective encoding genes and subsequently analyzed with respect to different genetic lineages. All investigated MSSP and MRSP yielded a positive PCR-result for lukI. Furthermore, expA was detected in 18/113 of MSSP (15.9%), but not among MRSP. In addition, expB was identified in 23/113 of MSSP (20.4%) and 1/107 of MRSP (0.9%), respectively. With regard to the sample site origin distribution, MSSP isolates obtained from either “skin” or “skin-associated structures” were with 16% (expA) and 12% (expB) equal or even below the overall average. Interestingly, MSSP isolated from wound swabs yielded positive PCR signals above the overall average, 30.8% for expA and 46.2% for expB. The putative impact of these toxins during development of wound infections might be an interesting aspect and should be further investigated in functional studies. In total, 219 of 220 S. pseudintermedius were typeable using the PFGE technique. Subsequent PFGE analysis and dendrogramm construction was carried out with Bionumerics 7.5 (Applied Maths, Belgium) using the Unweighted Pair Group Method with Arithmetic mean (UPGMA) employing an 80% cut-off for cluster dedication. In total, 20 distinct clusters as well as three singletons were assigned. Pattern of MSSP isolates clustered within 19 of the 20 clades and were associated with two of the three singletons described in this work. However, some MSSP patterns associated with isolates obtained from different animal species originating from different federal states seem to be closely related. This finding might indicate spread of various genetic lineages across large geographic regions. A putative explanation for this observation might be the mobility of the dog owners (e.g. holidays, relocation, dog shows etc.). Interestingly, the PFGE pattern of MRSP showed a remarkable diversity, an observation which has been published in different studies from other countries as well. Several MRSP revealed identical patterns, although these isolates originated from distinct animal patients living in different federal states. MLST analysis revealed 50 novel sequence types (ST) associated with the MSSP and one sequence type (ST370) that has been reported in a previous study. In contrast, the predominant genotype assigned to 48 of 55 MRSP isolates obtained from various German regions, animals and infected sites determined in this study was ST71. PFGE analysis revealed that the majority of MRSP investigated by MLST (39 of 55) clustered within the largest clade (clade 8). However, further PFGE patterns associated with MRSP_ST71 clustered within other clades as well. The apparent incongruence of MLST and PFGE data for S. pseudintermedius, especially for MRSP_ST71, has previously been described in other studies as well. The use of an in silico restriction analysis based on whole genome data might elucidate DNA sequence modifications of the SmaI restriction sites possibly responsible for this discrepancy between results of MLST and PFGE analysis. In addition, the MLST scheme currently used for S. pseudintermedius might lack discriminatory power. At present, the MLST database includes more than 600 different data base entries. However, for the gene tuf only 12 variants have so far been identified. Although ST71 is the predominant genetic lineage for MRSP investigated in this study, a diversification of MRSP sequence types was observed as well, consistent with recent publications. In addition, two novel MRSP genotypes (ST461 and ST525) were identified during this work. Furthermore, ST258 – an emerging genetic lineage identified in Northern Europe - was also detected in the present MRSP collection. This current evolvement seems to be similar to the evolution of methicillin-resistant S. aureus (MRSA) in the past, where several different genetic lineages seem to be capable of aquiring and integrating the mobile genetic element(s) harboring the methicillin resistance encoding gene. The future will show, whether MRSP infections will remain largely restricted to veterinary medicine or if serious infections in humans will occur more frequently.