Untersuchungen zum Vorkommen von Carbapenemase-produzierenden Enterobacteriaceae bei Tieren und zum Einfluss von Resistenzplasmiden auf die bakterielle Fitness
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Beschreibung
Carbapenemase-producing Enterobacteriaceae pose a serious threat for treatment of bacterial infections. Particularly nosocomial infections with these pathogens have occured more frequently over the last decades. To gain an overview of incidence of multiresistant Enterobacteriaceae, screening studies are essential.
Between June 2012 and December 2016, 19,025 E. coli, 1,607 Klebsiella spp. and 570 Enterobacter spp. were examined for carbapenem-non-susceptibility. Additionally, 367 archived ESBL /AmpC β Lactamase-producing Enterobacteriaceae were tested. Samples originated from swine (n = 10,899), cattle (n = 1,889), small ruminants (n = 246), birds (n=132), dogs (n=3,775), cats (n = 932), horses (n = 2,573), pet animals and rodents (n = 428), zoo and wildlife animals (n = 644) and others (n = 51). The sample material originated from about 1,500 different veterinary clinics from different regions throughout Germany (external clinics), as well as from the clinics for horses, ruminants, pigs and small animals and from the Institute of Veterinary Pathology of the JLU Giessen (internal clinics). Phenotypical Carbapenem-non-susceptible isolates were tested by PCR for blaNDM like, blaVIM like, blaKPC-like and blaOXA-48 like and in a positive case also for ESBL and AmpC β laktamases blaCTX M like, blaSHV like, blaTEM like, blaOXA like, blaCMY like, blaDHA like, blaACC like and blaFOX like.
OXA 48 like carbapenemases OXA 48 and OXA 181 were detected in 137 and 2 isolates, respectively.
BlaOXA-48 was located on an approximately 60¬ kb IncL-plasmid in all cases. These plasmids exhibited a high similarity of up to 100 % to published sequences of human OXA 48 plasmids. OXA-48-plasmids were only discovered in isolates of small animal origin but not in livestock.
K. pneumoniae was the most prevalent OXA-48-producer (n=86; 6.6 %), followed by E. cloacae (n=28; 5 %), K. oxytoca (n=1; 0.3 %) and E. coli (n=22; 0.1 %).
Predominant STs for OXA 48-positive isolates proved to be ST11 and ST15 for K. pneumoniae, ST506 and ST78 for E. cloacae and ST1196 for E. coli.
The minority (n = 20) of OXA 48 isolates originated from external veterinary practices. High detection rates in the sample material from internal clinics, similarity of plasmids size and replicontype, STs and results of macrorestriction analysis suggest high clonality and nosocomial events of according isolates. Size and replicontype of OXA-48-plasmids and in vitro conjugation experiments hypothesize plasmid-transfer between different spezies and STs. Repeated detection of isolates with identical macrorestriction profiles over long periods of up to four years (K. pneumoniae, ST15) might indicate persistence in clinic ambience, however, repeated external entries cannot be ruled out.
OXA 181 carrying E. coli were obtained from two different pigs from an Italian livestock farm. MLST revealed ST359 and ST641. One of the OXA 181-positive isolates was also positive for colistin resistance MCR 1 and methyltransferase gene armA. Moreover, both OXA-181-plasmids harboured quinolone-resistance gene qnrS1. BlaOXA 181 was located on an approximately 50 kb non-conjugative IncX3-plasmid, mcr 1 on an approximately 30 kb IncX4-plasmid. The two OXA 181 plasmids revealed up to 100 % sequence identity to human OXA 181 IncX3-plasmids, but this is the first report about OXA 181 in pig livestock. The detected IncX4-plasmid revealed sequence-homology of 99,97 % to already published IncX-4-plasmids. This is also the first report about the combination of carbapenemase gene blaOXA 181 and colistin-resistance gene mcr 1 in a sole bacterium.
In supplementary studies concerning the influence of the OXA-48 plasmid on biofilm formation, no statement could be made about a uniform effect of the resistance plasmid on the ability to form biofilms. This suggests very complex mechanisms of biofilm formation.
No statistically significant effect of the OXA-48 plasmid on the mortality of wax moth larvae could be determined in this study. In summary, the lethality of wax moth larvae infected with isolates with or without resistance plasmid was in the same range.
This study provided an overview regarding the spread of carbapenemase-producing Enterobacteriaceae in animals in Germany and supplied information on the nosocomial spread of different species and sequence types exhibiting an OXA-48 plasmid of equal size and identical replicon type in a veterinary clinic. Surveillance studies are of great importance for the targeted control of veterinary hospital-associated infectious events, analog to human medicine. Knowledge of the molecular epidemiology of carbapenemase-producing bacteria and their resistance plasmids is an essential prerequisite for the implementation or optimization of preventive hygiene measures in veterinary clinics. It was shown that carbapenemase producers from veterinary and human medicine have essential properties in common. This illustrates again that the global antibiotic resistance problem can only be fought with a "one health" approach.
Autor*in
Sandra Pulss