Mobilization of transfer of the resistance to imipenem and fluoroquinolones in bacterial strains from a large regional Hospital
Mobilizácia prenosu rezistencie na imipenem a fluorochinolóny v baktériových kmeňoch z veľkej oblastnej nemocnice
Marta BABÁLOVÁ1, Jana Blahová1, Kvetoslava Králiková1, Vladimír Krčméry1, Sr., Petr Ježek2
(1Dept. of Chemotherapy, Slovak University of Medicine, Bratislava, Slovak Republic and 2Regional Hospital Příbram, Dept. of Clinical Microbiology, Czech Republic)
Summary
Background: Transfer of resistance to imipenem and/or to fluoroquinolones from resistant bacterial strains to susceptible bacteria can decrease their value as effective reserve antibiotics. Therefore, it is important to monitor the incidence of transferable resistance to these drugs in nosocomial isolates of severely ill patients hospitalized in clinical settings.
Aim of study: To demonstrate the transferability of multi-resistant bacteria to cephalosporin antibiotics (in strains producing ESBL) and resistant to imipenem and/or fluoroquinolones. To study also the process of mobilization for transfer of these antibacterials by other transferable genetic determinants, e. g. by genes for ESBL.
Methods: We used mixed cultures of multi-resistant wild-type donor strains with rifampicin-resistant but otherwise susceptible recipient strain of E. coli K-12. Transconjugant clones were selected on bi-antibiotic media (rifampicin plus an antibiotic in the spectrum of resistance of the donor strain) and were tested for the presence of all other resistance determinant present in the spectrum of the donor strain.
Results: In one strain of Enterobacter the resistance to imipenem and ofloxacin was mobilized by the transfer of genes coding for ESBL. A strain of Providencia was mobilized for transfer of resistance to fluoroquinolones by use of two donor strains.
Conclusion: Our previous observation of mobilization of transfers to fluoroquinolones by genes coding for the production of ESBL was confirmed in strains from patients of another large Regional Hospital and was extended by the demonstration of mobilization also of resistance to imipenem.
Key words: Antibiotic multi-resistance – transfer of antibiotic resistance – mobilization of genes for resistance to imipenem and fluoroquinolones.
Lek Obz, 60, 2011, 7-8, p. 284-286.
Súhrn
Východisko: Prenos rezistencie na imipeném a/alebo fluorochinolóny z rezistentných baktériových kmeňov na citlivé baktérie môže znižovať ich hodnotu ako účinných rezervných antibiotík. Je preto dôležité monitorovať výskyt prenosnej rezistencie na tieto lieky u nozokomiálnych izolátov od ťažko chorých pacientov, hospitalizovaných v klinických podmienkach.
Cieľ práce: Dokázať možnosť prenosu rezistencie od baktérií s multirezistenciou na cefalosporínové antibiotiká (u kmeňov produkujúcich ESBL) a rezistentných na imipeném a/alebo fluorochinolóny. Študovať tiež procesy mobilizácie transferu týchto antibaktériových liekov inými transferabilnými genetickými determinantami, t.j. génmi pre ESBL.
Metódy: Použili sme zmiešané kultúry multirezistentných divokých donorských kmeňov s kmeňmi rezistentnými rifampicín, ale inak vnímavými recipientnými kmeňmi E. coli K-12. Transkonjugantné klony boli vyselektovaní na biantibiotických médiách (rifampicín + antibiotikum zo spektra rezistencie donorového kmeňa) a boli vyšetrované na prítomnosť iných determinantných rezistencií v spektre donorského kmeňa.
Výsledky: U jedného kmeňa Enterobacter bola prenesená rezistencia na imipeném a ofloxacín transferom génmi rezistencie na fluorochinolóny s použitím dvoch donatorských kmeňov.
Záver: Naše predchádzajúce pozorovania mobilizácie transferu rezistencie na fluorochinolóny génmi kódujúcimi tvorbu ESBL sme potvrdili u kmeňov od pacientov z inej veľkej oblastnej nemocnice a rozšírili sme ju aj dôkazom prenosu rezistencie na imipeném.
Kľúčové slová: multirezistencia na antibiotiká – prenos rezistencie na antibiotiká – mobilizácia génov rezistencie na imipeném a fluorochinolóny.
Lek Obz, 60, 2011, č. 7-8, s. 284 – 286.
In the recent two decades an unexpectedly intensive increase of the emergence of nosocomial bacteria resistant to imipenem and to fluoroquinolone chemotherapeutics is recorded worldwide (2). In the eighties of the last century we identified first nosocomial strains which demonstrate the transfer of the resistance to cefotaxime and other higher-generation cephalosporins (3) which was later designated as the transfer of genes for so-called ESBL (Extended-Spectrum Beta-Lactamase) (2). Moreover, in recent years, new transferable genes of resistance to imipenem and meropenem were identified in many countries of the world, e. g. genes for KPC (Klebsiella pneumoniae Carbapenemase), special oxacillinases (OXA) and, quite recently, the so-called New Delhi Carbapenemases (2). Their transferability, however, was not always demonstrated. Similarly, the transferability of genes coding for resistance of bacteria to fluoroquinolones was not always tested although it was demonstrated that it is mobilized and co-transferred with genes for ESBL (1).
In this communication we present results of direct transfer and of the mobilization of transfer of resistance to imipenem and to fluoroquinolones by the transferability of genes which code the resistance of the ESBL type in a strain of Enterobacter cloacae from a group of nosocomial bacteria isolated from patients hospitalized in clinical settings of a large Regional Hospital in Příbram (Czech Republic). In addition, we demonstrate the mobilization of resistance to fluoroquinolones in an additional strain of Providencia stuartii from the same hospital.
Material and methods
Characterization of some properties of tested strains with a multiple drug resistance including the resistance to cephalosporins (producing ESBL), to imipenem and fluoroquinolones is presented in Tables 1 and 2. Methods of the resistance transfer in the mixed cultures of these donor strains with recipient strain E. coli K-12 No. 3110 rif+ (in one strain also with Proteus mirabilis P-38 rif+, see Table 2) are described in our previous publications (1, 3). Transconjugant clones of recipient strains, which accepted the resistance to any antibiotic, were tested for the presence of the total spectrum of antibiotic resistance determinants transferred, by the method of indirect selection, i. e. by testing the spectrum of resistance determinants present in any type of transconjugant clones isolated on bi-antibiotic plate used for direct primary selection (1, 3).
Results
Transfer of resistance to high-generation cephalosporins (of genes coding ESBL), to imipenem and to fluoroquinolones
In Table 1 we present a review of determinants of antibiotic resistance transferred from four nosocomial bacterial strains. Three of them transfer genes coding for ESBL, i. e. resistance to cefotaxime, ceftazidime and cefepime. Two strains are resistant to imipenem and fluoroquinolones. This corresponds to the experience of other authors (2). One strain (Enterobacter cloacae) demonstrated, in tests with indirect selection, the mobilization of the transfer of resistance to both of these antibacterials.
In Table 2 we present results of mobilization of the transfer of resistance to fluoroquinolones mobilized by the transfer of genes for ESBL. However, to demonstrate the concomitant transfer of fluoroquinolone resistance, it was necessary to use transfer experiment to two recipient strains.
Discussion
Our earlier results from another University Hospital in Zlín (1) and present results from the Regional Hospital in Příbram demonstrate that, also in our geographical area, first signs appear of the process of mobilization of genes which code the transmissible resistance to imipenem and fluoroquinolones. The nosocomial strain of Enterobacter cloacae No. 2458 contains genes of transferable resistance to these substances (table 1) which can be mobilized for conjugal transfer. Another strain from this series, Providencia stuartii No. 2264, carries genes coding the resistance to fluoroquinolones. These can be mobilized for transfer by ESBL genes coding for transferable cefotaximase (table 2). Therefore, it is advisable to perform intensive investigation to demonstrate the occurrence of emergence of genes coding the resistance to imipenem, meropenem and the fluoroquinolones, of their mobilisability and/or direct transferability. Consequently, it is strongly advisable to follow, in the practical use of these reserve and indispensable antibacterial substances, all rules for their rational application for prevention and/or therapy of severe infective diseases of patients hospitalized in clinical settings and to maintain, as long as possible their preventive and therapeutical potency and value (2, 3).
Conclusion
In two nosocomial strains of bacteria, i. e. in the strain of Enterobacter spp. and Providencia stuartii, genes for resistance to fluoroquinolones were mobilisable by co-transferability of genes coding for broad spectrum ESBL. In addition, in the same strain of Enterobacter, also the gene coding for resistance to imipenem was mobilized as well. Nevertheless, the demonstration of co-transfer of genes to these drugs – to imipenem and/or fluoroquinolones, required the use of extended methods, i. e. the use of indirect selection procedure, and, in some cases, also the use of more than one recipient strain. This first demonstration of the mobilization of imipenem resistance presents a signal to use all extensive methods to identify strains of nosocomial bacteria which are able to disseminate genes for these resistances to other bacteria in a given clinical setting.
References
1. Babálová, M., Bartoníková, N., Blahová, J., Králiková, K., Krčméry, V., Menkyna, R., Rovný, I.: Mobilization of transfer of resistance to fluoroquinolones in nosocomial strain of Klebsiella pneumoniae. Lek Obz, 58, 2009, p. 288-290.
2. Jacoby, G.A., Munoz-Price, L.S.: Mechanisms of disease. N Engl J Med, 352, 2005, p. 380-390.
3. Knothe, H., Shah, P., KrČméry, V., Mitsuhashi, S.: Transferable resistance to cefotaxime, cefamandole and cefuroxime in nosocomial Klebsiella pneumoniae and Serratia marcescens. Infection, 11, 1983, p. 315-318.
