Abstract
Background: Proteus mirabilis is an opportunistic pathogen, commonly associated with complicated urinary tract infections (UTIs). UTIs caused by multidrug-resistant Proteus mirabilis have increased worldwide. Multidrug-resistance of Gram-negative enteric bacteria is usually associated with class 1 integrons.Purposes: To investigate the prevalence and characterize gene cassettes of class 1 integrons in multidrug-resistant P. mirabilis Methods: From 2006 to 2008, 314 P. mirabilis isolates from urine were collected from a regional teaching hospital. Antimicrobial resistance of the isolates was determined by disk diffusion methods. The phenotypic confirmatory test of extended-spectrum β-lactamase (ESBL) production was performed as described in the Clinical and Laboratory Standards Institute (CLSI) guideline. The genetic organization of the class 1 integron cassettes was investigated by PCR, cloning, and sequencing of the regions surrounding these genes.Results: Seventy-nine (25%, 79/314) P. mirabilis isolates were ESBL-producing and most ESBL-producing P. mirabilis were positive for blaCTX-M. Class 1 integrons were presented in 76 isolates (24.2%, 76/314), and were more frequently found in ESBL-positive (55/79, 70%) than ESBL-negative (21/235, 8.9%) P. mirabilis isolates. The most prevalence of the cassettes encoded resistance genes were aminoglycoside (aac(6’)-Ib, aacA7, aadAl, aadA2, and aadAla), trimethoprim (dfrAl and dfrA12) and chloramphenicol (catB3 and cmlA6). The most prevalent cassette of dfr12-orfF-aadA2 was found in 49 isolates. The cassette array aadB-catB3-oxa10-aadA1 was first found in P. mirabilis. The enterobacterial repetitive intergenic consensus (ERIC)-PCR fingerprinting patterns were detected in these 76 integron positive P. mirabilis isolates and belonged to 8 profiles.Conclusion: This study investigated the prevalence and characterized gene cassettes of class 1 integrons in MDR P. mirabilis isolates from urine samples. The frequency of gene cassettes in P. mirabilis were partially by clonal spread of the carriers and the results could provide information for effective antimicrobial therapy and infection control.
Highlights
The antimicrobial genes frequently located on plasmids, transposons and integrons, lead to the rapid dissemination and treatment problem
Class 1 integrons usually associated with multidrug-resistance due to their ability to incorporate or excise one or more antimicrobial resistance gene cassettes
By Polymerase chain reaction (PCR) and nucleotide sequencing, we detected the presence of only CTX-M-14 in 70 isolates, only CTX-M-3 in 2 isolates, Table 1 − Susceptibility testing results of 76 intl1-positive and 238 intl1-negative Proteus mirabilis isolates
Summary
The antimicrobial genes frequently located on plasmids, transposons and integrons, lead to the rapid dissemination and treatment problem. Class 1 integrons usually associated with multidrug-resistance due to their ability to incorporate or excise one or more antimicrobial resistance gene cassettes. These genes can be integrated in the form of cassettes by three key components: the int gene for recombination, the att site for primary recombination known as 59 base elements, and a promoter Pc that directs expression of the cassette-encoded genes [2]. The prevalence of integrons and characterized gene cassettes in Gram-negative bacteria integron-associated multidrug resistance have been investigated [12,13,14,15]; it is seldom addressed in P. mirabilis. A comparison of integron-carrying and non-integron-carrying MDR P. mirabilis isolated from urine was made to assess the differences in their antimicrobial susceptibility and clonal dissemination
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