Types Of Gene Cassette Arrays Research Articles

High incidence of multiple intI1 genomic gene cassettes in Aeromonas strains

Antimicrobial resistance profiles of Aeromonas have been used as an effective indicator for monitoring resistances in aquatic environments. Integron gene cassettes are a major reservoir of antibiotic resistance genes in bacteria. To date, little has been reported on the antimicrobial resistance or integrons of Aeromonas in bullfrog aquaculture. In this study, 27 isolates belonging to four Aeromonas species (A. hydrophila, A. veronii, A. caviae, and A. jandaei) were isolated from farmed diseased American bullfrogs (Rana catesbeiana). all of them were multidrug-resistant, exhibiting resistance to at least seven drugs from five antibiotic classes. Class 1 integrons (intI1s), containing nine types of gene cassette arrays encoding resistance to trimethoprim (dfrA1, dfrA12, dfrA15, dfrA17), streptomycin/spectinomycin (aadA2), fluoroquinolones/aminoglycosides (aac(6′)-Ib-cr), rifampin (arr3), proline-rich antimicrobial peptides (ptrB), and multiple antimicrobial agents involved in biofilm development (dgs), were detected in 26 (26/27, 96.3%) of the isolates. Seven patterns were identified, and six of them contained two or three gene cassettes, in 27 isolates. This work highlights unusually high frequency (21/27, 77.8%) of multiple intI1 gene cassette arrays and three novel intI1 gene cassettes or arrays (dgc, ptrB, and aac(6′)-Ib-cr-arr3) in the isolates of Aeromonas spp. from American bullfrogs.

Class 1 integrons in clinical and swine industry isolates of Salmonella Typhimurium from Colombia, dating 1997 to 2017.

Background. Salmonella enterica subsp. enterica serovar Typhimurium (S. Typhimurium) has been linked to outbreaks of foodborne gastroenteritis disease, and the emergence of antimicrobial-resistant clones. In Colombia, laboratory surveillance of Salmonella spp. between 1997-2018 revealed that S. Typhimurium was the most ubiquitous serovar (27.6 % of all Salmonella isolates), with increasing levels of resistance to several families of antibiotics.Hypothesis. Resistant isolates of S. Typhimurium recovered from human clinical, food and swine samples carry class 1 integrons that are linked to antimicrobial resistance genes.Aim. Identify class 1 integrons, and investigate their association with other mobile genetic elements, and their relationship to the antimicrobial resistance of Colombian S. Typhimurium isolates.Methods. In this study, 442 isolates of S. Typhimurium were analysed, of which 237 were obtained from blood culture, 151 from other clinical sources, 4 from non-clinical sources and 50 from swine samples. Class 1 integrons and plasmid incompatibility groups were analysed by PCR and whole-genome sequencing (WGS), and regions flanking integrons were identified by WGS. The phylogenetic relationship was established by multilocus sequence typing (MLST) and single-nucleotide polymorphism (SNP) distances for 30 clinical isolates.Results . Overall, 39 % (153/392) of the human clinical isolates and 22 % (11/50) of the swine S. Typhimurium isolates carried complete class 1 integrons. Twelve types of gene cassette arrays were identified, including dfr7-aac-bla OXA-2 (Int1-Col1), which was the most common one in human clinical isolates (75.2 %, 115/153). Human clinical and swine isolates that carried class 1 integrons were resistant to up to five and up to three antimicrobial families, respectively. The Int1-Col1 integron was most prevalent in stool isolates and was associated with Tn21. The most common plasmid incompatibility group was IncA/C.Conclusions. The widespread presence of the IntI1-Col1 integron in Colombia since 1997 was striking. A possible relationship between integrons, source and mobile elements that favour the spread of antimicrobial resistance determinants in Colombian S. Typhimurium was identified.

High Occurrence of Multiple-Drug Resistance Mediated by Integron in Aeromonas Isolated from Fish-Livestock Integrated Farms

Fish-livestock integrated farming is a traditional practice in South China and Southeast Asia. The administration of antimicrobial agents in livestock may potentially facilitate the spread of antimicrobial resistance to aquaculture through the drainage of livestock manure. Aeromonas spp. are fish pathogens that are the predominant bacteria in water bodies. The aim of this study was to characterize multiple-drug-resistantAeromonas spp. isolated from integrated and nonintegrated fish-livestock farms and to investigate the occurrence of class 1 integrons. Of the 481 Aeromonas strains examined in this study, isolates from pig manure, fish, and environmental samples from pig-fish or goose-fish integrated farms were significantly more resistant to various antimicrobial agents than those from nonintegrated farms P < 0.05 . High rates of resistance to nalidixic acid and sulfamonomethoxine were observed in the isolates from the integrated farm. Fifty Aeromonas isolates (10.4%) from integrated farms contained class 1 integrons. In addition, 96.0% (48/50) of the integron-positive strains displayed multiple-drug resistance. Ten types of gene cassette arrays were determined by sequencing, including dfrA17, dfrA12-orfF-aadA2, catB8, dfrB4-catB3-aadA1, aac6(6′)-Ib-cr-arr-3, aac-II-blaOXA-21-catB3, aar2-aacA4-drfA1-orfC, aac(6′)-Ib-cr, dfrA15, and dfrB4-catB3-blaOXA-10-aadA1. Notably, among the 50 integron-positive isolates, twenty isolates showed integrons located in plasmids, which may facilitate the transmission of resistance in integrated farms. Our investigation confirmed the high prevalence of multiple antimicrobial resistances mediated by class 1 integrons in Aeromonas isolates from integrated farms. Therefore, it is necessary to establish a risk assessment method for antimicrobial resistance in aquaculture.

Characterization of Integrons and Antimicrobial Resistance in Escherichia coli Sequence Type 131 Isolates.

Background Escherichia coli sequence type 131 (ST131) is an important multidrug-resistant extraintestinal pathogen, which can cause many kinds of infections. Integrons may play a crucial role in the dissemination of antibiotic resistance genes. The purpose of this study was to characterize the prevelance of integrons among E. coli ST131 strains in China. Methods Eighty-three E. coli ST131 strains in China. E. coli ST131 strains in China. Results Overall, 26.5% (22/83) of the E. coli ST131 strains in China. dfrA17-aadA5 and aac(6′)-Ib-cr-cmlA5. Only one type of Pc promoter variant was detected among 22 integron-positive isolates (PcW). In vivo transfer of integron was successful for 9 of integron-positive E. coli ST131 strains in China. E. coli ST131 strains in China. Conclusions Our study showed a low prevalence of integrons was detected in E. coli ST131. Continued surveillance of this mobile genetic element should be performed to study the evolution of antibiotic resistance among E. coli ST131.E. coli ST131 strains in China. E. coli ST131 strains in China.

Three Novel Class 1 Integrons Detected in Multidrug-Resistant Pseudomonas aeruginosa Hospital Strains

The antibacterial resistance of healthcare-associated infection (HAI) agents is a major public health problem worldwide. Pseudomonas aeruginosa is one of the main HAI agents, especially in intensive care units (ICUs). The present study focuses on the identification of antibacterial resistance genetic determinants and on determining the structure of mobile genetic elements—novel class 1 integrons of P. aeruginosa. P. aeruginosa strains (n = 105) were collected in the Department of the Moscow Neurosurgery ICU in 2013–2016 from the respiratory system (60.0%), urine (28.6%), surgical wounds (5.7%), blood (2.9%), and cerebrospinal fluid (2.9%). The majority (92.4%) of strains were characterized by a phenotype of multidrug-resistance. Beta-lactamase genes blaVIM-2-like, which are widely distributed in Russia, were identified in 37.7% of strains. The blaCTX-M-15 gene was carried by 3.0% of strains that is the first report of such gene identification in P. aeruginosa in Russia. Class 1 integrons were detected in 63.0% of strains, with 36.7% of strains carrying seven types of gene cassette arrays: (blaVIM-2-like), (aadA6-gcuD), (aacA7-blaVIM-2-like), (aac(3 ')Ic-cmlA5), (aadA6Δ3::ISPa21e-gcuD), (gcu87-aadB-aphA15d-aadA1a), and (blaPBL-1-aacA4). The latter three gene cassette arrays are new for class 1 integrons. Identification numbers have been assigned to novel integrons: In1379, In1360, and In1375. New genetic structures were described: the aadA6 gene cassette with inserted ISPa21уe element (In1379); the gsu87 gene cassette coding hypothetical protein which is not represented in the GenBank database (In1360); novel allele of aphA15d gene cassette and the blaPBL-1 gene cassette coding new, not previously described, beta-lactamase of class A (In1375). Identification of novel genetic structures of antibacterial resistance in P. aeruginosa strains isolated in the course of 3 years indicates the activity of genetic processes associated with antibiotic resistance in hospital pathogens in the Department of Neuro-ICU, which indicates the activity of genetic processes associated with the formation of multiple drug resistance of hospital pathogens.

Detection of common mobile genetic elements and genotyping of multidrug-resistant Gram-negative bacilli in blood specimens from septicemia patients in southern China.

BackgroundIntegron, ISCR1 and complex class 1 integrons lead bacteria to become resistant to antibiotic regimens. The aim of this study was to detect common mobile genetic elements of multidrug-resistant Gram-negative bacilli and evaluate the genotyping of these bacilli in blood specimens from septicemia patients in southern China.MethodsA total of 837 Gram-negative bacilli including 578 strains containing Enterobacteriaceae and 259 strains containing non-fermentative bacilli were investigated in blood samples collected from septicemia patients between 2011 and 2014 in southern China. Mobile genetic elements, such as class 1 integrons, the insertion sequence common region 1 (ISCR1), and complex class 1 integrons, were detected from the 837 strains.ResultsTwenty-seven types of gene cassette arrays were found among 837 strains in which 492 (58.8%) class 1 integron-positive isolates and 254 (51.6%) gene cassette-positive isolates were found, including the first description of two types, aacA4-blaIMP-1-blaOXA-30-catB3 and aac(6′)-II-aadA13-cmlA8-blaOXA-10, in the corresponding species and two gene cassettes, putative helicase and aadA-like, originally detected in integrons. Twelve types of ISCR1-linked resistance gene regions in 196 ISCR1-positive bacilli and seven different types of complex class 1 integron-positive strains were obtained including four distinct complex class 1 integrons that have never been described in any species. Enterobacterial repetitive intergenic consensus (ERIC)-PCR fngerprinting showed that isolates with identical gene profles were clonally unrelated.ConclusionOur results indicated that we should pay more attention to enhance the quality of infection control measures and prevent hospital infection, so as to avoid the outbreak of multidrug-resistant Gram-negative bacilli.

Genotypic Diversity of Multidrug Resistant Shigella species from Iran.

BackgroundIn many developing countries, shigellosis is endemic and also occurs in epidemics and treatment of multidrug-resistant (MDR) isolates are important. The aims of this study were to determine the antimicrobial susceptibility, prevalence of class 1 and 2 integrons and the clonal relatedness of isolates.Materials and MethodsAntimicrobial susceptibility tests were performed by disc diffusion method. Polymerase chain reaction (PCR)-sequencing technique was employed for detection and characterization of integrons. The genetic relatedness was evaluated by using enterobacterial repetitive intergenic consensus (ERIC) PCR.ResultsThere was a high percentage of resistance to trimethoprim-sulfamethoxazole (TMP/SMX) (93.7%), ampicillin (AMP) (87.3%), streptomycin (STR) (84.5%) and tetracycline (TET) (78.9%). Multidrug resistant phenotype was seen in 95.1% of total isolates. Most common MDR profile was TMP/SMX/STR/AMP resistant pattern. Among the 142 Shigella spp. analyzed in this study, 28 isolates were positive for class 1 integron with two types of gene cassette arrays (dfrA17/aadA5 = 31.7% and dfrA7 = 3.8%). The class 2 integron was more frequently detected among the isolates (94.7%) with dfrA1/sat1/aadA1 (69.4%) and dfrA1/sat1 (30.6%) gene cassettes. ERIC-PCR results showed 6, 5, 4 and 3 main genotypes among S. flexneri, S. sonnei, S. boydii and S. dysenteriae isolates, respectively.ConclusionsOur findings revealed that multidrug resistant Shigella species with high prevalence of class 2 integron were very common in Iran. In addition, ERIC-PCR patterns showed limited variety of clones are responsible for shigellosis in the region of the study.

Integron types, gene cassettes and antimicrobial resistance profile of Acinetobacter baumannii isolated from BAL samples in Babol, north of Iran

Multi-drug resistant isolates of Acinetobacter baumannii have created therapeutic problems worldwide. This current study was intended to determine the Integron types, gene cassettes and antimicrobial resistance profile of A.baumannii isolated from BAL samples in Babol, north of Iran. During a 15-month period, 35 A.baumannii isolates were studied. Different classes of antimicrobial agents were used to determine the resistance ratios. Multiplex-PCR was used to detect different types of integrons and associated gene cassettes. The resistance rates to GM, FEP, AK, TOB, CP, PIP, SAM, IPM, SXT, CTX, CAZ, CL, TIM, MEM, and TZP were 85.7%, 100%, 91.4%, 68.5%, 94.3%, 88.5%, 97.1%, 94.3%, 100%, 100%, 100%, 0.0%, 91.4%, 94.3% and 91.4%, respectively. The distribution analysis of int genes showed that 25.7%, 88.6% and 28.6% of isolates carried the intI, intII and intIII genes, respectively. The prevalence of aadB, dfrA1, bla-OXA30 and aadA1 genes were 94.3%, 77.1%, 40% and 5.7%, respectively. The current study showed that a high level of A.baumannii isolates harbor integrons in our therapeutic center, which may lead to distribution of multiple antimicrobial resistance. The different types of gene cassette arrays in the present study highlight the important role of geographical features in MDR isolates dissemination which could be credited to different profiles of drug consumption in different areas. The findings emphasized that the need for continuous surveillance to prevent distribution of multidrug resistance among A.baumannii strains in Iran.

Characterization of integrons and novel cassette arrays in bacteria from clinical isloates in China, 2000-2014.

Rapid dissemination of antibiotic resistance genes among bacterial isolates is an increasing problem in China. Integron, a conserved DNA sequence, which is carried on episomal genetic structures, plays a very important role in development of antibiotic resistance. This systematic analysis was based on MEDLINE and EMBASE databases. We summarized the distribution and proportion of different types of gene cassette arrays of integrons (including class 1, 2, 3 and atypical class 1 integron) from clinical bacteria isolates in China. Fifty-six literatures were included in this study. Most of the strains were Gram-negative bacteria (94.1%, 7,364/7,822) while only 5.9% strains were Gram-positive bacteria. Class 1 integrons were detected in 54.2% (3956/7295) Gram-negative strains. aadA2 was the most popular gene cassette array detected from 60 Gram-positive bacteria while dfrA17-aadA5 were detected in 426 Gram-negative bacteria. This study identified 12 novel gene cassette arrays which have not been previously found in any species. All the novel gene cassette arrays were detected from Gram-negative bacteria. A regional characteristic of distribution of integrons was presented in this study. The results highlight a need for continuous surveillance of integrons and provide a guide for future research on integron-mediated bacteria resistance.

Clonal dissemination of a single Shigella sonnei strain among Iranian children during Fall 2012 in Tehran, I.R. Iran

Shigella species are a common cause of bacterial diarrhea worldwide and the disease is characterized by seasonality. Shigella has been encountered by widespread resistance to commonly used antibiotics which is a serious concern. The aim of this study was to analyze the epidemiological relatedness of Shigella strains isolated from children during one year period by PFGE method and to investigate antimicrobial resistance determinants and cassettes among Shigella species. The occurrence of Shigella spp. in the present study was 1.32% during the study period and the majority of cases (56 (80%)) were occurred during autumn while Shigella sonnei was the most prevalent species identified. Multi-drug resistance phenotype was seen in 98.5% of total isolates with SXTr/TEr/TMPr resistance pattern. Among the 70 Shigella spp. analyzed in this study, 16 isolates were positive for class I integron (int1+) with two types of gene cassette arrays (dfrA17/aadA5 and dfrA7).The class 2 integron was more frequently detected among the isolates (85.71%) with dfrA1/sat1/aadA1 (10%) and dfrA1/sat1 (75.71%) gene cassettes. The tetA and tetB determinants were observed in 75.7% and 21.42% of Shigella isolates and tet(A) was the foremost in S. sonnei and Shigella flexneri population. In this study 5 tetracycline resistant isolates had no tetracycline resistance gene (A–D) and no association was recognized between the value of MIC against tetracycline and the tet genes content of isolates. Fifty three of total Shigella isolates (75.7%) showed an identical PFGE patterns. Seven PFGE clusters observed in our study were composed of members with one to three band variations, which is indicative of closely related isolates. The major cluster (cluster C) constituted 75.7% of total isolates, all of which (except eight isolates) consonantly showed identical class 2 integron of 1500bp which strongly suggests the dissemination of a single S. sonnei clone among the pediatric population in 2012 autumn in Tehran, Iran, in comparison with the equal data from the comparable time period from recent years.

Distribution and molecular profiling of class 1 integrons in MDR Acinetobacter baumannii isolates and whole genome-based analysis of antibiotic resistance mechanisms in a representative strain

The class 1 integron is an important driver of the nosocomial dissemination of multidrug-resistant (MDR) bacteria, such as Acinetobacters. In this study, we characterized the gene cassette arrays of class 1 integrons in Acinetobacter baumannii, where the detailed structure of these integrons for 38 clinical strains was analyzed. The results showed that there are three types of gene cassette arrays that are carried by different class 1 integrons, among them the aac(6′)-IId-catB8-aadA1 array was the most prevalent. For detailed analysis of the integron structure, whole genome sequencing was carried out on strain AB16, and it was found that a single integron on its chromosome has a partial Tn21 transposon in its 5′ flanking region and two complete copies of the insertion element IS26 in both the 5′ and 3′ flanking regions, indicating that the integron could be acquired by horizontal gene transfer. Furthermore, there is one resistance island AbaR22, one bla gene containing a transposon, four intrinsic resistant genes and one efflux pump that together confer six types of antibiotic resistance.

Detection and characterization of class 1 integron-associated gene cassettes from Pseudomonas aeruginosa isolates in southern Taiwan

In this study, detection and characterization of class 1 integron-associated gene cassettes from Pseudomonas aeruginosa isolates in southern Taiwan were investigated. The study focused on the association between integron-associated resistance gene cassettes and multidrug resistance in P. aeruginosa isolates. Using polymerase chain reaction amplification, DNA sequencing, and basic local alignment search tool analysis, a total of 22 different types of gene cassette arrays were detected in 162 class 1 integron-positive P. aeruginosa isolates. We first identified 11 different types of new gene cassette arrays within class 1 integron in P. aeruginosa isolates, including aac(6′)-II-catB2-aadA2, aac(6′)-II-aadA2, aac(6′)-II-catB2, aacA4-aadA15, aacC1-orfA-orfB-aadA1, cm1A-aadA1, catB3-blaOxA-10-aadA15, aacA4-catB8-aadA1, aadB-orfF1-aadA11, dfrB1, and dfrB4a-aacA4-aacA4-aadA1. Of these, aac(6′)-II-catB2-aadA2 was the most frequently found gene cassette. Twenty-one (21/162, 12.9%) strains carrying two different types of gene cassette arrays of catB3-blaOxA-10-aadA15 and aac(6′)-II-catB2-aadA2 were also simultaneously present in the P. aeruginosa isolates. A novel dfrB4a gene, different from the dfrB4 gene detected in the gene cassette array of dfrB4a-aacA4-aacA4-aadA, was characterized. A metallo-β-lactamaseo gene was also found to be carried on the gene cassette of blaVIM-3-orf2a-aacA4-aadB-aacA4 inserted in a class 1 integron obtained from meropenem-resistant P. aeruginosa isolates.

Carriage of Class 1 and 2 Integrons in Acinetobacter baumannii and Pseudomonas aeruginosa Isolated from Clinical Specimens and a Novel Gene Cassette Array: blaOXA-11-cmlA7

The dissemination of antibiotic resistance genes between bacteria leads to serious problems in the treatment of infectious diseases. It has been shown that resistance genes can also be carried by the integrons. There are limited studies regarding the carriage of class 1 and 2 integrons in Acinetobacter baumannii and Pseudomonas aeruginosa clinical strains in Turkey. The aims of this study were to investigate the carriage rates of class 1 and class 2 integrons in A.baumannii and P.aeruginosa strains isolated from clinical samples in Abant Izzet Baysal University Hospital, and to characterize the antibiotic resistance gene cassettes in these integrons by sequence analyses. A total of 137 strains (77 A.baumannii and 60 P.aeruginosa) isolated from various clinical specimens (56% were sputum, 19% wound, 11% urine, 11% blood, 3% catheter), between March 2010-December 2012, were included in the study. The identification and antibiotic susceptibility tests of the isolates were performed by Vitek 2 Compact (bioMérieux, France) and BD Phoenix 100 (Becton Dickinson, USA) systems. The presence of integrons were screened by PCR method using specific primer pairs targeting class 1 (intI1) and 2 (intI2) integrase regions. All the samples that revealed integron amplification were subjected to DNA sequence analysis, both in the forms of cloned products and PCR amplicons. In the study, the highest susceptibility rates were found against colistin (96%) and tigecycline (78%) in A.baumannii, and against piperacillin/tazobactam (97%) and piperacillin (93%) in P.aeruginosa isolates. The highest resistance rate was determined for piperacillin/tazobactam (95%) in A.baumannii strains. The presence of intI1 gene was detected in 33% (26/77) of A.baumannii and 10% (6/60) of P.aeruginosa isolates. When variable regions in intI1 positive strains were amplified by PCR, eight (8/77, 10%) A.baumannii and three (3/60, 5%) P.aeruginosa strains were found to harbor antibiotic resistance gene cassettes. IntI2 gene was not detected in any of the isolates. Resistance to piperacillin/tazobactam, ceftazidime, cefepime, ceftriaxone and ampicillin/sulbactam was detected as the common resistance pattern in all integron-positive A.baumannii strains, whereas resistance to ceftazidime, gentamicin and ciprofloxacin was the common pattern in all integron-positive P.aeruginosa strains. DNA sequence analysis of variable regions of integrons indicated that two separate gene cassette arrays (aacC1-aadA1 and aac(3)-1) were carried by A.baumannii strains, and two types of gene cassette arrays (blaOXA-30-aadA1 and blaOXA-11-cmlA7) were carried by P.aeruginosa strains. To our best knowledge, this is the first report of the gene sequence of blaOXA-11-cmlA7 defined in an integron gene cassette of P.aeruginosa.

Molecular diversity of class 2 integrons in antibiotic-resistant gram-negative bacteria found in wastewater environments in China

The molecular architecture of class 2 integrons among gram-negative bacteria from wastewater environments was investigated in Jinan, China. Out of the 391 antibiotic-resistant bacteria found, 38 isolates harboring class 2 integrons encoding potentially transferrable genes that could confer antibiotic resistance were found. These isolates were classified into 19 REP-PCR types. These strains were identified using 16S rRNA gene sequencing and found to be as follows: Proteus mirabilis (16), Escherichia coli (7), Providencia spp. (7), Proteus spp. (2), P. vulgaris (3), Shigella sp. (1), Citrobacter freundii (1), and Acinetobacter sp. (1). Their class 2 integron cassette arrays were amplified and then either analyzed using PCR-RFLP or sequenced. The typical array dfrA1-sat2-aadA1 was detected in 27 isolates. Six atypical arrays were observed, including three kinds of novel arrangements (linF2(∆attC1)-dfrA1(∆attC2)-aadA1-orf441 or linF2(∆attC1)-dfrA1(∆attC2)-aadA1, dfrA1-catB2-sat2-aadA1, and estX(Vr)-sat2-aadA1) and a hybrid with the 3'CS of class 1 integrons (dfrA1-sat2-aadA1-qacH), and dfrA1-sat1. Twenty-four isolates were also found to carry class 1 integrons with 10 types of gene cassette arrays. Several non-integron-associated antibiotic resistance genes were found, and their transferability was investigated. Results showed that water sources in the Jinan region harbored a diverse community of both typical and atypical class 2 integrons, raising concerns about the overuse of antibiotics and their careless disposal into the environment.

Integron-bearing methicillin-resistant coagulase-negative staphylococci in South China, 2001–2004

A total of 53 methicillin-resistant coagulase-negative staphylococci strains isolated in a hospital in Guangzhou, China, were analyzed to detect class 1 integrons and SCCmec typing. Thirty strains had the class 1 integrase (intI1) gene and 26 strains possessed the 3' conserved region of qacEDelta1-sul1. Four different types of gene cassette arrays were found and a highly prevalent array of dfrA12-orfF-aadA2 gene cassettes was observed. Thirty class 1 integron-positive coagulase-negative staphylococci strains were subjected to Southern hybridization analysis; the result showed that class 1 integrons were located on chromosome, not plasmid. According to the results of SCCmec typing for 30 integron-bearing MRCNS strains, five, 15 and five strains belonged to type I, II and III SCCmec, respectively, and five strains were untypeable. For 23 non-integron-bearing methicillin-resistant coagulase-negative staphylococci strains, four, nine and seven strains belonged to type I, II and III SCCmec, respectively, and three strains were untypeable. None of the strains belonged to type IV or V. Twenty-three coagulase-negative staphylococci isolates of three Staphylococcal species that contained the dfrA12-orfF-aadA2 gene cassette array were phylogenetically unrelated to each other by randomly amplified polymorphic DNA, indicating that the gene cassettes might be disseminated in the clinical strains by a horizontal gene transfer.