Emergence of NDM-1-producing Pseudomonas aeruginosa Sequence Type 773 Clone: Shift of Carbapenemase Molecular Epidemiology and Spread of 16S rRNA Methylase Genes in Korea.

Imipenemase (IMP)-6-producing Pseudomonas aeruginosa sequence type (ST) 235 is a dominant clone of carbapenemase-producing P. aeruginosa (CPPAE) in Korea. As part of the Antimicrobial Resistance Surveillance System in Korea, we found an increase in the carbapenem resistance rate of P. aeruginosa isolates from blood cultures and a shift in the molecular epidemiology of CPPAE. A total of 212 non-duplicated P. aeruginosa blood isolates were obtained from nine general hospitals and two nursing homes. Twenty-four isolates were identified as CPPAE. We observed the emergence of the NDM-1 P. aeruginosa ST 773 clone (N=10), mostly from Gyeongsang Province. The IMP-6 ST 235 clone (N=11) was detected in all provinces. CPPAE isolates showed very high resistance rates to amikacin, and all NDM-1 P. aeruginosa strains carried rmtB. This is the first nationwide surveillance of the recently emerged NDM-1-producing P. aeruginosa ST773 clone in Korea. Continuous surveillance is necessary to prevent the infection and transmission of carbapenem- and amikacin-resistant P. aeruginosa in Korea.

Prevalence of 16S rRNA methylase genes among ß-lactamase-producing Enterobacteriaceae clinical isolates in Saudi Arabia.

BACKGROUND: Co production of 16S rRNA methylases gene and ß-Lactamase gene among Enterobacteriaceae isolates conferring resistance to both therapeutic options has serious implications for clinicians worldwide. METHODS: To study co existence of 16S rRNA methylases (armA, rmtA, rmtB, rmtC, rmtD, and npmA) and ß-Lactamase (blaTEM-1, blaSHV-12, blaCTX-M-14) genes, we screened all phenotypic positive ß-Lactamase producing enterobacteriaceae by polymerase chain reaction (PCR) targeting above genes. A total of 330 enterobacteriaceae strains were collected during study period out of that 218 isolates were identified phenotypically as ß-Lactamase producers, which include 50 (22.9%) Escherichia coli; 92 (42.2%) Klebsiella pneumoniae, 44 (20.2%), Citrobactor freundii and 32 (14.7%) Enterobacter spp. RESULTS: Among this 218, only 188 isolates harbored the resistant gene for ß-Lactamase production. Major ß-Lactamase producing isolates were blaTEM-1 type. 122 (56 %) isolates were found to produce any one of the 16S rRNA methylase genes. A total of 116 isolates co produced b-Lactamase and at least one 16S rRNA methylases gene Co production of armA gene was found in 26 isolates with rmtB and in 4 isolates with rmtC. The rmtA and rmtD genes were not detected in any of the tested isolates. Six isolates were positive for a 16S rRNA methylase gene alone. CONCLUSION: ß-Lactamase producing isolates appears to coexist with 16S rRNA methylase predominantly armA and rmtB genes in the same isolate. We conclude the major ß-Lactamase and 16S rRNA methylases co-producer was K. pneumoniae followed by E. coli. We suggest further work on evaluating other ß-lactamases types and novel antibiotic resistance mechanisms among Enterobacteriaceae.

Drug Resistance Mechanism of Patients Infected with Aminoglycoside-resistant Acinetobacter Baumannii in Emergency Intensive Care Unit / 医药导报

Objective To investigate drug resistance mechanism of aminoglycoside-resistant Acinetobacter baumannii by detecting 16S rRNA methylase gene and three common genes of aminoglycoside-modifying enzymes in Acinetobacter baumannii infected patients at EICU. Methods The 48 Acinetobacter baumannii strains were collected,and antimicrobial susceptibility tests were performed by VITEK automicroscan. The MIC was detected by 2-fold agar dilution method,and genes were analyzed by polymerase chain reaction( PCR) . Results Among 48 strains,28 were highly resistant to aminoglycosides and 20 showed lower resistances. The 16S rRNA armA,APH(3')-I,ANT(3'')-Ia,AAC(6')-Ib genes were detected in 71. 43%,60. 71%,82. 14%, and 53. 57%of the 28 highly resistant strains,but only present in 0. 00%,0. 05%,0. 05%,and 0. 05%of the low-resistant isolates(P<0. 01). Conclusion The aminoglycoside-modifying enzymes and 16S rRNA methylase were frequently found in Acinetobacter baumannii clinical isolates,which is closely related to the high-level resistance to aminoglycoside antibiotics.

Distribution and resistance mechanism of 16S rRNA methylase in ESBL-producing Klebsiella pneumoniae / 中华微生物学和免疫学杂志

ObjectiveTo investigate the prevalence and distribution of 16S rRNA methylase gene and research the relationship with drug resistant spectrum.And preliminary explore its role in molecular epidemiology analysis.MethodsCollected 69 clinical isolates of non repetitive ESBL-producing Klebsiella pneumoniae in our hospital from Mar to Sep 2010.Detection 16S rRNA methylation enzyme gene by PCR,and analyze ESBL genetype and integron gene of the positive strains.All PCR products were sequenced for determination.Plasmid conjugation test and plasmid elimination method to determine dissemination of 16S rRNA methylase gene.Then we used ERIC-PCR genotyping technology for the establishment of DNA fingerprinting.ResultsIn sixty-nine strains,twenty isolates were rmtB positive (28.9％),two isolates were armA positive,and two strains coproduce rmtB and armA.All positive isolates carried the CTX-M gene,detemined by sequencing,14 strains of CTX-M-14 gene,6 strains of CTX-M-15 gene,14 strains carried TEM1 gene,8 strains carried SHY gene,sequencing showed that 5 strains of SHV-12 gene,3 strains of SHV-11 gene,3 strains carried OXA-10 gene,3 strains carried VBE-1 gene.In addition,the intl gene was found in 12 isolates of 20 rmtB positive strains.All the intl gene positive strains were divided into five kinds gene cassettes,which contained drfA25,drfA1,drfA12,aadA1,aadA2,sat and blaVEB-1 genes.Respectivily,16S rRNA methylase gene positive strains were divided into five genetypes using ERIC-PCR technology.A genetype was the advantage popular clones.Conjugative plasmid and elimination test found that rmtB gene was located in a plasmid in KP5 and KP16 isolates with A genetype,and can disseminate by conjugation.ConclusionA high prevalence of 16S rRNA methylase gene-rmtB was found among clinical ESBL-producing K.pneumoniae isolates in our hospital,which could lead to resistant to almost all aminoglycoside at a high level.Both horizontal gene transfer and clonal spread were responsible for the dissemination of the rmtB gene.In addition,K.pneumoniae co-producing ESBLs,16S rRNA methylation enzymes and class Ⅰ integron existed and were spreading.

aac(6')-Ⅰ b gene in drug-resistant strains of Pseudomonas aeruginosa / 中华临床感染病杂志

Objective To investigate the distribution of aminoglycoside modifying enzyme genes (AMEs) and 16S rRNA methylase genes in drug-resistant strains of Pseudomonas aeruginosa. Methods Twenty strains of drug-resistant Pseudomonas aeruginosa were isolated from sputum and wound secretion samples collected from the First People's Hospital of Huai' an in Jiangsu province. Eight AMEs [aac(3)-Ⅰ , aac(3)-Ⅱ, aac(6')-Ⅰb,aac(6')-Ⅱ, ant{2)-Ⅰ ,ant(3)-Ⅰ , ant(4')-Ⅰ , aph(3')-Ⅱb] and 6 16S rRNA methylase genes (armA, rmtA, rmtB, rmtC, rmtD, npmA) were analyzed by PCR and verified by DNA sequencing. Results Out of 20 strains of Pseudomonas aeruginosa, aac(6')-Ⅱ was positive in 8 strains (40.0% ) , ant2- Ⅰ in 8 strains (40.0% ) , aac(3)-Ⅱ in 5 strains (25.0% ) , aac(6')- Ⅰ b in 2 strains (10.0% ) and rmtB in 1 strains (5.0% ) , respectively. The rest 9 genes were not detected. Among 2 strains harboring aac(6')- Ⅰ b, DNA sequencing confirmed that 1 was aac(6')- Ⅰ b (the clssical type) and another was aac(6')- Ⅰ b-cr. Conclusion Gene aac(6')- Ⅰ b-cr exists in drug-resistant Pseudomonas aeruginosa, and it has modifying effect on both aminoglycosides and quinolones.

Aminoglycoside-modifying Enzyme and 16S rRNA Methylase Gene Expressions in Acinetobacter baumannii / 中华医院感染学杂志

OBJECTIVE To understand aminoglycoside-modifying enzyme and 16S rRNA methylase gene expressions in Acinetobacter baumannii in Xinjiang region.METHODS 20 A.baumannii strains were isolated and test the anti-bacterial drug sensitivity.PCR methods were used to test aminoglycoside-modifying enzyme and 16S rRNA methylase gene.RESULTS From thirteen A.baumannii strains detected the aminoglycoside-modifying enzyme genes,the detection rate was 65%;in which aac(3)-Ⅰ gene was positive in 4 strains(20%),aac(3)-Ⅱ gene in 8 strains(40%),aac(6′)-Ⅰad gene in 4 strain(20%),ant(3″)-Ⅰ gene in 4 strain(20%),and ant(2″)-Ⅰ gene was positive in 1 strain(5%).The aac(6′)-Ⅰ b and aac(6′)-Ⅱ gens and were not detected;the 16S rRNA gene methylation was negative.CONCLUSIONS There are aminoglycoside-modifying enzyme genes existing in A.baumannii,no 16S rRNA methylase gene was detected in Xinjiang region.

16S rRNA Methylase Gene and Aminoglycoside-modifying Enzyme Genes in Pseudomonas aeruginosa Isolated from Burned Patients / 中华医院感染学杂志

OBJECTIVE To investigate the 16S rRNA methylase gene and aminoglycoside-modifying enzyme genes in Pseudomonas aeruginosa isolated from burned patients. METHODS GNS-448 and K-B tests were performed to detect the susceptibility to 19 kinds of antimicrobial agents against these strains. 16S rRNA methylase gene and aminoglycoside-modifying enzyme genes were amplified by polymerase chain reaction (PCR) and verified by DNA sequencing. RESULTS The 32 isolated strains were all resistant to ampicillin,cefuroxime,cefoxitin,SMZ-TMP,The sensitive rates to amikacin and gentamicin were 68% and 46.9%,respectively. The resistant rates to imipenem and meropenem were 68.8% and 59.4%,respectively. The 16S rRNA methylase gene and aminoglycoside-modifying enzyme genes including aac(6')-Ⅰb,aac(6')-Ⅱ,ant(3″)-Ⅰ,ant(2″)-Ⅰ and rmtB were found and positive rates were 9.4%,3.1%,28.1%,25.0% and 3.1%,respectively. A novel subtype of aac(6')-Ⅰb was reported firstly. CONCLUSIONS There are high positive percentage of 16S rRNA methylase gene and aminoglycoside-modifying enzyme genes in P. aeruginosa isolated from burned patients. P. aeruginosa resistance to aminoglycoside relates to the existence of 16S rRNA methylase gene and aminoglycoside-modifying enzyme genes.

Detection of 16S rRNA methylase genes in Klebsiella pneumoniae / 临床检验杂志

Objective To investigate the prevalence of 16S rRNA methylase genes in Klebsiella pneumoniae isolates from Guangzhou.Methods K-B test was used to determine the resistant rates of these stains.Five 16S rRNA methylase genes,armA,rmtA,rmtB,rmtC,and rmtD,were detected by PCR.Results All 55 K.pneumoniae isolates showed resistant to arbekacin,gentamicin,tobramycin,and neomycin.Susceptibility rates were 5.5%,20.0%,72.7%,and 100% to ceftazidime,ciprofloxacin,piperacillin/tazobactam,and imipenem respectively.ESBLs were positive in 52 of 55 (94.5%) isolates.Among 55 K.pneumoniae isolates,34 were positive for armA and 1 for rmtB.Conclusions In K.pneumoniae resistant to arbekacin,the positive rate of 16S rRNA methylase genes was high,predominantly with armA positive.These strains were highly resistant to some antibiotics.