scholarly journals Dissection of the Activity of Agricultural Fungicides against Clinical Aspergillus Isolates with and without Environmentally and Medically Induced Azole Resistance

2021 ◽  
Vol 7 (3) ◽  
pp. 205
Author(s):  
Karin Meinike Jørgensen ◽  
Marie Helleberg ◽  
Rasmus Krøger Hare ◽  
Lise Nistrup Jørgensen ◽  
Maiken Cavling Arendrup
Keyword(s):  
Growth Inhibition ◽  
Type A ◽  
Clinical Isolates ◽  
Azole Resistance ◽  
Wild Type ◽  
Resistance Mutations ◽  
Resistance Development ◽  
Azole Fungicides

Azole resistance is an emerging problem in patients with aspergillosis. The role of fungicides for resistance development and occurrence is not fully elucidated. EUCAST reference MICs of 17 fungicides (11 azoles and 6 others), five azole fungicide metabolites and four medical triazoles were examined against two reference and 28 clinical isolates of A. fumigatus, A. flavus and A. terreus with (n = 12) and without (n = 16) resistance mutations. Eight/11 azole fungicides were active against wild-type A. fumigatus, A. flavus and A. terreus, including four (metconazole, prothioconazole-desthio, prochloraz and imazalil) with low MIC50 (≤2 mg/L) against all three species and epoxiconazole, propiconazole, tebuconazole and difenoconazole also against wild-type A. terreus. Mefentrifluconazole, azole metabolites and non-azole fungicides MICs were >16 mg/L against A. fumigatus although partial growth inhibition was found with mefentrifluconazole. Moreover, mefentrifluconazole and axozystrobin were active against wild-type A. terreus. Increased MICs (≥3 dilutions) were found for TR34/L98H, TR34(3)/L98H, TR46/Y121F/T289A and G432S compared to wild-type A. fumigatus for epoxiconazole, propiconazole, tebuconazole, difenoconazole, prochloraz, imazalil and metconazole (except G432S), and for prothioconazole-desthio against TR46/Y121F/T289A, specifically. Increased MICs were found in A. fumigatus harbouring G54R, M220K and M220R alterations for five, one and one azole fungicides, respectively, compared to MICs against wild-type A. fumigatus. Similarly, increased MICs wer found for A. terreus with G51A, M217I and Y491H alterations for five, six and two azole fungicides, respectively. Azole fungicides showed activity against wild-type A. fumigatus, A. terreus and A. flavus, but not against all mutant isolates, suggesting the environmental route of azole resistance may have a role for all three species.

scholarly journals A Novel Environmental Azole Resistance Mutation inAspergillus fumigatusand a Possible Role of Sexual Reproduction in Its Emergence

mBio ◽  
2017 ◽  
Vol 8 (3) ◽  
Author(s):  
Jianhua Zhang ◽  
Eveline Snelders ◽  
Bas J. Zwaan ◽  
Sijmen E. Schoustra ◽  
Jacques F. Meis ◽  
...  
Keyword(s):  
Aspergillus Fumigatus ◽  
Sexual Reproduction ◽  
Crop Protection ◽  
Resistance Mutation ◽  
Azole Resistance ◽  
Wild Type ◽  
Resistance Mutations ◽  
Resistance Selection ◽  
Genotype 2

ABSTRACTThis study investigated the dynamics ofAspergillus fumigatusazole-resistant phenotypes in two compost heaps with contrasting azole exposures: azole free and azole exposed. After heat shock, to which sexual but not asexual spores are highly resistant, the azole-free compost yielded 98% (49/50) wild-type and 2% (1/50) azole-resistant isolates, whereas the azole-containing compost yielded 9% (4/45) wild-type and 91% (41/45) resistant isolates. From the latter compost, 80% (36/45) of the isolates contained the TR46/Y121F/T289A genotype, 2% (1/45) harbored the TR46/Y121F/M172I/T289A/G448S genotype, and 9% (4/45) had a novel pan-triazole-resistant mutation (TR463/Y121F/M172I/T289A/G448S) with a triple 46-bp promoter repeat. Subsequent screening of a representative set of clinicalA. fumigatusisolates showed that the novel TR463mutant was already present in samples from three Dutch medical centers collected since 2012. Furthermore, a second new resistance mutation was found in this set that harbored four TR46repeats. Importantly, in the laboratory, we recovered the TR463mutation from a sexual cross between two TR46isolates from the same azole-containing compost, possibly through unequal crossing over between the double tandem repeats (TRs) during meiosis. This possible role of sexual reproduction in the emergence of the mutation was further implicated by the high level of genetic diversity of STR genotypes in the azole-containing compost. Our study confirms that azole resistance mutations continue to emerge in the environment and indicates compost containing azole residues as a possible hot spot. Better insight into the biology of environmental resistance selection is needed to retain the azole class for use in food production and treatment ofAspergillusdiseases.IMPORTANCEComposting of organic matter containing azole residues might be important for resistance development and subsequent spread of resistance mutations inAspergillus fumigatus. In this article, we show the dominance of azole-resistantA. fumigatusin azole-exposed compost and the discovery of a new resistance mutation with clinical relevance. Furthermore, our study indicates that current fungicide application is not sustainable as new resistance mutations continue to emerge, thereby threatening the use of triazoles in medicine. We provide evidence that the sexual part of the fungal life cycle may play a role in the emergence of resistance mutations because under laboratory conditions, we reconstructed the resistance mutation through sexual crossing of two azole-resistantA. fumigatusisolates derived from the same compost heap. Understanding the mechanisms of resistance selection in the environment is needed to design strategies against the accumulation of resistance mutations in order to retain the azole class for crop protection and treatment ofAspergillusdiseases.

scholarly journals Magnitude of Voriconazole Resistance in Clinical and Environmental Isolates of Aspergillus flavus and Investigation into the Role of Multidrug Efflux Pumps

2018 ◽  
Vol 62 (11) ◽  
Author(s):  
Raees A. Paul ◽  
Shivaprakash M. Rudramurthy ◽  
Manpreet Dhaliwal ◽  
Pankaj Singh ◽  
Anup K. Ghosh ◽  
...  
Keyword(s):  
Aspergillus Flavus ◽  
Efflux Pump ◽  
Efflux Pumps ◽  
Azole Resistance ◽  
Wild Type ◽  
Multidrug Efflux ◽  
Environmental Isolates ◽  
Content Type ◽  
Multidrug Efflux Pumps

ABSTRACT The magnitude of azole resistance in Aspergillus flavus and its underlying mechanism is obscure. We evaluated the frequency of azole resistance in a collection of clinical (n = 121) and environmental isolates (n = 68) of A. flavus by the broth microdilution method. Six (5%) clinical isolates displayed voriconazole MIC greater than the epidemiological cutoff value. Two of these isolates with non-wild-type MIC were isolated from same patient and were genetically distinct, which was confirmed by amplified fragment length polymorphism analysis. Mutations associated with azole resistance were not present in the lanosterol 14-α demethylase coding genes (cyp51A, cyp51B, and cyp51C). Basal and voriconazole-induced expression of cyp51A homologs and various efflux pump genes was analyzed in three each of non-wild-type and wild-type isolates. All of the efflux pump genes screened showed low basal expression irrespective of the azole susceptibility of the isolate. However, the non-wild-type isolates demonstrated heterogeneous overexpression of many efflux pumps and the target enzyme coding genes in response to induction with voriconazole (1 μg/ml). The most distinctive observation was approximately 8- to 9-fold voriconazole-induced overexpression of an ortholog of the Candida albicans ATP binding cassette (ABC) multidrug efflux transporter, Cdr1, in two non-wild-type isolates compared to those in the reference strain A. flavus ATCC 204304 and other wild-type strains. Although the dominant marker of azole resistance in A. flavus is still elusive, the current study proposes the possible role of multidrug efflux pumps, especially that of Cdr1B overexpression, in contributing azole resistance in A. flavus.

scholarly journals Characterization of Biofilm Formation and the Role of BCR1 in Clinical Isolates of Candida parapsilosis

2013 ◽  
Vol 13 (4) ◽  
pp. 438-451 ◽  
Author(s):  
Srisuda Pannanusorn ◽  
Bernardo Ramírez-Zavala ◽  
Heinrich Lünsdorf ◽  
Birgitta Agerberth ◽  
Joachim Morschhäuser ◽  
...  
Keyword(s):  
Biofilm Formation ◽  
Candida Parapsilosis ◽  
Clinical Isolates ◽  
Wild Type ◽  
Content Type ◽  
Initial Adhesion ◽  
High Level ◽  
Increased Susceptibility

ABSTRACT In Candida parapsilosis , biofilm formation is considered to be a major virulence factor. Previously, we determined the ability of 33 clinical isolates causing bloodstream infection to form biofilms and identified three distinct groups of biofilm-forming strains (negative, low, and high). Here, we establish two different biofilm structures among strains forming large amounts of biofilm in which strains with complex spider-like structures formed robust biofilms on different surface materials with increased resistance to fluconazole. Surprisingly, the transcription factor Bcr1, required for biofilm formation in Candida albicans and C. parapsilosis , has an essential role only in strains with low capacity for biofilm formation. Although BCR1 leads to the formation of more and longer pseudohyphae, it was not required for initial adhesion and formation of mature biofilms in strains with a high level of biofilm formation. Furthermore, an additional phenotype affected by BCR1 was the switch in colony morphology from rough to crepe, but only in strains forming high levels of biofilm. All bcr1 Δ/Δ mutants showed increased proteolytic activity and increased susceptibility to the antimicrobial peptides protamine and RP-1 compared to corresponding wild-type and complemented strains. Taken together, our results demonstrate that biofilm formation in clinical isolates of C. parapsilosis is both dependent and independent of BCR1 , but even in strains which showed a BCR1 -independent biofilm phenotype, BCR1 has alternative physiological functions.

scholarly journals In Vitro Generation of Novel Pyrimethamine Resistance Mutations in the Toxoplasma gondiiDihydrofolate Reductase

2001 ◽  
Vol 45 (4) ◽  
pp. 1271-1277 ◽  
Author(s):  
Mary G. Reynolds ◽  
Jung Oh ◽  
David S. Roos
Keyword(s):  
Potential Role ◽  
Opportunistic Infections ◽  
Potent Inhibitor ◽  
Random Mutagenesis ◽  
Protozoan Parasite ◽  
Amino Acid Residues ◽  
Wild Type ◽  
Resistance Mutations

ABSTRACT Pyrimethamine is a potent inhibitor of dihydrofolate reductase and is widely used in the treatment of opportunistic infections caused by the protozoan parasite Toxoplasma gondii. In order to assess the potential role of dhfr sequence polymorphisms in drug treatment failures, we examined the dhfr-ts genes of representative isolates for T. gondii virulence types I, II, and III. These strains exhibit differences in their sensitivities to pyrimethamine but no differences in predicted dhfr-tsprotein sequences. To assess the potential for pyrimethamine-resistantdhfr mutants to emerge, three drug-sensitive variants of the T. gondii dhfr-ts gene (the wild-type T. gondii sequence and two mutants engineered to reflect polymorphisms observed in drug-sensitive Plasmodium falciparum) were subjected to random mutagenesis and transfected into either wild-type T. gondii parasites ordhfr-deficient Saccharomyces cerevisiae under pyrimethamine selection. Three resistance mutations were identified, at amino acid residues 25 (Trp→Arg), 98 (Leu→Ser), and 134 (Leu→His).

SIRT1 Inhibition Induces Apoptosis In Human CML Progenitors by Enhancing p53 Acetylation and Activation

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 200-200
Author(s):  
Ling Li ◽  
Lisheng Wang ◽  
Tinisha McDonald ◽  
Aswani Bolla ◽  
Tessa L. Holyoake ◽  
...  
Keyword(s):  
Growth Inhibition ◽  
Transcriptional Activity ◽  
P53 Gene ◽  
K562 Cells ◽  
Wild Type ◽  
P53 Expression ◽  
Significant Growth ◽  
Cd34 Cells ◽  
Significant Growth Inhibition

Abstract Abstract 200 Imatinib mesylate (IM) treatment is effective in inhibiting CML primitive progenitor growth but induces only modest levels of apoptosis. Improved approaches to enhance elimination of residual CML progenitors in IM-treated patients are required. The NAD+ dependent deacetylase SIRT1 is a stress-response gene that is expressed at higher levels in CML compared to normal CD34+ progenitors. We have shown that inhibition of SIRT1 expression using lentivirus-mediated SIRT1 shRNA expression results in modest induction of apoptosis in CML progenitors and significantly enhanced apoptosis in combination with IM (Blood 2009, 114: 189). SIRT1 inhibition does not induce apoptosis in normal progenitors or increase their sensitivity to IM. SIRT1 can potentially regulate the acetylation of several transcription factors, including the p53 tumor suppressor protein. In contrast to several other cancers, p53 mutations are rare in CP CML, suggesting that p53 may still be subject to activation in CML progenitors. However we have observed that p53 levels are reduced in IM-treated CML CD34+ progenitors. We were therefore interested in investigating whether increased apoptosis of CML progenitors following SIRT1 inhibition was related to enhancement of p53 activity via protein acetylation. We observed that inhibition of SIRT1 using shRNA resulted in increased acetylation of p53 in CML CD34+ cells without increase in total p53 expression on both western blotting and flow cytometry. SIRT1 inhibition also increased p53 acetylation in IM-treated cells. Acetylated p53 was observed to localize to the nuclei of CML CD34+ cells on immunofluorescence microscopy. Q-PCR analysis revealed increased expression of the p53 transcriptional targets, GFI-1 and Necdin, in SIRT1 knockdown CML CD34+ cells (Necdin, Si versus Ctrl, 2.7±0.4 fold, p<0.05, n=3; GFI-1, Si versus Ctrl, 2.4±0.4 fold, p<0.05, n=3). These results suggest that SIRT1 inhibition results in increased p53 acetylation, nuclear localization and transcriptional activity in CML CD34+ cells. To further investigate the role of p53 in mediating the effects of SIRT1 inhibition we concomitantly knocked down both p53 and SIRT1 in CML CD34+ cells. Inhibition of p53 expression by lentivirus mediated delivery of p53 shRNA significantly enhanced growth and reduced apoptosis of SIRT1 knockdown CML CD34+ cells (14±2% apoptosis with SIRT1 knockdown, 7±2% apoptosis with combined SIRT1 and p53 knockdown, p<0.05, n=3). These results confirm an important role for p53 in SIRT1 mediated effects in CML progenitors. SIRT1 inhibition did not inhibit growth or induce apoptosis in CML blast crisis K562 cells, which are p53 null. To further determine the specific role of p53 acetylation in mediating SIRT1 effects, we expressed both wild type and acetylation-deficient p53 constructs in K562 cells. K562 cells ectopically expressing the wild type p53 gene demonstrated significant growth inhibition and apoptosis following SIRT1 knockdown (SIRT1 shRNA, 18±5% versus Ctrl shRNA, 8±3%, p<0.05), increased levels of acetylated p53, and enhanced transactivation of a p53 reporter containing the mdm2 promoter cloned upstream of the luciferase gene (p<0.05). In contrast, K562 cells transfected with an acetylation-defective p53 gene (with all eight acetylation sites mutated) did not demonstrate significant growth inhibition or apoptosis following SIRT1 inhibition. These results indicate that the inhibitory effect of SIRT1 on CML cells is dependent on p53 acetylation. We conclude that inhibition of SIRT1 enhances p53 acetylation and transcriptional activity resulting in enhanced apoptosis of CML progenitors. SIRT1 is a potentially druggable target, and several groups are actively developing SIRT1 inhibitory compounds. Activation of p53 via SIRT1 inhibition represents an attractive approach to eradicate CML stem cells in combination with IM or other treatments. Disclosures: No relevant conflicts of interest to declare.

Association of A313g Glutathione S-Transferase P1 (GSTP1) Inborn Polymorphism with Susceptibility to De Novo MDS

Blood ◽  
2012 ◽  
Vol 120 (21) ◽  
pp. 1445-1445
Author(s):  
Sophia Zachaki ◽  
Chryssa Stavropoulou ◽  
Aggeliki Daraki ◽  
Marina Kalomoiraki ◽  
Panagoula Kollia ◽  
...  
Keyword(s):  
De Novo ◽  
Conflicts Of Interest ◽  
Type A ◽  
Common Mechanism ◽  
Genotype Distribution ◽  
Distribution Analysis ◽  
Wild Type ◽  
Increased Risk ◽  
Variant Genotype

Abstract Abstract 1445 Models for the pathogenesis of myelodysplastic syndromes (MDS) imply the role of individual genetic variations in genes involved in detoxification mechanisms. GSTP1 enzyme plays a key role in detoxification of a variety of electrophilic compounds, such as benzo [a]-pyrene and other polycyclic aromatic hydrocarbons (PAHs), chemotherapy drugs and products of oxidative stress. GSTP1 acts through a common mechanism of conjugating reactive oxygen species (ROS) with glutathione, enabling their detoxification and elimination and thus defending tissues against DNA damage. The corresponding gene is subject to a single-nucleotide polymorphism (A313G) leading to abolished enzyme activity. Thus, individuals homozygous for the variant G allele (G/G) have a lower conjugating activity than individuals homozygous for the wild type A allele (A/A), while heterozygotes (A/G) display intermediate activity. The aim of the present study was to evaluate whether the GSTP1 polymorphism influences susceptibility to MDS and/or promote specific chromosomal aberrations. We conducted a case-control study in 310 de novo MDS patients and 370 unrelated healthy controls using both a conventional PCR-RFLP assay and a novel Real-Time PCR genotyping method using hybridization probe technology. The GSTP1 gene status was also evaluated in relation to patients' characteristics and chromosomal abnormalities. Comparison of the genotype distribution between controls and MDS cases revealed a significantly higher frequency of the variant genotypes (heterozygotes A/A and homozygotes G/G) among MDS patients, as compared to controls (p<0.0001, χ2=31.167, df=2). The most marked statistical difference between MDS patients and controls was observed between the wild-type (A/A) and the homozygous variant genotype (G/G), since subjects carrying the G/G variant genotype showed a 4.1-fold increased risk of MDS prevalence than subjects carrying the wild-type A/A genotype (p=0.000, χ2=30.5, d.f.=1, OR=4.098, 95%CI=[2.433–6.897]). Allele frequencies distribution analysis between patients and controls, showed that MDS patients exhibited a 1.9-fold increased risk of carrying at least one variant G allele, as compared to the controls (p<0.0001, d.f.=1, OR =1.9, 95%CI=[1.48–2.34]). There was no association between the GSTP1 polymorphism and gender or any specific cytogenetic subgroup, while stratification of patients according to age showed a differential GSTP1 genotype distribution (p=0.007). Our results, derived from the larger series of primary MDS cases tested for the GSTP1 genetic background, reveal an increased incidence of the GSTP1 variant genotypes among MDS patients, providing evidence for a potential pathogenetic role of the GSTP1 polymorphism on de novo MDS risk. Disclosures: No relevant conflicts of interest to declare.

scholarly journals New Insights into the Cyp51 Contribution to Azole Resistance in Aspergillus Section Nigri

2019 ◽  
Vol 63 (7) ◽  
Author(s):  
Alba Pérez-Cantero ◽  
Loida López-Fernández ◽  
Josep Guarro ◽  
Javier Capilla
Keyword(s):  
Resistance Mechanisms ◽  
Azole Resistance ◽  
Wild Type ◽  
Severe Condition ◽  
Content Type ◽  
Recommended Treatment ◽  
Highly Active ◽  
Expression Studies

ABSTRACT Invasive aspergillosis (IA) is a severe condition mainly caused by Aspergillus fumigatus, although other species of the genus, such as section Nigri members, can also be involved. Voriconazole (VRC) is the recommended treatment for IA; however, the prevalence of azole-resistant Aspergillus isolates has alarmingly increased in recent years, and the underlying resistance mechanisms in non-fumigatus species remain unclear. We have determined the in vitro susceptibility of 36 strains from section Nigri to VRC, posaconazole (POS), and itraconazole (ITC), and we have explored the role of Cyp51A and Cyp51B, both targets of azoles, in azole resistance. The three drugs were highly active; POS displayed the best in vitro activity, while ITC and VRC showed MICs above the established epidemiological cutoff values in 9 and 16% of the strains, respectively. Furthermore, expression studies of cyp51A and cyp51B in control condition and after VRC exposure were performed in 14 strains with different VRC susceptibility. We found higher transcription of cyp51A, which was upregulated upon VRC exposure, but no correlation between MICs and cyp51 transcription levels was observed. In addition, cyp51A sequence analyses revealed nonsynonymous mutations present in both, wild-type and non-wild-type strains of A. niger and A. tubingensis. Nevertheless, a few mutations were exclusively present in non-wild-type A. tubingensis strains. Altogether, our results suggest that azole resistance in section Nigri is not clearly explained by Cyp51A protein alteration or by cyp51 gene upregulation, which indicates that other mechanisms might be involved.

scholarly journals In VitroActivity of ASP2397 against Aspergillus Isolates with or without Acquired Azole Resistance Mechanisms

2015 ◽  
Vol 60 (1) ◽  
pp. 532-536 ◽  
Author(s):  
Maiken Cavling Arendrup ◽  
Rasmus Hare Jensen ◽  
Manuel Cuenca-Estrella
Keyword(s):  
Amphotericin B ◽  
Target Gene ◽  
Antifungal Agents ◽  
Susceptibility Testing ◽  
Resistance Mechanisms ◽  
Azole Resistance ◽  
Wild Type ◽  
Resistance Mutations ◽  
Content Type

ABSTRACTASP2397 is a new compound with a novel and as-yet-unknown target different from that of licensed antifungal agents. It has activity againstAspergillusandCandida glabrata. We compared itsin vitroactivity against wild-type and azole-resistantA. fumigatusandA. terreusisolates with that of amphotericin B, itraconazole, posaconazole, and voriconazole. Thirty-four isolates, including 4 wild-typeA. fumigatusisolates, 24A. fumigatusisolates with alterations in CYP51A TR/L98H (5 isolates), M220 (9 isolates), G54 (9 isolates), and HapE (1 isolate), andA. terreusisolates (2 wild-type isolates and 1 isolate with an M217I CYP51A alteration), were analyzed. EUCAST E.Def 9.2 and CLSI M38-A2 MIC susceptibility testing was performed. ASP2397 MIC50values (in milligrams per liter, with MIC ranges in parentheses) determined by EUCAST and CLSI were 0.5 (0.25 to 1) and 0.25 (0.06 to 0.25) againstA. fumigatusCYP51A wild-type isolates and were similarly 0.5 (0.125 to >4) and 0.125 (0.06 to >4) against azole-resistantA. fumigatusisolates, respectively. These values were comparable to those for amphotericin B, which were 0.25 (0.125 to 0.5) and 0.25 (0.125 to 0.25) against wild-type isolates and 0.25 (0.125 to 1) and 0.25 (0.125 to 1) against isolates with azole resistance mechanisms, respectively. In contrast, MICs for the azole compounds were elevated and highest for itraconazole: >4 (1 to >4) and 4 (0.5 to >4) against isolates with azole resistance mechanisms compared to 0.125 (0.125 to 0.25) and 0.125 (0.06 to 0.25) against wild-type isolates, respectively. ASP2397 was active againstA. terreusCYP51A wild-type isolates (MIC 0.5 to 1), whereas MICs of both azole and ASP2397 were elevated for the mutant isolate. ASP2397 displayedin vitroactivity againstA. fumigatusandA. terreusisolates which was independent of the presence or absence of azole target gene resistance mutations inA. fumigatus. The findings are promising at a time when azole-resistantA. fumigatusis emerging globally.

scholarly journals Nosocomial spread of OXA-232-producing Klebsiella pneumoniae ST15 in a teaching hospital, Shanghai, China

2019 ◽  
Vol 19 (1) ◽  
Author(s):  
Xin Li ◽  
Wei Ma ◽  
Qin Qin ◽  
Shanrong Liu ◽  
Liyan Ye ◽  
...  
Keyword(s):  
Klebsiella Pneumoniae ◽  
Teaching Hospital ◽  
Eastern China ◽  
Type A ◽  
Clinical Isolates ◽  
Low Level ◽  
Significant Homology

Abstract Background The spread and outbreak of Enterobacteriaceae producing OXA-48-like carbapenemases have become more and more prevalent in China. Results A total of 62 non-duplicated OXA-232-producing K. pneumoniae (OXA232Kp) were isolated between 2015 and 2017. An outbreak of OXA232Kp was observed in burn ICU. The 62 OXA232Kp isolates were all belongs to ST15 and categorized into two PFGE types (A and B). Type A was dominated of the isolates, which contained 61 clinical isolates and divided into 10 subtypes (A1-A10). In addition, most of OXA232Kp strains exhibited low-level carbapenems resistance. All strains carried a 6141 bp ColKP3 plasmid harboring the blaOXA-232 gene which is highly homologous to other blaOXA-232-bearing plasmids involved in other studies in eastern China. Conclusions In this study, clone transmission of OXA232Kp ST15was observed. Highly significant homology among the blaOXA-232-bearing plasmids indicated the important role of the 6.1 kb ColE-like plasmid on the prevalence of blaOXA-232 gene in China.

scholarly journals Role of ampD Homologs in Overproduction of AmpC in Clinical Isolates of Pseudomonas aeruginosa

2008 ◽  
Vol 52 (11) ◽  
pp. 3922-3927 ◽  
Author(s):  
Amber J. Schmidtke ◽  
Nancy D. Hanson
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Model System ◽  
Clinical Isolates ◽  
Rna Expression ◽  
Wild Type ◽  
Sequence Analyses ◽  
Strain Pao1 ◽  
Unknown Factor ◽  
Recycling Pathway

ABSTRACT AmpD indirectly regulates the production of AmpC β-lactamase via the cell wall recycling pathway. Recent publications have demonstrated the presence of multiple ampD genes in Pseudomonas aeruginosa and Escherichia coli. In the prototype P. aeruginosa strain, PAO1, the three ampD genes (ampD, ampDh2, and ampDh3) contribute to a stepwise regulation of ampC β-lactamase and help explain the partial versus full derepression of ampC. In the present study, the roles of the three ampD homologs in nine clinical P. aeruginosa isolates with either partial or full derepression of ampC were evaluated. In eight of nine isolates, decreased RNA expression of the ampD genes was not associated with an increase in ampC expression. Sequence analyses revealed that every derepressed isolate carried mutations in ampD, and in two fully derepressed strains, only ampD was mutated. Furthermore, every ampDh2 gene was of the wild type, and in some fully derepressed isolates, ampDh3 was also of the wild type. Mutations in ampD and ampDh3 were tested for their effect on function by using a plasmid model system, and the observed mutations resulted in nonfunctional AmpD proteins. Therefore, although the sequential deletion of the ampD homologs of P. aeruginosa can explain partial and full derepression in PAO1, the same model does not explain the overproduction of AmpC observed in these clinical isolates. Overall, the findings of the present study indicate that there is still an unknown factor(s) that contributes to ampC regulation in P. aeruginosa.

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