Genetic Analysis of a High-Level Vancomycin-Resistant Isolate of Staphylococcus aureus

Background. Global concerns have been raised due to upward trend of Vancomycin Intermediate Staphylococcus aureus (VISA) and Vancomycin Resistant Staphylococcus aureus (VRSA) reports which mean casting doubt on the absolute effectiveness of the last line of antibiotic treatment for S. aureus, vancomycin. Hence, epidemiological evaluation can improve global health care policies. Methodology. 171 Isolates of Staphylococcus aureus were collected from different types of clinical samples in selected hospitals in Isfahan, Mashhad, and Tehran, Iran. Then, they were evaluated by agar screening, disk diffusion, and MIC method to determine their resistance to vancomycin and methicillin. The isolated VISA strains were then confirmed with genetic analysis by the evaluation of mecA and vanA genes, SCCmec, agr, and spa type, and also toxin profiles. MLST was also performed. Results and Conclusion. Our data indicated that 67% of isolated S. aureus strains were resistant to methicillin. Furthermore, five isolates (2.9%) had intermediate resistance to vancomycin (VISA). In contrast to usual association of VISA with MRSA strains, we found two isolates of MSSA-VISA. Therefore, our data suggests a probable parallel growing trend of VISA towards MSSA, along with MRSA strains. However, more samples are required to confirm these primarily data. Moreover, genetic analysis of the isolated VISA strains revealed that these strains are endemic Asian clones.

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Genetic Analysis of a Vancomycin-Resistant Staphylococcus aureus Strain Isolated in Iran

mBio ◽

10.1128/mbio.00442-12 ◽

2012 ◽

Vol 3 (6) ◽

Cited By ~ 1

Author(s):

Amir Azimian ◽

Seyed Asghar Havaei ◽

Hosein Fazeli ◽

Mahmood Naderi ◽

Kiarash Ghazvini ◽

...

Keyword(s):

Staphylococcus Aureus ◽

Genetic Analysis ◽

Aureus Strain ◽

Vancomycin Resistant

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Penicillin-Binding Protein 2 Is Essential for Expression of High-Level Vancomycin Resistance and Cell Wall Synthesis in Vancomycin- Resistant Staphylococcus aureus Carrying the Enterococcal vanA Gene Complex

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.48.12.4566-4573.2004 ◽

2004 ◽

Vol 48 (12) ◽

pp. 4566-4573 ◽

Cited By ~ 31

Author(s):

Anatoly Severin ◽

Shang Wei Wu ◽

Keiko Tabei ◽

Alexander Tomasz

Keyword(s):

Staphylococcus Aureus ◽

Cell Wall ◽

Binding Protein ◽

Inducible Promoter ◽

Protein Product ◽

Vancomycin Resistance ◽

Penicillin Binding Protein ◽

Oxacillin Resistance ◽

Vancomycin Resistant ◽

High Level

ABSTRACT A combination of biochemical and genetic experiments were performed in order to better understand the mechanism of expression of high-level vancomycin resistance in Staphylococcus aureus. The transcription of pbp2 of the highly vancomycin- and oxacillin-resistant strain COLVA200 and its mutant derivative with inactivated mecA were put under the control of an inducible promoter, and the dependence of oxacillin and vancomycin resistance and cell wall composition on the concentration of the isopropyl-β-d-thiogalactopyranoside inducer was determined. The results indicate that mecA—the genetic determinant of oxacillin resistance—while essential for oxacillin resistance, is not involved with the expression of vancomycin resistance. Penicillin binding protein 2A, the protein product of mecA, appears to be unable to utilize the depsipeptide cell wall precursor produced in the vancomycin-resistant cells for transpeptidation. The key penicillin binding protein essential for vancomycin resistance and for the synthesis of the abnormally structured cell walls characteristic of vancomycin-resistant S. aureus (A. Severin, K. Tabei, F. Tenover, M. Chung, N. Clarke, and A. Tomasz, J. Biol. Chem. 279:3398-3407, 2004) is penicillin binding protein 2.

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Comparison of Tn1546-Like Elements in Vancomycin-Resistant Staphylococcus aureus Isolates from Michigan and Pennsylvania

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.49.1.470-472.2005 ◽

2005 ◽

Vol 49 (1) ◽

pp. 470-472 ◽

Cited By ~ 53

Author(s):

Nancye C. Clark ◽

Linda M. Weigel ◽

Jean B. Patel ◽

Fred C. Tenover

Keyword(s):

Staphylococcus Aureus ◽

Sequence Analysis ◽

Dna Sequence ◽

Intergenic Region ◽

Mobile Genetic Element ◽

Clinical Isolates ◽

Genetic Element ◽

Vancomycin Resistant ◽

High Level ◽

Genetic Events

ABSTRACT In 2002, the first two clinical isolates of vancomycin-resistant Staphylococcus aureus (VRSA) containing vanA were recovered in Michigan and Pennsylvania. Tn1546, a mobile genetic element that encodes high-level vancomycin resistance in enterococci, was present in both isolates. With PCR and DNA sequence analysis, we compared the Tn1546 elements from each isolate to the prototype Tn1546 element. The Michigan VRSA element was identical to the prototype Tn1546 element. The Pennsylvania VRSA element showed three distinct modifications: a deletion of nucleotides 1 to 3098 at the 5′ end, which eliminated the orf1 region; an 809-bp IS1216V-like element inserted before nucleotide 3099 of Tn1546; and an inverted 1,499-bp IS1251-like element inserted into the vanSH intergenic region. These differences in the Tn1546-like elements indicate that the first two VRSA isolates were the result of independent genetic events.

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Emergence of High-Level Vancomycin-Resistant Staphylococcus aureus in the Imam Khomeini Hospital in Tehran

Medical Principles and Practice ◽

10.1159/000141513 ◽

2008 ◽

Vol 17 (5) ◽

pp. 432-434 ◽

Cited By ~ 61

Author(s):

Marzieh Aligholi ◽

Mohammad Emaneini ◽

Fereshteh Jabalameli ◽

Shadi Shahsavan ◽

Hosein Dabiri ◽

...

Keyword(s):

Staphylococcus Aureus ◽

Vancomycin Resistant ◽

High Level

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Spontaneous Deletion of the Methicillin Resistance Determinant, mecA, Partially Compensates for the Fitness Cost Associated with High-Level Vancomycin Resistance in Staphylococcus aureus

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.01164-07 ◽

2008 ◽

Vol 52 (4) ◽

pp. 1221-1229 ◽

Cited By ~ 48

Author(s):

Michael J. Noto ◽

Paige M. Fox ◽

Gordon L. Archer

Keyword(s):

Staphylococcus Aureus ◽

Methicillin Resistance ◽

Chemotherapeutic Agents ◽

Vancomycin Resistance ◽

Resistance Determinant ◽

Gene Acquisition ◽

Resistant Strains ◽

Vancomycin Resistant ◽

Mrsa Strains ◽

High Level

ABSTRACT Treatment of infections caused by Staphylococcus aureus is often confounded by the bacterium's ability to develop resistance to chemotherapeutic agents. Methicillin-resistant S. aureus (MRSA) arises through the acquisition of staphylococcal chromosomal cassette mec (SCCmec), a genomic island containing the methicillin resistance determinant, mecA. In contrast, resistance to vancomycin can result from exposure to the drug, a mechanism that is not dependent upon a gene acquisition event. Here we describe three MRSA strains that became resistant to vancomycin during passage in the presence of increasing concentrations of the drug. In each case two derivative strains were isolated, one that had lost mecA and one that retained mecA during passage. Strain 5836VR lost mecA by the site-specific chromosomal excision of SCCmec, while the other two strains (strains 3130VR and VP32) deleted portions of their SCCmec elements in a manner that appeared to involve IS431. Conversion to vancomycin resistance caused a decrease in the growth rate that was partially compensated for by the deletion of mecA. In mixed-culture competition experiments, vancomycin-resistant strains that lacked mecA readily outcompeted their mecA-containing counterparts, suggesting that the loss of mecA during conversion to vancomycin resistance was advantageous to the organism.

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Vancomycin intermediate and high level vancomycin resistant Staphylococcus aureus clinical isolates in Osogbo, Nigeria

Microbiology Research ◽

10.4081/mr.2011.e6 ◽

2011 ◽

Vol 2 (1) ◽

pp. 6

Author(s):

Samuel Sunday Taiwo ◽

Titilope Bosede Bamigboye ◽

Osatohanmwen Odaro ◽

Olusegun Adelowo Adefioye ◽

Solomon Olufemi Fadiora

Keyword(s):

Staphylococcus Aureus ◽

Public Health Problem ◽

Disk Diffusion ◽

Major Public Health Problem ◽

Disk Diffusion Test ◽

Mueller Hinton ◽

Mueller Hinton Agar ◽

Vancomycin Resistant ◽

High Level ◽

Broth Dilution

The decreased vancomycin susceptibility and subsequent emergence of vancomycin resistant Staphylococcus aureus (VRSA) strains already multi-resistant to antibiotics is a major public health problem. In 2009, the Clinical and Laboratory Standards Institute (CLSI) altered its guidelines for vancomycin susceptibility testing in S. aureus and recent data suggests the possibility that VRSA may emerge more frequently than previously expected. Against this background, we conducted a study to ascertain the susceptibility status of clinical S. aureus isolates to vancomycin in our environment using vancomycin agar screen, disk diffusion and broth dilution methods. Of the total 49 S. aureus invasive strains isolated, 25 (51.0%) had vancomycin MIC of ≤2µg/ml by the CLSI standard broth dilution method and are classed as vancomycin susceptible; 18 (36.7%) had MIC of 4-8µg/ml (vancomycin intermediate resistant) and 6 (12.2%) had MIC of >256µg/ml (high level vancomycin resistant). Vancomycin agar screen with Mueller-Hinton agar containing 3µg/ml vancomycin (MHA-V3) correctly identified 20 of 25 (80%) vancomycin susceptible isolates; detected all 6 vancomycin resistant isolates and 16 of 18 (88.9%) vancomycin intermediate strains. Similarly, Mueller-Hinton agar containing 6µg/ml vancomycin (MHA-V6) correctly identified 23 of 25 (92%) vancomycin susceptible isolates and all 6 vancomycin resistant isolates but detected 14 (77.8%) of 18 vancomycin intermediate strains. Vancomycin disk diffusion test correctly identified all the 25 vancomycin susceptible S. aureus isolates giving 100% specificity but detected only 1 of 18 (5.6%) vancomycin intermediate and none (0%) of vancomycin resistant isolates. This result shows the occurrence of VISA and high level VRSA isolates in our environment, which contrary to current belief, may indicate widespread dissemination of VRSA. MHA-V3 agar is a useful alternative screening medium for vancomycin non-susceptibility detection in clinical S. aureus isolates but vancomycin disk diffusion is not useful in this regard.

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