scholarly journals Sequence heterogeneity of the PenA carbapenemase in clinical isolates of Burkholderia multivorans

2018 ◽  
Vol 92 (3) ◽  
pp. 253-258 ◽  
Author(s):  
Scott A. Becka ◽  
Elise T. Zeiser ◽  
Steven H. Marshall ◽  
Julian A. Gatta ◽  
Kevin Nguyen ◽  
...  
Keyword(s):  
Clinical Isolates ◽  
Burkholderia Multivorans ◽  
Sequence Heterogeneity

scholarly journals Exploring the Role of the Ω-Loop in the Evolution of Ceftazidime Resistance in the PenA β-Lactamase from Burkholderia multivorans, an Important Cystic Fibrosis Pathogen

2016 ◽  
Vol 61 (2) ◽  
Author(s):  
Krisztina M. Papp-Wallace ◽  
Scott A. Becka ◽  
Magdalena A. Taracila ◽  
Elise T. Zeiser ◽  
Julian A. Gatta ◽  
...  
Keyword(s):  
Amino Acid ◽  
Burkholderia Cepacia ◽  
Clinical Isolates ◽  
Dynamics Simulation ◽  
Single Amino Acid ◽  
Amino Acid Substitutions ◽  
Biochemical Basis ◽  
Content Type ◽  
Burkholderia Multivorans

ABSTRACT The unwelcome evolution of resistance to the advanced generation cephalosporin antibiotic, ceftazidime is hindering the effective therapy of Burkholderia cepacia complex (BCC) infections. Regrettably, BCC organisms are highly resistant to most antibiotics, including polymyxins; ceftazidime and trimethoprim-sulfamethoxazole are the most effective treatment options. Unfortunately, resistance to ceftazidime is increasing and posing a health threat to populations susceptible to BCC infection. We found that up to 36% of 146 tested BCC clinical isolates were nonsusceptible to ceftazidime (MICs ≥ 8 μg/ml). To date, the biochemical basis for ceftazidime resistance in BCC is largely undefined. In this study, we investigated the role of the Ω-loop in mediating ceftazidime resistance in the PenA β-lactamase from Burkholderia multivorans, a species within the BCC. Single amino acid substitutions were engineered at selected positions (R164, T167, L169, and D179) in the PenA β-lactamase. Cell-based susceptibility testing revealed that 21 of 75 PenA variants engineered in this study were resistant to ceftazidime, with MICs of >8 μg/ml. Under steady-state conditions, each of the selected variants (R164S, T167G, L169A, and D179N) demonstrated a substrate preference for ceftazidime compared to wild-type PenA (32- to 320-fold difference). Notably, the L169A variant hydrolyzed ceftazidime significantly faster than PenA and possessed an ∼65-fold-lower apparent Ki (Ki app) than that of PenA. To understand why these amino acid substitutions result in enhanced ceftazidime binding and/or turnover, we employed molecular dynamics simulation (MDS). The MDS suggested that the L169A variant starts with the most energetically favorable conformation (−28.1 kcal/mol), whereas PenA possessed the most unfavorable initial conformation (136.07 kcal/mol). In addition, we observed that the spatial arrangement of E166, N170, and the hydrolytic water molecules may be critical for enhanced ceftazidime hydrolysis by the L169A variant. Importantly, we found that two clinical isolates of B. multivorans possessed L169 amino acid substitutions (L169F and L169P) in PenA and were highly resistant to ceftazidime (MICs ≥ 512 μg/ml). In conclusion, substitutions in the Ω-loop alter the positioning of the hydrolytic machinery as well as allow for a larger opening of the active site to accommodate the bulky R1 and R2 side chains of ceftazidime, resulting in resistance. This analysis provides insights into the emerging phenotype of ceftazidime-resistant BCC and explains the evolution of amino acid substitutions in the Ω-loop of PenA of this significant clinical pathogen.

Molecular Characterisation of ESBL producer E. coli

2018 ◽  
Vol 1 (2) ◽  
pp. 40-57
Author(s):  
Abdulghani Alsamarai ◽  
Shler Khorshed ◽  
Imad Weli
Keyword(s):  
Urinary Tract Infection ◽  
Urinary Tract ◽  
Tract Infection ◽  
Female Student ◽  
Clinical Problem ◽  
Clinical Isolates ◽  
Molecular Characterisation ◽  
M Gene ◽  
Esbl Producer ◽  
E Coli

Background: Antibiotic resistance emerged as clinical problem challenge the effective treatment of infections. Virulence factor may play an important role in the influence of antimicrobial resistance. Objective: To determine the frequency of resistance gene in E. coli clinical isolates from women with urinary tract infection. Materials and Methods: Fifteen E.coli clinical isolates were tested by PCR to determine their molecular characterization. Results: The bla CTX –M gene was not detected in 6.7% out of the tested 15 E. coli clinical isolates from women with urinary tract infection. However, bla OXA gene was detected in all E. coli tested clinical isolates from pregnant women, female student and diabetic women with urinary tract infection. While bla TEM gene and bla SHV gene were not detected in 33.3% and 40% out of the tested E. coli clinical isolates respectively. Conclusions: Four types of ESBL genes were detected, and shows new trend of distribution, which indicated the predominance of OXA and CTX-M genes.

Assessment of the Multifactorial Effect on Antimicrobial Sensitivity in Positive Staphylococcus Aureus Clinical Isolates from Assir Region, Saudi Arabia

2012 ◽  
Vol 13 (2) ◽  
pp. 152-159 ◽  
Author(s):  
Nazar M Abdalla ◽  
Waleed O Haimour ◽  
Amani A Osman ◽  
Hassan Abdul Aziz
Keyword(s):  
Staphylococcus Aureus ◽  
Saudi Arabia ◽  
Culture Media ◽  
Meca Gene ◽  
Laboratory Data ◽  
Age Groups ◽  
Clinical Isolates ◽  
Diabetic Patients ◽  
Staph Aureus ◽  
Antimicrobial Sensitivity

General objectives: This study aimed at assessment of factors affecting antimicrobial sensitivity in Staphylococcus aureus clinical isolates from Assir region, Saudi Arabia. Materials and Methods: In this study, eighty one patients presented with Staph. aureus infections either nosocomial or community acquired infections were involved by collecting nasal swabs from them at Aseer Central Hospital General Lab. These patients were from all age groups and from males and females during the period of Jan 2011- Jun 2011. These samples were undergone variable laboratory procedures mainly; bactech, culture media, antibiotics sensitivity test using diffusion disc test (MIC) and molecular (PCR) for detection of mec A gene. Clinical and laboratory data were recorded in special formats and analyzed by statistical computer program (SPSS). Results: Showed that; Descriptive and analytical statistical analysis were performed and final results were plotted in tables. In Staph aureus MecA gene positive cases (50) showed: Oxacillin/ Mithicillin, Ciprofloxacin and Fusidin resistant in diabetic patients were 13, 26.0%, 9, 18% and 7, 14% respectively and in non diabetic patients were 37, 74.0%, 22, 44% and 20, 40% respectively. While no sensitivity in diabetic and non diabetic patients using Oxacillin/ Mithicillin. In Staph aureus MecA gene negative cases (31) showed: Oxacillin/ Mithicillin, sensitivity in diabetic patients (5, 16.1%) and in non diabetic were (26, 83.9%). While no resistant in diabetic and non diabetic patients. In Ciprofloxacin and Fusidin resistant in diabetic patients were 1, 3.2% and 1, 3.2% respectively and in non diabetic patients were 12, 38.7% and 7, 22.6%respectively. Erythromycin in Staph aureus ( MecA gene) positive cases (50) showed: resistant in age (0-15) years were (5, 10%), (16-50) years were (16, 32%) and ( ›50 years) were (12, 24%). Erythromycin in Staph aureus (MecA gene) negative cases (31) showed: resistant in age (0-15) years were (6, 19.3%), (16-50) years were (5, 16.1%) and ( ›50 years) were (3, 9.7%). Conclusion: Drugs resistance is a major progressive multifactorial problem facing the treatment of Staph aureus infections. DOI: http://dx.doi.org/10.3329/jom.v13i2.12750 J Medicine 2012; 13 : 152-159

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