Osong Public Health and Research Perspectives

Mohsen Mohammadi

3 Articles

Analysis of Resistance to Macrolide–Lincosamide–Streptogramin B Among mecA-Positive Staphylococcus Aureus Isolates: Mahmoud Khodabandeh, Mohsen Mohammadi, Mohammad Reza Abdolsalehi, Azadeh Alvandimanesh, Mehrdad Gholami, Meysam Hasannejad Bibalan, Abazar Pournajaf, Ramin Kafshgari, Ramazan Rajabnia; Osong Public Health Res Perspect. 2019;10(1):25-31. Published online February 28, 2019; DOI: https://doi.org/10.24171/j.phrp.2019.10.1.06

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Abstract PDF: Objectives
Genetic determinants conferring resistance to macrolide, lincosamide, and streptogramin B (MLS_B) via ribosomal modification such as, erm, msrA/B and ereA/B genes are distributed in bacteria. The main goals of this work were to evaluate the dissemination of MLS_B resistance phenotypes and genotypes in methicillin-resistant Staphylococcus aureus (MRSA) isolates collected from clinical samples.
Methods
A total of 106 MRSA isolates were studied. Isolates were recovered from 3 hospitals in Tehran between May 2016 to July 2017. The prevalence of MLS_B-resistant strains were determined by D-test, and then M-PCR was performed to identify genes encoding resistance to macrolides, lincosamides, and streptogramins in the tested isolates.
Results
The frequency of constitutive resistance MLS_B, inducible resistance MLS_B and MS_B resistance were 56.2%, 22.9%, and 16.6%, respectively. Of 11 isolates with the inducible resistance MLS_B phenotype, ermC, ermB, ermA and ereA were positive in 81.8%, 63.6%, 54.5% and 18.2% of these isolates, respectively. In isolates with the constitutive resistance MLS_B phenotype, the prevalence of ermA, ermB, ermC, msrA, msrB, ereA and ereB were 25.9%, 18.5%, 44.4%, 0.0%, 0.0%, 11.1% and 0.0%, respectively.
Conclusion
Clindamycin is commonly administered in severe MRSA infections depending upon the antimicrobial susceptibility findings. This study showed that the D-test should be used as an obligatory method in routine disk diffusion assay to detect inducible clindamycin resistance in MRSA so that effective antibiotic treatment can be provided.

A Novel PCR Assay for Detecting Brucella abortus and Brucella melitensis: Saeed Alamian, Majid Esmaelizad, Taghi Zahraei, Afshar Etemadi, Mohsen Mohammadi, Davoud Afshar, Soheila Ghaderi; Osong Public Health Res Perspect. 2017;8(1):65-70. Published online February 28, 2017; DOI: https://doi.org/10.24171/j.phrp.2017.8.1.09

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Abstract PDF: Objectives
Brucellosis is a major zoonotic disease that poses a significant public health threat worldwide. The classical bacteriological detection process used to identify Brucella spp. is difficult and time-consuming. This study aimed to develop a novel molecular assay for detecting brucellosis.
Methods
All complete sequences of chromosome 1 with 2.1-Mbp lengths were compared among all available Brucella sequences. A unique repeat sequence (URS) locus on chromosome 1 could differentiate Brucella abortus from Brucella melitensis. A primer set was designed to flank the unique locus. A total of 136 lymph nodes and blood samples were evaluated and classified by the URS-polymerase chain reaction (PCR) method in 2013–2014.
Results
Biochemical tests and bacteriophage typing as the golden standard indicated that all Brucella spp. isolates were B. melitensis biovar 1 and B. abortus biovar 3. The PCR results were the same as the bacteriological method for detecting Brucella spp. The sensitivity and specificity of the URS-PCR method make it suitable for detecting B. abortus and B. melitensis.
Conclusion
Quick detection of B. abortus and B. melitensis can provide the most effective strategies for control of these bacteria. The advantage of this method over other presented methods is that both B. abortus and B. melitensis are detectable in a single test tube. Furthermore, this method covered 100% of all B. melitensis and B. abortus biotypes. The development of this URS-PCR method is the first step toward the development of a novel kit for the molecular identification of B. abortus and B. melitensis.

Rapid Molecular Approach for Simultaneous Detection of Salmonella spp., Shigella spp., and Vibrio cholera: Reza Ranjbar, Ali Naghoni, Davoud Afshar, Farhad Nikkhahi, Mohsen Mohammadi; Osong Public Health Res Perspect. 2016;7(6):373-377. Published online December 31, 2016; DOI: https://doi.org/10.1016/j.phrp.2016.10.002

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Abstract PDF: Objectives
Gastrointestinal tract infection is still one of the serious public health problems in many geographic areas and is endemic in most countries including Iran. Early detection of the gastrointestinal tract pathogens can be extremely important. The aim of the current study was to apply a shortened time-multiplex polymerase chain reaction (PCR) for rapid and simultaneous detection of Salmonella spp., Shigella spp., and Vibrio cholera.
Methods
The standard and clinical strains of Salmonella spp., Shigella spp., and V. cholerae were used in the assay. Multiplex PCR was performed and optimized based on amplification of invA, putative integrase, and ompW genes for detecting Salmonella spp., Shigella spp., and V. cholerae, respectively. The specificity of the assay was evaluated by testing 12 different bacterial species.
Results
Only Salmonella spp., Shigella spp., and V. cholerae strains had positive results when subjected to the assay using multiplex PCR. The assay showed a high sensitivity, and no amplification products were observed in multiplex PCR with any of the other microorganisms.
Conclusion
Our study indicated that the invA, putative integrase, and ompW-based multiplex PCR assay appears to be an efficient method for rapid and simultaneous detection of Salmonella spp., Shigella spp., and V. cholerae.

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