Association of Panton Valentine Leukocidin (PVL) genes with methicillin resistant Staphylococcus aureus (MRSA) in Western Nepal: a matter of concern for community infections (a hospital based prospective study)

BACKGROUND: Methicillin resistant Staphylococcus aureus (MRSA) is a major human pathogen associated with nosocomial and community infections. Panton Valentine leukocidin (PVL) is considered one of the important virulence factors of S. aureus responsible for destruction of white blood cells, necrosis and apoptosis and as a marker of community acquired MRSA. This study was aimed to determine the prevalence of PVL genes among MRSA isolates and to check the reliability of PVL as marker of community acquired MRSA isolates from Western Nepal. METHODS: A total of 400 strains of S. aureus were collected from clinical specimens and various units (Operation Theater, Intensive Care Units) of the hospital and 139 of these had been confirmed as MRSA by previous study. Multiplex PCR was used to detect mecA and PVL genes. Clinical data as well as antimicrobial susceptibility data was analyzed and compared among PVL positive and negative MRSA isolates. RESULTS: Out of 139 MRSA isolates, 79 (56.8 %) were PVL positive. The majority of the community acquired MRSA (90.4 %) were PVL positive (Positive predictive value: 94.9 % and negative predictive value: 86.6 %), while PVL was detected only in 4 (7.1 %) hospital associated MRSA strains. None of the MRSA isolates from hospital environment was found positive for the PVL genes. The majority of the PVL positive strains (75.5 %) were isolated from pus samples. Antibiotic resistance among PVL negative MRSA isolates was found higher as compared to PVL positive MRSA. CONCLUSION: Our study showed high prevalence of PVL among community acquired MRSA isolates. Absence of PVL among MRSA isolates from hospital environment indicates its poor association with hospital acquired MRSA and therefore, PVL may be used a marker for community acquired MRSA. This is first study from Nepal, to test PVL among MRSA isolates from hospital environment. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s12879-016-1531-1) contains supplementary material, which is available to authorized users

Threat of multidrug resistant Staphylococcus aureus in Western Nepal

Objective: To determine the prevalence of methicillin resistant Staphylococcus aureus (MRSA) and antimicrobial susceptibility patterns of the isolates from Manipal Teaching Hospital, Pokhara, Nepal. Methods: This study was conducted over a period of 11 months (September 2012–August 2013) at the Manipal Teaching Hospital, Pokhara, Nepal. A total of 400 isolates were collected from various clinical specimens including hospital units (operation theaters and intensive care units). Antibiotic susceptibility testing was performed by Kirby-Bauer disc diffusion method. Primary screening for MRSA was performed using disc diffusion test by cefoxitin (30 μg) and oxacillin (1 μg) disc, further confirmation was done by detection of mecA gene using PCR. Results: Out of 400 Staphylococcus aureus strains, 139 (34.75%) were found to be MRSA. Among the MRSA isolates, 74 (53.2%) were from inpatient departments, 58 (41.7%) of the isolates were from outpatients and 7 (5.0%) isolates were from hospital units (operation theaters and intensive care units). Majority of MRSA (73.38%) isolates were multidrug resistant while less than 15% were resistant to amikacin, clindamycin and tetracycline. None of the isolate was resistant to vancomycin. Inducible clindamycin resistance was found in 54 (25.47%) isolates. Conclusions: This study showed a high prevalence of MRSA in our hospital. There is need of regular surveillance of antibiotic resistance, standardization of laboratory methods for detecting methicillin resistance and performing antibiotic susceptibility testing in developing countries like Nepal. Hospital acquired infections including prevalence of MRSA can be minimized by appropriate hygienic measures in patient care and management and by antibiotic stewardship. Screening of erythromycin resistant isolates would minimize clinical failures associated with clindamycin therapy

Maximum clade credibility phylogenetic tree based on 67 Arctic-related RABV N gene sequences.

<p>The horizontal branches are drawn to a scale of estimated year of divergence. Upper and lower limits of the 95% highest posterior density (HPD) estimates, and the corresponding divergence dates for the selected nodes are shown. Posterior probability values are shown above the branch for relevant key nodes only. Isolates for which the complete N gene sequence was obtained in this study are indicated by an asterisk.</p

A: Magnified phylogeny of the Indian subcontinent clade.

<p>B: Magnified phylogeny of the Arctic-like 1 and 3 sub-clades. Branches are labeled with bootstrap values generated with both the neighbor-joining (1,000 bootstrap replications) and maximum likelihood (100 bootstrap replications, number in brackets) algorithms. Bootstrap values are given for selected relevant nodes only. A scale indicating genetic distance is presented by the horizontal bar. Designations of the different RABV phylogroups (clade, sub-clade and lineage) are as indicated, based on previously defined assignments <a href="http://www.plosntds.org/article/info:doi/10.1371/journal.pntd.0002560#pntd.0002560-Bourhy1" target="_blank">[5]</a>, <a href="http://www.plosntds.org/article/info:doi/10.1371/journal.pntd.0002560#pntd.0002560-Kuzmin1" target="_blank">[25]</a>. Isolates for which the complete N gene sequence was obtained in this study are indicated by an asterisk with the viruses from Nepal underscored.</p

Clade specific amino acid differences in the glycoprotein of Nepalese RABV.

a<p>Amino acid positions exclude the 19aa signal peptide sequence.</p>b<p>Virus samples 3878-09 and 3878-78 have the Indian subcontinent residue.</p>c<p>Virus samples 3878-09 and 3878-78 have Thr substitution.</p>d<p>Virus sample 3878-78 has the Indian subcontinent residue.</p

Maximum likelihood phylogenetic tree based on 173 complete RABV N gene nucleotide sequences.

<p>Branches are labeled with bootstrap values generated with both the neighbor-joining (1,000 bootstrap replications) and maximum likelihood (100 bootstrap replications, number in brackets) algorithms. Bootstrap values are given for selected relevant nodes only. A scale indicating genetic distance is presented by the horizontal bar. Designations of the different RABV phylogroups (clade, sub-clade and lineage) are as indicated, based on previously defined assignments <a href="http://www.plosntds.org/article/info:doi/10.1371/journal.pntd.0002560#pntd.0002560-Bourhy1" target="_blank">[5]</a>, <a href="http://www.plosntds.org/article/info:doi/10.1371/journal.pntd.0002560#pntd.0002560-Kuzmin1" target="_blank">[25]</a>. Isolates for which the complete N gene sequence was obtained in this study are indicated by an asterisk with the viruses from Nepal underscored.</p

Clade specific amino acid differences in the nucleoprotein of Nepalese RABV.

a<p>Excludes virus sample 3878-10 which adopts Val at position 179.</p