Detection of Panton-valentine Leukocidin Gene Isoforms of Staphylococcus aureus Isolates in Al-Zahra Hospital, Isfahan-Iran

Clonal diversity and genomic characterization of Panton-valentine Leukocidin (PVL)-positive Staphylococcus aureus in Tehran, Iran

Background

Some Staphylococcus aureus strains produce Panton-Valentine leukocidin (PVL), a bi-component pore-forming toxin, which causes leukocyte lysis and tissue necrosis. Currently, there is very limited information on the molecular epidemiology of PVL-encoding S. aureus strains in Iran. This study aimed to determine the molecular epidemiology and genetic background of PVL-positive S. aureus clinical strains isolated from Iranian patients.

Methods

A total of 28 PVL-positive S. aureus strains were detected from 600 S. aureus isolates between February 2015 and March 2018 from different hospitals in Tehran, Iran. Antimicrobial susceptibility testing was performed according to the Clinical and Laboratory Standards Institute (CLSI) guidelines. Molecular genotyping was performed using SCCmec and accessory gene regulator (agr) typing, PVL haplotyping, multilocus sequence typing (MLST), and pulsed-field gel electrophoresis (PFGE).

Results

The highest antibiotic resistance rate was found to be against erythromycin (57.1%), followed by ciprofloxacin (42.8%) and clindamycin (35.7%). Moreover, 19 (67.9%) out of 28 S. aureus isolates were identified as MRSA, including CA-MRSA (14/19, 73.7%) and HA-MRSA (5/19, 26.3%). SCCmec type IVa was detected as the predominant type (10/19, 52.6%), followed by type III (5/19, 26.3%) and type V (4/19, 21.1%). The agr type I was identified as the most common type (14/28, 50%), and H and R haplotype groups were observed at frequencies of 67.9 and 32.1%, respectively. Among H variants, the predominant variant was H2 (78/9%). The isolates encompassed 21 different sequence types (STs), including 16 new STs (ST5147 to ST5162). Based on eBURST analysis, the isolates were clustered into five CCs, including CC30, CC22, CC1, CC8, and CC5 (ST5160), and nine singletons. PFGE typing showed that 24 isolates were clustered into A (4 pulsotypes), B (9 pulsotypes), and C (11 pulsotypes) clusters.

Conclusions

A high prevalence of PVL-positive CA-MRSA strains was detected in Iran. The majority of PVL-positive isolates were of H (mostly H2) variant, while R variant was harbored by 100% of PVL-positive MRSA strains. Also, CC8, CC22, and CC30 were identified as the dominant clones among PVL-encoding S. aureus strains. This study promotes a better understanding of the molecular epidemiology and evolution of PVL-positive S. aureus strains in Iran.

Reduced Susceptibility to Chlorhexidine among Staphylococcus aureus Isolates in Israel: Phenotypic and Genotypic Tolerance

Antiseptic use for body decolonization is the main activity applied to prevent healthcare-associated infections, including those caused by S. aureus. Consequentially, tolerance to several antiseptics such as chlorhexidine gluconate (CHG) has developed. This study aimed to estimate the prevalence of CHG tolerance among S. aureus strains in Israel and to evaluate factors that may affect this tolerance. Furthermore, it tested the associations between phenotypic and genotypic CHG tolerance. S. aureus strains (n = 190) were isolated from clinical samples of patients admitted to various medical institutions in Israel. Phenotypic susceptibility to CHG was assessed by determining minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). Genotypic tolerance was detected using real-time PCR for detection of qac A/B genes. MIC for the antibiotic mupirocin was determined using the Etest method. Presence of the Panton-Valentine Leucocidin (pvl) toxin, mecA and mecC genes was detected using an eazyplex^® MRSAplus kit (AmplexDiagnostics GmbH, Gars, Germany). CHG tolerance was observed in 13.15% of the isolates. An association between phenotypic and genotypic tolerance to CHG was observed. Phenotypic tolerance to CHG was associated with methicillin resistance but not with mupirocin resistance. Additionally, most of the CHG-tolerant strains were isolated from blood cultures. In conclusion, this work shed light on the prevalence of reduced susceptibility to CHG among S. aureus strains in Israel and on the characteristics of tolerant strains. CHG-tolerant strains were more common than methicillin-resistant ones in samples from invasive infections. Further research should be performed to evaluate risk factors for the development of CHG tolerance.

Prevalence of PVL and LucED Genes in Methicillin-Resistant and Susceptible Isolates of Staphylococcus aureus Isolated from Burn Patients in Kermanshah, Iran

Background: The main pathogen causing various nosocomial infections, especially in burn patients, is Staphylococcus aureus. An important virulence factor of this bacterium is leukocidin, which binds to white blood cells and leads to apoptosis and necrosis. Objectives: In the present research, we aimed at investigating the prevalence of the panton-valentine leukocidin (PVL) and LucED genes in methicillin-susceptible and resistant isolates of S. aureus isolated from burn patients in Kermanshah, Iran. Methods: Overall, 73 isolates of S. aureus were collected from burn wounds and identified by specific biochemical tests. After determining the susceptibility patterns of the isolates by the disc diffusion method, the frequencies of the PVL and LucED genes were assessed using specific primers and polymerase chain reactions. Results: The rates of methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-susceptible Staphylococcus aureus (MSSA) isolates were 58.9% (43 isolates) and 41.1% (30 isolates), respectively. In MRSA isolates, the highest antibiotic resistance was to penicillin (100%) and gentamicin (81.4%). Moreover, the frequencies of the LucED and PVL genes were 76.7% (56 isolates) and 27.4% (20 isolates), respectively, and the highest frequency of the LucED and PVL genes was observed in MRSA (81.4%) and MSSA (40%) isolates, respectively. Conclusions: Increased multidrug resistance pattern among S. aureus isolates with leukocidin production has led to treatment failure and severe infections. The development of infections can be prevented by the identification of isolates carrying the leukocidin gene, and early detection of MRSA isolates is feasible by using the PVL gene.

Hospital clones of Panton-Valentine leukocidin-positive and methicillin-resistant Staphylococcus aureus circulating in the Tehran community

OBJECTIVES

The emergence of Panton-Valentine leukocidin (PVL)-positive Staphylococcus aureus has become a serious challenge in hospital and community settings. Therefore, this study was designed to determine the molecular characteristics and genetic relationship of PVL-positive S. aureus.

METHODS

A total of 116 S. aureus isolates were collected from outpatients and inpatients within 48 h after admission. For PVL-positive strains, antibiogram testing, toxin gene profile, agr grouping, SCCmec typing and genotyping by pulsed-field gel electrophoresis (PFGE) were performed.

RESULTS

Of 116 isolates, 13 (11.2%) harboured the PVL gene, 5 isolates (38.4%) were methicillin-resistant S. aureus (MRSA) with agr group I and SCCmec III. Of these, four strains were hospital-associated MRSA (HA-MRSA) that moved to the community and one strain was atypical community-associated MRSA (CA-MRSA), with characteristics of being PVL-positive, susceptible to all tested antibiotics, including clindamycin, with SCCmec III. This was recovered from a burn patient less than 24 h after the patient's admission and fulfilled the Centers for Disease Control and Prevention (CDC) criteria for CA-MRSA, except for the type of SCCmec. High diversity was found among PVL-positive strains by PFGE. All PVL gene-positive strains had hly and psms genes, but the tsst-1 gene was found just in methicillin-susceptible S. aureus (MSSA).

CONCLUSION

The results indicate that the distribution of the PVL gene in MSSA isolates was higher than in MRSA strains, and various PVL-positive resistant and virulent clones of HA-MRSA are circulating in the community. Therefore, implementing systematic surveillance is necessary for the evaluation of common PVL-positive S. aureus clones in the community.