Detection of accessory gene regulator groups genes and cassette chromosome mec types among Staphylococcus aureus isolated from intensive care unit patients

Determination of Virulence Factors and Resistance Profile of Methicillin-Resistant Staphylococcus aureus Strains among Different Types of spa, agr, and SCCmec

In order to restrict the spread of methicillin-resistant S. aureus (MRSA) in hospitals, it is necessary to characterize isolates rapidly and precisely. The objective of this study was to determine virulence factors and resistance profiles of MRSA strains among spa, agr, and SCCmec types. In total, 55 MRSA isolates were collected from clinical specimens. The MRSA isolates were characterized by antimicrobial susceptibility testing, virulence genes, agr typing, spa typing, and SCCmec typing. According to our findings, all MRSA strains were resistant to cefoxitin; 88% and 86.7% of which were resistant to erythromycin and clindamycin, respectively. Type II agr was predominant with 54.54% frequency. Among 27 different spa types, type t030 was most frequently (25.45%). Most MRSA isolates (63.3%) were SCCmec type III. The pvl and tst genes were found in 25.3% and 32.7% of MRSA isolates, respectively. Among the MRSA strains, ermA, ermB, and ermC were present in 50%, 33.3%, and 57.3% of cases, respectively. In addition, 43 of the 55 MRSA strains (78%) harbored aminoglycoside resistance genes. The results of our study revealed that the MRSA rate in our region is dramatically high. Better infection control guidelines in hospitals, as well as ongoing epidemiological surveillance studies, could be strongly suggested for effective prevention of the spread of MRSA to inpatients.

Molecular Characterization, Virulence Determinants, and Antimicrobial Resistance Profile of Methicillin-Resistant Staphylococcus aureus in the North of Iran; a High Prevalence of ST239-SCCmec III/t037 Clone

OBJECTIVES

Emergence and prevalence of methicillin-resistant Staphylococcus aureus (MRSA) have become a major universal health concern, limiting therapeutic options.

METHODS

A total number of 37 MRSA isolates, including 19 clinical isolates from hospitalized patients and 18 colonizing isolates from health care workers were identified from 3 hospitals, in Gorgan, North of Iran. Antimicrobial susceptibility test was performed using the disk diffusion method and E-test. The presence of virulence and antibiotic resistance determinants were evaluated by PCR. The genotypical characterization was further analyzed using multi-locus sequence, spa, staphylococcal cassette chromosome, mec (SCCmec), and agr typing.

RESULTS

The frequency of MRSA among S. aureus isolates was 38.14% (37/97). The most frequent S. aureus resistant isolates were found to be obstinate against penicillin (98%) and gentamicin (82.5%). Additionally, the lowest resistance rates were found against daptomycin (0%), vancomycin (2.7%), and quinupristin-dalfopristin (5.4%). All MRSA isolates were susceptible to daptomycin with minimum inhibitory concentration (MIC)50/MIC90 of 0.25/0.5 μg/mL. One isolate belonging to sequence type 239 (ST239)-SCCmecIII/t037 clone (MIC ≥16 μg/mL) was resistant to vancomycin. All but 1 isolate that shares ST22-SCCmec IV/t790 strain were positive for both tsst and pvl genes. The most predominant MRSA isolates (27%) were associated with ST239-SCCmec III/t037, and ST239-SCCmec III/t924 (16.2%) clones, subsequently. In our study, circulating MRSA strains were genetically diverse with a high prevalence of ST239-SCCmec III/t037 clone.

CONCLUSION

These findings emphasize the need for future and continuous surveillance studies on MRSA to prevent the dissemination of existing multidrug resistance MRSA clones in an effective manner.

Methicillin-resistant Staphylococcus aureus colonization of infectious and non-infectious skin and soft tissue lesions in patients in Tehran

Background

The most common clinical manifestations of Staphylococcus aureus strains in the community are skin and soft-tissue infections. S. aureus could colonize the body sites and complicate the pathogenesis of skin diseases. S. aureus colonization is a risk factor for severe conditions such as bone and joint infections, pneumonia, bacteremia, and endocarditis. This study aimed to investigate the prevalence of S. aureus strains in skin and soft tissue infections and other skin disorders in patients referring to dermatology clinics and to evaluate the antibiotic resistance pattern and molecular characteristics of S. aureus isolates.

Methods

Skin swabs were collected from the lesional sites in 234 outpatients referring to dermatology clinics in three hospitals in Tehran. Antibiotic susceptibility, biofilm formation, and hemolysis tests were performed for isolates. PCR was done for SCCmec typing, agr grouping, and virulence genes detecting.

Results

The prevalence of S. aureus strains among patients with skin and soft-tissue infections and other skin lesions was 44.77% (30/67) and 44.91% (75/167), respectively. Also, 59 (56.19%) isolates were MRSA, 35.57% were HA-MRSA, and 30.5% were CA-MRSA. The psmα gene was more prevalent (62.8%) among isolates, followed by hlaα (56.1%), tsst-1 (15.2%) eta (13.3%), etb (6.6%), and pvl (2.8%). The agr specificity groups I, II, III, and IV were identified in 49.5, 21.9, 11.4, and 14.2% of S. aureus isolates, respectively. Most (56%) S. aureus isolates produced a moderate biofilm, and 23.8% of them produced strong biofilms. α-hemolysin (46.6%), β-hemolysin (25.7%), γ-hemolysin (19%), and both α and β-hemolysin (5.7%) were also produced by isolates.

Conclusion

The present study results indicated high colonization of skin lesions by HA-MRSA and CA-MRSA clones; MRSA strains were more resistant to antibiotics, contained various toxin genes, and were able to form biofilms. Therefore, they could play a vital role in the pathogenesis of various skin diseases; also, they could spread and cause infections in other body sites. Eradication and decolonization strategies could prevent recurrent infections and the spread of resistant strains and improve skin conditions.

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.

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.

Presence of blaPER-1 and blaVEB-1 beta-lactamase genes among isolates of Pseudomonas aeruginosa from South West of Iran

Pseudomonas aeruginosa isolates have acquired resistance to antibiotics such as novel beta-lactams. The aim of this study was to investigate the bla_PER-1, bla_VEB-1, and bla_PSE-1 genes among isolates of P. aeruginosa among intensive care unit (ICU) patients. Sixty-five isolates were collected. The antibiotic susceptibility testing and combined disk tests were performed to detect the isolates producing extended spectrum beta-lactamases (ESBLs) among ceftazidime-resistant isolates. Polymerase chain reaction (PCR) amplification of bla_PER-1, bla_VEB-1, and bla_PSE-1 genes was conducted. Ten (15.3%) isolates were ESBL-positive, of which 40% (n = 4) belonged to males and 60% (n = 6) were collected from females. Moreover, two and one isolates harbored bla_PER-1 and bla_VEB-1 genes, respectively.