Genetic Characterization of Methicillin Resistant and Sensitive, Vancomycin Intermediate Staphylococcus aureus Strains Isolated from Different Iranian Hospitals

Phenotypic and genotypic characterization of Staphylococcus aureus strains isolated from otitis externa: Emergence of CC30-spa t019-SCCmec IV carrying PVL as major genotype

The increasing emergence of Staphylococcus aureus as the primary causative agent of otitis externa has been noted; however, detailed information regarding the molecular characteristics of these strains in Iran remains scarce. The current study aims to investigate both genotypic and phenotypic attributes of S. aureus strains implicated in ear infections. In the present work, we analyzed 60 S. aureus strains isolated from cases of otitis externa over a period of 45 months. The resistance patterns were determined using disk diffusion and microbroth dilution methods. All S. aureus isolates were confirmed by the nucA polymerase chain reaction assay, and their biofilm production was assessed by a microtiter plate assay. Molecular characterization of the isolates was performed using the staphylococcal cassette chromosome mec, multilocus sequence typing, and staphylococcus protein A typing methods. Overall, the results indicated that 44 out of 60 S. aureus isolates (73.3 %) were methicillin-resistant Staphylococcus aureus. Resistance to mupirocin and vancomycin was observed in 13.3 % and 1.7 % of the tested isolates, respectively. Furthermore, out of the 60 S. aureus isolates, 56 strains (93.4 %) were classified as positive biofilm strains at different levels. Twelve distinct clonal lineages were identified. The vast majority of S. aureus isolates belonged to CC30/ST30-MRSA IV/t019 (41.7 %). Among the 31 strong biofilm producers, the majority (64.5 %) belonged to CC30/ST30-MRSA IV/t019 clone. Biofilm negative isolates belonged to CC22/ST22 (2 isolates), CC8/ST585 (one isolate), and CC8/ST8 (one isolate). Our result revealed that about three-quarters of PVL-positive strains belonged to CC30/ST30. Our data confirmed the presence of MSSA strains among CC30/ST30 and CC22/ST22 isolates. The mupirocin resistant isolates (n = 8) belonged to CC8/ST585-MRSA III/t713 (37.5 %), CC8/ST239-MRSA III/t030 (25 %), CC8/ST8-MRSA IV/t008 (12.5 %), CC8/ST239-MRSA III/t037 (12.5 %), and CC22/ST22-MRSA IV/t790 (12.5 %) lineages. The VRSA strain belonged to the CC8/ST8-MRSA IV/t008 lineage, carrying the vanA determinant. iMLSB phenotypes (n = 14) were distributed across different lineages, including CC30/ST30-MRSA IV/t019 (21.5 %), CC30/ST30-MSSA/t021 (21.5 %), CC22/ST22-MSSA/t005 (14.3 %), CC8/ST239-MRSA III/t030 (14.3 %), CC22/ST22-MSSA/t1869 (7.1 %), CC22/ST22-MRSA IV/t790 (7.1 %), CC8/ST239-MRSA III/t037 (7.1 %), and CC1/ST772-MRSA IV/t10795 (7.1 %). These findings highlight significant genotypic diversity and high biofilm formation among our isolates. The frequent occurrence of the CC/ST30 clone in S. aureus strains isolated from otitis externa reflects the emergence of these lineages as a predominant clone in Iran, posing a significant public health concern.

Hospital-Related Lineage of USA300 Methicillin-Resistant Staphylococcus aureus (MRSA) to Cause Bacteremia in Iran

Staphylococcus aureus is an important pathogen that causes bloodstream infections. This study is aimed at assessing the genotypic characteristics of S. aureus strains responsible for bloodstream infections. An epidemiological study was conducted using 85 S. aureus strains isolated from bloodstream infections. Susceptibility was tested using the broth microdilution method and disk diffusion. All detected methicillin-resistant S. aureus (MRSA) isolates were confirmed by mecA PCR assays. S. aureus isolated from bacteremia were characterized using SCCmec, spa, and multilocus sequence typing methods. The prevalence of S. aureus strains responsible for bloodstream infections was 38.8%. All isolates were MRSA. Multidrug resistance (MDR) was present in 84.7% of isolates. MRSA isolated categorized within six clonal complexes including CC8 (60%), CC22 (22.4%), CC5 (5.9%), CC30 (4.7%), CC45 (4.7%), and CC59 (2.3%). The main lineages found were USA300/CC8-MRSA-IV/t008 (41.2%), followed by ST22-SCCmecIV/t790 (9.4%), ST239-SCCmecIII/t037 (7.1%), ST22-SCCmecIV/t032 (7.1%), ST239-SCCmecIII/t631 (5.9%), ST239-SCCmecIII/t860 (5.9%), ST22-SCCmecIV/t852 (5.9%), ST5-SCCmecIV/t002 (4.7%), ST45-SCCmecIV/t038 (4.7%), ST30-SCCmecIV/t318 (4.7%), ST59-SCCmecIV/t437 (2.3%), and ST225-SCCmecII/t045 (1.1%). Resistance to vancomycin amounted to 5.9% of isolates that belonged to ST239-SCCmecIII/t037 (80%) and ST8-SCCmecIV/t008 (20%). The emergence of USA300 strains in bloodstream infections in our country is a serious alarm and highlights the significant invasion of this lineage into the healthcare system. MDR patterns among these strains appear to be becoming the biggest problem in healthcare treatment.

Mupirocin-Resistant Staphylococcus aureus in Iran: A Biofilm Production and Genetic Characteristics

The spread of mupirocin-resistant Staphylococcus aureus strains in hospitals and communities is a universal challenge. Limited data is available on the genetic features of high-level mupirocin resistant- (HLMUPR-) S. aureus isolates in Tehran. In the present research, we investigated 48 high-level mupirocin resistance S. aureus by antimicrobial activity, virulence analysis, biofilm formation, multilocus sequence typing (MLST), and staphylocoagulase (SC) typing. All the HLMUPR strains were positive for mupA gene. The frequency of multidrug resistance was 97.9%. Twenty-one (43.8%) were toxinogenic with 14 producing pvl (29.2%), 5 tst (10.4%), and two eta (4.2%). Among the HLMUPR isolates, biofilm production was detected in 45 (89.6%) isolates with complete dominance clfB, clfA genes, and a noticeably high frequency fnbA (95.8%), followed by fnbB (93.8%), eno and icaD (each 83.3%), sdrC (81.3%), ebps (79.2%), icaA (75%), sdrD (66.7%), fib (60.4%), sdrE (50%), cna (41.7%), and bap (4.2%). Coagulase typing distinguished isolates into four genotypic patterns including III (50%), II (27.1%), and type IVa (22.9%). A total of three clonal complexes (CCs) and 4 sequence types (STs) including CC/ST22 as the most prevalent (52.1%), CC8/ST239 (20.8%), CC/ST8 (16.7%), and CC/ST5 (10.4%) were identified in current work. According to our analysis, nonbiofilm producer isolates belonged to CC8/ST239 (6.3%) and CC/ST8 (4.2%). Fusidic acid-resistant isolates belonged to CC/ST45 (n = 3) and CC8/ST239 (n = 1). Observations highlighted the circulation of the CC/ST22 HLMUPR S. aureus strains with strong biofilm-production ability in our hospitals, indicating the possibility of transmission of this type between community and hospital.

Isolation and Genetic Characterization of Vancomycin-resistant and mecC+ Methicillin-resistant Staphylococcus aureus Strains in Clinical Samples of Bojnurd, Northeastern Iran

Background: The emergence of antibiotic-resistant Staphylococcus aureus strains is one of the major concerns about the various staphylococcal infections. Vancomycin is one the most important effective antibiotics on staphylococcal lethal infections. To date, vancomycin-resistant strains are increasingly isolated in different parts of the world, and it is alerting. Objectives: The current study was designed to evaluate the prevalence, and antibiotic susceptibility pattern of methicillin-resistant S. aureus (MRSA) and vancomycin-resistant S. aureus (VRSA) isolates in the main tertiary hospital of Bojnurd, Iran. Methods: Staphylococcus aureus isolates were collected from different clinical samples in Imam Reza Hospital of Bojnurd. After identification of isolates through using conventional methods, they were evaluated by agar screening, disk diffusion, and minimum inhibitory concentration (MIC) methods to determine resistance to vancomycin and methicillin. We also performed polymerase chain reaction (PCR) for the detection of mecA, mecC, vanA, and vanB genes. After confirmation of vancomycin resistance, genetic analysis was performed using SCCmec, agr, and spa typing, and multilocus sequence typing (MLST) methods on VRSA isolates. Results: We found four vancomycin-resistant isolates (1.29%). Also, 75% of isolates were resistant to cefoxitin. Using the PCR method, mecA was found in 73%, mecC in 0.64%, and vanA in 1.29% of isolates. Interestingly, we found two mecC positive isolates in MRSA isolates. The alpha-hemolysin (81.81%) and enterotoxin C (27%) had the highest and lowest toxins percentage, respectively. Among mecA positive isolates, SCCmec IV (37%), SCCmec III (31.27%), SCCmec I (14%), SCCmec II (11%), and SCCmec V (5.7%) were the most prevalent SCCmec types, respectively. It should be noted that the two mecC positive isolates belonged to SCCmec XI. Agr I (76.29%) was the highest agr type. We recognized t037 as the dominant spa type, and ST239, ST6, ST97, and ST8 were found in VRSA isolates. Conclusions: In our study, the frequency of mecA genes in MRSA isolates was very high. It seems that the resistant isolates belonged to endemic clones of Iran.

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.

The prevalence of drug-resistant and virulent Staphylococcus spp. in a municipal wastewater treatment plant and their spread in the environment

Drug-resistant and pathogenic Staphylococcus spp. strains can reach surface waters and air with wastewater evacuated to the environment. These strains increase the environmental pool of genetic determinants conferring antibiotic resistance and virulence, and constitute a health risk for the employees of wastewater treatment plants (WWTP) who come into daily contact with bioaerosols. The aim of this study was to identify the genetic determinants of drug resistance and virulence in Staphylococcus spp. strains isolated from untreated (UWW) and treated wastewater (TWW), an activated sludge (AS) bioreactor, river water collected upstream and downstream from the wastewater discharge point (URW and DRW), and WWTP employees. All isolates were analysed for the presence of the rpoB gene, and were subjected to clonal analysis by ERIC fingerprinting. As a result, 249 of the 455 analysed isolates were selected for PCR. The presence of the gene encoding nuclease activity in S. aureus (nuc), the methicillin resistance gene (mecA), vancomycin resistance gene (vanA), antiseptic resistance gene (qacA/B) and virulence genes (sasX, pvl, tst1, hla, sec) was determined. The prevalence of nuc, mecA, vanA and qacA/B genes in wastewater and river water was determined by quantitative PCR (qPCR). In the group of strains isolated from wastewater and water samples, 63% were identified as S. aureus, and 20% of the strains carried the vanA gene. The hla virulence gene was present in 80% of the isolates, and the pvl gene was detected in 27% of the isolates. In the group of strains isolated from the employees, 82% were identified as S. aureus, and the presence of vanA and mecA genes was confirmed in 14% and 16% of the isolates, respectively. The most prevalent virulence gene was hla (74%), whereas pvl was observed in 43% of the isolates. The quantitative analysis revealed the highest concentrations of the studied genes in UWW samples, at 2.56x10⁴ gene copies/ml for nuc, 1.18x10³ gene copies /ml for mecA, 8.28x10⁵ gene copies /ml for vanA and 3.83x10⁵ gene copies /ml for qacA/B. Some of analysed genes were identified in the isolates from both URW and DRW samples, as well as in genomic DNA of these samples. These results indicate that wastewater is not effectively treated in the analysed WWTP, which could contribute to the dissemination of antibiotic resistance genes (ARGs) and antibiotic-resistant bacteria (ARB) to the environment. An analysis of the genetic relatedness of selected isolates revealed clusters of strains originating from UWW samples, AS samples and the employees. These observations suggest that ARGs and ARB are transmitted by wastewater bioaerosols to the upper respiratory tract mucosa of the plant's employees, thus increasing their exposure to infectious factors.

The Nasal Carriage of Coagulase-Negative Staphylococci Among Animals and Its Public Health Implication

Background: The research scope toward nasal colonization of coagulase-negative staphylococci (CoNS) in animals is largely ignored for many years. Therefore, this study was conducted to investigate the nasal carriage of CoNS among different animals and its public health implication. Materials and Methods: Nasal swabs were gathered from 152 animals (36 cats, 31 dogs, 29 sheep, 32 goats, and 24 cattle). These samples were subjected for isolation and identification of CoNS by conventional bacteriological methods, then molecular confirmation was carried out using Staphylococcus genus-specific 16S rRNA PCR. All CoNS isolates were screened for the presence of antibiotic resistance (mecA and blaZ) and virulence (lukS/F-PV and tsst-1) genes. Moreover, strains carrying resistance and/or virulence genes were identified to species level by 16S rRNA gene sequencing approach. Results: CoNS were identified in 14.5% (22/152) of the examined animals, whereas the prevalence rates among different animals were 27.8%, 3.2%, 8.3%, 10.3%, and 18.8% for cats, dogs, cattle, sheep, and goats, respectively. Of all isolates, two strains (Staphylococcus epidermidis and Staphylococcus warneri) harbored mecA gene, which carried on staphylococcal cassette chromosome mec type I in S. epidermidis and type V in S. warneri, while blaZ gene has been found in one strain (Staphylococcus felis). Importantly, two isolates (S. epidermidis and S. felis) had tsst-1 gene but all of CoNS isolates were negative for Panton-Valentine leukocidin gene. The phylogenetic analysis of the obtained sequences of CoNS of the current study revealed high similarity to those of serious human clinical cases to underscore the public health significance of such isolates. Conclusion: The nasal carriage of antibiotic-resistant and toxigenic CoNS among different animals highlights the potential zoonotic link with great public health implication.

Global prevalence and distribution of vancomycin resistant, vancomycin intermediate and heterogeneously vancomycin intermediate Staphylococcus aureus clinical isolates: a systematic review and meta-analysis

Vancomycin-resistant Staphylococcus aureus (VRSA), Vancomycin-intermediate S. aureus (VISA) and heterogeneous VISA (hVISA) are subject to vancomycin treatment failure. The aim of the present study was to determine their precise prevalence and investigate prevalence variability depending on different years and locations. Several international databases including Medline (PubMed), Embase and Web of Sciences were searched (data from 1997 to 2019) to identify studies that addressed the prevalence of VRSA, VISA and hVISA among human clinical isolates around the world. Subgroup analyses and meta-regression were conducted to indicate potential source of variation. Publication bias was assessed using Egger's test. Statistical analyses were conducted using STATA software (version 14.0). Data analysis showed that VRSA, VISA and hVISA isolates were reported in 23, 50 and 82 studies, with an overall prevalence of 1.5% among 5855 S. aureus isolates, 1.7% among 22,277 strains and 4.6% among 47,721 strains, respectively. The overall prevalence of VRSA, VISA, and hVISA before 2010 was 1.2%, 1.2%, and 4%, respectively, while their prevalence after this year has reached 2.4%, 4.3%, and 5.3%. The results of this study showed that the frequency of VRSA, VISA and hVISA after 2010 represent a 2.0, 3.6 and 1.3-fold increase over prior years. In a subgroup analysis of different strain origins, the highest frequency of VRSA (3.6%) and hVISA (5.2%) was encountered in the USA while VISA (2.1%) was more prevalent in Asia. Meta-regression analysis showed significant increasing of VISA prevalence in recent years (p value ≤ 0.05). Based on the results of case reports (which were not included in the calculations mentioned above), the numbers of VRSA, VISA and hVISA isolates were 12, 24 and 14, respectively, among different continents. Since the prevalence of VRSA, VISA and hVISA has been increasing in recent years (especially in the Asian and American continents), rigorous monitoring of vancomycin treatment, it's the therapeutic response and the definition of appropriate control guidelines depending on geographical regions is highly recommended and essential to prevent the further spread of vancomycin-resistant S. aureus.

Characterization of SCCmec, Spa Types and Multidrug Resistant of Methicillin-Resistant Staphylococcus aureus Isolates in Ahvaz, Iran

Background

Methicillin-resistant Staphylococcus aureus (MRSA) is one of the most pathogens associated with health care. Molecular typing methods are vital for outbreak investigations of MRSA. The aim of this study was characterization of SCCmec, spa types and multidrug resistant of methicillin-resistant Staphylococcus aureus isolates in Ahvaz, Iran.

Methods

A total of 50 MRSA isolates were determined by using the phenotypic method and mecA gene. Antibiotic resistance profile and SCCmec types were screened using disc diffusion method and PCR, respectively. For spa typing of MRSA isolates, two molecular typing methods including the PCR-sequencing and high-resolution melting (HRM) analysis were used.

Results

In the present study, the highest sensitivity of MRSA was to vancomycin and linezolid and the lowest to clindamycin. In the MRSA isolates, 22% were XDR and 78% were MDR. SCCmec type III was found commonly among MRSA. Based on PCR-sequencing and HRM results, 10 different spa types were identified. The spa types t037 and t030 were the most common in this study.

Conclusion

This study emphasizes the spa variation among MRSA isolates, which may be considered as an important criterion when treating staphylococcal infections. Accurate and early detection of MDR, XDR, or even PDR MRSA isolates strains must be commenced by all clinical microbiology laboratories to reduce the menace of antimicrobial resistance.

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.

Molecular Characterization of Community-Associated Methicillin-Resistant Staphylococcus aureus in Iranian Burn Patients

Background & Objective:

Methicillin-resistant Staphylococcus aureus (MRSA) is reported as one of the important bacterial causes of burn wound infections. This study was carried out to investigate molecular characterization of community-associated MRSA (CA-MRSA) isolated from Iranian burn patients.

Methods:

A total of 31 isolates of S. aureus were collected from the Motahari Burns Hospital (Tehran, Iran) in 2016. All isolates were collected from outpatients and inpatients within 48 hours of admission. The mecA, pvl, tsst-1, hla-α, and psmα genes detecting, SCCmec, agr and PFGE typing were done.

Results:

A total of 13 (41.9%) isolates were cefoxitin-resistant and mecA-positive, which were considered as MRSA. The SCCmec typing MRSA strains revealed type II in 1 (7.7%), type III in 9 (69.2%), and other types in 3 isolates (23.7%) cases. The agr typing of all 31 isolates showed that 14 (45.2%), 1 (3.2%), 6 (19.4%), and 10 (32.3%) strains belonged to agr groups 1, 3, 4, and unknown type, respectively. The pvl, tsst-1, hla-α, and psmα genes were positive in 3 (9.7%), 4 (12.9%), 21 (67.7%), and 31 (100%) isolates, respectively. Considering the cut-off values of ≥50%, 3 groups of related isolates (cluster A1, B1, and C1) in PFGE study were observed.

Conclusion:

The MRSA strains of this study were initially isolated as Community-associated S. aureus (CA-MRSA); however molecular characterization showed that a significant proportion of them had hospital-associated MRSA (HA-MRSA) features. Therefore, it is likely that the HA-MRSA strains are spread among the community.

Genetic Diversity Analysis of Methicillin-resistant Staphylococcus aureus Strains Isolated from Intensive Care Unit in Iran

Objectives

Staphylococcus aureus has emerged as a major public health concern. It is a common pathogen in high-risk hospital intensive care units (ICUs). We analyzed the molecular characteristics on the SCCmec and spa genes of S. aureus isolates gathered from ICUs. The antibiotic resistance patterns and carriage of resistance and virulence determinants were also identified.

Methods

In this cross-sectional study, 84 non-duplicated S. aureus strains isolated from ICU patients in were genotyped using SCCmec and spa typing. The Kirby-Bauer disk diffusion and micro-broth dilution methods were used to determine resistance patterns. Virulence and resistance gene profiling were also determined using the polymerase chain reaction technique.

Results

All isolates were methicillin-resistant S. aureus and belonged to seven spa types: t388 (36.9%), t852 (14.3%), t924 (13.1%), t790 (11.9%), t064 (10.7%), t037 (9.5%), and t084 (3.6%). They differed in the carriage of resistance and toxin genes. The most common SCCmec type was III detected in 50 isolates (59.5%), followed by type IV in 34 isolates (40.5%). The pvl gene was detected in 14.3% (n = 12) of isolates, of which 66.7% (n = 8) belonged to t852 and 33.3% (n = 4) belonged to t790. Among the tested strains, 9.5% (n = 8) carried the mupA gene and belonged to the t064 spa type.

Conclusions

The data revealed a high resistance rate to antibiotics, which could be a threat to ICU patients. It is necessary to detect antimicrobial resistance and resistance and toxin-encoding of gene profiles in different molecular types.

Genetic Diversity Analysis of Mupirocin-Resistant Staphylococcus aureus Clinical Isolates in Tehran Hospitals, Iran

Few studies describe the molecular characterization of mupirocin resistance in Staphylococcus aureus strains. In this study, we evaluated the characteristics of mupirocin resistance in S. aureus isolates for 1-year period in Tehran, Iran. In a cross-sectional study, we collected 51 unique mupirocin-resistant strains obtained from 648 S. aureus isolates. High- and low-level resistance were determined by minimum inhibitory concentration with broth microdilution method. Presence of the genes for resistance to antibiotics and toxins was detected by polymerase chain reaction assays. Genotyping was performed by S. aureus protein A (spa) and staphylococcal cassette chromosome mec (SCCmec) typing, whereas clones were determined by multilocus sequence typing. Among mupirocin-resistant isolates, methicillin-resistant S. aureus (MRSA) 23 (45.1%) and 28 (54.9%) isolates were classified as high- and low-level mupirocin resistance, respectively. Among the 51 tested strains 25 (49%) isolates were positive for mupA genes. Seven different clones were detected in this study. High-level mupirocin-resistant (HLMUPR) strains belonged to ST8-SCCmec IV/t064 (n = 10, 19.6%), ST5-SCCmec IV/t002 (n = 5, 9.8%), ST8-SCCmec IV/t008 (n = 4, 7.8%), and ST239-SCCmec III/t631 (n = 4, 7.8%) clones, while low-level mupirocin-resistant (LLMUPR) strains belonged to ST22-SCCmec IV/t790 (n = 11, 21.6%), ST239-SCCmec III/t860 (n = 9, 17.7%), and ST15-SCCmec IV/t084 (n = 8, 15.7%) clones. Two strains belonged to ST22-SCCmec IV/t790 clone, despite carrying mupA gene, and demonstrated LLMUPR phenotype. One ST8-SCCmecIV/t008 strain with HLMUPR was confirmed as Vancomycin-intermediate S. aureus strain. Our data demonstrated the need for thorough epidemiological monitoring and a routine mupirocin testing program to prevent and detect mupirocin resistance in MRSA.

Molecular Characterization of Methicillin-Resistant Staphylococcus aureus Isolates, Isolated from a Burn Hospital in Southwest Iran in 2006 and 2014

OBJECTIVES

Incidence of methicillin-resistant Staphylococcus aureus (MRSA) is increasing every year, especially in burn patients with a high rate of morbidity and mortality. Molecular and epidemiologic studies are useful practices for understanding the relatedness of isolates in a single patient or a hospital. This study aimed at determining molecular characterizations of isolates collected in 2006 and 2014 using S. aureus-specific staphylococcal protein A (Spa) typing and Multilocus Sequence Typing (MLST) methods.

MATERIALS AND METHODS

Totally, 71 MRSA isolates were collected during the last two studies (2006 and 2014) from burn patients at Taleghani Burn Centre. After confirmation, all isolates were analysed using MLST and Spa typing methods.

RESULTS

We reported the emergence of Spa type t021, ST-30-IV MRSA isolates, which were PVL-positive in 14.6% of the cases and t12366, ST-8-IV isolates, which were PVL-negative in 9.8% of the cases. In 2014 study, Spa typing of MRSA isolates revealed five different spa types. Overall, in two studies, t037, ST-239, SCCmec III, and CC8 were predominant clones and they were reported in 63% of the cases.

CONCLUSION

The predominance of ST-239 in this region during the last eight years is a major concern. It also has a disturbing impact on the management of staphylococcal infections. Moreover, the SCCmec type IV strain is able to disseminate rapidly in hospital environments, demanding an improvement in infection-control policy.

Molecular characterization of vancomycin-resistant Staphylococcus aureus strains isolated from clinical samples: A three year study in Tehran, Iran

Introduction

Emergence of vancomycin-intermediate Staphylococcus aureus (VISA) and vancomycin-resistant S. aureus (VRSA) strains has led to great concern in global public health in both developing and developed countries. This study investigated distribution and molecular characterization of VRSA strains in Tehran’s hospitals using a combination of molecular typing methods.

Materials and methods

A total of 1789 S. aureus isolates obtained between 2014 and 2017 and were characterized using antibiogram, SCCmec typing, spa typing, and multilocus-sequence typing. Resistance to vancomycin was determined by E-test method. After confirmation of the isolated VRSA strain, genetic analysis was performed by evaluating vanA and vanB genes presence.The presence of resistance (ermA, ermB, ermC, mupA, msrA, msrB, tetM, ant (4΄)-Ia, aac (6΄)-Ie/aph (2˝), aph (3΄)-IIIa) and toxin (etb, eta, pvl, tst) encoding genes was investigated by the polymerase chain reaction (PCR) technique.

Results

Of all S. aureus tested isolates, four isolates were confirmed as VRSA isolates and two isolates confirmed as VISA isolates. ST5- SCCmec II/t002 and ST239-SCCmec III/t037 strains had MIC values of 512μg/ml, ST239-SCCmec III/t037 and ST8-SCCmecIV/t008 strains had MIC values of 64μg/ml and ST22-SCCmec IV/t790 and ST239-SCCmec III/t030 strains had MIC values ≥ 8 μg/ml. pvl-encoding gene was confirmed in ST8-SCCmecIV/t008 and ST22-SCCmec IV/t790 strains. The isolates differed in the carriage of resistance and toxin encoding genes.

Conclusions

The study revealed the existence of VRSA strains in capital of Iran, Tehran. To our knowledge, this is the first report of ST239-SCCmec III/t037 as VRSA strain. These findings support the need for future surveillance studies on VRSA strains to keep the emergence and transmission of these isolates to a minimum.

Methicillin-Resistant Staphylococcus aureus Isolated From Various Types of Hospital Infections in Pediatrics: Panton-Valentine Leukocidin, Staphylococcal Chromosomal Cassette mec SCCmec Phenotypes and Antibiotic Resistance Properties

Background:

Staphylococcus aureus has long been considered as a major pathogen of hospital infections.

Objectives:

The present investigation was carried out to study the distribution of Staphylococcal Chromosomal Cassette mec (SCCmec) types, Panton-Valentine Leukocidin (PVL) gene and antibiotic resistance properties of Methicillin Resistant Staphylococcus aureus (MRSA) strains isolated from various types of infections found in Iranian pediatric patients.

Patients and Methods:

Two-hundred and fifty-five clinical specimens were collected from four major provinces of Iran. Samples were cultured and the MRSA strains were subjected to Polymerase Chain Reaction (PCR). The patterns of antibiotic resistance were determined using the disk diffusion method.

Results:

Seventy-four out of 255 (29.01%) clinical samples were positive for MRSA. Of the 74 MRSA strains, 47 (63.51%) were PVL positive. The clinical samples of respiratory tract infections (36.36%), those from the Shiraz province (37.87%) and samples collected during the summer season (56.48%) were the most commonly infected samples. The most commonly detected antibiotic resistance genes were tetK (89.18%), mecA (71.62%), msrA (56.75%) and tetM (54.05%). Methicillin Resistant Staphylococcus aureus had the highest levels of resistance against penicillin (100%), tetracycline (98.64%), ampicillin (93.24%) and oxacillin (93.24%). The most commonly detected SCCmec types in the MRSA strains were type V (18.91%) and III (17.56%).

Conclusions:

Regular surveillance of hospital-associated infections and monitoring of the antibiotic sensitivity patterns are required to reduce the prevalence of MRSA. We recommend initial management of children affected by MRSA with imipenem, lincomycin and cephalothin prescriptions.

Relationship between adhesin genes and biofilm formation in vancomycin-intermediate Staphylococcus aureus clinical isolates

The adherence ability and biofilm production are the characteristic of enhanced virulence among isolates of vancomycin-intermediate Staphylococcus aureus (VISA) strains. Although biofilm-forming properties have been well demonstrated in S. aureus, they still remain unclear among the recently emerged types of VISA strains. The aim of this study was to investigate correlations between the distribution of genes encoding staphylococcal microbial surface components which recognise adhesive matrix molecules (MSCRAMMs), the surface protein A (Spa) types, MLST types and the ability of VISA strains to biofilm formation. Microtiter plate assay (Mtp) results showed that all eleven biofilm producer isolates were adherent at various levels. PCR experiments showed that nine MSCRAMM genes, clfA, clfB, fnbA and fib were detected in all of the strains, indicating a high prevalence. The prevalences of other MSCRAMMs and icaABCD genes were found to be variable and not equally distributed among the VISA strains. There was no direct correlation between the distribution of adhesion-related genes and biofilm formation, which indicates that the presence or absence of these genes cannot be employed as an indicator of the ability to biofilm formation. Isolates which belong to the same Spa and ST types showed similar adherence capacities in the Mtp assay, but significant differences were observed between different Spa types. The findings of this study, using quantitative methods, have shown that genotypically different strains of VISA have different capabilities to produce biofilms. This may be caused by a difference in the spa types of VISA isolates or due to their differences in the expression of MSCRAMM and icaABCD genes.

Meticillin-resistant Staphylococcus aureus isolated from Iranian hospitals: virulence factors and antibiotic resistance properties

Staphylococcus aureus is an important opportunistic pathogen responsible for a variety of diseases. Indiscriminate prescription of antibiotics caused severe antibiotic resistance especially against commonly used drugs. The present investigation was carried out to study the distribution of Panton-Valentine Leukocidin gene, SCCmec types and antibiotic resistance properties of meticillin-resistant Staphylococcus aureus isolated from Iranian hospitals. A total of 132 clinical specimens were collected from two major Iranian hospitals. Samples were cultured and their positive results were subjected to several PCR methods. The patterns of antibiotic resistance were studied using the disk diffusion method. We found that 66 out of 132 samples (50%) were positive for Staphylococcus aureus. The most commonly infected samples were superficial and surgical wounds (66.12%). The incidence of mecA, tetK, ermA, ermC, tetM, aacA-D, linA, msrA, vatA, vatC and vatB antibiotic resistance genes were 80.30%, 34.84%, 30.30%, 25.75%, 24.24%, 19.69%, 7.57%, 7.57%, 6.06%, 3.03% and 1.51%, respectively. Totally, 40.90% of isolates harbored the Panton-Valentine Leukocidin gene. Of 53 mec positive strains, the distribution of SCCmec V, SCCmec III, SCCmec IVa, SCCmec IVc and SCCmec IVb were 28 (52.83%), 13 (24.52%), 6 (11.32%), 4 (7.54%) and 2 (3.77%), respectively. All isolates were resistant to penicillin, cephalothin, cefazoline and ceftriaxone. The high levels of Staphylococcus aureus resistance against commonly used antibiotics as well as high presence of SCCmec types of meticillin-resistant virulent strains of Staphylococcus aureus suggest that infections with these strains require more advanced hospital care with emerging demand for novel antibiotics.