Toxic Shock Syndrome Toxin-1 Gene Research Articles

Discovery of an antivirulence compound that targets the Staphylococcus aureus SaeRS two-component system to inhibit toxic shock syndrome toxin-1 production

Menstrual toxic shock syndrome (mTSS) is a rare but severe disorder associated with the use of menstrual products such as high-absorbency tampons and is caused by Staphylococcus aureus strains that produce the toxic shock syndrome toxin-1 (TSST-1) superantigen. Herein, we screened a library of 3920 small bioactive molecules for the ability to inhibit transcription of the TSST-1 gene without inhibiting growth of S. aureus. The dominant positive regulator of TSST-1 is the SaeRS two-component system (TCS), and we identified phenazopyridine hydrochloride (PP-HCl) that repressed production of TSST-1 by inhibiting the kinase function of SaeS. PP-HCl competed with ATP for binding of the kinase SaeS leading to decreased phosphorylation of SaeR and reduced expression of TSST-1 as well as several other secreted virulence factors known to be regulated by SaeRS. PP-HCl targets virulence of S. aureus, and it also decreases the impact of TSST-1 on human lymphocytes without affecting the healthy vaginal microbiota. Our findings demonstrate the promising potential of PP-HCl as a therapeutic strategy against mTSS.

Antimicrobial resistance and virulence profiling of Staphylococcus pseudintermedius isolated from cats, Bangladesh

Staphylococcus pseudintermedius is a significant bacterial pathogen that frequently colonizes different body sites and mucous membranes of pets. The objectives of the cross-sectional study were to estimate the prevalence, antimicrobial resistance pattern, and detection of diverse resistance as well as virulence genes of S. pseudintermedius in cats. A standard bacteriological method, species-specific gene and different antimicrobial resistance as well as virulence genes were confirmed by PCR assay. A total of 233 swab samples were collected from different body sites of 102 cats, among them 146 swabs from 73 healthy cats, and 87 from 29 diseased cats. Overall, prevalence of S. pseudintermedius in cats was 12.01%, while dermatitis and otitis affected cats were 26.08% and 33.33%, respectively. The highest antimicrobial resistance was observed against penicillin (96.42%) followed by streptomycin (85.71%) and erythromycin (78.57%). Moreover, 89.28% of S. pseudintermedius isolates exhibit multi-drug resistance (MDR) (≥ 3 classes’ antimicrobial resistant). In addition, 17.86% isolates harbored the mecA gene; thus, were classified as methicillin-resistant S. pseudintermedius (MRSP). Furthermore, the erythromycin resistance genes ermA and ermB were harbored by 25% and 10.71% of isolates, while 42.86% and 17.86% of isolates carried tetK and tetL (tetracycline resistance) genes, respectively. In virulence profiling, 32.14% (sea) and 10.71% (seb) of isolates were found positive for enterotoxin genes, whereas, the toxic shock syndrome toxin-1 (tst-1) gene and the Panton-Valentine leukocidin gene (pvl) were detected in 25% and 14.29% of isolates, respectively. To our knowledge, this is the first report of cats in Bangladesh for MDR S. pseudintermedius, MRSP, and their virulence profiling.

Evolutionary dynamics of the novel ST22-PT methicillin-resistant Staphylococcus aureus clone co-harbouring Panton–Valentine leucocidin and duplicated toxic shock syndrome toxin 1 genes

ObjectivesGlobally, the isolation of community-associated methicillin-resistant Staphylococcus aureus (MRSA) harbouring both the Panton–Valentine leucocidin (PVL) and toxic shock syndrome toxin 1 (TSST-1) genes is rare. However, we encountered an outbreak of the ST22-PT clone exhibiting this phenotype in Japan. Notably, the TSST-1 gene was duplicated in most of the strains. This study aimed to elucidate the mechanisms underlying this gene duplication. MethodsA total of 90 MRSA isolates were collected from the skin of outpatients in Fukuoka City, Japan, between 2017 and 2019. Whole-genome sequencing was performed on MRSA strains that were PVL and TSST-1 positive. ResultsA total of 43 (47.8%) strains produced TSST-1, 20 (22.2%) produced PVL, and 16 (17.8%) produced both. Fifteen isolates were classified as ST22/SCCmec type IVa (ST22-PT clone) and one as ST1/SCCmec type V (ST1-PT clone). Three distinct ST22-PT clones were identified: Fukuoka clone I (one PVL gene and one TSST-1 gene), Fukuoka clone II (addition of a TSST-1 gene to Fukuoka clone I), and Fukuoka clone III (marked by a chromosomal inversion in a large region from Fukuoka clone II). DiscussionFukuoka clone I may have integrated a novel pathogenicity island bearing the TSST-1 gene, leading to the emergence of Fukuoka clone II with a duplicated TSST-1 gene. This duplication subsequently instigated a chromosomal inversion in a large region owing to the homologous sequence surrounding TSST-1, giving rise to Fukuoka clone III. These findings provide crucial insights into the genetic evolution of MRSA.

Diversity of Staphylococcus aureus isolated from nares of ruminants.

To examine the diversity of Staphylococcus aureus isolated from nasal swabs of ruminants in Rwanda. A total of 454 nasal swabs from 203 cows, 170 goats, and 81 sheep were examined for the presence of S. aureus, and 30 S. aureus isolates were detected and characterized pheno- and genotypically. Resistance to penicillin and/or tetracycline was observed. The isolates were assigned to eight different spa types (t21057 (novel), t10103, t18853, t20842, t318, t355, t458, and t9432) belonging to six clonal complexes (CCs) (CC152, CC30, CC3591, CC3666, CC522, and CC97). Panton-Valentine leukocidin (PVL) genes (lukF-PV/lukS-PV), the bovine leukocidin genes (lukM/lukF-P83), and the human and bovine variants of the toxic shock syndrome toxin gene tst-1 variants were detected. These findings demonstrate that the nares of ruminants in Rwanda are colonized with mastitis-associated S. aureus, including lineages that are also carried by humans, underscoring the zoonotic risk, especially for livestock keepers. These results highlight the crucial importance of hygiene measures when handling livestock.

Assessment of Staphylococcal toxins acting as superantigens in different nasal specimens in the etiology of chronic rhinosinusitis

The mechanism of development of chronic rhinosinusitis(CRS) is not fully known. However, bacteria are thought to play an important role in this clinic. It has been suggested that toxins with superantigen(SAgs) properties produced by one of these bacteria, Staphylococcus aureus(S.aureus), play a role in the development of inflammation associated with sinusitis. In this study, S.aureus was isolated by taking endoscopic sinus biopsy samples and nasal swab samples from patients with CRS and the control group. It was aimed to examine the frequency of S.aureus presence in the samples taken, the presence of toxin genes showing superantigen quality in these isolated bacteria, and to evaluate the roles of these parameters in the development of CRS. More S.aureus was isolated in the samples taken from patients with CRS than in the control group. The isolated S.aureus samples were analysed by real-time PCR method. The presence of enterotoxin A, B, C and D genes in the S.aureus samples isolated from the patient group were found at the rates of 54%, 32%, 16% and 16%, respectively, while these rates were 46%, 24%, 14% and 14% in the control group. The Toxic Shock Syndrome Toxin-1(TSST-1) gene was detected in 20% of the samples isolated from the patient and 46% in the control group bacteria. The fact that S.aureus was isolated in 20% of the patients shows that this bacterium is not necessary for CRS. The frequency of superantigen toxin genes in S.aureus isolates shows that these toxins are not necessary for the development of the disease.

Characterisation of antibiotic resistant Staphylococcus species and molecular identification of mecA and toxic shock syndrome toxin-1 (tsst-1) genes of Staphylococcus aureus isolates from cows' milk

Staphylococcus aureus (S. aureus) is one of the most important causes of foodborne illness. Due to the interest of people to use traditional dairy products, especially milk, in the current descriptive study the frequency of S. aureus, antibiotic resistance pattern and presence of toxic shock syndrome toxin-1 gene (tsst-1 gene) in these isolated strains was investigated. Thirty-nine strains (26%) of S. aureus were identified from the samples studied, of which 6 (15.38%) were resistant to methicillin, and 9 (23.07%) were positive for mecA gene. Also, 31 (20.7%) coagulase-negative staphylococci isolates were identified. Out of the 39 strains of S. aureus, the presence of tsst gene was detected in 1 strain (2.56%). Therefore, S. aureus contamination indicates a risk to public health and can be significantly controlled using a high level of hygiene and professional training in the handling of raw milk.

Staphylococcus aureus in the Processing Environment of Cured Meat Products.

The presence of Staphylococcus aureus in six dry-cured meat-processing facilities was investigated. S. aureus was detected in 3.8% of surfaces from five facilities. The occurrence was clearly higher during processing (4.8%) than after cleaning and disinfection (1.4%). Thirty-eight isolates were typified by PFGE and MLST. Eleven sequence types (STs) were defined by MLST. ST30 (32%) and ST12 (24%) were the most abundant. Enterotoxin genes were detected in 53% of isolates. The enterotoxin A gene (sea) was present in all ST30 isolates, seb in one ST1 isolate, and sec in two ST45 isolates. Sixteen isolates harbored the enterotoxin gene cluster (egc) with four variations in the sequence. The toxic shock syndrome toxin gene (tst) was detected in 82% of isolates. Regarding antimicrobial resistance, twelve strains were susceptible to all the antibiotics tested (31.6%). However, 15.8% were resistant to three or more antimicrobials and, therefore, multidrug-resistant. Our results showed that in general, efficient cleaning and disinfection procedures were applied. Nonetheless, the presence of S. aureus with virulence determinants and resistance to antimicrobials, particularly multidrug-resistant MRSA ST398 strains, might represent a potential health hazard for consumers.

Molecular identification, antimicrobial resistance and virulence gene profiling of Staphylococcus spp. associated with bovine sub-clinical mastitis in Bangladesh

This study was conducted to investigate the diversity and antimicrobial resistance profiling of Staphylococcus species causing sub-clinical mastitis (SCM) in dairy herds in Bangladesh as well as putative risk factors associated with the infections. Individual quarter milk samples were collected from a total of 284 lactating cows from 30 dairy farms were screened by means of California mastitis test; 178 (62.7%) of them had at least of quarter affected by SCM. After conventional microbiological isolation procedures, PCR tests were used for Staphylococcus species identification and detection of antimicrobial resistance and virulence genes. S. chromogenes (65.7%) was the most predominant species followed by, S. epidermidis (20.2%), S. haemolyticus (19.1%), S. aureus (15.7%), and S. sciuri (5.6%). High levels of antimicrobial resistance to ampicillin and amoxicillin/clavulanic acid were observed in S. aureus (82.1% and 75%) and S. sciuri (80% and 70%), while resistance to cefepime was markedly higher in S. chromogenes (95.7%), S. haemolyticus (94.1%), and S. epidermidis (97.2%). Multidrug resistance isolates were identified in all five species. The mecA gene was detected in S. aureus (32.1%) and S. chromogenes (5.98%). In addition, 20% S. sciuri and 17.7% S. haemolyticus carried the cytotoxin (pvl) gene, while 14.3% S. aureus harbored the toxic shock syndrome toxin (tst) gene. Multivariable logistic regression analysis identified “Old aged” (OR [CI]: 3.5 [1–12.4]); “Early stage of lactation” (OR [CI]: 3.4 [1.2–9.7]) and, “Firm udder condition” (OR [CI]: 4.2 [1.2–14.6]) as risk factors associated with SCM caused by S. aureus, S. chromogenes, and S. haemolyticus, respectively. Moreover, “Use of antimicrobials” (OR [CI]: 10.4 [3.4–32.1] and “History of previous clinical mastitis” (OR [CI]: 4.9 [1.2–19.7] for the carriage of methicillin-resistant Staphylococcus spp.

The emerging threat of methicillin-resistant Staphylococcus aureus (MRSA) clone ST22-PT, carrying both Panton-Valentine leucocidin and toxic shock syndrome toxin 1 genes.

Some MRSA strains produce Panton-Valentine leucocidin (PVL) and/or toxic shock syndrome toxin 1 (TSST-1), which are associated with severe infectious diseases. Although PVL- or TSST-1-positive strains have been isolated worldwide, strains carrying both PVL and TSST-1 genes are rare and sporadic. The objective of this study was to characterize these strains from Japan. A total of 6433 MRSA strains isolated in Japan between 2015 and 2021 were analysed. Molecular epidemiological and comparative genomic analyses were conducted on PVL- and TSST-1-positive MRSA strains. A total of 26 strains from 12 healthcare facilities were PVL positive and TSST-1 positive, and all were classified as clonal complex (CC) 22. These strains exhibited similar genetic features to each other and were named as ST22-PT according to a previous report. Twelve and one of the ST22-PT strains were identified in patients with deep-seated skin infections and toxic shock syndrome-like symptoms, which are typical clinical features of PVL-positive and TSST-1-positive Staphylococcus aureus, respectively. Whole-genome comparative analysis revealed that the ST22-PT strains were highly similar to PVL- and TSST-1-positive CC22 strains isolated in several countries. Evaluation of the genome structure showed that ST22-PT possessed ΦSa2 harbouring PVL genes and a unique S. aureus pathogenicity island harbouring the TSST-1 gene. ST22-PT strains have recently emerged from several healthcare facilities in Japan, and ST22-PT-like strains have been identified in several countries. Our report highlights that the risk of international spread of PVL- and TSST-1-positive MRSA clone ST22-PT needs to be further investigated.

Prevalence of Panton-Valentine leukocidin and toxic shock syndrome toxin-1 genes in methicillin-resistant Staphylococcus aureus isolated from nose of restaurant workers in Kirkuk city.

Staphylococcus aureus resides naturally in the nasal cavity of healthy individuals, including those working in restaurants, so they may be a source for spreading this bacterium to restaurant customers directly or indirectly through cooked meals. This bacterium has several virulence factors enabling it to cause many diseases in different parts of the body. It has also the capability to resist conventional antibiotics including methicillin. To investigate methicillin-resistant S. aureus (MRSA), 170 nasal swabs were collected from food preparation workers in 30 restaurants (5-6 workers in each restaurant) in Kirkuk city. After collection, the samples were directly transferred to the laboratory and cultured on selective media like mannitol salt agar (MSA). Microbiological examination including morphological, biochemical, and confirmatory tests showed that 24/170 of collected samples were positive for S. aureus with a rate of 14.12%. Among 24 isolates, 20 (83.3%) belonged to MRSA. All isolates were resistant to oxacillin and penicillin (100%), whereas sensitive to other antibiotics (gentamicin, chloramphenicol, and rifampicin). Polymerase chain reaction exhibited that 13 (65%) of MRSA isolates have toxic shock syndrome toxin-1 gene and only 4 (20%) have Panton-Valentine leukocidin gene.

Characterization of Virulence Genes and Antibiotic Resistance of Methicillin-resistant Staphylococcus aureus (MRSA) and Methicillin-susceptible Staphylococcus aureus (MSSA) Isolates in Intensive Care Unit (ICU) and Non-ICU Wards

Background: We are witnessing the increasing use of antibiotics and the upward trend of resistant nosocomial infections. Therefore, identifying pathogens and determining the local patterns of antibiotic resistance are the health system's priorities in any region. Objectives: The current study aimed to investigate the prevalence of methicillin-resistant Staphylococcus aureus (MRSA) in the Intensive Care Unit (ICU) and Non-ICU wards, the toxic shock syndrome toxin-1 (TSST-1), alpha-toxin (Hla), and pantone-valentine leucocidin (PVL) genes in S. aureus strains, and antibiotic resistance patterns to provide a clinical guide for clinicians in Southwest Iran. Methods: Staphylococcus aureus was isolated from clinical specimens between 2018 and 2020. Methicillin-resistant S. aureus was detected by cefoxitin screening. Then, the antimicrobial resistance of all isolates was tested with the disk diffusion (DD) and the minimum inhibitory concentration (MIC) methods. Virulence genes, including TSST-1, Hla, and PVL, were evaluated by the PCR method. Results: Of 186 S. aureus strains isolated from various specimens, 51 (27.4%) were MRSA, with a 26.8% rate in the ICU. All isolates were susceptible to vancomycin, teicoplanin, linezolid, daptomycin, and quinupristin-dalfopristin. The penicillin-resistant S. aureus proportion was 93.5% (174/186), and more than 50% of all S. aureus isolates were resistant to fluoroquinolones. The incidence rates of virulence factors, including TSST-1, Hla, and PVL genes in MRSA, were 3.9%, 39.2%, and 2%, respectively. Conclusions: It is recommended to start empiric treatment against MRSA in case of severe infections in the ICU with either quinupristin-dalfopristin, daptomycin, vancomycin, teicoplanin, or linezolid until the culture and antibiotic susceptibility test results are available. Nevertheless, following the antibiotic resistance pattern is necessary to start treatment for other infections.

Comparative Genomic Analysis of a Panton-Valentine Leukocidin-Positive ST22 Community-Acquired Methicillin-Resistant Staphylococcus aureus from Pakistan.

Staphylococcus aureus (S. aureus) ST22 is considered a clinically important clone because an epidemic strain EMRSA-15 belongs to ST22, and several outbreaks of this clone have been documented worldwide. We performed genomic analysis of an S. aureus strain Lr2 ST22 from Pakistan and determined comparative analysis with other ST22 strains. The genomic data show that Lr2 belongs to spa-type t2986 and harbors staphylococcal cassette chromosome mec (SCCmec) type IVa(2B), one complete plasmid, and seven prophages or prophage-like elements. The strain harbors several prophage-associated virulence factors, including Panton–Valentine leukocidin (PVL) and toxic shock syndrome toxin (TSST). The single nucleotide polymorphism (SNPs)-based phylogenetic relationship inferred from whole genome and core genome revealed that strain Lr2 exhibits the nearest identities to a South African community-acquired methicillin-resistant S. aureus (CA-MRSA) ST22 strain and makes a separate clade with an Indian CA-MRSA ST22 strain. Although most ST22 strains carry blaZ, mecA, and mutations in gyrA, the Lr2 strain does not have the blaZ gene but, unlike other ST22 strains, carries the antibiotic resistance genes erm(C) and aac(6′)-Ie-aph(2″)-Ia. Among ST22 strains analyzed, only the strain Lr2 possesses both PVL and TSST genes. The functional annotation of genes unique to Lr2 revealed that mobilome is the third-largest Cluster of Orthologous Genes (COGs) category, which encodes genes associated with prophages and transposons. This possibly makes methicillin-resistant S. aureus (MRSA) Lr2 ST22 strain highly virulent, and this study would improve the knowledge of MRSA ST22 strains in Pakistan. However, further studies are needed on a large collection of MRSA to comprehend the genomic epidemiology and evolution of this clone in Pakistan.

Genomic Investigation of Methicillin-Resistant Staphylococcus aureus ST113 Strains Isolated from Tertiary Care Hospitals in Pakistan.

Methicillin-resistant Staphylococcus aureus (MRSA) is a multi-drug resistant and opportunistic pathogen. The emergence of new clones of MRSA in both healthcare settings and the community warrants serious attention and epidemiological surveillance. However, epidemiological data of MRSA isolates from Pakistan are limited. We performed a whole-genome-based comparative analysis of two (P10 and R46) MRSA strains isolated from two provinces of Pakistan to understand the genetic diversity, sequence type (ST), and distribution of virulence and antibiotic-resistance genes. The strains belong to ST113 and harbor the SCCmec type IV encoding mecA gene. Both the strains contain two plasmids, and three and two complete prophage sequences are present in P10 and R46, respectively. The specific antibiotic resistance determinants in P10 include two aminoglycoside-resistance genes, aph(3’)-IIIa and aad(6), a streptothrin-resistance gene sat-4, a tetracycline-resistance gene tet(K), a mupirocin-resistance gene mupA, a point mutation in fusA conferring resistance to fusidic acid, and in strain R46 a specific plasmid associated gene ant(4’)-Ib. The strains harbor many virulence factors common to MRSA. However, no Panton-Valentine leucocidin (lukF-PV/lukS-PV) or toxic shock syndrome toxin (tsst) genes were detected in any of the genomes. The phylogenetic relationship of P10 and R46 with other prevailing MRSA strains suggests that ST113 strains are closely related to ST8 strains and ST113 strains are a single-locus variant of ST8. These findings provide important information concerning the emerging MRSA clone ST113 in Pakistan and the sequenced strains can be used as reference strains for the comparative genomic analysis of other MRSA strains in Pakistan and ST113 strains globally.

Antibiotic Sensitivity and Virulence Genes in Staphylococcus aureus Isolates from Surgical Site Infection

Fourteen multi drug resistant Staphylococcus aureus isolates from surgical site infection were analyzed for their antibiotic sensitivity and the presence of nine virulence genes. The isolates showed a high resistance pattern, all being resistant to methicillin, oxacillin, azithromycin, ceftazidime and amoxyclav. Seven of the isolates were sensitive to linezolid; three were sensitive to trimethoprim: sulfamethoxazol and another three were sensitive to ciprofloxacin. Ceftriaxone, gentamicin and amikacin were the drugs of choice as nine (64.3%) isolates were sensitive to ceftriaxone, eleven (78.6%) were sensitive to gentamicin and another eleven (78.6%) to amikacin. The present study focused to identify nine important virulence genes including intrinsic methicillin resistance gene mecA, methicillin resistance assisting gene femA, toxic shock syndrome toxin gene tst, exfoliative toxin A and B genes, eta and etb, Panton Valentine leukocidin gene LukS/F-PVL, along with three enterotoxin genes sec, sed and see. According to the presence of mecA gene and antibiotic resistance profile, two isolates were identified as methicillin resistant Staphylococcus aureus. However, another isolate, despite harbouring both mecA and femA genes, was sensitive to ceftriaxone which excluded it from being considered as an MRSA. Thus, the ratio of MRSA can be considered to be quite high (2/14) among the strains. Interestingly, most of the isolates (10/14) harboured femA gene, the majority of which were mecA negative with an MSSA type antibiotic profile. Although considered as a marker for community acquired MRSA, LukS/F-PV was found in half of these nosocomial isolates. Five, four and two of the isolates harboured etb, tst and sec gene, respectively. However, all the isolates were negative for eta, sed and see genes. Two isolates showed the co-existance of “femA, LukS/F-PV, etb, and tst” genes. Another two virulence gene patterns observed were “femA, mecA, tst, sec” and “femA, LukS/F-PV, etb”. The presence of several virulence genes can be correlated to the highly pathogenic nature of the isolates.
 Bangladesh J Microbiol, Volume 38, Number 1, June 2021, pp 21-26

PREVALENCE OF TSST PRODUCING COAGULASE-NEGATIVE STAPHYLOCOCCUS AUREUS IN WOUND SAMPLES AND CHARACTERIZATION OF MRSA AGAINST TEA EXTRACT

Objective: Methicillin-resistant Staphylococcus aureus (MRSA) is a potential pathogen for hospital-acquired infections. This study was conducted to determine the prevalence of MRSA using tea extract. Methods: All S. aureus isolates obtained from wound samples were studied for antibiotic resistance pattern using 23 different antibiotics. Based on coagulase negative, S. aureus isolates were identified for toxic shock syndrome toxin (TSST) gene and analyzed using PCR method. The antibacterial activities of tea extract were tested against MRSA using agar well-diffusion method. Results: A total of 100 wound samples were collected from hospital, where 75% of samples showed presence of S. aureus. About 100% resistance to cefoperazone, ampicillin, penicillin, rifampicin, novobiocin, and vancomycin antibiotics was observed. The isolates showed less resistance <50% toward chloramphenicol (30%), ciprofloxacin (25%), gentamycin (52%), amikacin (38%), and imipenem (33%). Twenty-five isolates were selected for MRSA characterization based on multiple drug resistance pattern. Coagulase-negative S. aureus isolates showed presence of TSST gene. Tea extract (2%) showed effective antibacterial activity against MRSA strains. Conclusion: The study showed the presence of MRSA at higher level and suggesting to out further epidemiological study on such infections. However, cost-effective and easily available tea extract was found to be the best antimicrobial agent for preventing such bacterial infection and to reduce the risk of emerging resistance.

A Molecular Study of Toxic Shock Syndrome Toxin gene (tsst-1) in β-lactam Resistant Staphylococcus aureus Clinical Isolates

Three hundred and sixty different samples were collected from different sources, including wound, burn, nasal, and oral swabs from several hospitals in Baghdad. A number of 150 (53%) Staphylococcus aureus samples were isolated and identified among a total of 283 samples. Then, the spread of the Toxic Shock Syndrome Toxin-1 gene (tsst-1) was investigated in β-lactamase resistant S. aureus. According to the source of samples, the distribution of S. aureus isolates was found to be significantly higher (p < 0.01) in wound samples as compared to other sources. According to the age, a highly significant distribution (p < 0.01) was recorded in the age group of 15-30 years, whereas gender comparison showed no statistically significant differences. All the isolates were subjected to susceptibility test against eight β-Lactam antibiotics by using the disc diffusion method. The antimicrobial susceptibility test showed that S. aureus had maximum resistance percentage to Carbenicillin (97.3%), while the lowest resistance rate was against Meropenem, with a sensitivity rate of up to 82%. In addition, 144 (96%) out of the 150 S. aureus isolates have multiple drug resistance (MDR). All the isolates were subjected to polymerase chain reaction to amplify tsst-1 toxin gene. A number of 70 isolates (46.7%) were found to be positive for tsst-1 gene. The results showed no significant correlation between tsst-1 gene with the individual antibiotic resistance and the multi-drug resistance patterns of the isolates (p = 0.226).

Molecular Typing of Community-acquired Methicillin-Resistant Staphylococcus aureus Isolated from 2- to 6-year old Children by Staphylococcal Protein A and Agr Typing in Isfahan, Iran.

Background: Methicillin-resistant Staphylococcus aureus (MRSA) has become a considerable public health concern in the entire world due to the rapid spread of this bacterium in human community; also the epidemiology of MRSA has changed, as the isolation of MRSA strains from healthy and non-healthy patients. Therefore, the objective of this study is to determine the genetic diversity and antibiotic resistance profile of community-acquired (CA)-MRSA nasal carriage in the Iranian samples.Materials and Methods:A total of 25 CA-MRSA were isolated from the anterior nares of 410 healthy preschool children. All MRSA isolates were characterized by the detection of the toxic shock syndrome toxin-1 (TSST-1) and typed by γ-hemolysin genes, agr groups, and staphylococcal protein A (spa) typing. Kirby-Buyer antibiotic susceptibility testing was performed and interpreted as per the standard guidelines.Results:A total of 25 (6.1%) MRSA isolates were recovered from the anterior nares of 410 preschool children. Sixteen isolates (64%) were positive for the TSST-1 gene. Three agr specificity groups were determined, as follows: eight (32%) isolates belonged to agr Group I, five (20%) isolates belonged to agr Group II, and 12 (48%) isolates belonged to agr Group III. The repeated profiles of these spa types of 25 isolates were organized into eight different lineages groups. Five of lineages contained a single strain, three of lineages contained two strains, and three of lineages consisted of more than three strains.Conclusions:The results of our study show that the rate of MRSA in our region is significantly high. Additionally, spa type t037 was the predominant type among CA S. aureus.

Community- and Health Care-Associated Methicillin-Resistant Staphylococcus aureus Infection in Tehran, Iran: Comparison of Drug Resistance and Virulence Determinants.

Methicillin-resistant Staphylococcus aureus (MRSA) can cause serious infections not only in hospitals but also in the community. The present study was aimed to characterize drug resistance and virulence determinants of community-associated (CA) MRSA isolate compared with healthcare-associated (HA) MRSA. A total of 44 patients with HA-MRSA and 11 patients with CA-MRSA infection (median age, 72 years) were included. The clinical isolates of MRSA were subjected to molecular analysis of virulence genes and drug susceptibility testing. Panton-Valentine leucocidin (PVL) exotoxin and toxic shock syndrome toxin (TSST) genes were disproportionately distributed between CA- and HA-isolates. PVL genes were more likely to be found among CA-isolates (36.4%) than HA-isolates (18.2). TSST genes were identified in only 2 CA-MRSA isolates tested (18.2%) compared with 9 HA-isolates (20.5%). Exfoliative toxin- b gene was negative in all isolates, however, one HA-isolate was positive for exfoliative toxin-a. mec-A gene was present in all clinical isolates. CA-isolates were more likely to be susceptible to trimethoprim-sulfamethoxazole and vancomycin compared with HA-isolates. Vancomycin-intermediate resistance was found in 2 HA-isolates. All clinical isolates were also resistant to clindamycin. CA- and HA- MRSA isolates are epidemiologically and microbiologically distinct. Thus, the strategies to prevent and treat these infections would be different. Patients with CA- and HA-MRSA infections should be treated effectively and receive follow-up evaluation to ensure the resolution of their infection. Surveillance studies should be conducted to determine the extent of CA- and HA-MRSA dissemination in Iran.

Antimicrobial Resistance and Virulence of Methicillin-Resistant Staphylococcus aureus from Human, Chicken and Environmental Samples within Live Bird Markets in Three Nigerian Cities.

Background: Methicillin-resistant Staphylococcus aureus (MRSA) has emerged as a major threat to public health. This study investigated the occurrence of MRSA in humans, chickens, chicken meat and environmental samples within poultry farms and live bird markets in southwestern Nigeria. Methods: MRSA were isolated using selective culture and tested for antimicrobial susceptibility by broth microdilution. Selected isolates were characterized by whole genome sequencing (WGS). From WGS data, spa, dru, multilocus sequence typing (MLST) and SCCmec types, but also virulence and antimicrobial resistance genes, were identified. Results: Fifty-six MRSA isolates were detected in 734 samples. They showed resistance to β-lactams (100%), tetracycline (60.7%), ciprofloxacin (33.9%), erythromycin (28.6%), gentamicin (32.1%), and trimethoprim/sulfamethoxazole (10.7%). All 30 isolates investigated by WGS carried mecA, dfrG, and tet(38) genes. Other resistance genes detected were blaZ (83.3%), fosB (73.3%), tet(K) (60.0%), aacA-aphD (36.6%), aphA3 (33.3%), msr(A) (30.0%), mph(C) (30.0%), dfrS1 (3.3%), and sat4 (3.3%). Seven spa types (t091, t314, t657, t1476, t2331, t4690 and t12236), four known (dt9aw, dt10ao, dt10cj, and dt11a) and two novel (dt10dr and dt11dw) dru types, as well as five sequence types (ST8, ST121, ST152, ST772 and ST789) were found among the MRSA isolates. All ST121 isolates carried an SCCmec type IV cassette and were not dru-typeable. ST152 and ST121 were found only in specific sample categories within defined locations, while ST8 and ST772 were distributed across most sample categories and locations. Three SCCmec types, IVa, V and Vc, were identified. All MRSA isolates possessed virulence genes including aur, clpP, coa, fnbA, esaA, hly, hla, ica, isdA, srtB, sspA, and vWbp, among others. The toxic shock syndrome toxin gene (tst) was not detected in any isolate, whereas the Pantone–Valentine leukocidin genes lukF-PV/lukS-PV were present in all ST121, all ST772, and all but one ST152 isolates. Conclusion: The results of this study (i) showed that chicken meat is contaminated by MRSA and (ii) suggested that live bird markets may serve as focal points for the dissemination of MRSA within the community.

Characteristics of methicillin-resistant Staphylococcus aureus carrying the toxic shock syndrome toxin gene: high prevalence of clonal complex 22 strains and the emergence of new spa types t223 and t605 in Iran.

Methicillin-resistant Staphylococcus aureus (MRSA) strains that carry the tst gene are disseminated worldwide with varying regional incidences and different genetic backgrounds. The data on molecular characteristics of these strains is insufficient in Iran. The present study aimed to assess the characteristics and distribution of spa types of tst-positive MRSA strains. We investigated 89 MRSA isolates carrying the tst gene with spa typing, resistance gene detection and in vitro antimicrobial susceptibility. Of the 89 tested isolates, 61 (68.5%) were confirmed as multidrug resistant (MDR). The isolates were distributed across seven clonal complexes (CCs) including CC22 (42.7%), CC8 (28.1%), CC5 (11.2%), CC59 (5.6%), CC30 (4.5%), CC80 (4.5%) and CC15 (3.4%). spa typing identified 11 distinct types, with t223 (16.9%) and t790 (15.7%) being the most prevalent. All high-level mupirocin-resistant strains belonged to t002 (n = 8) and low-level mupirocin-resistant strains belonged to t790 (n = 6) spa types. Fusidic-acid-resistant isolates belonged to t437 (n = 3). iMLSB phenotype was observed in t005 (6.7%), t002 (5.6%), t790 (3.4%), and t030, t044 and t084 (each 2.2%). It was found that in the tst-carrying MRSA strains, there were genetic diversities with a majority of the t223 spa type. Indeed, there is a necessity for more constructive surveillance/infection control strategies to address the prevalence and prevention of the emerging spa types.