scholarly journals Genetic Organization of the Chromosome Region Surrounding mecA in Clinical Staphylococcal Strains: Role of IS431-Mediated mecI Deletion in Expression of Resistance in mecA-Carrying, Low-Level Methicillin- Resistant Staphylococcus haemolyticus

2001 ◽  
Vol 45 (7) ◽  
pp. 1955-1963 ◽  
Author(s):  
Yuki Katayama ◽  
Teruyo Ito ◽  
Keiichi Hiramatsu
Keyword(s):  
Gene Transcription ◽  
Methicillin Resistance ◽  
Chromosome Region ◽  
Population Analysis ◽  
Phenotypic Expression ◽  
Gene Complex ◽  
Methicillin Resistant ◽  
Low Level ◽  
Class A ◽  
Class C

ABSTRACT We report on the structural diversity of mecA gene complexes carried by 38 methicillin-resistant Staphylococcus aureus and 91 methicillin-resistant coagulase-negativeStaphylococcus strains of seven different species with a special reference to its correlation with phenotypic expression of methicillin resistance. The most prevalent and widely disseminatedmec complex had the structuremecI-mecR1-mecA-IS431R (or IS431mec), designated the class A mecA gene complex. In contrast, in S. haemolyticus, mecA was bracketed by two copies of IS431, forming the structure IS431L-mecA-IS431R. Of the 38 S. haemolyticus strains, 5 had low-level methicillin resistance (MIC, 1 to 4 mg/liter) and characteristic heterogeneous methicillin resistance as judged by population analysis. In these five strains, IS431L was located to the left of an intactmecI gene, forming the structure IS431L-class AmecA-gene complex. In other S. haemolyticusstrains, IS431L was associated with the deletion ofmecI and mecR1, forming the structure IS431L-ΔmecR1-mecA-IS431mec, designated the class C mecA gene complex. Mutants with the class C mecA gene complex were obtained in vitro by selecting strain SH621, containing the IS431L-class AmecA gene complex with low concentrations of methicillin (1 and 3 mg/liter). The mutants had intermediate level of methicillin resistance (MIC, 16 to 64 mg/liter). The mecA gene transcription was shown to be derepressed in a representative mutant strain, SH621-37. Our study indicated that the mecI-encoded repressor function is responsible for the low-level methicillin resistance of some S. haemolyticus clinical strains and that the IS431-mediated mecI gene deletion causes the expression of methicillin resistance through the derepression of mecA gene transcription.

scholarly journals Complete Genome Sequence of Macrococcus caseolyticus Strain JSCS5402, Reflecting the Ancestral Genome of the Human-Pathogenic Staphylococci

2008 ◽  
Vol 191 (4) ◽  
pp. 1180-1190 ◽  
Author(s):  
Tadashi Baba ◽  
Kyoko Kuwahara-Arai ◽  
Ikuo Uchiyama ◽  
Fumihiko Takeuchi ◽  
Teruyo Ito ◽  
...  
Keyword(s):  
Resistance Gene ◽  
Virulence Genes ◽  
Acid Metabolism ◽  
Methicillin Resistance ◽  
Small Chromosome ◽  
Gene Complex ◽  
Human Pathogens ◽  
Methicillin Resistant ◽  
The Family ◽  
Genome Nucleotide Sequence

ABSTRACT We isolated the methicillin-resistant Macrococcus caseolyticus strain JCSC5402 from animal meat in a supermarket and determined its whole-genome nucleotide sequence. This is the first report on the genome analysis of a macrococcal species that is evolutionarily closely related to the human pathogens Staphylococcus aureus and Bacillus anthracis. The essential biological pathways of M. caseolyticus are similar to those of staphylococci. However, the species has a small chromosome (2.1 MB) and lacks many sugar and amino acid metabolism pathways and a plethora of virulence genes that are present in S. aureus. On the other hand, M. caseolyticus possesses a series of oxidative phosphorylation machineries that are closely related to those in the family Bacillaceae. We also discovered a probable primordial form of a Macrococcus methicillin resistance gene complex, mecIRAm , on one of the eight plasmids harbored by the M. caseolyticus strain. This is the first finding of a plasmid-encoding methicillin resistance gene. Macrococcus is considered to reflect the genome of ancestral bacteria before the speciation of staphylococcal species and may be closely associated with the origin of the methicillin resistance gene complex of the notorious human pathogen methicillin-resistant S. aureus.

scholarly journals Methicillin Resistant Staphylococcus aureus nasal carriage and associated factors in a rural tertiary hospital in Eastern Uganda: A prospective cross-sectional study

2019 ◽  
Author(s):  
Nobert Thembo ◽  
George Masifa ◽  
Gerald Kamugisha ◽  
Robinah Nabitaka ◽  
Benjamin Akais ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Associated Factors ◽  
Methicillin Resistant Staphylococcus Aureus ◽  
Methicillin Resistance ◽  
Phenotypic Expression ◽  
Nasal Carriage ◽  
Referral Hospital ◽  
Carriage Rate ◽  
Regional Referral Hospital ◽  
Methicillin Resistant

Abstract Background: Asymptomatic carriage of Methicillin-Resistant Staphylococcus aureus (MRSA) can predispose the host to a wide array of infections that can be difficult to treat due to antibiotic resistance. To inform public health strategies, the study sought to describe MRSA nasal carriage frequencies and the associated factors concerning nasal carriage among patients attending Mbale Regional Referral Hospital (MRRH). Methods: Nasal swabs were obtained from consented (aged >15years) participants presenting to the hospital for medical care between January and April 2018[L1] . Direct Culture of swabs was performed on blood agar and then incubated at 37℃ for 24 hours. Identification of S. aureus was done using conventional biochemical tests. Phenotypic screening and confirmation of MRSA was done using cefoxitin disc (30µg) test and MICs on the Phoenix M50 instrument respectively. Patient demographic characteristics and the MRSA nasal carriage risk factors were collected using a pre-tested questionnaire. Results: Overall, majority of the participants were in-patients (138, 63.3%) with the proportions of both females and males among the participants being 154/218 (70.6%) and 64/218 (29.3%) respectively. Mean age for both female and male participants was 40.16 (SD± 17.04) years respectively. S. aureus nasal carriage rate among the participants was 22.9% (50/218), with 57.9% (29/50) of the harboured strains phenotypically expressing methicillin resistance (mecA mediated). Phenotypic co-expression with inducible clindamycin resistance and vancomycin resistance was displayed in 45.5% (23/50) and 2% (1/50) of the studied isolates respectively. Colonisation with MRSA did not show any significant relationship with all the studied factors. Conclusion: There was a moderate S. aureus nasal carriage among the participants in Mbale Regional Referral Hospital with a highly noted phenotypic expression of methicillin resistance among the isolated S. aureus strains. The studied factors were not significantly associated with the rate of MRSA nasal carriage. For surveillance purposes to combat future outbreaks, there is a need to do a larger study to better draw generalizable conclusions of carriage in the population. [L1]This is an important statement. I suggest that we reinstatate it if we are still in recommended word count

scholarly journals Differential Expression of Methicillin Resistance by Different Biofilm-Negative Staphylococcus epidermidis Transposon Mutant Classes

2002 ◽  
Vol 46 (1) ◽  
pp. 178-183 ◽  
Author(s):  
Dietrich Mack ◽  
Axel Sabottke ◽  
Sabine Dobinsky ◽  
Holger Rohde ◽  
Matthias A. Horstkotte ◽  
...  
Keyword(s):  
Staphylococcus Epidermidis ◽  
Biofilm Formation ◽  
Methicillin Resistance ◽  
Population Analysis ◽  
Phenotypic Expression ◽  
Class Ii ◽  
Class Iii ◽  
Wild Type ◽  
Heterogeneous Expression ◽  
Negative Phenotype

ABSTRACT Biofilm formation mediated by polysaccharide intercellular adhesin (PIA) is the major virulence factor of Staphylococcus epidermidis and is often associated with methicillin resistance. Transposon Tn917 insertions leading to a biofilm-negative phenotype in the biofilm-producing S. epidermidis strain 1457 (mecA-negative) were transferred into the methicillin-resistant, biofilm-producing S. epidermidis 1057 (mecA-positive) by transduction. According to their phenotypes and genotypes, the mutants could be separated into genetic classes I to IV (D. Mack, H. Rohde, S. Dobinsky, J. Riedewald, M. Nedelmann, J. K. M. Knobloch, H.-A. Elsner, and H. H. Feucht, Infect. Immun. 68:3799–3807, 2000). All transductants of S. epidermidis 1057 had phenotypes for biofilm formation similar to those of the corresponding mutants of S. epidermidis 1457. With a mecA-specific probe, identical hybridization patterns were observed for wild-type S. epidermidis 1057 and all the transductants. There were minor changes in oxacillin MICs for Class II and III transductants compared to those for wild-type S. epidermidis 1057. On population analysis, S. epidermidis 1057 displayed a heterogeneous expression type of resistance with an oxacillin MIC of ≥6 μg/ml for more than 90% of the cells. An almost identical profile was observed with biofilm-negative class I mutants, where the transposon insertions inactivate the icaADBC gene locus essential for PIA synthesis. In contrast, class III mutants were more sensitive to oxacillin with a MIC of ≤1 μg/ml for more than 90% of the cells. The class IV mutant displayed homogenous resistance with a MIC of ≥50 μg/ml for more than 90% of the cells. On oxacillin gradient plates, the class II mutant displayed decreased resistance. Apparently, different independent mutations leading to a biofilm-negative phenotype of S. epidermidis by influencing expression of icaADBC on the level of transcription significantly influence the expression of methicillin resistance. However, transcription of mecA was not significantly altered in the different transductants compared to the wild type, independent of mecA induction with oxacillin, indicating that other mechanisms influencing phenotypic expression of methicillin resistance are involved.

scholarly journals Methicillin Resistant Staphylococcus aureus nasal carriage and associated factors in a rural tertiary hospital in Eastern Uganda: A prospective cross-sectional study

2020 ◽  
Author(s):  
Nobert Thembo ◽  
George Masifa ◽  
Gerald Kamugisha ◽  
Robinah Nabitaka ◽  
Benjamin Akais ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Associated Factors ◽  
Methicillin Resistant Staphylococcus Aureus ◽  
Methicillin Resistance ◽  
Phenotypic Expression ◽  
Nasal Carriage ◽  
Referral Hospital ◽  
Carriage Rate ◽  
Regional Referral Hospital ◽  
Methicillin Resistant

Abstract Background: Asymptomatic carriage of Methicillin-Resistant Staphylococcus aureus (MRSA) can predispose the host to a wide array of infections that can be difficult to treat due to antibiotic resistance. To inform public health strategies, the study sought to describe MRSA nasal carriage frequencies and the associated factors concerning nasal carriage among patients attending Mbale Regional Referral Hospital (MRRH). Methods: Nasal swabs were obtained from consented (aged >15years) participants presenting to the hospital for medical care between January and April 2018 [L1] . Direct Culture of swabs was performed on blood agar and then incubated at 37℃ for 24 hours. Identification of S. aureus was done using conventional biochemical tests. Phenotypic screening and confirmation of MRSA was done using cefoxitin disc (30µg) test and MICs on the Phoenix M50 instrument respectively. Patient demographic characteristics and the MRSA nasal carriage risk factors were collected using a pre-tested questionnaire. Results: Overall, majority of the participants were in-patients (138, 63.3%) with the proportions of both females and males among the participants being 154/218 (70.6%) and 64/218 (29.3%) respectively. Mean age for both female and male participants was 40.16 (SD± 17.04) years respectively. S . aureus nasal carriage rate among the participants was 22.9% (50/218), with 57.9% (29/50) of the harboured strains phenotypically expressing methicillin resistance ( mecA mediated). Phenotypic co-expression with i nducible clindamycin resistance and vancomycin resistance was displayed in 45.5% (23/50) and 2% (1/50) of the studied isolates respectively. Colonisation with MRSA did not show any significant relationship with all the studied factors. Conclusion : There was a moderate S. aureus nasal carriage among the participants in Mbale Regional Referral Hospital with a highly noted phenotypic expression of methicillin resistance among the isolated S. aureus strains. The studied factors were not significantly associated with the rate of MRSA nasal carriage. For surveillance purposes to combat future outbreaks, there is a need to do a larger study to better draw generalizable conclusions of carriage in the population. [L1] This is an important statement. I suggest that we reinstatate it if we are still in recommended word count

scholarly journals Suppression of methicillin resistance in a mecA-containing pre-methicillin-resistant Staphylococcus aureus strain is caused by the mecI-mediated repression of PBP 2' production.

1996 ◽  
Vol 40 (12) ◽  
pp. 2680-2685 ◽  
Author(s):  
K Kuwahara-Arai ◽  
N Kondo ◽  
S Hori ◽  
E Tateda-Suzuki ◽  
K Hiramatsu
Keyword(s):  
Staphylococcus Aureus ◽  
Gene Transcription ◽  
Culture Medium ◽  
Methicillin Resistant Staphylococcus Aureus ◽  
Methicillin Resistance ◽  
Meca Gene ◽  
Aureus Strain ◽  
Methicillin Resistant ◽  
Gene Transcripts ◽  
Regulator Genes

The mechanism of methicillin susceptibility was studied in Staphylococcus aureus N315P, a pre-methicillin-resistant S. aureus strain that is susceptible to methicillin, despite the presence of mecA in the chromosome. In the presence of mec regulator genes mecI and mecR1, transcription of the mecA gene was not inducible by the addition of methicillin to the culture medium. Inactivation of the mecI gene function by replacing it with tetL made N315P express heterogeneous-type methicillin resistance. The subclone, in which the mecI gene was replaced, subclone P delta I, produced 12 times greater amounts of mecA gene transcripts and 8.5 times more PBP 2' protein than N315P. These data indicate that the mecI gene-encoded repression of mecA gene transcription is responsible for the apparent methicillin susceptibility phenotype of pre-methicillin-resistant S. aureus N315P.

scholarly journals Methicillin Resistant Staphylococcus aureus nasal carriage and associated factors in a rural tertiary hospital in Eastern Uganda: A prospective cross-sectional study

2019 ◽  
Author(s):  
Nobert Thembo ◽  
George Masifa ◽  
Gerald Kamugisha ◽  
Robinah Nabitaka ◽  
Benjamin Akais ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Associated Factors ◽  
Methicillin Resistant Staphylococcus Aureus ◽  
Clinical Laboratory ◽  
Methicillin Resistance ◽  
Phenotypic Expression ◽  
Nasal Carriage ◽  
Referral Hospital ◽  
Regional Referral Hospital ◽  
Methicillin Resistant

Abstract Background: Asymptomatic carriage of Methicillin-Resistant Staphylococcus aureus (MRSA) can predispose the host to a wide array of infections that would pose a challenge in the management of the cases in a current era encompassed with antibiotic resistance. To inform public health strategies, the study sought to describe MRSA nasal carriage frequencies and the associated factors concerning nasal carriage among patients attending Mbale Regional Referral Hospital (MRRH). Methods: Two hundred eighteen consented participants presenting to the hospital for medical care between January and April 2018 were recruited to participate in this study. Sampling was done on both anterior nares using a pre-moistened swab and then transported to the laboratory at Room temperature for the detection of MRSA. Culture was performed on blood agar and plates incubated at 37℃ for 24 hours. Identification of Staphylococcus aureus was done using conventional biochemical tests . MRSA was detected phenotypically using cefoxitin (30µg) as a surrogate test as per the Clinical Laboratory Standard Institute guidelines 2017 version. Patient demographic characteristics and the MRSA nasal carriage factors were collected using a pre-tested questionnaire. The collected raw data was entered into excel and later imported into STATA software for analysis. Results: Overall, Majority of the participants were in-patients (138, 63.3%) with the proportions of both females and males among the participants being 154/218 (70.6%) and 64/218 (29.3%) respectively. Mean age for both female and male participants was 40.16 (SD± 17.04) years respectively. Staphylococcus aureus nasal carriage rate among the participants was 22.9% (50/218), with 72% (36/50) of the harboured strains phenotypically expressing methicillin resistance. Colonization with Methicillin Resistant Staphylococcus aureus did not show any significant relationship with all the studied factors. Conclusion: There was a moderate Staphylococcus aureus nasal carriage among the participants in Mbale Regional Referral Hospital. We also observed a highly displayed phenotypic expression of methicillin resistance among the isolated Staphylococcus aureus strains. The studied factors indicated an independent influence on the rate of nasal carriage. For surveillance purposes to combat future outbreaks, there is a need to do a larger study with better power to better draw generalizable conclusions of carriage in the population.

scholarly journals Eagle-Type Methicillin Resistance: New Phenotype of High Methicillin Resistance under mec Regulator Gene Control

2001 ◽  
Vol 45 (3) ◽  
pp. 815-824 ◽  
Author(s):  
Noriko Kondo ◽  
Kyoko Kuwahara-Arai ◽  
Hiroko Kuroda-Murakami ◽  
Eiko Tateda-Suzuki ◽  
Keiichi Hiramatsu
Keyword(s):  
Gene Transcription ◽  
Genomic Library ◽  
Methicillin Resistance ◽  
Genetic Alteration ◽  
Specific Gene ◽  
High Concentration ◽  
Methicillin Resistant ◽  
Mutant Strains ◽  
Multiple Copies ◽  
High Concentrations

ABSTRACT We report a novel phenotype of methicillin resistance, designated “Eagle-type” resistance, which is characteristic in its resistance to high concentrations of methicillin (64 to 512 μg/ml) and susceptibility to low concentrations of methicillin (2 to 16 μg/ml). The type of resistance was expressed in mutant strains selected with high concentrations (e.g., 128 to 512 μg/ml) of methicillin from the pre-methicillin-resistant Staphylococcus aureus strain N315, whose mecA gene transcription is strongly repressed by the mecI gene-encoded repressor protein MecI. The Eagle-type mutant strains harbored no mutation in themecI gene or in the operator region ofmecA gene to which MecI repressor is supposed to bind. In the representative Eagle-type strain h4, repression of mecAgene transcription and penicillin-binding protein 2′ production were found to be released by exposing the cells to a high concentration (128 μg/ml) of methicillin but not to lower concentrations (1 and 8 μg/ml) of methicillin. The strain h4 expressed paradoxical susceptibility (Eagle effect) to the cytokilling activity of methicillin. Experimental deletion of mecI gene from the chromosome of h4 by mecI-specific gene substitution converted its Eagle-type resistance to homogeneously high methicillin resistance. We cloned two novel genes, designated hmrA andhmrB, from genomic library of h4, which conferred Eagle-type resistance to N315 when introduced into the cell in multiple copies. The genes were shown to confer homogeneous methicillin resistance to the heterogeneously methicillin-resistant strain LR5 when they were introduced into on multicopy plasmids. This result strongly indicated that the genetic alteration responsible for the expression of the Eagle phenotype is identical, or equivalent in its effect, to the genetic alteration underlying heterogeneous-to-homogeneous conversion of methicillin resistance in S. aureus.

scholarly journals The First Report of a Methicillin-Resistant Staphylococcus aureus Isolate Harboring Type IV SCCmec in Thailand

Pathogens ◽  
2021 ◽  
Vol 10 (4) ◽  
pp. 430
Author(s):  
Wichai Santimaleeworagun ◽  
Praewdow Preechachuawong ◽  
Wandee Samret ◽  
Tossawan Jitwasinkul
Keyword(s):  
Staphylococcus Aureus ◽  
Resistance Genes ◽  
Methicillin Resistant Staphylococcus Aureus ◽  
Methicillin Resistance ◽  
Sccmec Type ◽  
Clinical Strain ◽  
Spa Typing ◽  
Methicillin Resistant ◽  
Type Iv ◽  
Antimicrobial Resistance Genes

Methicillin-resistant Staphylococcus aureus (MRSA) is mostly found in Thailand in the hospital as a nosocomial pathogen. This study aimed to report the genetic characterization of a clinical community-acquired MRSA (CA-MRSA) isolate collected from hospitalized patients in Thailand. Among 26 MRSA isolates, S. aureus no. S17 preliminarily displayed the presence of a staphylococcal cassette chromosome mec (SCCmec) type IV pattern. The bacterial genomic DNA was subjected to whole-genome sequencing. Panton–Valentine leukocidin (PVL) production, virulence toxins, and antibiotic resistance genes were identified, and multi-locus sequence typing (MLST) and spa typing were performed. The strain was matched by sequence to MLST type 2885 and spa type t13880. This strain carried type IV SCCmec with no PVL production. Five acquired antimicrobial resistance genes, namely blaZ, mecA, Inu(A), tet(K), and dfrG conferring resistance to β-lactams, lincosamides, tetracycline, and trimethoprim, were identified. The detected toxins were exfoliative toxin A, gamma-hemolysin, leukocidin D, and leukocidin E. Moreover, there were differences in seven regions in CR-MRSA no. S17 compared to CA-MRSA type 300. In summary, we have reported the ST2885-SCCmec IV CA-MRSA clinical strain in Thailand for the first time, highlighting the problem of methicillin resistance in community settings and the consideration in choosing appropriate antibiotic therapy.

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