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Molecular detection of some tetracycline-resistant genes in Staphylococcus aureus isolated from sheep milk in Al-Qadisiyah province
Abstract
Our study aims to investigate some tetracycline resistance genes in isolates of Staphylococcus aureus that collected from ewes milk that collected randomly. Sixty Milk samples are taken from ewes randomly and submitted to culturing on blood agar then submitted to PCR methods for final confirming detection of Staphylococcus aureus by using specific primers designed for (Glpf) gene depending on NCBI and Primer3 then making sensitivity test for tetracycline then make PCR for detection of some tetracycline resistance genes. Our results showed positive samples for Staphylococcus aureus was 14/60 (23.3%) by using PCR. Besides, all Staphylococcus aureus isolates were submitted to the tetracycline sensitivity test (disk diffusion method (Kirby‐Bauer) by tetracycline. Moreover, showing the percentage of tetracycline resistance isolates was 8/14(57.1%), and tetracycline sensitive isolates were 6/14 (42.8%). Also, our results showed the percentage of tetracycline resistance genes tet(L) and tet(k) were 9/14 (64.2%) and 7/14 (50%) respectively, and percentage of isolates that carry gene tet(L) and tet(K) together was 2/14 (14.2)% by using polymerase chain reaction technique. Our study concluded ewes milk that contaminated by Staphylococcus aureus at a high rate, and the non-response to treatment by tetracycline is occurred due to present tetracycline resistance genes such as tet(L) and tet(k), were causes treatment failure by tetracycline.
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Objective:
To determine antibiotic susceptibility pattern of S. aureus isolates from clinical specimens collected from patients at Kenyatta National Hospital from March 2014-February 2016, and to determine the prevalence and quarterly trends of MRSA throughout the study period.
Results:
A total of 944 S. aureus isolates were analyzed. High sensitivity of S. aureus was observed for quinupristin/dalfopristin (100%), tigecycline (98.2), imipenem (98%), nitrofurantoin (97.6%), linezolid (97.3%), teicoplanin (97.1%) and vancomycin (95.1%). High resistance was recorded against penicillin G (91.9%), trimethoprim/sulfamethoxazole (56.9%) and tetracycline (33.2%). MRSA prevalence among the patients at KNH was 27.8%. Highest proportion (80%) of MRSA was in burns unit. Both MRSA and MSSA were highly susceptible to quinupristin/dalfopristin, tigecycline, linezolid, nitrofurantoin, ampicillin/sulbactam and vancomycin and showed high resistance to commonly used antibiotics such as gentamycin, erythromycin, levofloxacin and tetracycline. A majority of isolates were from pus specimen (68%).
Staphylococcus aureus (S. aureus) is one of the most common organisms associated with infections among burn patients and has shown a frequent and rapid development of antibiotic resistance. The presence of genes encoding aminoglycoside modifying enzymes (AME) and tetracycline resistance were detected by PCR and multiplex-PCR. Among the 151 S. aureus isolates recovered from the burn patients, 96 (63.6%) were detected to have mecA gene. The rate of tetracycline resistance genes associated with mecA was 61% (92/151). Forty nine isolates (32.4%) contained tetM, 26 (17.2%) possessed only tetK and 21 (13.9%) contained both tetM and tetK. The presence of the aac(6')-Ie-aph(2'')-I gene was determined in 18 isolates, aph(3')-IIIa in 8 isolates, both the aac(6')-Ie-aph(2'')-I, aph(3')-IIIa and the ant(4')-Ia genes in 69 isolates, both aac(6')-Ie-aph(2'')-I and ant(4')-Ia in 6 isolates, and both the aph(3')-IIIa and the ant(4')-Ia genes in 8 isolates. Most of the strains which harboured the mecA gene also contained the tet and AME genes.
The objective of this study was to determine the expression and transferability of tetracycline and erythromycin resistance among 188 MRSA strains from a Malaysian tertiary hospital. The minimum inhibitory concentrations (MICs) for oxacillin, erythromycin, tetracycline and ciprofloxacin ranged from 4 to 512 μg/ml, 0.25 to 256 μg/ml, 0.5 to 256 μg/ml and 0.5 to 512 μg/ml, respectively. Tetracycline-resistant strains showed co-resistance towards ciprofloxacin and erythromycin. There was a significant increase (P<0.05) of high-level tetracycline (≥MIC 256 μg/ml) and erythromycin (≥MIC 128 μg/ml) resistant strains in between the years 2003 and 2008. All erythromycin-resistant strains harboured ermA or ermC gene and all tetracycline-resistant strains harboured tetM or tetK gene. The blaZ was detected in all MRSA strains, whereas ermA, tetM, ermC, tetK and msrA genes were detected in 157 (84%), 92 (49%), 40 (21%), 39 (21%) and 4 (2%) MRSA strains, respectively. The blaZ, tetM, ermC and tetK genes were plasmid-encoded, with ermC gene being easily transmissible. Tn5801-like transposon was present in 78 tetM-positive strains. ermA and tetM genes were the most prevalent erythromycin and tetracycline resistance determinants, respectively, in MRSA strains. The association of resistance genes with mobile genetic elements possibly enhances the spread of resistant traits in MRSA.
A diverse collection of methicillin-resistant Staphylococcus aureus (MRSA) isolates resistant to tetracycline was screened by PCR for the presence of the resistance determinants tetK, tetL, tetM or tetO. Twenty-four of 66 isolates had tetM alone, 21 had tetK alone and 21 had both tetK and tetM (tetKM). All isolates were tetL- and tetO-negative. MICs of tetracycline, doxycycline and minocycline were evaluated for all isolates with or without preincubation in the presence of subinhibitory concentrations of tetracycline or minocycline. All isolates with one or more tetracycline resistance determinants were resistant to tetracycline 8 mg/L without induction of resistance. Some MRSA isolates of each of these three genotypes showed an unexpected lack of resistance to tetracyclines when the disc diffusion or agar dilution method was applied to uninduced cells. Resistance to tetracycline and doxycycline was greater (two- to four-fold) in tetK cells preincubated with tetracycline (tetK MRSA isolates were susceptible to minocycline </=0.25 mg/L under all conditions tested). For isolates with tetM alone, preincubation with tetracycline or minocycline gave up to a four-fold increase in the level of resistance to doxycycline and minocycline. Induction of doxycycline and minocycline resistance was clearly observed for tetKM isolates when cells were preincubated with minocycline. This study suggests that, despite the results of susceptibility testing, all tetracycline-resistant S. aureus isolates should be treated as resistant to doxycycline, and all tetM-positive isolates should be treated as resistant to all tetracyclines. A double disc diffusion method has been developed to identify inducible resistance to minocycline and to distinguish between tetK, tetM and tetKM isolates.
Tetracyclines were discovered in the 1940s and exhibited activity against a wide range of microorganisms including gram-positive and gram-negative bacteria, chlamydiae, mycoplasmas, rickettsiae, and protozoan parasites. They are inexpensive antibiotics, which have been used extensively in the prophlylaxis and therapy of human and animal infections and also at subtherapeutic levels in animal feed as growth promoters. The first tetracycline-resistant bacterium, Shigella dysenteriae, was isolated in 1953. Tetracycline resistance now occurs in an increasing number of pathogenic, opportunistic, and commensal bacteria. The presence of tetracycline-resistant pathogens limits the use of these agents in treatment of disease. Tetracycline resistance is often due to the acquisition of new genes, which code for energy-dependent efflux of tetracyclines or for a protein that protects bacterial ribosomes from the action of tetracyclines. Many of these genes are associated with mobile plasmids or transposons and can be distinguished from each other using molecular methods including DNA-DNA hybridization with oligonucleotide probes and DNA sequencing. A limited number of bacteria acquire resistance by mutations, which alter the permeability of the outer membrane porins and/or lipopolysaccharides in the outer membrane, change the regulation of innate efflux systems, or alter the 16S rRNA. New tetracycline derivatives are being examined, although their role in treatment is not clear. Changing the use of tetracyclines in human and animal health as well as in food production is needed if we are to continue to use this class of broad-spectrum antimicrobials through the present century.
The effect of large-scale expanded surveillance for methicillin-resistant Staphylococcus aureus (MRSA) on health care-associated MRSA disease is not known.
To examine the effect of 2 expanded surveillance interventions on MRSA disease.
Observational study comparing rates of MRSA clinical disease during and after hospital admission in 3 consecutive periods: baseline (12 months), MRSA surveillance for all admissions to the intensive care unit (ICU) (12 months), and universal MRSA surveillance for all hospital admissions (21 months).
A 3-hospital, 850-bed organization with approximately 40,000 annual admissions.
Polymerase chain reaction-based nasal surveillance for MRSA followed by topical decolonization therapy and contact isolation of patients who tested positive for MRSA.
Poisson and segmented regression models were used to compare prevalence density of hospital-associated clinical MRSA disease (bloodstream, respiratory, urinary tract, and surgical site) in each period. Rates of bloodstream disease with methicillin-susceptible S. aureus were used as a control.
The prevalence density of aggregate hospital-associated MRSA disease (all body sites) per 10,000 patient-days at baseline, during ICU surveillance, and during universal surveillance was 8.9 (95% CI, 7.6 to 10.4), 7.4 (CI, 6.1 to 9.0; P = 0.15 compared with baseline), and 3.9 (CI, 3.2 to 4.7; P < 0.001 compared with baseline and ICU surveillance), respectively. During universal surveillance, the prevalence density of MRSA infection at each body site had a statistically significant decrease compared with baseline. The methicillin-susceptible S. aureus bacteremia rate did not statistically significantly change during the 3 periods. In a segmented regression model, the aggregate hospital-associated MRSA disease prevalence density changed by -36.2% (CI, -65.4% to 9.8%; P = 0.17) from baseline to ICU surveillance and by -69.6% (CI, -89.2% to -19.6%]; P = 0.03) from baseline to universal surveillance. During universal surveillance, the MRSA disease rate decreased during hospitalization and in the 30 days after discharge; no further reduction occurred thereafter. Surveillance with clinical cultures would have identified 17.8% of actual MRSA patient-days, and ICU-based surveillance with polymerase chain reaction would have identified 33.3%.
The findings rely on observational data.
The introduction of universal admission surveillance for MRSA was associated with a large reduction in MRSA disease during admission and 30 days after discharge.
Part I of volume 1 covers the basic principles of the concepts of diagnosis and management of infectious disease. Chapters dealing with microbial virulence factors, host defense mechanisms, the epidemiology of infectious disease and the clinical and microbiological data are included. There is also a comprehensive discussion of anti-infective chemotherapy. Part II considers major clinical syndromes followed by a discussion of the potential etiologic agents, evaluation of differential diagnostic possibilities and an outline of presumptive therapy. All major infectious diseases are discussed in this part of the book.
Five common tetracycline resistance genes tet(A), tet(B), tet(M), tet(O) and tet(S) were studied by polymerase chain reaction in 100 bacteria isolated from Iranian fish farms. In the antibiogram test most of the bacteria were either intermediately or completely resistant to tetracycline. Nine isolates out of 46 Aeromonas spp. contained either tet(A/M/S) resistant genes as follows: tet(A) in A. veronii/sobria (n = 1), A. media (n = 2), A. aquariorum (n = 1), and A. veronii (n = 3); tet(M) in one isolate of A. sobria and tet(S) in 1 isolate of A. jandaei. In other bacteria, tet(A) gene was detected in Citrobacter freundi (n = 1), Pseudomonas putida (n = 1); tet(S) was also identified in Yersinia ruckeri (n = 1), Arthrobacter arilaitensis (n = 1) and P. putida (n = 1). In total, 31 isolates (31.00%) contained the tetracycline resistance genes in which 21 bacteria (21.00%) showed the tet(S), nine bacteria (9.00%) contained the tet(A) and 1 bacteria (1.00%) was positive for tet(M). All of the L.
garvieae isolates contained tet(S) in this study. The most widely distributed resistance gene was gene tet(A) and the least known resistance genes was tet(M) among the studied bacteria of the genus Aeromonas in this study.
A 4 kb fragment of chromosomal DNA was cloned from a clinical strain of methicillin-resistant Staphylococcus aureus. It comprises part of a section of the chromosome that was lost when the strain was cured of resistance to methicillin and to other antimicrobial agents. The fragment mediates an increased level of methicillin resistance when inserted into a shuttle vector and transformed back into the sensitive strain generated when the original DNA was deleted.
Resistance to Tetracycline and Vancomycin of Staphylococcus aureus Isolates from Sanandaj Patients by Molecular Genotyping
- F -Arabzadeh
- F Aeini
- F Keshavarzi
- P Karami
-Arabzadeh F, Aeini F, Keshavarzi F, Karami P (2018) Resistance to
Tetracycline and Vancomycin of Staphylococcus aureus Isolates from Sanandaj
Patients by Molecular Genotyping. Ann Clin Lab Res Vol.6 No.4:260.