Microbiology
Meysam Manouchehrifar; Farzad Khademi; Hadi Peeri Doghaheh; shahram Habibzadeh; Mohsen Arzanlou
Abstract
Background & Objective: Staphylococcus aureus causes various hospital- and community-acquired infections. This study aimed to investigate the phenotypic and genotypic characteristics of erythromycin and inducible clindamycin resistance, virulence gene profiles, and spa types of S. aureus isolates ...
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Background & Objective: Staphylococcus aureus causes various hospital- and community-acquired infections. This study aimed to investigate the phenotypic and genotypic characteristics of erythromycin and inducible clindamycin resistance, virulence gene profiles, and spa types of S. aureus isolates collected from patients in Ardabil Province, Iran.Methods: A total of 118 clinical S. aureus isolates, including 50 (42.4%) methicillin-resistant S. aureus (MRSA) and 68 (57.6%) methicillin-susceptible S. aureus (MSSA) strains, were investigated. Resistance patterns were determined by the disk diffusion method and minimum inhibitory concentration (MIC) test. Inducible macrolide-lincosamide-streptogramin B (iMLSB) resistance was detected using D-test method. The polymerase chain reaction (PCR) was used to identify the virulence and resistance-encoding genes. Additionally, the spa types of the isolates were determined using the PCR, followed by sequencing.Results: In total, 49.1% (58/118) and 44% (52/118) of the isolates were resistant to erythromycin and clindamycin, respectively. Overall, 13.5% (16/118) of the isolates showed the iMLSB resistance phenotype. The ermC gene (72.4% [42]) was the most frequent erythromycin resistance-encoding gene, followed by ermA (60.3% [35]), ermB (60.3% [35]), ermTR (51.7% [30]), and msrA (15.5% [9]) genes among erythromycin-resistant isolates. The virulence genes hla, hld, sea, LukS PV, tst, seb, sed, eta, sec, and etb were detected in 93.2%, 74.5%, 70.3%, 32.2%, 29.6%, 17%, 8.5%, 8.5%, 5.9%, and 4.2% of the isolates, respectively. Ten different spa types were identified for 58 erythromycin-resistant S. aureus strains, of which t030 and t078 types were the most common types.Conclusion: A high frequency of macrolide- and lincosamide-resistant S. aureus isolates with different genetic backgrounds of resistance and virulence may be found in patients in Ardabil Province, Iran.
Ali Majidpour; Sara Fathi Zadeh; Mastaneh Afshar; Mohammad Rahbar; Mina Boustanshenas; Marjan Heidarzadeh; Leila Arbabi; Somayeh Soleymanzadeh Moghadam
Abstract
Background & Objective: Staphylococcus aureus, especially methicillin-resistant S. aureus (MRSA), represent serious nosocomial and community infections. Biofilm formation as an important virulence factor may be affected by sub-inhibitory levels of antibiotics. Few studies examined the effects of ...
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Background & Objective: Staphylococcus aureus, especially methicillin-resistant S. aureus (MRSA), represent serious nosocomial and community infections. Biofilm formation as an important virulence factor may be affected by sub-inhibitory levels of antibiotics. Few studies examined the effects of all therapeutic antimicrobial agents on clinical S.aureus. The current study aimed at observing the inducing and reducing effects of antibiotics, commonly used to treat staphylococcal infections on the production of staphylococcal biofilm. Methods: Four MRSA (1ATCC and 3 clinical) and 1 methicillin-susceptible Staphylococcus aureus (MSSA) strains with biofilm forming ability, evaluated by the Congo red agar (CRA) plate test, were employed. Biofilm formation was measured by crystal violet microtiter plate assay. Cefazolin, rifampicin, vancomycin, oxacillin, clindamycin, cotrimoxazole, minocycline, linezolid, azithromycin, and clarithromycin were added to wells ranging from 0.06to 128 µg/mL (1× to 1/1024 MIC dependent on the MIC value of each strain). Results: The current study showed that azithromycin and vancomycin had a significant inducing effect on biofilm formation. In contrast, linezolid, cefazolin, and clarithromycin, and in the second place, clindamycin and minocycline could inhibit the level of biofilm production in the sub-minimal inhibitory concentrations. Conclusion: The findings demonstrated that the biofilm formation as an important virulence factor may be affected by the subinhibitory levels of antibiotics.
Microbiology
Hossein Koupahi; Sahar Honarmand Jahromy; Mohammad Rahbar
Volume 11, Issue 4 , October 2016, , Pages 370-376
Abstract
Background: Methicillin resistant Staphylococcus aureus (MRSA) has been emerged as a nosocomial and community acquired pathogen worldwide. There are many challenges for laboratory detection of MRSA. The aim of this study was to compare different phenotypic methods with PCR based method as a gold standard ...
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Background: Methicillin resistant Staphylococcus aureus (MRSA) has been emerged as a nosocomial and community acquired pathogen worldwide. There are many challenges for laboratory detection of MRSA. The aim of this study was to compare different phenotypic methods with PCR based method as a gold standard for detection of mecA gene. Methods: A total of 220 clinical isolates of S. aureus which were isolated from various clinical specimens from September 2013 until the June of 2014 in Milad Hospital of Tehran, Iran was subject of our study. Methicillin resistance was determined by oxacillin and cefoxitin disks, oxacillin screen agar and CHROMagar™ MRSA medium. The results of these methods were compared with mecA gene based PCR method as a gold standard method. Results: Among 220 isolates from S. aureus, 105 (47.72%) isolates were positive for mecA gene by PCR method. The results of cefoxitin disk diffusion method with 100% sensitivity and specificity was the same as PCR method .CHROMagar™ MRSA medium had 98.13% sensitivity and 100% specificity. Oxacillin disk diffusion and oxacillin screen agar had 95.42% and 97.22% sensitivity respectively. Conclusion: Result of cefoxitin disk diffusion method with 100% sensitivity and specificity was the same as PCR method for detection mecA gene. Cefoxitin disk diffusion method can be used as an alternative method of PCR for detection of MRSA.
Microbiology
Abdolmajid Ghasemian; Shahin Najar Peerayeh; Bita Bakhshi; Mohsen Mirzaee
Abstract
Background:Isolates of Staphylococcus aureus express a myriad of adhesive surface proteins that play important role in colonization of the bacteria on nasal and skin surfaces, beginning the process of pathogenesis. The aim of this study was to screen several of the Microbial Surface Components Recognizing ...
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Background:Isolates of Staphylococcus aureus express a myriad of adhesive surface proteins that play important role in colonization of the bacteria on nasal and skin surfaces, beginning the process of pathogenesis. The aim of this study was to screen several of the Microbial Surface Components Recognizing Adhesive Matrix Molecules (MSCRAMMs) genes among the isolate of S. aureus from hospitalized children.
Methods:A totalof 22 S. aureus isolates were collected from hospitalized children in Tehran from 2012 to 2013. Detection of the mecA and several adhesive surface proteins genes including clfA, B (encoding clumping factors A, B); fnbA, B (encoding finronectin binding proteins A, B); fib (encoding fibrinogen binding protein); eno (encoding laminin binding protein); cna (encoding collagen binding protein); ebps (encoding elastin binding protein) and bbp (encoding bone sialo-protein binding protein), was performed by PCR.
Results: The clfAB genes were detected among all the isolates. The prevalence of fnbA, fnbB, fib, eno, cna, ebps and bbp was 63%, 6%, 50%, 59%, 82%, 63%, 9% and 0%, respectively.
Conclusion: The high prevalence of these genes is important for future plans in vaccine designation. MRSA and MSSA isolates similarly can produce adhesive surface proteins for colonization.
Mohsen Mirzaee; Shahin Najar Peerayeh; Abdol-Majid Ghasemian
Volume 9, Issue 4 , October 2014, , Pages 257-262
Abstract
Background & Objectives: Methicillin resistance Staphylococcus aureus (MRSA) is one of the most important pathogens that causes several nosocomial and community infections. Adhesion to surfaces and biofilm formation is considered main step in staphylococcal infection. The aims of this study ...
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Background & Objectives: Methicillin resistance Staphylococcus aureus (MRSA) is one of the most important pathogens that causes several nosocomial and community infections. Adhesion to surfaces and biofilm formation is considered main step in staphylococcal infection. The aims of this study were to determine presence oficaABCD genes and relation to the biofilm formation in of MRSA isolates. Methods: Of the 63 MRSA clinical isolates collected from selected hospitals in Tehran, Iran,quantitative biofilm formation was determined by microtiter tissue culture plates (MtP). All MRSA isolates were examined for determination the icaABCD genes by using PCR method. Results: twenty nine (46%) of the isolates were strong produced biofilm on Mtp. All of the MRSA isolates carried icaD and icaC genes, whereas, the prevalence of icaA and icaB was 60.3% and 51% respectively. Conclusions: S. aureus clinical isolates have different capacity to production biofilm and adhesion. This may be caused by a different in the expression of biofilm genes and hetrogenicity in genetic origins.
Alireza Nateghian; Gholamreza Irajian; Fatemeh Faraji
Volume 6, Issue 2 , April 2011, , Pages 79-85
Abstract
Background and Objectives: The aim of the study was to determine the role and characteristics of nosocomial and community acquired Staphylococcus sepsis in admitted children in tertiary centers in Iran. Patients and Methods: A cross sectional descriptive-analytic study was performed since March ...
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Background and Objectives: The aim of the study was to determine the role and characteristics of nosocomial and community acquired Staphylococcus sepsis in admitted children in tertiary centers in Iran. Patients and Methods: A cross sectional descriptive-analytic study was performed since March 2008 to March 2009 in which all blood cultures from various admitted patients were checked for Staphylococcu aurues in Aliasghar Children Hospital, Tehran, Iran. Upon diagnosis by appropriate microbiologic tests, antimicrobial testing was done according to CLSI methods. Results: Overall, 2647 blood culture samples from 5197 admitted children were sent from which, 25 cases of S. aurues septicemia were isolated; the rate was 4.8 in 1000 admissions;1.3 in 1000 admissions were nosocomial and 3.5 in 1000 admissions were community acquired sepsis. Ten cases were neonates and remainder was older. Eighteen cases were CA and 28% were NI septicemia with mean age of 38.8 months and 8.2 months, respectively. Mean duration of admission in NI group was 20.5 days, however it was 12.6 days in CA group; they also had higher mortality rate. Conclusion: The rate of Staphylococcus sepsis in this study was higher than developed countries for both CA and NI cases, both groups had high rate of resistance. Although most cases were CA in which significant proportion had underlying malignancy, NI group had a longer duration of admission and mortality.
Horieh Saderi; Parviz Owlia; Maryam Eslami
Volume 4, Issue 4 , September 2009, , Pages 161-166
Abstract
Background and Objectives: Staphylococcus aureus is an important cause of nosocomial and community-acquired infections in every region of the world. Clindamycin is one of the alternative agents used to treat S. aureus infections and accurate identification of clindamycin resistance is important to prevent ...
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Background and Objectives: Staphylococcus aureus is an important cause of nosocomial and community-acquired infections in every region of the world. Clindamycin is one of the alternative agents used to treat S. aureus infections and accurate identification of clindamycin resistance is important to prevent therapeutic failure. Unfortunately, inducible clindamycin resistance is not detected by standard susceptibility tests. This study aimed to determine the prevalence of the macrolides-lincosamides-streptogramins B (MLSB) resistance in S. aureus isolated in four university hospitals in Tehran, Iran. Material & Methods: Two hundreds and forty-four non-duplicate clinical isolates of S. aureus (133 methicillin resistant S. aureus (MRSA) and 111 methicillin susceptible (MSSA) S. aureus) were collected in 2008. Antimicrobial susceptibilities were determined by the D-test. Results: Altogether, 68% and 61.1% of isolates were resistant to erythromycin and clindamycin, respectively; with higher resistance in MRSA isolates compared to MSSA isolates. The constitutive MLSB (cMLSB) resistance phenotype was recognized in 61.1%, while 5.3% had shown inducible MLSB (iMLSB) resistance phenotype. Constitutive MLSB resistance phenotype predominated over inducible MLSB resistance phenotype and susceptible phenotype (83.9, 9.3 and 6.8%, respectively) among the MRSA isolates, whereas susceptible phenotype predominated over constitutive MLSB resistance phenotype and inducible MLSB resistance phenotype (62.6, 31.3 and 2%, respectively) among the MSSA isolates. Conclusion:Considering the higher prevalence of clindamycin resistance in MRSA isolates compared MSSA isolates, routine D-test of MRSA isolates is strongly recommended to prevent treatment failure.
Horieh Saderi; Parviz Owlia; Zohreh Maleki; Mehri Habibi; Nayere Rahmati
Volume 3, Issue 3 , June 2008, , Pages 161-167
Abstract
Background and Objective: Vancomycin is frequently the antibiotic of choice for the treatment of infections caused by methicillin-resistant Staphylococcus aureus (MRSA). For the last years, the incidence of vancomycin-intermediate S. aureus (VISA) and vancomycin-resistant S. aureus (VRSA) has ...
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Background and Objective: Vancomycin is frequently the antibiotic of choice for the treatment of infections caused by methicillin-resistant Staphylococcus aureus (MRSA). For the last years, the incidence of vancomycin-intermediate S. aureus (VISA) and vancomycin-resistant S. aureus (VRSA) has been increased in various parts of the world. The present study was carried out to determine the presence of VISA and VRSA in Tehran. Materials and Methods: A total of 164 S. aureus strains were isolated from clinical specimens in four university-affiliated hospitals in Tehran from November 2006 to June 2007. Minimum inhibitory concentration (MIC) of vancomycin of isolates was determined by agar dilution method. Vancomycin (6 mg/l) screen agar plate method and E-test were used to confirm presence of resistance to vancomycin. Disc diffusion agar test was also used to detect resistance to other antimicrobial agents. Results: Only one VRSA(MIC 256 mg/l) was detected and three strains with MIC 4 mg/l considered VISA according to recent CLSI breakpoints for vancomycin. Only VRSA strain had shown growth on vancomycin screen agar plate and was also resistant to several antimicrobial agents but susceptible to quinupristin/dalfopristin, linezolid, chloramphenicol, mupirocin and cotrimoxazole. Isolated VISA were also multi-resistant but showed susceptibility to quinupristin/dalfopristin, linezolid, chloramphenicol and mupirocin. Conclusion: Detection of vancomycin resistance in Iranian S. aureus isolates emphasizes the challenges confronted by the infection control specialists in hospitals in Iran as well as causing problems in the treatment of patients with S. aureus infections.
Horieh Saderi; Mehri Habibi; Parviz Owlia; Mohammadreza Asadi Karam
Volume 3, Issue 1 , January 2008, , Pages 11-14
Abstract
Background and Objective: Methicillin resistance in Staphylococcus aureus is an increasingly important clinical problem. A chromosomal gene, mecA, mediates resistance to penicillinase-resistant penicillins such as methicillin and oxacillin in Staphylococcus aureus. We evaluated the validity of ...
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Background and Objective: Methicillin resistance in Staphylococcus aureus is an increasingly important clinical problem. A chromosomal gene, mecA, mediates resistance to penicillinase-resistant penicillins such as methicillin and oxacillin in Staphylococcus aureus. We evaluated the validity of disk diffusion test by using oxacillin, methicillin and cefoxitin disks with consideration of the presence of mecA gene as the reference method for detection of methicillin resistant Staphylococcus aureus (MRSA). Materials and Methods: The susceptibility testing of 222 S. aureus clinical isolates to oxacillin (1 µg), cefoxitin (30 µg) and methicillin (5 µg) was carried out by the disk diffusion method according to the Clinical Laboratory Standards Institute guidelines. Detection of mecA gene was performed using PCR method. Results: An amplified mecA gene of 310 bp was detected in 55% of examined strains by PCR, thus 55% strains were considered MRSA. Sensitivity of oxacillin, methicillin and cefoxitin disks were determined 100%, 99.1% and 98.3% respectively. All MRSA strains in PCR had shown resistance to penicillinase-resistant penicillins by oxacillin disk, but two and one strains were sensitive by cefoxitin and methicillin disk respectively. Thus, oxacillin was the most appropriate disk for detecting MRSA. Conclusion: The prevalence of MRSA in this study is comparable to that found in United States, Canada, Europe and Iran, but the percentage of MRSA isolates is almost twice of percentage reported from Japan.
