MLSB Phenotype Research Articles

Detection of Biofilm Production and Antibiotic Susceptibility Pattern among Clinically Isolated Staphylococcus aureus.

The increasing antibiotic resistance and the ability to form biofilms in medical devices have become the leading cause of severe infections associated with Staphylococcus aureus (S. aureus). Since the bacteria living in biofilms can exhibit 10- to 1,000-fold increase in antibiotic resistance and implicate chronic infectious diseases, the detection of S. aureus ability to form biofilms is of great importance for managing, minimizing, and effectively treating infections caused by it. This study aimed to compare the tube and tissue culture methods to detect biofilm production and antibiotic susceptibility in MRSA and MSSA. The S. aureus isolates were identified by the examination of the colony morphology, Gram staining, and various biochemical tests. Antimicrobial susceptibility testing of all isolates was performed by the modified Kirby-Bauer disc diffusion method as recommended by CLSI guidelines. MRSA screening was performed phenotypically using a cefoxitin disc (30 µg). Isolates were tested for inducible resistance using the D-test, and two phenotypic methods detected biofilm formation. Among 982 nonrepeated clinical specimens, S. aureus was isolated from 103 (10.48%). Among 103 clinical isolates of S. aureus, 54 (52.42%) isolates were MRSA, and 49 (47.57%) were MSSA. Among 54 MRSA isolates, the inducible MLSB phenotype was observed in 23/54 (42.59%) with a positive D-test. By TCP method, 26 (48.1%) MRSA isolates were strong biofilm producers, whereas, among all MSSA isolates, only 6 (12.2%) were strong biofilm producers. MRSA showed strong biofilm production in comparison with MSSA. The TCP method is a recommended reliable method to detect the biofilm among S. aureus isolates, and the TM method could be useful for the screening of biofilm production in S. aureus in the routine clinical laboratory.

Co-resistance to methicillin and clindamycin among coagulase-negative staphylococci isolates recovered from pet food in Brazil

Pet food have been considered as possible vehicles of bacterial pathogens. The sudden boom of the pet food industry due to the worldwide increase in companion animal ownership calls for pet food investigations. Herein, this study aimed to determine the frequency, antimicrobial susceptibility profile, and molecular characteristics of coagulase-negative staphylococci (CoNS) in different pet food brands in Brazil. Eighty-six pet food packages were screened for CoNS. All isolates were identified at species level by MALDI-TOF MS and species-specific PCR. Antimicrobial susceptibility testing was performed by disc diffusion and broth microdilution (vancomycin and teicoplanin only) methods. The D-test was used to screen for inducible clindamycin phenotype (MLS-B). SCCmec typing and detection of mecA, vanA, vanB, and virulence-encoding genes were done by PCR. A total of 16 (18.6 %) CoNS isolates were recovered from pet food samples. Isolates were generally multidrug-resistant (MDR). All isolates were completely resistant (100 %) to penicillin. Resistances (12.5 % - 75 %) were also observed for fluoroquinolones, sulfamethoxazole-trimethoprim, tetracycline, rifampicin, erythromycin, and tobramycin. Isolates were susceptible to vancomycin (MICs <0.25–1 μg/mL) and teicoplanin (MICs <0.25–4 μg/mL). Intriguingly, 3/8 (37.5 %) CoNS isolates with the ERYRCLIS antibiotype expressed MLS-B phenotype. All isolates harboured blaZ gene. Seven (43.8 %) isolates carried mecA; and among them, the SCCmec Type III was the most frequent (n = 5/7; 71.4 %). Isolates also harboured seb, see, seg, sej, sem, etb, tsst, pvl, and hla toxin virulence-encoding genes (6.3 % - 25 %). A total of 12/16 (75 %) isolates were biofilm producers, while the icaAB gene was detected in an S. pasteuri isolate. Herein, it is shown that pet food is a potential source of clinically important Gram-positive bacterial pathogens. To the best of our knowledge, this is the first report of MLS-B phenotype and MR-CoNS in pet food in Latin America.

Staphylococcus aureus Induced Wound Infections Which Antimicrobial Resistance, Methicillin- and Vancomycin-Resistant: Assessment of Emergence and Cross Sectional Study.

Wound infection is a prevalent concern in the medical field, being is a multi-step process involving several biological processes. Methicillin-resistant S. aureus (MRSA) and vancomycin-resistant S. aureus (VRSA) infections often occur in areas of damaged skin, such as abrasions and open wounds. This research aims to light the incidence of MRSA and VRSA in wound swabs, the antimicrobial susceptibility configuration of isolated S. aureus patterns in pus/wound samples collected from Saudi Arabian tertiary hospital. The cross section study, β- lactamase detection, VRSA genotyping, MAR index, D-test and VRSA genotyping are methods, which used for completed this research. Patients of several ages and genders delivered specimens from two hospitals in the Al jouf area, in the northern province of Saudi Arabia. S. aureus was found in 188 (34.7%) of the 542 wounds. The traumatized wounds provided 71 isolates (38.8%), surgical wound provided 49 isolates (26.8%) and abscess were represented 16 by isolates (8.7%). In the study, 123 (65.4%) out of 188 were MRSA, 60 (31.9%) were MSSA, and five (2.7%) were VRSA. Linezolid and rifampin were found to be the most effective antimicrobials with 100% in vitro antibacterial activity against S. aureus isolates. The Multiple antimicrobials resistance (MAR) index revealed 73 isolates (38.9%) with a MAR index greater than 0.2, and 115 (61.1%) less than 0.2. The D-test showed that of MLSb phenotypes among S. aureus, 22 (11.7%) strains were D-test positive (MLSbi phenotype), 53 (28.2%) strains were constitutive MLSc phenotypes, and 17 (9%) strains were shown to have MSb phenotypes. All VRSA isolates (n=5) were found to be positive for vanA, and no vanB positive isolates were detected in the study. Regular monitoring and an antimicrobials stewardship program should be in place to provide critical information that can be utilized for empirical therapy and future prevention strategies.

Prevalence of MLSB Phenotypes of &lt;i&gt;Staphylococcus aureus&lt;/i&gt; isolates in a tertiary care hospital of Delhi

Against the backdrop of the ever-changing Staphylococcal resistance pattern, clindamycin remains a viable therapeutic alternative Variation of Clindamycin drug resistance patterns with geographic area make inducible clindamycin resistance testing imperative for all staphylococcal isolates to avoid therapeutic failure. This was a prospective study conducted over a period of 1.5 years from January 2021 until June 2022. Prevalence of different MLSB Phenotypes of Staphylococcus aureus isolates was determined by standard disc diffusion method as per CLSI guidelines. Pyogenic samples received in the Microbiology lab that yielded Staphylococcus aureus were further tested for the presence of clindamycin resistance by disc diffusion method. Out of 6586 total pyogenic and respiratory specimens received in the lab, Staphylococcus aureus was yielded in 752 samples. On further testing for the MLSB phenotypes, 16.3% isolates were found to be iMLSB, 19.28% were cMLSB, 43.1% were of MSB type. ICR screening will reduce the unessential subjection of the patient to the antibiotic, and would prevent unnecessary adverse effects in the patients.

Emergence of Erythromycin-Resistant Invasive Group A Streptococcus, West Virginia, USA, 2020-2021.

Clindamycin and β-lactam antibiotics have been mainstays for treating invasive group A Streptococcus (iGAS) infection, yet such regimens might be limited for strains displaying MLSB phenotypes. We investigated 76 iGAS isolates from 66 patients in West Virginia, USA, during 2020-2021. We performed emm typing using Centers for Disease Control and Prevention guidelines and assessed resistance both genotypically and phenotypically. Median patient age was 42 (range 23-86) years. We found 76% of isolates were simultaneously resistant to erythromycin and clindamycin, including all emm92 and emm11 isolates. Macrolide resistance was conferred by the plasmid-borne ermT gene in all emm92 isolates and by chromosomally encoded ermA, ermB, and a single mefA in other emm types. Macrolide-resistant iGAS isolates were typically resistant to tetracycline and aminoglycosides. Vulnerability to infection was associated with socioeconomic status. Our results show a predominance of macrolide-resistant isolates and a shift in emm type distribution compared with historical reports.

Genetic determinants of macrolide and tetracycline resistance in penicillin non-susceptible Streptococcus pneumoniae isolates from people living with HIV in Dar es Salaam, Tanzania

BackgroundOver one million yearly deaths are attributable to Streptococcus pneumoniae and people living with HIV are particularly vulnerable. Emerging penicillin non-susceptible Streptococcus pneumoniae (PNSP) challenges therapy of pneumococcal disease. The aim of this study was to determine the mechanisms of antibiotic resistance among PNSP isolates by next generation sequencing.MethodsWe assessed 26 PNSP isolates obtained from the nasopharynx from 537 healthy human immunodeficiency virus (HIV) infected adults in Dar es Salaam, Tanzania, participating in the randomized clinical trial CoTrimResist (ClinicalTrials.gov identifier: NCT03087890, registered on 23rd March, 2017). Next generation whole genome sequencing on the Illumina platform was used to identify mechanisms of resistance to antibiotics among PNSP.ResultsFifty percent (13/26) of PNSP were resistant to erythromycin, of these 54% (7/13) and 46% (6/13) had MLSB phenotype and M phenotype respectively. All erythromycin resistant PNSP carried macrolide resistance genes; six isolates had mef(A)-msr(D), five isolates had both erm(B) and mef(A)-msr(D) while two isolates carried erm(B) alone. Isolates harboring the erm(B) gene had increased MIC (> 256 µg/mL) towards macrolides, compared to isolates without erm(B) gene (MIC 4-12 µg/mL) p < 0.001. Using the European Committee on Antimicrobial Susceptibility Testing (EUCAST) guidelines, the prevalence of azithromycin resistance was overestimated compared to genetic correlates. Tetracycline resistance was detected in 13/26 (50%) of PNSP and all the 13 isolates harbored the tet(M) gene. All isolates carrying the tet(M) gene and 11/13 isolates with macrolide resistance genes were associated with the mobile genetic element Tn6009 transposon family. Of 26 PNSP isolates, serotype 3 was the most common (6/26), and sequence type ST271 accounted for 15% (4/26). Serotypes 3 and 19 displayed high-level macrolide resistance and frequently carried both macrolide and tetracycline resistance genes.ConclusionThe erm(B) and mef(A)-msr(D) were common genes conferring resistance to MLSB in PNSP. Resistance to tetracycline was conferred by the tet(M) gene. Resistance genes were associated with the Tn6009 transposon.

Identification of Novel Mobile Genetic Elements Associated with Resistance to Macrolide and Lincosamide in Streptococcus dysgalactiae subsp. equisimilis

Background: Streptococcus dysgalactiae subsp. equisimilis (SDSE) is an important human pathogen. Recently, several studies have described the incidence of antibiotic resistance for SDSE worldwide, however, the data on the presence of corresponding genes and their possible association with mobile genetic elements are still limited. Objective: The objective of this research was to analyze the macrolide resistance in SDSE and to identify genetic determinants, mechanisms of resistance, and association with mobile genetic elements. Methods: A total of 9 SDSE strains from the collection of Joint Russian-Vietnamese Tropical Research and Technological Center (Hanoi, Vietnam) were used. These strains were previously isolated from throat swabs of children with pharyngotonsillitis in 6 provinces in Vietnam from 2012 to 2015. Antimicrobial resistance was tested by disk diffusion method. The presence of antibiotic resistance genes (ARG) was analyzed by PCR. The strains were characterized by emm typing and multilocus sequence typing (MLST). Illumina sequencing was employed for genome analysis of 4 representative SDSE isolates. Analysis of genetic elements with antibiotic resistance determinants was done using PubMed database and BLAST-searches. Artemis was used for comparative analysis of genetic elements. Results: In our study, we identified emm types that were similar to those reported in other studies. All SDSE isolates remained susceptible to penicillin, but presented alarming level of resistance to macrolides, tetracyclines, and fluoroquinolones. Most of the erythromycin-resistant strains were also characterized by clindamycin-resistance (MLSB phenotype). Both erm and different alleles of mef genes widely distributed among streptococcus pyogenes and Streptococcus pneumoniae were detected, except erm (TR) gene. The genetic elements carrying resistance determinants showed significant interspecies similarities, indicating conjugative transfer of antibiotic resistance genes between streptococcal species. Conclusion: Identification of the novel antibiotic resistance genes in SDSE indicates the necessity of monitoring of antibiotic resistance spreading and gene transfer in this bacterium.

Heterogeneous Vancomycin Intermediate Staphylococcus aureus Infections in Diabetic and Non-Diabetic Patients – A Hospital-Based Comparative Study

To study the infections caused by methicillin resistant Staphylococcus aureus (MRSA) with emphasis on heterogeneous vancomycin intermediate S. aureus (hVISA) in diabetic and non-diabetic patients and their comparison. S. aureus strains isolated from diabetic and non-diabetic patients admitted in four tertiary care hospitals in Coastal Karnataka, South India, were tested for methicillin resistance and included in the present study. Demographic and clinical data of the patients were collected using structured proforma. Antimicrobial susceptibility testing was done using the Kirby-Bauer disc diffusion method, and MLSB phenotypes were identified using the D-test. The minimum inhibitory concentration (MIC) of vancomycin was determined using agar dilution. MRSA isolates were tested for hVISA using vancomycin screen agar and population analysis profile - area under the curve (PAP-AUC) test. Statistical analysis of the results was done using the chi-square test. SPSS version 29.0 was used for this purpose. Out of 665 strains of S. aureus isolated, 220 (33.1%) were MRSA. Of these 220 MRSA strains, 122 (55.5%) and 98 (44.5%) were isolated from diabetic and non-diabetic patients, respectively. There was no significant difference in the antimicrobial resistance patterns of MRSA strains isolated from diabetic and non-diabetic patients. Foot infections and osteomyelitis caused by MRSA were significantly more among diabetic patients. Out of 220 strains of MRSA, 14 (6.4%) were hVISA. The rates of hVISA among MRSA isolated from diabetic and non-diabetic were 9.0% and 3.1%, respectively. This difference was statistically not significant. The rate of hVISA among all MRSA isolates was 6.4%. The risk of hVISA infection was three times more in diabetic patients. The results emphasize the importance of the detection of hVISA among MRSA isolates especially from diabetic patients.

Tetracycline, Macrolide and Lincosamide Resistance in Streptococcus canis Strains from Companion Animals and Its Genetic Determinants.

Growing antimicrobial resistance (AMR) in companion-animal pathogens, including Streptococcus canis (S. canis), is a significant concern for pet treatment as well for public health. Despite the importance of S. canis in veterinary and human medicine, studies concerning the AMR of this bacterium are still scarce. A total of 65 S. canis strains, isolated from dogs and cats, were assessed to test for susceptibility to six clinically relevant antimicrobials via a microdilution method. The prevalence of the selected acquired-resistance genes was also investigated via PCR. High MIC50 and MIC90 values (≥128 μg/mL) were noted for tetracycline, erythromycin and clindamycin. Only a few strains were resistant to the tested beta-lactams (6.2%). Tetracycline resistance was found in 66.2% of the strains. Resistance to erythromycin and clindamycin (ML resistance) was found in 55.4% of the strains. Strains with a phenotype showing concurrent resistance to tetracycline and ML were predominant (53.8%). AMR in the tested S. canis strains was associated with a variety of acquired and potentially transferable genes. Tetracycline resistance was conferred by tet(O) (40.0%), tet(M) (9.2%), and tet(T) (1.5%), which is reported for the first time in S. canis. In most cases, the tet(M) gene was detected in relation to the conjugative transposon Tn916. The MLSB phenotype was confirmed in the strains harboring erm(B) (43.1%) and erm(TR) (7.7%). To conclude, a high rate of S. canis strains occurring in dogs and cats displayed resistance to antimicrobials important for treatment; moreover, they are a potential reservoirs of various resistance determinants. Therefore, AMR in these pathogens should be continuously monitored, especially regarding the One Health concept.

Antibiotics Susceptibility Profile of &amp;lt;i&amp;gt;Staphylococcus aureus&amp;lt;/i&amp;gt; Clinical Isolates Collected in Hospitals in the City of Douala (Cameroon)

Introduction: Staphylococcus aureus is one of the most important agents involved in community and hospital-acquired infections. Due to the multi-drug resistance of strains to antibiotics, treatment to eradicate it is becoming more difficult and poses a global public health problem. Methodology: This was a cross-sectional study conducted from March to August 2020 in hospitals in the city of Douala, including all S. aureus isolates from diagnostic samples. Strain identification and antibiotic susceptibility testing were performed using the Vitek2 CompactTM (BioMerieux). Results: During the study period, 136 non-repetitive S. aureus strains were identified with a high frequency of methicillin-resistant S. aureus of 78.7%. The majority of the strains originated from the Douala General Hospital (66.9%) and was most frequently isolated from blood culture samples (55.1%). The study of biochemical characteristics showed that most of the strains identified had between 87% and 99% homology with the reference strain. The most active antibiotics were Quinupristin/Dalfopristin (94.2%), Linezolid (87.8%) and Vancomycin (84.2%). Methicillin resistance was associated with decreased susceptibility of S. aureus to other antibiotics such as Gentamycin (44.9%), Erythromycin (38.2%), Tetracycline (38.3%), Trimethoprim (21.4%), Ciprofloxacin (19.1%) and Levofloxacin (24.0%). Inducible MLSb and constitutive resistance phenotypes were identified with 26.7% and 22.8% respectively. Conclusion: The sensitivity of S. aureus strains differs from one antibiotic family to another, and remains good for molecules that are not available in our context. The high frequency of Methicillin-Resistant S. aureus shows the continuous progression of multi-resistant strains of S. aureus and their decreased sensitivity to usual antibiotics becomes more and more alarming.

MACROLIDE-LINCOSAMIDE-STREPTOGRAMIN B RESISTANCE AMONG STAPHYLOCOCCUS AUREUS IN CHITWAN MEDICAL COLLEGE TEACHING HOSPITAL, NEPAL

Objectives: Staphylococcus aureus is often linked with human infection. Clindamycin is one of the key substitute antimicrobial agents in the treatment of S. aureus, especially in methicillin-resistant S. aureus (MRSA) infections. Inducible macrolide-lincosamide-streptogramin B (iMLS B) resistance is a crucial factor in antimicrobial susceptibility testing. The intention of the research was to identify S. aureus from distinct clinical specimens and investigate the prevalence of inducible clindamycin resistance among them and also study their association with MRSA.&#x0D; Methods: A descriptive cross-sectional study was accomplished in the Dept. of Microbiology CMC-TH, Nepal from January 2018 to December 2020 with 525 non-repeated S. aureus obtained from a different clinical specimen. Antibiotic susceptibility test was performed by Kirby–Bauer disc diffusion method. MRSA was detected using cefoxitin (30 μg) and results were interpreted as stated by CLSI. “D-Test” was done by applying erythromycin (15 μg) and clindamycin (2 μg) as per CLSI guidelines. Data were analyzed using SPSS IBM version 20.&#x0D; Results: Among 525 isolates, there were 315 (60.00%) MRSA. Results of D test analysis showed that 280 (53.33%) were MLSB sensitive while 245 (46.67%) were MLSB resistant; where 80 (15.24%) iMLSB with D zone, 100 (19.05%) constitutive MLSB (cMLSB) phenotype, and 65 (12.38%) MS phenotype. Of a total of 80 iMLSB, a significant proportion of 64 (80.00%) was MRSA (p&lt;0.001). All the isolates were sensitive to vancomycin, teicoplanin, and linezolid. The prevalence of both iMLSB and cMLSB was high among MRSA.&#x0D; Conclusion: In this study, cMLSB phenotype was predominant (19.05%) followed by iMLSB phenotype (15.25%) and then MS phenotype (12.38%). Inducible iMLS B phenotypes, as well as cMLSB, are higher among MRSA. It is advisable to include “D-Test” as a part of regular antibiotic susceptibility testing to detect iMLSB resistance among S. aureus.

Antimicrobial profile of inducible clindamycin resistant strains of staphylococcus species

Introduction: The appearance of continuous resistant to multiple drugs among Staphylococci is a global burden due to its ability to cause severe infections. The selective use of drugs is necessary to overwhelm the situation. Taking in account present study was carried out to rule out true susceptibility of clindamycin towards staphylococcus species and its antimicrobial profile for judicial use of the drugs. Material and Methods: All the clinical samples received in the Department of microbiology were screened for Staphylococci as per standard guidelines which were further subjected to Antimicrobial susceptibility testing and D-test to detect MLSb phenotypes. Results: A total of 421 Staphylococcus species, 359(85.3%) were Staphylococcus aureus and 62(14.8%) were Coagulase negative Staphylococci; among them 42(10%) were Staphylococcus epidermidis& 20(4.8%) were Staphylococcus saprophyticus. D-test for S.aureus shows that 173(48.2%) inducible Clindamycin resistant, 113(31.5%) strains were constitutive MLSb phenotypes and 58(16.2%) strains shown to have MSb phenotypes. Among CoNS; among Staphylococcus epidermidis and S.saprophyticus 9.5% & 5% were Inducible Clindamycin resistance, 38.1% & 85% were constitutive MLSb phenotypes and 28.6%& 10% were MSb phenotypes respectively. All the isolates were sensitive to Linezolid, Vancomycin and Ceftaroline. Conclusion: Inducible clindamycin resistant strains of Staphylococci found to be among half of the strains, indicating that true susceptibility of clindamycin should be rule out on routine basis for proper institution of the therapy. Keywords: Staphylococci, MLSb phenotypes, AST.

Genomic basis of antimicrobial resistance in non-toxigenic Clostridium difficile in Southeast Asia

Despite being incapable of causing Clostridium difficile infection, non-toxigenic C. difficile (NTCD) may still be relevant. This study explored the role of NTCD as a reservoir of accessory antimicrobial resistance (AMR) genes in NTCD from Southeast Asia. This region has high rates of antimicrobial use, a high prevalence of NTCD and phenotypic AMR in such strains. More than half of the 28 NTCD strains investigated had at least one accessory AMR gene on mobile genetic elements (MGEs) which were similar to the elements found in other bacteria, including Erysipelothrix rhusiopathiae and Streptococcus suis, both of which are found in the pig gut. Thus, C. difficile may facilitate the movement of AMR genes between different hosts within a wide range of pathogenic bacteria. C. difficile β-lactamases were not located on MGEs and were unlikely to be transferred. Concordance between the MLSB resistance genotype and phenotype was low, suggesting multiple resistance mechanisms, many of which remain unknown. On the contrary, there was a high concordance between resistance genotype and phenotype for both fluoroquinolones and rifaximin. From an epidemiological perspective, NTCD populations in Southeast Asia comprised members of evolutionary clades 1 and 4, which are thought to have originated from Europe and Asia, respectively. This population structure reflects the close relationship between the people of the two regions.

Antimicrobial Resistance and Biofilm Formation by Staphylococcus aureus Isolated From Ocular Infections

Background: Untreated staphylococcal ocular infections may cause injuries in the ocular structure and lead to visual impairments, lesions in the anatomical ocular surface, and blindness. The aim of the study was to describe the characteristic of 90 Staphylococcus aureus (SA) strains from hospital and community treated ocular infections with a special emphasis on ability of biofilm formation and drug resistance. The biofilm formation was carried out using the Congo red agar (CRA) method applying Congo red dye. Studies have demonstrated that the CRA method is simple, fast, and repeatable and that modifications of some components can easily increase its accuracy. Methods: Biofilm formation was examined by the method with CRA test. On CRA, slime-producing strains formed black colonies, whereas nonproducing strains developed red colonies in 6 kinds of colors, from very red to very black: very red, red, burgundy, almost black, black, and very black. Antimicrobial susceptibility testing was performed by disc diffusion or the E-test method according to the current guidelines of the EUCAST. The MRSA, and MLSB phenotypes were detected. Polymerase chain reaction (PCR) was used to detect the mecA, and mupA genes. Erythromycin resistance genes (ermA, ermB, ermC, and msr) were detected by multiplex PCR. Results: A positive result of the CRA test was accomplished in 66.2% cases; significantly more often in hospital strains (73.4% vs 45.4%; OR, 3.3; 55% CI, 1.2–9.3). Moreover, 73.4% isolates were fully susceptible. In hospitalized patients, the level of resistance to at least 1 antimicrobial category has been identified as 40.9%, and this rate was 27.2% in outpatients. Among the tested strains, 5 (6.0%) had the resistance phenotype MRSA and 22 (26.5%) the resistance phenotype MLSB; 4 strains manifested both mechanisms; erythromycin resistance was 25.3% in those resistant to fluoroquinolones. Resistance to fluoroquinolones was 5 times more often found in ambulatory patients. All of the tested isolates were vancomycin sensitive. Conclusions: Biofilm formation is an important risk factor for developmental staphylococcal hospital-acquired ocular infections. Our results prove that hospital strains have demonstrated much greater biofilm-forming ability than nonhospital strains. Studies indicate the high efficacy of chloramphenicol and fluoroquinolones treatments, as well as the need to implement new solutions due to the aforementioned bacteria’s high resistance to neomycin and anatomic barriers difficulties.Disclosures: NoneFunding: None

Molecular Characterization, Drug Resistance and Virulence Analysis of Constitutive and Inducible Clindamycin Resistance Staphylococcus aureus Strains Recovered from Clinical Samples, Tehran-Iran.

BackgroundMacrolide-lincosamide streptogramin B family is one of the important alternative antibiotics for treating staphylococcal infections. The aim of this study was to determine the characteristics and prevalence of antibiotic resistance genes in different coagulase types of clinical Staphylococcus aureus strains.MethodsIn the present study, 86 isolates with different phenotypes of MLSB resistance were investigated. In vitro susceptibility was assessed by the disk diffusion and broth microdilution methods. PCR assays were used to detect resistance-related genes. Coagulase and SCCmec types were identified by multiplex PCR assay.ResultsThe prevalences of constitutive MLSB, inducible MLSB, and MS phenotypes were found to be 23%, 14.2%, and 4.9%, respectively. The rates of resistance to mupirocin, fusidic acid, and tigecycline were found to be 9.3%, 4.6%, and 2.3%, respectively. The top three predominant resistance genes were mecA, tet(M), erm(C) representing 75.6, 50, and 40.7% of isolates. mupA (7%), fusB (3.5%), and fusC (1.2%) genes were also detected among tested isolates. Coagulase types were mainly type II (34.9%), followed by III (32.6%), V (20.9%), and I (11.6%).ConclusionThese findings indicated high resistance rate and low genetic variability with the prominence of coa type II, highlighting the particular importance of diagnosis of these strains to avoid treatment failure.

Staphylococcus aureus in tonsils of patients with recurrent tonsillitis: prevalence, susceptibility profile, and genotypic characterization

IntroductionBacterial tonsillitis is an upper respiratory tract infection that occurs primarily in children and adolescents. Staphylococcus aureus is one of the most frequent pathogens in the etiology of tonsillitis and its relevance is due to its antimicrobial resistance and persistence in the internal tissues of the tonsils. Tonsillectomy is indicated in cases of recurrent tonsillitis after several failures of antibiotic therapy. Material and methodsIn this study we evaluated 123 surgically removed tonsils from patients who had history of recurrent tonsillitis. The tonsils were submitted to microbiological analysis for detection of S. aureus. The isolates were identified by PCR for femA gene. Antimicrobial susceptibility of the isolates was determined by disk diffusion tests. All isolates were submitted to PCR to detect mecA and Panton-Valentine leucocidin (PVL) genes. The genetic similarity among all isolates was determined by pulsed field gel electrophoresis. ResultsSixty-one S. aureus isolates were obtained from 50 patients (40.7%) with mean age of 11.7 years. The isolates showed high level resistance to penicillin (83.6%), 9.8% had inducible MLSb phenotype, and 18.0% were considered multidrug resistant (MDR). mecA gene was detected in two isolates and the gene coding for PVL was identified in one isolate. The genetic similarity analysis showed high diversity among the isolates. More than one genetically different isolate was identified from the same patient, and identical isolates were obtained from different patients. ConclusionsMDR isolates colonizing tonsils even without infection, demonstrate persistence of the bacterium and possibility of antimicrobial resistance dissemination and recurrence of infection. A specific clone in patients colonized by S. aureus was not demonstrated.

English

This work aimed at the phenotypic and molecular characterization of inducible clindamycin resistance among strains of Staphylococcus aureus isolated from cancer patients with febrile neutropenia. Out of 231clinical specimens Staphylococci were isolated from 179 (77.48%) cases. Isolates were identified by conventional microbiological methods. Antimicrobial sensitivity to all isolates was done using disc diffusion methods. For strains that were erythromycin resistant, D-test was performed to screen the presence of inducible clindamycin resistance. Multiplex polymerase chain reaction (multiplex-PCR) was done for strains with constitutive or inducible resistance to detect the distribution of erm (e), and erm (C) genes. Out of 231 clinical specimens, staphylococci were isolated from 179 (77.48%). Staphylococcal isolates were tested for susceptibility to erythromycin; 100 (55.8%) of them were erythromycin resistant. of these 100, erythromycin resistant isolates (8, 4.46%) were resistant to both erythromycin and clindamycin indicating constitutive MLSB Phenotype; 92 isolates were erythromycin resistant, and clindamycin sensitive. Out of these, 45 (25.1%) isolates showed positive D test indicating inducible MLSB phenotype while 47(26.2%) gave negative D test indicating MS phenotype. Molecular study revealed that 8 strains (100%) of staphylococci with constitutive MLSB phenotype and 23 strains (51.1%) of staphylococci with inducible MLSB phenotype had both erm(e) and erm(c) gene, erm (e) gene was present in 33.3% and erm (c) gene present in 15.6% of staphylococcus isolates with inducible MLS B phenotype. Inducible resistance and MS phenotype were found to be higher in MRSA as compared to MSSA (27.6, 24.3 and 1.6 and 4% respectively). Rapid dissemination of inducible clindamycin-resistant S. aureus isolates is worrisome and calls for judicious use of antibiotics. Therefore, the D-test should be added as a routine procedure on each staphylococcal isolates to detect inducible clindamycin resistance to avoid failure of antibiotic therapy. &nbsp; Key words: Clindamycin, Staphylococcus aureus, antimicrobial susceptibility.

Distribution of Genes Encoding Toxin, Adhesion, and Antibacterial Resistance Among Various SCCmec Types of Methicillin-Resistant Staphylococcus aureus Isolated From Intensive Care Unit, Tehran, Iran

Background: Most methicillin-resistant Staphylococcus aureus (MRSA) infections occur in health care settings; therefore, it is important to know about antimicrobial susceptibility, and carriage of virulence genes in S. aureus isolates. Objectives: The current study aimed at determining the prevalence of genes coding antimicrobial resistance, toxins, and adhesion factors among various SCCmec types of MRSA isolated from intensive care units (ICUs). Methods: From April 2016 to March 2017, a total of 200 MRSA species were isolated from various clinical samples of patients hospitalized in ICUs. The Kirby-Bauer disk diffusion method was employed to determine resistance pattern. Conventional polymerase chain reaction (PCR) assay was utilized to demonstrate antimicrobial resistance, toxins, and adhesion genes. Different SCCmec types of MRSA strains were determine by the multiplex PCR assay. Results: Antibiotic susceptibility testing revealed that all the isolates were sensitive to linezolid, teicoplanin, and vancomycin. The frequency of high-level mupirocin-resistant MRSA was 5.5%. The presence of resistance genes ant(4’)-Ia, aac(6’)-Ie/aph(2’’), tetM, msrA, ph(3’)-IIIa, ermA, msrB, ermB, ermC, and mupA were detected 73.5%, 60.5%, 57.5%, 37%, 36.5%, 34.5%, 24%, 17%, 15% and 5.5%, respectively. The most prevalent adhesion genes were clfA (93.5%) followed by clfB (90%), fnbA (81.5%), fnbB (77%), can (51%), ebp (46.5%), and bbp (2.5%). The frequency of etb, eta, pvl, and tst genes were 4.5%, 9.5%, 21.5%, and 61.5%, respectively. Inducible macrolide-lincosamide-streptogramin B (inducible MLSB resistance; iMLSB), and constitutive MLSB (cMLSB) phenotypes were observed in 88 (44%) and 26 (13%) isolates. Different SCCmec types comprising type III (56.5%), type IV (25%), type II (11%) and type I (7.5%) were identified among the MRSA strains. Conclusions: Results of the current study showed a high prevalence of resistance to commonly used antibiotics that can be a serious threat to patients hospitalized in ICUs. Also, the current study findings showed that different SCCmec types causing nosocomial infections were associated with specific antimicrobial resistance, adhesion, and toxin gene profiles.

Evaluation of Contamination of Hands of the Medical Students in a Medical Teaching Tertiary Care Hospital

Background: In the hospital, patients are often exposed to multiple procedures, invasive devices etc., increasing their chances of contracting such potential pathogens. Most of the time these potential pathogens exhibit multiple drug resistance. Aim: In view of the above factors, this study was undertaken to determine the rate of colonization of potential bacterial pathogens in the hands of final year MBBS undergraduate students. As per their clinical teaching curriculum, they visit the wards/ICU/OT, etc. on a daily basis. Method: Samples were collected from the hands of final year MBBS undergraduate students. The samples were collected by rubbing a saline wet swab stick onto the hands of the students and were inoculated onto nutrient agar plates for 18 - 24 hours at 37°C aerobically. Bacterial isolates were identified till species level by performing gram staining and biochemical reactions. Antibiotic susceptibility testing was done by Kirby-baur disc diffusion method as per CLSI guidelines 2016. Conclusion: 103 samples were collected from hands of final year undergraduate MBBS students by swab culture method. 38 showed growth and 65 showed no growth. Out of 38 isolates, 36 were Gram positive cocci and 2 were Gram positive bacilli. No Gram negative bacilli were isolated. Amongst 36 Gram positive cocci, 16 were coagulase positive Staphylococcus aureus and 20 were Coagulase negative Staphylococci (CoNS). 14 Staphylococcus aureus out of 16 were methicillin sensitive and 2 were methicillin resistant Staphylococcus aureus (MRSA). Out of 16 Staphylococcus aureus, 1 isolate showed Inducible Clindamycin Resistance (iMLSB phenotype) and 6 isolates showed complete resistance to erythromycin and clindamycin (constitutive MLSB phenotype). 1 Staphylococcus aureus which was Inducible Clindamycin Resistance (iMLSB phenotype) was also methicillin resistant.

Prevalence of inducible clindamycin resistance in erythromycin resistant clinical isolates of Staphylococcus aureus and CONS at tertiary care hospital

Background &amp; Objectives: The objective of this study was to isolate and identify Staphylococcus species from different samples clinical samples and to determine the current trend regarding the incidence and distribution of inducible clindamycin resistance in clinical isolates of Staphylococcus aureus and CONS.Materials &amp; Methods: A total of 264 isolates of staphylococcus species were isolated from various clinical samples. Clinical samples were cultured and Staphylococcus species were identified using standard microbiological methods recommended by the American Society for Microbiology (ASM). Methicillin resistance was confirmed using cefoxitin and oxacillin disks. Inducible clindamycin resistance was identified using D-zone test.Results: Among 264 erythromycin resistant staphylococcus species, 213 (80.6%) were S. aureus and 51 (19.3%) were CONS. Out of 213 erythromycin resistant isolates of S. aureus, 140 (65.7%) were MRSA and 73 (34.2%) were MSSA whereas out of 51 erythromycin resistant isolates of CONS, 28 (54.9%) were MRCNS and 23 (45%) were MSCNS. Constitutive MLSB phenotype and Inducible MLSB phenotype was higher among both MRSA and MRCNS isolates. MS phenotype was more predominant among 11 (5.1%) MSSA and 5 (9.8%) MSCNS isolates compared to 9 (4.2%) in MRSA and 2 (3.9%) in MRCNS.Conclusion: The prevalence of constitutive &amp; inducible clindamycin resistance in staphylococcus isolates was high among both MRSA and MRCNS. Hence the implementation of D-test routinely, will reveal the iMLSB &amp; cMLSB phenotype &amp; will guide the clinicians whether to use clindamycin in staphylococcal infections when erythromycin resistance is present.