Antibiotic susceptibility profile of Staphylococcus aureus isolates with particular reference to methicillin and inducible clindamycin resistance: Phenotypic investigation in Erbil City

Methicillin and inducible clindamycin resistance in Gram-positive cocci among GeneXpert-positive pulmonary tuberculosis patients and apparently healthy individuals in Northwest Ethiopia.

Background/Objectives: Methicillin-resistant Staphylococcus aureus (MRSA) causes hospital- and community-acquired infections. MRSA is a highly diverse strain that includes several epidemic clones, including CC45. A previous study conducted among MRSA isolates in Kuwait identified CC45 in two isolates in the early 2000s. This study provides an update on the prevalence and molecular characteristics of CC45 among MRSA isolates in Kuwait hospitals, during 2016-2022. Methods: A total of 13,276 MRSA isolates were collected during 2016-2022 and typed using antibiogram, DNA microarray, Staphylococcal protein A (spa) typing, pulsed-field gel electrophoresis (PFGE), and multi-locus sequence typing (MLST). Results: CC45 was detected in 87 (0.65%) of the 13,276 MRSA isolates. The isolates were resistant to fusidic acid (n = 71), erythromycin (n = 16), and inducible clindamycin resistance (n = 15). Twenty-one isolates were resistant to multiple antibiotics. Spa typing identified 19 types, with t362 (n = 35) and t132 (n = 27) as the dominant types. DNA microarray identified seven genotypes with CC45-MRSA-[IV + fus] (n = 36) and CC45-MRSA-[VI + fus] (n = 30) as the dominant types. MLST identified six sequence types (STs): ST7119, ST508, ST45, ST46, ST9548, and ST10699. PFGE clustered the isolates into two major types, A and B, with type A being the major type (n = 83), mostly consisting of CC45-MRSA-[IV + fus] isolates. The CC45-MRSA-[IV + fus] and CC45-MRSA-[VI + fus] genotypes were detected throughout the study period (2016-2022), whereas the other genotypes were detected less frequently. Conclusions: The CC45-MRSA circulating in Kuwait hospitals comprises genetically diverse isolates that may have originated from different sources. The emergence of multidrug resistance among the isolates poses challenges for therapy and infection prevention.

Background: Clindamycin is a reserved antibiotic used to treat infections caused by Gram-positive cocci; however, increasing bacterial resistance threatens its effectiveness. Routine antimicrobial susceptibility testing may fail to detect inducible macrolide-lincosamide-streptogramin B (iMLS B) resistance, which requires the double disc diffusion (D-test) for accurate identification. Therefore, this study aimed to use the D-test to determine the prevalence of inducible clindamycin resistance among Gram-positive cocci isolates from patients with bacterial infections at a tertiary hospital in Tanzania. Methods: A cross-sectional study was conducted among patients presenting with bacterial infections at Muhimbili National Hospital (MNH) in Tanzania from April to August 2022. Convenience sampling was used to include all eligible clinical specimens yielding Gram-positive cocci during the study period. All Gram-positive cocci isolated from the participants’ clinical specimens were subjected to antimicrobial susceptibility testing (AST) using the Kirby-Bauer disc diffusion method, and the D-test was performed to phenotypically detect iMLS B resistance. Demographic variables (age and sex), clinical specimen types, bacterial species, and antimicrobial resistance profiles were collected from patients’ records and laboratory results. Data were analyzed using Stata® Statistical Software version 15.1 (StataCorp LLC, College Station, TX, USA). Descriptive statistics were used to summarize the data, while the Chi-square test was used for analysis of categorical variables. A p-value < 0.05 was considered statistically significant. Results: A total of 246 Gram-positive cocci isolates from clinical specimens were analyzed. The majority were Coagulase-negative Staphylococci (CoNS) 64.6%, followed by Staphylococcus aureus 30.1%. The prevalence of inducible clindamycin resistance was 25.2% (95% Confidence Interval (CI) [20.2%-30.9%]). Among the Staphylococcus aureus and CoNS isolates, 39.2% (95% CI [28.9%-50.6%]) and 20.8%(95% CI [15.2%-27.7%]) exhibited the iMLS B resistance phenotype, respectively. In addition, 63.5% of Staphylococcus aureus isolates were phenotypically confirmed as methicillin-resistant Staphylococcus aureus (MRSA), and 44.7% of these isolates demonstrated the iMLS B resistance phenotype. Furthermore, 75.6% (95% CI [69.9%-80.6%]) of the Gram-positive bacterial isolates were multidrug-resistant (MDR). Conclusions: The present study demonstrated that a substantial proportion of Gram-positive cocci isolates exhibited iMLS B resistance, and the prevalence of MDR was high. These findings highlight the importance of incorporating the D-test into routine antimicrobial susceptibility testing to guide appropriate antibiotic therapy for infections caused by Gram-positive cocci. Furthermore, the results provide baseline evidence for future surveillance studies and support the need for strengthened antimicrobial stewardship programs and continued research to monitor and control antibiotic resistance in resource-limited settings.

Methicillin and Vancomycin resistance Staphylococcus aureus nasal carriage rate and antimicrobial susceptibility pattern among health care workers at Jigjiga university sheik Hassen Yebare comprehensive specialized Hospital, Jigjiga, Ethiopia.

Introduction: Methicillin-resistant Staphylococcus aureus (MRSA) is a resistant organismthat heavily contributes to hospital and community-acquired infections worldwide. It spreads very easily from patient to patient, by the hands of health workers, through contaminated objects and by air. MRSA poses a major clinical problem in treatment. So, it is essential to know its antibiotic pattern. Material & Methods: This study was carried out in the department of Microbiology at C. U. Shah Medical College and hospital, Surendranagar. Total 180 samples were included in the study during the period of 1st July 2021 to 30th June 2022. Identification of isolated organism was done by conventional method using biochemical reactions. Antimicrobial susceptibility testing and MRSA detection was done using VITEK-2 compact system. Results: Methicillin resistant Staphylococcus aureus (MRSA) was seen in 58% of the isolates. The sensitivity profile shows Tigecycline 100%, Nitrofurantoin, Linezolid and Teicoplanin 99%, Vancomycin 95%. Lower sensitivity rates were found for Levofloxacin (7%), Ciprofloxacin and Oxacillin (6%) and cefepime (2%). Inducible clindamycin resistance was found to be 37.5%. Vancomycin sensitivity was 95%, rest 4% was VISA and 1% was VRSA. Discussion: Prevalence of MRSA was found 57.78% from various clinical samples.A similar study done by Fatemeh et al and Kirti et alwas reported MRSA prevalence of 63.20% and 33.7% respectively. Conclusion: MRSA were most sensitive to Tigecycline, Linezolid, Tecoplanin , Vancomycin and least sensitive to Oxacillin and cefepime. The knowledge of antibiotic sensitivity pattern of S. aureus will therefore be helpful to get control over the evolving resistance.

We report a case of spondylodiscitis caused by methicillin-susceptible Staphylococcus pseudintermedius (MSSP) in a 23-year-old male following lumbar spine stabilization. Despite initial recovery, the patient developed postoperative infection with elevated inflammatory markers and radiological signs of spondylodiscitis. Revision surgery revealed pus extending to the osteosynthesis device. S. pseudintermedius was identified from tissue and blood cultures by MALDI-TOF MS and molecular methods. Whole-genome sequencing (WGS) of three isolates collected at different time points revealed a single clonal strain carrying multiple chromosomal resistance genes [blaZ, cat, ermB, aph-Stph, ant6, aph(3″)-III, sat4A] and a 3.1 kb plasmid of unknown function, but no mecA. Phenotypically, the isolate was susceptible to all tested antibiotics except erythromycin and exhibited inducible clindamycin resistance. Therapy began with clindamycin, later switched to daptomycin, followed by oral levofloxacin and rifampicin, achieving clinical resolution. To contextualize the isolate within the species' antimicrobial resistance (AMR) landscape, we compared its AMR gene profile with 5,500 publicly available S. pseudintermedius genomes. Thirty-four AMR genes were detected, most frequently aac6-aph2, ant6, aph2, sat, aph-Stph, blaZ, mecA, erm, tetM/tetO, cat, and dfr. Cluster analysis revealed three AMR groups: highly multidrug-resistant (clusters 1-2), intermediate (clusters 3-7), and low-AMR (clusters 8-10). Our isolate fell into cluster 7, enriched for aminoglycoside, β-lactam, macrolide, tetracycline, and phenicol resistance genes. Overall, 42.5% of genomes carried multidrug-resistant gene constellations, whereas 57.5% harbored few AMR genes, with mecA rare in low-AMR clusters. Virulence profiling of our isolate indicated diverse toxins, adhesion factors, biofilm-related autolysins, and immune evasion proteins, supporting pathogenic potential. Phylogenetic analysis using MLST and core-SNPs demonstrated high genomic diversity among S. pseudintermedius worldwide. HGW2412 belonged to the rare sequence type ST2051, previously reported only in Poland. Despite clustering with isolates from multiple continents, precise geographic inference was limited. This case highlights the value of WGS and advanced molecular diagnostics for managing S. pseudintermedius infections and underscores the need for standardized surveillance within a One Health framework.

To determine the prevalence of inducible clindamycin resistance among methicillin-resistance Staphylococcus aureus (MRSA), and to detect the presence of mecA and ermC genes among MRSA recoveredfrom hospital patients in central Nepal. Staphylococcus aureus isolated from a total of 289 clinical specimens consisting of pus and wound swabs were analyzed and identified. The MRSA strains were screened using a cefoxitin (30 µg) disc following the CLSI procedure and a double-disc test (D-test) was applied to investigate iMLSB-resistant phenotypes among the MRSA isolates. The bacterial genomic DNA was extracted and mecA and ermC genes were detected using specific primer pairs. Among the 64 S. aureus strains, 39.1% of the isolates were MRSA. The prevalence of inducible clindamycin resistance among MRSA was observed to be 48%. All MRSA (100%) isolates were resistant to penicillin and amoxicillin, whereas all strains were susceptible to linezolid, vancomycin, teicoplanin, and tigecycline. Among MRSA isolates, 8% carried the mecA gene and 13.3% of iMLSB isolates were positive for the ermC gene. A high rate of inducible clindamycin resistance among MRSA was observed. To identify the status of antibiotic resistance among S. aureus, further genomic-based studies are required.

BackgroundGroup A Streptococcus (GAS) is highly contagious and can cause invasive infections including bacteremia, sepsis, and necrotizing fasciitis. Thus, it is important to limit transmission and treat infections promptly and appropriately. In 2019, the Centers for Disease Control and Prevention (CDC) listed resistant GAS as a concerning threat due to increasing rates of clindamycin (CLI) and erythromycin (ERY) resistance. The Wadsworth Center (WC) is one of 10 laboratories in the country funded to perform GAS surveillance through the Emerging Infections Program (EIP) and receives isolates of GAS from hospitals, laboratories, and local health departments. WC also receives isolates from healthcare-associated investigations. In the past 6 years, over 2,200 GAS isolates have been received, including isolates from over 100 outbreaks.MethodsThese isolates are analyzed using multiple methods for identification and characterization, including antimicrobial resistance (AR) and whole genome sequencing (WGS). Antimicrobial susceptibility testing (AST) is performed using the bioMérieux E-test gradient strip to assess increased resistance to CLI and ERY.ResultsTo date, WC has tested over 1,400 GAS isolates and identified CLI resistance in 130 isolates and ERY resistance in 230 isolates. Inducible clindamycin resistance (ICR) in GAS can develop when the pathogen is exposed to other antibiotics, such as ERY, and can result in treatment failure. To address this concern, the ICR test is currently under validation and will be used alongside the E-test when applicable. In addition to culture AST, isolates are sent for WGS and analyzed using an AR bioinformatic gene detection pipeline to screen for genes potentially leading to AR in strains circulating in New York State (NYS). To date, this method has identified over 400 samples containing one or more AR genes. Data analysis is underway to assess the relationship between the presence of AR genes and the correlation with phenotypic AST results.ConclusionThe surveillance testing performed at WC represents an extensive testing algorithm that can be used for the identification of trends in antimicrobial resistance in GAS. Data analysis may lead to the development of new assays to improve testing algorithms at WC and other public health laboratories.DisclosuresAll Authors: No reported disclosures

Introduction: Staphylococcus aureus is a bacterium associated with the majority of Skin and Soft Tissue Infections (SSTIs). It possesses a wide range of virulence factors and an inherent ability to acquire resistance mechanisms. The incidence of drug resistance in S. aureus has increased significantly. Mupirocin is a key treatment option for decolonisation of carriers. However, rising resistance to mupirocin poses a major challenge in the decolonisation of carriers and in preventing transmission of infection to susceptible individuals. Aim: To determine the mupirocin susceptibility pattern in Staphylococcus aureus isolated from SSTIs at a tertiary care hospital. Materials and Methods: The present study was an observational, cross-sectional study conducted over a period of two years in the Department of Microbiology, Shaheed Hasan Khan Mewati Government Medical College (SHKMGMC), Nalhar, Haryana, India. Out of a total of 2,156 pus samples, 160 isolates of Staphylococcus aureus were obtained and subjected to antimicrobial susceptibility testing using the disc diffusion method. Results: Of the 160 Staphylococcus aureus isolates, 31.87% were methicillin-resistant S. aureus (MRSA). Overall mupirocin resistance was observed in 15.6% of isolates. High-level mupirocin resistance and low-level mupirocin resistance were noted in 11.87% and 3.75% of isolates, respectively. Inducible clindamycin resistance was detected in 17.5% of isolates. Coresistance to mupirocin and MRSA was observed in 10.6% of cases, while combined resistance to mupirocin, MRSA, and inducible clindamycin was seen in 1.9% of isolates. Conclusion: The proportion of mupirocin resistance was higher among MRSA isolates. A significant association was observed between high-level mupirocin resistance and MRSA.

Background: Bloodstream infections (BSIs) can cause self-limiting infections that recover within one to two days in healthy individuals to life-threatening sepsis in those with predisposing conditions. Aim: The present study aimed to assess the frequency and antibiogram of Staphylococcus spp. isolated from blood culture and further detect methicillin resistance and vancomycin resistance among the isolates. Methods: A total of 120 Staphylococcus species isolated over a period of six months from patients with BSIs were included in the study. In addition to antibiogram, vancomycin resistance was also determined using vancomycin screen agar test and E-test for determination of minimum inhibitory concentration (MIC). Results: Among the Staphylococcal isolates (n= 120), comprising of S. aureus (66.7%, n= 80) and coagulase negative Staphylococci (CoNS) (33.3%, n= 40), a total of 56 (70%) S. aureus and 24 (60%) CoNS isolates were detected as methicillin-resistant. Of the methicillin resistant CoNS, 33.3% (n=6), 50% (n=6) and 40% (n= 4) were methicillin resistant S. epidermidis, S. haemolyticus and S. hominis, respectively.  All the Staphylococcal isolates were susceptible to linezolid and minocycline. Of the MRSA isolates, two strains were found to be resistant to vancomycin by Kirby Bauer’s disc diffusion method. Additionally, D-test was done for the MRSA strains (n= 56), of which 20 (35.7%) exhibited inducible clindamycin resistance. Conclusion: This study highlights the increasing methicillin resistance in staphylococcal blood isolates. Resistance to majority of the antibiotics including vancomycin, the drug of choice for treatment of infections caused by MRSA strains, has reached alarming levels and continues to increase.

Methicillin-resistant Staphylococcus aureus (MRSA) is a major cause of community- and hospital-acquired infections which poses serious therapeutic challenges. This study aimed to evaluate the resistance patterns and genomic characteristics of S. aureus isolates from a tertiary care hospital in India. A total of 3,266 clinical specimens were processed from January 2023 to December 2024, of which 425 (13%) were S. aureus. Among them, 55.2% were MSSA and 44.8% were MRSA. MRSA isolates were categorized as community-acquired (CA-MRSA, 82.14%) or hospital-acquired (HA-MRSA, 17.85%) based on clinical data. MRSA was most frequently isolated from pus (56.8%) and wound swab (33.6%) samples. Infections were more common in men and patients aged 41-60 years. The prevalence was significantly higher in patients with diabetes (30%) than in those without diabetes (9%) (p = 0.04). PVL was detected in 63.6% of MRSA, with higher expression in CA-MRSA. The mecA gene was found in 97% of MRSA isolates, whereas mecC was present in 1.5% of isolates. MRSA showed high resistance to penicillin (100%), ciprofloxacin (70.5%), and cotrimoxazole (60%), but remained sensitive to vancomycin. MDR was observed in 96% of MRSA and 18.1% of MSSA. Inducible clindamycin resistance was detected in 54.7% of MRSA isolates. Biofilm production was noted in 49.4% of MRSA isolates, with icaA and icaD genes detected in 19% of them (p = 0.001). This study highlights the high prevalence of CA-MRSA, with significant resistance patterns and virulence markers. Continued surveillance is essential for effective infection control and ensuring antibiotic stewardship.

Antimicrobial resistance (AMR) in commensal microorganisms from companion animals represents a growing challenge within the One Health framework, as the close coexistence between pets and humans facilitates the circulation of resistance genes across species. This study aimed to characterize Staphylococcus spp. isolated from the oropharynx of dogs and cats attended at veterinary clinics in the Metropolitan Region of Recife, Pernambuco, Brazil, focusing on both phenotypic and genotypic antimicrobial resistance profiles. Oropharyngeal samples from 20 animals (13 dogs and 7 cats) were cultured on Mannitol Salt Agar, and isolates were identified by MALDI-TOF mass spectrometry. Antimicrobial susceptibility was assessed using the disk diffusion method, and resistance genes were screened by PCR. Eleven Staphylococcus isolates were identified, including S. aureus (n=2), S. felis (n=2), S. sciuri (n=2), S. warneri (n=2), S. haemolyticus (n=1), S. nepalensis (n=1), and S. simulans (n=1). Erythromycin resistance predominated (6/11; 54.5%), and all resistant isolates exhibited inducible clindamycin resistance (D-test positive). The blaZ, norA, norC, and tet(38) genes were detected, while mecA and mecC were absent. These findings demonstrate the genetic diversity of Staphylococcus spp. colonizing the oropharynx of dogs and cats and reveal the silent circulation of antimicrobial resistance determinants in companion animals. The results reinforce the need for integrated AMR surveillance connecting human, animal, and environmental health sectors to prevent the dissemination of resistance within the One Health continuum.

Researchers are still interested in the genus Staphylococcus because of its virulence and antimicrobial resistance (AMR) in different strains, which have increased infection-related morbidity and mortality. This study aimed to determine the species and distribution of methicillin-resistant, inducible clindamycin-resistant, and multidrug- resistant (MDR) staphylococci causing clinical infections in Benin City, Nigeria. Methods. Three hundred and thirty-five staphylococcal isolates were recovered from clinical specimens over one year. These isolates were identified, and antimicrobial susceptibility tests including methicillin resistance (MR), inducible clindamycin resistance (iMLSB), and vancomycin resistance were carried out using the VITEK-2 Compact System. Result. The most common species causing infections were S. aureus and S. haemolyticus. Overall, 71.2% and 89.5% of S. aureus and Coagulase-negative staphylococci (CoNS), respectively, were methicillin-resistant. Only 19.1% of the isolates were tested positive for iMLSB, with S. saprophyticus having the highest prevalence (29.4%), followed by S. aureus with 16%. A low prevalence of vancomycin resistance was observed (1.5%) as only S aureus (2.4%) and S. haemolyticus (1.7%) showed resistance. Majority of isolates were MDR (72.5%) while S. haemolyticus had the highest prevalence (94.1%). Compared with methicillin-sensitive staphylococci, methicillin-resistant staphylococci were significantly more likely to be MDR (17.2% vs 83.3%, OR=23.489 95%CI=11.093, 49.740, p < 0.0001). Concerning susceptibility profile, S. haemolyticus was the least susceptible to the tested antibacterial agents. The most active antibacterial agents against Staphylococcus spp were tigecycline (99.7), linezolid (99.1%), nitrofurantoin (98.8%), and daptomycin (96.4%), while the least active were trimethoprim-sulfamethoxazole (31.3%) and the quinolones ciprofloxacin (32.2%) and levofloxacin (33.1%). Conclusions. A high prevalence of MR-staphylococci that were MDR was observed in this study. There is a need to enact and implement antibiotic stewardship guidelines to reverse the rising tide of AMR.

ABSTRACT Background and Aim Staphylococcus aureus colonizing the nasal cavity poses a potential risk for infections. Vancomycin is a primary treatment for invasive infections caused by penicillin and methicillin‐resistant S. aureus (MRSA). However, reports of vancomycin‐resistant S. aureus (VRSA) have emerged, highlighting it as a high‐priority pathogen requiring attention. There is limited information on the epidemiology of VRSA and vancomycin‐intermediate S. aureus (VISA) from the Sidama regional state. This study aimed to determine the prevalence of VRSA and VISA among S. aureus colonizing patients admitted to Hawassa University Comprehensive Specialized Hospital (HUCSH), as well as to identify associated factors and assess the antimicrobial susceptibility profile. Methods A hospital‐based prospective cross‐sectional study was conducted from April to June 2023. Socio‐demographic and clinical data were collected using an interviewer‐administered questionnaire. Nasal swabs were obtained from 378 admitted patients, and S. aureus was identified using standard bacteriological methods. VRSA was determined using the Epsilometer test ( E ‐test), while the antimicrobial susceptibility profile was assessed using the Kirby–Bauer disk diffusion method. Data were analyzed using SPSS version 22, with a p ‐value of < 0.05 considered statistically significant. Results Out of 92 isolated S. aureus strains, 12 (13.04%) were classified as VRSA, 27 (29.3%) as VISA, and 15 (16.3%) as MRSA. The carriage rates among admitted patients were 12 (3.2%) for VRSA (95% CI: 1.7−5.5%) and 27 (7.14%) for VISA (95% CI: 4.8−10.2%). The overall nasal carriage rate of S. aureus was 92 (24.3%) (95% CI: 20.1−29%), with MRSA found in 15 (3.97%) (95% CI: 2.2−6.5%). Among the VRSA isolates, 11 (91.7%) showed susceptibility to tigecycline. Additionally, 40 (43.5%) of the S. aureus strains were positive for inducible clindamycin resistance. Patients with a history of hospitalization in the intensive care unit were 37 times more likely to be colonized with VRSA ( p = 0.001), while those with domestic animals were 22 times more likely ( p = 0.021). Conclusions This study revealed a significant proportion of VRSA and VISA among S. aureus isolates from hospitalized patients in the region. More than 80% of VRSA isolates were susceptible to tigecycline. A history of hospitalization in the intensive care unit and ownership of domestic animals were associated with an increased likelihood of VRSA colonization.

Methicillin-resistant Staphylococcus aureus (MRSA) infections of soft tissues and deep and superficial wounds affect morbidity, mortality, and healthcare resources in Saudi Arabia. The growing frequency of these infections underscore the need for effective antimicrobial stewardship projects and robust infection control. This study included patients from various age groups and was conducted in a tertiary care facility in Riyadh. Clinical specimens from different body parts were cultured, as part of the study protocol. Samples showing significant Staphylococcus aureus (S. aureus) growth were identified phenotypically and tested for microbial susceptibility. Antibiotics were evaluated and analyzed according to Clinical and Laboratory Standards Institute (CLSI) guidelines. MRSA isolates were screened using cefoxitin discs. Data was gathered and analyzed over one year, from January to December 2023. This study included 11,837 culture specimens, of which 3,795 yielded positive cultures. S. aureus was isolated in 333 cases, accounting for 2.8% of all specimens, and 8.8% of positive cultures. Most patients were male, comprising 121 study participants (36%). The highest MRSA prevalence was observed between 12 and 40 years. The prevalence of MRSA in the local healthcare environment was 3.3%. Hospitalized patients showed a slightly higher incidence of MRSA infection. MRSA prevalence was significantly associated with the specimen type (p < 0.05). Vancomycin and linezolid were 100% effective against all S. aureus strains, followed by tetracycline and gentamicin. The D-test was used to assess 307 S. aureus strains to assess inducible clindamycin resistance, 28 tested positive. The high MRSA infection load and new MRSA strains highlight the need for ongoing surveillance, stringent infection control, and targeted antibiotic stewardship programs. Our findings could be used to guide antibiotic treatment and combat antibiotic resistance in local hospitals.

BackgroundAntimicrobial resistance (AMR), particularly methicillin-resistant Staphylococcus aureus (MRSA), is a pressing global health concern. These bacteria are increasingly becoming resistant to the most commonly available treatment options. As a choice, the macrolide lincosamide-streptogramin B (MLSB) is used, with clindamycin being the preferred drug. However, an alarming number of staphylococcal strains are developing resistance to MLSB. The resistance exhibits several phenotypes, including inducible MLSB (iMLSB), constitutive MLSB (cMLSB), and macrolide streptogramin B (MSB). One of the biggest challenges is the accurate detection of iMLSB in routine laboratory tests, as they appear erythromycin-resistant and clindamycin-sensitive unless the two antibiotics are placed adjacent to each other, which leads to clinical therapeutic failure.MethodTo achieve this, double disc diffusion (D test) was used to test iMLSB phenotypically. In addition, the genetic determinants were identified through singleplex PCR using specific primers to detect erm (A, B, C) and msr genes associated with the different phenotypes of MLSB resistance.ResultAmong 161 S. aureus isolates, 42 (26.1%) were erythromycin-resistant; 25 (15.5%) showed an iMLSB phenotype, and 16 (9.9%) displayed an MSB phenotype. One MRSA isolate expressing cMLSB phenotype. Genotypic analysis revealed a prevalence of ermC in 60% and msr in 40% of S. aureus isolates.ConclusionThe D-test is a reliable method for identifying inducible clindamycin resistance in clinical diagnostics, to support antibiotic use and treatment stewardship in Qatar.

BackgroundStaphylococcus aureus remains a significant pathogen responsible for a wide range of infections. Clindamycin is frequently employed as an effective alternative for treating Staphylococcal infections. However, the emergence of antimicrobial resistance, particularly inducible clindamycin resistance (ICR), poses a substantial therapeutic challenge. Routine detection of ICR is crucial to prevent therapeutic failures and ensure appropriate use of clindamycin. Identifying a suitable substitute for erythromycin in resource-limited settings could enhance the reliability and feasibility of ICR detection in clinical laboratories. This study aimed to assess whether azithromycin could serve as a reliable alternative inducer for the detection of ICR in S. aureus and to compare its results with the standard erythromycin-induced D-test.Material and methodsA cross-sectional comparative study was carried out in a tertiary care hospital setting. A total of 216 non-duplicate clinical isolates of Staphylococcus aureus were subjected to the D-test using both erythromycin and azithromycin in combination with clindamycin. The erythromycin-induced clindamycin resistance test, as recommended by the Clinical and Laboratory Standards Institute (CLSI), served as the reference method. Interpretation of azithromycin-induced D-test results was based on adapted CLSI criteria used for erythromycin.ResultOf the 216 Staphylococcus aureus isolates tested, the iMLSB phenotype was most common with 52.31% isolates (n=113), followed by 12.03% cMLSB (n=26) and macrolide-streptogramin (MS) (17.21%, n=37). Our findings show 100% agreement between the test method (using azithromycin) and the reference method (using erythromycin) for the determination of ICR.ConclusionThis study demonstrates that azithromycin may be a viable alternative to erythromycin for detecting inducible clindamycin resistance in clinical isolates of Staphylococcus aureus. Incorporating azithromycin in routine susceptibility testing could offer a practical substitute, particularly in settings where erythromycin is unavailable.

The increase in microbial resistance to antibiotics is emerging as a challenge globally in the treatment of infections. The emergence of multiple drug-resistant microbial infections has created a severe concern for public health. Phenotypic and genotypic estimation of these resistant genes will assist in mitigating measures to curb the rising incidence The aim of this study is to isolate and characterize inducible clindamycin and methicillin co-resistant Staphylococcus aureus from clinical samples phenotypical and genotypically. Clinical samplescollected from the various hospitals were cultured on mannitol salt agar, blood agar and incubated overnight at 37oC. Colonial morphology, API identification system and standard identifications including Gram stain reaction, catalase, and coagulase were used to identify the isolates. he antibiotic susceptibility and D tests were carried out on Mueller- Hinton agar using the modified Kirby-Bauer method according to the guidelines of the Clinical Laboratory Standard Institute (CLSI). The overall occurrence of S. aureus was 75% (160/214). Multiple drug-resistant, S. aureus was 50% (81/160), methicillin resistance was 32%, (51/160), and inducible clindamycin resistance was 29.38% (47/160). The prevalence of co-resistance of inducible clindamycin and Methicillin resistance was 23.75%. The prevalence of resistance genes among the isolates with co-resistance of inducible clindamycin and methicillin resistance genes were 13.7%, 17.6, 5.9, 5.9, for Mec A, Mec C, Erm B and Erm C respectively. The highest incidence of inducible clindamycin and methicillin co-resistance was seen in urine samples. This study reveals a high level prevalence of methicillin and inducible clindamycin co- resistance among the isolates from the clinical samples studied which is a public health threat.

Background: Macrolides, lincosamides, and streptogramin B (MLSB) antibiotics act by inhibiting 50S ribosomal subunit mediated bacterial protein synthesis. Staphylococcus species exhibits resistance to MLSB antibiotics through msr (A)-mediated efflux and erm gene-mediated ribosomal modification. Clindamycin widely used for skin and soft tissue infections, due to its oral bioavailability, tissue penetration and low cost, especially against Staphylococcus species. If inducible Macrolides, lincosamides, and streptogramin B (iMLSB) goes undetected, then it can lead to therapy failure. Material and methods: This study evaluated the performance of the Vitek 2 compact system against the phenotypic D-test for detecting iMLSB in Staphylococcus isolates. All the clinical isolates of Staphylococcus species isolated during study period were included in the study. The isolates of Staphylococcus species which were resistant to erythromycin were subjected to D-test which was a gold standard test. Results: A total of 58 isolates of Staphylococcus species, were obtained during study perod. Of these Staphylococcus species, 34 isolates were S.aureus (58.62%) and 24 isolates were CONS (41.4%). Among CONS, Staphylococcus hemolyticus was the most common species (41.7%). Total 39 isolates of Staphylococcus species ( 67.24%) were resistant to erythromycin and were subjected to D-test. The iMLSB was present in 41.02% isolates of Staphylococcus species by D-test. Discrepancies were noted with Vitek 2 test which included one false-negative and one false-positive result giving a sensitivity of 93.75% and specificity of 95.65%. Conclusion: The study highlights the importance of confirming Vitek 2 results with the D-test to ensure accurate detection of iMLSB and guide effective treatment.