Teicoplanin Resistance Research Articles

Prevalence and Antibiotic Resistance Patterns of Methicillin-Resistant Staphylococcus aureus (MRSA) in a Hospital Setting: A Retrospective Study from 2018 to 2022.

Methicillin-resistant Staphylococcus aureus (MRSA) is a highly infectious pathogen that poses a serious threat to human life and health. This study aimed to provide a scientific basis for the rational clinical use of antimicrobial drugs for treating MRSA infections and inform the development of preventive and control measures by analyzing the clinical distribution and resistance characteristics of MRSA in a hospital in Hebei China. To accomplish this, bacterial identification and drug sensitivity experiments were performed with 1858 Staphylococcus aureus (S. aureus) strains collected from a hospital from January 2018 to December 2022 using a phoenixTM-100 bacterial identification drug sensitivity analyzer. The experimental data were analyzed using WHONET 5.6 software, and the MRSA strains detected were analyzed for their clinical distribution and drug resistance. Of the 1858 S. aureus strains isolated, 429 were MRSA. Sputum samples had the highest MRSA detection rates (52.45%). Critical care medicine had the highest rate of MRSA (12.59%), followed by dermatology (9.79%). MRSA resistance to tetracycline increased by 13.9% over 5years; resistance to quinupristin/dalfopristin also increased but remained low (1.9%). Resistance decreased to gentamicin, rifampicin, ciprofloxacin, and cotrimoxazole, though most significantly to erythromycin and clindamycin, exceeding 77% and 83%, respectively. No strains were resistant to vancomycin, teicoplanin, or linezolid, and drug resistance was most prevalent in patients ≥ 60years old. This study will aid in improving the diagnosis and treatment of MRSA infections.

Antibiotic resistance determination using Enterococcus faecium whole-genome sequences: a diagnostic accuracy study using genotypic and phenotypic data

DNA sequencing could become an alternative to invitro antibiotic susceptibility testing (AST) methods for determining antibiotic resistance by detecting genetic determinants associated with decreased antibiotic susceptibility. Here, we aimed to assess and improve the accuracy of antibiotic resistance determination from Enterococcus faecium genomes for diagnosis and surveillance purposes. In this retrospective diagnostic accuracy study, we first conducted a literature search in PubMed on Jan14,2021, to compile a catalogue of genes and mutations predictive of antibiotic resistance in E faecium. We then evaluated the diagnostic accuracy of this database to determine susceptibility to 12 different, clinically relevant antibiotics using a diverse population of 4382 E faecium isolates with available whole-genome sequences and invitro culture-based AST phenotypes. Isolates were obtained from various sources in 11 countries worldwide between 2000 and 2018. We included isolates tested with broth microdilution, Vitek 2, and disc diffusion, and antibiotics with at least 50 susceptible and 50 resistant isolates. Phenotypic resistance was derived from raw minimum inhibitory concentrations and measured inhibition diameters, and harmonised primarily using the breakpoints set by the European Committee on Antimicrobial Susceptibility Testing. A bioinformatics pipeline was developed to process raw sequencing reads, identify antibiotic resistance genetic determinants, and report genotypic resistance. We used our curated database, as well as ResFinder, AMRFinderPlus, and LRE-Finder, to assess the accuracy of genotypic predictions against phenotypic resistance. We curated a catalogue of 228 genetic markers involved in resistance to 12 antibiotics in E faecium. Very accurate genotypic predictions were obtained for ampicillin (sensitivity 99·7% [95% CI 99·5-99·9] and specificity 97·9% [95·8-99·0]), ciprofloxacin (98·0% [96·4-98·9] and 98·8% [95·9-99·7]), vancomycin (98·8% [98·3-99·2] and 98·8% [98·0-99·3]), andlinezolid resistance (after re-testing false negatives: 100·0% [90·8-100·0] and 98·3% [97·8-98·7]). High sensitivity was obtained for tetracycline (99·5% [99·1-99·7]), teicoplanin (98·9% [98·4-99·3]), and high-level resistance to aminoglycosides (97·7% [96·6-98·4] for streptomycin and 96·8% [95·8-97·5] for gentamicin), although at lower specificity (60-90%). Sensitivity was expectedly low for daptomycin (73·6% [65·1-80·6]) and tigecycline (38·3% [27·1-51·0]), for which the genetic basis of resistance is not fully characterised. Compared with other antibiotic resistance databases and bioinformatic tools, our curated database was similarly accurate at detecting resistance to ciprofloxacin and linezolid and high-level resistance to streptomycin and gentamicin, but had better sensitivity for detecting resistance to ampicillin, tigecycline, daptomycin, and quinupristin-dalfopristin, and better specificity for ampicillin, vancomycin, teicoplanin, and tetracycline resistance. In a validation dataset of 382 isolates, similar or improved diagnostic accuracies were also achieved. To our knowledge, this work represents the largest published evaluation to date of the accuracy of antibiotic susceptibility predictions from E faecium genomes. The results and resources will facilitate the adoption of whole-genome sequencing as a tool for the diagnosis and surveillance of antimicrobial resistance in E faecium. A complete characterisation of the genetic basis of resistance to last-line antibiotics, and the mechanisms mediating antibiotic resistance silencing, are needed to close the remaining sensitivity and specificity gaps in genotypic predictions. Wellcome Trust, UK Department of Health, British Society for Antimicrobial Chemotherapy, Academy of Medical Sciences and the Health Foundation, Medical Research Council Newton Fund, Vietnamese Ministry of Science and Technology, and European Society of Clinical Microbiology and Infectious Disease.

Australian Group on Antimicrobial Resistance (AGAR) Australian Staphylococcus aureus Surveillance Outcome Program (ASSOP) Bloodstream Infection Annual Report 2022.

From 1 January to 31 December 2022, fifty-five institutions across Australia participated in the Australian Staphylococcus aureus Surveillance Outcome Program (ASSOP). The aim of ASSOP 2022 was to determine the proportion of Staphylococcus aureus bacteraemia (SAB) isolates in Australia that were antimicrobial resistant, with particular emphasis on susceptibility to methicillin and on characterisation of the molecular epidemiology of the methicillin-resistant isolates. A total of 3,214 SAB episodes were reported, of which 77.5% were community-onset. Overall, 15.0% of S. aureus were methicillin resistant. The 30-day all-cause mortality associated with methicillin-resistant SAB was 21.4%, which was significantly different to the 16.8% all-cause mortality associated with methicillin-susceptible SAB (p = 0.02). With the exception of the β-lactams and erythromycin, antimicrobial resistance in methicillin-susceptible S. aureus was rare. However, in addition to the β-lactams, approximately 31% of methicillin-resistant S. aureus (MRSA) were resistant to ciprofloxacin; 30% to erythromycin; 13% to tetracycline; 11% to gentamicin; and 2% to co-trimoxazole. One MRSA isolate, with a daptomycin MIC of 1.5 mg/L, harboured the A302V mprF and A23V cls2 mutations. When applying the European Committee on Antimicrobial Susceptibility Testing (EUCAST) breakpoints, teicoplanin resistance was detected in one MRSA isolate. Resistance to vancomycin or linezolid was not detected. Resistance to non-β-lactam antimicrobials was largely attributable to the healthcare-associated MRSA (HA-MRSA) clone ST22-IV [2B] (EMRSA-15), and to the community-associated MRSA (CA-MRSA) clone ST45-V [5C2&5] which has acquired resistance to multiple antimicrobials including ciprofloxacin, clindamycin, erythromycin, gentamicin, and tetracycline. The ST22-IV [2B] (EMRSA-15) clone is the predominant HA-MRSA clone in Australia. Nonetheless, 86% of methicillin-resistant SAB episodes were due to CA-MRSA clones. Although polyclonal, approximately 72% of CA-MRSA clones were characterised as ST93-IV [2B] (Queensland clone); ST5-IV [2B]; ST45-V [5C2&5]; ST1-IV [2B]; ST30-IV [2B]; ST97-IV [2B]; ST953-IV [2B]; and ST8-IV [2B]. As CA-MRSA is well established in the Australian community, it is important to monitor antimicrobial resistance patterns in community- and healthcare-associated SAB as this information will guide therapeutic practices in treating S. aureus bacteraemia.

Evaluation of antibiotic susceptibility in enterococci isolated from blood culture samples

Aims: Increased vancomycin resistance in enterococci is an important cause of life-threatening bloodstream infections in hospitalized patients. The aim of this study is to determine the antibiotic susceptibility rates of Enterococcus strains isolated from blood cultures in hospitalized patients in Antalya Training and Research Hospital. 
 Methods: The antibiotic resistance rates of Enterococcus strains isolated from blood cultures of patients hospitalized in the service and intensive care units (ICU) between 1 January 2018 and 30 December 2022 were examined retrospectively. Blood samples were studied with the BacT/ALERT 3D culture system (Biomerieux, France). Bacterial identification was performed using conventional methods, Matrix Assisted Laser Desorption-Ionization Time-of-Flight Mass Spectrometer (MALDI-TOF MS) and VITEK 2 (Biomerieux, France) systems. Antimicrobial susceptibility tests were performed with VITEK 2 (Biomerieux, France) systems. Ampicillin, vancomycin, teicoplanin, high-level gentamicin resistance (HLGR) and linezolid susceptibility of isolated strains were evaluated according to the European Committee on Antimicrobial Susceptibility Testing (EUCAST) criteria. Vancomycin minimal inhibitory concentration (MIC) values of vancomycin resistant strains were studied by microdilution gradient strip test (Bioanalyse).
 Results: A total of 623 strains of enterococci were isolated from blood culture samples. Of the enterococci, 305 (48.9%) were identified as Enterococcus faecalis, 281 (45.6%) Enterococcus faecium, 12 (1.9%) Enterococcus avium, 11 (1.8%) Enterococcus gallinarum, 7 (1.2%) Enterococcus casseliflavus, 2 (0.4%) Enterococcus durans and 1 Enterococcus hirae (0.2%). Ampicillin and HLGR resistance rates of isolated E. faecalis strains were 11 (3.6%) and 72 (23.6%), respectively, and all strains were found to be susceptible to vancomycin, teicoplanin and linezolid. The ampicillin, vancomycin, teicoplanin and HLGR resistance rates of E. faecium strains were determined as 229 (81.5%), 36 (12.8%), 30 (10.7%) and 142 (50.5%), respectively, and all strains were found to be susceptible to linezolid. 
 Conclusion: In infections caused by enterococci, identification and determination of antibiotic susceptibility rates according to culture antibiogram results would be the right approach. Knowing the current susceptibility rates of enterococci isolated from blood culture samples in our hospital will contribute for clinicians' planning of empirical treatment.

Detection of Methicillin-resistant Staphylococcus aureus (MRSA) resistant to vancomycin and linezolid in bulk tank milk by E-test method

Staphylococcus aureus is considered a serious threat to public health, besides is one of the most common causes of subclinical mastitis in dairy cows. Therefore, especially methicillin-resistant Staphylococcus aureus (MRSA) is among the most critical reasons for antibiotic treatment. Monitoring the antibiotic resistance of MRSA from livestock animals and foods is of great significance. The E-test method is a suitable option for detecting antibiotics' minimum inhibition concentration (MIC) value because it is an easy and fast assay to perform. This study aimed to detect vancomycin, teicoplanin, and linezolid resistance of milk-borne 34 MRSA isolates with subclinical mastitis by the E-test method to determine MIC values. The study determined that 8.8% of MRSA isolates isolated from milk with subclinical mastitis were also resistant to vancomycin and 11.7% to linezolid, while none of the isolates were determined to be resistant to teicoplanin, according to EUCAST. The data obtained from the study reveal that the efficacy of vancomycin and linezolid antibiotics, which are commonly used against MRSA infections, are in danger. Especially before MRSA treatment, MIC values of antibiotics should be determined, and appropriate antibiotics should be used in effective doses.

Antibiotic susceptibility of staphylococcus aureus strains isolated from various clinical specimens in a tertiary hospital

Aims: Staphylococcus aureus infection rates, which are the cause of infections, have rapidly risen in both hospitals and society, constituting a concern. In this study, it was aimed to examine the antibiotic susceptibility of S. aureus strains isolated from patients treated in a tertiary state hospital for four years. Methods: A retrospective analysis was performed on S. aureus strains (n=584) identified from clinical samples delivered to the medical microbiology laboratory of Niğde Ömer Halisdemir University Training and Research Hospital for bacterial culture between 2016 and 2019. The isolates were identified by standard laboratory procedure. VITEK 2 automated system (bioMerieux, France) was used to identification and antibiotic susceptibilities of evaluate the strains. Results: Strains were most commonly isolated from wound swab (n=173) and blood culture (n=107). While the highest resistance rate was observed against Erythromycin (n=232), the least amikacin (n=16) resistant strain was determined. Vancomycin and teicoplanin resistance was not observed. Conclusion: Multi-drug resistance and MRSA resistance still exist today. The absence of vancomycin and teicoplanin resistance, in addition to the low level of trimethoprim-sulfamethoxazole resistance, is encouraging. This information about S. aureus's susceptibility may be helpful in determining how to administer antibiotics.

Reversible vancomycin susceptibility within emerging ST1421 Enterococcus faecium strains is associated with rearranged vanA-gene clusters and increased vanA plasmid copy number

Vancomycin variable enterococci (VVE) are van-positive enterococci with a vancomycin-susceptible phenotype (VVE-S) that can convert to a resistant phenotype (VVE-R) and be selected for during vancomycin exposure. VVE-R outbreaks have been reported in Canada and Scandinavian countries. The aim of this study was to examine the presence of VVE in whole genome sequenced (WGS) Australian bacteremia Enterococcus faecium (Efm) isolates collected through the Australian Group on Antimicrobial resistance (AGAR) network. Eight potential VVEAus isolates, all identified as Efm ST1421, were selected based on the presence of vanA and a vancomycin-susceptible phenotype. During vancomycin selection, two potential VVE-S harboring intact vanHAX genes, but lacking the prototypic vanRS and vanZ genes, reverted to a resistant phenotype (VVEAus-R). Spontaneous VVEAus-R reversion occurred at a frequency of 4-6 × 10−8 resistant colonies per parent cell in vitro after 48 h and led to high-level vancomycin and teicoplanin resistance. The S to R reversion was associated with a 44-bp deletion in the vanHAX promoter region and an increased vanA plasmid copy number. The deletion in the vanHAX promoter region enables an alternative constitutive promoter for the expression of vanHAX. Acquisition of vancomycin resistance was associated with a low fitness cost compared with the corresponding VVEAus-S isolate. The relative proportion of VVEAus-R vs. VVEAus-S decreased over time in serial passages without vancomycin selection. Efm ST1421 is one of the predominant VanA-Efm multilocus sequence types found across most regions of Australia, and has also been associated with a major prolonged VVE outbreak in Danish hospitals.

Changing Trends in Antimicrobial Susceptibility Patterns of Bloodstream Infection (BSI) in Secondary Care Hospitals of India.

Introduction Bloodstream infection (BSI) and subsequent sepsis are life-threatening medical conditions. The onset of antimicrobial resistance and subsequent multi-drug resistant organisms (MDRO) significantly increase healthcare-associated expenditure with adverse clinical outcomes. The present study was undertaken to identify the trends of BSI in community settings in secondary care hospitals (smaller private hospitals and district hospitals) in the state of Madhya Pradeshin Central India with the support of the Indian Council of Medical Research (ICMR) and National Health Mission, Madhya Pradesh. Methodology The present study was a prospective, longitudinal observational chart review type of study. The study was carried out at 10 secondary care hospitals (eight smaller private hospitals and two government district hospitals) nominated by the State Government as part of the ICMR Antimicrobial Resistance Surveillance and Research Network (AMRSN). The hospitals were nominated depending on the availability of a microbiology laboratory and a full-time microbiologist. Result A total of 6202 blood samples were received from patients with suspected BSI, out of which 693 samples were positive for aerobic culture. Among these, 621 (89.6%) showed bacterial growth and 72 (10.3%) grew Candida species (spp). Out of the 621 bacterial growth samples, Gram-negative bacteria were 406 (65.3%) and Gram-positive bacteria were 215 (34.6%). Among the Gram-negative isolates (406), the predominant isolate was Escherichia coli (115; 28.3%) followed by Klebsiella pneumoniae(109; 26.8%), Pseudomonas aeruginosa(61; 15%), Salmonella spp. (52; 12.8%), Acinetobacter spp. (47; 11.6%) and the other Enterobacter spp. (22; 5.4%). Among the Gram-positive isolates (215), the predominant isolate was Staphylococcus aureus(178; 82.8%) followed by Enterococcus spp. (37; 17.2%). Among the Escherichia coli, third-generation cephalosporin resistance was identified in 77.6%, piperacillin-tazobactam resistance in 45.2%, carbapenem resistance in 23.5% and colistin resistance in 16.5% of cases. Among the Klebsiella pneumoniae, third-generation cephalosporin resistance was identified in 80.7%, piperacillin-tazobactam resistance in 72.8%, carbapenem resistance in 63.3% and colistin resistance in 14% of cases. Among the Pseudomonas aeruginosa, ceftazidime resistance was identified in 61.2%, piperacillin-tazobactam resistance in 55%, carbapenem resistance in 32.8%, and colistin resistance in 38.3% of cases. Among the Acinetobacter spp., piperacillin-tazobactam resistance was identified in 72.7%, carbapenem resistance in 72.3%, and colistin resistance in 9.3% cases. While analyzing the antibiogram for Staphylococcus aureus isolates, methicillin resistance (MRSA) was seen in 70.3% of cases, followed by vancomycin resistance (VRSA) in 8% of cases and linezolid resistance in 8.1%. Among the Enterococcus spp. isolates, linezolid resistance was found in 13.5%, vancomycin resistance (VRE) in 21.6%, and teicoplanin resistance in 29.7% of cases. Conclusion In conclusion, the first-ever study to identify the risk of high-end antibiotics causing significant drug resistance in secondary and tertiary care settings has highlighted the urgent need for more randomized control studies and proactive measures from healthcare authorities and serves as a beacon for future research efforts and underscores the importance of implementing antibiograms to combat the growing threat of antibiotic resistance.

Teicoplanin-Resistant Coagulase-Negative Staphylococci: Do the Current Susceptibility Testing Methods Reliably Detect This Elusive Phenotype?

Coagulase-negative staphylococci (CoNS), members of the skin commensal microbiota, are increasingly associated with local or systemic infections due to a shift in patient populations in recent decades. Subsequently, more CoNS strains have been subjected to antibiotic susceptibility testing (AST), thus leading to the increased detection of teicoplanin resistance. However, data concerning teicoplanin resistance among CoNS strains remain limited, heterogeneous, and inconclusive. We collected 162 consecutive CoNS strains identified using Vitek-2 as teicoplanin-resistant and tested them with a range of AST methods. The results of standard and high inoculum broth microdilution (sBMD; hBMD), agar dilution (AD) after 24 h and 48 h incubation, standard and macrogradient diffusion strip (sGDT, MET), screening agar, and disc diffusion were compared to assess their robustness and to establish a diagnostic algorithm to detect teicoplanin resistance. sBMD was used as the reference method, and the lowest number of strains were teicoplanin-resistant using this method. sGDT and disc diffusion generated similar results to sBMD. Compared with sBMD, AD-24 h generated the lowest number of false teicoplanin-resistant strains, followed by hBMD, AD-48 h, and Vitek-2. sGDT, a fast, easy, affordable method in diagnostic settings, generated the highest rate of false teicoplanin-susceptible strains. Vitek-2 testing produced the highest number of teicoplanin-resistant strains. Only in two strains was the initial Vitek-2 teicoplanin resistance confirmed using five other AST methods. In conclusion, the different antibiotic susceptibility testing methods generated inconsistent, inconclusive, and discrepant results, thus making it difficult to establish a diagnostic algorithm for suspected teicoplanin resistance. Teicoplanin testing proved to be challenging and easily influenced by technical factors. This study aimed not only to raise awareness of teicoplanin resistance testing but also of the need for future studies focusing on the clinical efficacy of teicoplanin in relation to its susceptibility results.

Surgical Site Infection in Head and Neck Cancer Patients: Observations from A Tertiary Care Hospital.

Ramakrishna Pai JakribettuBackground Surgical site infections (SSIs) in head and neck cancer (HNC) patients can significantly affect the outcome of the surgery. Appropriate antimicrobial prophylaxis is needed for prevention of SSI. Aim To study the causative agents causing SSI among the HNC patients and their drug resistance pattern. Materials and Methods This was a retrospective study. The antibiotic suspectibility pattern of the aerobic bacteria isolated from the wound infection in the patients underwent surgery for head and neck cancer, admitted from January 2015 to December 2016 were added in the study. The demographic details of patients, pathogens isolated, and their antimicrobial susceptibility were collected, entered into Microsoft Excel, and statistical analysis was done as per percentage of isolates and drug resistance. Results A total of 130 culture-positive pus samples were included in the study. The majority of the samples were from males (71.5%), one-third of the patients belonged to the sixth decade of their life. Buccal mucosa and tongue were the common cancer in the head and neck region. The common gram-negative pathogens were Klebsiella sp. and Acinetobacter sp. and Staphylococcus aureus and Enterococcus sp. among the gram-positive bacteria. Methicillin-resistant S. aureus isolation rate was noted to be as high as 64.28%. High levels of resistance to aminopenicillins, third generation cephalosporins, co-trimoxazole and fluoroquinolones among the gram-negative pathogens. Anti-MRSA drugs such as vancomycin, linezolid, and teicoplanin resistance was not seen among S. aureus . Conclusion The resistance pattern among the pathogens isolated from SSI in HNC patients is alarming. So, implementation of strict infection control practices to prevent SSI rather than treating them with high end antimicrobials is the best option.

Australian Group on Antimicrobial Resistance (AGAR) Australian Staphylococcus aureus Surveillance Outcome Program (ASSOP).

From 1 January to 31 December 2021, forty-eight institutions around Australia participated in the Australian Staphylococcus aureus Surveillance Outcome Programme (ASSOP). The aim of ASSOP 2021 was to determine the proportion of Staphylococcus aureus bacteraemia (SAB) isolates in Australia that were antimicrobial resistant, with particular emphasis on susceptibility to methicillin and on characterisation of the molecular epidemiology of the methicillin-resistant isolates. A total of 2,928 SAB episodes were reported, of which 78.4% were community-onset. Overall, 16.9% of S. aureus isolates were methicillin resistant. The 30-day all-cause mortality associated with methicillin-resistant SAB was 15.0%, which was not significantly different from the 14.4% all-cause mortality associated with methicillin-susceptible SAB (p = 0.7). With the exception of the β-lactams and erythromycin, antimicrobial resistance in methicillin-susceptible S. aureus was rare. However, in addition to the β-lactams, approximately 36% of methicillin-resistant S. aureus (MRSA) were resistant to ciprofloxacin; 30% to erythromycin; 15% to tetracycline; 16% to gentamicin; and 3% to co-trimoxazole. When applying the European Committee on Antimicrobial Susceptibility Testing (EUCAST) breakpoints, teicoplanin resistance was detected in three S. aureus isolates. Resistance to vancomycin or linezolid was not detected. Resistance to non-β-lactam antimicrobials was largely attributable to the healthcare-associated MRSA (HA-MRSA) clone ST22-IV [2B] (EMRSA-15), and the community-associated MRSA (CA-MRSA) clone ST45-V [5C2&5] which has acquired multiple antimicrobial resistance determinants including ciprofloxacin, erythromycin, clindamycin, gentamicin and tetracycline. The ST22-IV [2B] (EMRSA-15) clone is the predominant HA-MRSA clone in Australia. Nonetheless, 85% of methicillin-resistant SAB episodes were due to CA-MRSA clones. Although polyclonal, approximately 68% of CA-MRSA clones were characterised as ST93-IV [2B] (Queensland clone); ST45-V [5C2&5]; ST5-IV [2B]; ST1-IV [2B]; ST30-IV [2B]; and ST97-IV [2B]. As CA-MRSA is well established in the Australian community, it is important to monitor antimicrobial resistance patterns in community- and healthcare-associated SAB as this information will guide therapeutic practices in treating S. aureus bacteraemia.

Australian Group on Antimicrobial Resistance (AGAR) Australian Staphylococcus aureus Sepsis Outcome Programme (ASSOP) Annual Report 2020.

From 1 January to 31 December 2020, forty-nine institutions around Australia participated in the Australian Staphylococcus aureus Sepsis Outcome Programme (ASSOP). The aims of ASSOP 2020 were to determine the proportion of Staphylococcus aureus bacteraemia (SAB) isolates in Australia that were antimicrobial resistant, with particular emphasis on susceptibility to methicillin; and to characterise the molecular epidemiology of the methicillin-resistant isolates. A total of 2,734 SAB episodes were reported, of which 79.7% were community-onset. Of S. aureus isolates, 17.6% were methicillin resistant. The 30-day all-cause mortality associated with methicillin-resistant SAB was 14.2%, which was not significantly different from the 13.3% mortality associated with methicillin-susceptible SAB (p = 0.6). With the exception of the β-lactams and erythromycin, antimicrobial resistance in methicillin-susceptible S. aureus was rare. However, in addition to the β-lactams, approximately 35% of methicillin-resistant S. aureus (MRSA) were resistant to erythromycin, 33% to ciprofloxacin, 13% to tetracycline, 13% to gentamicin and 4% to co-trimoxazole. When applying the European Committee on Antimicrobial Susceptibility Testing (EUCAST) breakpoints, teicoplanin resistance was detected in four S. aureus isolates. Resistance was not detected for vancomycin and linezolid. Resistance to non-beta-lactam antimicrobials was largely attributable to two healthcare-associated MRSA (HA-MRSA) clones: ST22-IV [2B] (EMRSA-15) and ST239-III [3A] (Aus-2/3 EMRSA). The ST22-IV [2B] (EMRSA-15) clone is the predominant HA-MRSA clone in Australia. However, 85% percent of methicillin-resistant SAB isolates were community-associated MRSA (CA-MRSA) clones. Although polyclonal, approximately 77% of CA-MRSA clones were characterised as: ST93-IV [2B] (Queensland CA-MRSA); ST5-IV [2B]; ST45-V [5C2&5]; ST1-IV [2B]; ST30-IV [2B]; ST8-IV [2B]; and ST97-IV [2B]. The CA-MRSA clones, in particular ST45-V [5C2&5], have acquired multiple antimicrobial resistance determinants including ciprofloxacin, erythromycin, clindamycin, gentamicin and tetracycline. The multi-resistant ST45-V [5C2&5] clone accounted for 11.0% of CA-MRSA. As CA-MRSA is well established in the Australian community, it is important to monitor antimicrobial resistance patterns in community- and healthcare-associated SAB as this information will guide therapeutic practices in treating S. aureus sepsis.

TEICOPLANIN RESISTANCE IN GRAM-POSITIVE BACTERIAL ISOLATE: AN EMERGING THREAT

Objectives: Development of antimicrobial resistance in microorganism isolated from blood stream infection constitutes a major concern about their treatment. Teicoplanin is a glycopeptide antibiotic used in the treatment of infection caused by Gram-positive bacteria. This study was planned to determine Teicoplanin resistance in the Central India and recommend policy changes for prevention of the future resistance to the higher antibiotics. Methods: A total of 1855 septicemia suspected blood samples were studied. The blood culture samples were processed and identified in the microbiology laboratory according to the Clinical and Laboratory Standards Institute guidelines. Antibiotic susceptibility test was done using Kirby B disk diffusion method. Results: About 39.5% of blood culture samples showed positive growth for organism. We observed high teicoplanin resistance (29.5%) among Gram-positive isolates, predominantly (53%) in the Enterococcus species. Conclusion: Teicoplanin resistance has emerged tremendously in the present study. Hence, attention is required about this serious issue otherwise very limited choice of antibiotics will be available for treating infections in the future.

The Prevalence and Antimicrobial Susceptibility Pattern of Gram-Positive Pathogens: Three-Year Study at a Tertiary Care Hospital in Mumbai, India

Introduction The growing resistance pattern of the gram-positive pathogens along with a steady increase in minimum inhibitory concentration of the currently available antibiotics have led to an increase in morbidity and mortality rates in India. This study aims to access the shifting antibiotic susceptibility paradigm of the gram-positive pathogens in various infections at a tertiary care center. Methods This is a 3-year retrospective observational study which was performed from January 2016 to December 2018 at a tertiary care hospital in Mumbai. All clinically significant gram-positive cocci isolated from a variety of clinical specimens were studied for their prevalence and antimicrobial susceptibility. Results Out of 4,428 gram-positive isolates, Staphylococcus aureus (35.3%) was the commonly encountered pathogen, followed by Enterococcus spp. (32.1%) and coagulase-negative Staphylococcus (CoNS) (25.7%). S. aureus was majorly isolated from skin and soft tissue infections (60.3%), followed by patients with respiratory tract infections (18.2%) and blood stream infections (13%). Among S. aureus , particularly methicillin-resistant S. aureus (MRSA), prevalence increased from 29.5% in 2016 to 35.1% in 2018, with an overall prevalence of 33.6%. All S. aureus isolates were 100% sensitive toward vancomycin, linezolid, tigecycline, and teicoplanin. However, the CoNS isolates showed a higher resistance rate with reduced susceptibility toward linezolid and teicoplanin. High prevalence of resistance was observed across gram-positive isolates with commonly used antibiotics such as ciprofloxacin, levofloxacin, and erythromycin. While the prevalence of linezolid-resistant enterococcus (LRE) was 3.6%, vancomycin (VRE) and teicoplanin resistance among the enterococcus species was as high as 7.7% and 7.5%, respectively. Conclusion Rising methicillin resistance among the Staphylococcal species (MRSA and MR-CoNS) along with reduced susceptibility toward currently available anti-MRSA agents is a matter of serious concern as it limits the therapeutic options for treating multidrug resistant (MDR) gram-positive infections.

Phenotype-Genotype Characterization and Antibiotic-Resistance Correlations Among Colonizing and Infectious Methicillin-Resistant Staphylococcus aureus Recovered from Intensive Care Units.

IntroductionMethicillin-resistant Staphylococcus aureus (MRSA) presents a profound hazard to public health. MRSA colonizing skin, mucous membranes, and the anterior nares without clinical symptoms is termed “colonizing MRSA”. Upon manifestation of clinical symptoms, it is termed “infectious MRSA”. Here, we characterize and differentiate colonizing and infectious MRSA, and analyze the phenotypic-genotypic and antibiotic susceptibility correlations.MethodologyClinical MRSA isolates were recovered from intensive care units (ICUs) of two major Egyptian hospitals and their biofilm formation ability was tested. Antibiograms against 16 antibiotics were determined, in addition to the minimum inhibitory concentrations (MICs) of vancomycin and linezolid. The entire collection was typed by enterobacterial repetitive intergenic consensus (ERIC)-PCR, as well as multi-locus sequence typing (MLST). Representative resistance and virulence genes were detected by PCR amplification.ResultsForty-nine isolates were confirmed as MRSA, of which 30 isolates were infectious and 19 were colonizing. Versatile resistance patterns were observed in both groups of isolates. We report a higher tendency for biofilm-formation and borderline minimum inhibitory concentrations among infectious isolates. A Positive antibiotic correlation was observed between susceptibility to protein synthesis inhibitors and cell wall inhibitors. Positive correlations were observed between isolation site and rifampicin resistance: nasal samples were enriched in rifampicin-resistant isolates, while urine and blood samples were enriched in susceptible ones. Furthermore, biofilm formation ability was slightly associated with amikacin resistance, and an association between teicoplanin resistance and the presence of the Panton-Valentine leukocidin gene was the only significant phenotype-genotype correlation observed. Finally, ERIC typing and MLST had congruent results.ConclusionLinezolid and vancomycin are still the most convenient choice for MRSA treatment. ERIC PCR and MLST show promising typing combination that could be easily used periodically for tracking the genotypic changes of MRSA, especially within the healthcare facilities. Several correlations were established between groups of antibiotics and the genotypes/phenotypes of the selected isolates.

Staphylococcus aureus’un Onbeş Yılda Metisilin Direnç ve Antibiyogram Direnç Profilinin ve Görülme Sıklığının Değişimi

Objective: The aim of this retrospective study was to evaluate the rate and antimicrobial resistance profile of community-acquired (CA) and hospital-acquired (HA) methicillin-resistant and sensitive Staphylococcus aureus (MRSA, MSSA) strains between 2004 and 2019. Method: Within the scope of the research, the rate of MRSA and MSSA and the change in antimicrobial resistance profile over time were investigated using two research data of 210 Staphylococcus aureus strains isolated in 2004, and 401 in 2019. Results: While any significant change was not seen in the rates of CA-MRSA (32.4%) and CA-MSSA (67.6%) in 2004, and of CA-MRSA (31.6%) and CA-MSSA (68.4%) in 2019, the prevalence of HA-MRSA decreased by 56.1% in 2004 and 30.7% in 2019 and of HA-MSSA increased by 43.9% in 2004 and 69.3% in 2019. No resistance to vancomycin and teikoplanin was observed in MRSA strains. Resistance of CA-MRSA against ciprofloxacin, levofloxacin, clindamycin and gentamicin decreased. In CA-MSSA an increase of penicillin resistance as well as a decrease in gentamicin resistance was observed. In resistance of HA-MRSA against ciprofloxacin, levofloxacin, erythromycin, clindamycin, gentamicin decreased. HA-Resistance of MSSA against fusidic acid increased and against ciprofloxacin and trimethoprim/sulfamethoxazole and erythromycin resistance decreased. Conclusion: It was found that the rate of HA-MRSA decreased during the given period of 15 years. Vancomycin or teicoplanin resistance was not observed in MRSA and MSSA. While against ciprofloxacin, levofloxacin, clindamycin, gentamicin decreased in both CA-MRSA and HA-MRSA. A closer follow-up of the prevalence and antimicrobial resistance profiles of these strains is of utmost importance for the successful control of the infections caused by MRSA and MSSA.

Çeşitli Klinik Örneklerden İzole Edilen Vankomisine Direçli Enterokok (VRE) Suşlarının Fenotipik ve Genotipik Değerlendirilmesi

Objective: Enterococci are among the important microorganism group worldwide due to their natural resistance to many antibiotics, especially their acquired resistance mechanisms against glycopeptides (vancomycin, teicoplanin). In this study, vancomycin and teicoplanin resistance were phenotypically determined in Vancomycin-resistant Enterococci strains obtained from various clinical specimens, and the presence of VanA, VanB and VanC was investigated by molecular methods. Method: A total of 30 VRE strains isolated from various clinical specimens at Microbiology Laboratory of Van Yuzuncu Yil University Faculty of Medicine Hospital between 2015 and 2018 were included in the study. MicroScan WalkAway 96 Plus (Beckman Coulter, USA) automated system was used for the identification of strains and determination of antibiotic resistance. Antimicrobial resistance to vancomycin and teicoplanin were also determined by gradient test method. Resistance genes were investigated by in-house PCR method performed in Inonu University Faculty of Medicine, Molecular Diagnostics Laboratory of The Department of Medical Microbiology using appropriate primers. Results: Identification tests revealed 29 strains as Enterococcus faecium and 1 as Enterococcus faecalis. While all strains were resistant to vancomycin and teicoplanin in the automated identification system, three isolates tested by gradient test method were found to be susceptible to these antibiotics. Molecular method of these three strains showed that there were no VanA, VanB and VanC genes. While VanA gene was detected in 27 strains, VanB gene was detected in one strain, and VanC gene was not detected. Resistance detection by gradient test and molecular method were found to be 100% compatible in the identification of vancomycinresistance in enterococci isolates. Conclusion: Gradient test method is reliable in determining glycopeptide resistance of enterococcal isolates in clinical microbiology laboratory.

Yara Yeri Örneklerinden İzole Edilen Mikroorganizmalar ve Antibiyotik Direnç Oranlar

In this study, it was aimed to contribute to available epidemiological data and guide empirical treatment by determining the distribution and antibiotic susceptibility of pathogenic microorganisms isolated from wound samples sent to the microbiology laboratory of our hospital. The agents of wound infection sent to our laboratory between 02.01.2017 and 20.07.2020 were retrospectively analyzed. The microorganisms grown were identified by conventional microbiological methods together with automated system. Antibiotic susceptibility testing was done by Kirby-Bauer disk diffusion method and an automated system and evaluated according to EUCAST criteria. Of the 956 bacteria isolated from 722 samples, 370 (39 %) were order Enterobacterales, 286 (30 %) were Gram positive cocci, 134 (14 %) were Pseudomonas spp., 83 (9 %) were Acinetobacter baumannii and 27 (3 %) were Candida spp. Vancomycin, teicoplanin and linezolid resistance were not found in staphylococci and enterococci. The most effective antibiotic against Staphylococcus aureus was trimethoprim-sulfamethoxazole (TMP-SXT) (11 %), and gentamicin (30 %) and TMP-SXT (28 %) for coagulase negative staphylococci (CNS). Ciprofloxacin (48 %) and levofloxacin (58 %) resistance was higher in enterococci compared to other antibiotics. In addition, Klebsiella spp. strains have higher resistance rates than other Enterobacterales genus strains while A. baumannii and Pseudomonas spp. strains had the lowest resistance rate against colistin (1 %). Antibiotic resistance was higher in intensive care units than in other clinics, except for enterococci. In our study, it was observed that many species of bacteria and fungi could be an agent in wound infection, and high rates of resistance developed against antibiotics. Therefore, it was thought that the treatments should be regulated by performing culture and antibiogram procedures on all samples for which wound infection is suspected.

Alternative vanHAX promoters and increased vanA-plasmid copy number resurrect silenced glycopeptide resistance in Enterococcus faecium.

BackgroundVancomycin variable enterococci (VVE) are van-positive isolates with a susceptible phenotype that can convert to a resistant phenotype during vancomycin selection.ObjectivesTo describe a vancomycin-susceptible vanA-PCR positive ST203 VVE Enterococcus faecium isolate (VVESwe-S) from a liver transplantation patient in Sweden which reverted to resistant (VVESwe-R) during in vitro vancomycin exposure.MethodsWGS analysis revealed the genetic differences between the isolates. Expression of the van-operon was investigated by qPCR. Fitness and stability of the revertant were investigated by growth measurements, competition and serial transfer.ResultsThe VVESwe-R isolate gained high-level vancomycin (MIC >256 mg/L) and teicoplanin resistance (MIC = 8 mg/L). VVESwe-S has a 5′-truncated vanR activator sequence and the VVESwe-R has in addition acquired a 44 bp deletion upstream of vanHAX in a region containing alternative putative constitutive promoters. In VVESwe-R the vanHAX-operon is constitutively expressed at a level comparable to the non-induced prototype E. faecium BM4147 strain. The vanHAX operon of VVESwe is located on an Inc18-like plasmid, which has a 3–4-fold higher copy number in VVESwe-R compared with VVESwe-S. Resistance has a low fitness cost and the vancomycin MIC of VVESwe-R decreased during in vitro serial culture without selection. The reduction in MIC was associated with a decreased vanA-plasmid copy number.ConclusionsOur data support a mechanism by which vancomycin-susceptible VVE strains may revert to a resistant phenotype through the use of an alternative, constitutive, vanR-activator-independent promoter and a vanA-plasmid copy number increase.

Phylogenomic analysis of Clostridioides difficile ribotype 106 strains reveals novel genetic islands and emergent phenotypes

Clostridioides difficile infection (CDI) is a major healthcare-associated diarrheal disease. Consistent with trends across the United States, C. difficile RT106 was the second-most prevalent molecular type in our surveillance in Arizona from 2015 to 2018. A representative RT106 strain displayed robust virulence and 100% lethality in the hamster model of acute CDI. We identified a unique 46 KB genomic island (GI1) in all RT106 strains sequenced to date, including those in public databases. GI1 was not found in its entirety in any other C. difficile clade, or indeed, in any other microbial genome; however, smaller segments were detected in Enterococcus faecium strains. Molecular clock analyses suggested that GI1 was horizontally acquired and sequentially assembled over time. GI1 encodes homologs of VanZ and a SrtB-anchored collagen-binding adhesin, and correspondingly, all tested RT106 strains had increased teicoplanin resistance, and a majority displayed collagen-dependent biofilm formation. Two additional genomic islands (GI2 and GI3) were also present in a subset of RT106 strains. All three islands are predicted to encode mobile genetic elements as well as virulence factors. Emergent phenotypes associated with these genetic islands may have contributed to the relatively rapid expansion of RT106 in US healthcare and community settings.