Routine Susceptibility Research Articles

PREVALENCE AND ANTIMICROBIAL SUSCEPTIBILITY OF URINARY TRACT INFECTION CASES AND FINDING OF ESBL AND AMPC β-LACTAMASES PRODUCING ESCHERICHIA COLI AND KLEBSIELLA PNEUMONIAE IN A TERTIARY CARE HOSPITAL MIZORAM

Introduction: Resistance to broad spectrum -lactams mediated by extended spectrum -lactamases (ESBL) and AmpC -lactamases enzymes is a growing threat worldwide.Aim: The aim of the study was to detect the prevalence and antimicrobial susceptibility of ESBL and AmpC -lactamase producing Escherichia coli and Klebsiellapneumoniae isolated from Urinary Tract infection Materials and Methods: A total of 288 isolates comprising of 180 Escherichia coli and 108 Klebsiellapneumoniaeisolated from various clinical samples were included. ESBL was detected by Phenotypic Conrmatory Disc Diffusion Test (PCDDT) and Double Disk Synergy Test (DDST). AmpC detection was done by AmpC disk test. Results: Out of 180 Escherichia coli, and 108 Klebsiellapneumoniaeisolates 91(50.5%) and 63(58.3%) were conrmed to be ESBL producers by PCDDT and 81(45%) and 57(52.7%) by DDST respectively. AmpC was detected in 35(19.4%) of Escherichia coli and 33(30.5%) of Klebsiellapneumoniae isolates. Co-production of ESBL and AmpC was detected in 6(3.3%) Escherichia coli and 11(10.18%) of Klebsiellapneumonia isolates. Majority of ESBL producers were from blood in both organisms. Multi drug resistance (MDR) was seen in 79.1% of ESBLEscherichiacoli and 63.5% of ESBLKlebsiellapneumoniae isolates. MDR was seen in 28(96.5%) of AmpC producing Escherichia coli and all AmpC producing Klebsiellapneumoniae isolates. Conclusion: It is essential to report ESBL and AmpC beta lactamase production along with routine susceptibility which will aid the clinicians in prescribing antibiotics.Strict adherence to the hospital antibiotic policy and good infection control practices would go a long way in curtailing the menace of drug resistance.

Diarrhea-Causing Bacteria and Their Antibiotic Resistance Patterns Among Diarrhea Patients From Ghana.

Diarrheal disease remains a major global health problem particularly in children under 5 years and the emergence of antibiotic-resistant strains of causative pathogens could slow control efforts, particularly in settings where treatment options are limited. This surveillance study conducted in Ghana aimed to determine the prevalence and antimicrobial susceptibility profile of diarrhea-causing bacteria. This was a cross-sectional study carried out in five health facilities in the Ga West Municipality of Ghana between 2017 and 2021. Diarrheic stool samples from patients were collected and cultured on standard differential/selective media and isolates identified by standard biochemical tests, MALDI-TOF assay, and serological analysis. The antibiogram was determined using Kirby-Bauer disk diffusion and Microscan autoScan4 MIC panels which were used for extended-spectrum beta-lactamase (ESBL) detection. Bacteria were isolated from 97.5% (772/792) of stool samples, and 167 of the isolates were diarrheagenic and met our inclusion criteria for antimicrobial resistance (AMR) analysis. These included Escherichia coli (49.1%, 82/167), Salmonella species (23.9%, 40/167), Vibrio species (16.8%, 28/167), and Shigella species (10.2%, 17/167). Among 24 Vibrio species, we observed resistances to cefotaxime (21/24, 87.5%), ceftriaxone (20/24, 83.3%), and ciprofloxacin (6/24, 25%), including four multi-drug resistant isolates. All 13 Vibrio parahaemolyticus isolates were resistant to cefazolin. All 17 Shigella isolates were resistant to tetracycline with resistance to shigellosis drugs such as norfloxacin and ciprofloxacin. Salmonella isolates were highly susceptible to norfloxacin (40/40, 100%) and tetracycline (12/34, 35%). Two ESBL-producing E. coli were also identified with marked susceptibility to gentamicin (66/72, 91.7%) and amikacin (57/72, 79.2%) prescribed in the treatment of E. coli infections. This study showed the different bacteria implicated in diarrhea cases in Ghana and the need for differential diagnoses for better treatment outcomes. Escherichia coli, Shigella, Salmonella, and Vibrio have all been implicated in diarrhea cases in Ghana. The highest prevalence was E. coli and Salmonella with Shigella the least prevalent. Resistance to commonly used drugs found in these isolates may render bacteria infection treatment in the near future nearly impossible. Routine antimicrobial susceptibility testing, effective monitoring, and nationwide surveillance of AMR pathogens should be implemented to curb the increase of antimicrobial resistance in Ghana.

Multicenter Evaluation of a Gradient Diffusion Method for Antimicrobial Susceptibility Testing of Helicobacter pylori.

ABSTRACTHelicobacter pylori is an important human pathogen associated with peptic ulcer disease, dyspepsia, and gastric malignancy. Antimicrobial susceptibility testing (AST) is often requested for patients who fail eradication therapy. The Clinical and Laboratory Standards Institute (CLSI) reference method, agar dilution (AD), is not performed in most laboratories and maintaining organism viability during transit to a reference laboratory is difficult. We assessed the performance of the Etest (bioMérieux) as a method for H. pylori AST in comparison to AD. Etest MICs were determined for 83 H. pylori isolates at ARUP and Cleveland Clinic (CC). Categorical agreement (CA), very major, major, and minor errors (VME, ME, and mE) were determined for Etest using AD performed at Mayo Clinic Laboratories as the reference method. Testing on isolates with errors was repeated to determine final results summarized below. For clarithromycin, 66.3% of isolates were resistant (R) by AD; Etest results at each laboratory showed 1mE (1.2%) and 1 ME (3.8%). For tetracycline, only 2 isolates were R by AD; a single VME occurred at both sites (98.8% CA, 50% VME) with the same isolate. Applying EUCAST levofloxacin breakpoints to interpret ciprofloxacin results, 60.2% of isolates were R by AD; ARUP CA was 97.6% (1 ME (3%), 1 VME (2%)) and CC CA was 96.3% (1 ME (3%), 2 VMEs (4%)). Despite high error rates, the categorical agreement was acceptable (>90%) for all three antibiotics between AD and Etest. In-house susceptibility testing by gradient diffusion can allow for testing of fastidious organisms that may not survive transport to specialized laboratories; however, the method is not without technical challenges. Characterization of resistance mechanisms, increased AD dilutions, and testing from the same inoculum may determine if the observed errors reflect technical issues or breakpoints that need optimization.IMPORTANCE Routine antimicrobial susceptibility testing (AST) of Helicobacter pylori by agar dilution is difficult to perform and not practical in most clinical microbiology laboratories. The Etest gradient diffusion method can be a reliable alternative for H. pylori AST with the advantage of being a less laborious quantitative method. This work reveals that an optimized Etest method can provide acceptable performance for H. pylori AST and describes the challenges associated with this methodology.

Evaluation of the in vitro Activity and in vivo Efficacy of Anidulafungin-Loaded Human Serum Albumin Nanoparticles Against Candida albicans.

Recent decades have seen a significant increase in invasive fungal infections, resulting in unacceptably high mortality rates. Anidulafungin (AN) is the newest echinocandin and appears to have several advantages over existing antifungals. However, its poor water solubility and burdensome route of administration (i.e., repeated, long-term intravenous infusions) have limited its practical use. The objective of this study was to develop anidulafungin-loaded Human Serum Albumin (HSA) nanoparticles (NP) so as to increase both its solubility and antifungal efficacy. HSA was reduced using SDS and DTT, allowing liberation of free thiols to form the intermolecular disulfide network and nanoassembly. Reduced HSA was then added to MES buffer (0.1 M, pH 4.8) and magnetically stirred at 350 rpm and 25°C with AN (m/m 50:1) for 2 h to form nanoparticles (AN NP). We next performed routine antifungal susceptibility testing of Candida strains (n = 31) using Clinical and Laboratory Standards Institute (CLSI) methodologies. Finally, the in vivo efficacy of both AN and AN NP was investigated in a murine model of invasive infection by one of the most common fungal species—C. albicans. The results indicated that our carrier formulations successfully improved the water solubility of AN and encapsulated AN, with the latter having a particle size of 29 ± 1.5 nm with Polymer dispersity index (PDI) equaling 0.173 ± 0.039. In vitro AN NP testing revealed a stronger effect against Candida species (n = 31), with Minimum Inhibitory Concentration (MIC) values 4- to 32-fold lower than AN alone. In mice infected with Candida and having invasive candidiasis, we found that AN NP prolonged survival time (P < 0.005) and reduced fungal burden in kidneys compared to equivalent concentrations of free drug (P < 0.0001). In conclusion, the anidulafungin nanoparticles developed here have the potential to improve drug administration and therapeutic outcomes for individuals suffering from fungal diseases.

Detection of Inducible Resistance to Clindamycin among Methicillin Resistant and Sensitive strains of Staphylococcus aureus from India

The resistance to MLSB antibiotics, i.e. Macrolide-Lincosamide-Streptogramin B (MLSB), is an increasing problem among Methicillin-resistant Staphylococci. The resistance to macrolides can be by efflux mechanism or via inducible or constitutive resistance. Unfortunately, routine clindamycin susceptibility testing fails to detect the inducible resistance, which commonly results in treatment failure and necessitates incorporating a simple D-test to detect such resistance. A retrospective observational study was performed on S. aureus isolates from patients. The strains were subjected to antibiotic susceptibility testing followed by detection of mecA gene by a polymerase chain reaction and, the ‘D-test’ was performed to know the inducible resistance to clindamycin. A total of 235 isolates were identified as S. aureus. Antibiotic susceptibility test indicated 190 MRSA and 45 are sensitive to MLSB (MS). Inducible clindamycin resistance was found among 48 (20.4%) isolates and constitutive resistance in 104 (44.2%). MRSA strains had higher inducible and constitutive resistance than MSSA strains (22.1%, 51.6% and 13.3%, 13.3%, respectively). Clindamycin is a commonly used antibiotic in patients with MRSA infections to spare higher-end anti-MRSA antibiotics like linezolid and vancomycin. To detect inducible clindamycin to avoid treatment failures; the study showed the importance of incorporating the D-test in routine testing.

Inducible Clindamycin Resistance in Staphylococcus aureus isolated from pus samples in an Orthopaedic tertiary care centre.

Introduction: Clindamycin is a commonly used antibiotic to treat skin and soft tissue infectionscaused by Staphylococcus aureus particularly Methicillin-Resistant Staphylococcus aureus (MRSA)infection. In vitro routine tests for clindamycin susceptibility may fail to detect inducible clindamycinresistance due to genes resulting in treatment failure, thus necessitating the need to detect suchresistance by a simple D - test on a routine basis. Materials and Methods: 165 isolates ofStaphylococcus aureus were subjected to routine antibiotic susceptibility testing including Oxacillin(1μg) and Cefoxitin (30μg) by Kirby Bauer disc diffusion method. Inducible clindamycin resistancewas detected by D test as per CLSI guidelines on erythromycin resistant isolates. Results: 24(14.5%) isolates showed inducible clindamycin resistance, 8 (4.84%) showed constitutive resistancewhile the remaining 59 (35.75%) showed MS phenotype. Inducible clindamycin resistance and MSphenotype were found higher in MRSA (21.42%, 40.47%) as compared to MSSA (7.40%, 30.86%).Conclusion: This study showed that the D test should be used as a mandatory method in routinedisc diffusion testing to detect inducible clindamycin resistance.

Emergence of resistance to bedaquiline

Resistance to first-line anti-tuberculosis (TB) drugs continues to threaten global TB control with over 500 000 cases of rifampicin resistant (RR)-TB being reported in 2018. Treatment of RR-TB requires the use of toxic drugs often leading to adverse events, poor adherence and poor treatment outcomes. In order to address the toxicity of treatment and to improve treatment outcomes the World Health Organization has promoted the use of injection free regimens which include new and repurposed drugs: bedaquiline (BDQ), linezolid (LZD) and clofazimine (CFZ). In 2017, South Africa rolled out the inclusion of BDQ in the treatment of all pre-XDR- and XDR-TB cases as well as patients experiencing adverse events from kanamycin. In late 2018, South Africa included BDQ into three injection free regimens for treating RR-TB. This was done before routine drug susceptibility testing for BDQ could be implemented. Resistance to BDQ occurs primarily through mutations in Rv0678 (mmpR), pepQ and atpE. Understanding which mutations confer resistance and why they arise in a patient will be critical for early diagnosis as well as for preventing the emergence of resistance thereby ensuring successful treatment. Collation of the mutations identified in Rv0678 shows that BDQ resistance is largely driven by small insertions/deletions which disrupt the function of the repressor thereby leading to over expression of the efflux pump mmpL5 responsible for extruding BDQ from the cell. Understanding the association between gene mutation and phenotypic resistance remains critical for the development of new molecular diagnostics to rapidly diagnose resistance thereby affording the clinician the opportunity to adjust the regimen. Analysis of serial isolates collected from patients receiving BDQ (Access program pre-2017) has shown the emergence of mutations in Rv0678, atpE and pepQ during treatment in patients who remain culture positive after three months of treatment. Using targeted deep sequencing it is now possible to track the emergence of resistant sub-populations at the sub-phenotypic level (i.e., micro-heteroresistance) thereby affording the opportunity to study the association of the emergence of resistance with drug regimens, MIC distributions, PK and PD data and treatment outcomes. Our analysis showed that mutations conferring resistance occurred soon after the introduction of BDQ into the regimen and that clones harbouring these mutations were subsequently selected. Most surprising was the observation that different resistant sub-populations emerged during the period after the cessation of BDQ in the regimen. This demonstrates the continuing selective pressure as a result of the long half-life of BDQ. Although the origin of the distinct resistant clones is unknown, we hypothesize that resistance evolved independently in spatially separated lesions subsequently rupturing into the airways. A surprising observation was that concomitant emergence of different variants of the rpoC gene suggesting a compensatory mechanism to overcome the fitness cost of Rv0678 mutations.

Antimicrobial susceptibility pattern of pathogenic bacteria of Chronic Suppurative Otitis Media (CSOM) patients through culture and sensitivity in a tertiary level hospital in Khulna

Background: Chronic Suppurative Otitis Media (CSOM) is a chronic disease associated with irreversible consequences and serious intracranial and extracranial complications. Thereby early &amp; effective treatment must be needed to avoid such complications.&#x0D; Objectives: This study was carried out to know antimicrobial susceptibility pattern of pathogenic bacteria through culture and sensitivity for better management and to reduce resistance &amp; morbidity due to CSOM.&#x0D; Methods: After taking proper approval from hospital administration, this study was conducted on 82 patients of clinically diagnosed cases of both Tubo-tympanic &amp; Attico-antral variety of CSOM attending ENT OPD of Gazi Medical College Hospital, Khulna from January 2018 to June 2018. After proper sample collection by sterile aural swabs, they were immediately sent to the microbiology laboratory of Gazi Medical College Hospital, Khulna for bacterial culture, isolation and identification. Routine antibacterial susceptibility was done as per CLSI guidelines. SPSS 18.0 was used for statistical analysis.&#x0D; Results: The commonest pathogens isolated were Staphylococci, Coagulase Negative Staphylococci (CONS), Pseudomonas aeruginosa, Klebsiella spp. &amp; others; mostly showing susceptibility to high end antibiotics like Ceftriaxone and Amoxiclav for staphylococcal infection &amp; piperacillin-tazobactum for Pseudomonal infection.&#x0D; Conclusion: Antibiotic sensitivity pattern determines the prevalent bacterial organism causing CSOM to start empirical treatment for a successful outcome, and thus to prevent the emergence of resistant strains.&#x0D; Mediscope Vol. 7, No. 1: Jan 2020, Page 1-6

Susceptibility of Aedes aegypti and Aedes albopictus (Diptera: Culicidae) to Temephos in Thailand and Surrounding Countries.

Aedes-borne virus disease control relies on insecticides to interrupt transmission. Temephos remains a key chemical for control of immature stage Aedes in Thailand and much of Southeast Asia. However, repeated use of insecticides may result in selection for resistance in vector populations, thus compromising operational intervention. Herein, the phenotypic response to temephos by Aedes aegypti (L.) and Aedes albopictus (Skuse) collected in Thailand and surrounding countries is presented. Data from 345 collection sites are included: 283 from literature review (244 sites with Ae. aegypti, 21 with Ae. albopictus, and 18 having both species sampled), plus 62 locations with Ae. aegypti in Thailand conducted between 2014 and 2018. Susceptibility assays followed WHO guidelines using the recommended discriminating dose of temephos (0.012 mg/liter) against late third to early fourth instar Ae. aegypti. Findings revealed 34 locations with susceptible Ae. aegypti, 13 with suspected resistance, and 15 indicating resistance. Published data between 1999 and 2019 in Thailand found Ae. aegypti resistant in 73 of 206 collection sites, whereas 3 locations from 11 sampled with low-level resistant in Ae. albopictus. From surrounding countries conducting temephos assays (Cambodia, Lao PDR, Myanmar, Malaysia, and Singapore), resistance is present in Ae. aegypti and Ae. albopictus from 27 of 56 and 19 of 28 locations, respectively. Routine insecticide susceptibility monitoring should be an operational requirement in vector control programs. Given the wide distribution and apparent increase in temephos-resistance, alternative larvicidal compounds must be considered if chemical control is to remain a viable vector control strategy.

Accuracy of Nanosphere Verigene Gram-Negative Blood Culture (BC-GN) Test for Rapid Detection of Extended-Spectrum Beta-Lactamases (ESBLs) From Positive Blood Cultures

Abstract Background The rapid and accurate detection of ESBL production in Gram-negative rod (GNR) bacteremia is critical as recent data suggest that carbapenem treatment decreases mortality. At the same time, avoiding widespread empiric carbapenem prescribing is an important goal of antimicrobial stewardship teams. The aim of this retrospective review was to determine the accuracy of a nucleic acid–based test, Luminex Verigene BC-GN panel, to detect ESBL-positive GNRs direct from blood cultures. Methods The Verigene BC-GN was performed on all first positive GNR blood cultures. In addition, routine antibiotic susceptibility testing was performed on all isolates by the disk-diffusion method and included phenotypic ESBL testing using cefotaxime and ceftazidime with and without clavulanate. Escherichia coli, Klebsiella spp., and Proteus mirabilis–positive blood cultures were identified as ESBL producers through either Verigene or phenotypic disk testing. Positive GNR blood cultures from February 2016 to July 2017 were included for review. The primary objective was to determine the sensitivity and specificity of Verigene for detection of ESBLs. The secondary objective was assessing the percent of community-onset and hospital-acquired ESBL-positive blood cultures. Results There were 83 positive blood cultures with ESBL producing GNR included in the primary review. A total of 82 of 83 positive GNR blood cultures were CTX-M gene positive via Verigene (sensitivity 98.8%). All 83 cultures were confirmed as ESBL producers via phenotypic tests. There were no positive Verigene cases with negative phenotypic results. All 68 ESBL E coli–positive cultures were detected by Verigene (100%), 10 ESBL K pneumoniae (100%), and four of the five ESBL P mirabilis–positive cultures (80%). Of the 73 results available for review in the secondary objectives, 68 were community onset (93%) and five were hospital acquired (7%). Conclusion The majority of ESBL-positive blood cultures in a low-prevalence setting were due to CTX-M producers. The Luminex Verigene BC-GN was accurate in detecting ESBL-producing Enterobacteriaceae from blood cultures and can be reliably used to guide antimicrobial therapy.

Bacterial Infection in Male Infertility in Al-Anbar Province West Of Iraq.

Background: The role of bacterial infections on male infertility has always been controversial due to the lack of decisive analytical tools for examining seminal fluid specimens. As a result, these infectious processes lead to deterioration of spermatogenesis, impairment of sperm function and/or obstruction of the seminal tract. Aims of the study: To investigate the role of bacterial infections in male infertility in the province of Al - Anbar, western Iraq and their pattern of susceptibility to antibiotics in vitro. Patients and methods: Semen specimen were collected and processed in accordance with standard microbiology techniques for routine culture and antibiotic susceptibility. Results: Out of 80 semen samples, bacteriospermia was observed in 42(52.5%). E. coli took first rank of isolation (13.7%), followed by Klebsiella pneumoniae (11.2%), while Coagulase negative Staphylococcus was shown in (10%). Regarding antibiogram, E. coli was found to be susceptible to Meropenem (100%), followed by Amikacin(81.8%) and Levofloxacin (81.8%). Conclusion:We can conclude from the study that is semen culture is an important diagnostic tool for all patients undergoing fertility investigations and bacteriospermia is an important cause of infertility, and for empirical treatment levofloxacin and meropenem seems to be drug of choice. The regular screening of bacterial pathogen in infertile man seems necessary because it affects infertility in several ways

2065. Whole Genome Sequencing for Antimicrobial Resistance Prediction in MRSA and VRE: A Real-world Application

BackgroundThe antimicrobial resistance (AMR) crisis represents a serious threat to public health and the healthcare economy. The impact of increasing AMR has resulted in concentrated efforts to increased rapid molecular diagnostics of AMRs. In combination with publicly available web-based AMR databases, whole-genome sequencing (WGS) offers the capacity for detection of antibiotic resistance genes with low turnaround times and is becoming increasingly affordable. Here we sought to examine concordance between WGS-based resistance prediction and phenotypic susceptibility testing results for prospectively collected VRE and MRSA clinical isolates using publicly-available tools.MethodsMRSA and VRE isolates were prospectively collected and underwent WGS at the University of Pittsburgh Medical Center (UPMC) between December 2016 and December 2017. Antibiotic-resistant gene content was assessed by uploading assembled contigs to ResFinder, NCBI betalactamase and CARD using a BLASTn.search. Routine susceptibility was performed by Microscan™. Concordance between genotypic and phenotypic as well as sensitivity, specificity, positive and negative predictive values methods were calculated for each antibiotic/organism combination, using the phenotypic results as the gold standard. In case of discordance between the methods, repeat susceptibility using disc diffusion results was performed and was then considered to be the gold standard method.ResultsPhenotypic susceptibility testing and WGS results were available for 109 and 105 unique MRSA and VRE isolates, respectively. Out of total of 1,058 isolate/antibiotic combinations overall concordance of WGS-web-based prediction with phenotypic susceptibility methods was 99.1% with a sensitivity, specificity, PPV, NPV of 98, 99.6, 99.5, and 98.3%, respectively. Specific concordance for MRSA isolates was 98.8%. with a sensitivity, specificity, PPV and NPV of 97.6, 99.8, 99.7, and 98.5% (Table 1), while concordance for VRE isolates was 99.3%, with a sensitivity, specificity, PPV and NPV of 98.6, 98.1, 99.1, and 97.2% (Table 2). ConclusionWGS is a reliable predicator of phenotypic resistance for both MRSA and VRE.Disclosures All authors: No reported disclosures.

Validity of Cefoxitin Disc Diffusion Test for the Detection of Methicillin-resistant Staphylococcus Aureus

Definite detection of MRSA is important for proper treatment. The purpose of the present study was to measure the validity of cefoxitin disc diffusion test for the detection of methicillin-resistant Staphylococcus aureus. This cross-sectional study was carried out in the Department of Microbiology and Immunology at Bangabandhu Sheikh Mujib Medical University, Dhaka from January 2010 to December 2010 for a period of one (01) year. S. aureus isolates were collected from different clinical samples including wound swab, pus, blood, urine, tracheal aspirate, throat swab, aural swab etc. Staphylococcus aureus (S.aureus) were isolated and confirmed by staining, biochemical tests. Routine antimicrobial susceptibility testing was performed cefoxitin discs diffusion test. PCR was performed for detection of the mecA gene for MRSA. Out of the 22 suspected MRSA isolates 19 were mecA positive by PCR and all of them 19(100.0%) were resistant to cefoxitin disc diffusion. The comparison of oxacillin and cefoxitin resistance and presence of mecA gene by PCR showed that out of 22 suspected MRSA isolates 19 were mecA positive by PCR and all the 19 (100.0%) showed resistance to cefoxitin disc diffusion. The sensitivity and specificity of cefoxitin disc diffusion were 100.0% and 100.0% respectively. Cefoxitin disc diffusion test has high sensitivity and specificity for the detection of MRSA.

Incidence of Methicillin-Resistant Staphylococcus aureus Isolation from Sheep and Goat

Methicillin-resistant Staphylococcus aureus (MRSA) is a type of bacteria that is resistant to certain antibiotics including methicillin, oxacillin, penicillin and amoxicillin. Our study investigated the occurrence of Staphylococcus aureus in a total of 95 and 86 sheep and goat, respectively in different healthy conditions (apparently healthy, pneumonia, enteritis and pneumoenteritis) using routine bacteriological identification and antimicrobial susceptibility testing. The results showed that S. aureus in sheep was detected in 25, 31.25, 43.3 and 20 %, in apparently healthy, pneumonia, enteritis and pneumoenteritis cases, respectively in nasal swabs and 12.5, 20.8, 16.6 and 17.5 %, respectively in fecal swabs. While in goats, S. aureus was detected in 25, 26, 15.3, 14.2 % in apparently healthy, pneumonia, enteritis and pneumoenteritis cases, respectively in nasal swabs and 12.5, 8.3, 11.5, 14.2 %, respectively in fecal swabs. Further, the isolates were studied for their antimicrobial susceptibility patterns using 9 antibiotics commonly used. S. aureus isolated from nasal or fecal swabs from healthy sheep and goat were 100% resistant to Ampicillin, Amoxycillin and Penicillin, while S. aureus isolated from nasal and fecal swabs from sheep with pneumointeritis were 50 % resistant to Methicillin and Oxacillin. All S. aureus isolates were 100 % sensitive to Ciprofloxacin and Gentamycin making them the drugs of choice for the treatment of different disease conditions caused by S. aureus in sheep and goat.

Clinical Evaluation of Automated BACTEC MGIT 960 System for Identification, Recovery and Drug Susceptibility Testing of Mycobacterium tuberculosis Clinical Isolates

Background and Objectives: The objective of this study was to evaluate the clinical applicability of BACTEC Mycobacterial Growth Indicator Tube 960 TM system with Lowenstein-Jensen (LJ) culture for routine recovery and drug susceptibility test analysis of mycobacteria from clinical specimens. Method and Statistical Analysis: One hundred and seven clinical specimens were processed by routine laboratory procedures like p-nitro benzoic acid test and PCR amplification of IS 6110 and inoculated in LJ medium and MGIT for mycobacterial growth recovery and DST procedures. Findings: Ninety four (87.8%) samples were demonstrated reproducible result by MGIT, in which 89 (83.1%) were smear positive and all the specimens were confirmed as M. tuberculosis complex by MGIT PNB and IS 6110 PCR procedures. The observed mean time for mycobacterial detection was 9 days for primary culture and 11 days for DST in MGIT system. Applications/Improvements: The use of BACTEC MGIT 960 system was found to be a sensitive, rapid mycobacterial recovery and culture system and offers precise identification and detection of drug resistance from clinical isolates at earliest.

Assessing the Prevalence of Staphylococcus Aureus, Particularly MRSA, from Anterior Nares of Medical Students

Introduction: Staphylococcus aureus is a frequent cause of infections in both the community and hospital. Methicillin-resistant Staphylococcus aureus continues to be an important nosocomial pathogen and infections are often difficult to manage due to its resistance to multiple antibiotics. Aims and objectives: Aim of the study is to determine the nasal carriage rate of S. aureus and also to detect the antimicrobial susceptibility patterns of the isolates, which include methicillin resistance among medical students. Inclusion criteria: Medical students who have just passed 1st yr and started attending clinical postings. Exclusion criteria: History of antibiotic usage, students using nasal drops for any treatment, recent hospitalisation. Materials and methods: Nasal swabs were collected, and isolation of Staphylococcus aureus was and they were identified using conventional culture methods. Routine antibiotic susceptibility test was performed by modified Kirby-Bauer disc diffusion method by using 0.5 Mc Farland standards. Methicillin resistance is be detected by using cefoxitin disc as per CLSI guidelines. Results: Of 91 samples the nasal carriage of S.aureus is seen in 18 students (19.7%), among them MRSA is identified in 3 students (11.1%). Overall prevalence of MRSA is 3 out of 91(2.1%). Keywords: Antibiotic susceptibility testing, CLSI guide lines, Kirby-Bauer disc diffusion method, MRSA, Nasal carriage

Trends in darunavir resistance-associated mutations and phenotypic resistance in commercially tested United States clinical samples between 2006 and 2012.

HIV-1 samples submitted by clinicians from the United States for routine drug susceptibility testing (PhenoSense GT) were evaluated for genotypic and phenotypic resistance to darunavir and other protease inhibitors (PIs). Among these samples (Monogram Biosciences database January 2006-June 2012; N=78,843), isolates harboring zero IAS-USA darunavir resistance-associated mutations (RAMs) increased from 77.7% in 2006 to 92.8% through the first half of 2012 (H1 2012; upward trend, p=0.0008); a downward trend seen for samples with three or more darunavir RAMs (7.5% in 2006 and 2.6% in H1 2012; p=0.002). Among samples with any PI resistance (N=15,932), samples harboring zero darunavir RAMs gradually increased (39.9% in 2006 vs. 55.0% in H1 2012; upward trend, p=0.005), but three or more darunavir RAMs did not change over time (21.7% in 2006 and 19.2% in H1 2012; p=0.27). During this period, the frequency of the 11 individual darunavir RAMs (IAS-USA 2011 list) decreased among all samples. The frequency of each darunavir RAM in PI-resistant samples decreased or remained relatively stable. The prevalence of samples with phenotypic resistance to darunavir (partial-to-full) decreased over time in all samples (8.2% in 2006 vs. 2.3% in H1 2012), as did resistance to other PIs (p<0.006 for all PIs). Phenotypic resistance to darunavir and other PIs also decreased in PI-resistant samples (darunavir: 23.9% in 2006 vs. 17.1% in H1 2012; p<0.013 for all PIs). Since approval of darunavir in 2006, there was a significant decrease in prevalence of samples with genotypic and phenotypic resistance to darunavir in commercially tested HIV-1 isolates. Furthermore, the prevalence of phenotypic resistance to darunavir was lower than all other PIs.

Pattern of antibiotic sensitivity of bacteria causing urinary tract infection in a private medical college hospital in Dhaka

Background: Urinary tract infections (UTI), being the most common infections diagnosed in community and hospital, are to be treated scrupulously considering the type of infecting organism and its antibiotic sensitivity and resistance pattern. Aims and objectives: The aim of the present study was to observe the antibiotic sensitivity pattern of isolated uropathogens from urine samples of patients attending at Shahabuddin Medical College &amp; Hospital, Dhaka, during the period of July 2008 to June 2009. Result: A total of 555 urine samples were studied; of which 84 (15.13%) were culture positive. Among 84 culture positive cases, 84 isolates were identified. Among the isolates, E.coli was the most predominant 61 (62.88%) followed by Enterococci 11 (11.34%), proteus 4 (4.13%) and Pseudomonas 3 (3.09%). Whereas Staphylococcus saprophyticus and Klebsiella showed frequency rate of 2 (2.06%) for each. However Gram positive cocci showed lowest frequency rate of 1 (1.03%). All of the isolates were sensitive to Netilmicin. The majority of isolates were sensitive to Imipenam (92.3%) followed by Amikacin (91.1%), Meropenam (83.3 %), Tetracycline (70%). Sensitivity &amp; resistance rate were same (50%) in Vancomycin &amp; Cefodoxime. Where complete (100%) resistance was shown to Ampicillin, Azithromycin and Cefoxitin. However all isolates were poorly sensitive to cotrimoxazole (35.7%), ciprofloxacin (43%) and nitrofurantoin (44.8%). Conclusion: So, routine urine culture and susceptibility before therapy should be encouraged and periodic evaluation of predominant organisms and their antimicrobial susceptibility pattern should be studied for appropriate selection of antibiotic for effective management of UTI cases.DOI: http://dx.doi.org/10.3329/bjms.v14i1.21562 Bangladesh Journal of Medical Science Vol.14(1) 2015 p.70-74

To be or not to be? (Resistant)

Background Our laboratory changed routine antibiotic susceptibility testing from the Clinical and Laboratory Standards Institute (CLSI) to the European Committee on Antimicrobial Susceptibility Testing (EUCAST) method in August 2014. We have since observed a sudden increase in amoxicillin/clavulanate (Augmentin) resistant, beta-lactamase positive, Haemophilus influenzae . Aim This Quality Assurance Project compares H. influenzae susceptibility using breakpoints from EUCAST and CLSI methodology. The null hypothesis: EUCAST method is more sensitive, therefore increased detection of Augmentin resistant strains of H. influenzae is expected. Aim – to determine a gold standard for H. influenzae susceptibility testing. Method H. influenzae isolates were predominantly from respiratory specimens. Disc susceptibility and Augmentin E-tests were performed on every isolate using EUCAST and CLSI methods. Results The CLSI method provided consistent results; disc susceptibility correlated well with E-test results. The EUCAST results were variable; E-test results often did not correlate with disc susceptibility data. Discussion Using the EUCAST method, we identified more H. influenzae that were Augmentin resistant, beta-lactamase producers. Using the CLSI we would have mis-reported these isolates as susceptible to Augmentin. This study raises two important questions: which of the two susceptibility testing methods provides the accurate in vitro results, likely to correlate with clinical effectiveness; and, which method should be recommended for routine use in a diagnostic laboratory?

Macrolide-Lincosamide-Streptogramin B Resistance Phenotypes in Staphylococcus Aureus

Staphylococcus aureus is one of the most frequently isolated pathogens in community and hospital-acquired infections. Macrolidelincosamide-streptogramin B (MLSB) group antibiotics have frequently been preferred. In this study, it was aimed to determine MLSB group antibiotics resistance phenotypes observed in S. aureus strains. A total of 182 S. aureus strains were included in the study. Methicillin resistance was assessed using the cefoxitin (30μg) disc, MLSB resistance phenotypes were assessed using D zone test with erythromycin (15μg) and clindamycin (2μg) discs according to the Clinical and Laboratory Standards Institute (CLSI) recommendations. Of the strains included in the study, 38 (20.9%) methicillin-resistant S.aureus (MRSA) and 144 (79.1%) methicillin-susceptible S.aureus (MSSA) were identified. MLSB resistance phenotype was found in 65 (35.7%) strains. MLSB resis tance was found 84% in MRSA strains and 23% in MSSA strains: There was statistically significant between MRSA and MSSA strains. Constitutional MLSB resistance was found higher in MRSA strains (71%) and however, in MSSA strains was higher inducibleMLSB resistance (16.5%). It is suggested that, using the D test method in routine antibiotic susceptibility testing and determining resistance phenotypes in microbiology laboratories is the right approach and may play an important role in the prevention of treatment failure according to the substantial proportion of inducible resistance MLSB resistance observed.