Standard Antimicrobial Susceptibility Testing Research Articles

Rapid Identification and Multiple Susceptibility Testing of Pathogens from Positive-Culture Sterile Body Fluids by a Combined MALDI-TOF Mass Spectrometry and Vitek Susceptibility System.

Infections of the bloodstream, central nervous system, peritoneum, joints, and other sterile areas are associated with high morbidity and sequelae risk. Timely initiation of effective antimicrobial therapy is crucial to improving patient prognosis. However, standard final identification and antimicrobial susceptibility tests (ASTs) are reported 16–48 h after a positive alert. For a rapid, effective and low-cost diagnosis, we combined matrix-assisted laser desorption/ionization time of flight mass spectrometry with a Vitek AST system, and performed rapid microbial identification (RMI) and rapid multiple AST (RMAST) on non-duplicated positive body fluid cultures collected from a hospital in Shanghai, China. Sterile body fluid positive culture and blood positive culture caused by Gram negative (GN) or polymicrobial were applied to the MALDI–TOF measurement directly. When positive blood culture caused by Gram positive (GP) bacteria or yeasts, they were resuspended in 1 ml brain heart infusion for 2 or 4 h enrichment, respectively. Regardless of enrichment, the RMI (completed in 40 min per sample) accurately identified GN and GP bacteria (98.9 and 87.2%, respectively), fungi (75.7%), and anaerobes (94.7%). Dominant species in multiple cultures and bacteria that failed to grow on the routing plates were correctly identified in 81.2 and 100% of cases, respectively. The category agreements of RMAST results, determined in the presence of various antibiotics, were similarly to previous studies. The RMI and RMAST results not only reduce the turnaround time of the patient report by 18–36 h, but also indicate whether a patient's antibiotic treatment should be accelerated, ceased or de-escalated, and adjusted the essential drugs modification for an optimized therapy.

Evaluating the Effect of Oxygen Concentrations on Antibiotic Sensitivity, Growth, and Biofilm Formation of Human Pathogens.

Standard antimicrobial susceptibility tests are performed in vitro under normal room oxygen conditions to predict the in vivo effectiveness of antimicrobial therapy. The aim of this study was to conduct a comprehensive analysis of the effect of different oxygen levels on the antibiotic susceptibility of two strains of Staphylococcus aureus, Pseudomonas aeruginosa, and Klebsiella pneumoniae. It was found that anoxic conditions caused reduced sensitivity of bacteria to aminoglycoside antibiotics in four of six bacteria used in the study. In addition, oxygen limitation decreased the susceptibility of P. aeruginosa strains and K. pneumoniae strains to piperacillin/tazobactam and azithromycin, respectively. In contrast, five of six bacteria became more susceptible to tetracycline antibiotics under oxygen-limiting conditions. Our data highlight the importance of considering the potential in vivo oxygen levels within the infection site when setting susceptibility breakpoints for evaluating the therapeutic potential of a drug and its effect on antibiotic sensitivity of the pathogen.

Etiologic Agents of Bacterial Sepsis and Their Antibiotic Susceptibility Patterns among Patients Living with Human Immunodeficiency Virus at Gondar University Teaching Hospital, Northwest Ethiopia

Background. Bacterial sepsis is a major cause of illness in human immunodeficiency virus infected patients. There is scarce evidence about sepsis among HIV patients in Ethiopia. This study aimed to determine the etiologic agents of bacterial sepsis and their antibiotic susceptibility patterns among HIV infected patients. Methods. A cross-sectional study was carried out from March 1 to May 2, 2013. One hundred patients infected with HIV and suspected of having sepsis were included. Sociodemographic data were collected by interview and blood sample was aseptically collected from study participants. All blood cultures were incubated aerobically at 35°C and inspected daily for 7 days. The positive blood cultures were identified following the standard procedures and antimicrobial susceptibility testing was performed using disk diffusion technique. Data was entered by Epi-info version 3.5.1 and analysis was done using SPSS version 20. Results. Of the study participants, 31 (31%) confirmed bacterial sepsis. The major isolates were 13 (13%) Staphylococcus aureus, 8 (8%) coagulates negative staphylococci, and 3 (3%) viridans streptococci. Majority of the isolates, 25 (80.6%), were multidrug resistant to two or more antimicrobial agents. Conclusions. Bacterial sepsis was a major cause of admission for HIV infected patients predominated by Staphylococcus aureus and coagulase negative staphylococci species and most of the isolates were multidrug resistant.

Cell-on-hydrogel platform made of agar and alginate for rapid, low-cost, multidimensional test of antimicrobial susceptibility.

Antimicrobial resistance (AMR) is a rapidly increasing threat to the effective treatment of infectious diseases worldwide. The two major remedies include: (1) using narrow-spectrum antibiotics based on rapid diagnosis; and (2) developing new antibiotics. A key part of both remedies is the antimicrobial susceptibility test (AST). However, the current standard ASTs that monitor colony formation are costly and time-consuming and the new strategies proposed are not yet practical to be implemented. Herein, we report a strategy to fabricate whole-hydrogel microfluidic chips using alginate-doped agar. This agar-based microfabrication makes it possible to prepare inexpensive hydrogel devices, and allows a seamless link between microfluidics and conventional agar-based cell culture. Different from common microfluidic systems, in our system the cells are cultured on top of the device, similar to normal agar plate culture; on the other hand, the microfluidic channels inside the hydrogel allow precise generation of linear gradient of drugs, thus giving a better performance than the conventional disk diffusion method. Cells in this system are not exposed to any shear flow, which allows the reliable tracking of individual cells and AST results to be obtained within 2-3 hours. Furthermore, our system could test the synergistic effect of drugs through two-dimensional gradient generation. Finally, the platform could be directly implemented to new drug discovery and other applications wherein a fast, cost-efficient method for studying the response of microorganisms upon drug administration is desirable.

High-Throughput Intracellular Antimicrobial Susceptibility Testing of Legionella pneumophila

Legionella pneumophila is a Gram-negative opportunistic human pathogen that causes a severe pneumonia known as Legionnaires' disease. Notably, in the human host, the organism is believed to replicate solely within an intracellular compartment, predominantly within pulmonary macrophages. Consequently, successful therapy is predicated on antimicrobials penetrating into this intracellular growth niche. However, standard antimicrobial susceptibility testing methods test solely for extracellular growth inhibition. Here, we make use of a high-throughput assay to characterize intracellular growth inhibition activity of known antimicrobials. For select antimicrobials, high-resolution dose-response analysis was then performed to characterize and compare activity levels in both macrophage infection and axenic growth assays. Results support the superiority of several classes of nonpolar antimicrobials in abrogating intracellular growth. Importantly, our assay results show excellent correlations with prior clinical observations of antimicrobial efficacy. Furthermore, we also show the applicability of high-throughput automation to two- and three-dimensional synergy testing. High-resolution isocontour isobolograms provide in vitro support for specific combination antimicrobial therapy. Taken together, findings suggest that high-throughput screening technology may be successfully applied to identify and characterize antimicrobials that target bacterial pathogens that make use of an intracellular growth niche.

Empiric treatment of neonatal sepsis in developing countries.

Infections are among the leading causes of neonatal mortality, and about 75% of the burden occurs in developing countries. Diagnosis of neonatal sepsis in these countries is dependent on the recognition of a set of nonspecific clinical signs that maximize sensitivity because staff making initial assessments may not have specialist pediatric training. Accurate diagnosis is usually limited by the unavailability of reliable microbiological investigation. The World Health Organization recommends ampicillin (or penicillin; cloxacillin if staphylococcal infection is suspected) plus gentamicin for empiric treatment of neonates with suspected clinical sepsis or meningitis. However, there is a lack of comprehensive data on the causes of infection and antimicrobial susceptibility in developing countries to support these recommendations, especially in rural settings. Bacterial pathogens (predominantly Gram negative) with reduced susceptibility to empiric medication have been reported, with variations both between and within regions. Nosocomial infections with resistant organisms and high case fatality challenge the first-line use of cephalosporins. Improving local surveillance data using standardized antimicrobial susceptibility testing methods and validation of diagnostic algorithms against microbial findings are essential. Standardized reporting of treatment outcomes is required to evaluate practice, provide guidance on second-line regimes and for studies of new approaches, such as simplified community-based regimens, and to determine the appropriate duration of empiric treatment for apparently low-risk neonates with early resolution of clinical signs, or where available, negative blood cultures. Thus, a multifaceted approach, with attention to microbiological quality assurance, is needed to better guide antimicrobial use and reduce mortality and long-term impairments.

Extended-spectrum beta-lactamase production by Enterobacteriaceae isolates from urine cultures of outpatients: results of a 7-year follow-up

The aim of the study was to evaluate the change of the frequency of extended-spectrum beta-lactamase (ESBL) producing Enterobacteriaceae isolates from urine samples of outpatients in years and to analyse the antibiotic resistance profiles for a rational drug use. The urine samples cultured in our laboratory from the patients who were admitted to outpatient clinics of our hospital between years 2007-2013 were included in this study. Enterobacteriaceae strains were isolated and identified by conventional methods and API 20E system (BioMérieux, France). The standard antimicrobial susceptibility tests were performed by Kirby Bauer disk diffusion method. ESBL production were screened by double-disk synergy method according to CLSI guidelines. E-test method (BioMérieux, France) were used for the verification of suspicious ESBL production. The identification and antimicrobial susceptibility testing were performed for a total of 12.535 isolates. Of the isolates 8716 were identified as Escherichia coli (69.3%), 1514 were Klebsiella pneumoniae/oxytoca (12.1%), 257 were Proteus mirabilis (2.1%), 345 were other Enterobacteriae members (8%), 411 were various non-fermentative gram-negative bacteria (3.3%) and 1292 were various gram-positive bacteria (10.3%). The total positivity rate of ESBL was found as 21.8% (2.283/10.487), and the ESBL positive rates for E.coli, K.pneumoniae/oxytoca and P.mirabilis were 21.2%, 28.2% and 4.7%, respectively. Other Enterobacteriaceae isolates were not evaluated because of the absence of standardized methods and breakpoint values. There was no statistically significant difference among ESBL producing isolates within seven years (p= 0.364). The antibiotic resistance rates of the ESBL-positive isolates were statistically higher than ESBL-negative isolates [amoxicillin-clavulanate (73.1%/11.3%), trimethoprim-sulfamethoxazole (63.1%/31.0%), nitrofurantoin (17.3%/8.6%), gentamicin (42.2%/10.1%), amikacin (3.5%/0.9%), tobramisin (56.8%/10.5%), imipenem (0.3%/0.1%), ofloxacin (66.8%/19.8%), ticarcillin-clavulanate (73.5%/19.8%), piperacillin-tazobactam (28.8%/5.0%)] (p< 0.05). Statistically significant variations were detected within the years for the resistance rates of amoxicillin-clavulanate (p= 0.001), tobramycin (p=0.003), ofloxacin (p= 0.001), ticarcillin-clavulanate (p= 0.001) and piperacillin-tazobactam (p= 0.001) were detected within the years. Although a quite high percentage of ESBL positivity in Enterobacteriaceae isolates was determined, there was a slight but not statistically significant increase of this value during the seven-year period. The stability of the percentage of ESBL positivity may indicate a positive change in the habit of the usage of beta-lactam antibiotics. According to the results of our study, the most effective drugs for ESBL-producing isolates were piperacillin-tazobactam among inhibitor combinations, amikacin among aminoglycosides and nitrofurantoin among orally-used drugs.

Standard versus biofilm antimicrobial susceptibility testing to guide antibiotic therapy in cystic fibrosis.

The antibiotics used to treat pulmonary infections in people with cystic fibrosis are typically chosen based on the results of antimicrobial susceptibility testing performed on bacteria traditionally grown in a planktonic mode (grown in a liquid). However, there is considerable evidence to suggest that Pseudomonas aeruginosa actually grows in a biofilm (or slime layer) in the airways of people with cystic fibrosis with chronic pulmonary infections. Therefore, choosing antibiotics based on biofilm rather than conventional antimicrobial susceptibility testing could potentially improve response to treatment of Pseudomonas aeruginosa in people with cystic fibrosis. This is an update of a previously published Cochrane Review. To compare biofilm antimicrobial susceptibility testing-driven therapy to conventional antimicrobial susceptibility testing-driven therapy in the treatment of Pseudomonas aeruginosa infection in people with cystic fibrosis. We searched the Cochrane Cystic Fibrosis Trials Register, compiled from electronic database searches and handsearching of journals and conference abstract books. We also searched a registry of ongoing trials and the reference lists of relevant articles and reviews.Most recent search: 19 November 2014. Randomized controlled trials of antibiotic therapy based on biofilm antimicrobial susceptibility testing compared to antibiotic therapy based on conventional antimicrobial susceptibility testing in the treatment of Pseudomonas aeruginosa pulmonary infection in people with cystic fibrosis. Both authors independently selected trials, assessed their risk of bias and extracted data from eligible trials. Additionally, the review authors contacted the trial investigators to obtain further information. The searches identified two multicentre, randomized, double-blind controlled clinical trials eligible for inclusion in the review with a total of 78 participants; one trial was done in people who were clinically stable, the other in people experiencing pulmonary exacerbations. These trials prospectively assessed whether the use of biofilm antimicrobial susceptibility testing improved microbiological and clinical outcomes in participants with cystic fibrosis who were infected with Pseudomonas aeruginosa. The primary outcome was the change in sputum Pseudomonas aeruginosa density from the beginning to the end of antibiotic therapy.Although the intervention was shown to be safe, the data from these two trials did not provide evidence that biofilm susceptibility testing was superior to conventional susceptibility testing either in terms of microbiological or lung function outcomes. One of the trials also measured risk and time to subsequent exacerbation as well as quality of life measures and did not demonstrate any difference between groups in these outcomes. Both trials had an overall low risk of bias. The current evidence is insufficient to recommend choosing antibiotics based on biofilm antimicrobial susceptibility testing rather than conventional antimicrobial susceptibility testing in the treatment of Pseudomonas aeruginosa pulmonary infections in people with cystic fibrosis. Biofilm antimicrobial susceptibility testing may be more appropriate in the development of newer, more effective formulations of drugs which can then be tested in clinical trials.

Direct disk diffusion test using European Clinical Antimicrobial Susceptibility Testing breakpoints provides reliable results compared with the standard method.

Sepsis represents a life-threatening infection requiring the immediate start of antibacterial treatment to reduce morbidity. Thus, laboratories use direct antimicrobial susceptibility testing (AST) to rapidly generate preliminary results from positive blood cultures. As the direct AST has not yet been published to be evaluated with EUCAST breakpoints, the purpose of the study was to investigate the reliability of the direct agar diffusion test to correctly produce AST results from positive monobacterial blood cultures compared with the VITEK2-based definitive AST, when current EUCAST breakpoints were used. A total of 428 isolates from unselected monobacterial routine blood cultures and 110 challenge strains were included. Direct agar diffusion-based and standard VITEK2-based AST of 2803 bacterium-drug combinations yielded a total clinical category agreement of 95.47% with 1.28% very major errors and 3.42% combined major and minor errors. On the species level, very major errors were observed in the species-drug combinations Enterococcus spp.-high-level gentamicin (10.87%) and Staphylococcus spp.-rifampicin (5%), only. No very major errors occurred with Enterobacteriaceae and Pseudomonas aeruginosa. In most species-drug combinations, the direct agar diffusion test using EUCAST breakpoints precisely predicted the result of the definitive antibiotic susceptibility test and, thus, it can be used to optimize empiric antibiotic therapy until definitive results are available.

Comparative whole genome sequencing of community-associated methicillin-resistant Staphylococcus aureus sequence type 8 from primary care clinics in a Texas community.

Our understanding of the molecular dynamics driving the community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) epidemic at the whole genome level is limited. We sought to assess the use of whole genome sequencing (WGS) to evaluate the genomic diversity and genotypic prediction of antimicrobial resistance of CA-MRSA isolates from patients in South Texas. Comparative whole genome sequencing. Thirteen clinical CA-MRSA isolates recovered from patients presenting with skin and soft tissue infections to nine primary care clinics in the South Texas Ambulatory Research Network between 2010 and 2013. Comparative WGS was performed on the 13 MRSA sequence type 8 clinical isolates. We compared the resistome of genes encoding for antibiotic resistance with a phenotypically derived antibiogram using standard antimicrobial susceptibility testing. The strains differed by an average of 72 single nucleotide polymorphisms (SNPs) per isolate in the core genome compared with FPR3757 (USA300, reference strain). There were a total of 623 unique SNPs in the core genome (range 47-88 SNPs per isolate). We identified 19 nonsynonymous SNPs in genes encoding proven or putative S.aureus virulence determinants in the core genome. There was complete concordance between genotypic evidence for antimicrobial resistance and the phenotypically derived antibiogram. Overall, although these CA-MRSA isolates were similar on the level of clonal type, clinical syndrome, and geographic area, the strains were diverse at the genome level. Furthermore, our findings provide important proof-of-concept information for using WGS as a potential front-end screening tool for antimicrobial resistance predictions.

Concomitant Detection of Biofilm Formation and MBL Production in Meropenem Resistant Isolates of Pseudomonas aeruginosa

The purpose of this study was to detect biofilm formation and to examine the correlation between biofilm and Metallo-β-lactamases (MBL) production in Pseudomonas aeruginosa. A total of 64 P. aeruginosa isolates were identified using standard microbiological methods and antimicrobial susceptibility testing (AST) was performed on them according to Clinical and Laboratory Standards Institute (CLSI) guidelines. The isolates were screened for biofilm production using both qualitative and quantitative methods. The presence of MBL genes were checked by multiplex PCR assay. Out of all 30 meropenem resistant P. aeruginosa , 2 isolates were found producing all the three genes (i.e. bla IMP , bla VIM , bla SIM ) for MBL production and they were found to produce biofilm. Resistant to four antibiotics such as aztreonam (85.7% vs 11.1%, P< 0.000), Cefepime (82.1% vs 2.8%, P<0.000) gentamycin (82.1% vs 27.8%, P< 0.000) and Pipercillin/Tazobactum was also high

Knowledge and practices of laboratory workers on standardized antimicrobial susceptibility testing and biosafety practices to prevent the spread of superbugs in Pakistan

A cross-sectional survey using structured questionnaire was conducted to assess practices of microbiological laboratories working with pathogens. Forty-eight laboratory workers (50%) agreed that laboratory methods to detect antimicrobial resistance are not standardized in Pakistan, and 6% of the laboratory workers were not aware of the standardization of antimicrobial susceptibility testing in Pakistan. Reported rates of awareness regarding the role of waste disposal, disinfection, and handwashing in limiting the spread of antimicrobial resistance were 75%, 42%, and 81%, respectively. Our results provide baseline data for planning programs to train, supervise, and improve the operational quality of microbiological laboratories nationwide to prevent the spread of superbugs.

A 6-year retrospective study of bloodstream Salmonella infection and antibiotic susceptibility of Salmonella enterica serovar Typhi and Paratyphi in a tertiary care hospital in Dhaka, Bangladesh

ObjectivesBloodstream infections (BSI) are a serious cause of morbidity and mortality worldwide. Emerging antimicrobial drug resistance among bacterial pathogens causing BSI can limit therapeutic options and complicate patient management. This retrospective study was conducted to determine trends in Salmonella BSI and antibiotic susceptibility patterns over 6 years (2008–2013) in a tertiary care hospital in Dhaka, Bangladesh. MethodsA total of 3584 blood samples were collected from patients with clinically diagnosed enteric fever at Dhaka Medical College Hospital, Dhaka from January 2008 to December 2013. Isolates of Salmonella enterica serovars Typhi and Paratyphi were identified by standard microbiological and biochemical procedures. ResultsA total of 168 isolates of S. enterica serovar Typhi and 160 isolates of S. enterica serovar Paratyphi were found. The average prevalence rate of Salmonella in the blood was 9.15%. Young patients, neonates, and elderly individuals were more prone to Salmonella infection than other patients, and females were more susceptible to Salmonella septicemia than males. Among Salmonella spp. isolates, 20.92% were multidrug resistant and showed high resistance against amoxicillin, trimethoprim–sulfamethoxazole, ciprofloxacin, nalidixic acid, and chloramphenicol. Resistance rates to cefipime, cefixime, and ceftriaxone are increasing slowly. Among Salmonella spp. isolates, 57.01% showed extended-spectrum β-lactamase production capability. ConclusionSpecific antibiotic utilization strategies such as antibiotic restriction, combination therapy and usage according to standard antimicrobial susceptibility testing may help decrease or prevent the emergence of resistance and incidence of BSI.

Corneal ulcer: A prospective clinical and microbiological study

Background: It is important to study the epidemiologic features and predisposing factors of corneal ulcer and subsequently to find out its causative agents and their antimicrobial susceptibility patterns in a given community, climate and culture. Aims & Objectives: This prospective study of 100 cases of corneal ulcer was undertaken to bring out the bacterial and fungal prevalence among different age groups. Materials and Methods: Corneal scrapings were collected from all patients. One corneal swab and three corneal scrapings were collected. Direct examination of samples was done by potassium hydroxide wet mount and gram stained smear and then inoculated onto blood agar, MacConkey’s agar and Saboraud's dextrose agar media. Identification of fungal growth finally was done based on its macroscopic and microscopic features. Bacterial colonies were identified by Gram staining and standard biochemical tests and antimicrobial susceptibility testing was carried out for each bacterial isolate. Results: Out of total 100 specimens of corneal ulcer, only 55% cases were found to be culture positive in which bacteria were more frequently isolated than fungi. Staphylococcus aureus and Aspergillus spp were the most frequent bacterium and fungus. The incidence was higher in males and in age group of >40-60 years. While S. aureus was found to be most sensitive to vancomycin, Staphylococcus epidermis was most sensitive to cefazoline. Conclusion: S. aureus and Aspergillus spp were the most common isolate to be associated with corneal ulcer, and the incidence was higher in rural population, especially farmers, who were constantly exposed to vegetative matter.

Co-production of ESBL and AmpC β-Lactamases in Clinical Isolates of A. baumannii and A. lwoffii in a Tertiary Care Hospital From Northern India.

Acinetobacter baumannii is an important cause of health care associated infections which are difficult to control and treat, because of widespread antimicrobial resistance which is possessed by this organism. The aim of the present study was to know the prevalence of ESBLs and AmpC β-lactamases in clinical isolates of Acinetobacter spp. which were cultured from various clinical specimens by using different phenotypic methods. Study was conducted over a period of one year at the Microbiology Department of a tertiary care teaching hospital. A total of 100 consecutive, non-duplicate strains of Acinetobacter species which were isolated from various clinical samples were included. All the isolates were identified by standard microbiological procedures and antimicrobial susceptibility testing was done by Kirby-Bauer disc diffusion technique. Isolates which showed reduced susceptibilities to third generation cephalosporins were tested for ESBL production by CLSI double disc synergy method and also by using sulbactam as an inhibitory agent. Isolates which showed reduced susceptibilities to cefoxitin were tested for AmpC detection by doing AmpC disc test. SPSS, version 17 was used to calculate p-value. If the p-value was <0.05, it was considered to be significant. Out of 100 isolates, 82 were Acinetobacter baumannii and 18 were Acinetobacter lwoffii. ESBL were mentioned in 4% of the Acinetobacter isolates and in 77% of the isolates by using clavulanic acid and sulbactam as inhibitory agents respectively. AmpC β-lactamase production was detected in 60% isolates of Acinetobacter spp. Co-production of both ESBL and AmpC enzymes were seen in 29% of the Acinetobacter strains. Failure in detecting β-lactamases contributes to their uncontrolled spread and therapeutic failures. Hence, these β-lactamases should be detected routinely and they should be reported to clinicians in time, so that inappropriate use of antibiotics can be stopped in time.

Evaluation and use of a rapid Staphylococcus aureus assay by an antimicrobial stewardship program

The performance of a rapid test for methicillin-resistant Staphylococcus aureus (MRSA) in a large community hospital was investigated. A prospective observational study was conducted to evaluate an immunochromatographic assay (Alere PBP2a Culture Colony Test, Alere Scarborough, Inc.) for rapid differentiation of MRSA and methicillin-susceptible S. aureus (MSSA) strains using isolates cultured overnight on common laboratory media. S. aureus isolates cultured for 12-24 hours were tested with the assay, which detects penicillin-binding protein 2a (PBP2a) and provides results in six minutes. The test results were compared with data from standard overnight antimicrobial susceptibility testing to determine the assay's sensitivity and specificity. Changes in therapy associated with use of the rapid assay were evaluated. Over an 11-month period, 661 inpatient isolates from mostly nonhematologic sites were tested. There were six false-negative results, indicating assay sensitivity of 98.4%, with no false positives (specificity of 100%). Eight invalid test results were documented. During designated evaluation periods, a total of 169 patient cases involving PBP2a testing were reviewed by the hospital's antimicrobial stewardship pharmacist. In 63 of those cases (37%), changes in therapy were implemented on the day of test result posting. Interventions often involved switching patients from inappropriate to appropriate MRSA therapy or optimizing MRSA- or MSSA-targeted therapy. An assay for quickly differentiating between MRSA and MSSA was highly sensitive, highly specific, and inexpensive in actual hospital use and led to rapid prescription of appropriate antistaphylococcal therapy 24-48 hours after culture specimens were collected.

English

INTRODUCTION: Infection is a major cause of morbidity and mortality in burn patients, in spite of considerable advances in burn wound care and medical treatment. Burn wound infections are largely nosocomial in origin, incidence and isolation differ from hospital to hospital, study of isolates and their antibiogram is necessary to provide adequate and effective treatment that will reduce morbidity and mortality of patients. OBJECTIVE: The present study was undertaken to know the aerobic bacteriological profile of burn wound infection and their antimicrobial susceptibility pattern. MATERIAL AND METHOD: A total of 209 specimens were received from burn patients between January to July 2012. Wound swabs were taken with aseptic precautions by disposable sterile swabs. These swabs were transported to central laboratory where they were cultured on blood agar and MacConkey agar and incubated aerobically overnight at 37 0 C. Isolates were identified based on standard microbiological methods and antimicrobial susceptibility testing was done by Kirby Bauer's disc diffusion method. RESULT: A total of 147 bacterial pathogens were isolated from 209 samples. The most frequent cause of infection was found to be Pseudomonas aeruginosa (48.3%), followed by Staphylococcus aureus (19.29%), Escherichia coli (13.26%), Klebsiella spp. (8.44%), Proteus spp. (3.7%), Enterococcus spp.(6 %) & Citrobacter spp. (1%). High level of drug resistance was observed for Cefotaxime, Ceftazidime and Cotrimoxazole among gram negative pathogens. Imipenem, Piperacillin/Tazobactam, Amikacin and Ciprofloxacin were found to be most effective. Twenty two percent of the Staphylococcus aureus isolates were methicillin resistant but none was resistant to Vancomycin & Linezolid. CONCLUSION: Pseudomonas aeruginosa is a major cause of infection in burn wounds which showed high level resistance to antimicrobials. The high prevalence of antimicrobial resistance emphasizes the need for strengthening the infection control practices and regular and periodical surveillance activities to contain the upward trend of resistance. Isolation pattern and antibiogram

Antibacterial and Antioxidant Activities of Various Medicinal Plants Used in Oriental Medicine

The antibacterial activities of the ethanol extracts of 35 medicinal plants were screened against Escherichia coli, Bacillus cereus, and Staphylococcus aureus by following standard antimicrobial susceptibility testing procedures. The ethanol extracts of Coptis chinensis and Glycyrrhiza uralensis showed antibacterial activity against all three test bacterial species. The screened extracts were also tested for their antioxidant activities using the DPPH free radical scavenging activity assay, and for their cytotoxic and antioxidant activity in vitro using an assessment of cell viability on mouse embryonic fibroblast cells. The ethanol extracts of both C. chinensis and G. uralensis showed good radical scavenging antioxidant properties and attenuated the rate of cell death caused by oxidative damage. Our results showed that C. chinensis and G. uralensis are promising sources of natural products with good antibacterial and antioxidant activities.

Letter: curing Helicobacter pylori infection in a clinical setting – authors' reply

We thank Dr Tursi for his recent comments concerning our recent publication.1, 2 Bacterial culture and standard antibiotic susceptibility testing is recommended for patients who have failed first-line triple therapy.3 Such standard susceptibility testing is not widely available in many countries. As a result, the success of a treatment plan without standard susceptibility testing is of pertinent interest. We are currently undertaking a retrospective analysis on the salvage therapies, PARC and PBRC (Table 1), which were prescribed to patients without performing the standard susceptibility testing. A total of 98 patients initially failed at least one course (usually two) of standard 7-day triple therapy and were subsequently treated in this study. Preliminary analysis suggests that the PARC regimen successfully eradicated H. pylori in 90.5% of patients (n = 63, 95% CI: 85–98) (Table 2). For patients allergic to amoxicillin, the PBRC regimen eradication rate was 100% (n = 25, 95% CI: 88–100). Patients requiring alternative salvage therapies were given novel personalised combinations consisting of bismuth, rifabutin and either tetracycline or furazolidone; the eradication rate for this small group was 90% (n = 10, 95% CI: 57–99). Although the sample size is small, this encouraging analysis indicates that the PARC and PBRC salvage therapies can be confidently prescribed without the expense of standard antimicrobial susceptibility testing. The efficacies of alternative antibiotic combinations with small sample sizes are continuously being monitored in our clinic. It is important to note that antibiotic resistant profiles vary from country to country. As a result, the proposed salvage therapies in our previous publication2, PARC and PBRC, are suitable only for countries with low rates of resistance to quinolone and rifabutin. The authors' declarations of personal and financial interests are unchanged from those in the original article.2

Clinicians' knowledge, attitudes, and practices regarding infections with multidrug-resistant gram-negative bacilli in intensive care units.

To assess how healthcare professionals caring for patients in intensive care units (ICUs) understand and use antimicrobial susceptibility testing (AST) for multidrug-resistant gram-negative bacilli (MDR-GNB). A knowledge, attitude, and practice survey assessed ICU clinicians' knowledge of antimicrobial resistance, confidence interpreting AST results, and beliefs regarding the impact of AST on patient outcomes. Sixteen ICUs affiliated with NewYork-Presbyterian Hospital. Attending physicians and subspecialty residents with primary clinical responsibilities in adult or pediatric ICUs as well as infectious diseases subspecialists and clinical pharmacists. Participants completed an anonymous electronic survey. Responses included 4-level Likert scales dichotomized for analysis. Multivariate analyses were performed using generalized estimating equation logistic regression to account for correlation of respondents from the same ICU. The response rate was 51% (178 of 349 eligible participants); of the respondents, 120 (67%) were ICU physicians. Those caring for adult patients were more knowledgeable about antimicrobial activity and were more familiar with MDR-GNB infections. Only 33% and 12% of ICU physicians were familiar with standardized and specialized AST methods, respectively, but more than 95% believed that AST improved patient outcomes. After adjustment for demographic and healthcare provider characteristics, those familiar with treatment of MDR-GNB bloodstream infections, those aware of resistance mechanisms, and those aware of AST methods were more confident that they could interpret AST results and/or request additional in vitro testing. Our study uncovered knowledge gaps and educational needs that could serve as the foundation for future interventions. Familiarity with MDR-GNB increased overall knowledge, and familiarity with AST increased confidence interpreting the results.