Antimicrobial Susceptibility Testing Results Research Articles

Antimicrobial susceptibility patterns of bacterial isolates cultured from synovial fluid samples from horses with suspected septic synovitis: 108 cases (2008–2017)

To describe the antimicrobial susceptibility patterns of the most commonly isolated bacteria cultured from synovial fluid samples from horses with suspected septic synovitis treated at an equine referral hospital between May 1, 2008, and September 24, 2017. 131 synovial fluid samples from 108 client-owned horses. A retrospective medical record search was conducted to identify horses with suspected septic synovitis and results of synovial fluid bacterial culture and antimicrobial susceptibility testing. Data collected included signalment, known or suspected origin of synovial contamination, synovial structures affected, antimicrobial treatment, and results of synovial fluid cytologic evaluation and bacterial culture and susceptibility testing. Horses were grouped as adults (≥ 6 months old) or foals (< 6 months old). Results of bacterial culture were positive for 34 of 70 (49%) and 18 of 61 (30%) samples from 68 adult horses and 40 foals, respectively. Gram-positive bacteria were more common in adult horses, whereas gram-negative bacteria were more common in foals. No multidrug-resistant microorganisms were identified. For adult horses, 92% (23/25) of gram-positive isolates tested with penicillin and gentamicin were susceptible to the combination. For foals, 94% (15/16) of isolates tested with penicillin, gentamicin, or both had susceptibility to 1 or both antimicrobials. Periodic review of bacterial profiles and antimicrobial susceptibility in horses with septic synovitis can help to detect early changes in bacterial pressure and antimicrobial resistance. Findings suggested that in the geographic area we serve, a combination of penicillin and gentamicin would be an effective empirical antimicrobial treatment for most horses with septic synovitis while results of bacterial culture and susceptibility are pending.

Susceptibility-guided bismuth quadruple therapies for resistant Helicobacter pylori infections.

Increasing Helicobacter pylori resistance to antibiotics has ledthat molecular testing is appropriate as a sub to adoption of seven different bismuth quadruple therapies (BQT) in China without differentiation of first-line or second-line regimens. The objective of this study was to evaluate the efficacy of susceptibility-guided BQT for patients who had experienced previous treatment failures. A total of 133 patients was included and H. pylori was successfully cultured from 101 patients (75.9%) for subsequent antimicrobial susceptibility testing (AST). Based on the AST results, 88 patients completed one of five AST-guided 14-day BQT regimens: esomeprazole and bismuth colloidal pectin, along with either, amoxicillin and clarithromycin (EBAC), amoxicillin and levofloxacin (EBAL), amoxicillin and furazolidone (EBAF), amoxicillin and tetracycline (EBAT), or tetracycline and furazolidone (EBTF). H. pylori eradication rates were 100% for EBAC (5/5), EBAL (13/13), EBAF (14/14), and EBTF (43/43), but 76.9% for EBAT (10/13). The three patients that failed the EBAT regimen were all cured after subsequent treatment with the EBTF regimen. Our study demonstrates the excellent efficacy of the AST-guided BQT for referred H. pylori patients, and that the current EBAT regimen, used in clinics, needs to be optimized. In addition, 57 of the isolates were subjected to whole-genome sequencing. Analysis of the sequences revealed that point mutations in 23S rRNA correlated well with the phenotypic clarithromycin resistance with a concordance of 91.2%, while the concordance between phenotypic levofloxacin resistance and gyrA point mutations was 82.3%. This suggests that molecular testing is appropriate as a substitute for AST as a more rapid and cost-effective method for determining clarithromycin and levofloxacin resistance in Chinese patients.

ANTIMICROBIAL RESISTANCE OF COMMON UROPATHOGENS FROM CATS WITH URINARY TRACT INFECTIONS IN A VETERINARY TEACHING HOSPITAL IN TAIWAN

Urinary tract infection (UTI) is frequently diagnosed in dogs and cats. To realize common regional uropathogens and their antimicrobial resistance plays an important role in both human and veterinary medicine. An empirical antibiotic was administrated while waiting for the results of bacterial culture and antimicrobial susceptibility testing. Eighty-five bacterial isolates were obtained from 74 cats with clinical signs of UTI. Escherichia coli, Enterococcus species, Staphylococcus species and Klebsiella species were the most common bacterial isolates in our hospital. Compared to the previous researches, the susceptibilities of recommended empirical antibiotics exhibited higher resistant rate in our study. Lincomycin was the most resistant antibiotic within the test panel to that almost 98% uropathogens were resistant. The resistant rates of cephalexin, cephalothin, penicillin and amoxicillin were about 90%. Therefore, the selection of empirical antibiotics should be re-evaluated with time in Taiwan.

Differences in isolation rate and antimicrobial susceptibility of bacteria isolated from foals with sepsis at admission and after ≥48 hours of hospitalization.

BackgroundAntimicrobial treatment protocols for foals with sepsis that do not improve clinically often are adjusted based on bacteriological and antimicrobial susceptibility testing results from samples collected at hospital admission.ObjectivesTo evaluate whether hospitalization for ≥48 hours affects bacteriological and antimicrobial susceptibility testing results.AnimalsTwo‐hundred sixty‐seven foals <30 days of age admitted to a neonatal intensive care unit and diagnosed with sepsis.MethodsMedical records were reviewed retrospectively to identify foals with sepsis and positive bacteriological cultures. Results from samples collected at hospital admission were compared to those collected ≥48 hours after admission. Logistic regression for clustered data and exact logistic regression were used for statistical analysis.ResultsThree‐hundred fifty‐three unique bacterial isolates were obtained from 231 foals at hospital admission and 92 unique bacterial isolates were obtained from 57 foals after ≥48 hours of hospitalization. Relative isolation frequency after ≥48 hours of hospitalization increased for Acinetobacter spp., 0.6% versus 3.3% (odds ratio [OR], 7.63; 95% confidence interval [CI], 1.28‐45.45); Enterococcus spp., 4.8% versus 19.6% (OR, 5.37; 95% CI, 2.64‐10.90); Klebsiella spp., 5.1% versus 10.9% (OR, 2.27; 95% CI, 1.05‐4.89); Pseudomonas spp., 3.0% versus 7.6% (OR, 3.49; 95% CI, 3.49‐240.50); and Serratia spp., 3.0% versus 5.4% (OR, 20.23; 95% CI, 2.20‐186.14). Bacteria isolated after ≥48 hours of hospitalization were less susceptible to all tested antimicrobial drugs, except for imipenem.Conclusions and Clinical ImportanceDecreased antimicrobial susceptibility of bacteria isolated after ≥48 hours of hospitalization provides a rationale for repeated bacteriological culture and susceptibility testing in hospitalized foals with sepsis.

Rapid Determination of Antimicrobial Susceptibility of Gram-Negative Bacteria from Positive Blood Cultures Using an Innovative Method

Introduction: A blood stream infection (BSI) presents a complex and serious health problem and is growing in light of the eminent antimicrobial resistance threat. Progress must be made towards rapid BSI diagnosis and antimicrobial susceptibility testing (AST) to reduce preventable death in BSI. Methods: Positive blood cultures from Ninewells Hospital, Dundee were studied prospectively. Flagged positive blood cultures were processed by Gram-staining, Vitek identification and AST or disc diffusion for ceftriaxone susceptibility and by scattered light integrated collection device (SLIC). Susceptibility to a panel of five antibiotics as defined by EUCAST breakpointswere compared.The time to AST result and AST categorical agreement was compared for standard methods and SLIC, any discrepancies were resolved by the EUCAST broth micro-dilution reference method. Results: A total of 505 bacterial-antimicrobial combinations were analysed. A categorical agreement of 95.45% (482/505) was achieved between SLIC and Vitek/disk diffusion. The remaining 23 discrepancies were resolved by broth micro-dilution with 10 AST results agreeing with the SLIC result and 13 in agreement of Vitek/disk diffusion. Thus the overall AST agreement of the standard workflow was 98.01% (495/505) compared to 97.43% (492/505) using SLIC. The mean time for AST was 1.94 + 0.02 h and 10.53 + 0.46 h for SLIC and Vitek respectively. Overall SLIC was calculated to save 25hrs from positive blood culture to AST outcome. Conclusion: SLIC has the capacity to provide AST at the same time as Gram stain or MALDI-TOF identification.This could improve the value of blood culture in clinical practice.

Discordant bioinformatic predictions of antimicrobial resistance from whole-genome sequencing data of bacterial isolates: an inter-laboratory study.

Antimicrobial resistance (AMR) poses a threat to public health. Clinical microbiology laboratories typically rely on culturing bacteria for antimicrobial-susceptibility testing (AST). As the implementation costs and technical barriers fall, whole-genome sequencing (WGS) has emerged as a ‘one-stop’ test for epidemiological and predictive AST results. Few published comparisons exist for the myriad analytical pipelines used for predicting AMR. To address this, we performed an inter-laboratory study providing sets of participating researchers with identical short-read WGS data from clinical isolates, allowing us to assess the reproducibility of the bioinformatic prediction of AMR between participants, and identify problem cases and factors that lead to discordant results. We produced ten WGS datasets of varying quality from cultured carbapenem-resistant organisms obtained from clinical samples sequenced on either an Illumina NextSeq or HiSeq instrument. Nine participating teams (‘participants’) were provided these sequence data without any other contextual information. Each participant used their choice of pipeline to determine the species, the presence of resistance-associated genes, and to predict susceptibility or resistance to amikacin, gentamicin, ciprofloxacin and cefotaxime. We found participants predicted different numbers of AMR-associated genes and different gene variants from the same clinical samples. The quality of the sequence data, choice of bioinformatic pipeline and interpretation of the results all contributed to discordance between participants. Although much of the inaccurate gene variant annotation did not affect genotypic resistance predictions, we observed low specificity when compared to phenotypic AST results, but this improved in samples with higher read depths. Had the results been used to predict AST and guide treatment, a different antibiotic would have been recommended for each isolate by at least one participant. These challenges, at the final analytical stage of using WGS to predict AMR, suggest the need for refinements when using this technology in clinical settings. Comprehensive public resistance sequence databases, full recommendations on sequence data quality and standardization in the comparisons between genotype and resistance phenotypes will all play a fundamental role in the successful implementation of AST prediction using WGS in clinical microbiology laboratories.

Poor Antimicrobial Activity of Opium Against Carbapenem-Resistant Pseudomonas aeruginosa Isolates

Background: Carbapenem-resistant Pseudomonas aeruginosa (P. aeruginosa) has dramatically increased. Thus, finding a new therapeutic option is necessary to fight such isolates. Objectives: This study aimed to explore the influence of opium on carbapenem-resistant and carbapenem-sensitive P. aeruginosa. Methods: During the study period from December 2018 to March 2019, a total of 20 non-duplicate P. aeruginosa isolates were collected from clinical samples in Shahid Mohammadi and Pediatrics hospitals (teaching hospitals) affiliated to Hormozgan University of Medical Sciences in Bandar Abbas, the South of Iran. The antimicrobial susceptibility pattern was tested by the disc diffusion method according to the Clinical and Laboratory Standards Institute (CLSI) guidelines. The influence of opium was tested by broth microdilution and agar disc diffusion methods against P. aeruginosa isolates. Results: We studied 20 isolates of P. aeruginosa, of which 30%, 30%, 15%, 10%, 10%, and 5% were collected from wound, urine, discharge, blood, tracheal tube, and other specimens, respectively. According to the antimicrobial susceptibility testing results, the highest and lowest rates of resistance were to ofloxacin and piperacillin, respectively. Unexpectedly, all clinical and standard isolates of P. aeruginosa were resistant to different concentrations of opium. Conclusions: Based on our experiments, no antimicrobial effect was found for opium against the tested isolates. Studies of opium need to be continued as it may show some bacteriostatic or bactericide activities in other conditions.

Trends of Intra-Cranial Bacterial Infection in Patients Requiring Emergency Neurosurgery.

Background: Intra-cranial bacterial infection is a serious complication in emergency neurosurgical patients, and few data are available on the trends of these infections and the rates of antibacterial drug resistance. Methods: We surveyed retrospectively the patients with intra-cranial bacterial infection in our emergency neurosurgical center between January 2009 and December 2018. Demographic characteristics, causative bacteria, and antimicrobial susceptibility test results were collected. Results: A total of 100 patients with intra-cranial bacterial infection, 1.41% of our patients, were enrolled. There were 123 strains of bacteria cultured from the cerebrospinal fluid (CSF), consisting of 96 strains of gram-negative (GN) bacteria and 27 strains of gram-positive (GP) bacteria. Compared with the GP bacteria, the percentage of GN bacteria increased to 75.0% of the total near the end of the study. Compared with Acinetobacter baumannii, Klebsiella pneumoniae also showed an uptrend. Most of the bacteria were multi-drug-resistant (MDR). We further analyzed the consistency of CSF and sputum cultures from the same patient. The ratio of Klebsiella pneumoniae and Acinetobacter baumannii to the corresponding strains in the CSF were 77.0% and 62.0%. Conclusions: The bacteria recovered from the CSF were mainly GN. The tendency of GN bacteria showed an uptrend, especially for Klebsiella pneumoniae. Furthermore, most of the bacteria were MDR.

Repetitive cellulitis caused by Streptococcus agalactiae isolates with different genotypic and phenotypic features in a patient having upper extremity with lymphedema after mastectomy and axillary lymph node dissection

Previously reported cases of recurrent cellulitis/erysipelas affecting chronically lymphedematous skin regions have been demonstrated to be due to Streptococcus agalactiae isolates with closely related genetic background which may be suggestive of relapse rather than reinfection. Herein, we report the occurrence of three episodes of repetitive cellulitis caused by S. agalactiae strains with different genotypic and phenotypic characteristics, including different antimicrobial susceptibility patterns (tetracycline, macrolide/lincosamide, and fluoroquinolone classes), in the left upper extremity of a patient with lymphedema, following left mastectomy and axillary lymph node dissection. The genotypic and phenotypic characteristics of the three isolates were confirmed based on the random amplified polymorphic DNA patterns, DNA profiles of virulence factors (bca-rib-bac-lmb-cylE), data on biofilm formation and cell invasion, antimicrobial susceptibility testing results, antimicrobial resistance (AMR) genotypes, and amino acid mutations associated with AMR. These results revealed that reinfection with S. agalactiae, rather than recurrence, occurred during the three episodes. In conclusion, microbiologic studies such as blood cultures or tissue cultures are certainly helpful in the management of recurrent infections or invasive infections such as bacteremia in order to better target antimicrobial therapy, regardless of the data previously presented.

Carbapenem-resistant Enterobacteriaceae (CRE) and gram-negative bacterial infections in south-west Nigeria: a retrospective epidemiological surveillance study.

BackgroundCarbapenem-resistant Enterobacteriaceae (CRE) are often responsible for severe, life-threatening infections and they represent a critical threat to the available antibiotic agents and to global health. An understanding of the epidemiology of these infections will be indispensable to the development of appropriate case management as well as infection prevention and control (IPC) measures in any healthcare setting.ObjectivesThe objective of this study was to investigate and describe the epidemiology of carbapenem-resistant Enterobacteriaceae (CRE) and other gram-negative bacteria in a tertiary hospital in south west Nigeria using routinely collected microbiological laboratory data.MethodsA retrospective collection of microbiological laboratory records from the January to June 2018 was performed. All culture and antimicrobial susceptibility test results of patients who required laboratory tests were collected. Other information collected include: patient demographics, clinical specimen types and the requesting hospital department. The data was analyzed using SPSS Windows version 24. Comparison between categorical variables was done using chi-square tests while independent sample t-test was used to determine significant mean differences between groups. A p < 0.05 was taken to be statistically significant.ResultsThe prevalence of carbapenem-resistance among Enterobacteriaceae and gram-negative bacteria isolates was 22% (n = 39/177). Of these, 35.9% (n = 14) were Klebsiella pneumonia, 30.8% (n = 12) were Pseudomonas aeruginosa and 15.4% (n = 6) were Klebsiella oxytoca. 87.2% (n = 34) of these were also multi-drug resistant, with a mean total resistance score of 3.92 (SD = ± 1.44). There were differences observed in proportion of carbapenem-resistance across clinical specialties and age groups; however, these differences were not statistically significant. Independent sample t-test revealed that carbapenem-resistant isolates exhibited more drug resistance than carbapenem-sensitive isolates (3.93 vs. 2.30; p < 0.001).ConclusionCarbapenem resistance is an important threat to the current antibiotic armory. Active surveillance, particularly in the healthcare setting is required to identify high risk groups, inform better treatment options and infection prevention and control measures.

Occurrence and antibiogram of Listeria monocytogenes Isolates from Retail Meat Shops at Erbil City, Kurdistan Region, Iraq.

Listeria monocytogenes is well-known globally as one of the most significant foodborne bacterial pathogens. Listeriosis may trigger life-threatening illness, such as severe sepsis, meningitis, sometimes resulting in lifelong harm and even death. This study aimed to determine the occurrence and antibiotic resistance pattern of L. monocytogenes in red meats sold at retail outlets in Erbil city, Kurdistan region, Iraq. Three hundred and seventy-five (375) samples were aseptically collected from retail meat shops between July and December 2018. For isolation of L. monocytogenes, samples were cultured on selective media and tested for their susceptibility to common antibiotics by disk diffusion assay. The results revealed that the overall occurrence of L. monocytogenes in red meat samples was 13.9%. Warm season was associated with increase in L. monocytogenes occurrence. The results of antimicrobial susceptibility testing showed that 98.1%, 94.2%, and 82.7% of isolates were resistant to Streptomycin, Gentamicin, and Ampicillin respectively. This resistance pattern of L. monocytogenes is critically alarming owing to the aforementioned antibiotics are the drugs of choice of treatment of listeriosis. This level of resistance requires further investigations and effective countermeasures since it may pose a public health hazard.

Evaluation of a new Rapid Antimicrobial Susceptibility system for Gram-negative and Gram-positive bloodstream infections: speed and accuracy of Alfred 60AST

BackgroundBlood stream infections (BSIs) are a major cause of morbidity and mortality. The time from taking blood cultures to obtain results of antibiotic sensitivity can be up to five days which impacts patient care. The Alfred 60 AST™ can reduce laboratory time from positive culture bottle to susceptibility results from 16 to 25 h to 5–6 h, transforming patient care. To evaluate the diagnostic accuracy of a rapid antimicrobial susceptibility system, the Alfred 60 AST™, in clinical isolates from patients with BSIs and confirm time to results. 301 Gram-negative and 86 Gram-positive isolates were analysed directly from positive blood culture bottles following Gram staining. Antimicrobial susceptibility results and time-to-results obtained by rapid Alfred 60 AST system and BD Phoenix were compared .ResultsA total of 2196 antimicrobial susceptibility test results (AST) were performed: 1863 Gram-negative and 333 Gram-positive. AST categorical agreement (CA) for Alfred 60 AST™ was 95% (1772/1863) for Gram-negative and 89% (295/333) for Gram-positive isolates. Gram-negative CA: ampicillin 96% (290/301); ciprofloxacin 95% (283/297); ceftriaxone 96% (75/78); meropenem 97% (288/297); piperacillin-tazobactam 95% (280/295); gentamicin 94% (279/297) and amikacin 93% (277/298). The median time to susceptibility results from blood culture flagging positive was 6.3 h vs 20 h (p < 0.01) for Alfred system vs BD Phoenix™.ConclusionAlfred 60 AST system greatly reduced time to antimicrobial susceptibility results in Gram-negative and Gram-positive BSIs with good performance and cost, particularly for Gram-negative bacteraemia.

Rapid microbial identification and phenotypic antimicrobial susceptibility testing directly from positive blood cultures: a new platform compared to routine laboratory methods

The Accelerate Pheno™ System (APS), a new platform that combines rapid identification (ID) of bacteria and yeasts and phenotypic antimicrobial susceptibility testing (AST) in a single assay, has been evaluated directly from positive blood cultures in comparison to routine laboratory methods. The APS ID results showed an overall sensitivity and specificity of 92.6% and 99.6%, respectively. With regard to AST results, 31 discrepancies (8 single errors and 23 combined errors) were observed, including 13 major errors (3.3%) and 18 minor errors (4.6%) mainly involving Pseudomonas aeruginosa. No very major error was observed. The APS ID results were obtained in 1.5 h and the AST results were available in 7 h, on average 34.1 h before routine laboratory methods. This reduction in AST time-to-result represents one of the main advantages of this technology, reducing the time to provide to the physician the microbiological report.

Rapid antimicrobial susceptibility testing on positive blood cultures through an innovative light scattering technology: performances and turnaround time evaluation

BackgroundA bacteremia diagnosis with speeded-up identification and antimicrobial susceptibility testing (AST) is mandatory to adjust empirical broad-spectrum antibiotherapy and avoid the emergence of multi-resistant bacteria. Alfred 60AST (Alifax, Polverara, PD, Italy) is an innovative automated system based on light scattering measurements allowing direct AST from positive blood cultures with rapid results. In this study we aimed to evaluate the system’s performances and turnaround time (TAT) compared to routine AST.MethodsThe study was conducted during 2 non-consecutive 3-month periods at the microbiology laboratory of the Cliniques universitaires Saint-Luc. All blood cultures detected positive in the 0 AM–10 AM time frame with a pure Gram-positive cocci or Gram-negative bacilli stain were included for Alfred 60AST testing. Two customized EUCAST antibiotic panels were set up composed of 1) a “Gram-negative” panel including cefuroxime, ceftazidime Enterobacteriaceae, piperacillin-tazobactam Enterobacteriaceae, ciprofloxacine, and ceftazidime Pseudomonas 2) a “Gram-positive” panel including cefoxitin Staphylococcus aureus, cefoxitin coagulase-negative (CNS) Staphylococci and ampicillin Enterococci. Categorical agreement (CA), very major errors (VME), major errors (ME), minor errors (mE) and TAT to Alfred 60AST results were calculated in comparison with AST results obtained from direct testing on positive blood cultures with the Phoenix system (Becton Dickinson, Franklin Lakes, NJ, USA).ResultsFive hundred seventy and one hundred nine antibiotics were evaluated on respectively 166 Gram-negative bacilli and 109 Gram-positive cocci included in the studied population. During the first study period regarding Gram-negative strains a CA of 89.5% was obtained with a high rate of VME (19 and 15.4% respectively) for cefuroxime and piperacillin-tazobactam Enterobacteriaceae. Considering this, Alifax reviewed these antibiotics’ formulations improving Gram-negative bacilli total CA to 92.2% with no VME during the second study period. For Gram-positive cocci, total CA was 88.1% with 2.3% VME, 13.8% ME (mainly cefoxitin CNS) and 12% mE rates both study periods combined. Median TAT to AST results was 5 h with Alfred versus 12 h34 with Phoenix.ConclusionThe Alfred 60AST system shows correct yet improvable microbiological performances and a major TAT reduction compared to direct automated AST testing. Clinical studies measuring the impact of the approach on antibiotic management of patients with bacteremia are recommended.

Susceptibility Pattern of Isolated Pathogenic Oral Bacteria to Some Commonly Prescribed Antibiotics in Dental and General Medical Practice

The current global rise in the morbidity and mortality rates of infectious diseases is due in part, to the problem of antimicrobial resistance. The global threat of antimicrobial resistance is also partly a consequence of widespread inappropriate prescription and use of antibiotics, sometimes on empirical basis, without any established antimicrobial susceptibility data-based guidelines on such empirical use. In the present study, we re-examined the susceptibility pattern of organisms isolated from active carious lesions to some commonly prescribed antibiotics and suggest a comprehensive data generation and establishment of guidelines based on a holistic assessment of susceptibility pattern of different organisms to the different classes of antibiotics commonly prescribed in various branches of medicine. For instance, our results revealed significant resistance of cariogenic organisms such as Streptococcus mutans and Lactobacillus to Amoxicillin, Gentamicin, Tarivid, Chloramphenicol and Sparfloxacin, with good susceptibility to Ciprofloxacin, Ofloxacin, Pefloxacin and Streptomycin. These findings suggest that the latter group of antibiotics could function better than Amoxicillin in the prophylactic and empirical management of dental caries and other oral infections prior to obtaining antimicrobial susceptibility test results. &#x0D; Keywords: Antimicrobial, Susceptibility, Empirical, Resistance.

Same-day antimicrobial susceptibility test using acoustic-enhanced flow cytometry visualized with supervised machine learning.

Purpose. Antimicrobial susceptibility is slow to determine, taking several days to fully impact treatment. This proof-of-concept study assessed the feasibility of using machine-learning techniques for analysis of data produced by the flow cytometer-assisted antimicrobial susceptibility test (FAST) method we developed.Methods. We used machine learning to assess the effect of antimicrobial agents on bacteria, comparing FAST results with broth microdilution (BMD) antimicrobial susceptibility tests (ASTs). We used Escherichia coli (1), Klebsiella pneumoniae (1) and Staphylococcus aureus (2) strains to develop the machine-learning algorithm, an expanded panel including these plus E. coli (2), K. pneumoniae (3), Proteus mirabilis (1), Pseudomonas aeruginosa (1), S. aureus (2) and Enterococcus faecalis (1), tested against FAST and BMD (Sensititre, Oxoid), then two representative isolates directly from blood cultures.Results. Our data machines defined an antibiotic-unexposed population (AUP) of bacteria, classified the FAST result by antimicrobial concentration range, and determined a concentration-dependent antimicrobial effect (CDE) to establish a predicted inhibitory concentration (PIC). Reference strains of E. coli, K. pneumoniae and S. aureus tested with different antimicrobial agents demonstrated concordance between BMD results and machine-learning analysis (CA, categoric agreement of 91 %; EA, essential agreement of 100 %). CA was achieved in 35 (83 %) and EA in 28 (67 %) by machine learning on first pass in a challenge panel of 27 Gram-negative and 15 Gram-positive ASTs. Same-day AST results were obtained from clinical E. coli (1) and S. aureus (1) isolates.Conclusions. The combination of machine learning with the FAST method generated same-day AST results and has the potential to aid early antimicrobial treatment decisions, stewardship and detection of resistance.

1608. Use of Selective Reporting of Antimicrobial Susceptibilities and Its Impact on Antimicrobial Resistance Surveillance—National Healthcare Safety Network, 2017–2018

BackgroundSelective reporting (SR), recommended by the 2016 IDSA/SHEA antimicrobial stewardship guidelines, is a strategy to guide prescribing decisions by limiting the antimicrobial susceptibility testing (AST) results available to prescribers. Yet, SR carries risks that cumulative antibiograms reflect only partial AST results. The Clinical Laboratory Standards Institute (CLSI) M100 performance standards stipulate that AST results should be routinely reported for some antimicrobials (Group A agents) while SR is appropriate for other antimicrobials (Group B agents). We assessed the extent of SR use and its impact on national antimicrobial resistance (AR) surveillance.MethodsWe used Enterobacteriaceae (EB) and Staphylococcus aureus (SA) blood culture AST results that hospitals reported for group A and B agents to the CDC’s National Healthcare Safety Network’s AR option from 2017 through 2018. Routine reporting for an organism-agent combination was defined as results reported for ≥ 90% isolates for the hospital’s most frequently reported agents. SR was defined as a shortfall of > 20% in results reported for an agent compared with a routinely reported agent in a hospital that reported ≥ 30 isolates. We compared hospital antibiograms between SR and non-SR hospitals. We also identified isolate characteristics associated with AST reporting in SR hospitals.ResultsAmong 242 and 185 hospitals reported ≥ 30 isolates, many showed patterns of SR (Figure 1). Of 437 and 425 hospitals reported ≥ 1 isolate, only 112 (26%) and 152 (36%) routinely reported AST results for all group A agents for EB and SA, respectively. For EB, 345 (79%) hospitals routinely reported AST results for ciprofloxacin or levofloxacin, although both are group B agents. For SA, 324 (76%) routinely reported vancomycin (Figure 2). Antibiograms for many agents differed between SR and non-SR hospitals (Figure 3, 4). In SR hospitals, non-susceptibility to narrower-spectrum drugs, patient location, age, and some species among EB were associated with AST reporting.ConclusionAST results reporting vary across hospitals and agents, and CLSI’s SR standards are used inconsistently. For AR surveillance, complete reporting calls for solutions that bypass SR. In the meantime, SR should be taken into account in national AR benchmarking. Disclosures All authors: No reported disclosures.

2441. Automated, Rapid Detection of Potential Healthcare-Acquired Infection Clusters Based on Microbiology And Patient Geotemporal Data

BackgroundWhole-genome sequencing (WGS) has shown promise in identifying transmissions of healthcare-associated infections (HAIs), but it may be costly to sequence all potential HAIs. By automatically identifying samples likely to be HAIs, WGS can be focused on specific samples. We describe an algorithm that quickly identifies potential HAI clusters by analyzing patient geotemporal and pathogen microbiology data. This approach systematically triages potential HAI investigations to aid infection control professionals (ICPs) in their workflow.MethodsThis novel algorithm within Philips IntelliSpace Epidemiology scores the potential of transmission for pairs of infections. Inputs include microbiology (MB) data (genus- or species-level identification and antimicrobial susceptibility test results) and geotemporal (GT) data (timing of sample collection and shared location stays). From the resulting pairwise scores, clusters of potential HAIs are identified. Leveraging 9 months (June, 2018 – March, 2019) of data from a 900-bed US hospital (i.e., 2825 samples, 1814 patients and 13 organisms—of which a subset of 404 samples had WGS performed concomitantly with MB studies), we evaluated the extent to which this algorithm captures genetically similar sample pairs.ResultsPairwise scores enrich for genetically similar samples when considering MB data only (odds ratio: 17.3), GT only (odds ratio: 6.1) and a combination of both (odds ratio: 19.8), with highly significant P-values for all (P < 10−16). Considering MB only, 91% of samples group together in potential transmission clusters. With MB and GT data, this fraction drops to 24.6% (694 samples) forming 178 possible clusters, 173 of which contain fewer than ten samples each. The 5 larger clusters contain 40–64 samples each and span multiple units in the hospital.ConclusionThe proposed system automatically suggests potential HAI clusters. By combining MB and GT data, the number of samples to review is reduced, enabling ICPs to focus their attention and sequencing efforts. By focusing on a targeted group of higher probability clusters, ICPs may be able to increase their efficiency and effectiveness in controlling the spread of HAIs—thus boosting potential for patient safety and amelioration of cost of care.Disclosures All authors: No reported disclosures.

1593. Analysis of Hospital Antimicrobial Susceptibility Test Results for Patterns of Antibiotic Resistance

BackgroundAntimicrobial susceptibility tests (ASTs) are routinely performed on pathogens isolated from clinical samples. ASTs are used by clinicians to select the most appropriate treatment for antibiotic-resistant microorganisms. In aggregate, ASTs offer insight into the rise and spread of antibiotic resistance across hospitals. Here, we used ASTs to identify patterns of antibiotic resistance across drugs and microorganisms.MethodsWe conducted a retrospective analysis of 364,813 AST results from the University of Pittsburgh Medical Center from 2015 to 2018. Data regarding infection site, hospital laboratory testing, organism identification, and antibiotic susceptibilities were extracted from the laboratory information system and anonymized prior to use. The pathogens studied included Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Acinetobacter baumannii, Staphylococcus aureus, Proteus mirabilis, and Enterococcus faecalis.ResultsWe identified 21 antibiotic-pathogen combinations where resistance was found in less than 1% of AST results. Concordant susceptibility results of levofloxacin and ciprofloxacin occurred the most frequently among antibiotic pairs. Additionally, concordant susceptibility results were more common within antibiotics belonging to the same antibiotic class than between classes. P. aeruginosa had the highest rate of overall concordant results with concordance occurring within all -lactam classes. In contrast, K. pneumoniae and P. mirabilis showed the least concordance, suggesting that their resistance profiles are less predictable. Notably, we did not identify any pairs of antibiotics that strongly exhibited discordant susceptibility results regardless of the microorganism.ConclusionUsing routinely collected clinical microbiological data, we were able to characterize pathogen-antibiotic combinations where resistance is rarely seen. Additionally, we identified pairs of antibiotics that frequently exhibited concordance susceptibilities both within and between classes. Lastly, we were unable to find evidence of discordant susceptibility results, indicating that more clinical research is needed to determine the efficacy of collateral sensitivity treatment techniques.Disclosures All authors: No reported disclosures.

Carbapenemase Genes and Multidrug Resistance of Acinetobacter Baumannii: A Cross Sectional Study of Patients with Pneumonia in Southern Vietnam.

Background: Acinetobacter baumannii (Ab) is an opportunistic bacterial pathogen found in hospital-acquired infections including nosocomial pneumonia, especially multidrug-resistant Ab. This study aims to survey the drug resistance profiles of Ab isolated from patients in Thong Nhat Dong Nai General Hospital and assess the relationship between genotypes and antibiotic resistance; Methods: Ninety-seven Ab strains isolated from 340 lower respiratory tract specimens among pneumonia patients were used to screen the most common local carbapenemase genes. Antimicrobial susceptibility testing results and demographic data were collected and minimum inhibitory concentrations (MIC) of colistin were also determined; Results: Over 80% and 90% of Ab strains were determined as carbapenem-resistant and multidrug-resistant (MDR), respectively. Most of the strains carried carbapenemase genes, including blaOXA-51, blaOXA-23-like, blaOXA-58-like, and blaNDM-1, with proportions of 97 (100%), 76 (78.4%), 10 (10.3%), 6 (6.2%), respectively. Amongst these genes, blaOXA-23-like was the only gene which significantly influenced the resistance (p < 0.0001); and Conclusions: The severity of Ab antibiotic resistance is urgent and specifically related to carbapenemase encoding genes. Therefore, screening of MDR Ab and carbapenemase for better treatment options is necessary.