Clinical And Laboratory Standards Institute Research Articles

Antimicrobial susceptibility of Gram-Negative Infections in King Faisal Medical Complex at Taif, Saudi Arabia

Objectives: Describe susceptibility patterns to several antimicrobials in Gram-negative pathogens isolated from patients in King FaisalMedical Complex (KFMC) at Taif, Saudi Arabia over a 6-month period. Methods: The study included a cumulative antibiogram of Gram-negative bacteria (GNB). Interpretation of the antimicrobial susceptibilitytests was based on the Clinical and Laboratory Standards Institute (CLSI) guidelines and the Phoenix system. Results: Overall, 763 clinical infections by GNB isolates of the specimens collected during six months were culture-positive. Amongthe array of GNB, Escherichia coli numbered 290 (38.0%) was the most frequently identified, then Klebsiella pneumoniae 276 (36.2%),Pseudomonas aeruginosa 77 (10.1%), Acinetobacter baumannii 48 (6.3%), Proteus spp. 31 (4.1%), Citrobacter koseri 11 (1.4%), Serratiaspp. 8 (1.0 %), Enterobacter aerogenes 7 (0.9%), Klebsiella Oxytoca 4 (0.5%), Providencia rettgeri 3 (0.4 %), Klebsiella ozaenae 3 (0.4%),Morganella morganii 2 (0.3%), Stenotrophomonas maltophilia 2 (0.3 %), and Pseudomonas puda 1 (0.1%). Fifty-one isolates were resistantto all tested antibiotics, but 97 (12.7 %) were susceptible to all the tested antibiotics. The majority (87.3%) of isolates were resistant toone or more antimicrobials tested. In general, 83% of the bacterial species were MDR. The carbapenem sensitivity was 68.7% for allGNB isolates, 47.3% and 52.3% of K. pneumoniae, 20.8% and 25% of Acinetobacter, and 64.1% and 75.6% of P. aeruginosa to imipenemand meropenem, respectively. The carbapenem sensitivity for E. coli was extremely high showing 100% and 99.9% for imipenem andmeropenem, respectively. Antibiotic sensitivity of the most isolated GNB pathogens was highly variable showing that tigecycline is themost effective antibiotic with 82.4% sensitivity while was non-effective for Acinetobacter. The colistin sensitivity was 88.3% for E. coli,69.2% for P. aeruginosa, 45.5% for K. pneumoniae and less effective against A. baumannii. Conclusion: Antibiotic resistance among K. pneumoniae, A. baumannii and P. aeruginosa was high for many used antibiotics, thus continued surveillance is needed.

Profiling of circulating glial cells for accurate blood-based diagnosis of glial malignancies.

Here, we describe a blood test for the detection of glial malignancies (GLI-M) based on the identification of circulating glial cells (CGCs). The test is highly specific for GLI-M and can detect multiple grades (II-IV) and subtypes including gliomas, astrocytomas, oligodendrogliomas, oligoastrocytomas and glioblastomas, irrespective of gender and age. Analytical validation of the test was performed as per Clinical and Laboratory Standards Institute (CLSI) guidelines. Real-world performance characteristics of the test were evaluated in four clinical (observational) studies. The test has high analytical sensitivity (95%), specificity (100%) and precision (coefficient of variation [CV] = 13.7% for repeatability and CV = 23.5% for within laboratory precision, both at the detection threshold) and is not prone to interference from common drugs and serum factors. The ability of the test to detect and differentiate GLI-M from non-malignant brain tumours (NBT), brain metastases from primary epithelial malignancies (EPI-M) and healthy individual donors (HD) was evaluated in four clinical cohorts. Across these clinical studies, the test showed 99.35% sensitivity (95% confidence interval [CI]: 96.44%-99.98%) and 100% specificity (95% CI: 99.37%-100%). The performance characteristics of this test support its clinical utility for diagnostic triaging of individuals presenting with intracranial space-occupying lesions (ICSOL).

Frequency of Vancomycin and Aminoglycoside Resistance Genes in Enterococcus spp. Isolated from Chicken Raw Meat Samples

Background: Enterococci are main normal microbial flora of both humans and animals and can survive in a diverse range of environments. These bacteria carry out aminoglycoside and vancomycin resistance genes and spread them in environment by many routs such as chicken meat products. The present study was aimed to determine the frequency of aminoglycoside and vancomycin resistant genes in Enterococcus species isolated from chicken meat specimens.
 Methods: A total of 250 chicken raw meat specimens was prepared from slaughterhouses at Zanjan province, cultured at BHI broth and incubated at 37°C for 24h. The positive cultures were sub-cultured in blood agar plates and grown colonies identified using phenotypical and biochemical tests. Antibiotic susceptibility was determined according to the Clinical and Laboratory Standards Institute (CLSI) standards and PCR assays were performed to detect vanA, vanB, aph (2")1c, aph (2")1b, aph (2")1d, ant(3'), aph(3')IIIa, ant(4')1a, ant(6') and aac(6') genes.
 Results: In total, 100 Enterococcus species isolated from 250 specimens and 35% of them belonged to E. faecalis and the others were E. faecium (65%). The prevalence of the vanA, vanB, aph (2")1c, aph (2")1b, aph (2")1d, ant(3'), aph(3')IIIa, ant(4')1a, ant(6') and aac(6') genes among the 100 Enterococcus species was 14%, 12%, 10%, 1%, 2%, 50%, 26%, 9%, 18% and 22%, respectively.
 Conclusion: The current study revealed that the rate of antimicrobial resistance genes to aminoglycosides and vancomycin was worrying and health measurements in meat products industries must be performed to prevent spread of antimicrobial resistance elements among bacteria.

Occurrence of Salmonella Species in Local and Commercial Chickens Slaughtered at Samaru and Sabongari Live Bird Markets, Kaduna State

Salmonellosis is a bacterial infection caused by members of the genus Salmonella. It is one of the most common and important zoonotic diseases. The route of infection from animals to humans is usually through contaminated food, water and environment. Bacteriological investigation on 303 cloacal swab samples collected from local (139) and commercial (164) chickens slaughtered at Samaru and Sabon-gari live bird markets, Kaduna State was carried out to determine the occurrence of Salmonella species. Cultural isolation and identification using conventional biochemical tests, microgen test kit™ and Polymerase Chain Reaction (PCR) amplification of invA gene of the Salmonella isolates was carried out. Isolates were subjected to antimicrobial susceptibility tests, phenotypic detection of Extended Spectrum Beta Lactamases (ESBLs) producing Salmonella isolates using the modified Clinical and Laboratory Standards Institute (CLSI) ESBL confirmatory test. The occurrence of Salmonella species based on cultural and biochemical tests was found to be 13 (4.29%), microgen kit identified 7 (53.8%) of the 13 Salmonella species while PCR based on invA gene confirmed 9 (69.2%) as the overall occurrence rate of Salmonella species. Meanwhile, the study also revealed rate of occurrence of Salmonella species in local chickens 8 (61.5%) which was higher compared to commercial chickens 1 (7.69%) with a statistical significant association (χ2 = 8.775, P = 0.003) between the occurrence of Salmonella species in local and commercial chickens. Antimicrobial susceptibility testing was carried out using panel of 12 antibiotics from 8 different antibiotic classes. Highest rate of sensitivity of the isolates to antibiotics was observed for Ofloxacin with 90%, while all the isolates (100%) were resistant to Nalidixic Acid, Cefazolin, Amoxicillin + Clavulanic Acid, Oxacillin and Penicillin. This study revealed multidrug-resistance (MDR) profile of Salmonella with a total of (25%) of Salmonella isolates being resistant to 5 antibiotics belonging to 4 different classes of antimicrobials with the highest multiple antibiotic-resistant (MAR) indices ranging from 0.58 to 0.91. All the nine (9) isolates of Salmonella tested were found to be negative for ESBLs production. Therefore, it is concluded that Salmonella species are present in local and commercial chickens slaughtered at Samaru and Sabon-gari live bird markets, Kaduna State and could pose serious public health risks to handlers and to consumers of poultry meat and its products.

Zuccagnia punctata Cav., a Potential Environmentally Friendly and Sustainable Bionematicide for the Control of Argentinean Horticultural Crops.

This research was designed to investigate the metabolite profiling, phenolics, and flavonoids content as well as the potential nematicidal properties of decoction (ZpDe), orange-yellow resin (ZpRe) and essential oil (ZpEO) from Argentinean medicinal plant Zuccagnia punctata Cav. Additionally, the antioxidant and antibacterial properties of ZpDe and ZpEO were determined. Metabolite profiling was obtained by an ultrahigh-resolution liquid chromatography MS analysis (UHPLC-ESI-QTOF/OT-MS-MS) and GCMS. The nematicidal activity was assayed by a standardized method against Meloidogyne incognita. The antioxidant properties were screened by four methods: (2,2-diphenyl-1-picrylhydrazyl assay (DPPH), Trolox equivalent antioxidant activity assay (TEAC), ferric-reducing antioxidant power assay (FRAP), and lipid peroxidation in erythrocytes (ILP). The antibacterial activity was evaluated according to the Clinical and Laboratory Standards Institute (CLSI) rules. The ZpDe, ZpRe and ZpEO displayed a strong nematicidal activity with an LC50 of 0.208, 0.017 and 0.142 mg/mL, respectively. On the other hand, the ZpDe showed a strong DPPH scavenging activity (IC50 = 28.54 µg/mL); ILP of 87.75% at 250 µg ZpDe/mL and moderated antimicrobial activity. The ZpEO showed promising activity against a panel of yeasts Candida albicans and non-albicans (ATCC and clinically isolated) with MIC values from 750 to 1500 µg/mL. The ZpDe showed a content of phenolics and flavonoid compounds of 241 mg GAE/g and 10 mg EQ/g, respectively. Fifty phenolic compounds were identified in ZpDe by ultrahigh-resolution liquid chromatography (UHPLC-PDA- Q-TOF-MS) analysis, while forty-six phenolic compounds were identified in ZpRe by UHPLC-ESI-Q-OT-MS-MS and twenty-nine in ZpEO using a GC-MS analysis, updating the knowledge on the chemical profile of this species. The results support and standardize this medicinal plant mainly as a potential environmentally friendly and sustainable bionematicide for the control of Argentinean horticultural crops including tomatoes and peppers and as a source of antimicrobial and antioxidant compounds which could be further explored and exploited for potential applications.

Comparative evaluation of antifungal susceptibility testing methods for Rhizopus species isolates.

The mainstay of treatment for COVID-19-associated mucormycosis was liposomal Amphotericin B. Other antifungal agents, such as posaconazole and isavuconazole, were used as well. The Clinical and Laboratory Standards Institute (CLSI) and the European Committee on Antimicrobial Susceptibility Testing recommend broth microdilution methods for antifungal susceptibility testing. In this regard, the present study aimed to see what potency and zone diameters correlate with the gold standard broth microdilution method. All the isolates were identified by matrix-assisted laser desorption ionization-time-of-flight. In total, 127 isolates of 83Rhizopus oryzae complex and 44 isolates ofRhizopus microsporuscomplex were selected. Anti-fungal susceptibility testing by disc diffusion and E-test was performed on Mueller Hinton Agar and compared with the CLSI broth microdilution method of Anti-fungal susceptibility testing. Percentage agreement was found to be more in the case of the E test than the disc diffusion method. In the case of R. oryzae, posaconazole had 98.79% agreement with broth microdilution followed by Isavuconazole (97.59%), Itraconazole (96.38%), and Amphotericin B (91.56%). Disc diffusion correlates well with broth microdilution, although its correlation is weaker when compared to the E test. Effective concentration of Amphotericin B discs for antifungal susceptibility testing depends on the specific Rhizopus species.

Utilizing the photodynamic properties of curcumin to disrupt biofilms in Cutibacterium acnes: A promising approach for treating acne

BackgroundThe treatment of acne vulgaris is often challenging due to the antibiotic resistance frequently observed in Cutibacterium acnes (C.acnes), a prevalent bacterium linked to this condition. ObjectiveThe objective of this research was to examine the impact of curcumin photodynamic therapy (PDT) on the survival of C.acnes and activity of biofilms produced by this microorganism. MethodsFollowing the Clinical and Laboratory Standards Institute (CLSI) guidelines, we assessed the drug sensitivity of 25 clinical C.acnes strains to five antibiotics (erythromycin, clindamycin, tetracycline, doxycycline, minocycline) and curcumin by implementing the broth microdilution technique. In addition, we established C.acnes biofilms in a laboratory setting and subjected them to curcumin-PDT(curcumin combined with blue light of 180 J/cm2). Afterwards, we evaluated their viability using the XTT assay and observed them using confocal laser scanning microscopy. ResultsThe result revealed varying resistance rates among the tested antibiotics and curcumin, with erythromycin, clindamycin, tetracycline, doxycycline, minocycline, and curcumin exhibiting resistance rates of 72 %, 44 %, 36 %, 28 %, 0 %, and 100 %, respectively. In the curcumin-PDT inhibition tests against four representative antibiotic-resistant strains, it was found that the survival rate of all strains of planktonic C. acnes was reduced, and the higher the concentration of curcumin, the lower the survival rate. Furthermore, in the biofilm inhibition tests, the vitality and three-dimensional structure of the biofilms were disrupted, and the inhibitory effect became more significant with higher concentrations of curcumin. ConclusionThe results emphasize the possibility of using curcumin PDT as an alternative approach for the treatment of C.acnes, especially in instances of antibiotic-resistant variations and infections related to biofilms.

Antibiogram of selected bacteria isolated from urine polluted environment in Benue State Campus, Makurdi

Urine contaminated soil contains various potential hazardous components which create an environment for bacteria to adapt, multiply and share their resistant genes. This study aimed to determine the antibiogram of selected bacteria isolated from urine polluted environment. Urine contaminated soil were randomly sampled from four different sites in Benue State University, Makurdi metropolis. Standard microbiological cultures, biochemical tests, modified Kirby-Bauer techniques and Clinical and Laboratory Standard Institute (CLSI) were used to isolate, identify, and determine the antibiotic susceptibility profiles of the bacteria at a 0.5 scale Mcfarland’s standard (1.5x 108 cells/ml). Bacteria insolated include Bacillus sp. (25), E. coli (13), Klebsiella sp. (10), Staphylococcus sp. (8) Salmonella sp. (7). The colony and colony forming unit (CFU) of eastern wing campus (7.85 X 107) was slightly higher compared to western wing campus (7.05 x 107). Escherichia coli (100 %) was resistant to all the antibiotics (Imipinem, Oxacillin, Ciprofloxacin, and Gentamicin), Staphylococcus spp isolates obtained were resistant to all the antibiotics except 50 % that were susceptible to Gentamicin, while 50 % of Bacillus spp on the other hand was susceptible to Imipenem, all were susceptible to Gentamicin and Ciprofloxacin (100 %); and all were however resistant to Oxacillin (100.00 %). Salmonella spp and Klebsiella spp showed similar pattern of susceptibility. All the isolates of the two organisms were susceptible to Imipenem, Gentamicin and Ciprofloxacin (100 %). All the isolates were resistant to Oxacillin. All the selected bacteria showed resistance to at least one antibiotic (P˂0.05) Unavailability of good toilet systems has contributed to the open urination and environmental contamination. Provision of more and adequate toilet facilities within the university premises and good antibiotic misuse orientation should be giving priority to prevent excessive contamination of soil with urine and antibiotic resistance.

Evaluation of a Method for Standardized Antimicrobial Susceptibility Testing with Mycoplasma hyorhinis Field Isolates.

Organizations like the Clinical and Laboratory Standards Institute (CLSI) or the European Committee of Antimicrobial Susceptibility Testing (EUCAST) provide standardized methodologies for antimicrobial susceptibility testing of a wide range of nonfastidious and fastidious bacteria, but so far not for Mycoplasma spp. of animal origin. Recently, a proposed method for the standardized broth microdilution testing of Mycoplasma hyorhinis using commercial Sensititre microtiter plates was presented. In this study, we evaluated this broth microdilution method with 37 field isolates and tested their susceptibility toward the following antimicrobial agents: doxycycline, enrofloxacin, erythromycin, florfenicol, gentamicin, marbofloxacin, tetracycline, tiamulin, tilmicosin, tulathromycin, and tylosin. The isolates originated from different countries, isolation sites, and years. The broth microdilution method was carried out using a modified Friis broth as the culture and test medium. For macrolides and lincosamides, a bimodal distribution with elevated MIC values could be observed for almost half of the tested field isolates, deducing reduced susceptibility toward these substances. With a recently published protocol, we were able to test a variety of field isolates, and consistent data could be obtained. Using this method, monitoring studies of Mycoplasma hyorhinis isolates can be carried out in a comparable manner, and the observed susceptibility profiles can be screened for possible changes in MIC values in the future.

2716. Epidemiology of invasive fungal infection in pediatric liver transplant recipients: A retrospective, single-center study, 2012-2022

Abstract Background Studies on liver transplant (LT) recipients have reported an incidence of invasive fungal infection (IFI) ranging from 2.5 to 5%; however, antifungal prophylaxis has not yet been approved by the Ministry of Food and Drug Safety in Korea. We investigated the incidence of early-onset IFI and its characteristics in pediatric LT recipients in Korea, and also explored the risk factors for IFIs. Methods This is a retrospective, single-center study on children (< 19 years of age) who have undergone LT from 2012 to 2022 at Severance Hospital, Korea. IFI was defined as the detection of fungus in sterile fluid, tissue, and/or blood with symptoms of a fungal infection. Superficial fungal infection and colonization on the skin or urine were excluded. The primary outcome is the occurrence of IFI within 90 days of LT. The logistic regression method was used to analyze the risk factors for IFI. Results A total of 104 LT children were included, among whom 6 received multiple transplantations, resulting in 111 LT cases. 42% (n = 44) were male, and the median age at LT was 4.0 years of age (IQR 1.0–11.0). Two thirds of the patients received LT due to biliary atresia (n = 69, 66%), and the remaining were diagnosed with acute liver failure (n = 17, 16%), miscellaneous causes (n = 11, 11%), and so on (n = 7, 7%). Antifungal prophylaxis, except nystatin gargle, was done in 12.8% of recipients. IFI was identified in 19 patients (18%), and due to five multiple IFI events per patient, a total of 23 IFI events were noted at a median time of 16.5 days after LT (IQR 10-38). 87% of the pathogens detected were Candida species (C. albicans 40%, C. parapsilosis 35%, C. auris 15%), and Aspergillus fumigatus (13%). Antifungal susceptibility patterns are described in Table 1. The risk of IFI was significantly increased in those who underwent acute re-transplantation, postoperative intervention, or surgery due to bleeding, vascular, and bile duct complications (OR = 4.6; 95% CI, 1.5–13.6; P = 0.006) 8) and renal replacement therapy (OR=3.2; 95% CI, 1.1-8.8; P=0.028).Table.Antifungal susceptibility patterns of identified pathogens according to Clinical and Laboratory Standards Institute (CLSI). a Number of cases identified with the fungal pathogen b Antifungal susceptibility testing has to be additionally requested, so it was not performed in all cases. c 1 case had a fluconazole-resistant C.parapsilosis strain with intermediate resistance to other antifungal agents (MIC: fluconazole 32, micafungin 2, caspofungin 2, voriconazole 0.12, amphotericin B 0.5). d CLSI does not provide a tentative MIC breakpoint for voriconazole and other second generation azoles, but that of fluconazole may be considered as a surrogate. Conclusion The incidence of early IFI after LT in Korean children is considerable; therefore, universal antifungal prophylaxis is necessary. High-risk IFI patients, such as those undergoing reoperation, intervention, or renal replacement therapy, require attention and close monitoring. Disclosures All Authors: No reported disclosures

1946. In Vitro Activity of Ceftobiprole against Staphylococcus aureus Bacteremia Isolates from the United States (2018–2020)

Abstract Background Ceftobiprole (BPR) is an advanced-generation cephalosporin approved in Europe and many non-European countries for the treatment of community-acquired pneumonia and non–ventilator-associated hospital-acquired pneumonia in adults. A Phase 3 clinical trial (NCT03138733) was recently completed with BPR for the treatment of Staphylococcus aureus (SA) bacteremia, including infective endocarditis. This study evaluated the activity of BPR and comparators against recent SA isolates causing bloodstream infections (BSI) in patients hospitalized at medical centers in the United States (US). Methods A total of 1,946 SA isolates from 32 US medical centers (2018–2020) were collected from patients with BSI. 53 isolates from endocarditis patients were included. Isolates were tested for antimicrobial susceptibility using the Clinical and Laboratory Standards Institute (CLSI) broth microdilution method. MIC interpretations for BPR and comparators utilized European Committee on Antimicrobial Susceptibility Testing (EUCAST) or CLSI criteria, respectively. Multidrug-resistant (MDR) isolates were non-susceptible to ≥ 3 of the following drugs without regard to oxacillin resistance: clindamycin, daptomycin, erthryomycin, gentamicin, levofloxacin, tetracycline, and trimethoprim-sulfamethoxazole. No isolates were resistant to linezolid, tigecycline, or vancomycin. Results BPR inhibited 99.5% of all SA at ≤ 2 mg/L, which is the EUCAST susceptibility breakpoint (MIC50/90, 0.5/2 mg/L). The MIC50/90 values were stable over all 3 surveillance years and identical to previously reported values from analogous isolates collected in 2016–2017. BPR activity was maintained against the methicillin-resistant SA (MRSA) subset (41% of all SA; 98.8% susceptible). All isolates from endocarditis patients were susceptible to BPR. 10 MRSA isolates (0.5%) were resistant to BPR with MIC values of 4 mg/L. Of 288 MDR isolates, 96.9% remained susceptible to BPR, while only 78.8% of the same isolate set was susceptible to ceftaroline. Conclusion These in vitro results extend previous surveillance data that suggest that BPR represents a potential option for treating BSI and endocarditis caused by SA in US hospitals, including MRSA and MDR isolates. Disclosures Leonard R. Duncan, PhD, AbbVie: Grant/Research Support|Basilea: Grant/Research Support|CorMedix: Grant/Research Support|Melinta: Grant/Research Support|Pfizer: Grant/Research Support Mariana Castanheira, PhD, AbbVie: Grant/Research Support|Basilea: Grant/Research Support|bioMerieux: Grant/Research Support|Cipla: Grant/Research Support|CorMedix: Grant/Research Support|Entasis: Grant/Research Support|Melinta: Grant/Research Support|Paratek: Grant/Research Support|Pfizer: Grant/Research Support|Shionogi: Grant/Research Support Jennifer Smart, PhD, Basilea Pharmaceutica International Ltd, Allschwil, Switzerland: Stocks/Bonds Mark E. Jones, PhD, Astellas Pharma Global Development, Inc: Support for the present publication|Basilea Pharmaceutica International Ltd: Employee of Basilea Pharmaceutica International Ltd|Basilea Pharmaceutica International Ltd: Stocks/Bonds Rodrigo E. Mendes, PhD, AbbVie: Grant/Research Support|Basilea: Grant/Research Support|Cipla: Grant/Research Support|Entasis: Grant/Research Support|GSK: Grant/Research Support|Paratek: Grant/Research Support|Pfizer: Grant/Research Support|Shionogi: Grant/Research Support

2122. In Vitro Activity of Cefepime-Taniborbactam Against Clinically Significant Gram-Negative Bacteria Isolated from Patients with Cancer

Abstract Background Gram negative (GN) bacterial infections are on the rise in patients with cancer (PWC). There is an urgent need for new therapies to address the rise of infections caused by multidrug resistant (MDR) GN pathogens. Taniborbactam is a β-lactamase inhibitor in combination with cefepime may offer a potential treatment option for patients with serious GN bacterial infections. This study aimed to evaluate the in vitro activity of a novel combination of cefepime-taniborbactam and comparators against recent Gram-negative clinical isolates from PWC. Methods Recent GN clinical isolates from PWC were tested against cefepime-taniborbactam and comparators. Clinical and laboratory Standards Institute (CLSI) approved broth microdilution method was used. Appropriate ATCC controls were included. MIC90, and percent of susceptibility calculations were made using FDA breakpoints when available. We tested 100 GN isolates and further testing is ongoing. Results Cefepime-taniborbactam and comparators antibiotics susceptibility percentage (S: %), and MIC90 are shown in the table below. Cefepime-taniborbactam demonstrated highly potent activity against all of tested Enterobacterales including extended spectrum Beta-lactamase (ESBL), and carbapenem-resistant Enterobacterales (CRE) as well as against P. aeruginosa and Stenotrophomonas maltophilia. At a provisional breakpoint of 16/4 mg/L, cefepime-taniborbactam showed highest activity against all tested isolates when compared to cefepime and other comparators, including activity against ESBL, CRE, MDR P. aeruginosa and S. maltophilia. Comparative study between cefepime-taniborbactam and comparators for MIC90 (mg/L.) and Susceptibility (%) results against Gram-negative bacteria isolated from patients with cancer Conclusion Our data demonstrate that cefepime-taniborbactam has promising activity against clinically significant multidrug-resistant (MDR) GN bacterial pathogens isolated from PWC and it showed high activity compared to other commonly used broad spectrum antimicrobial agents. Disclosures Joel Rosenblatt, PhD, Novel Anti-Infective Technologies, LLC: Licensed Technology Issam I. Raad, Distinguished Professor, Novel Anti-Infective Technologies, LLC: Technology License

2810. A synergy test to assess the activity of the Ceftazidime-Avibactam and Aztreonam combination: An experience from a single centre in Malaysia

Abstract Background Southeast Asia has a high prevalence of metallo-β-lactamase-producing carbapenem-resistant Enterobacterales (CRE). Ceftazidime-avibactam (CZA) and Aztreonam (ATM) combination is one of the preferred therapeutic options against them. Methods A prospective study was performed at a university hospital in Kuala Lumpur, Malaysia, involving CRE isolates resistant to CZA and ATM. Susceptibility testing results were interpreted using the Clinical and Laboratory Standards Institute (CLSI) breakpoints. A synergy test for both agents [as in Falcone et al. study (CID 2021:72)] was carried out using the double disk synergy (DDS) and the gradient test superposition (GTS) methods. Synergy was considered present when the inhibition zone between the two disks became evident and if CZA reduced the ATM minimum inhibitory concentration (MIC) below its CLSI susceptibility cut-off (≤4 mg/L). Results Eleven isolates (8 K. pneumoniae, 2 E. coli, and 1 K. aerogenes) from 10 patients were tested. Concordant results were seen for both methods for all the isolates. Synergy was demonstrated with 8 isolates; for 2 of the 3 isolates with no synergy, the MIC of ATM reduced to an intermediate result after GTS. The most common sites of infection were bloodstream infection (4) and intra-abdominal infection (3). Five patients received the CZA-ATM combination (one received two courses of CZA-ATM). Five isolates from four patients demonstrated synergy, and one showed intermediate synergy. The latter received additional IV tigecycline. The median time to CZA-ATM initiation from the index culture was 8 (3-13) days. The median duration of therapy was 21 (6-28) days. Four patients responded favorably to the agents (survived the infection), while the remaining patient died. For those that did not receive CZA-ATM, one received polymyxin-based therapy, one received high-dose, extended-infusion meropenem, and one received no treatment. Only the patient that received meropenem survived the infection. Please refer to Table 1.0 for more detail. Conclusion Based on this small sample size, only a 73% synergy rate between CZA and ATM was seen for our CRE isolates resistant to CZA and ATM. Favorable treatment response was seen in those receiving the CZA-ATM combination therapy when synergy was demonstrated Disclosures All Authors: No reported disclosures

2795. Cefepime Versus Meropenem for Infections Due to HECCcK-YeS-MAm Organisms with Cefepime MICs of 4-8 mCg/mL (S-DD)

Abstract Background Recent guidance from IDSA recommends meropenem for treatment of organisms at moderate-high risk for inducible chromosomal AmpC β-lactamase hyperproduction (AmpC organisms) with a cefepime minimum inhibitory concentration (MIC) of 4-8 mCg/mL (susceptible dose-dependent or S-DD).1 This runs contrary to pharmacokinetic/pharmacodynamic data and Clinical and Laboratory Standards Institute (CLSI) M100 guidance, which considers organisms ≥ 16 mCg/mL resistant.2 The purpose of this study is to evaluate the clinical efficacy of cefepime versus meropenem for the treatment of infections caused by AmpC organisms with a S-DD cefepime MIC. Methods This was a retrospective study evaluating patients treated within Indiana University Health from 2015-2022. All cefepime S-DD AmpC isolates were included. Exclusion criteria were < 48 hours of treatment, multiple days of therapy with another active agent, inadequate dosing, extended spectrum β-lactamase (ESBL) co-production, and carbapenem resistance. The primary endpoint of this study was a composite of in-hospital all-cause mortality and antibiotic escalation due to clinical worsening. Secondary endpoints include positive repeat blood cultures within 7 days of treatment initiation, and ESBL or carbapenem resistant organism isolation during or following treatment. Results 355 isolates were screened. 71 patients were included in the final analysis, 43 in the cefepime group and 28 in the meropenem group. Baseline characteristics were not significantly different. Enterobacter cloacae made up 79% of cases. The primary endpoint occurred in 13/43 (30%) of patients on cefepime and 7/28 (25%) of patients on meropenem (P=0.63). Treatment escalation and escalation due to clinical worsening was higher in the cefepime group with 7 (16%) and 6 (14%) incidents respectively compared to none in the meropenem group (P=0.03; P=0.04). No other endpoints, including all-cause mortality, were significantly different between groups. Conclusion Cefepime remains a viable treatment option for ESBL-negative, AmpC organisms with MICs in the S-DD range. Disclosures All Authors: No reported disclosures

2162. In Vitro Antimicrobial Activity of Ceftobiprole against Streptococcus pneumoniae Isolates from the United States (2016–2020)

Abstract Background Ceftobiprole (BPR) is an advanced-generation cephalosporin approved in Europe and many non-European countries for the treatment of community-acquired pneumonia and non–ventilator-associated hospital-acquired pneumonia in adults caused by indicated species, including Streptococcus pneumoniae (SPN). This study evaluated the in vitro antimicrobial activity of BPR and comparator agents against recent SPN isolates causing lower respiratory tract infections in patients at medical centers in the United States (US). Methods A total of 2,793 SPN isolates from 32 US medical centers (2016–2020) were collected from patients with lower respiratory tract infections. Isolates were tested for antimicrobial susceptibility using the Clinical and Laboratory Standards Institute (CLSI) broth microdilution method. MIC interpretations for BPR and comparators utilized European Committee on Antimicrobial Susceptibility Testing (EUCAST) or CLSI criteria, respectively. The EUCAST BPR susceptibility breakpoint for SPN was 0.5 mg/L. Results BPR inhibited 99.5% of all SPN isolates at the EUCAST breakpoint (MIC50/90, 0.015/0.25 mg/L). The MIC50/90 values were stable over all 5 surveillance years. The following comparator agents displayed lower activity against the isolate set: clindamycin (85.5% susceptible [S]), erythromycin (53.2% S), penicillin (63.2% S using oral breakpoints), tetracycline (79.4% S), and trimethoprim-sulfamethoxazole (72.8% S). BPR maintained excellent in vitro activity against each of the isolate subsets resistant to these comparator antimicrobials (95.4–98.8% S to BPR depending on the comparator antimicrobial; 95.4% of the penicillin-resistant isolates were S to BPR). This SPN isolate set was also 99.4% S to levofloxacin, 97.4% S to ceftriaxone (using non-meningitis breakpoints), and 100% S to linezolid and vancomycin. Conclusion BPR exhibited potent in vitro antimicrobial activity against recent SPN clinical isolates collected in US medical centers (2016–2020). These data indicate that BPR merits further investigation as a potential option for the treatment of lower respiratory tract infections caused by SPN in the US. Disclosures Leonard R. Duncan, PhD, AbbVie: Grant/Research Support|Basilea: Grant/Research Support|CorMedix: Grant/Research Support|Melinta: Grant/Research Support|Pfizer: Grant/Research Support Mariana Castanheira, PhD, AbbVie: Grant/Research Support|Basilea: Grant/Research Support|bioMerieux: Grant/Research Support|Cipla: Grant/Research Support|CorMedix: Grant/Research Support|Entasis: Grant/Research Support|Melinta: Grant/Research Support|Paratek: Grant/Research Support|Pfizer: Grant/Research Support|Shionogi: Grant/Research Support Jennifer Smart, PhD, Basilea Pharmaceutica International Ltd, Allschwil, Switzerland: Stocks/Bonds Mark E. Jones, PhD, Astellas Pharma Global Development, Inc: Support for the present publication|Basilea Pharmaceutica International Ltd: Employee of Basilea Pharmaceutica International Ltd|Basilea Pharmaceutica International Ltd: Stocks/Bonds Rodrigo E. Mendes, PhD, AbbVie: Grant/Research Support|Basilea: Grant/Research Support|Cipla: Grant/Research Support|Entasis: Grant/Research Support|GSK: Grant/Research Support|Paratek: Grant/Research Support|Pfizer: Grant/Research Support|Shionogi: Grant/Research Support

722. Risk Factors for Infection or Colonization with Ceftolozane/Tazobactam Non-Susceptible Extensively β-Lactam Resistant Pseudomonas aeruginosa

Abstract Background Treatment of infections due to multidrug resistant (MDR) Pseudomonas aeruginosa is complicated by co-resistance amongst traditional anti-pseudomonal β-lactams, as 50% of MDR isolates exhibit extensive β-lactam resistance (EBR, non-susceptible to cefepime, ceftazidime, piperacillin/tazobactam, and meropenem). Ceftolozane/tazobactam (C/T) was developed to combat MDR and EBR P. aeruginosa. Unfortunately, C/T resistance has proliferated. We designed this retrospective case-control study to identify risk factors for C/T non-susceptibility (NS) amongst EBR P. aeruginosa. Methods Between 2015 to 2020, hospitalized adult patients infected or colonized with EBR P. aeruginosa were identified. C/T susceptibility was defined per the 2023 Clinical and Laboratory Standards Institute (CLSI) guidelines (susceptible (S) if minimum inhibitory concentration (MIC) ≤ 4 mg/L, NS if MIC ≥ 8 mg/L). Patients with an EBR P. aeruginosa NS to C/T were classified as cases, whereas those with S isolates were controls. Patients with multiple EBR P. aeruginosa isolates over the study period were only included once. If a patient had a C/T NS isolate, they were classified as cases and the first C/T NS isolate was included as the index culture. If the patient did not have a C/T NS isolate over the study period, they were considered a control and the first C/T S isolate was the index culture. Bivariate and multivariate modeling was performed to identify independent predictors for C/T NS. Results 188 unique patients with C/T susceptibility performed were included in the study; 96 (51%) were C/T NS and 92 (49%) were C/T S. Table 1 shows the bivariate comparisons of key baseline characteristics between groups. Independent predictors of C/T NS are displayed in table 2. Conclusion Independent predictors for C/T NS amongst EBR P. aeruginosa isolates were a history of cancer, cystic fibrosis, and isolation of EBR P. aeruginosa in the past 90 days. While receipt of cefepime or ceftazidime in the past 90 days was associated with C/T NS in bivariate comparisons, the association did not remain in multivariate modeling. C/T exposure was not a statistically significant risk factor, but it was numerically associated with NS and the lack of significance was likely due to the small number of patients (n = 15) who received it. Disclosures Virginia M. Pierce, MD, FIDSA, UpToDate, Inc.: Authorship royalties jason M. Pogue, PharmD, AbbVie: Advisor/Consultant|Entasis: Advisor/Consultant|Ferring: Advisor/Consultant|GSK: Advisor/Consultant|Merck: Advisor/Consultant|Merck: Grant/Research Support|Qpex: Advisor/Consultant|Shionogi: Advisor/Consultant

In vitro activity of ceftaroline against bacterial isolates causing skin and soft tissue and respiratory tract infections collected in Latin American countries, ATLAS program 2016–2020

Objectives: Ceftaroline, a broad-spectrum cephalosporin has activity against Gram-positive and several Gram-negative bacteria (GNB). This study aimed to evaluate the antimicrobial activity of ceftaroline and comparators against isolates causing skin and soft tissue infections (SSTIs) and respiratory tract infections (RTIs) collected in Latin America (LATAM) in 2016-2020 as part of the Antimicrobial Testing Leadership and Surveillance program (ATLAS). Methods: Minimum inhibitory concentrations were determined using both Clinical and Laboratory Standards Institute (CLSI) and European Committee on Antimicrobial Susceptibility Testing (EUCAST) criteria. Results: Ceftaroline demonstrated potent activity against methicillin-susceptible Staphylococcus aureus (CLSI/EUCAST: MIC90 0.25 mg/L; susceptibility 100%), whereas activity against methicillin-resistant S. aureus varied for SSTIs (MIC90 1 mg/L; susceptibility 92.5%) and RTIs isolates (MIC90 2 mg/L; susceptibility 72.9%) isolates. For Streptococcus pneumoniae, particularly penicillin-resistant isolates commonly causing respiratory infections, high ceftaroline activity (MIC90 0.25 mg/L; susceptibility 100%/98.4%) was noted. All isolates of β-hemolytic streptococci were susceptible to ceftaroline [S. agalactiae: MIC90 0.03 mg/L (SSTIs); MIC90 0.015 mg/L (RTIs); susceptibility 100%; S. pyogenes: MIC90 0.008 mg/L; susceptibility 100%). Ceftaroline was highly active against Haemophilus influenzae including β-lactamase positive isolates (MIC90 0.06 mg/L; susceptibility 100%/85.7%). Ceftaroline demonstrated high activity against non-ESBL-producing GNB (E. coli: MIC90 0.5 mg/L, susceptibility 91.9%; K. pneumoniae: MIC90 0.25 mg/L, susceptibility 95.1%; K. oxytoca, MIC90 0.5 mg/L; susceptibility 95.7%). Conclusion: Ceftaroline was active against the recent collection of bacterial pathogens commonly causing SSTIs and RTIs in LATAM. Local and regional surveillance of antimicrobial resistance patterns are crucial to understand evolving resistance and guide treatment management.

Development and validation of an LC-MS/MS method for the simultaneous quantitation of angiotensin (1–7), (1–8), (1–9) and (1–10) in human plasma

Cardiovascular diseases have cast a significant negative impact on the lives of millions worldwide. Over the years, extensive efforts have been dedicated to enhancing diagnostic and prognostic tools for these diseases. A growing body of evidence indicates that the angiotensin convertase enzyme (ACE) and the angiotensin convertase enzyme 2 (ACE2), and angiotensin peptide levels could hold a pivotal role in assisting clinicians with the management of cardiovascular conditions, notably hypertension and heart failure. However, despite the considerable body of knowledge in this domain, a void remains in the field of analytical methodologies for these molecules. In this study, we present a fully validated LC-MS/MS method for the precise quantitation of plasma angiotensin (1–7), (1–8), (1–9), and (1–10), following the guidelines set by the Clinical and Laboratory Standards Institute (CLSI). Our method not only enables the accurate quantification of angiotensin peptides but also provides a means to assess ACE and ACE2 activity. Remarkably, our method achieved a Lower Limit of Measurement Interval (LLMI) as low as 5 pg/mL. This has enabled the detection of angiotensin (1–7), (1–8), (1–9) and (1–10) and the accurate quantitation of angiotensin (1–7), (1–8) and (1–10) in all analyzed groups, including healthy controls, patients with high blood pressure, and patients with chronic kidney disease. To our knowledge, our method represents the most sensitive approach allowing for simultaneous quantitation of these four angiotensin peptides. A distinct advantage of our method, when compared to immunoassays, is its high sensitivity combined with comprehensive chromatographic separation of all currently known angiotensin peptides. This combination translates to an exceptional level of selectivity, underscoring the value and potential of our methodology in advancing cardiovascular disease research.

Disinfectant resistance of Salmonella enterica isolated from retail chicken in Hanoi, Vietnam

Salmonella enterica is the most common foodborne pathogen found in poultry processing and slaughterhouses; therefore, understanding the resistance of this bacteria group is critical for effective pathogen control. This research in Vietnam provides a new field for studying resistance to biocides and disinfectants, along with the distribution of genes coding for this characteristic in Salmonella species members. According to the Clinical and Laboratory Standards Institute (CLSI) guidelines, 119 strains of Salmonella bacteria underwent testing for minimum inhibitory concentration (MIC) with two compounds, BKC (benzalkonium chloride) and CPC (cetylpyridinium chloride). Moreover, these Salmonella strains were further characterised based on the genes responsible for disinfectant resistance. The results showed that the MICs of BKC and CPC were between 12.5-25 and 6.25-12.5 μg/ml, respectively. Furthermore, the presence of two genes, qacEand qacE∆, discovered in 61% (73/119) and 60% (72/119) of the strains, indicates the wide spread of disinfectant resistance genes is a novelty in the resistance of this bacteria group.

Effect of various concentrations of common organic solvents on the growth and proliferation ability of Candida glabrata and their permissible limits for addition in drug susceptibility testing.

Dimethyl sulfoxide (DMSO), acetone, ethanol, and methanol are organic solvents commonly used for dissolving drugs in antimicrobial susceptibility testing. However, these solvents have certain antimicrobial activity. Currently, standardized criteria for the selection and dosage of drug solvents in drug susceptibility testing research are lacking. The study aims to provide experimental evidence for the selection and addition limit of drug solvents for the in vitro antifungal susceptibility test of Candida glabrata (C. glabrata). According to the recommendation of the Clinical and Laboratory Standards Institute (CLSI) M27-A3, a 0.5 McFarland C. glabrata suspension was prepared and then diluted 1:1,000. Next, a gradient dilution method was used to prepare 20%, 10%, 5%, and 2.5% DMSO/acetone/ethanol/methanol. The mixture was plated onto a 96-well plate and incubated at a constant temperature of 35 °C for 48 h. The inhibitory effects of DMSO, acetone, ethanol, and methanol on C. glabrata growth and proliferation were analyzed by measuring optical density values at 600 nm (OD600 values). After 48 h incubation, the OD600 values of C. glabrata decreased to different extents in the presence of the four common organic solvents. The decrease in the OD600 values was greater with increasing concentrations within the experimental concentration range. When DMSO and acetone concentrations were higher than 2.5% (containing 2.5%) and methanol and ethanol concentrations were higher than 5.0% (containing 5.0%), the differences were statistically significant compared with the growth control wells without any organic solvent (P < 0.05). All four organic solvents could inhibit C. glabrata growth and proliferation. When used as solvents for drug sensitivity testing in C. glabrata, the concentrations of DMSO, acetone, ethanol, and methanol should be below 2.5%, 2.5%, 5%, and 5%, respectively.