Browsing by Subject "Microbial Sensitivity Tests"
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Item Open Access A Multicountry Molecular Analysis of Salmonella enterica Serovar Typhi With Reduced Susceptibility to Ciprofloxacin in Sub-Saharan Africa.(Clin Infect Dis, 2016-03-15) Al-Emran, Hassan M; Eibach, Daniel; Krumkamp, Ralf; Ali, Mohammad; Baker, Stephen; Biggs, Holly M; Bjerregaard-Andersen, Morten; Breiman, Robert F; Clemens, John D; Crump, John A; Cruz Espinoza, Ligia Maria; Deerin, Jessica; Dekker, Denise Myriam; Gassama Sow, Amy; Hertz, Julian T; Im, Justin; Ibrango, Samuel; von Kalckreuth, Vera; Kabore, Leon Parfait; Konings, Frank; Løfberg, Sandra Valborg; Meyer, Christian G; Mintz, Eric D; Montgomery, Joel M; Olack, Beatrice; Pak, Gi Deok; Panzner, Ursula; Park, Se Eun; Razafindrabe, Jean Luco Tsiriniaina; Rabezanahary, Henintsoa; Rakotondrainiarivelo, Jean Philibert; Rakotozandrindrainy, Raphaël; Raminosoa, Tiana Mirana; Schütt-Gerowitt, Heidi; Sampo, Emmanuel; Soura, Abdramane Bassiahi; Tall, Adama; Warren, Michelle; Wierzba, Thomas F; May, Jürgen; Marks, FlorianBACKGROUND: Salmonella enterica serovar Typhi is a predominant cause of bloodstream infections in sub-Saharan Africa (SSA). Increasing numbers of S. Typhi with resistance to ciprofloxacin have been reported from different parts of the world. However, data from SSA are limited. In this study, we aimed to measure the ciprofloxacin susceptibility of S. Typhi isolated from patients with febrile illness in SSA. METHODS: Febrile patients from 9 sites within 6 countries in SSA with a body temperature of ≥38.0°C were enrolled in this study. Blood samples were obtained for bacterial culture, and Salmonella isolates were identified biochemically and confirmed by multiplex polymerase chain reaction (PCR). Antimicrobial susceptibility of all Salmonella isolates was performed by disk diffusion test, and minimum inhibitory concentrations (MICs) against ciprofloxacin were measured by Etest. All Salmonella isolates with reduced susceptibility to ciprofloxacin (MIC > 0.06 µg/mL) were screened for mutations in quinolone resistance-determining regions in target genes, and the presence of plasmid-mediated quinolone resistance (PMQR) genes was assessed by PCR. RESULTS: A total of 8161 blood cultures were performed, and 100 (1.2%) S. Typhi, 2 (<0.1%) Salmonella enterica serovar Paratyphi A, and 27 (0.3%) nontyphoid Salmonella (NTS) were isolated. Multidrug-resistant S. Typhi were isolated in Kenya (79% [n = 38]) and Tanzania (89% [n = 8]) only. Reduced ciprofloxacin-susceptible (22% [n = 11]) S. Typhi were isolated only in Kenya. Among those 11 isolates, all had a Glu133Gly mutation in the gyrA gene combined with either a gyrA (Ser83Phe) or gyrB mutation (Ser464Phe). One Salmonella Paratyphi A isolate with reduced susceptibility to ciprofloxacin was found in Senegal, with 1 mutation in gyrA (Ser83Phe) and a second mutation in parC (Ser57Phe). Mutations in the parE gene and PMQR genes were not detected in any isolate. CONCLUSIONS: Salmonella Typhi with reduced susceptibility to ciprofloxacin was not distributed homogenously throughout SSA. Its prevalence was very high in Kenya, and was not observed in other study countries. Continuous monitoring of antimicrobial susceptibility is required to follow the potential spread of antimicrobial-resistant isolates throughout SSA.Item Open Access A prospective study of Escherichia coli bloodstream infection among adolescents and adults in northern Tanzania.(Transactions of the Royal Society of Tropical Medicine and Hygiene, 2020-05) Madut, Deng B; Rubach, Matthew P; Kalengo, Nathaniel; Carugati, Manuela; Maze, Michael J; Morrissey, Anne B; Mmbaga, Blandina T; Lwezaula, Bingileki F; Kilonzo, Kajiru G; Maro, Venance P; Crump, John ABackground
Characterization of the epidemiology of Escherichia coli bloodstream infection (BSI) in sub-Saharan Africa is lacking. We studied patients with E. coli BSI in northern Tanzania to describe host risk factors for infection and to describe the antimicrobial susceptibility of isolates.Methods
Within 24 h of admission, patients presenting with a fever at two hospitals in Moshi, Tanzania, were screened and enrolled. Cases were patients with at least one blood culture yielding E. coli and controls were those without E. coli isolated from any blood culture. Logistic regression was used to identify host risk factors for E. coli BSI.Results
We analyzed data from 33 cases and 1615 controls enrolled from 2007 through 2018. The median (IQR) age of cases was 47 (34-57) y and 24 (72.7%) were female. E. coli BSI was associated with (adjusted OR [aOR], 95% CI) increasing years of age (1.03, 1.01 to 1.05), female gender (2.20, 1.01 to 4.80), abdominal tenderness (2.24, 1.06 to 4.72) and urinary tract infection as a discharge diagnosis (3.71, 1.61 to 8.52). Of 31 isolates with antimicrobial susceptibility results, the prevalence of resistance was ampicillin 29 (93.6%), ceftriaxone three (9.7%), ciprofloxacin five (16.1%), gentamicin seven (22.6%) and trimethoprim-sulfamethoxazole 31 (100.0%).Conclusions
In Tanzania, host risk factors for E. coli BSI were similar to those reported in high-resource settings and resistance to key antimicrobials was common.Item Open Access Antimicrobial-Resistant Shigella spp. in San Diego, California, USA, 2017-2020.(Emerging infectious diseases, 2022-06) Gaufin, Thaidra; Blumenthal, Jill; Ramirez-Sanchez, Claudia; Mehta, Sanjay; Pride, David T; Fierer, Joshua; Jenks, Jeffrey DAnnually, Shigella spp. cause ≈188 million cases of diarrheal disease globally, including 500,000 cases in the United States; rates of antimicrobial resistance are increasing. To determine antimicrobial resistance and risk factors in San Diego, California, USA, we retrospectively reviewed cases of diarrheal disease caused by Shigella flexneri and S. sonnei diagnosed during 2017-2020. Of 128 evaluable cases, S. flexneri was slightly more common than S. sonnei; most cases were in persons who were gay or bisexual cisgender men, were living with HIV, were unhoused, or used methamphetamines. Overall, rates of resistance to azithromycin, fluoroquinolones, ampicillin, and trimethoprim/sulfamethoxazole (TMP/SMX) were comparable to the most recent national data reported from the Centers for Disease Control and Prevention; 55% of isolates were resistant to azithromycin, 23% to fluoroquinolones, 70% to ampicillin, and 83% to TMP/SMX. The rates that we found for TMP/SMX were slightly higher than those in national data.Item Open Access Autochthonous ST405 NDM-5 producing Escherichia coli causing fatal sepsis in Northern Italy.(International journal of antimicrobial agents, 2020-05) Peri, Anna Maria; Piazza, Aurora; De Zan, Valentina; Carugati, Manuela; Muscatello, Antonio; Comandatore, Francesco; De Lorenzis, Elisa; Pluderi, Mauro; Arghittu, Milena; Cariani, Lisa; Cantù, Anna Paola; Bandi, Claudio; Cugno, Massimo; Gori, Andrea; Bandera, AlessandraItem Open Access Bloodstream infections in community hospitals in the 21st century: a multicenter cohort study.(PLoS One, 2014) Anderson, Deverick J; Moehring, Rebekah W; Sloane, Richard; Schmader, Kenneth E; Weber, David J; Fowler, Vance G; Smathers, Emily; Sexton, Daniel JBACKGROUND: While the majority of healthcare in the US is provided in community hospitals, the epidemiology and treatment of bloodstream infections in this setting is unknown. METHODS AND FINDINGS: We undertook this multicenter, retrospective cohort study to 1) describe the epidemiology of bloodstream infections (BSI) in a network of community hospitals and 2) determine risk factors for inappropriate therapy for bloodstream infections in community hospitals. 1,470 patients were identified as having a BSI in 9 community hospitals in the southeastern US from 2003 through 2006. The majority of BSIs were community-onset, healthcare associated (n = 823, 56%); 432 (29%) patients had community-acquired BSI, and 215 (15%) had hospital-onset, healthcare-associated BSI. BSIs due to multidrug-resistant pathogens occurred in 340 patients (23%). Overall, the three most common pathogens were S. aureus (n = 428, 28%), E. coli (n = 359, 24%), coagulase-negative Staphylococci (n = 148, 10%), though type of infecting organism varied by location of acquisition (e.g., community-acquired). Inappropriate empiric antimicrobial therapy was given to 542 (38%) patients. Proportions of inappropriate therapy varied by hospital (median = 33%, range 21-71%). Multivariate logistic regression identified the following factors independently associated with failure to receive appropriate empiric antimicrobial therapy: hospital where the patient received care (p<0.001), assistance with ≥3 ADLs (p = 0.005), Charlson score (p = 0.05), community-onset, healthcare-associated infection (p = 0.01), and hospital-onset, healthcare-associated infection (p = 0.02). Important interaction was observed between Charlson score and location of acquisition. CONCLUSIONS: Our large, multicenter study provides the most complete picture of BSIs in community hospitals in the US to date. The epidemiology of BSIs in community hospitals has changed: community-onset, healthcare-associated BSI is most common, S. aureus is the most common cause, and 1 of 3 patients with a BSI receives inappropriate empiric antimicrobial therapy. Our data suggest that appropriateness of empiric antimicrobial therapy is an important and needed performance metric for physicians and hospital stewardship programs in community hospitals.Item Open Access Cationic amphiphilic Zn-porphyrin with high antifungal photodynamic potency.(Photochemical & photobiological sciences : Official journal of the European Photochemistry Association and the European Society for Photobiology, 2017-11) Moghnie, Sara; Tovmasyan, Artak; Craik, James; Batinic-Haberle, Ines; Benov, LudmilPhotodynamic therapy (PDT) is a promising alternative approach particularly attractive for treatment of localized fungal infections. It is based on compounds, photosensitizers (PSs), which when excited with visible light, generate reactive species that ultimately cause cell death. Such species have short lifespans; as a consequence, efficiency and selectivity of the PDT treatment depend mainly on the properties of the PSs. This study is the first to explore the effect of cationic porphyrin-based photosensitizers on Saccharomyces cerevisiae, a member of the fungus kingdom. The study investigates which properties of the PS are essential for efficient antifungal PDT. Cationic Zn(ii) meso-tetrakis(N-alkylpyridinium-2-yl)porphyrins (ZnP) with identical tetrapyrrole core and photo-physical properties, but with different substituents at the meso positions of the porphyrin ring were studied. Attaching six-carbon aliphatic chains to the four pyridyl nitrogens at all meso positions to the porphyrin ring produced a highly photo-efficient amphiphilic, water soluble PS, with minimal dark toxicity. It was taken up by the yeast cells and upon illumination suppressed metabolism by inactivating cytoplasmic and mitochondrial enzymes, and compromising plasma membrane barrier function. At low concentrations (up to 5 μM) the tetrahexyl derivative was a much more powerful antifungal agent than the commercially available chlorin e6. The more lipophilic tetraoctyl analog was also highly photo-efficient but displayed strong dark toxicity, presumably due to higher lipophilicity which might affect the lipid bilayer of membranes. Results presented here can assist the design of antifungal agents whose biological action depends on efficient and rapid uptake by the cells.Item Open Access Characterization of the FKBP12-Encoding Genes in Aspergillus fumigatus.(PLoS One, 2015) Falloon, Katie; Juvvadi, Praveen R; Richards, Amber D; Vargas-Muñiz, José M; Renshaw, Hilary; Steinbach, William JInvasive aspergillosis, largely caused by Aspergillus fumigatus, is responsible for a growing number of deaths among immunosuppressed patients. Immunosuppressants such as FK506 (tacrolimus) that target calcineurin have shown promise for antifungal drug development. FK506-binding proteins (FKBPs) form a complex with calcineurin in the presence of FK506 (FKBP12-FK506) and inhibit calcineurin activity. Research on FKBPs in fungi is limited, and none of the FKBPs have been previously characterized in A. fumigatus. We identified four orthologous genes of FKBP12, the human FK506 binding partner, in A. fumigatus and designated them fkbp12-1, fkbp12-2, fkbp12-3, and fkbp12-4. Deletional analysis of the four genes revealed that the Δfkbp12-1 strain was resistant to FK506, indicating FKBP12-1 as the key mediator of FK506-binding to calcineurin. The endogenously expressed FKBP12-1-EGFP fusion protein localized to the cytoplasm and nuclei under normal growth conditions but also to the hyphal septa following FK506 treatment, revealing its interaction with calcineurin. The FKBP12-1-EGFP fusion protein didn't localize at the septa in the presence of FK506 in the cnaA deletion background, confirming its interaction with calcineurin. Testing of all deletion strains in the Galleria mellonella model of aspergillosis suggested that these proteins don't play an important role in virulence. While the Δfkbp12-2 and Δfkbp12-3 strains didn't show any discernable phenotype, the Δfkbp12-4 strain displayed slight growth defect under normal growth conditions and inhibition of the caspofungin-mediated "paradoxical growth effect" at higher concentrations of the antifungal caspofungin. Together, these results indicate that while only FKBP12-1 is the bona fide binding partner of FK506, leading to the inhibition of calcineurin in A. fumigatus, FKBP12-4 may play a role in basal growth and the caspofungin-mediated paradoxical growth response. Exploitation of differences between A. fumigatus FKBP12-1 and human FKBP12 will be critical for the generation of fungal-specific FK506 analogs to inhibit fungal calcineurin and treat invasive fungal disease.Item Open Access Contribution of urinary tract infection to the burden of febrile illnesses in young children in rural Kenya.(PLoS One, 2017) Masika, Wechuli Geoffrey; O'Meara, Wendy Prudhomme; Holland, Thomas L; Armstrong, JaniceINTRODUCTION: The clinical features of UTI in young children may not localize to the urinary tract and closely resemble other febrile illnesses. In malaria endemic areas, a child presenting with fever is often treated presumptively for malaria without investigation for UTI. Delayed or inadequate treatment of UTI increases the risk of bacteremia and renal scarring in young children and subsequently complications as hypertension and end stage renal disease in adulthood. METHODS: A cross-sectional study was carried out in a hospital in western Kenya. Inpatients and outpatients 2 months to five years with axillary temperature ≥37.5°C and no antibiotic use in the previous week were enrolled between September 2012 and April 2013. Urine dipstick tests, microscopy, and cultures were done and susceptibility patterns to commonly prescribed antibiotics established. UTI was defined as presence of pyuria (a positive urine dipstick or microscopy test) plus a positive urine culture. RESULTS: A total of 260 subjects were recruited; 45.8% were female and the median age was 25months (IQR: 13, 43.5). The overall prevalence of UTI was 11.9%. Inpatients had a higher prevalence compared to outpatients (17.9% v 7.8%, p = 0.027). UTI co-existed with malaria but the association was not significant (OR 0.80, p = 0.570). The most common organisms isolated were Escherichia coli (64.5%) and Staphylococcus aureus (12.9%) and were sensitive to ciproflaxin, cefuroxime, ceftriaxone, gentamycin and nitrofurantoin but largely resistant to more commonly used antibiotics such as ampicillin (0%), amoxicillin (16.7%), cotrimoxazole (16.7%) and amoxicillin-clavulinate (25%). CONCLUSION: Our study demonstrates UTI contributes significantly to the burden of febrile illness in young children and often co-exists with other infections. Multi-drug resistant organisms are common therefore choice of antimicrobial therapy should be based on local sensitivity pattern.Item Open Access Determination of plasma protein binding of dalbavancin.(The Journal of antimicrobial chemotherapy, 2022-06) Turner, Nicholas A; Xu, Allan; Zaharoff, Smitha; Holland, Thomas L; Lodise, Thomas PObjectives
Dalbavancin is a lipoglycopeptide with a long half-life, making it a promising treatment for infections requiring prolonged therapy, such as complicated Staphylococcus aureus bacteraemia. Free drug concentration is a critical consideration with prolonged treatment, since free concentration-time profiles may best correlate with therapeutic effect. In support of future clinical trials, we aimed to develop a reliable and reproducible assay for measuring free dalbavancin concentrations.Methods
The ultracentrifugation technique was used to determine free dalbavancin concentrations in plasma at two concentrations (50 and 200 mg/L) in duplicate. Centrifuge tubes and pipette tips were treated for 24 h before use with Tween 80 to assess adsorption. Dalbavancin concentrations were analysed from the plasma samples (total) and middle layer samples (free) by LC/MS/MS with isotopically labelled internal standard. Warfarin served as a positive control with known high protein binding.Results
Measurement of free dalbavancin was sensitive to adsorption onto plastic. Treatment of tubes and pipette tips with ≥2% Tween 80 effectively prevented drug loss during protein binding experiments. By the ultracentrifugation method, dalbavancin's protein binding was estimated to be approximately 99%.Conclusions
Dalbavancin has very high protein binding. Given dalbavancin's high protein binding, accurate measurement of free dalbavancin concentrations should be a key consideration in future exposure-response studies, especially clinical trials. Future investigations should confirm if the active fraction is best predicted by the free or total fraction.Item Open Access Do high MICs predict the outcome in invasive fusariosis?(The Journal of antimicrobial chemotherapy, 2021-03) Nucci, Marcio; Jenks, Jeffrey; Thompson, George R; Hoenigl, Martin; Dos Santos, Marielle Camargo; Forghieri, Fabio; Rico, Juan Carlos; Bonuomo, Valentina; López-Soria, Leyre; Lass-Flörl, Cornelia; Candoni, Anna; Garcia-Vidal, Carolina; Cattaneo, Chiara; Buil, Jochem; Rabagliati, Ricardo; Roiz, Maria Pia; Gudiol, Carlota; Fracchiolla, Nicola; Campos-Herrero, Maria Isolina; Delia, Mario; Farina, Francesca; Fortun, Jesus; Nadali, Gianpaolo; Sastre, Enric; Colombo, Arnaldo L; Pérez Nadales, Elena; Alastruey-Izquierdo, Ana; Pagano, LivioBackground
Invasive fusariosis (IF) affects mostly severely immunocompromised hosts and is associated with poor outcome. Since Fusarium species exhibit high MICs for most antifungal agents, this could explain the poor prognosis. However, a clear-cut correlation between MIC and outcome has not been established.Objective
To evaluate the correlation between MIC and outcome (6 week death rate) in patients with IF.Methods
We performed a multicentre retrospective study of patients with IF who received treatment and had MIC levels determined by EUCAST or CLSI for the drug(s) used during treatment. We compared the MIC50 and MIC distribution among survivors and patients who died within 6 weeks from the diagnosis of IF.Results
Among 88 patients with IF, 74 had haematological diseases. Primary treatment was monotherapy in 52 patients (voriconazole in 27) and combination therapy in 36 patients (liposomal amphotericin B + voriconazole in 23). The MIC50 and range for the five most frequent agents tested were: voriconazole 8 mg/L (range 0.5-64), amphotericin B 2 mg/L (range 0.25-64), posaconazole 16 mg/L (range 0.5-64), itraconazole 32 mg/L (range 4-64), and isavuconazole 32 mg/L (range 8-64). There was no difference in MIC50 and MIC distribution among survivors and patients who died. By contrast, persistent neutropenia and receipt of corticosteroids were strong predictors of 6 week mortality.Conclusions
Our study did not show any correlation between MIC and mortality at 6 weeks in patients with IF.Item Open Access Drug design from the cryptic inhibitor envelope.(Nat Commun, 2016-02-25) Lee, Chul-Jin; Liang, Xiaofei; Wu, Qinglin; Najeeb, Javaria; Zhao, Jinshi; Gopalaswamy, Ramesh; Titecat, Marie; Sebbane, Florent; Lemaitre, Nadine; Toone, Eric J; Zhou, PeiConformational dynamics plays an important role in enzyme catalysis, allosteric regulation of protein functions and assembly of macromolecular complexes. Despite these well-established roles, such information has yet to be exploited for drug design. Here we show by nuclear magnetic resonance spectroscopy that inhibitors of LpxC--an essential enzyme of the lipid A biosynthetic pathway in Gram-negative bacteria and a validated novel antibiotic target--access alternative, minor population states in solution in addition to the ligand conformation observed in crystal structures. These conformations collectively delineate an inhibitor envelope that is invisible to crystallography, but is dynamically accessible by small molecules in solution. Drug design exploiting such a hidden inhibitor envelope has led to the development of potent antibiotics with inhibition constants in the single-digit picomolar range. The principle of the cryptic inhibitor envelope approach may be broadly applicable to other lead optimization campaigns to yield improved therapeutics.Item Open Access Etiologies of illness among patients meeting integrated management of adolescent and adult illness district clinician manual criteria for severe infections in northern Tanzania: implications for empiric antimicrobial therapy.(Am J Trop Med Hyg, 2015-02) Rubach, Matthew P; Maro, Venance P; Bartlett, John A; Crump, John AWe describe the laboratory-confirmed etiologies of illness among participants in a hospital-based febrile illness cohort study in northern Tanzania who retrospectively met Integrated Management of Adolescent and Adult Illness District Clinician Manual (IMAI) criteria for septic shock, severe respiratory distress without shock, and severe pneumonia, and compare these etiologies against commonly used antimicrobials, including IMAI recommendations for emergency antibacterials (ceftriaxone or ampicillin plus gentamicin) and IMAI first-line recommendations for severe pneumonia (ceftriaxone and a macrolide). Among 423 participants hospitalized with febrile illness, there were 25 septic shock, 37 severe respiratory distress without shock, and 109 severe pneumonia cases. Ceftriaxone had the highest potential utility of all antimicrobials assessed, with responsive etiologies in 12 (48%) septic shock, 5 (14%) severe respiratory distress without shock, and 19 (17%) severe pneumonia illnesses. For each syndrome 17-27% of participants had etiologic diagnoses that would be non-responsive to ceftriaxone, but responsive to other available antimicrobial regimens including amphotericin for cryptococcosis and histoplasmosis; anti-tuberculosis therapy for bacteremic disseminated tuberculosis; or tetracycline therapy for rickettsioses and Q fever. We conclude that although empiric ceftriaxone is appropriate in our setting, etiologies not explicitly addressed in IMAI guidance for these syndromes, such as cryptococcosis, histoplasmosis, and tetracycline-responsive bacterial infections, were common.Item Open Access Influence of vancomycin minimum inhibitory concentration on the outcome of methicillin-susceptible Staphylococcus aureus left-sided infective endocarditis treated with antistaphylococcal β-lactam antibiotics: a prospective cohort study by the International Collaboration on Endocarditis.(Clinical microbiology and infection : the official publication of the European Society of Clinical Microbiology and Infectious Diseases, 2017-08) Pericàs, JM; Messina, JA; Garcia-de-la-Mària, C; Park, L; Sharma-Kuinkel, BK; Marco, F; Wray, D; Kanafani, ZA; Carugati, M; Durante-Mangoni, E; Tattevin, P; Chu, VH; Moreno, A; Fowler, VG; Miró, JM; International Collaboration on Endocarditis Microbiology InvestigatorsObjectives
Left-sided methicillin-susceptible Staphylococcus aureus (MSSA) endocarditis treated with cloxacillin has a poorer prognosis when the vancomycin minimum inhibitory concentration (MIC) is ≥1.5 mg/L. We aimed to validate this using the International Collaboration on Endocarditis cohort and to analyse whether specific genetic characteristics were associated with a high vancomycin MIC (≥1.5 mg/L) phenotype.Methods
All patients with left-sided MSSA infective endocarditis treated with antistaphylococcal β-lactam antibiotics between 2000 and 2006 with available isolates were included. Vancomycin MIC was determined by Etest as either high (≥1.5 mg/L) or low (<1.5 mg/L). Isolates underwent spa typing to infer clonal complexes and multiplex PCR for identifying virulence genes. Univariate analysis was performed to evaluate the association between in-hospital and 1-year mortality, and vancomycin MIC phenotype.Results
Sixty-two cases met the inclusion criteria. Vancomycin MIC was low in 28 cases (45%) and high in 34 cases (55%). No significant differences in patient demographic data or characteristics of infection were observed between patients with infective endocarditis due to high and low vancomycin MIC isolates. Isolates with high and low vancomycin MIC had similar distributions of virulence genes and clonal lineages. In-hospital and 1-year mortality did not differ significantly between the two groups (32% (9/28) vs. 27% (9/34), p 0.780; and 43% (12/28) vs. 29% (10/34), p 0.298, for low and high vancomycin MIC respectively).Conclusions
In this international cohort of patients with left-sided MSSA endocarditis treated with antistaphylococcal β-lactams, vancomycin MIC phenotype was not associated with patient demographics, clinical outcome or virulence gene repertoire.Item Open Access Isolation, speciation and antifungal susceptibility testing of Candida isolates from various clinical specimens at a tertiary care hospital, Nepal.(BMC research notes, 2017-06) Khadka, Sundar; Sherchand, Jeevan Bahadur; Pokhrel, Bharat Mani; Parajuli, Keshab; Mishra, Shyam Kumar; Sharma, Sangita; Shah, Niranjan; Kattel, Hari Prasad; Dhital, Subhash; Khatiwada, Sulochana; Parajuli, Narayan; Pradhan, Manoj; Rijal, Basista PrasadBackground
Candida species are responsible for various clinical infections ranging from mucocutaneous infection to life threatening invasive diseases along with increased resistance to antifungal drugs has made a serious concern. Resistance to antifungal agents has increased during the last decade. Thus, identification of Candida up to species level and its antifungal susceptibility testing has a paramount significance in the management of Candidal infections. The aim of the study was to speciate Candida species and to determine antifungal susceptibility pattern of Candida species to antifungal agents.Methods
A total of 100 consecutive Candida species were isolated from 1248 clinical specimens over 7 months period. Growths on Sabouraud dextrose agar were evaluated for colony appearance, macroscopic examination, Gram staining, germ tube test and urea hydrolysis test. Further, they were processed for Candida speciation on CHROMagar. Antifungal susceptibility testing was performed as recommended by Clinical and Laboratory Standards Institute (CLSI) M44-A document.Results
Out of 100 Candida isolates, Candida albicans (56%) was the most common species. Among the non-albicans Candida species, Candida tropicalis (20%) was the predominant isolate followed by Candida glabrata (14%). Regarding antifungal susceptibility pattern, Candida species were more susceptible to clotrimazole (82%) followed by fluconazole (64%) and miconazole (44%).Conclusions
Candida albicans was the predominant species responsible for various Candidal infections. Among commonly used antifungal drugs clotrimazole, miconazole and fluconazole were most effective.Item Open Access Microbial inactivation of Pseudomonas putida and Pichia pastoris using gene silencing.(Environ Sci Technol, 2010-05-01) Morse, Thomas O; Morey, Sara J; Gunsch, Claudia KAntisense deoxyoligonucleotide (ASO) gene silencing was investigated as a potential disinfection tool for industrial and drinking water treatment application. ASOs bind with their reverse complementary mRNA transcripts thereby blocking protein translation. While ASO silencing has mainly been studied in medicine, it may be useful for modulating gene expression and inactivating microorganisms in environmental applications. In this proof of concept work, gene targets were sh ble (zeocin resistance) and todE (catechol-2,3-dioxygenase) in Pichia pastoris and npt (kanamycin resistance) in Pseudomonas putida. A maximum 0.5-fold decrease in P. pastoris cell numbers was obtained following a 120 min incubation with single-stranded DNA (ssDNA) concentrations ranging from 0.2 to 200 nM as compared to the no ssDNA control. In P. putida, a maximum 5.2-fold decrease was obtained after 90 min with 400 nM ssDNA. While the silencing efficiencies varied for the 25 targets tested, these results suggest that protein activity as well as microbial growth can be altered using ASO gene silencing-based tools. If successful, this technology has the potential to eliminate some of the environmental and health issues associated with the use of strong chemical biocides. However, prior to its dissemination, more research is needed to increase silencing efficiency and develop effective delivery methods.Item Open Access Pediatric-specific antimicrobial susceptibility data and empiric antibiotic selection.(Pediatrics, 2012-09) Boggan, JC; Navar-Boggan, AM; Jhaveri, ROBJECTIVE: Duke University Health System (DUHS) generates annual antibiograms combining adult and pediatric data. We hypothesized significant susceptibility differences exist for pediatric isolates and that distributing these results would alter antibiotic choices. METHODS: Susceptibility rates for Escherichia coli isolates from patients aged ≤12 years between July 2009 and September 2010 were compared with the 2009 DUHS antibiogram. Pediatric attending and resident physicians answered case-based vignettes about children aged 3 months and 12 years with urinary tract infections. Each vignette contained 3 identical scenarios with no antibiogram, the 2009 DUHS antibiogram, and a pediatric-specific antibiogram provided. Effective antibiotics exhibited >80% in vitro susceptibility. Frequency of antibiotic selection was analyzed by using descriptive statistics. RESULTS: Three hundred seventy-five pediatric isolates were identified. Pediatric isolates were more resistant to ampicillin and trimethoprim-sulfamethoxazole (TMP-SMX) and less resistant to amoxicillin-clavulanate and ciprofloxacin (P < .0005 for all). Seventy-five resident and attending physicians completed surveys. In infant vignettes, physicians selected amoxicillin-clavulanate (P < .05) and nitrofurantoin (P < .01) more often and TMP-SMX (P < .01) less often with pediatric-specific data. Effective antibiotic choices increased from 68.6% to 82.2% (P = .06) to 92.5% (P < .01) across scenarios. In adolescent vignettes, providers reduced TMP-SMX use from 66.2% to 42.6% to 19.0% (P < .01 for both). Effective antibiotic choices increased from 32.4% to 57.4% to 79.4% (P < .01 and P = .01). CONCLUSIONS: Pediatric E. coli isolates differ significantly in antimicrobial susceptibility at our institution, particularly to frequently administered oral antibiotics. Knowledge of pediatric-specific data altered empirical antibiotic choices in case vignettes. Care of pediatric patients could be improved with use of a pediatric-specific antibiogram.Item Open Access PKC signaling regulates drug resistance of the fungal pathogen Candida albicans via circuitry comprised of Mkc1, calcineurin, and Hsp90.(PLoS Pathog, 2010-08-26) LaFayette, Shantelle L; Collins, Cathy; Zaas, Aimee K; Schell, Wiley A; Betancourt-Quiroz, Marisol; Gunatilaka, AA Leslie; Perfect, John R; Cowen, Leah EFungal pathogens exploit diverse mechanisms to survive exposure to antifungal drugs. This poses concern given the limited number of clinically useful antifungals and the growing population of immunocompromised individuals vulnerable to life-threatening fungal infection. To identify molecules that abrogate resistance to the most widely deployed class of antifungals, the azoles, we conducted a screen of 1,280 pharmacologically active compounds. Three out of seven hits that abolished azole resistance of a resistant mutant of the model yeast Saccharomyces cerevisiae and a clinical isolate of the leading human fungal pathogen Candida albicans were inhibitors of protein kinase C (PKC), which regulates cell wall integrity during growth, morphogenesis, and response to cell wall stress. Pharmacological or genetic impairment of Pkc1 conferred hypersensitivity to multiple drugs that target synthesis of the key cell membrane sterol ergosterol, including azoles, allylamines, and morpholines. Pkc1 enabled survival of cell membrane stress at least in part via the mitogen activated protein kinase (MAPK) cascade in both species, though through distinct downstream effectors. Strikingly, inhibition of Pkc1 phenocopied inhibition of the molecular chaperone Hsp90 or its client protein calcineurin. PKC signaling was required for calcineurin activation in response to drug exposure in S. cerevisiae. In contrast, Pkc1 and calcineurin independently regulate drug resistance via a common target in C. albicans. We identified an additional level of regulatory control in the C. albicans circuitry linking PKC signaling, Hsp90, and calcineurin as genetic reduction of Hsp90 led to depletion of the terminal MAPK, Mkc1. Deletion of C. albicans PKC1 rendered fungistatic ergosterol biosynthesis inhibitors fungicidal and attenuated virulence in a murine model of systemic candidiasis. This work establishes a new role for PKC signaling in drug resistance, novel circuitry through which Hsp90 regulates drug resistance, and that targeting stress response signaling provides a promising strategy for treating life-threatening fungal infections.Item Open Access Rare mould infections caused by Mucorales, Lomentospora prolificans and Fusarium, in San Diego, CA: the role of antifungal combination therapy.(International journal of antimicrobial agents, 2018-11) Jenks, Jeffrey D; Reed, Sharon L; Seidel, Danila; Koehler, Philipp; Cornely, Oliver A; Mehta, Sanjay R; Hoenigl, MartinNon-Aspergillus invasive mould infections (IMIs) are associated with devastating morbidity and mortality rates and are increasingly diagnosed in immunocompromised hosts. The aim of this study was to describe the epidemiology and outcomes of non-Aspergillus IMIs at a university hospital in San Diego, California, USA. A retrospective chart review of the medical records of all patients with cultures growing non-Aspergillus moulds at the microbiology laboratory in the Center for Academic Laboratory Medicine, Department of Pathology, University of California, San Diego (UCSD) Health between mid-2014 and mid-2017 (3-year period) was performed. A total of 23 cases of non-Aspergillus IMI were identified, including 10 cases of mucormycosis, 8 cases of lomentosporiosis and 5 cases of fusariosis. Antifungal susceptibility testing was performed for 14 isolates, and 10/11 Fusarium and Lomentospora isolates had minimum inhibitory concentrations (MICs) of >16 µg/mL for voriconazole and/or posaconazole. Overall 180-day mortality was significantly lower among those who received combination antifungal therapy than among those who received single-agent therapy [3/13 (23%) vs. 9/10 (90%); P = 0.003]. In conclusion, Lomentospora prolificans (35% of non-Aspergillus IMIs) and Fusarium spp. (22%) accounted for high proportions of non-Aspergillus IMIs during the study period. Non-Aspergillus IMIs were detected in patients with various underlying diseases and were associated with high mortality rates, which was significantly lower in those who received antifungal combination therapy.Item Open Access The inoculum effect and band-pass bacterial response to periodic antibiotic treatment.(Mol Syst Biol, 2012) Tan, Cheemeng; Smith, Robert Phillip; Srimani, Jaydeep K; Riccione, Katherine A; Prasada, Sameer; Kuehn, Meta; You, LingchongThe inoculum effect (IE) refers to the decreasing efficacy of an antibiotic with increasing bacterial density. It represents a unique strategy of antibiotic tolerance and it can complicate design of effective antibiotic treatment of bacterial infections. To gain insight into this phenomenon, we have analyzed responses of a lab strain of Escherichia coli to antibiotics that target the ribosome. We show that the IE can be explained by bistable inhibition of bacterial growth. A critical requirement for this bistability is sufficiently fast degradation of ribosomes, which can result from antibiotic-induced heat-shock response. Furthermore, antibiotics that elicit the IE can lead to 'band-pass' response of bacterial growth to periodic antibiotic treatment: the treatment efficacy drastically diminishes at intermediate frequencies of treatment. Our proposed mechanism for the IE may be generally applicable to other bacterial species treated with antibiotics targeting the ribosomes.Item Open Access Voriconazole plus terbinafine combination antifungal therapy for invasive Lomentospora prolificans infections: analysis of 41 patients from the FungiScope® registry 2008-2019.(Clinical microbiology and infection : the official publication of the European Society of Clinical Microbiology and Infectious Diseases, 2020-06) Jenks, JD; Seidel, D; Cornely, OA; Chen, S; van Hal, S; Kauffman, C; Miceli, MH; Heinemann, M; Christner, M; Jover Sáenz, A; Burchardt, A; Kemmerling, B; Herbrecht, R; Steinmann, J; Shoham, S; Gräber, S; Pagano, L; Deeren, D; Aslam, S; Taplitz, R; Revankar, SG; Baddley, J; Mehta, SR; Reed, S; Slavin, MA; Hoenigl, MObjectives
Lomentospora prolificans is an emerging cause of serious invasive fungal infections. Optimal treatment of these infections is unknown, although voriconazole-containing treatment regimens are considered the treatment of choice. The objective of this study was to evaluate the role of combination antifungal therapy for L. prolificans infections.Methods
We performed a retrospective review of medical records of patients with invasive L. prolificans infection diagnosed between 1 January 2008 and 9 September 2019 that were documented in the FungiScope® registry of rare invasive fungal infections. We compared clinical outcomes between antifungal treatment strategies.Results
Over the study period, 41 individuals with invasive L. prolificans infection from eight different countries were documented in the FungiScope® registry. Overall, 17/40 (43%) had treatment response/stable disease and 21/40 (53%) had a fatal outcome attributed to invasive fungal infection. Combination antifungal therapy was associated with increased 28-day survival (15/24 survived versus 4/16 receiving monotherapy; p 0.027) and the combination voriconazole plus terbinafine trended to be associated with higher rates of treatment success (10/16, 63%, 95% CI 35%-85%) compared with other antifungal treatment regimens (7/24, 29%, 95% CI 13%-51%, p 0.053). In Kaplan-Meier survival analysis there was a higher survival probability in individuals receiving the voriconazole/terbinafine combination compared with other antifungal regimens (median survival 150 days versus 17 days).Conclusions
While overall mortality was high, combination antifungal treatment, and in particular combination therapy with voriconazole plus terbinafine may be associated with improved treatment outcomes compared with other antifungal regimens for the treatment of invasive L. prolificans infections.