Elevated Minimum Inhibitory Concentrations Research Articles

Molecular types of Cryptococcus neoformans and Cryptococcus gattii in Western Australia and correlation with antifungal susceptibility

Cryptococcus neoformans and Cryptococcus gattii species complexes have a worldwide distribution; however, there is geographical variation in the prevalence of different molecular types. Additionally, antifungal susceptibility differences between molecular types have been demonstrated. This study investigates the distribution of cryptococcal molecular types among human clinical isolates over a 10-year period from a Western Australian population. Molecular type was determined based on polymorphisms in the phospholipase gene locus identified through amplification and sequencing. Minimum inhibitory concentrations (MICs) were identified for fluconazole, 5-fluorocytosine, posaconazole, itraconazole, voriconazole, and amphotericin B. Most isolates were C. neoformans complex (42) of which over half were molecular type VNI (22) followed by VNII (20). Among the remaining C. gattii complex (13) the majority were VGI (11) with VGII (2) uncommonly found. All isolates demonstrated low MICs to antifungal agents including fluconazole. Geometric mean MIC values against 5-fluorocytosine for VNI (1.741mg/l) were significantly higher than those for VGI (0.47mg/l, P = .002). Similarly fluconazole geometric mean MICs against fluconazole for VNI (2.3mg/l) were significantly higher than VNII (0.87mg/l, P = .036). These data reveal the presence of four molecular types (VNI, VNII, VGI and VGII) within clinical Western Australian cryptococcal isolates and, while elevated antifungal MICs were not encountered, significant molecular type dependent differences in susceptibility were found.

Natural products show diverse mechanisms of action against Clostridium difficile.

To investigate the mechanisms of action of natural products with bactericidal (cinnamon root powder, peppermint oil, trans-cinnamaldehyde, menthol and zingerone) or bacteriostatic (fresh garlic bulb extract, garlic clove powder, Leptospermum honey and allicin) activity against two Clostridium difficile strains. Bactericidal products significantly reduced intracellular ATP after 1h (P≤0·01), quantified using the BacTiter-Glo reagent, and damaged the cell membrane, shown by the leakage of both 260-nm-absorbing materials and protein, and the uptake of propidium iodide. Bacteriolysis was not observed, determined by measuring optical density of treated cell suspensions at 620-nm. The effect of three bacteriostatic products on protein synthesis was quantified using an Escherichia coli S30 extract system, with Leptospermum honey (16% w/v) showing significant inhibition (P<0·01). Lastly, no products showed elevated minimum inhibitory concentrations against antimicrobial-resistant C. difficile, determined by broth microdilution. Cytoplasmic membrane damage was identified as a mechanism of action that may contribute to the activity of several natural products against C. difficile. This study describes the possible mechanisms of action of natural products against C. difficile, yet the efficacy invivo to be determined.

125. eGISP: Enhanced Surveillance of Neisseria gonorrhoeae Antimicrobial Susceptibility in the United States

BackgroundThe Gonococcal Isolate Surveillance Project (GISP), which monitors trends in N. gonorrhoeae susceptibility among men with gonococcal urethritis in sexually transmitted disease (STD) clinics, has informed treatment recommendations for 3 decades. However, it has been speculated that susceptibility patterns may differ in women, as well as in the pharynx and rectum. We describe preliminary findings from the enhanced GISP (eGISP), which expands surveillance to pharyngeal, rectal, and endocervical isolates.MethodsIn August 2017, select jurisdictions were funded to collect urogenital and extragenital specimens from men and women seen in participating STD clinics. Positive gonorrhea cultures were sent to regional laboratories for antimicrobial susceptibility testing (AST) by agar dilution. Isolates with elevated minimum inhibitory concentration (MIC) to azithromycin (AZI) (MIC ≥2.0 μg/mL), cefixime (CFX) (MIC ≥0.25 μg/mL), and/or ceftriaxone (CRO) (MIC ≥0.125 μg/mL) were designated as Alert isolates. Clinical and epidemiological data were linked to AST results.ResultsFrom August 2017 to February 2018, 4 clinics in 4 jurisdictions submitted 468 positive gonococcal specimens for AST; 36.1% were from men who have sex with men (MSM), 51.9% from men who have sex with women (MSW), and 12.0% from women. Overall, 71.8% were urethral, 7.9% endocervical, 7.1% rectal, and 13.2% pharyngeal. Seventy-two isolates (15.4%) were Alerts: 97.2% (N = 70) had elevated MICs to AZI, 2.8% (N = 2) had elevated MICs to CFX, and none had elevated MICs to CRO. No isolate had elevated MICs to both AZI and CFX. Among MSM, 15.9% of urogenital isolates and 16.1% of extragenital isolates had an elevated AZI MIC. Among MSW, 11.8% of urogenital isolates and 14.3% of pharyngeal isolates had an elevated AZI MIC. Among women, 24.3% of endocervical isolates and 26.3% of extragenital isolates had an elevated AZI MIC.ConclusionPreliminary eGISP data suggest that enhanced surveillance of pharyngeal, rectal, and endocervical isolates is feasible and that elevated MICs to azithromycin are common among males and females. Including isolates from extragenital anatomic sites and women may help strengthen N. gonorrhoeae surveillance capacity.Disclosures All authors: No reported disclosures.

1167. Trends in Multi-Drug-Resistant Gonorrhea, Gonococcal Isolate Surveillance Project, United States, 1987–2016

Background Neisseria gonorrhoeae’s ability to develop resistance to antibiotics used for treatment and a limited development of new therapies have made this organism one of three urgent threat pathogens in the United States. We provide the first report of US trends in multi-drug-resistant (MDR) and extensively-drug-resistant (XDR) gonorrhea.MethodsThe Gonococcal Isolate Surveillance Project (GISP) monitors trends in antimicrobial susceptibility in N. gonorrhoeae in the United States. Antimicrobial susceptibility testing by agar dilution is performed on urethral isolates from male patients at participating STD clinics. Minimum inhibitory concentration (MIC) are used to identify isolates with resistance or reduced susceptibility using the following criteria: fluoroquinolones (ciprofloxacin [MIC ≥1.0 μg/mL]) and elevated MICs to cephalosporins (cefixime [MIC ≥0.25 μg/mL], ceftriaxone [MIC ≥0.25 μg/mL]) and macrolides (azithromycin [MIC ≥1.0 μg/mL before 2005 and ≥2.0 μg/mL 2005–2016]). In this analysis, MDR is defined as resistance or elevated MICs to ≥2 classes of antimicrobials; XDR as resistance or elevated MICs to ≥3 classes. This classification excludes penicillin and tetracycline due to their long history and high prevalence of gonococcal resistance.ResultsDuring 1987–2016, 159,445 isolates were collected through GISP. In 1998, the first MDR strains were identified. Although only 0.04% of isolates that year, these isolates showed elevated MICs to both cephalosporins and macrolides. By 2010, 1.0% of GISP isolates were MDR with elevated MICs or resistance to two of the cephalosporins, macrolides, or fluoroquinolones. In 2011, the proportion of isolates that were MDR peaked at 1.3%. In 2016, after minor fluctuations, 1.1% of GISP isolates were considered MDR. Only one occurrence of XDR, in 2011, has been seen in GISP. The strain was resistant to fluoroquinolones with elevated MICs to both cephalosporins and macrolides.ConclusionMDR and XDR gonorrhea have remained low over the past three decades; however, dual treatment with cephalosporins and macrolides is the last remaining recommended therapy for N. gonorrhoeae. Until new treatment options become available, a combination of surveillance and ensuring appropriate treatment are needed to delay further resistance.Disclosures All authors: No reported disclosures.

2432. Appropriateness of Empiric Extended-Infusion Piperacillin/Tazobactam in the Intensive Care Unit

BackgroundGram-negative (GN) infections in ICU patients have increased antibiotic resistance owing to higher minimum inhibitory concentrations (MICs). Piperacillin/tazobactam (PTZ) 3.375 g extended infusion (EI) may be used as an empiric agent. GN organisms with PTZ MICs > 16/4 may not be adequately covered by this regimen. The objective of this study was to evaluate MICs of GN isolates from the ICU to determine whether PTZ 3.375 g EI is an appropriate empiric regimen for ICU patients. Appropriateness of empiric antibiotic therapy was defined as PTZ MIC ≤16/4 in greater than 80% of isolates. The secondary objective was to evaluate patient specific risk factors that may be associated with elevated PTZ MICs in GN pathogens.MethodsAll ICU patients admitted from January to December 2017 with a confirmed GN pathogen from a non-urinary source were included. Patients were excluded if they had cystic fibrosis, cultures obtained >48 hours prior to ICU admission, or they were incarcerated. Patients’ electronic medical records were reviewed for the following data: age, sex, ethnicity, location prior to ICU admission, GN pathogen, culture source, risk factors for multi-drug-resistant organisms (dialysis, injection drug use, indwelling catheter, wounds/trauma), pathogen susceptibility profile, risk modifying co-morbidities (diabetes, heart failure, chronic kidney disease, and liver disease) and creatinine clearance.Results231 patients were included in the study. The average patient was 56.7 years old ±16.95. The majority of patients were white (64.1%) and male (69.7%). There were no significant differences in baseline characteristics between patients with PTZ MICs >16/4 and those with MICs ≤16/4. Pseudomonas aeruginosa (41%) was the primary organism identified and 28% of all GN isolates had MICs >16/4. Dialysis (P = 0.028), IV antibiotics (P < 0.001) and presence of wounds or trauma (P = 0.018) were all associated with elevated MICs.ConclusionCurrent PTZ EI 3.375g dosing may not provide adequate empiric coverage of GN pathogens for ICU patients especially for patients who received previous IV antibiotics, are on dialysis, or have the presence of wounds or trauma.Disclosures All authors: No reported disclosures.

MIXED NON-ALBICANS CANDIDA FUNGEMIA: AN UNCOMMON BUT EASILY OVERLOOKED CLINICAL ENTITY

The increasing use of invasive medical devices and broad-spectrum antimicrobial agents has resulted in rising candidemia rates throughout the world. A 70-year-old diabetic and schizophrenic woman was admitted initially for staphylococcal sepsis secondary to an infected sacral sore but developed a catheter-related bloodstream infection caused by extended-spectrum β-lactamase-producing Klebsiella sp. which necessitated the administration of meropenem. Unfortunately, after a week on the carbapenem, the bacterial sepsis was followed by candidemia. Parenteral fluconazole therapy was started pending identification of the yeast(s). Two distinct Candida species were isolated from her blood which were identified biochemically using ID 32 C as Candida tropicalis and Candida lipolytica. Both yeasts possessed elevated minimal inhibitory concentrations toward fluconazole and although amphotericin B was eventually administered, the patient succumbed to her illness.

In vitro activity of cefiderocol, a siderophore cephalosporin, against a recent collection of clinically relevant carbapenem-non-susceptible Gram-negative bacilli, including serine carbapenemase- and metallo-β-lactamase-producing isolates (SIDERO-WT-2014 Study)

Cefiderocol is a siderophore cephalosporin in development for treatment of infections caused by Gram-negative bacilli, including carbapenem-resistant and multidrug-resistant isolates. β-Lactamase carriage and in vitro activity of cefiderocol were determined against 1272 meropenem-non-susceptible isolates of Enterobacteriaceae, Pseudomonas aeruginosa and Acinetobacter baumannii collected as part of the SIDERO-WT-2014 surveillance study. Minimum inhibitory concentration (MIC) values for cefiderocol were ≤4 µg/mL against 97.7% of tested isolates, including 100% of IMP-positive (range, 1-2 µg/mL), OXA-58-positive (MIC90, 1 µg/mL), KPC-positive (MIC90, 2 µg/mL), VIM-positive (MIC90, 2 µg/mL), and OXA-48-like-positive (MIC90, 4 µg/mL) isolates; 99.3% of carbapenemase-negative isolates (MIC90, 1 µg/mL); 97.2% of OXA-23-positive isolates (MIC90, 1 µg/mL); 95.2% of OXA-24-positive isolates (MIC90, 1 µg/mL); 91.7% of GES-positive isolates (MIC90, 4 µg/mL); and 64.3% of NDM-positive isolates (MIC90, 8 µg/mL). A total of 29 isolates (2.3%; 15 OXA-23-producers, 6 OXA-24-producers, 5 NDM-producers, and 3 carbapenemase-negative isolates) exhibited cefiderocol MIC ≥8 µg/mL, confirming there was no clear correlation between carriage of β-lactamases included in the molecular testing algorithm and elevated cefiderocol MICs. Similarly, no correlation was observed between cefiderocol MICs and truncation or loss of porin proteins in meropenem-non-susceptible isolates of E. coli and K. pneumoniae. Cefiderocol MICs were also ≤4 µg/mL against 99.3% of 136 colistin-resistant Enterobacteriaceae collected as part of the SIDERO-WT-2014 study, including isolates carrying mcr-1 (MIC90, 2 µg/mL). Cefiderocol demonstrated potent in vitro activity against a collection of carbapenemase-producing and carbapenemase-negative meropenem-non-susceptible Gram-negative bacilli for which few treatment options are available, including the majority of metallo-β-lactamase producing isolates identified.

Distribution of the pco Gene Cluster and Associated Genetic Determinants among Swine Escherichia coli from a Controlled Feeding Trial.

Copper is used as an alternative to antibiotics for growth promotion and disease prevention. However, bacteria developed tolerance mechanisms for elevated copper concentrations, including those encoded by the pco operon in Gram-negative bacteria. Using cohorts of weaned piglets, this study showed that the supplementation of feed with copper concentrations as used in the field did not result in a significant short-term increase in the proportion of pco-positive fecal Escherichia coli. The pco and sil (silver resistance) operons were found concurrently in all screened isolates, and whole-genome sequencing showed that they were distributed among a diversity of unrelated E. coli strains. The presence of pco/sil in E. coli was not associated with elevated copper minimal inhibitory concentrations (MICs) under a variety of conditions. As found in previous studies, the pco/sil operons were part of a Tn7-like structure found both on the chromosome or on plasmids in the E. coli strains investigated. Transfer of a pco/sil IncHI2 plasmid from E. coli to Salmonella enterica resulted in elevated copper MICs in the latter. Escherichia coli may represent a reservoir of pco/sil genes transferable to other organisms such as S. enterica, for which it may represent an advantage in the presence of copper. This, in turn, has the potential for co-selection of resistance to antibiotics.

Epidemiology of Aspergillus species causing keratitis in Mexico.

The incidence of fungal keratitis has increased in recent years. While the epidemiology and clinical roles of various Candida and Fusarium species have been relatively well-identified in infections of the eye, data regarding keratitis caused by Aspergillus species are scant. Accurate and rapid diagnosis is important for successful management of this infection. To present the first molecular epidemiological data from Mexico during a 4-year period of cases admitted with Aspergillus keratitis to a tertiary care eye institution in Mexico City. A total of 25 cases of keratitis were included in the study. Aspergillus isolates were identified by sequencing the calmodulin gene. Antifungal susceptibility was tested according to CLSI. The aetiological agents belonged to Aspergillus flavus (n=13), Aspergillus effusus (n=1), Aspergillus tamarii (n=4), Aspergillus sydowii (n=1), Aspergillus protuberus (n=3) and Aspergillus terreus (n=3). All strains had low minimum inhibitory concentrations (MICs) of itraconazole and voriconazole (VCZ). Amphotericin B and natamycin showed moderate elevated MICs. Early diagnosis and application of topical VCZ 1% were associated with good outcome. Monitoring of local epidemiological data plays an important role in clinical practice.

Synergistic and bactericidal activities of mecillinam, amoxicillin and clavulanic acid combinations against extended-spectrum β-lactamase (ESBL)-producing Escherichia coli in 24-h time–kill experiments

This study aimed to evaluate the potential synergistic and bactericidal effects of mecillinam in combination with amoxicillin and clavulanic acid against extended-spectrum β-lactamase (ESBL)-producing Escherichia coli. Eight clinical E. coli isolates with varying susceptibility to mecillinam [minimum inhibitory concentrations (MICs) of 0.125 mg/L to >256 mg/L] and high-level resistance to amoxicillin (MICs > 256 mg/L) were used. Whole-genome sequencing was performed to determine the presence of β-lactamase genes and mutations in the cysB gene. The activities of single drugs and the combinations of two or three drugs were tested in 24-h time-kill experiments. Population analysis was performed for two strains before and after experiments. Only one strain had a mutation in the cysB gene resulting in an amino acid substitution. With the two-drug combinations, initial killing was observed both with mecillinam and amoxicillin when combined with clavulanic acid. Synergy was observed with mecillinam and clavulanic acid against one strain and with amoxicillin and clavulanic acid against three strains. However, following significant re-growth, a bactericidal effect was found only with amoxicillin and clavulanic acid against two strains. Pre-existing subpopulations with elevated mecillinam MICs were detected before experiments and were selected with mecillinam alone or in two-drug combinations. In contrast, the three-drug combination showed enhanced activity with synergy against six strains, a bactericidal effect against all eight strains, and suppression of resistance during 24-h antibiotic exposure. This combination may be of clinical interest in the treatment of urinary tract infections caused by ESBL-producing E. coli.

Plasmid-Mediated AmpC β-Lactamase and Underestimation of Extended-Spectrum β-Lactamase in Cefepime-Susceptible Elevated-Ceftazidime-MIC Enterobacteriaceae Isolates.

Phenotypic detection of extended-spectrum β-lactamase (ESBL) is important for public health and infection control; however, plasmid-mediated AmpC β-lactamases (pAmpCs) can interfere with the ESBL phenotyping. We focused on Enterobacteriaceae strains that were susceptible to cefepime but had a mildly elevated minimum inhibitory concentration (MIC) of ceftazidime and studied the effect of pAmpC on the ESBL phenotyping in this population. Genotyping of ESBL and pAmpC was performed on 528 clinical isolates of Escherichia coli, Klebsiella spp., and Proteus spp. with a ceftazidime MIC of ≥2 μg/mL and cefepime MIC≤8 μg/mL; these isolates were collected at Nagasaki University Hospital from January 2005 to March 2011. In this sample, 145 isolates (27.5%) tested positive for pAmpC (pAmpC group). The concordance rates of phenotypic and genotypic detection of ESBLs were 69.2% in the pAmpC group and 88.8% in the non-pAmpC group (P=0.04). pAmpC was more commonly detected in isolates with non-CTX-M genes (5/53, 9.4%) than in isolates with CTX-M genes (8/121, 6.6%). Our data suggest that the presence of pAmpC increases the false negative detection of ESBL. When ESBL phenotyping is used, the underestimation of the prevalence of ESBL producers should be taken into account.

Mutations associated with in vitro resistance to bedaquiline in Mycobacterium tuberculosis isolates in Australia

Genome-wide analysis of 517 Mycobacterium tuberculosis isolates from New South Wales, Australia, have identified previously reported and 8 new mutations in Rv0678 and atpE genes linked to in vitro resistance to bedaquiline, a new class of antimycobacterial drugs. These mutations were present in 2.9% of prospectively sequenced genomes but in 10.6% of strains that were phenotypically multidrug-resistant. However only 14% of isolates with these mutations demonstrated elevated minimum inhibitory concentrations to bedaquiline.

Overinduction of CYP51A Gene After Exposure to Azole Antifungals Provides a First Clue to Resistance Mechanism in Fusarium solani Species Complex.

The genus Fusarium is largely represented in fungal infections, not only mostly in plants but also in humans. Fungi belonging to the Fusarium solani species complex (FSSC) are those that are most frequently isolated in invasive fusariosis and present elevated minimum inhibitory concentrations for the main antifungal drugs used in medicine. This study is the first to investigate the resistance mechanism in FSSC by monitoring CYP51A expression in the presence of azole antifungals. After exposure to voriconazole, an overinduction of CYP51A was observed irrespective of the concentration of antifungal used and the generation studied. The same observation is made for other azole antifungals, posaconazole and tebuconazole, but not for amphotericin B. This observation could contribute to explaining why some antifungal molecules used in agriculture or medical practices may have low susceptibility for some fungi.

Vancomycin and daptomycin minimum inhibitory concentrations as a predictor of outcome of methicillin-resistant Staphylococcus aureus bacteraemia.

The aim of this study was to determine the persistence of the adverse prognostic effect of elevated vancomycin minimum inhibitory concentration (MIC) in methicillin-resistant Staphylococcus aureus (MRSA) bacteraemia in a setting with low vancomycin use. A retrospective study focusing on episodes of bacteraemia due to MRSA diagnosed from January 2010 through December 2015 was designed. The main outcome measures were 30-day mortality and treatment failure. Multivariate logistic regression analysis was used to identify variables associated with patient mortality and treatment outcome. In total, 79 MRSA bacteraemia episodes were included. The vancomycin MIC was >1.0μg/mL in 53 episodes (67.1%). The presence of high vancomycin MIC was not associated with a higher mortality rate or treatment success. A daptomycin MIC≥0.5μg/mL was present in 16 (26.2%) of 61 episodes for which the daptomycin MIC was obtained and was associated with 30-day mortality in the multivariate analysis (odds ratio=4.72, 95% confidence interval 1.19-18.71). None of the antimicrobials used were associated with a lower risk of treatment failure or mortality. The pernicious effect of high vancomycin MIC disappears in the absence of a predominant use of this antibiotic. However, a high daptomycin MIC in MRSA bacteraemia is associated with higher mortality in patients with bacteraemia, irrespective of antimicrobial treatment choice.

Antimicrobial susceptibility of Avibacterium paragallinarum isolates from outbreaks of infectious coryza in Dutch commercial poultry flocks, 2008–2017

The objective of the present study was to determine the in vitro antimicrobial susceptibility of Avibacterium paragallinarum isolates from infectious coryza outbreaks in Dutch commercial poultry, from 2008 till mid-2017. By using a broth microdilution method, minimal inhibitory concentrations (MICs) of 15 antimicrobial agents were assessed, and MIC50 and MIC90 values were determined. Additionally, isolates were subjected to different PCRs for the presence of genes that may confer antimicrobial resistance. Besides field isolates, a set of reference strains, among which the nine Kume strains and one Page serovar strain, were included in the study.For broth microdilution testing a new growth medium, recently developed for susceptibility testing of Haemophilus parasuis, was used. The medium proved to be suitable for broth microdilution susceptibility testing of NAD dependent Av. paragallinarum as well; visible growth was obtained in growth control wells and accepting a deviation of one dilution step, MIC values were reproducible. Results of 44 field isolates originating from 25 outbreaks showed relatively good susceptibility to antimicrobial agents that are recommended for the treatment of infectious coryza in the Netherlands, except for tetracycline; circa 75% of the isolates were characterized by MIC values of tetracycline of ≥16 μg/ml. In almost a quarter of these isolates with high MICs of tetracycline, tet genes were detected. For the remaining isolates with elevated MIC values, the mechanism conferring resistance remains to be studied. Of most agents, low MIC values were determined for the nine Kume and one Page serovar reference strains, as well as negative PCR results for resistance genes, being concordant with agar diffusion results reported for these strains.

Is previous azithromycin treatment associated with azithromycin resistance in Neisseria gonorrhoeae? A cross-sectional study using national surveillance data in England

ObjectivesIt has been suggested that treatment of STIs with azithromycin may facilitate development of azithromycin resistance in Neisseria gonorrhoeae (NG) by exposing the organism to suboptimal doses. We investigated whether...

Invasive Fungal Infections in Patients with Hematological Malignancies: Emergence of Resistant Pathogens and New Antifungal Therapies.

Invasive fungal infections caused by drug-resistant organisms are an emerging threat to heavily immunosuppressed patients with hematological malignancies. Modern early antifungal treatment strategies, such as prophylaxis and empirical and preemptive therapy, result in long-term exposure to antifungal agents, which is a major driving force for the development of resistance. The extended use of central venous catheters, the nonlinear pharmacokinetics of certain antifungal agents, neutropenia, other forms of intense immunosuppression, and drug toxicities are other contributing factors. The widespread use of agricultural and industrial fungicides with similar chemical structures and mechanisms of action has resulted in the development of environmental reservoirs for some drug-resistant fungi, especially azole-resistant Aspergillus species, which have been reported from four continents. The majority of resistant strains have the mutation TR34/L98H, a finding suggesting that the source of resistance is the environment. The global emergence of new fungal pathogens with inherent resistance, such as Candida auris, is a new public health threat. The most common mechanism of antifungal drug resistance is the induction of efflux pumps, which decrease intracellular drug concentrations. Overexpression, depletion, and alteration of the drug target are other mechanisms of resistance. Mutations in the ERG11 gene alter the protein structure of C-demethylase, reducing the efficacy of antifungal triazoles. Candida species become echinocandin-resistant by mutations in FKS genes. A shift in the epidemiology of Candida towards resistant non-albicans Candida spp. has emerged among patients with hematological malignancies. There is no definite association between antifungal resistance, as defined by elevated minimum inhibitory concentrations, and clinical outcomes in this population. Detection of genes or mutations conferring resistance with the use of molecular methods may offer better predictive values in certain cases. Treatment options for resistant fungal infections are limited and new drugs with novel mechanisms of actions are needed. Prevention of resistance through antifungal stewardship programs is of paramount importance.

Antibioresistance of Microbial Strains Implicated in the Etiology of Sepsis with Oro-Maxillofacial Portal of Entry

Methicillin-resistance phenomenon regarding Staphylococcus aureus which is often met as etiologic agent of severe systemic infections with oral-maxillofacial portal of entry imposes the first-line therapeutic schemes readjustment in patients with significant risk factors. Minimum inhibitory concentration (MIC) determination for every isolated S.aureus strain is useful for the antibiotherapy guiding, in order to choose the appropriate antimicrobial substances and to avoid the selection of resistant mutants. There have been studied and tested 9036 bacterial strains isolated from patients hospitalized in the Sf.Spiridon Emergency County Hospital between 2013-2016. Minimum inhibitory concentrations (MIC), MIC 50 and MIC 90 values were determined for the following antibiotics: Penycilline, Erithromycin, Oxacylline, Tetracycline, Gentamycin, Tobramycine, Kanamycin, Ryfampicyn, Trimethoprim-Sulfamethoxazole, Ofloxacine, Ciprofloxacine and Vancomycin.The classification of each identified bacterial strain into sensitive or resistant was accomplished according to the breakpoints recommended by CLSI 2016 (Clinical and Laboratory Standard Institute). We considered intermediately susceptible isolates as being resistant. S.aureus antibioresistance was high to tetracycline, erythromycin and kanamycin, with elevated MIC 90 values (64�g). The rate of resistance to penicillin in the case of S.aureus was 94.7%. The lowest MIC values regarding Pseudomonas aeruginosa were for imipenem, meropenem and colistin and the highest ones for piperacillin-tazobactam, ceftazidime and amikacin. Third generation cephalosporins demonstrated their inefficiency in the staphylococcal infections� treatment as a consequence of an increasing resistance to this category of betalactams. Vancomycin remains a saving in-hospital therapeutic option in the case of MRSA implication, next to teicoplanin and linezolid.

Characterisation of a novel plasmid containing a florfenicol resistance gene in Haemophilus parasuis

Thirty clinical isolates of H. parasuis from pig farms in eastern China were screened for antimicrobial susceptibility. A novel plasmid, designated pHPSGC, was extracted from one isolate with evidence of resistance (elevated minimum inhibitory concentration) to florfenicol. DNA sequencing demonstrated that pHPSGC (5297 base pairs) contains three open reading frames (ORFs), corresponding to the genes rep, floR and lysR. The rep gene of pHPSGC shared 99% sequence identity with the rep gene of pHPS1019. In addition, the region containing floR and lysR in pHPSGC shared 99% similarity with the corresponding region of pCCK381. pHPSGC may be derived from a recombination event between pHPS1019 and pCCK381. A florfenicol resistance gene in H. parasuis may have been transferred via recombination between different plasmids.

Activities of Dual Combinations of Antibiotics Against Multidrug-Resistant Nontuberculous Mycobacteria Recovered from Patients with Cystic Fibrosis.

Patients with cystic fibrosis (CF) are at risk for recurrent pulmonary infections due to increased viscosity of airway secretions, leading to persistent colonization with pathogenic bacteria, including nontuberculous mycobacteria (NTM). Extensive antibiotic use for treatment of infections has led to increasing antimicrobial resistance, which is a significant barrier to the treatment of NTMs. We examined the in vitro activity of several antibiotics against a selection of the most drug-resistant clinical isolates of Mycobacterium abscessus, Mycobacterium chelonae, and Mycobacterium avium complex recovered from CF patients at our institution, as well as paired combinations of antibiotics against a subset of M. abscessus strains, to determine whether they exhibit synergy in inhibiting bacterial growth. Most isolates displayed resistance to at least six of the nine antibiotics tested for which phenotypic interpretation is available, and elevated minimum inhibitory concentrations (MICs) were observed for many of the other drugs. The major exception was clofazimine, which had relatively low MICs for most isolates across all species. When synergy testing was performed by using paired combinations of drugs, clofazamine and clarithromycin exhibited 100% synergy for all combinations tested, as did amikacin, with the exception of one isolate. These results suggest that synergistic antibiotic combinations are capable of overcoming drug resistance in vitro, and laboratories might consider implementation of synergy testing in multidrug-resistant (MDR)-NTM organisms to guide treatment decisions in the setting of extensive antimicrobial resistance.