Fermenting Gram Negative Bacilli Research Articles

An Update on Novel Taxa and Revised Taxonomic Status of Bacteria (Including Members of the Phylum Planctomycetota) Isolated from Aquatic Host Species Described in 2018 to 2021.

Increased interest in farmed aquatic species, aquatic conservation measures, and microbial metabolic end-product utilization have translated into a need for awareness and recognition of novel microbial species and revisions to bacterial taxonomy. Because this need has largely been unmet, through a 4-year literature review, we present lists of novel and revised bacterial species (including members of the phylum Planctomycetota) derived from aquatic hosts that can serve as a baseline for future biennial summaries of taxonomic revisions in this field. Most new and revised taxa were noted within oxidase-positive and/or nonglucose fermentative Gram-negative bacilli, including members of the Tenacibaculum, Flavobacterium, and Vibrio genera. Valid and effectively published novel members of the Streptococcus, Erysipelothrix, and Photobacterium genera are additionally described from disease pathogenesis perspectives.

Development of a Manometric Monitoring Method for Early Detection of Air Microbiological Contamination in the Bloodstream

Atmospheric air is a microbial habitat of pathogenic bioaerosols that may pose serious risks to humans. A commonly laboratory-based approach for the diagnosis of such infections in the bloodstream is the blood culture analysis. Its clinical relevance is attributed to the fact that these infections are characterized by high rates of morbidity and mortality, requiring the need for efficient methods for rapid diagnosis. For this reason, our study aimed to develop a method of manometric monitoring for the rapid detection of viable microorganisms in blood culture vials. A methodology was developed to detect pressure variation in intra-vials through a manometric instrument that was coupled to vials of blood culture containing culture broth that allowed microbial growth. This device allowed the early detection of microbial activity based on the production or use of intra-flask gases as a result of microbial metabolic activity. The analyzed variables were the pressure as a function of time, microbial species, and culture medium. The highest pressure found in the flasks without microorganisms was 40 mmHg between 2 and 6 h, and the lowest pressure was −42 mmHg between 21 and 24 h. The variation of the internal pressure in blood culture flasks according to different groups of microorganisms as a function of time demonstrated that the fermentative gram-negative bacilli and gram-positive cocci exhibited a significant increase in relation to their respective control groups (p < 0.001). The non-fermenting gram-negative bacilli showed expected results in relation to the pressure variation in which the production of negative pressures was noticed during the period of analysis, with a significant difference with respect to their control groups (p < 0.001). The developed methodology for the early detection of microorganisms responsible for bloodstream infection was demonstrated to be effective.

Multidrug-resistant profile and prevalence of extended spectrum β-lactamase and carbapenemase production in fermentative Gram-negative bacilli recovered from patients and specimens referred to National Reference Laboratory, Addis Ababa, Ethiopia.

BackgroundThe emergence of multidrug-resistance (MDR), production of extended-spectrum β-lactamases, and carbapenemase in members of fermentative gram-negative bacilli are a serious threat to public health.ObjectiveThe aim of this study was to determine the burden of multi-drug resistance, the production of extended-spectrum β-lactamases (ESBLs), and carbapenemase in fermentative Gram-negative bacilli in Ethiopian Public Health Institute.Materials and methodsA cross-sectional study was carried out from December 2017 to June 2018. Different clinical samples were collected, inoculated, and incubated according to standard protocols related to each sample. Bacterial identification was performed by using the VITEKR 2 compact system using the GNR card. Antimicrobial susceptibility testing was carried out by the Kirby-Bauer disc diffusion method. Production of ESBL and carbapenemase were confirmed by combination disc and modified Hodge Test method respectively.ResultsA total of 238 fermentative Gram-negative bacilli were recovered during the study period, among which E.coli were the predominant isolates followed by K. pneumoniae. The highest percentage of antibiotic resistance was noted against ampicillin (100%) followed by trimethoprim/sulfamethoxazole (81.9%). The isolates showed better sensitivity towards carbapenem drugs. Out of 238 isolates, 94.5% were MDR and of which 8.8% and 0.8% were extensively and pan drug resistant, respectively. Nearly 67% and 2% of isolates were producers of ESBL and carbapenemase, respectively. The isolation rates of MDR, ESBL, and carbapenemase producing stains of the isolates were ≥70% in intensive care unit while the isolation rates in other wards were ≤25%.ConclusionsThe findings of this study revealed that the burden of MDR and ESBL was high and carbapenemase producing isolates were also identified which is concerning. This situation warrants a consistent surveillance of antimicrobial resistance of fermentative Gram-negative bacilli and implementation of an efficient infection control program.

Consumo de antimicrobianos e o impacto na resistência bacteriana em um hospital público do estado do Pará, Brasil, de 2012 a 2016

OBJECTIVE: To evaluate the profile of antibiotic consumption and its impact on bacterial resistance in a university hospital in Para State, Northern Brazil, from 2012 to 2016. MATERIALS AND METHODS: A total of 279 blood cultures from adult patients, both sexes, admitted to wards and Intensive Care Unit (ICU), were selected for further analysis of clinical specimen culture results. RESULTS: Primary bloodstream infections accounted for 60.2% of the total. Gram-negative bacilli (GNB) were the most frequent microorganisms (51.3%), of which the fermenters were resistant to ceftazidime (83.0%) and cefepime (76.1%). Staphylococcus aureus resistance to clindamycin and oxacillin reached 57.4% and 48.9%, respectively. There was a statistically significant reduction in overall consumption of piperacillin + tazobactam and vancomycin. In ICU, there was reduction in ceftriaxone, oxacillin, piperacillin + tazobactam and vancomycin consumption and increase in amikacin and meropenem consumption (all statistically significant). Fermentative GNB and S. aureus showed a positive and nonlinear correlation between the increase of resistance rates and cefepime and oxacillin consumption, respectively. CONCLUSION: Antimicrobial consumption and its impact on bacterial resistance varied over the study period, highlighting the positive and nonlinear correlation between increased cefepime and oxacillin consumption and the recrudescence of fermenting BGN strains and resistant S. aureus strains, respectively.

Risks for multidrug-resistant pathogens in the ICU.

The impact of multidrug-resistant organisms (MDROs) is rising and often underestimated. The epidemiology of MDROs is extremely complex and multifactorial. There is increasing antibiotic resistance, mainly related to antibiotic pressure and patients' characteristics. Emphasis on MDRO epidemiology is needed to better understand current strategies of prevention and management. Among them, antibiotic stewardship has been one of the most successful strategies. It is important to note that there is a controversial issue when considering community and healthcare-related infections. In addition, different strategies have been determined to find the impact and optimal use of recently launched antibiotics for MDRO treatment. Infections with MDROs can prolong hospital stay, promote antibiotic use and prolong duration of mechanical ventilation. Some points should be further explored in clinical research such as the heterogeneity of healthcare-associated pneumonia and the need of new drug development. Resistance to non fermentative Gram-negative bacilli, rising minimum inhibitory concentration in methicillin-resistant Staphylococcus aureus and spread of MDROs in patients without known risk factors suggest a review of guideline validation, taking into account ecology and severity of patient illness to provide timely and appropriate empiric therapy.

Evaluation of three phenotypic methods for the detection of metallo-beta- lactamase production in non fermenting gram negative bacilli

Background & objectives: Non-fermenting gram-negative bacilli (NFGNB) are common nosocomial pathogens and are often resistant to several antibiotics in clinical practice. Metallo-beta-lactamase (MBL) mediated resistance to carbapenems is an emerging threat among hospital isolates of P.aeruginosa. As there are no CLSI guidelines for the detection of these enzymes the present study was conducted with the objective to evaluate three phenotypic methods for the detection of Carbapenemase and MBL production in NFGNB. Methods: 100 consecutive NFGNB resistant to ceftazidime and imepenem by disc diffusion test were included in the study. Resistance to imepenem was confirmed by determining the minimum inhibitory concentration (MIC) by agar dilution method. Three phenotypic tests, namely modified Hodge test (MHT), ethylene di-amine tetra acetic acid (EDTA) imepenem double disk synergy test (DDST) and 4-fold reduction in MIC with imipenem-EDTA combination were evaluated for detection of carbapenemase and MBL production. Results: Of the 100 multidrug resistant NFGNB isolated 66 were P. aeruginosa and 34 were Acinetobacter species. 62 P.aeruginosa and 31 Acinetobacter isolates were confirmed resistant to imepenem by MIC, 7 isolates had MIC values in the intermediate range. 55/100 imepenem resistant isolates were MBL producers by MHT. 73/100 isolates were positive for MBL production by DDST. 74/100 isolates showed more than fourfold fall in MIC with IMP-EDTA combination. In this study 74% of imepenem resistant NFGNB were MBL producers. Interpretation & Conclusion: P.aeruginosa was the predominant NFGNB isolated. DDST and MIC with imipenem EDTA combination are almost equally effective and more sensitive than MHT for detection MBL production. Routine screening for MBL mediated carbapenem resistance among clinical isolates of NFGNB is important to ensure appropriate treatment of infections caused by them in clinical settings.

Detection of Bacterial and Yeast Species with the Bactec 9120 Automated System with Routine Use of Aerobic, Anaerobic, and Fungal Media

During the period 2006 and 2007, all blood cultures required by four units at high infective risk and most of those required by other units of the University Hospital of Palermo, Palermo, Italy were performed using a Bactec 9120 automated blood culture system with a complete set of Plus Aerobic/F, Plus Anaerobic/F, and Mycosis IC/F bottles. The aim of the study was to enable the authors to gain firsthand experience of the culture potentialities of the three different media, to obtain information regarding the overall and specific recovery of bacteria and yeasts from blood cultures in the hospital, and to reach a decision as to whether and when to utilize anaerobic and fungal bottles. Although very few bloodstream infections (1.8%) were associated with obligate anaerobes, the traditional routine use of anaerobic bottles was confirmed because of their usefulness, not only in the detection of anaerobes, but also in that of gram-positive cocci and fermentative gram-negative bacilli. In this study, Mycosis IC/F bottles detected 77.4% of all the yeast isolates, 87.0% of yeasts belonging to the species Candida albicans, and 45.7% of nonfermentative gram-negative bacilli resistant to chloramphenicol and tobramycin. In order to improve the diagnosis of fungemia in high-risk patients, the additional routine use of fungal bottles was suggested when, as occurred in the intensive-care unit and in the hematology unit of the University Hospital of Palermo, high percentages of bloodstream infections are associated with yeasts, and/or antibiotic-resistant bacteria and/or multiple bacterial isolates capable of inhibiting yeast growth in aerobic bottles.

Rapid differentiation of fermentative from nonfermentative gram-negative bacilli in positive blood cultures by an impedance method.

Rapid differentiation of fermentative gram-negative bacilli (fermenters) from nonfermentative gram-negative bacilli (nonfermenters) in positive blood cultures may help physicians to narrow the choice of appropriate antibiotics for empiric treatment. An impedance method for direct differentiation of fermenters from nonfermenters was investigated. The bacterial suspensions (or positive culture broths containing gram-negative bacteria) were inoculated into the module wells of a Bactometer (bioMérieux, Inc., Hazelwood, Mo.) containing 1 ml of Muller-Hinton broth. The inoculated modules were incubated at 35 degrees C, and the change in impedance in each well was continuously monitored. The amount of time required to cause a series of significant deviations from baseline impedance values was defined as the detection time (DT). The percent change of impedance was defined as the change of impedance at the time interval from DT to DT plus 1 h. After testing 857 strains of pure cultures (586 strains of fermenters and 271 strains of nonfermenters), a breakpoint (2.98%) of impedance change was obtained by discriminant analysis. Strains displaying impedance changes of greater than 2.98% were classified as fermenters; the others were classified as nonfermenters. By using this breakpoint, 98.6% (340 of 345) of positive blood cultures containing fermenters and 98% (98 of 100) of positive blood cultures containing nonfermenters were correctly classified. The impedance method was simple, and the results were normally available within 2 to 4 h after direct inoculation of positive blood culture broths.

Comparison of the Minitek system with conventional methods for identification of nonfermentative and oxidase-positive fermentative gram-negative bacilli

The Minitek system was compared with conventional test methods for identifying a wide range of nonfermentative and oxidase-positive fermentative gram-negative bacilli. A total of 230 isolates representing 33 species and biotypes were tested against 12 Minitek substrates and the corresponding conventional tube media. In addition, supplementary tests were included for 141 (61.3%) of the isolates. Overall, 88% of the positive reactions agreed, and negative reactions agreed 95.5%. Anaerobic dextrose, maltose, lactose, and citrate were responsible for 62.4% of the 93 discrepant positive reactions, and 51.8% of the 83 discrepant negative reactions involved the aerobic dextrose, nitrate, and citrate disks. Some discrepancies were related to specific organisms. The system and supplementary tests correctly identified 88.3% of the isolates to species level and 92.6% to correct genus. No particular organism or substrate was responsible for misidentification errors. In a test challenge with 19 selected organisms, 3 were incorrectly identified to species and 4 were misidentified to genus level. Most of the errors responsible for these incorect identifications were due to factors other than the Minitek disks and pointed out the importance of using appropriate supplemental data, and the need for a coding manual and a more enriched broth for certain types of isolates.

Accuracy and reproducibility of the Oxi/Ferm system in identifying a select group of unusual gram-negative bacilli

The Oxi/Ferm (O/F) identification system was compared in a double-blind study to a conventional test battery for the characterization of 96 reference and clinical strains consisting of 83 nonfermentative and 13 oxidase-producing, fermentative gram-negative bacilli. The O/F tube and supplemental tests correctly identified 84% of the nonfermentative and 77% of the oxidase-producing, fermentative bacilli. However, when the supplemental tests were excluded and the biochemical profiles generated by all nine O/F tube reactions were examined, the profile accuracy reached 95% (79 of 83) for the nonfermentative and 93% (12 of 13) for oxidase-producing, fermentative bacilli. Seven of the nine O/F substrate reactions demonstrated less than or equal to 89% agreement with conventional reactions, whereas the urea and arginine reactions provided 82 and 85% agreement, respectively. Replicate O/F tests with six selected organisms demonstrated 97% identification reproducibility and 84% overall substrate reproducibility. The mean O/F identification time was 2.6 days as compared to 3.3 days for the conventional system. Although this study suggests that the O/F system is a convenient, rapid, and accurate alternative to conventional identification methods, several modifications are recommended.