Strains Of Gram-negative Rods Research Articles

In vitro activity of antibiotics potentially effective against difficult-to-treat strains of Gram-negative rods: retrospective study

Bacterial resistance surveillance is one of the main outputs of microbiological laboratories and its results are important part of antimicrobial stewardship (AMS). In this study, the susceptibility of specific bacteria to selected antimicrobial agents was tested. The susceptibility of 90 unique isolates of pathogens of critical priority obtained from clinically valid samples of ICU patients in 2017–2021 was tested. 50% of these fulfilled difficult-to-treat resistance (DTR) criteria and 50% were susceptible to all antibiotics included in the definition. 10 Enterobacterales strains met DTR criteria, and 2 (20%) were resistant to colistin (COL), 2 (20%) to cefiderocol (FCR), 7 (70%) to imipenem/cilastatin/relebactam (I/R), 3 (30%) to ceftazidime/avibactam (CAT) and 5 (50%) to fosfomycin (FOS). For Enterobacterales we also tested aztreonam/avibactam (AZA) for which there are no breakpoints yet. The highest MIC of AZA observed was 1 mg/l, MIC range in the susceptible cohort was 0.032–0.064 mg/l and in the DTR cohort (incl. class B beta-lactamase producers) it was 0.064–1 mg/l. Two (13.3%) isolates of Pseudomonas aeruginosa (15 DTR strains) were resistant to COL, 1 (6.7%) to FCR, 13 (86.7%) to I/R, 5 (33.3%) to CAT, and 5 (33.3%) to ceftolozane/tazobactam. All isolates of Acinetobacter baumannii with DTR were susceptible to COL and FCR, and at the same time resistant to I/R and ampicillin/sulbactam. New antimicrobial agents are not 100% effective against DTR. Therefore, it is necessary to perform susceptibility testing of these antibiotics, use the data for surveillance (including local surveillance) and conform to AMS standards.

Design, Synthesis, and Characterization of Novel Coordination Compounds of Benzimidazole Derivatives with Cadmium.

Four complexes of Cd(II) with benzimidazole derivatives were synthesized and named C1, C2, C3, and C4. All coordination compounds were characterized through elemental analysis (EA), flame atomic absorption spectrometry (FAAS), Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis coupled with mass spectrometry) (TG-MS), a cytotoxicity assay (MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazoliumbromide)), and computational chemical analysis for absorption, distribution, metabolism, and excretion (ADME). All of the obtained results are compatible and are consistent with the respective structures of the obtained compounds and their properties. The various techniques used allowed the determination of the composition, proposed structure of the compounds, their thermal stability and thermal properties, and the method of coordination between the metal (II) ion and the ligand. The ADME technique was also used to estimate the physicochemical and biological properties. The antitumor activity of the compounds was determined with an MTT assay on the glioblastoma (T98G), neuroblastoma (SK-N-AS), and lung adenocarcinoma (A549) cell lines, as well as normal human skin fibroblasts (CCD-1059Sk). Compound C2 was found to have potential antitumor properties and to be effective in inhibiting the growth of neuroblastoma cells. The antimicrobial activity of Cd complexes, free ligands, and reference drugs was tested against six strains of Gram-positive bacteria, five strains of Gram-negative rods, and three strains of yeasts. Compound C3 significantly increased activity against Gram-positive bacteria in comparison to the ligand.

An Application of Imipenem Discs or P. aeruginosa ATCC 27853 Reference Strain Increases Sensitivity of Carbapenem Inactivation Method for Non-Fermenting Gram-Negative Bacteria

Non-fermenting Gram-negative rods are one of the most commonly isolated bacteria from human infections. These microorganisms are typically opportunistic pathogens that pose a serious threat to public health due to possibility of transmission in the human population. Resistance to beta-lactams, due to carbapenemases synthesis, is one of the most important antimicrobial resistance mechanisms amongst them. The aim of this study was to evaluate the usefulness of the Carbapenem Inactivation Method (CIM), and its modifications, for the detection of carbapenemase activity amongst non-fermenting Gram-negative rods. This research involved 81 strains of Gram-negative rods. Of the tested strains, 55 (67.9%) synthesized carbapenemases. For non-fermenting rods, 100% sensitivity and specificity was obtained in the version of the CIM test using imipenem discs and E. coli ATCC 25922 strain. The CIM test allows for differentiation of carbapenems resistance mechanisms resulting from carbapenemase synthesis from other resistance types. It is a reliable diagnostic method for the detection of carbapenemase activity amongst non-fermenting Gram-negative rods. Application of imipenem discs and P. aeruginosa ATCC 27853 reference strain increases CIM results sensitivity, while imipenem discs and E. coli ATCC 25922 strain use maintains full precision of the test for non-fermenting rods.

Działanie in vitro olejku cyprysowego (Oleum Cupressi) na bakterie beztlenowe

Introduction. Cypress (Cupressus sempervirens L.) belongs to the family Cupressaceae. It is evergreen, and grows in Mediterranean region. The Cypress leaves and young branches are utilized to produce the essential oil. Cypress oil contain a number of components, in it α-pinene, Δ3-carene, α-terpinyl acetate, cedrol, α-terpinolene, β-myrcene, limonene, α-terpineolene, terpinen-4-ol, β-pinene, δ-cadinene and sabinene. The oil is used in therapy different diseases. It to have antimicrobial activity. Aim. The aim of the date was evaluation the susceptibility of anaerobic bacteria to Cypress oil. Material and methods. The anaerobic bacteria were isolated from patients. The 62 microorganisms, in it 36 strains of Gram-negative rods, 14 Gram-positive cocci and 12 Gram-positive rods, and 7 reference strains were tested. Susceptibility (MIC) was determined by means of plate dilution technique in Brucella agar supplemented with 5% defibrynated sheep blood, menadione and hemin. The Cypress oil was dissolved in DMSO and distilled water to obtain final following concentrations: 2.5, 5.0, 7.5, 10.0, 15.0 and 20.0 mg/ml. Inoculum containing 106 CFU per 1 ml was seeded with Steers replicator upon the agar with oil or without the oil (strains growth control). The agar plates was incubated in anaerobic condition in anaerobic jar in 37°C for 48 hrs. The MIC was interpreted as the lowest concentration of Cypress oil inhibiting the growth of tested bacteria. Results. The results indicated that from among Gram-negative rods the most susceptible to Cypress oil was the strains from genus Tannerella forsythia (MIC < 2.5-5.0 mg/ml), Bacteroides uniformis (MIC = 5.0 mg/ml), Bacteroides vulgatus and Porphyromonas asaccharolytica (MIC 5.0-7.5 mg/ml) and Porphyromonas levii (MIC = 7.5 mg/ml). The strains from genera Fusobacterium and of Bacteroides fragilis were the susceptible to 2.5-≥ 20.0 mg/ml. The Cypress oil was least active towards Prevotella and Parabacteroides strains (MIC ≥ 20.0 mg/ml).The tested Gram-positive cocci were more susceptible. The growth of the strains were inhibited by concentrations in ranges ≤ 2.5-7.5 mg/ml. The oil was minor active towards Gram-positive rods (MIC ≤ 2.5-20.0 mg/ml). Among the strains the genus of Actinomyces odontolyticus (MIC = 5.0 mg/ml) and Actinomyces viscosus (MIC ≤ 2.5-7.5 mg/ml) were the most susceptible. The growth of rods of Bifidobacterium breve was inhibited by concentrations 10.0 mg/ml. The data indicates that the Gram-negative rods were the less susceptible than Gram-positive bacteria to cypress oil. Conclusions. Among Gram-negative rods the most susceptible were the strains Tannerella forsythia, Bacteroides uniformis, Bacteroides vulgatus, Porphyromonas asaccharolytica and Porphyromonas levii. The oil was more active against Gram-positive cocci. Gram-positive anaerobic bacteria demonstrate the more susceptible to Cypress oil then Gram-positive rods.

Wpływ olejku świerkowego (Oleum Picea excelsa) na bakterie beztlenowe

Introduction. Spruce (Picea abies L.) is a member of family Pinaceae. It was known and used in ancient. The tree grown to 50 m height. Produced by conifers etheric oil possesses antibacterial, antifungal and antioxidant properties. The major compounds of the spruce oil are: pinene, cadinene and felandrene. It is obtained hydro distillation method. Aim. The aim of the date was to investigate activity of spruce oil against anaerobic bacteria. Material and methods. The 53 of anaerobic bacteria isolated from oral cavity and upper respiratory tract, in it 32 strains of Gram-negative rods, 12 Gram-positive rods and 9 Gram-positive cocci were tested. Moreover investigated 8 reference strains. Susceptibility (MIC) was determined by two-fold dilution technique in Brucella agar with 5% defibrynated sheep blood, menadione and hemin. The spruce oil was dissolved in DMSO and distillated water to obtained a final concentrations 2.5, 5.0, 7.5, 10.0, 15.0 and 20.0 mg/ml. The inoculums containing 106 CFU/ml was seeded with Steers replicator upon the surface of agar with oil or without tested essential oil (strains growth control). Incubation the agar plates was performed in anaerobic conditions in anaerobic jars containing 10% C02 , 10% H2 and 80% N2 , palladic catalyst and anaerobic indicator, at 37°C for 48 hrs. The MIC was established as the lowest concentration of the spruce oil that inhibiting the growth of tested anaerobes. Results. The results of these investigations indicated that the most susceptible to spruce oil from Gram-negative bacteria were the strains Prevotella intermedia (MIC 5.0-10.0 mg/ml) and Porphyromonas levii (MIC = 7.5 mg/ml). The growth of strains from genus Bacteroides fragilis was inhibited by concentration > 20.0 mg/ml, and Tannerella forsythia in ranges from 15.0 to > 20.0 mg/ml. The Gram-positive bacteria were more susceptible. The growth of 50% of this rods was inhibited in concentration 2.5-7.5 mg/ml. From Gram-positive rods from genus of Actinomyces odontolyticus were the most susceptible. The 75% of the rods were inhibited by spruce oil in concentrations 2.5-7.5 mg/ml. The least sensitive was the strain Actinomyces viscosus (MIC = 15.0 mg/ml). The tested oil was more active on account Gram-positive cocci. The growth was inhibited by concentrations in ranges 2.5-7.5 mg/ml. The Gram-positive cocci were more susceptible than Gram-positive rods. The data indicated that the spruce oil was more active towards Gram-positive rods than Gram-negative anaerobes. Conclusions. From the Gram-negative bacteria the Prevotella rods were the more susceptible to spruce oil. The oil was the less active towards Gram-negative rods from genus Tannerella forsythia. From Gram-positive anaerobic bacteria the Gram-positive cocci were the more susceptible to spruce oil then Gram-positive rods.

Microbial contamination of surgical instruments used for laparotomy

The aim of this study was to determine the risk of contamination of surgical instruments according to the type of instrument and the surgical procedure. Microbiologic examination was conducted on 140 pairs of forceps used in 24 elective laparotomies. These included 60 pairs of tissue forceps and 80 pairs of DeBakey forceps. Microbes on their surface were recovered using a membrane filter method. Adenosine triphosphate assay was also performed simultaneously in each pair of forceps. A total of 66 strains of microbes was recovered from 44 collected instruments (31%), with microbial counts ranging from 0 to 296 colony-forming units. Among the recovered microbes, gram-positive cocci were dominant [corrected]. The remaining microbes included 6 strains of gram-positive rods and 4 strains of gram-negative rods. The most common organism was Staphylococcus epidermidis, followed by S hominis and S warneri. Residual adenosine triphosphate was not correlated with the number of recovered microbes. Surgical instruments tend to be contaminated during operations by microbes that inhabit the skin and organs. Surgical instruments could act as fomites for the pathogens of surgical site infection even if the surgical field is not apparently contaminated, through application of appropriate practices adhering to surgical site infection guidelines.

Bacterial pneumonia as a result of mechanical ventilation in patients treated in intensive care units – epidemiological importance

Introduction. Ventilator-associated pneumonia (VAP) is among the most common hospital infections in an Intensive Care Unit (ICU). The most important risk factors of VAP are endotracheal catheterization and mechanical ventilation. Aim. The objective of the study was evaluation of the prevalence of ventilator-associated pneumonia, and determination of the type of microbiological agents in specimens collected from the bronchial tree. Material and methods. The study covered 42 patients: 59.5% of males and 40.5% of females, hospitalized in the Intensive Care Unit (ICU), in whom mechanical ventilation was applied. Airway secretion was grown on a solid agar medium: Columbia agar with 5% sheep blood, chocolate agar, McConkey and Sabouraud media. Identification of the bacterial strains grown was based on the determination of their biochemical properties, with the use of commercial assays (bio-Merieux): ID 32E and ID 32GN and tests ID 32 STAPH and API 20 STREP. Results. In the group of 42 patients who received mechanical ventilation (59.5% of the total number of hospitalized patients) VAP developed in 17 patients (40.5%). From the specimens 30 (34.9%) strains of Gram-negative rods, 19 (22%) strains of Gram-positive cocci, and 13 (15.1%) fungi were grown. The largest number of strains was isolated in patients who received artificial ventilation until day 20 of hospitalization. Conclusions. The microorganisms most often isolated from the upper airways were Gram-negative rods; patients admitted to ICU from other wards were colonized with bacterial flora conveyed with them from the original ward; the duration of artificial ventilation increases the risk of occurrence of ventilator-associated pneumonia.

Nitrito urinário e infecção do trato urinário por cocos gram-positivos

INTRODUCAO: A infeccao do trato urinario (ITU) e uma das mais comuns na clinica medica. Os testes que utilizam tiras reagentes detectam significativamente mais infeccoes por bacterias gram-negativas do que por especies gram-positivas, uma vez que o teste de nitrito nao revela a presenca de patogenos gram-positivos em muitos casos. OBJETIVOS: Explorar a microbiologia e a frequencia de infeccao urinaria por cocos em adultos sintomaticos, relacionando-as com o resultado de nitrito urinario, para tracar o perfil epidemiologico desses pacientes. MATERIAL E METODO: Um estudo retrospectivo foi conduzido na Secretaria de Saude do municipio de Maringa-PR, no periodo de abril de 2004 a marco de 2005. RESULTADOS: Amostras de urina de 3.426 pacientes foram coletadas e analisadas. Um total de 448 (13,1%) amostras foi positivo para cultura. Em 388 (86,6%) casos houve crescimento de bacilos gram-negativos (BGN) e em 60 (13,4%) casos, cocos gram-positivos (CGP). A analise estatistica de co-morbidades revelou diferenca significativa na proporcao de pacientes com hipertensao (31,3% com nitrito positivo versus 4,5% com nitrito negativo, p < 0,05). Os pacientes com resultado de nitrito positivo relataram febre em proporcao maior que os com nitrito negativo (75% versus 43,2%, respectivamente; p < 0,05). Staphylococcus aureus redutores de nitrato mostraram maior resistencia a ciprofloxacina (66,7%) quando em comparacao com os isolados nao-redutores (100% sensiveis). CONCLUSOES: Este estudo preliminar mostrou que a avaliacao de sinais clinicos e sintomas, juntamente com o resultado de nitrito urinario na tira reagente, poderia auxiliar o medico na tomada de decisoes importantes.

Nosocomial Bacteremia in Neonates Related to Poor Standards of Care

In developing countries, intravenous liquids are mixed and administered by nurses, sometimes under suboptimal infection control conditions. We hypothesized that outbreaks of infusate-associated neonatal bacteremias are common, and we evaluated whether they can be detected by vigilant microbiologic surveillance of infusates. We studied intravenous infusates administered to neonates in a Mexican hospital where mixtures of infusates were prepared in hospital wards. The study was performed in 3 stages: stage 1, initial culturing of in-use infusates under basal conditions; stage 2, prospective culturing during a cluster of clinical sepsis; and stage 3, final culturing once the outbreak was controlled. In stage 1, 68 infusates were sterile, and 1 was contaminated with Staphylococcus aureus (1.45%), from 23 patients. In stage 2, of 182 infusates from 39 patients, 51 infusates (28%) were contaminated with Gram-negative rods. On the first day of stage 2, 11 of 15 infusates were contaminated with the same strain of Klebsiella pneumoniae, which continued to appear for 26 days. Another 4 strains of Gram-negative rods were also isolated during stage 2. The association between contaminated infusate and death was significant (odds ratio, 9.4; 95% confidence interval, 2-44.3; P < 0.001). Mixtures made by nurses were more likely contaminated than commercial preparations (odds ratio, 3.1; 95% confidence interval, 1.1-8.5; P = 0.037). In stage 3, there were 42 sterile infusates from 22 patients. Our study suggests that poor standards of care common in hospitals from developing countries sometimes result in outbreaks of sepsis and death for newborn patients.

Evaluation of an automated system for identification of Enterobacteriaceae and nonfermenting bacilli.

The performance of the Vitek 2 (bioMérieux, France), a new fully automated system allowing rapid identification of microorganisms and susceptibility testing, and the Vitek 2 ID-GNB card (bioMérieux) was evaluated using 502 clinical isolates and stock collection strains of gram-negative rods belonging to 70 taxa. The number of isolates correctly identified to species and genus levels was 430 (85.7%) and 485 (96.6%), respectively. Clinical isolates of both Enterobacteriaceae and non-Enterobacteriaceae were better identified at the species level (95.3% and 74%, respectively) than stock collection strains (86.4% and 52.2%, respectively). The Vitek 2 ID-GNB card provides after 3 h a highly acceptable level of accuracy for identification of Enterobacteriaceae and non-Enterobacteriaceae, including most atypical strains encountered in clinical situations.

Isolation of Serratia fonticola from Mollusks

Summary Eleven of some 2400 strains of gram-negative rods isolated from mollusks were identified as Serratia fonticola both biochemically and by DNA hybridization. The phenotypic and genotypic data confirm that S. fonticola belongs to the genus Serratia .

A clinical study on cefteram pivoxil in pediatrics

Clinical evaluations of cefteram pivoxil (CFTM-PI, T-2588) were carried out. The obtained results are summarized as follows. 1. Clinical responses to CFTM-PI of 39 patients with pediatric infections were excellent in 16, good in 21, fair in 1 and poor in 1. The overall efficacy rate was 94.9%. 2. Bacteriologically, eradication rates for 39 isolates presumed to be pathogens were evaluated. The eradication rates obtained were 94.1% in 17 strains of Gram-positive cocci, 90.9% in 22 strains of Gram-negative rods. 3. Side effects observed were diarrhea in 2 patients, diarrhea and abdominal pain in 1, erythema and edema in 1. The incidence was 8.7%. An abnormal value found in clinical laboratory tests was eosinophilia in 1 patient. The results suggested that CFTM-PI might be a very useful and safe drug for the treatment of pediatric infections.

The comparative in-vitro activity of norfloxacin, ciprofloxacin, enoxacin and nalidixic acid against 423 strains of Gram-negative rods and staphylococci isolated from infected hospitalised patients

The in-vitro activities of four quinolone carboxylic acids against 423 clinical isolates of Gram-negative rods and staphylococci from infected hospitalised patients were compared. The antibiotics included nalidixic acid and the newer compounds, norfloxacin (MK-0366), ciprofloxacin (Bay 09867) and enoxacin (AT 2266 or CI919). Norfloxacin showed slightly more activity than enoxacin, but both agents had markedly greater potencies and broader antibacterial spectrums than nalidixic acid. Ciprofloxacin was the most active quinolone tested against both gentamicin-susceptible and gentamicin-resistant stains, having an MIC90 equal or less than 1 mg/l for all species studied.

The activity of temocillin against Enterobacteriaceae, Pseudomonas and Haemophilus influenzae.

The in vitro antimicrobial activity of temocillin against 130 strains of Enterobacteriaceae and 27 strains of Pseudomonas and other related Gram-negative organisms was compared with carbenicillin, mezlocillin and piperacillin. Temocillin was compared with ampicillin against 76 strains of Haemophilus influenzae. More than 90% of Enterobacteriaceae including 65 carbenicillin-resistant strains were inhibited by 8 mg/L of temocillin. Pseudomonas spp. were less susceptible to temocillin than to the other 3 penicillins. 35 out of 38 strains of beta-lactamase-producing H. influenzae were inhibited by 2 mg/L of temocillin. But with 38 ampicillin-sensitive and non-beta-lactamase-producing ampicillin-resistant strains, temocillin was slightly less active than ampicillin. There was no significant enhancement of temocillin activity by clavulanic acid against 20 strains of Gram-negative rods producing characterised beta-lactamases. The resistance to plasmid-mediated and chromosomal beta-lactamase extracts was also studied by bioassay method. No enzyme extracts tested could hydrolyse temocillin except that from one Flavobacterium strain.

Differentiation of Enterobacteriaceae and Vibrionaceae by a micromethod for determination of carbon substrate assimilation.

The assimilation techniques described for taxonomic study are unsuitable for routine diagnosis because of the need for purification and standardization of substrates, the great quantity of medium consumed and difficulties in interpreting the results. A standardized micromethod (API strip) for the study of carbon substrate assimilation by bacteria has recently been described (Zbl. Bakt. Hyg., I. Abt. Orig. A 255 (1983) 479-488). The prototype gallery used consisted of two strips of 32 microtubes each containing dehydrated carbon substrate. Each strip contained 30 tests plus positive and negative controls. The suspension medium was a synthetic semi-gel. A total of 914 strains of Gram negative rods representing 44 species of Enterobacteriaceae and Vibrionaceae were tested (Table 1). Automatic reading was performed after incubation at 32 degrees C for one day, or two days for slow growing bacteria using an ATB - 1500 reader (API System) linked to a HP 85 microcomputer (Hewlett-Packard). Most species showed typical carbon substrate assimilation patterns allowing their differentiation from other species within each genus (Table 2). The results obtained with the micromethod agreed in large measure with the nutritional patterns reported by other workers. It should be possible to use these results to construct a coherent framework of tests suitable for identifying species of Enterobacteriaceae and Vibrionaceae of clinical significance.

Use of selenite reduction in bacterial classification.

SUMMARYThe ability of 548 strains of Gram negative rods to reduce selenite was investigated in parallel with their ability to produce H2S and reduce nitrate. Reduction of selenite was shown to be a reasonably good test compared with other tests used in classifying these organisms. The ability to reduce selenite often paralleled the ability to produce H2S; it did not parallel the ability to reduce nitrate.

Organisms resembling Alcaligenes faecalis.

Forty strains of Gram-negative rods which resembled Alcaligenes in failing to attack carbohydrates were studied. Twenty-four strains had lophotrichous flagella, three were monotrichous, three were either lophotrichous or monotrichous, six were peritrichous, and four were nonflagellated. Strains were grouped by their action on gelatin and nitrate, and by motility. Most lophotrichous and monotrichous organisms liquefied gelatin, reduced nitrate, or did both, whereas most peritrichous and nonflagellated rods failed to do either.Serological studies indicated antigenic heterogeneity, but some strains in the more homogeneous physiological groups were related, mainly through flagellar antigens. Three phages were obtained without induction but only one of these was lytic for a single heterologous strain. Inducible substances resembling bacteriocines were elaborated by several strains, and the activity was confined primarily to homogeneous physiological and serological groups. Some lophotrichous strains closely resembled but were not identical with the genus Lophomonas. The validity of the genus Alcaligenes is questioned, since few isolates resemble the original description (peritrichous flagella) and these could be included in the genus Achromobacter.