Detection and evaluation of susceptibility to antibiotics in non-hydrogen sulfide-producing antibiotic-resistant soil microbe: Pseudomonas guariconensis

Antimicrobial resistance in bacteria is a global threat that can make antibacterial treatments ineffective. One well-known method of antibiotic resistance and a common defensive mechanism in many harmful bacteria is the synthesis of endogenous hydrogen sulfide (H2S) in bacteria. In this study, soil bacteria were screened using the lead acetate agar test and the triple sugar iron test to determine that they were non-endogenous H2S producers. This was further validated by full genome analysis of the identified organism against the gene sequences of H2S-producing genes. Antibacterial resistance of the bacteria was phenotypically analyzed using the Kirby-Bauer disk diffusion method. Then, the effect of exogenous H2S on the antibiotic-resistant bacteria was checked in sodium sulfide, leading to antibiotic re-sensitization.

Rapid antibiotic susceptibility testing (RAST) of blood cultures in enterobacteria with inducible chromosomal AmpC-type β-lactamase

INTRODUCTION

Early and adequate treatment of bloodstream infections decreases patient morbidity and mortality. The objective is to develop a preliminary method for rapid antibiotic susceptibility testing (RAST) in enterobacteria with inducible chromosomal AmpC.

METHODS

RAST was performed directly on spiked blood cultures of 49 enterobacteria with inducible chromosomal AmpC. Results were read at 4, 6 and 8h of incubation. Commercial broth microdilution was considered the reference method. Disks of 10 antibiotics were evaluated.

RESULTS

The proportion of readable tests at 4h was 85%. All RAST could be read at 6 and 8h. For most antibiotics, the S or R result at 4, 6 and 8h was greater than 80% after tentative breakpoints were established and Area of Technical Uncertainty was defined.

CONCLUSIONS

This preliminary method seems to be of practical use, although it should be extended to adjust the breakpoints and differentiate them by species.

Performances of disk diffusion method for determining triazole susceptibility of Aspergillus species: Systematic review

The therapeutic management of invasive aspergillosis should be guided by antifungal susceptibility testing (AFST). The disk diffusion (DD) method due to its simplicity and low cost could be an appropriate alternative to the reference methods (CLSI, EUCAST) which are not suitable for AFST in routine clinical microbiology laboratories, particularly in resource-constrained settings. This review summarizes the available data on the performance of the DD method in determining triazole susceptibility profile of Aspergillus species. The published articles on the performance of DD method for determining triazole susceptibility of Aspergillus spp. were systematically searched on major medical databases and Google Scholar. We identified 2725 articles of which 13 met the inclusion criteria. The overall average agreement value obtained between DD and CLSI broth microdilution (CLSI-BMD) methods for the itraconazole 10 µg disk (70.75%) was low especially when the medium used was not Mueller-Hinton (MH) agar. In contrast average agreement for the voriconazole 1 µg disk and the posaconazole 5 µg disk were > 94% regardless of media used. The correlation coefficient values between the DD and CLSI-BMD methods on MH agar were acceptable (≥ 0.71) for the itraconazole 10 µg disk and posaconazole 5 µg disk and good (≥ 0.80) for the voriconazole 1 and 10 µg disk. The reproducibility of the DD method regardless to the medium used was ≥ 82%. This systematic review shows that the disk diffusion method could be a real alternative for triazole antifungals susceptibility testing of Aspergillus spp.

Improved disk diffusion method for simple detection of group B streptococci with reduced penicillin susceptibility (PRGBS)

We used 73 group B Streptococcus with reduced penicillin susceptibility (PRGBS) isolates and determined more rational cutoff values of previously developed disk diffusion method for detecting PRGBS using oxacillin, ceftizoxime, and ceftibuten disks. Using the novel cutoff values, the three disks showed high sensitivity and specificity, which were above 90.0%.

Antibacterial Activity Evaluation of ZnO, CuO, and TiO2 Nanoparticles in Solution and Thin Films

This chapter introduces unique methodology of antibacterial activity evaluation of nanoparticles in both solution and thin films. Nanoparticles of ZnO, TiO₂, and CuO are synthesized via the sol-gel method. Antibacterial tests are carried out against Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli bacteria using disk diffusion and bioluminescence. To perform antibacterial tests on thin films and to overcome bacterial strains recuperation on the supports, a new method of bacterial detaching from the slides is developed based on French standard NF EN 14561.

Correlation between antibiotic resistance and clinical outcome of anaerobic infections; mini-review

In anaerobic infections, the relationship between clinical failure and antibiotic resistance is difficult to demonstrate, especially in mixed anaerobic-aerobic infections. Single isolates of anaerobes in cases of bacteraemia revealed that treatment failures were due to inappropriate therapy. We review here cases, where the empiric treatment was unsuccessful due to resistance of anaerobic bacteria to the administered agents and where the change of the antibiotic allowed the patients to be cured. Many therapeutic failures could be linked to the lack of timely detection of resistance, including heteroresistance of the anaerobes. Disk diffusion or Etest methodology may be suitable, at least for rapidly growing anaerobes, to detect both resistance and heteroresistance to antibiotics widely used for empirical therapy.

Antifungal activity of different essential oils against Malassezia pathogenic species

ETHNOPHARMACOLOGICAL RELEVANCE

Plants produce essential oils in response to physiological stresses, pathogen attacks and ecological factors. Nowadays, they are recognized as defence compounds and attractors of pollinators. Essential oils have been traditionally used in the past years in various cultures for medicinal and health purposes. In recent times due to their well-documented antimicrobial activities, essential oils have consolidated their use in raw and processed food preservation, health and clinical uses.

AIMS OF THE REVIEW

The potential activity of essential oils against the largely diffused Malassezia species on the human skin, which can cause common infections or exacerbate multiple skin disorders, such as P. versicolor, folliculitis, seborrheic dermatitis and dandruff, atopic dermatitis and psoriasis.

MATERIALS AND METHODS

Information on essential oils activity against Malassezia species was obtained from published materials, including books and electronic databases, such as SCI finder, PubMed, Web of Science, ACS, Science Direct, Wiley, Springer, Taylor, J-STAGE and Google Scholar. Search was conducted covering the period from January 2013 to December 2018.

RESULTS

In the in vitro studies diverse methods were used to test the essential oils activity, namely broth microdilution method, which resulted the most used one, followed by agar disk diffusion and vapour phase methods. Essential oils obtained by steam distillation were from different plant genera, Thymus, Artemisia, Malaleuca, Cinnamomun, Ocimum, Zataria, Rosmarinus, Origanum, Syzigium, Foenicolum, Thapsia, Tachyspermum, Myrtus. MIC values were expressed as μg/mL, μL/mL and by inhibition zone (mm) or μL/cm³. All the investigated essential oils were active at the tested conditions. In addition, two clinical studies used essential oils from Cymbopogon citratus and C. flexuosus formulated in shampoo, cream or lotion for the successful treatment of dandruff and P. versicolor.

CONCLUSIONS

Results of these studies indicate worthy prospects for clinical application of essential oils and there is an urgent need to conduct further in vivo studies with large number of patients in order to verify the clinical potential of essential oils against Malassezia species.

Evaluation of antibiotic susceptibility test results: how guilty a laboratory could be?

Background

The selection of an appropriate antimicrobial is a challenging task for clinicians. The Kirby-Bauer disk diffusion method is one of the most widely practiced antimicrobial susceptibility tests (AST). It is affected by many factors among which are the media used. Mueller-Hinton agar (MHA) is the standard medium recommended in guidelines. However, these guidelines are not strictly adhered to in some developing countries.

Objectives

Validation of AST results on nutrient agar (NA) medium used as a substitute for MHA by some microbiology laboratories in Alexandria, Egypt.

Methods

A total of 149 clinical bacterial isolates and 3 reference strains: Staphylococcus aureus (S. aureus) ATCC® 25923, Escherichia coli (E. coli) ATCC®25922, and Pseudomonas aeruginosa (P. aeruginosa) ATCC®27853 were comparatively challenged to antibiotics employing MHA and NA.

Results

All antibiotics-reference bacterial strain challenges on NA compared to MHA were unacceptable (> 3 out of limit zones in 30 consecutive days). Considering clinical isolates, the frequency of very major, major, and minor errors on NA was highest in the case of P. aeruginosa (8.98%, 4.08%, and 14.7% respectively) followed by S. aureus (7.6%, 6%, and 8.8% respectively). On the other hand, the least frequency of errors was in the case of Enterobacteriaceae (0%, 0.4%, and 3.2% respectively).

Conclusions and recommendations

Using NA in AST resulted in multiple errors and the high discrepancy in results compared to MHA making it unreliable for susceptibility testing. MHA should not be replaced by NA in AST. Following guidelines and QC measures for AST must be neither bypassed nor underestimated.

[Antimicrobial susceptibility in isolates of Streptococcus equi subsp. equi from Buenos Aires province, Argentina]

Streptococcus equi subsp. equi is the etiologic agent of strangles, an infectious disease affecting the upper respiratory tract and head and neck lymph nodes of equines. Routine antimicrobial therapy includes penicillin (PEN) as antibiotic of first choice. Streptococci are usually susceptible to PEN and only a few antimicrobial studies had been performed. The aim of this work was to study the antimicrobial susceptibility profile of S. equi from Buenos Aires, Argentina. Ninety-two isolates were studied by the single disk method to PEN, cefotaxime, erythromycin (ERY), tetracycline, enrofloxacin (ENR), trimethoprim sulfamethoxazole (TMS), ciprofloxacin, clindamycin (CLI), streptomycin (STR) and florfenicol. Minimum inhibitory concentration (MIC) to PEN and antibiotics with resistance and intermediate susceptibility were tested. High percentages of susceptibility were obtained by the disk diffusion method and MIC values of PEN, TMS and CLI were found to be under the breakpoint values. Resistant strains of ENR and STR with MIC₅₀, MIC₉₀ and MIC ranges above breakpoints were identified. These findings confirm that PEN may be used empirically because resistant strains were not found in Buenos Aires. Emphasis is placed on the rational use of antibiotics to achieve therapeutic success, to prevent chronicity, recurrence of infections and the emergence of resistance.

Development of an algorithm for phenotypic screening of carbapenemase-producing Enterobacteriaceae in the routine laboratory

BACKGROUND

Carbapenemase-producing Enterobacteriaceae (CPE) are difficult to identify among carbapenem non-susceptible Enterobacteriaceae (NSE). We designed phenotypic strategies giving priority to high sensitivity for screening putative CPE before further testing.

METHODS

Presence of carbapenemase-encoding genes in ertapenem NSE (MIC > 0.5 mg/l) consecutively isolated in 80 French laboratories between November 2011 and April 2012 was determined by the Check-MDR-CT103 array method. Using the Mueller-Hinton (MH) disk diffusion method, clinical diameter breakpoints of carbapenems other than ertapenem, piperazicillin+tazobactam, ticarcillin+clavulanate and cefepime as well as diameter cut-offs for these antibiotics and temocillin were evaluated alone or combined to determine their performances (sensitivity, specificity, positive and negative likelihood ratios) for identifying putative CPE among these ertapenem-NSE isolates. To increase the screening specificity, these antibiotics were also tested on cloxacillin-containing MH when carbapenem NSE isolates belonged to species producing chromosomal cephalosporinase (AmpC) but Escherichia coli.

RESULTS

Out of the 349 ertapenem NSE, 52 (14.9%) were CPE, including 39 producing OXA-48 group carbapenemase, eight KPC and five MBL. A screening strategy based on the following diameter cut offs, ticarcillin+clavulanate <15 mm, temocillin <15 mm, meropenem or imipenem <22 mm, and cefepime <26 mm, showed 100% sensitivity and 68.1% specificity with the better likelihood ratios combination. The specificity increased when a diameter cut-off <32 mm for imipenem (76.1%) or meropenem (78.8%) further tested on cloxacillin-containing MH was added to the previous strategy for AmpC-producing isolates.

CONCLUSION

The proposed strategies that allowed for increasing the likelihood of CPE among ertapenem-NSE isolates should be considered as a surrogate for carbapenemase production before further CPE confirmatory testing.

Synthesis, characterization, antimicrobial activity and carbonic anhydrase enzyme inhibitor effects of salicilaldehyde-N-methyl p-toluenesulfonylhydrazone and its Palladium(II), Cobalt(II) complexes

We report the synthesis of the ligand, salicilaldehyde-N-methyl p-toluenesulfonylhydrazone (salptsmh) derived from p-toluenesulfonicacid-1-methylhydrazide (ptsmh) and its Pd(II) and Co(II) metal complexes were synthesized for the first time. The structure of the ligand and their complexes were investigated using elemental analysis, magnetic susceptibility, molar conductance and spectral (IR, NMR and LC-MS) measurements. Salptsmh has also been characterized by single crystal X-ray diffraction. (1)H and (13)C shielding tensors for crystal structure were calculated with GIAO/DFT/B3LYP/6-311++G(d,p) methods in CDCl3. The complexes were found to have general composition [ML2]. The results of elemental analysis showed 1:2 (metal/ligand) stoichiometry for all the complex. Magnetic and spectral data indicate a square planar geometry for Pd(II) complex and a distorted tetrahedral geometry for Co(II) complexes. The ligand and its metal chelates have been screened for their antimicrobial activities using the disk diffusion method against the selected Gram positive bacteria: Bacillus subtilis, Bacillus cereus, Staphylococcus aureus, Enterococcus faecalis, Gram negative bacteria: Eschericha coli, Pseudomonas aeruginosa, Klebsiella pneumonia. The inhibition activities of these compounds on carbonic anhydrase II (CA II) and carbonic anhydrase I (CA I) have been investigated by comparing IC50 and Ki values and it has been found that Pd(II) complex have more enzyme inhibition efficiency than salptsmh and Co(II) complex.

Evaluation of anti-bacterial and anti-oxidant potential of andrographolide and echiodinin isolated from callus culture of Andrographis paniculata Nees

OBJECTIVE

To evaluate the anti-bacterial and anti-oxidant activity of andrographolide (AND) and echiodinin (ECH) of Andrographis paniculata.

METHODS

In this study, an attempt has been made to demonstrate the anti-microbial and anti-oxidant activity of isolated AND and ECH by broth micro-dilution method and 2,2-diphenyl-2-picryl-hydrazyl (DPPH) assay, respectively. Structure elucidation was determined by electro-spray ionization-MSD, NMR ((1)H and (13)C) and IR spectra.

RESULTS

AND was effective against most of the strains tested including Mycobacterium smegmatis, showing broad spectrum of growth inhibition activity with Minimum inhibitory concentration values against Staphylococcus aureus (100 µg/mL), Streptococcus thermophilus (350 µg/mL) Bacillus subtilis (100 µg/mL), Escherichia coli (50 µg/mL), Mycobacterium smegmatis (200 µg/mL), Klebsiella pneumonia (100 µg/mL), and Pseudomonas aeruginosa (200 µg/mL). ECH showed specific anti-bacterial activity against Staphylococcus aureus, Escherichia coli, Bacillus subtilis and Pseudomonas aeruginosa at a concentration higher than 225 µg/mL. Both AND and ECH were not effective against the two yeast strains, Candida albicans and Saccharomyces cerevisiae tested in this study.

CONCLUSION

This preliminary study showed promising anti-bacterial activity and moderate free radical scavenging activity of AND and ECH, and it may provide the scientific rationale for its popular folklore medicines.

Vibriocidal activity of certain medicinal plants used in Indian folklore medicine by tribals of Mahakoshal region of central India

OBJECTIVES

Screening of the medicinal plants and determination of minimum inhibitory concentration (MIC) against Vibrio cholerae and Vibrio parahaemolyticus.

MATERIALS AND METHODS

A simple in vitro screening assay was employed for the standard strain of Vibrio cholerae, 12 isolates of Vibrio cholerae non-O1, and Vibrio parahaemolyticus. Aqueous and organic solvent extracts of different parts of the plants were investigated by using the disk diffusion method. Extracts from 16 medicinal plants were selected on account of the reported traditional uses for the treatment of cholera and gastrointestinal diseases, and they were assayed for vibriocidal activities.

RESULTS

The different extracts differed significantly in their vibriocidal properties with respect to different solvents. The MIC values of the plant extracts against test bacteria were found to be in the range of 2.5-20 mg/ml.

CONCLUSIONS

The results indicated that Lawsonia inermis, Saraca indica, Syzygium cumini, Terminalia belerica, Allium sativum, and Datura stramonium served as broad-spectrum vibriocidal agents.

STUDY OF YEAST SPECIES ISOLATED FROM CLINICAL SPECIMENS

Opportunistic yeast infections are very common in patients with malignancy or some form of immuno-suppression. Conventional methods of yeast identification are time consuming and labour intensive whereas commercial methods are expensive and beyond reach of most laboratories. Disk diffusion method offers a relatively simple, inexpensive and rapid method of identifying yeasts. 63 specimens of yeasts were isolated and identified from 68 patients by conventional methods. With disk diffusion method 54 of 63 species (85.7%) gave the same identification.