Essential oil of clove, dispersed (0.4% v/v) in a concentrated sugar solution, had a marked germicidal effect against various bacteria and Candida albicans. Staphylococcus aureus (five strains), Klebsiella pneumoniae, Pseudomonas aeruginosa, Clostridium perfringens, and Escherichia coli inoculated at a level of 10(7) cfu/ml, and C. albicans (inoculum 4.0 x 10(5) cfu/ml) were killed (greater than 99.999%) after 2-7 min in a laboratory broth supplemented with 63% (v/w) of sugar, and containing 0.4% (v/w) of essential oil of clove. Added organic matter (i.e. human or bovine serum) did not impair its antimicrobial activity. Sugar was not necessary for the antimicrobial activity of clove oil, but the concentrated sugar solution provided a good vehicle for obtaining an oil dispersion that is relatively stable for certain practical applications.
Clove essential oil, used as an antiseptic in oral infections, inhibits Gram-negative and Gram-positive bacteria as well as yeast. The influence of clove essential oil concentration, temperature and organic matter, in the antimicrobial activity of clove essential oil, was studied in this paper, through the determination of bacterial death kinetics. Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa were the microorganisms selected for a biological test. To determine the temperature effect, they were assayed at 21° and 37° C. The concentration coefficient was determined with 0.4%, and 0.2% of essential oil. The influence of the presence of organic matter was determined with 0.4% of essential oil. The results obtained demonstrated that Escherichia coli were more sensitive even though the essential oil exerted a satisfactory action in three cases. In the three microbial species, 0.4% of essential oil at 21° C have reduced the bacterial population in 5 logarithmic orders. Organic matter reduces the antibacterial activity even though the bactericide efficacy was not lost. Clove essential oil can be considered as a potential antimicrobial agent for external use
Large quantities of disinfectants are used in hospitals, externally on human skin or to eliminate microorganisms from inanimate objects. After use, residual quantities of these products reach the wastewater, exposing the bacteria that survive in hospital wastewaters to a wide range of biocides that could act as a selective pressure for the development of resistance. Increasing attention has been directed recently to the resistance of bacteria to disinfectants. The aim of this paper was to determine the disinfectant bacterial resistance pattern of the microflora released to the urban sewer system by hospital effluents. The characterization of the waste water microflora was performed by determination of the CFU of heterotrophic bacteria, fecal indicator bacteria, Pseudomonas sp. and Staphylococcus sp., in a Buenos Aires hospital effluent. The bacterial resistance to the disinfectants more frequently used in the hospital practice, glutaraldehyde, chlorhexidine and povidoneiodine, was then evaluated. Disinfectant resistant bacterial strains were isolated and typified. Between 10 3 and 10 6 chlorexidine resistant bacteria/100 mL were isolated from the samples. Bacteria resistant to other disinfectants ranged between 10 3 and 10 4 /100 mL. The bacterial population resistant to desinfectants to was mainly composed by Enterobacteriaceae, Staphylococcus spp, and Bacillus spp, which are highly associated to nosocomial infections. The results obtained show that the hospital effluents are of importance in the bacterial resistance selection process, particularly in the case of disinfectants.
The effect of temperature, concentration and contact time on the fungicidal effect of clove oleoresin dispersed in a concentrated sugar solution at 21 and 37ºC, and clove oleoresin at 0.2 to 0.8% (v/v) was studied. The test microorganisms were Candida albicans, Penicillium citrinum, Aspergillus niger and Trichophyton mentagrophytes. The fungicidal effect was enhanced at 37ºC; at this temperature short contact times (e.g. 1 min.) were enough to eliminate a microbial inoculum of 10 6 c.f.u./ml of C. albicans. Although clove oleoresin caused important lethal effect, P. citrinum and A. niger were more resistant. After 60 minutes, clove oleoresin dispersed (0.4% v/v) in concentrated sugar solution caused a 99.6% reduction of the initial population (10 6 c.f.u./ml) of Trichophyton mentagrophytes. The fungicidal activity of clove-sugar on C. albicans, after 2 min contact, was similar to that presented by disinfectants commonly used in hospitals, such as povidone-iodine and chloroxylenol.
Untreated wastewater is a reservoir for multidrug-resistant bacteria, but its role in the spread of antibiotic resistance in the human population remains poorly investigated. In this study, we isolated a KPC-2-producing ST2787 Klebsiella quasipneumoniae subsp. quasipneumoniae (WW14A), recovered from raw sewage at a wastewater treatment plant in Argentina in 2018 and determined its complete genome sequence. Strain WW14A was resistant to all β-lactams, ciprofloxacin and amikacin. A core genome phylogenetic analysis indicated that WW14A was closely related to a GES-5-producing Taiwanese strain isolated from hospital wastewater in 2015 and it was clearly distinct from strains isolated recently in Argentina and Brazil. Interestingly, blaKPC-2 was harbored by a recently described IncP-6 broad-spectrum plasmid which was sporadically reported worldwide and had never been reported before in Argentina. We investigated the presence of the IncP-6 replicon in isolates obtained from the same sampling and found a novel non-typable/IncP-6 hybrid plasmid in a newly assigned ST1407 Enterobacter asburiae (WW19C) also harboring blaKPC-2. Nanopore sequencing and hybrid assembly of strains WW14A and WW19C revealed that both IncP-6 plasmids shared 72% of coverage (~20 kb), with 99.99% of sequence similarity and each one also presented uniquely combined regions that were derived from other plasmids recently reported in different countries of South America, Asia, and Europe. The region harboring the carbapenem resistance gene (~11 kb) in both plasmids contained a Tn3 transposon disrupted by a Tn3-ISApu-flanked element and the core sequence was composed by ΔISKpn6/blaKPC-2/ΔblaTEM-1/ISKpn27. Both strains also carried genes conferring resistance to heavy metals (e.g., arsenic, mercury, lead, cadmium, copper), pesticides (e.g., glyphosate), disinfectants, and several virulence-related genes, posing a potential pathogenic risk in the case of infections. This is the first study documenting blaKPC-2 associated with IncP-6 plasmids in K. quasipneumoniae and Enterobacter cloacae complex from wastewater in Argentina and highlights the circulation of IncP-6 plasmids as potential reservoirs of blaKPC-2 in the environment.
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