Minimum Inhibitory Concentration Of Oxytetracycline Research Articles

The fly route of extended-spectrum-β-lactamase-producing Enterobacteriaceae dissemination in a cattle farm: from the ecosystem to the molecular scale

IntroductionThis study aimed to understand the origin and to explain the maintenance of extended-spectrum β-lactamase (ESBL) Enterobacteriaceae isolated from food-producing animals in a third-generation cephalosporin (3GC)-free farm.MethodsCulture and molecular approaches were used to test molecules other than 3GC such as antibiotics (tetracycline and oxytetracycline), antiparasitics (ivermectin, flumethrin, fenbendazol, and amitraz), heavy metal [arsenic, HNO3, aluminum, HNO3, cadmium (CdSO4), zinc (ZnCl2), copper (CuSO4), iron (FeCl3), and aluminum (Al2SO4)], and antioxidant (butylated hydroxytoluene) as sources of selective pressure. Whole-genome sequencing using short read (Illumina™) and long read (Nanopore™) technologies was performed on 34 genomes. In silico gene screening and comparative analyses were used to characterize the genetic determinants of resistance, their mobility, and the genomic relatedness among isolates.ResultsOur analysis unveiled a low diversity among the animal ESBL-producing strains. Notably, E. coli ST3268 was recurrently isolated from both flies (n = 9) and cattle (n = 5). These E. coli ST3268/blaCTX-M-15/blaTEM-1B have accumulated multiple plasmids and genes, thereby representing a reservoir of resistance and virulence factors. Our findings suggest that flies could act as effective mechanical vectors for antimicrobial gene transfer and are capable of transporting resistant bacteria across different environments and to multiple hosts, facilitating the spread of pathogenic traits. A significantly higher mean minimum inhibitory concentration of oxytetracycline (841.4 ± 323.5 mg/L vs. 36.0 ± 52.6 mg/L, p = 0.0022) in ESBL E. coli than in non-ESBL E. coli and blaCTX-M-15 gene overexpression in oxytetracycline-treated vs. untreated ESBL E. coli (RQOxy = 3.593, p = 0.024) confirmed oxytetracycline as a source of selective pressure in ESBL E. coli.DiscussionThe occurrence of ESBL E. coli in a farm without 3GC use is probably due to an as yet undefined human origin of Enterobacteriaceae blaCTX-M-15 gene transmission to animals in close contact with cattle farm workers and the maintenance of the local ESBL E. coli reservoir by a high fly diversity and oxytetracycline selective pressure. These findings highlight the critical need for stringent vector control to mitigate antimicrobial resistance spread for preserving public health. Addressing this issue necessitates a multifaceted approach combining microbial genetics, vector ecology, and farm management practices.

Oxytetracycline resistance of Melissococcus plutonius strains in Japan

European foulbrood caused by the Gram-positive lanceolate coccus, Melissococcus plutonius, is a major bacterial infection of honey bee brood. Oxytetracycline (OTC) has been used to combat this disease in some countries. Although OTC resistance was not previously reported despite its long-term use, the first case was finally detected in an M. plutonius strain isolated in Canada in 2019. In Japan, OTC has not been approved for use in the control of any honey bee diseases. However, after testing 77 M. plutonius strains isolated in Japan between the 1980s and 2010s, we identified four OTC-resistant strains with a minimum inhibitory concentration of OTC on agar medium of 16 µg/ml. The four strains were isolated in 2008 (1 strain), 2013 (1 strain), and 2015 (2 strains); i.e., before the Canadian OTC-resistant isolate. These results provide insights into the mechanisms underlying the development of OTC-resistant M. plutonius.

New host record of Vibrio anguillarum associated with haemorrhagic septicaemia in golden mahseer, Tor putitora (Hamilton, 1822) from India

Vibrio strains (n=5) were isolated from a pooled liver samples of golden mahseer, Torputitora (n=10) showing symptoms of hemorrhagic septicemia in cultured conditions. From biochemical analysis, partial PCR amplification of 16S rRNA genes (~1400bp) and sequencing, the isolates were identified as Vibrio anguillarum. One of the 5 isolates was designated as a strain number MHJL 248 and submitted to the NCBI (MN900589). The phylogenetic analysis of the V. anguillarum MHJL 248 showed >99% similarity with V. anguillarum strain HA (KF413427). V. anguillarum MHJL 248 was positive to arginine, oxidase, catalase, string test, ONPG, siderophore, sensitive to O/129 vibriostatic disc (10 and 150 pg) grown on medium containing varying NaCl concentrations (0.5% to 2.0%), showing intermediate resistance to ampicillin (10 pg) and a-hemolytic on 5% sheep blood agar plate. The major histopathological changes recorded in the kidney, liver, gill and intestine collected from natural infection were cellular degeneration, necrosis, cytoplasmic vacuolation, degeneration of glomerulus, dilation and increasing Bowman's space and glomerular contraction. Vibrio anguillarum MHJL 248 was found resistant to cefoxitin (30 pg), ciprofloxacin (5 pg), imipenem (10 pg), levofloxacin (5 pg) and nalidixic acid (30 pg). The minimum inhibitory concentration of oxytetracycline, erythromycin and florfenicol against V. anguillarum MHJL 248 were 16, 0.5 and 0.125 pg mL−1, respectively. Transmission electron microscopy (negatively stained) of V. anguillarum MHJL 248 demonstrated the presence of monotrichous polar flagellum and capsular structure that can be correlated to the pathogenicity of the bacterium. This is the first case of a new host (T. putitora) record of V. anguillarum infection in coldwater aquaculture practices in India. Seeing the severity of infection of V. anguillarum in aquaculture worldwide, further study needs to be focused on the development of efficient measures to control its infection in coldwater aquaculture.

Triclosan exposure induces varying extent of reversible antimicrobial resistance in Aeromonas hydrophila and Edwardsiella tarda

Triclosan (TCS) is a biocide commonly used in household and personal care items to prevent the microbial growth and is currently considered as an emerging pollutant. It has a ubiquitous distribution which can substantially contribute towards antimicrobial resistance. The present study was designed to evaluate the effect of different concentrations of TCS exposure on the antibiotic sensitivity of aquatic bacteria. Aeromonas hydrophila ATCC® 49140™ and Edwardsiella tarda ATCC® 15947™ exposed to TCS for short (30 min) and long duration (serial passages). The agar-disc diffusion assay during the serial passages of TCS exposure and subsequent exposure withdrawal showed clinically insignificant changes in the zone of inhibition for six selected antibiotics in both bacterial strains at all exposure concentrations. Four folds concentration-dependent increase in the minimum inhibitory concentrations (MICs) of TCS was observed in both the strains following TCS exposure. Similarly, a concentration-dependent increase in the MICs of oxytetracycline (OTC) up to 4 folds in A. hydrophila, and up to 8 folds in E. tarda, was also documented during the TCS exposure. In all the cases, withdrawal of TCS exposure effectively reduced the MICs of TCS and OTC in blank passages suggesting a decline in acquired resistance. The frequencies of mutation during 30 min TCS exposure for E. tarda and A. hydrophila ranged between >10−6 and 10−7 levels. Nevertheless, the TCS exposure did not cause any detectable mutation on the fabV gene of A. hydrophila indicating that the TCS may elicit phenotypic adaptation or other resistance mechanism. Although the reduction in MICs due to exposure withdrawal did not restore the bacterial susceptibility up to the initial level, the study proved that the reduced TCS use could significantly help reduce the antimicrobial-resistance and cross-resistance in pathogenic bacteria.

Diversity and characterization of oxytetracycline-resistant bacteria associated with non-native species, white-leg shrimp (Litopenaeus vannamei), and native species, black tiger shrimp (Penaeus monodon), intensively cultured in Thailand

This study aimed at surveying prevalence of oxytetracycline (OTC)-resistant bacteria in the white-leg shrimp Litopenaeus vannamei, and the black tiger shrimp Penaeus monodon, intensively cultured in Thailand. We investigated the phylogenetic diversity of the bacterial isolates, as well as the minimum inhibitory concentration (MIC) of OTC, the occurrence of major OTC-resistant genes and multiple-antibiotic resistance in the isolates. Shrimps were collected from culture ponds, and the homogenates of whole bodies were plated on tryptic soy agar supplemented with or without OTC. Percentages of OTC-resistant bacteria were 0·3-52·1% in white-leg samples and 0·008-22·3% in black tiger samples. Analyses of 16S rDNA sequences indicated that most OTC-resistant isolates were closely related to Aeromonas spp. and Lactococcus garvieae. MICs of OTC were 4-128 μg ml(-1) in the OTC-resistant aeromonads and 128-256 μg ml(-1) in OTC-resistant L. garvieae. OTC resistance was found to be conferred by the genes tet(A), tet(C), tet(D), tet(E), tet(M) and tet(S), detected either singly or in pairs. No resistance to ceftazidime, imipenem or chloramphenicol was observed in any isolate. Both species of shrimp are associated with OTC-resistant bacteria, occasionally at high densities exceeding 10(6) cfu g(-1). The associated bacteria, predominantly Lactococcus and Aeromonas genera, are potential pathogens and are reservoirs of a variety of OTC-resistant genes. Cultured shrimps can be vehicle to carry OTC-resistant bacteria to domestic and foreign consumers via the food chain. Very low populations of OTC-resistant bacteria observed in the several ponds suggest that levels of the resistant bacteria are artificially high and should be reduced in farmed shrimps.

Diversity and antimicrobial susceptibility of oxytetracycline-resistant isolates of Stenotrophomonas sp. and Serratia sp. associated with Costa Rican crops

To ameliorate the identification, evaluate the diversity, and determine the antimicrobial sensitivity of 19 oxytetracycline-resistant isolates of Stenotrophomonas sp. and Serratia sp. associated with Costa Rican crops. Phenotypical, chemotaxonomical, and molecular data allocated most isolates to the species Sten. maltophilia and Ser. marcescens. The API profiles, antimicrobial resistance patterns (ATB system), and BOX-polymerase chain reaction (PCR) genomic fingerprints of isolates of Stenotrophomonas sp. exhibited a higher degree of heterogeneity than those obtained for the isolates of Serratia sp. The former group of bacteria exhibited multiresistance to antimicrobials. In contrast, isolates of Serratia sp. were sensitive to the majority of the drugs tested. Changes in the results of the antibiograms throughout incubation, which indicate an induction of tolerance, were observed for isolates of both the species. Minimum inhibitory concentration of oxytetracycline, determined using E-test stripes, were rather elevated. The occurrence of two species of opportunistic pathogens in crop-associated materials poses a risk to consumers in the community. The phenotypic and genotypic data presented could support epidemiologist and physicians dealing with infections caused by environmental strains of these taxa.

ANTIPARASITIC, ANTIBACTERIAL, AND ANTIFUNGAL ACTIVITIES DERIVED FROM A TERMINALIA CATAPPA SOLUTION AGAINST SOME TILAPIA (OREOCHROMIS NILOTICUS) PATHOGENS

ANTIPARASITIC, ANTIBACTERIAL, AND ANTIFUNGAL ACTIVITIES DERIVED FROM A TERMINALIA CATAPPA SOLUTION AGAINST SOME TILAPIA (OREOCHROMIS NILOTICUS) PATHOGENS

Oxytetracycline Activity in Honeybee Larvae Following Hive Treatment with Various Oxytetracycline Preparations

SummaryForty-seven hives were treated with various preparations of Oxytetracycline (OTC). OTC activity was detected in larval samples collected from all treated hives. The peak concentration was always above the minimum inhibitory concentration of OTC to Melissococcus pluton which was determined to be 3·8 μg/ml. The period of detectable OTC ranged from 1 to 9 days and the highest OTC larval concentration in hives following treatment varied from 10 to 184 μg/g of larval material.

Fish pasteurellosis of cultured striped bass ( Morone saxatilis) in coastal Alabama

The first reported epizootic of fish pasteurellosis caused by the bacterium Pasteurella piscicida in a cultured population of fish in the United States is described. The epizootic occurred in populations of striped bass ( Morone saxatilis) cultured in earthen, brackish-water ponds at the Claude Peteet Mariculture Center, Gulf Shores, AL. Losses of approximately 49 000 fingerlings (80% of the existing stock) occurred over a 3-week period. Oxytetracycline was administered via the feed within 48 h of the onset of mortality. Oxytetracycline residues in tissues of fish sampled during the treatment period were quantitated by a fluorometric method. The isolated bacterium was characterized biochemically and serologically. The sensitivity of the bacterium to various antibiotics was determined, and the minimum inhibitory concentration of oxytetracycline was determined to be 0.25 ppm. The salient histopathological features of the disease in striped bass are described.

Transmissible drug resistance in human and animal strains of Enterobacteriaceae and Pseudomonas aeruginosa

In an investigation carried out over a period of six months, 53 strains of Enterobacteriaceae and nine strains of Pseudomonas aeruginosa were examined for antibiotic resistance and transmissible drug resistance factor. Seventeen antibiotic resistance patterns were found among 51 drug resistant Enterobacteriaceae. Of the 62 strains, 23 were capable of transferring a part or all of the antibiotic resistance pattern to sensitive Escherichia coli. The P aeruginosa isolated from both man and piglets harboured R-factors which were transferable at high frequencies to the sensitive recipients, while only one of the six single resistant E coli isolated from piglets transferred resistance to the sensitive recipients. The minimum inhibitory concentrations of oxytetracycline, ampicillin, chloramphenicol, sulphadimidine and streptomycin of the resistant E coli, P aeruginosa, Salmonella spp and Proteus spp were 500 to 625, 62 to 500, 500 to 625, 500 and 7.8 to 500 micrograms/ml, respectively.

Vaginal oxytetracycline concentrations.

Although tetracycline preparations are widely used in departments of genitourinary medicine, or sexually transmitted diseases clinics, little is known of the concentrations of these preparations in genital secretions. For this reason a microbiological method was used for estimating oxytetracycline concentrations in vaginal secretions. These concentrations varied from 0.6 to 6.5 microgram/ml in 19 women who had had sexual contact with a man with non-specific urethritis and who were taking oxytetracycline dihydrate 250 mg four times daily. They were well in excess of the minimum inhibitory concentration of oxytetracycline (0.2 microgram/ml) for the strains of Chlamydia trachomatis isolated from the patients with positive culture results. Thus, oxytetracycline 250 mg four times daily appears to be a satisfactory regimen for the treatment of chlamydial genital infection in women.