chlortetracycline and Gram-Negative-Bacterial-Infections

In recent years, Aeromonas hydrophila, which has been classified as a food borne pathogen, has presented with increased levels of antibiotic resistance, with the mechanisms of this resistance being poorly understood. In this study, iTRAQ coupled mass spectrometry was employed to compare differentially expressed proteins in chlortetracycline (CTC) resistant A. hydrophila relative to a control strain. Result showed that a total of 234 differential proteins including 151 down-regulated and 83 up-regulated were identified in chlortetracycline resistance strain. Bioinformatics analysis showed that chemotaxis related proteins, such as CheA-2, CheR-3, CheW-2, EnvZ, PolA, FliS and FliG were down-regulated in addition to previously reported tricarboxylic acid cycle (TCA) related proteins also being down-regulated. A subset of identified differentially expressed proteins was then further validated via Western blotting. Exogenous metabolite combined with CTC further enhanced the bacterial susceptibilities to CTC in A. hydrophila. Furthermore, a bacterial survival capability assay showed that several chemotaxis related mutants, such as ΔcheR-3 and ΔAHA_0305, may affect the antimicrobial susceptibility of A. hydrophila. Overall, these findings contribute to a further understanding of the mechanism of CTC resistance in A. hydrophila and may contribute to the development of more effective future treatments.. A. hydrophila is a well-known fish pathogenic bacterium and has presented with increasing levels of antibiotic resistance, with the mechanisms of this resistance being poorly understood. Our current study compared the differentially expression proteins between chlortetracycline (CTC) resistant and control stains via an iTARQ-based quantitative proteomics method. Chemotaxis related proteins were down-regulated in CTC resistant strain but exogenous metabolite addition increased bacterial susceptibility in A.hydrophila. Significantly, chemotaxis related genes depletion affected antimicrobial susceptibilities of A.hydrophila indicating the role of chemotaxis process in antibiotics resistance.

Topics: Aeromonas hydrophila; Anti-Bacterial Agents; Bacterial Proteins; Chemotaxis; Chlortetracycline; Drug Resistance, Microbial; Gene Expression Regulation, Bacterial; Gram-Negative Bacterial Infections; Proteomics

Antibiotic fitness and acquired resistance are the two critical factors when bacteria respond to antibiotics, and the correlations and mechanisms between these two factors remain largely unknown. In this study, a TMT-labeling-based quantitative proteomics method was used to compare the differential expression of proteins between the fitness and acquired resistance to chlortetracycline in Aeromonas hydrophila biofilm. Bioinformatics analysis showed that translation-related ribosomal proteins, such as 30s ribosome subunits, increased in both factors; fatty acid biosynthesis related proteins, such as FabB, FabD, FabG, AccA, and AccD, increased in biofilm fitness, and some pathways (including propanoate-metabolism-related protein, such as PrpB, AtoB, PflB, AcsA, PrpD, and GabT) displayed decreased abundance in acquired resistance biofilm. The varieties of selected proteins involved in fatty acid biosynthesis and propanoate metabolism were further validated by q-PCR assay or Western blotting. Furthermore, the antibiotic-resistance-function assays showed that fatty-acid biosynthesis should be a protective antibiotics-resistance mechanism and a cocktail of chlortetracycline and triclosan, a fatty-acid-biosynthesis inhibitor, exhibited more efficient antimicrobial capability than did each antibiotic individually on biofilm, specifically on chlortetracycline-sensitive biofilm. We therefore demonstrate that the up-regulation of fatty acid biosynthesis may play an important role in antibiotic resistance and suggest that a cocktail of chlortetracycline and triclosan may be a potential cocktail therapy for pathogenic infections in biofilm.

Topics: Aeromonas hydrophila; Anti-Bacterial Agents; Bacterial Proteins; Biofilms; Chlortetracycline; Drug Resistance, Bacterial; Drug Therapy, Combination; Fatty Acids; Gram-Negative Bacterial Infections; Propionates; Proteomics; Triclosan

Dichelobacter nodosus is the main causative agent of ovine footrot, and there are strong indications that the bacterium can be transferred to cattle grazing on the same pasture as sheep. The aim of this study was to investigate if benign and virulent D. nodosus strains isolated from sheep can be transferred to the interdigital skin of cattle under experimental conditions. Further, we wanted to observe the impact of such infection on bovine foot health, and test the effect of topical chlortetracycline (Cyclo spray(®): Eurovet) on the infection.. Six heifers were included in the study. After an initial 18-day maceration period, three heifers were inoculated on one single foot with a benign strain and three with a virulent strain by adding bacterial suspension in a bandage. The bandages were left on for 17 days, and when removed, D. nodosus was isolated from all six heifers. All six heifers developed interdigital dermatitis. In five of the heifers D. nodosus organisms were demonstrated within the epidermis. Twenty-four days after treatment with chlortetracycline all heifers were negative by cultivation, but tested positive for D. nodosus by polymerase chain reaction (PCR). Two of the six heifers still tested positive for D. nodosus by PCR 49 days after treatment. After 70 days, all heifers tested negative for D. nodosus.. This study shows that both virulent and benign D. nodosus strains originating from sheep can be transferred to naïve heifers under experimental conditions. Further, the study supports the hypothesis that infections with virulent D. nodosus in cattle are associated with interdigital dermatitis. No conclusion regarding the treatment of D. nodosus infection with chlortetracycline was possible.

Topics: Animals; Anti-Bacterial Agents; Cattle; Cattle Diseases; Chlortetracycline; Dichelobacter nodosus; Digital Dermatitis; Female; Foot Rot; Gram-Negative Bacterial Infections; Real-Time Polymerase Chain Reaction; RNA, Ribosomal, 16S; Sheep; Sheep Diseases; Sheep, Domestic

The effects of continuous oral administration of antibiotics in mice were investigated. Sulfamerazine, ampicillin, and chlortetracycline were tested at a rate of 500 mg/L of drinking water. Mice were infected by intranasal inoculation with 10(6) bacilli of the SMR strain of cilia-associated respiratory (CAR) bacillus. The mice were treated with the antibiotics starting 1 week before, 1 week after, or 4 weeks after the inoculation, for 5, 3, or 4 weeks respectively, then were examined. The infected mice lost body weight, and this loss was prevented or regained by all of the antibiotic treatments. Serologically no antibodies were detectable in the mice administered sulfamerazine starting 1 week before the inoculation. Mice administered sulfamerazine starting 1 week after the inoculation and ampicillin or chlortetracycline starting 1 week before or after the inoculation yielded a low titer of antibodies compared with nontreated infected mice. Mice administered antibiotics starting 4 weeks after the inoculation yielded the same titer of antibodies as nontreated infected mice. No pathologic respiratory tract lesions were observed in mice administered sulfamerazine starting 1 week before the inoculation. Mice administered sulfamerazine starting 1 week after the inoculation or ampicillin starting 1 week before or after the inoculation had slight peribronchitis without CAR bacillus colonization. Mice administered chlortetracycline, starting either 1 week before or after inoculation, developed peribronchitis, with colonization of the bacillus on the airway mucosa. In mice medicated starting 4 weeks after the inoculation, respiratory tract lesions developed, but their severity was reduced. The airway mucosa in mice treated with chlortetracycline was associated with the CAR bacillus but not in mice treated with sulfamerazine and ampicillin. These findings suggest that prevention and eradication of CAR bacillus infection is possible by treatment with sulfamerazine.

Topics: Ampicillin; Animals; Anti-Bacterial Agents; Antibodies, Bacterial; Body Weight; Bronchi; Chlortetracycline; Drug Administration Schedule; Female; Gram-Negative Bacteria; Gram-Negative Bacterial Infections; Mice; Mice, Inbred BALB C; Respiratory System; Respiratory Tract Infections; Rodent Diseases; Specific Pathogen-Free Organisms; Sulfamethazine; Time Factors