High-dose Antibiotics Research Articles

Preparation and Physicochemical Characterization of Hyaluronic Acid-Lysine Nanogels Containing Serratiopeptidase to Control Biofilm Formation

Remarkable resistance of bacterial biofilms to high doses of antimicrobials and antibiotics is one of their main challenges. Encapsulation of proteolytic enzymes is one of the suggested strategies to tackle this problem. In this regard, the antibacterial and anti-biofilm activity of biocompatible hyaluronic acid- Lysine nanogels containing serratiopeptidase (SRP-loaded HA-Lys nanogel) was assessed against P. aeruginosa and S. aureus strains. SRP-loaded HA-Lys nanogel was prepared using dropping method and optimized by Box-Behnken experimental design. These formulations were studied for physical characterization, release profile, stability, bioactivity, and anti-biofilm effects. The particle size, polydispersity index (PDI), and surface charge were measured by Zetasizer Nano ZS. The average particle size and zeta potential of the optimum sample were 156 nm and -14.1 mV, respectively. SRP release showed an initial burst followed by sustained release and the highest release was around 77%. Enzyme biological activity data revealed the higher efficiency of free SRP compared to SRP-loaded HA-Lys nanogel. The time-kill assay showed that both forms of SRP-loaded HA-Lys nanogel and blank HA-Lys nanogel showed significant antimicrobial activity against examined bacteria in comparison to the free enzyme. The obtained results demonstrated improved anti-biofilm efficacy and down regulation of tested biofilm genes for both SRP-loaded HA-Lys nanogel 100% and blank HA-Lys nanogel 100% compared to SRP 100%.

Optimization of ultrasound contrast agent and treatment duration for drug delivery to methicillin-resistant Staphylococcus aureus diabetic wound biofilms in mice

Chronic wounds are frequently infected with bacterial biofilms which pose a barrier to drug diffusion, drug uptake, and facilitate drug tolerance, thereby prolonging the healing process in chronic wounds and increasing the likelihood of relapse. A major contributor to relapse is persister cells, a subset resilient to high antibiotic doses. Previous work by our group showcased significantly improved gentamicin efficacy in a diabetic murine wound model using ultrasound, nanodroplets, and an anti-persister drug. Here, we aim to optimize nanodroplet formulation for persister cell targeting and treatment duration for clinical translation. In a methicillin-resistant Staphylococcus aureus (MRSA) diabetic wound model in SKH-1 hairless mice (n = 5), wounds were treated twice daily with gentamicin, ultrasound, and nanodroplets containing oxygen or palmitoleic acid (PA). These components aim to increase oxygenation and enhance persister uptake, respectively. Additionally, treatments with gentamicin, PA nanodroplets, and ultrasound for 2, 5, and 10 minutes were investigated (n = 3). Preliminary findings indicate PA most effectively potentiates antibiotic activity, 10- minute treatments improve efficacy by 1-log compared to 5-minutes, and 2-minute treatments achieve comparable efficacy to 5-minutes. These initial findings suggest a promising strategy for enhancing antibiotic efficacy and targeting persister cells in biofilms, with consideration for resource-efficient treatment times for clinical application.

Brain abscess originating from odontogenic maxillofacial fascial space abscess : report of two cases

Brain abscesses caused by dental infections are rare but potentially fatal infections with a high mortality rate. Early diagnosis and treatment are crucial, but diagnosing them is not straightforward. Various mechanisms exist through which oral bacteria can spread to the central nervous system, with hematogenous dissemination being considered the most important pathophysiological mechanism. In this report, two cases of brain abscess originating from maxillofacial fascial space infec-tion will be presented. In the first case, the infection originating from the right side secondary to the left brain abscess, and in the second case, the infection originating from the left side led to a secondary infection in the left brain abscess. In both cases, the source of the infection was traced back to dental issues. The patients showed improvement through long-term high dose antibiotic therapy and surgical treatment by oral & maxillofacial surgeon and neurosurgeon.

Factors Associated with Inappropriate Use of Antibiotics Among Animal Health Professionals in Selected Districts of Rwanda, 2021

BackgroundAntibiotic resistance is a global health concern. Humans can acquire antibiotic resistance through human-to-human transmission, from the environment, via the food chain, and through the contact with animals. The National Action Plan on antimicrobial resistance 2020–2024 highlights the prudent use of antibiotics in veterinary activities as the key element in keeping antibiotics effective. We determined the factors associated with misuse of antibiotics among animal health professionals in Rwanda.MethodsThis was a cross-sectional study that enrolled animal health field professionals from five districts, where stratified random sampling was used to select one district by each province of Rwanda. Structured questions were used during face-to-face interviews. The misuse of antibiotics was defined as the use of antibiotics for reasons other than treatment, the non-completion of required courses, or the use of a high dose (i.e., an overdose) of antibiotics. We collected socio-demographic data of respondents, as well as elementary knowledge and perceptions on veterinary antibiotics and antibiotic resistance. A backward stepwise logistic regression model was used to identify the factors that were predictive of the inappropriate use of antibiotics.ResultsThere were 256 respondents to the survey. Of those, 198 were male and 58 were female. Almost three quarters of respondents (n = 174/256; 68%) reported the misuse of antibiotics at least once in the previous 12 months. The final logistic regression analysis identified the following factors to be predictive of antibiotics misuse: aged ≤ 24 years (aOR 0.92; 95% CI [0.88, 0.96]; p < 0.001); low trust in veterinary antibiotics available in the local market (aOR 8.45; 95% CI [4.18, 17.07]; p < 0.01), insufficient knowledge about basic understanding of antibiotics and antibiotic resistance (aOR 2.78; 95% CI [1.38, 5.58], p < 0.01) and not acquiring any continuing education (aOR 1.97; 95% CI [1.02, 4.19]; p = 0.04).ConclusionsThis study identified inadequate perceptions of proper antibiotic use among animal health professionals. There is a need for continuous education on appropriate antibiotic use among animal health professionals to lessen the negative impact of antibiotic resistance on public health security.

Dermatomyositis with multiple organ involvement: a case report and literature review

Background: Dermatomyositis (DM) is a chronic autoimmune disorder characterized by muscle and skin inflammation, a part of the idiopathic inflammatory myositis (IIM). Even though the disease is idiopathic, there are multifactorial factors related to dermatomyositis. This care report aimed to describe a DM case in a male patient to increase the knowledge and management of DM patients. Case description: A 44-year-old Filipino male was referred to the emergency department (ED) of Siloam Hospital Mataram complaining of muscle pain and weakness with skin rashes 3 weeks before admission. Before the skin rash started, he had enlarged femoral lymph nodes in both thighs. The patient was afebrile with normal vital signs and was prescribed ibuprofen and amoxicillin. After that, he experienced skin rashes around his neck and the back of his ears with minimal pruritus. The symptoms worsened, making him unable to open his mouth and hard to breathe. In the ED, he also threw up dark-colored blood twice. Supporting examination showed elevated transaminase, increased LDH, and creatinine kinase. Biopsy results showed a histologic pattern of dermatomyositis. During hospitalization, he received a high-dose systemic steroid, antibiotic, and symptomatic treatment. He was discharged with a good outcome and planned to continue medical treatment in his country. Conclusion: Dermatomyositis is an idiopathic autoimmune disease involving skin and internal organs. It is a multifactorial disease yet with unclear etiopathogenesis. Specific treatment guidelines for DM are not yet established, but initial systemic corticosteroid and additional steroid-sparring agents may exhibit good outcomes.

Investigating the effects of zinc oxide and titanium dioxide nanoparticles on the formation of biofilm and persister cells in Klebsiella pneumoniae.

The biofilm formation in klebsiella pneumoniae isolates poses a significant problem as it can result in treatment failure and the development of chronic infections. These biofilms act as protective barriers, rendering the bacteria resistant to antibiotics. Additionally, persister cells, which make up a small fraction of the bacterial population, have the ability to enter a dormant state after treatment with high doses of antibiotics. These persister cells play a crucial role in the high level of biofilm-mediated tolerance to antibiotics. The present study aimed to investigate the impact of Zinc oxide (ZnO) and titanium dioxide (TiO2) nanoparticles on the formation of biofilm and persister cells in K. pneumoniae. The minimum inhibitory concentration (MIC) of colistin in K. pneumoniae ATCC 13883 was determined using the microdilution method. The formation of persister cells was evaluated by introducing sub-MIC of colistin. Subsequently, the MIC of ZnO NPs and TiO2 NPs in these persister cells was assessed using the microdilution method. Furthermore, the effects of nanoparticles on the expression levels of biofilm-associated genes were analyzed using real-time polymer chain reaction (PCR). The MIC values for colistin, ZnO, and TiO2 were determined at 2, 12.5, and 6.25 μg/mL, respectively. In the presence of nanoparticles, biofilm formation decreased. Real-time PCR results showed the messenger RNA (mRNA) level of mrkH and fimH were decreased and the expression of luxS and mazF were increased. Biofilm formation of K. pneumoniae ATCC 1383 was inhibited in response to nanoparticles. According to the results of the present study use of nanoparticles may help control multidrug-resistant (MDR) infections in hospitalized patients.

Review Article] Review of Streptococcus pyogenes

_Streptococcus pyogenes_, commonly known as group A _Streptococcus_ (GAS), is a bacterium that causes a wide range of clinical diseases. Its ability to cause superficial, invasive, and even life-threatening infections makes it an important pathogen that requires prompt diagnosis and treatment. It is a Gram-positive bacterium. These infections involve the bloodstream and can lead to sepsis, toxic shock syndrome, pneumonia, and necrotizing fasciitis. These infections require immediate medical attention and treatment with high doses of antibiotics and aggressive supportive care. _S. pyogenes_ is a bacterium that causes a wide range of clinical diseases. Its ability to cause superficial, invasive, and even life-threatening infections makes it an important pathogen that requires prompt diagnosis and treatment. With the appropriate use of antibiotics and appropriate infection control measures, the incidence of _S. pyogenes_ infections can be significantly reduced. The main objectives of this review are to know the causes of _Streptococcus pyogenes_.

Antibiofilm and Anti-quorum Sensing Activities of Biological Nanoparticles

Despite the availability of numerous antibacterial treatments, infectious diseases caused by multidrug-resistant bacteria remain a significant public health threat and are rapidly becoming the leading cause of global mortality. The emergence of multidrug resistance is due to the extensive use of high-dose antibiotics. Additionally, biofilm is another barrier to effective disease treatment because bacteria trapped in biofilm can resist antimicrobial agents. Therefore, the development of new strategies to combat multidrug-resistant bacteria and biofilm-associated infections is urgently needed. This is why special attention has been given to a recent area, "nanotechnology". Nanoparticles could be a source of hope for this problem as they can not only eliminate biofilms, but also interfere with quorum sensing (QS). Several studies have highlighted the advantages of biosynthesis over physiochemical synthesis of nanoparticles. These biologically synthesized nanoparticles demand special attention since this green technology combines energy and cost efficiency with environmental friendliness. This review summarizes the use of biological nanoparticles as biofilm and QS-inhibitors to combat biofilm-associated infections.

Review Article] Review of Streptococcus pyogenes

_Streptococcus pyogenes_, commonly known as group A _Streptococcus_ (GAS), is a bacterium that causes a wide range of clinical diseases. Its ability to cause superficial, invasive, and even life-threatening infections makes it an important pathogen that requires prompt diagnosis and treatment. It is a Gram-positive bacterium. These infections involve the bloodstream and can lead to sepsis, toxic shock syndrome, pneumonia, and necrotizing fasciitis. These infections require immediate medical attention and treatment with high doses of antibiotics and aggressive supportive care. _S. pyogenes_ is a bacterium that causes a wide range of clinical diseases. Its ability to cause superficial, invasive, and even life-threatening infections makes it an important pathogen that requires prompt diagnosis and treatment. With the appropriate use of antibiotics and appropriate infection control measures, the incidence of _S. pyogenes_ infections can be significantly reduced. The main objectives of this review are to know the causes of _Streptococcus pyogenes_.

Repurposing carvacrol, cinnamaldehyde, and eugenol as potential anti-quorum sensing agents against uropathogenic Escherichia coli isolates in Alexandria, Egypt

BackgroundUrinary tract infections represent one of the most frequent hospital and community-acquired infections with uropathogenic Escherichia coli (UPEC) being the main causative agent. The global increase in the emergence of multidrug-resistant (MDR) UPEC necessitates exploring novel approaches. Repurposing natural products as anti-quorum sensing (QS) agents to impede bacterial virulence is gaining momentum nowadays. Hence, this study investigates the anti-QS potentials of carvacrol, cinnamaldehyde, and eugenol against E. coli isolated from urine cultures of Egyptian patients.ResultsAntibiotic susceptibility testing was performed for 67 E. coli isolates and 94% of the isolates showed MDR phenotype. The usp gene was detected using PCR and accordingly, 45% of the isolates were categorized as UPEC. Phytochemicals, at their sub-inhibitory concentrations, inhibited the swimming and twitching motilities of UPEC isolates, with eugenol showing the highest inhibitory effect. The agents hindered the biofilm-forming ability of the tested isolates, at two temperature sets, 37 and 30 °C, where eugenol succeeded in significantly inhibiting the biofilm formation by > 50% at both investigated temperatures, as compared with untreated controls. The phytochemicals were shown to downregulate the expression of the QS gene (luxS) and critical genes related to motility, asserting their anti-QS potential. Further, the combinatory activity of the phytoproducts with five antibiotics was assessed by checkerboard assay. The addition of the phytoproducts significantly reduced the minimum inhibitory concentrations of the antibiotics and generated several synergistic or partially synergistic combinations, some of which have not been previously explored.ConclusionsOverall, carvacrol, cinnamaldehyde, and eugenol could be repurposed as potential anti-QS agents, which preferentially reduce the QS-based communication and attenuate the cascades of gene expression, thus decreasing the production of virulence factors in UPEC, and eventually, subsiding their pathogenicity. Furthermore, the synergistic combinations of these agents with antibiotics might provide a new perspective to circumvent the side effects brought about by high antibiotic doses, thereby paving the way for overcoming antibiotic resistance.

Paediatric bone and joint infections: a guide from diagnosis to management

Paediatric bone and joint infections (PBJI) can be challenging to diagnose due to their non-specific symptoms including fever, pain, swelling, and limited range of motion of the limb. The diagnosis involves a combination of clinical evaluation, laboratory tests, and imaging studies. Plain radiographs, ultrasound, and MRI can aid in the diagnosis of these infections. The approach to treating PBJI is multidisciplinary, involving paediatricians, infectious disease specialists, orthopaedic surgeons, and radiologists. Family-centred care and close follow-up are crucial to ensure optimal outcomes for children with bone infections. Management involves a combination of medical treatment with intravenous and oral antibiotics, and, if required, surgical interventions centred around debriding all dead bone and soft tissue, draining intra- or extra-osseus abscesses, stabilizing pathological fractures and delivering high doses of local antibiotics. Early diagnosis and prompt initiation of appropriate treatment are crucial to prevent long-term complications such as chronic osteomyelitis, septic arthritis, growth disturbances and limb length discrepancies.

Using the National Nosocomial Infections Surveillance risk index to determine risk factors associated with surgical site infections following gynecologic surgeries.

We used the National Nosocomial Infections Surveillance (NNIS) risk index to determine risk factors associated with surgical site infections (SSIs) following gynecologic surgeries. A retrospective study was conducted based on the medical records of 185 patients with SSIs, following gynecologic surgeries at a Grade A tertiary gynecologic and obstetric hospital in southwest China during September 2013-June 2021. Suspected risk factors associated with SSIs were: length of hospital stay, age, whether the patient had cancer, whether the patient had chemotherapy or high-dose antibiotic therapy before surgery, duration of surgery, amount of blood loss, and whether a blood transfusion was done. It was found that SSIs were more likely to occur in cancer patients with an NNIS risk index score of 1 and in patients with preoperative chemotherapy and an NNIS risk index score of 2. Among the patients with an NNIS risk index score of 2, the older the patient, the higher incidence of SSIs. Gynecologic surgery teams should pay more attention to the independent risk factors associated with SSIs determined by the NNIS risk index score to prevent SSIs following gynecologic surgeries, thus ensuring patient safety.

The study of the influence of tetracycline and sulfadiazine on biomethane production from manure and apple pomace

Anaerobic digestion is the most popular technic for obtaining biomethane from substrates like cow manure and other organic materials, however, chlortetracycline (CTC) and sulfadiazine (SDZ) which are commonly used in animal husbandry and present in cow manure can adversely affect biomethane yields. In this paper, the results of the influence of an increasing dose of CTC between 10 and 1000 mg×kg−1 and dose of SDZ between 10 and 500 mg×kg−1 on biomethane yield and kinetics for co-fermentation of cow manure and apple pomace experiment was presented. The obtained data during 21 days of lasting batch tests performed under mesophilic conditions allowed the determination of kinetics parameters of biomethane production according to the modified Gompertz model. The biomethane yield for the experiment with CTC differs from 233 to 353 mlCH4, while for the experiment with SDZ from 396 to 455 mlCH4. The kinetics parameters varied in a broad range. The ymax, λ, and Rm were 232–531 ml, 18–66 ml d−1, and –2.9-(–1.7) d for CTC, and 533–653 ml, 20–21 ml d−1, and –4.5-(–0.8) d for SDZ, respectively. With the high antibiotics dose, the biomethane yield decreased due to the inhibitive effect on microorganisms. The experiment showed that antibiotics had an inhibitory effect on biomethane production, at high doses. The biomethane yield had been reduced by 32.3 % at 1000 mg×kg−1 of CTC and by 13.9 % at 500 mg×kg−1 of SDZ. Interestingly, small doses (<100 mg×kg-1) did not affect significantly methane yield and sometimes increased it. Obtained results showed that the co-fermentation of apple pomace and manure performance may be affected by high doses of antibiotics. Depending on the dose and the antibiotic type it affects the biomethane yield, production rate, or lag phase differently.

Are envelope stress responses essential for persistence to β-lactams in Escherichia coli?

Bacterial persistence to antibiotics defines the ability of small sub-populations of sensitive cells within an isogenic population to survive high doses of bactericidal antibiotics. Here, we investigated the importance of the five main envelope stress responses (ESRs) of Escherichia coli in persistence to five bactericidal β-lactam antibiotics by combining classical time-kill curve experiments and single-cell analysis using time-lapse microscopy. We showed that the survival frequency of mutants for the Bae, Cpx, Psp, and Rcs systems treated with different β-lactams is comparable to that of the wild-type strain, indicating that these ESRs do not play a direct role in persistence to β-lactams. Since the σE-encoding gene is essential, we could not directly test its role. Using fluorescent reporters to monitor the activation of ESRs, we observed that σE is induced by high doses of meropenem. However, the dynamics of σE activation during meropenem treatment did not reveal any difference in persister cells compared to the bulk of the population, indicating that σE activation is not a hallmark of persistence. The Bae, Cpx, Psp, and Rcs responses were neither induced by ampicillin nor by meropenem. However, pre-induction of the Rcs system by polymyxin B increased survival to meropenem in an Rcs-dependent manner, suggesting that this ESR might confer some yet uncharacterized advantages during meropenem treatment or at the post-antibiotic recovery step. Altogether, our data suggest that ESRs are not key actors in E. coli persistence to β-lactams in the conditions we tested.

Acute dacryocystitis in aplastic anemia – A case report

Immunosuppression in Aplastic anemia often leads to bacterial sepsis and pneumonias. We report a case of a 33-year female with aplastic anemia, with acute fulminant dacryocystitis. She also had anemic retinopathy in both eyes with subhyaloid hemorrhage in the left eye. The clinical presentation was as with typical acute dacryocystitis with characteristic erythema and edema inferior to medial canthus. However, there was a rapid progression to systemic sepsis. She was treated with blood and blood component transfusion and hematopoietic growth factors in addition to high-dose broad-spectrum lytic antibiotics. The patient responded initially, but clinical course subsequently deteriorated due to systemic involvement. This may have happened due to infected lacrimal sac acting as a persistent focus of infection. This is the first documented case of treatment of acute dacryocystitis in aplastic anemia.

Systemic application of bone-targeting peptidoglycan hydrolases as a novel treatment approach for staphylococcal bone infection.

The rising prevalence of antimicrobial resistance in S. aureus has rendered treatment of staphylococcal infections increasingly difficult, making the discovery of alternative treatment options a high priority. Peptidoglycan hydrolases, a diverse group of bacteriolytic enzymes, show high promise as such alternatives due to their rapid and specific lysis of bacterial cells, independent of antibiotic resistance profiles. However, using these enzymes for the systemic treatment of local infections, such as osteomyelitis foci, needs improvement, as the therapeutic distributes throughout the whole host, resulting in low concentrations at the actual infection site. In addition, the occurrence of intracellularly persisting bacteria can lead to relapsing infections. Here, we describe an approach using tissue-targeting to increase the local concentration of therapeutic enzymes in the infected bone. The enzymes were modified with a short targeting moiety that mediated accumulation of the therapeutic in osteoblasts and additionally enables targeting of intracellularly surviving bacteria.

The essential role of intestinal microbiota in cytomegalovirus reactivation.

Human cytomegalovirus (HCMV) is a member of Herpesviridae. It has been reported that HCMV is reactivated in the breast milk of HCMV-seropositive lactating women. As we have reported various aspects of the roles of indigenous microbiota, its role in the murine CMV (MCMV) reactivation was examined in this study. MCMV was latently infected in the salivary gland, mammary tissues, and colon in the pregnant mice. When the salivary gland, mammary tissues, and colon were removed 5 days after delivery, MCMV reactivation of latent infection in each organ was confirmed by the detection of MCMV IE1 mRNA using reverse transcription-quantitative PCR. MCMV reactivation was observed in 100% of the mice during pregnancy. Next, for the elimination of intestinal microbiota, the pregnant mice were treated with low-dose or high-dose non-absorbable antibiotics. Although the numbers of aerobe/anaerobe in cecal content in low-dose antibiotic-treated mice were comparable to those in untreated controls, high-dose antibiotic treatment decreased the number of aerobe/anaerobe microbes from ca.9.0 Log10 to ca.3.0 Log10 (cfu/g). However, it could not be confirmed in 16S rRNA analysis that specific bacterial phylum or genus was eliminated by this high-dose treatment. Interestingly, MCMV reactivation was also observed in 100% of low-dose antibiotic-treated mice, whereas, in high-dose antibiotic-treated mice, MCMV reactivation was not observed in the salivary gland or colon. MCMV IE1 mRNA was detected only in 33% of the mammary tissues of those high-dose-treated mice. These results suggest that the indigenous microbiota played a crucial role in the reactivation of latent infection. IMPORTANCE Human cytomegalovirus (HCMV) infection via breast milk is a serious problem for very preterm infants such as developing a sepsis-like syndrome, cholestasis, or bronchopulmonary dysplasia, among others. It has been reported that HCMV is reactivated in the breast milk of HCMV-seropositive lactating women. In this study, the roles of indigenous microbiota in the murine CMV (MCMV) reactivation were examined using a mouse model. In MCMV latently infected mice, MCMV reactivation was observed in 100% of the mice during pregnancy. For the elimination of intestinal microbiota, MCMV-latent mice were treated with non-absorbable antibiotics. After delivery, MCMV reactivation was not observed in antibiotic-treated mice. This result suggested that the indigenous microbiota played a crucial role in the reactivation of latent infection.

Recurrent osteomyelitis in patient of osteopetrosis: A rare case report and management

: Osteopetrosis is a rare heritable disease. It sometimes presents as incidental finding with no symptoms to even life threatening complications. It may present as multiple fractures, compressive neuropathies, hypocalcaemia, and life-threatening pancytopaenia. In this article, A 15 years old female reported for evaluation and treatment of pain and pus discharge in the left side of mandible since 1 year after the extraction multiple deciduous tooth. pus discharge in the left side of mandible with draining fistula. Intraoral examination revealed exposed necrotic bone in mentioned region. : osteopetrosis of mandible may develop osteomyelitis. The osteomyelitis is usually due to tooth extraction or pulpal necrosis. However, its treatment is controversial.: Treatment regimens include high-dose systemic antibiotics along with thorough debridement of necrotic bone and primary closure of soft tissues &amp; may require Hyperbaric oxygen.

(P)ppGpp synthetase Rsh participates in rifampicin tolerance of persister cells in Brucella abortus in vitro

Brucella abortus is facultative intracellular pathogen that causes chronic persistent infections and results in abortion and infertility in food animals. Recurrent infections can be one of the results of persister cells formation that transiently displays phenotypic tolerance to high dose of antibiotics treatment. We examined persister cells formation of B. abortus strain A19 in stationary phase and investigated a potential role for the (p)ppGpp synthetase Rsh in this process. We found that B. abortus stationary phase cells can produce higher levels of multi-drugs tolerant persister cells in vitro under high dose of antibiotics (20 × MIC) exposure than do exponential phase cells. Persister cell formation was also induced with environmental stressors pH 4.5, 0.01 M PBS (pH7.0), 2% NaCl and 25 °C, upon exposure to ampicillin, enrofloxacin and rifampicin. Persister cells were not formed following exposure to 1 mM H2O2. The numbers of persister cells were significantly increased following uptake of B. abortus stationary phase cells by RAW264.7 macrophages in contrast with cultures in TSB liquid medium. Environmental stressors to B. abortus significantly increased expression of rsh mRNA level. The rsh null mutant (Δrsh) formed significantly fewer persister cells than the complemented (CΔrsh) and wildtype (WT) strains under high dose of rifampicin in vitro. These data for the first time demonstrate that B. abortus can produce multi-drug tolerant persister cells in stationary phase. The (p)ppGpp synthetase Rsh is necessary for persister cell formation in B. abortus in the presence of rifampicin. On this basis, a new understanding of the recurrent infections of Brucella was advanced, thus provided a new basis for revelation of pathogenic mechanism of the chronic persistent infection in Brucella.

Comparison of antibacterial activity and biocompatibility of non-leaching nitrofuran bone cement loaded with vancomycin, gentamicin, and tigecycline

BackgroundNon-leaching antibacterial bone cement can generate long-term antibacterial activity, it cannot treat serious infections that have occurred like antibiotic-loaded bone cement. Currently, the antibacterial activity and biocompatibility of non-leaching cement when loaded with antibiotics have yet to be determined.MethodsNon-leaching antibacterial nitrofuran bone cement (NFBC) specimens were prepared with low-dose and high-dose antibiotics. The antibacterial activity and biocompatibility of NFBC loaded with vancomycin, gentamicin, and tigecycline were compared. The agar diffusion method was employed to observe the inhibition zone of the samples against two bacterial strains from day one to day seven. The CCK-8 assay and acute liver and kidney toxicity test were conducted to assess the effects of the samples on mouse embryo osteoblast precursor cells and C57 mice, respectively.ResultsGentamicin-loaded cement exhibited the most potent antibacterial activity, effectively inhibiting both bacterial strains at a low dose. Tigecycline-loaded cement demonstrated superior biocompatibility, showing no acute liver and kidney toxicity in mice and minimal cytotoxicity to osteoblasts.ConclusionsNFBC loaded with gentamicin, vancomycin, and tigecycline not only maintains sustained antibacterial activity but also exhibits excellent biocompatibility.