Infection Of Crabs Research Articles

Optimizing Treatment for Carbapenem-Resistant Acinetobacter baumannii Complex Infections: A Review of Current Evidence.

Carbapenem-resistant Acinetobacter baumannii complex (CRAB) poses a significant global health challenge owing to its resistance to multiple antibiotics and limited treatment options. Polymyxin-based therapies have been widely used to treat CRAB infections; however, they are associated with high mortality rates and common adverse events such as nephrotoxicity. Recent developments include numerous observational studies and randomized clinical trials investigating antibiotic combinations, repurposing existing antibiotics, and the development of novel agents. Consequently, recommendations for treating CRAB are undergoing significant changes. The importance of colistin is decreasing, and the role of sulbactam, which exhibits direct antibacterial activity against A. baumannii complex, is being reassessed. High-dose ampicillin-sulbactam-based combination therapies, as well as combinations of sulbactam and durlobactam, which prevent the hydrolysis of sulbactam and binds to penicillin-binding protein 2, have shown promising results. This review introduces recent advancements in CRAB infection treatment based on clinical trial data, highlighting the need for optimized treatment protocols and comprehensive clinical trials to combat the evolving threat of CRAB effectively.

Intraventricular or intrathecal polymyxin B for treatment of post-neurosurgical intracranial infection caused by carbapenem-resistant gram-negative bacteria: a 8-year retrospective study.

Post-neurosurgical intracranial infection caused by carbapenem-resistant gram-negative bacteria (CRGNB) is a life-threatening complication. This study aimed to assess the current practices and clinical outcomes of intravenous (IV) combined with intraventricular (IVT)/intrathecal (ITH) polymyxin B in treating CRGNB intracranial infection. A retrospective study was conducted on patients with post-neurosurgical intracranial infection due to CRGNB from January 2013 to December 2020. Clinical characteristics and treatment outcomes were collected and described. Kaplan-Meier survival and multivariate logistic regression analyses were performed. The study included 114 patients, of which 72 received systemic antimicrobial therapy combined with IVT/ITH polymyxin B, and 42 received IV administration alone. Most infections were caused by carbapenem-resistant Acinetobacter baumannii (CRAB, 63.2%), followed by carbapenem-resistant Klebsiella pneumoniae (CRKP, 31.6%). Compared with the IV group, the IVT/ITH group had a higher cerebrospinal fluid (CSF) sterilization rate in 7 days (p < 0.001) and lower 30-day mortality (p = 0.032). In the IVT/ITH group, patients with CRKP infection had a higher initial fever (p = 0.014), higher incidence of bloodstream infection (p = 0.040), lower CSF sterilization in 7 days (p < 0.001), and higher 30-day mortality (p = 0.005) than those with CRAB infection. Multivariate logistic regression analysis revealed that the duration of IVT/ITH polymyxin B (p = 0.021) was independently associated with 30-day mortality. Intravenous combined with IVT/ITH polymyxin B increased CSF microbiological eradication and improved clinical outcomes. CRKP intracranial infections may lead to more difficult treatment and thus warrant attention and further optimized treatment.

Macrophthalmus (Macrophthalmus) abbreviatus Manning & Holthuis, 1981, a new natural host for Hematodinium perezi infection.

Recent reports have shown that wild crabs may be important hosts involved in the transmission and spread of the parasitic Hematodinium in cultured marine crustaceans. Therefore, monitoring the prevalence of Hematodinium infections in wild crabs is necessary to develop effective strategies for the prevention and control of Hematodinium disease. Here we report a wild crab species, Macrophthalmus (Macrophthalmus) abbreviatus Manning & Holthuis, 1981, as a new natural host for Hematodinium sp. infection. It is one of the common wild crab species dwelling in the ponds or waterways connected to the polyculture ponds located on the coast of Rizhao or Weifang, Shandong Peninsula, China. According to the results of PCR detection and phylogenetic analysis targeting the internal transcribed spacer 1 (ITS 1) region, these Hematodinium sp. isolates were identified as H. perezi and fell into the genotype II category within H. perezi. A high monthly prevalence of H. perezi infection was observed during the 2021-2022 field survey, ranging from 33.3% to 90.6% in M. abbreviatus originating from Weifang (n=304 wild crabs) and from 53.6% to 92.9% in those from Rizhao (n=42 wild crabs). Artificial inoculation infection experiments demonstrated that M. abbreviatus could be infected by H. perezi, and massive Hematodinium cells and typical histopathological changes were observed in the hepatopancreas and gill tissues of the infected crabs. To our knowledge, this is the first report of M. abbreviatus as a new natural host for H. perezi infection. Results in the present study extend the known host spectrum for this emerging parasite pathogen, and also provide valuable information for epidemic surveillance of the Hematodinium disease as well.

API5-Hsp20 axis regulate apoptosis and viral infection in mud crab (Scylla paramamosain).

Apoptosis Inhibitor 5 (API5) is a widely concerned nuclear protein with diverse functions in organisms, so far, study of API5 is still quite limited in lower animals, and its role in viral immune response has not been addressed. Here, we explored the function of API5 in mud crab (Scylla paramamosain) during White Spot Syndrome Virus (WSSV) infection. The interacting protein Hsp20 of API5 was screened by pull-down assay, and API5 and hsp20 were knocked down by RNAi interference. The results showed that API5 was upregulated along with virus infection, silencing of API5 led to increased WSSV copy numbers and apoptotic rate of hemocytes, highlighting its significance in the immune response. Moreover, we discovered a novel interaction between API5 and Heat Shock Protein 20 (Hsp20), and then revealed that Hsp20 could promote cell apoptosis of hemocytes and reduce viral copy numbers by suppressing API5. The current study therefore improves the knowledge of API5-Hsp20 axis and provides novel insights into intricate mechanisms governing the antiviral response in marine crustaceans.

A systematic review and meta-analysis for risk factor profiles in patients with resistant Acinetobacter baumannii infection relative to control patients.

Acinetobacter baumannii is a major cause of nosocomial infections and high mortality rates. Evaluation of risk factors for such resistant infections may aid surveillance and diagnostic initiatives, as well as, can be crucial in early and appropriate antibiotic therapy. To identify the risk factors in patients with resistant A. baumannii infection with respect to controls. Prospective or retrospective cohort and case-control studies reporting the risk factors for resistant A. baumannii infection were collected through two data sources, MEDLINE/PubMed and OVID/Embase. Studies published in the English language were included while animal studies were excluded. The Newcastle-Ottawa Scale was used to assess the quality of studies. The odds ratio of developing antibiotic resistance in patients with A. baumannii infection was pooled using a random-effect model. The results are based on 38 studies with 60878 participants (6394 cases and 54484 controls). A total of 28, 14, 25, and 11 risk factors were identified for multi-drug resistant (MDRAB), extensive-drug resistant (XDRAB), carbapenem-resistant (CRAB) and imipenem resistant A. baumannii infection (IRAB), respectively. In the MDRAB infection group, exposure to carbapenem (OR 5.51; 95% CI: 3.88-7.81) and tracheostomy (OR 5.01; 95% CI: 2.12-11.84) were identified with maximal pool odd's ratio. While previous use of amikacin (OR 4.94; 95% CI: 1.89-12.90) and exposure to carbapenem (OR 4.91; 95% CI: 2.65-9.10) were the foremost factors associated with developing CRAB infection. Further analysis revealed, mechanical ventilation (OR 7.21; 95% CI: 3.79-13.71) and ICU stay (OR 5.88; 95% CI: 3.27-10.57) as the most significant factors for XDRAB infection. The exposure of carbapenem, amikacin (previous) and mechanical ventilation were the most significant risk factors for multidrug, extensive-drug, and carbapenem resistance in patients with A. baumannii infection respectively. These findings may guide to control and prevent resistant infections by identifying the patients at higher risk of developing resistance.

2458. Carbapenem-resistant Acinetobacter baumannii complex infections and SARS-CoV-2 positivity in 9 U.S. sites, 2020-2022

Abstract Background Reports have shown increases in carbapenem-resistant Acinetobacter baumannii complex (CRAB) infections during the COVID-19 pandemic. To describe the effect of SARS-CoV-2 (SC2) infection on CRAB infection epidemiology, we analyzed data from the Centers for Disease Control and Prevention’s Emerging Infections Program (EIP) population-based CRAB surveillance in 9 U.S. sites. Methods: In 2020–22, among surveillance-area residents, an incident CRAB case was defined as the 1st isolation of A. baumannii complex resistant to ≥1 carbapenem (excluding ertapenem) from a normally sterile site or urine (or lower respiratory tract or wound, as of 2021) in a 30-day period. We included cases that underwent chart review. Cases with a culture collected ≥3 days after hospitalization were considered hospital-onset (HO); all others were community-onset (CO). Cases with a SC2+ test ≤14 days before the incident CRAB culture were compared to other CRAB cases. Results Of 406 CRAB cases representing 344 patients, 26 (6%) cases in 24 patients were SC2+. SC2+ case-patients were more likely to be female than other CRAB case-patients (58% vs 34%, p=0.02); there were no significant differences in race/ethnicity or age distribution. SC2+ cases were more likely to be obese (42% vs. 23%, p=0.03), have bacteremia (23% vs. 10%, p=0.05), and to have died (39% vs. 16%, p=0.003). SC2+ cases were also more likely to require hospitalization (100% vs. 75%, p=0.005) and have HO CRAB (58% vs 29%, p=0.003). Median hospital length of stay was longer in SC2+ cases (19 days, interquartile range [IQR] 8–30) than in other CRAB cases (14 days, IQR 7–26, p=0.42), but there were no significant differences in the percentages with intensive care unit stays or mechanical ventilation in the 7 days before CRAB culture. Culture sources and infection types in SC2+ cases vs. other CRAB cases are shown in the Table. Conclusion A small minority of CRAB patients were infected with SC2+ in the 14 days before CRAB infection but these patients had epidemiological and clinical features that were distinct from other CRAB patients, including higher mortality. Infection control and clinical measures are needed to protect SC2+ patients from secondary bacterial infection and mitigate poor outcomes in those with SC2 and CRAB infection. Disclosures Ghinwa Dumyati, MD, Pfizer: Grant/Research Support Rebecca Tsay, MPH, CDC: Grant/Research Support

2137. Real World Experience with Eravacycline for the Treatment of Infections Caused by Carbapenem-Resistant Acinetobacter baumannii

Abstract Background Carbapenem-resistant Acinetobacter baumannii (CRAB) are considered an urgent public health threat responsible for causing severe infections with high associated mortality. CRAB isolates are often resistant to several antibiotic classes thereby limiting treatment options. Eravacycline is a novel tetracycline antibiotic with potent in vitro activity against CRAB. Per the recent Infectious Diseases Society of America (IDSA) Guidance on the Treatment of Antimicrobial-Resistant Gram-Negative Infections, clinical data are limited for eravacycline use for CRAB infections. The purpose of this study was to evaluate clinical outcomes of patients treated with eravacycline for CRAB infections at Montefiore Medical Center. Methods This was a retrospective chart review of patients 18 years of age and older who received eravacycline for at least 72 hours for the treatment of an infection due to CRAB between January 1, 2019 to February 28, 2023. Patients were excluded if they had a urinary tract infection. Patient demographics, risk factors, type/source of infection, clinical outcomes, etc. were collected. Results Eighteen patients received eravacycline for the treatment of non-urinary CRAB infections (Table 1). Ventilator-associated pneumonia was the predominant infection, representing 14/18 (78%) cases. High rates of antibiotic non-susceptibility were demonstrated in all cases. Median eravacycline minimum inhibitory concentration (MIC) was 1 mg/L, with a range of 0.19 – 6 mg/L. Median duration of eravacycline therapy was 7 days. Overall, the clinical success rate was 33% (6/18). Four patients (22%) experienced progression or worsening of symptoms that required a change in antibiotics. Of 11 evaluable patients, three patients (27%) had a recurrent infection caused by CRAB within 30 days of completion of eravacycline therapy. All-cause 30-day mortality was 56% (10/18), with six deaths (33%) attributed to CRAB infection. Conclusion CRAB infections pose a significant challenge in the healthcare setting and are associated with high mortality rates. Eravacycline remains a last resort option for these difficult to treat infections. Further study is warranted for eravacycline use for CRAB infections. Disclosures All Authors: No reported disclosures

Exosomal SpFlotillin-1 participates in resistance to Vibrio parahemolyticus infection in mud crab (Scylla paramamosain)

Exosomes have been considered anti-microbial immune factors in animals (including aquatic animals). However, the relationship between exosomal proteins and immune responses during bacterial infection has not been addressed. Flotillin-1 has previously been shown to enrich plasma membrane which implicates in cellular processes, including signal transduction, membrane trafficking, and molecular sorting. In this study, SpFlotillin-1 was cloned and characterized from mud crab (Scylla paramamosain). SpFlotillin-1 was found to be up-regulated in the hemocytes of mud crabs after infecting with V. parahaemolyticus. RNAi knockdown of SpFlotillin-1 showed capacity in suppressing phagocytosis and reducing the expression of antimicrobial peptides (AMPs) but increasing the ROS production in hemocytes. Furthermore, SpFlotillin-1 densely packaged in the exosomes can regulate the phagocytosis, expression of AMPs through MAPK and NF-κB pathway, and production of ROS, eventually activating the immune response to bacterial infection in mud crabs. Taken together, the results of this study provide a new finding on the mechanism that exosomal SpFlotillin-1 may participate in the V. parahaemolyticus infection through the regulation of phagocytosis and activation of AMP synthesis in mud crabs.

Effects of the tumor necrosis factor on hemocyte proliferation and bacterial infection in Chinese mitten crab (Eriocheir sinensis)

Tumor necrosis factor (TNF) is an important cytokine that can regulate a variety of cellular responses by binding tumor necrosis factor receptor (TNFR). We studied whether the TNF of Eriocheir sinensis can regulate hemocyte proliferation. The results showed that the EsTNF and EsTNFR were constitutively expressed in all tested tissues, including the heart, hepatopancreas, muscles, gills, stomachs, intestines, and hemocytes. We found that low levels of EsTNF and EsTNFR transcripts were present in hemocytes. The gene expression levels were significantly increased in the hemocytes after being stimulated by Staphylococcus aureus or Vibrio parahaemolyticus. We also found some genes related to cell proliferation were expressed at a higher level in pulsing rTNF-stimulated hemocytes compared with the control group. We also knocked down the EsTNFR gene with RNAi technology. The results showed that the expression level of these genes related to cell proliferation was significantly down-regulated compared with the control group when the TNF does not bind TNFR. We used Edu technology to repeat the above experiments and the results were similar. Compared with the control group, the hemocytes stimulated by rTNF showed more significant proliferation, and the proliferation rate was significantly down-regulated after knocking down the EsTNFR gene. Therefore, we indicate that TNF binding TNFR can affect the proliferation of E. sinensis hemocytes, which might be manifested by affecting the expression of some proliferation-related genes.

KCMF1-like suppresses white spot syndrome virus infection by promoting apoptosis in mud crab (Scylla paramamosain)

Potassium channel modulatory factor 1 (KCMF1), an E3 ubiquitin ligase, plays a vital role in renal tubulogenesis, preeclampsia, and tumor development in mammals. Nevertheless, the function of KCMF1 in invertebrates remains to be investigated. Here, we identified KCMF1-like from Scylla paramamosian, encoding 242 amino acids with two zinc finger domains at the N-terminal. Real-time quantitative PCR analysis revealed that KCMF1-like was expressed in all tested tissues, including hemocytes, brain, mid-intestine, subcuticular epidermis, gills, muscle, heart, and stomach, with higher levels in muscle and mid-intestine. KCMF1-like was up-regulated in the hemocytes of mud crabs challenged with white spot syndrome virus (WSSV). RNA interference (RNAi) was performed to investigate the impact of KCMF1-like on the proliferation of WSSV in mud crabs. Knock-down of KCMF1-like resulted in an increase of the WSSV copy number and an impairment of the hemocytes apoptosis rate in vivo. In addition, KCMF1-like could also affect the mitochondrial membrane potential. Collectively, these results revealed that KCMF1-like might play a crucial role in the defense against virus infection in mud crab. This study contributes a novel insight into the role of KCMF1-like in the antiviral immune defense mechanism in crustaceans.

Co-infection of mud crab Reovirus (MCRV) and Staphylococcus saprophyticus in giant mud crab, Scylla serrata (Forsskal, 1775)

The culture of animals in a controlled environment can be a factor in disease transmission. Mud Crab Reovirus (MCRV) and staphylococcus saprophyticus were co-infected in Scylla serrata, in a fattening pen from MGR Thittu, Cuddalore District, Tamil Nadu, Southeast coast of India. Lethargic, sluggish, partially atrophied hepatopancreas, loose gills, and discoloration of the animal characterized the spontaneously infected moribund crab. Viral invasion in the hepatopancreas with basophilic inclusion was evaluated in the histopathological studies. Molecular evidence shows reovirus infection in crab. Scanning electron microscopy reveals the presence of cocci bacteria. The 16 s RNA sequencing and phylogenetic analysis confirm the infected bacteria were Staphylococcus saprophyticus. Ultrastructural studies provided evidence for the coinfection of MCRV and Staphylococcus saprophyticus. This is the inaugural article on the co-infection of reovirus and bacteria in the mud crab Scylla serrata.

The effect of reactive oxygen species (ROS) in immunity and WSSV infection of Scylla paramamosain

Reactive oxygen species (ROS) are typically regarded as being generated by the cellular respiratory chain or by cells under pathological damage, which play a crucial role as signaling molecules in promoting hemocytes circulation and normal cellular physiological functions. In this study, the antioxidant N-acetylcysteine (NAC) was used to reduce ROS in vivo and in vitro, which to analyze the effect of ROS on innate immunity and viral infection of mud crab. The total hemocyte count (THC), phenoloxidase (PO), superoxide dismutase (SOD) activity, immune-relative genes were analyzed, respectively. Moreover, the effect of ROS on WSSV infection was analyzed by THC and hemocytes apoptosis. The data showed that NAC could effectively remove and inhibit intracellular ROS. The THC of NAC group was reduced at 12 h and 24 h compared with that of control. And the inhibition of ROS by NAC could increase the SOD activity with control group, while increased the PO activity caused by early WSSV infection. And NAC could up-regulate the expression of MCM7, JAK, TLR and proPO significantly, while down-regulate the expression of Astakine, proPO, caspase and p53. Similarly, NAC could inhibit WSSV-induced apoptosis of S. paramamosain hemocytes. The data illustrated that ROS participates in the interaction between hemocytes and virus infection by regulating innate immunity. Especially, after NAC inhibited ROS, the expression of hemocytes proliferation gene Astakine was also inhibited, which may indicate that ROS is related to the process of hemocytes proliferation. The data will show a preliminary exploration on the regulatory role of ROS in crustacean immune system.

Short versus long course of colistin treatment for carbapenem-resistant A. baumannii in critically ill patients: A propensity score matching study

BackgroundCarbapenem-resistant Acinetobacter baumannii (CRAB) is one of the most commonly found nosocomial infections in critically ill patients. However, the appropriate treatment period for a specific group of critically ill patients with CRAB infection is currently being debated. Therefore, our study aimed to evaluate the optimal courses of therapy for critically ill patients with CRAB infection by comparing the outcomes of colistin therapy of short duration (<14 days) versus long duration (≥ 14 days). MethodsA retrospective cohort study was conducted at Nakornping Hospital on critically ill patients with CRAB infection who received either a short or long course of colistin treatment between 2015 and 2022. The primary outcome was the 30-day mortality rate while secondary outcomes were clinical response, microbiological response, and nephrotoxicity. Propensity score matching with a 1: 1 ratio was performed to reduce potential biases. Furthermore, a logistic regression model was used to estimate the odds ratio (OR). ResultsA total of 374 patients met the inclusion criteria. Two hundred and forty-eight patients were recruited after utilizing propensity scores to match patients at a 1: 1 ratio. The results from the propensity score matching analysis demonstrated that the long-course therapy group had a lower 30-day mortality rate compared to the short-course therapy group (adjusted OR (aOR) = 0.46, 95% CI: 0.26–0.83, p = 0.009). The clinical response and microbiological response rates were higher in patients who received the long course of colistin therapy compared to those receiving the short course (aOR = 3.24, 95% CI: 1.78–5.92, p = 0.001; aOR = 3.01, 95% CI: 1.63–5.57, p = 0.001). There was no significant different in the occurrence of nephrotoxicity (aOR = 1.28, 95% CI: 0.74–2.22, p = 0.368) between the two treatment groups. ConclusionA long course of colistin therapy resulted in a lower 30-day mortality rate in critically ill patients, and better clinical and microbiological outcomes, but similar nephrotoxicity as compared to a short course of colistin therapy. Therefore, a specific subset of critically ill patients who had CRAB infection needed to be considered for a long course of therapy.

Duox mediated ROS production inhibited WSSV replication in Eriocheir sinensis under short-term nitrite stress

Nitrite stress and white spot syndrome virus (WSSV) infection are major problems threatening the sustainable and healthy development of Eriocheir sinensis. Some studies have found that nitrite stress can lead to the production of reactive oxygen species (ROS), whereas synthetic ROS plays a vital role in the signaling pathway. However, whether nitrite stress influences the infection of crabs by WSSV remains unclear. NADPH oxidases, including NOX1-5 and Duox1-2, are important for ROS production. In the present study, a novel Duox gene (designated as EsDuox) was identified from E. sinensis. The studies found that nitrite stress could increase the expression of EsDuox during WSSV infection and decrease the transcription of the WSSV envelope protein VP28. Moreover, nitrite stress could increase the production of ROS, and the synthesis of ROS relied on EsDuox. These results indicated a potential “nitrite stress–Duox activation–ROS production” pathway that plays a negative role in WSSV infection in E. sinensis. Further studies found that nitrite stress and EsDuox could promote the expression of EsDorsal transcriptional factor and antimicrobial peptides (AMPs) during WSSV infection. Moreover, the synthesis of AMPs was positively regulated by EsDorsal in the process of WSSV infection under nitrite stress. Furthermore, EsDorsal played an inhibitory role in the replication of WSSV under nitrite stress. Our study reveals a new pathway for “nitrite stress–Duox activation–ROS production–Dorsal activation–AMP synthesis” that is involved in the defense against WSSV infection in E. sinensis during short-term nitrite stress.

Subcellular Translocation of Yorkie through the PRP4K-CRM1 Axis Regulates Antimicrobial Peptides Transcription and Defense against Bacterial Infection in Crab.

The Hippo signaling pathway plays important roles in innate immunity. In the current study, we found that bacterial infection did not influence mRNA and protein levels of yorkie (Yki), which is an important terminal molecule of the Hippo signaling pathway. However, bacterial infection promoted the translocation of Yki from the nucleus to the cytoplasm in Chinese mitten crab (Eriocheir sinensis), thus attenuating Yki-suppressed transcription of antimicrobial peptides through Cactus. Chromosome region maintenance 1 (CRM1)-silenced crab hemocytes significantly suppressed Yki translocation from the nucleus to the cytoplasm upon bacterial infection, resulting in significantly increased expression of Cactus, decreased expression of antimicrobial peptides, and higher bacterial susceptibility, which demonstrated the regulatory role of CRM1 in subcellular localization of Yki. However, RNA interference of Scalloped (Sd) exhibited no effect on the subcellular localization of Yki and its regulation of Cactus/antimicrobial peptides. Moreover, we elucidated that both CRM1 and Sd could interact with Yki and that the PRP4K-mediated phosphorylation of a conserved serine amino acid residue in the nuclear export signal of Yki is essential for interaction between Yki and CRM1; however, the phosphorylation did not affect the binding of Yki with Sd. We also found that bacterial infection significantly promoted the expression of PRP4K in hemocytes; RNA interference of PRP4K and phosphatase inhibitor suppressed Yki translocation from the nucleus to the cytoplasm, promoting Cactus expression and inhibiting antimicrobial peptide expression. Thus, subcellular localization of Yki regulates antibacterial infection through both PRP4K and CRM1 in crabs.

Dynamic Distribution of Mesanophrys sp. and Tissue Enzyme Activities in Experimentally Infected Mud Crab Scylla paramamosain

Mesanophrys sp. is reported to be highly pathogenic to marine crustaceans. This study presents the first report of Mesanophrys sp. infection in the mud crab (Scylla paramamosain). In this study, we first recorded the survival rates of an experimentally infected group and a control group; the cumulative survival rate in the infected group was significantly lower compared to the control group after 72 h (73.20% vs. 94.19%), while the highest mortality of S. paramamosain occurred within the first 24 h post-infection. Then, we investigated the dynamic distribution and tissue tropism of the Mesanophrys sp. in the infected S. paramamosain by a quantitative real-time polymerase chain reaction (qPCR). The result showed that a significant increase in the number of Mesanophrys sp. could be detected in all tested tissues (obtained from the eyestalks, gills, heart, nerves, muscles and hepatopancreas) at 3 h post-infection. The numbers of Mesanophrys sp. in the gill, eyestalk and nerve tissues were relatively higher than in the other tissues. The gill tissue showed the highest numbers from 6 to 48 h. Histopathological observation found a severe collapse in the filament structure, which indicated tissue-specific pathogen infection. Furthermore, the antioxidant enzyme activity of superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) in three representative tissues (gill, muscle and hepatopancreas) were compared between the infected and control groups, and a significant increase in enzyme activity was observed in all three tested tissues in the infected group, indicating a relatively strong innate immune defense reaction that could have been induced by Mesanophrys sp. infection. These results will be helpful to Mesanophrys sp. pathogenicity-related research and the control of this pathogen in S. Paramamosain in the future.

Protective effect of chicken egg yolk immunoglobulin (IgY) against Spiroplasma eriocheiris infection in Chinese mitten crab

The aquaculture of the Chinese mitten crab Eriocheir sinensis has become the leading and pillar of aquaculture in China. The tremor disease (TD) caused by Spiroplasma eriocheiris is the most destructive disease of E. sinensis. At present, the treatment of TD in crabs mainly depends on antibiotics. To protect the environment and the health of aquatic products, it is urgent to establish an effective and pollution-free green prevention and control technology. This study aimed to investigate the prevention and control of the TD by immunization with chicken yolk antibody (IgY). Anti-S. eriocheiris IgY was obtained by intramuscular injection of ultrasonically inactivated S. eriocheiris into chickens. After successful isolation and purification of IgY from eggs, ELISA and sensitivity tests were performed. Specific IgY was able to specifically react at a titer of 1:10,000 to antigen at a minimum concentration of 20 μg/mL and to inhibit the growth of S. eriocheiris in vitro. The affection of IgY in vivo to resist S. eriocheiris infection was demonstrated by feeding or injection of specific IgY. The copy number of S. eriocheiris in crab hemocytes with specific IgY administration was significantly less than in crabs that received normal IgY or without IgY. Meanwhile, the survival rate of E. sinensis with anti-S.eriocheiris- specific IgY using both injection and feeding methods significantly increased during S. eriocheiris infection. The electron microscope results showed that the structure of S. eriocheiris in specific IgY group was completely irregular and broken pin vivo. Finally, this study provides a reference for clarifying the potential role of specific IgY to help E. sinensis resist S. eriocheiris infection.

First report of Ameson portunus (microsporidia) infection in earthen pond-cultured mud crab, Scylla paramamosain (Decapoda: Portunidae) in China, causing mass morbidity.

First report of Ameson portunus (microsporidia) infection in earthen pond-cultured mud crab, Scylla paramamosain (Decapoda: Portunidae) in China, causing mass morbidity.

654. Clinical efficacy and safety of high dose Ampicillin sulbactam among patients with CRAB infections: A case series

Abstract Background CRAB continues to threaten the healthcare facilities in developing nations and is one among the commonest causes of hospital acquired infections in our hospital. In December 2021, the IDSA published the AMR guidance 2.0, that stated Ampicillin- sulbactam as the first choice for treating CRAB infections. We review the clinical outcomes with adherence to this guideline in our setting. Methods A descriptive study from India (January 2022 to April 2022), of in-patients who have received ampicillin sulbactam monotherapy or combination for CRAB infections. A standard treatment guideline for the identification and management of CRAB infections was introduced to the clinicians based on the AMR guidance 2.0 of IDSA. CRAB infections were classified as mild to severe based on clinical and radiological parameters. We collected the data on patients who were started on ampicillin sulbactam, given in a high dose (27g per day or renally adjusted) as a 4-hour infusion either alone or as combination with other antibiotics for the indication of CRAB infections. Results Ampicillin-Sulbactam was started for 12 patients with CRAB infection. 2 of these patients were discharged while on treatment and hence, excluded. 6 out of the 10 patients were being treated for CRAB associated hospital acquired pneumonia, whereas the other indications included urinary tract infection, post neurosurgical meningitis and skin and soft tissue infections. Susceptibility testing to Ampicillin-Sulbactum was not possible in our setting. All the patients survived from 14 days of starting the therapy and 9 out of 10 patients improved clinically (in terms of defervescence or symptomatic relief) by day 7. No adverse effects were noted either in clinical symptoms or Laboratory parameters during the course of treatment. Conclusion High dose Ampicillin-Sulbactum is effective and safe for CRAB infections with varying clinical syndromes and severity. All patients in this case series were treated with Colistin sparing regimens when combination therapy was required. Disclosures All Authors: No reported disclosures.

Prevalence and pathology of Sacculina beauforti (Cirripedia, Rhizocephala) infection in box crab, Calappa lophos of Southeast coast of India

Prevalence and pathology of Sacculina beauforti (Cirripedia, Rhizocephala) infection in box crab, Calappa lophos of Southeast coast of India