Serratia marcescens, as a Gram-negative opportunistic pathogen, is a rare cause of peritonitis and has worse clinical outcomes than Gram-positive peritonitis. In this case report, we describe a case of Serratia marcescens associated peritonitis that was successfully cured without catheter removal. A 40-year-old male patient with peritoneal dialysis who worked in the catering industry was admitted to the hospital for 16 hours after the discovery of cloudy peritoneal dialysate and abdominal pain. Ceftazidime and cefazolin sodium were immediately given intravenously as an empirical antibiotic regimen. After detecting Serratia marcescens in the peritoneal diasate culture, the treatment was switched to ceftazidime and levofloxacin. The routine examination of peritoneal dialysate showed a significant decrease in white blood cells, the peritoneal dialysate became clear, and the peritoneal dialysis catheter was retained. The patient was treated for 2 weeks and treated with oral antibiotics for 1 week. It is necessary to further strengthen the hygiene of work environment to prevent Serratia marcescens infection in peritoneal dialysis patients. We recommend that patients with Serratia marcescens associated peritonitis should be treated with a combination of antibiotics as early as possible empirically, and at the same time, the peritoneal dialysis fluid culture should be improved, and the antibiotic regimen should be timely adjusted according to the drug sensitivity results. For patients with clinical symptoms for more than 3 days, considering the strong virulence of Serratia marcescens, whether to use meropenem directly or not can provide a reference for clinical decision-making. Further clinical studies are needed to achieve more precise anti-infective treatment.

For antimicrobial agents in particular, plasma protein binding (PPB) plays a pivotal role in deciphering key properties of drug candidates. Animal models are generally used in the preclinical development of new drugs to predict their effects in humans using translational pharmacokinetics/pharmacodynamics (PK/PD). Thus, we compared the protein binding (PB) of cefazolin as well as bacterial growth under various conditions in vitro. The PB extent of cefazolin was studied in human, bovine, and rat plasmas at different antibiotic concentrations in buffer and media containing 20-70% plasma or pure plasma using ultrafiltration (UF) and equilibrium dialysis (ED). Moreover, bacterial growth and time-kill assays were performed in Mueller Hinton Broth (MHB) containing various plasma percentages. The pattern for cefazolin binding to plasma proteins was found to be similar for both UF and ED. There was a significant decrease in cefazolin binding to bovine plasma compared to human plasma, whereas the pattern in rat plasma was more consistent with that in human plasma. Our growth curve analysis revealed considerable growth inhibition of Escherichia coli at 70% bovine or rat plasma compared with 70% human plasma or pure MHB. As expected, our experiments with cefazolin at low concentrations showed that E. coli grew slightly better in 20% human and rat plasma compared to MHB, most probably due to cefazolin binding to proteins in the plasma. Based on the example of cefazolin, our study highlights the interspecies differences of PB with potential impact on PK/PD. These findings should be considered before preclinical PK/PD data can be extrapolated to human patients.

BACKGROUND: Pyomyositis is a microbial infection of the muscles and contributes to local abscess formation. Staphylococcus aureus frequently causes pyomyositis; however, transient bacteremia hinders positive blood cultures and needle aspiration does not yield pus, especially at the early disease stage. Therefore, identifying the pathogen is challenging, even if bacterial pyomyositis is suspected. Herein, we report a case of primary pyomyositis in an immunocompetent individual, with the identification of S aureus by repeated blood cultures.
METHODS: A 21-year-old healthy man presented with fever and pain from the left chest to the shoulder during motion. Physical examination revealed tenderness in the left chest wall that was focused on the subclavicular area. Ultrasonography showed soft tissue thickening around the intercostal muscles, and magnetic resonance imaging with short-tau inversion recovery showed hyperintensity at the same site. Oral nonsteroidal anti-inflammatory drugs for suspected virus-induced epidemic myalgia did not improve the patient\'s symptoms. Repeated blood cultures on days 0 and 8 were sterile. In contrast, inflammation of the soft tissue around the intercostal muscle was extended on ultrasonography.
METHODS: The blood culture on day 15 was positive, revealing methicillin-susceptible S aureus JARB-OU2579 isolates, and the patient was treated with intravenous cefazolin.
METHODS: Computed tomography-guided needle aspiration from the soft tissue around the intercostal muscle without abscess formation was performed on day 17, and the culture revealed the same clone of S aureus.
RESULTS: The patient was diagnosed with S aureus-induced primary intercostal pyomyositis and was successfully treated with intravenous cefazolin for 2 weeks followed by oral cephalexin for 6 weeks.
CONCLUSIONS: The pyomyositis-causing pathogen can be identified by repeated blood cultures even when pyomyositis is non-purulent but suspected based on physical examination, ultrasonography, and magnetic resonance imaging findings.

BACKGROUND: An infected popliteal pseudoaneurysm has never been described in the pediatric population. Physicians need to be aware of its presentation and management, in order to diagnose and treat this medical condition adequately.
METHODS: We describe the case of a 14-year-old boy who developed myositis and cellulitis centered at the popliteal fossa after playing basketball. A treatment of intravenous cefazolin was started. 5 days later, he experienced a knee pain flare-up, which turned out to be a popliteal pyomyositis with a pseudoaneurysm of the popliteal artery. A saphenous vein graft bypass of the popliteal artery and an excision of the popliteal pseudoaneurysm were performed. Intravenous cefazolin was continued for 6 weeks and prophylactic acetylsalicylic acid for 6 months.
CONCLUSIONS: This case highlighted the importance of repeating radiologic investigations if a patient suffering from soft tissue infection has persistent pain after several days of appropriate antibiotics. A popliteal pseudoaneurysm can be diagnosed with ultrasound imaging and treated with a popliteal-popliteal bypass. Our patient needed a catheter-guided dilation of the anastomosis at the vein graft 6 months post-surgery, and then evolved favorably and went back to playing basketball 6 months post-dilation.

Kounis syndrome is an allergic acute coronary syndrome (ACS) characterised by coronary artery spasm, plaque erosion/rupture or stent thrombosis caused by mast cell and other interacting cell activation. Although intracoronary imaging modalities can detect those ACS mechanisms, Kounis syndrome due to plaque rupture has rarely been reported using intracoronary imaging. We present the case of a woman in her 70s who developed Kounis syndrome as a result of plaque rupture detected with optical coherence tomography (OCT). She had non-ST-segment elevation ACS as a result of anaphylaxis to cefazolin. Coronary angiography revealed severe stenosis in the left anterior descending artery; angiographically undetectable plaque rupture was detected using OCT. OCT also revealed intraplaque neovascularisation, suggesting that the culprit plaque had been vulnerable. OCT can aid in understanding the underlying mechanisms of Kounis syndrome.

Purpose: To describe a case of significantly elevated international normalized ratio (INR) in a patient on apixaban receiving treatment with intravenous cefazolin in the setting of coronavirus disease 2019 (COVID-19) infection and malnutrition. Summary: A 74-year-old male patient on apixaban receiving cefazolin for osteomyelitis in the setting of COVID-19 and poor nutritional intake presented with internal jugular tunneled catheter site bleeding and an INR of greater than 22.5. Laboratory abnormalities and bleeding concerns were successfully managed with vitamin K and changing antimicrobial therapy from cefazolin to daptomycin. Follow-up labs one week later demonstrated a sustained improvement in coagulopathy. Conclusion: INR prolongation believed to be secondary to cefazolin can be effectively managed with administration of vitamin K and conversion of antimicrobial therapy to an alternative agent.

Intraoperative anaphylaxis is a life threatening and multiorgan system hypersensitivity reaction that frequently leads to cessation of operations. Despite the incidence of Cefazolin allergy being on the rise, the cases of anaphylaxis to Cefazolin during surgeries and its management are seldom reported.
We present two patients with no known beta-lactam allergy and end stage kidney disease who received perioperative intravenous Cefazolin for planned deceased kidney transplant surgery at our academic medical center. Both patients developed anaphylaxes approximately three minutes following the administration of the antibiotic and experienced severe, refractory hypotension that required the use of vasopressors. The severity of the anaphylactic reactions resulted in the cessation of the transplant operation and multiple days of intensive care unit admission.
Peri-or intraoperative anaphylaxis to Cefazolin is on the rise and its consequences in transplant candidates are even more dire given the pre-existing end organ failure, financial burden for health care system, potential loss of donor organs, and emotional burden for recipients and their families. These are the first two cases of reported Cefazolin-induced anaphylaxis that actually resulted in aborting the kidney transplant operation. In addition, cases of previously reported Type 1 hypersensitivity to Cefazolin as prophylaxis for operations were reviewed and the allergy workups were discussed.

The eustachian valve (EV) is a vestigial structure found at the junction of the inferior vena cava and the right atrium, a remnant of the embryological sinus venosus that may persist throughout life. Right-sided infective endocarditis of the eustachian valve remains a distinctly rare and under-diagnosed entity. Commonly known risk factors of eustachian valve endocarditis (EVE) are intravenous drug use, in-dwelling intracardiac devices, and central lines, although more recently immunocompromised states, e.g. uncontrolled diabetes mellitus and old age, have been recognized as risk factors for the disease. Although Staphylococcus aureus has been the most commonly implicated organism, cases of infections with gram-negative organisms are emerging. We present a 47-year-old male with uncontrolled type 1 DM who initially presented to the ED with complaints of low back pain and dysuria and was later found to have eustachian valve endocarditis ultimately treated with intravenous antibiotics.

The use of antibiotics can, in rare cases, induce neuromuscular blockade (NMB), resulting in paralytic symptoms. Although such antibiotic-induced NMB has been described in the anaesthesiology and infectious disease literature, it is an unfamiliar clinical entity in the fields of neurosurgery and spinal surgery. Herein, we report a case of periodic quadriplegia due to NMB induced by perioperative prophylactic antibiotic of cefazolin, resulting in highly confusing paralytic symptoms during the acute postoperative phase of cervical laminoplasty, together with a review of the relevant literature.

BACKGROUND: Cefazolin is a first-generation cephalosporin commonly used for skin and soft tissue infections, abdominal and orthopedic surgery prophylaxis, and methicillin-sensitive staph aureus. Cephalosporins as a whole are known potential inducers of hemolytic anemia; however, mechanism of action is primarily autoimmune, and compared to other drugs, cefazolin is the least common.
METHODS: A rare case report of cefazolin-induced hemolytic anemia \"CIHA\" and a systematic review of CIHA articles in English literature. Two authors performed review of publications and articles were selected based on inclusion and exclusion criteria. A systematic search of the literature yielded 768 entries with five case reports on cefazolin-induced hemolytic anemia.
UNASSIGNED: An 80-year-old female with methicillin-sensitive Staphylococcus aureus \"MSSA\" endocarditis. The patient was started on intravenous \"IV\" cefazolin that that resulted in hemolytic anemia and eosinophilia. Switching to vancomycin improved hemoglobin level and resolved eosinophilia. Four cefazolin-induced hemolytic anemia case reports and one population-based article with a case reported were analyzed with respect to direct antiglobulin test \"DAT\" (also known as the direct Coombs test) results, prior penicillin sensitivity, and acute anemia causes exclusion.
CONCLUSIONS: CIHA is a rare cause of clinically significant anemia. The diagnosis of drug-induced anemia is one of exclusion. It is important to consider DAT results and prior penicillin sensitivity when evaluating a patient for cefazolin-induced hemolytic anemia. However, the frequency of cefazolin use and resultant anemia necessitates early recognition of hemolytic anemia and prompt discontinuation of cefazolin, especially with long-term use.