Case report of a successful treatment of methicillin-resistant Staphylococcus aureus (MRSA) bacteremia and MRSA/vancomycin-resistant Enterococcus faecium cholecystitis by daptomycin

A Rare Case of Acute Cholecystitis Caused by Methicillin-Resistant Staphylococcus aureus (MRSA) in an Immunocompetent Person in the Absence of Bacteremia or Pre-Existing Conditions

Acute cholecystitis, typically caused by gallstone obstruction of the cystic duct, is often complicated by infection. Mostly observed in immunocompromised patients with bacteremia Methicillin-resistant Staphylococcus aureus (MRSA) is not typically associated with this ailment. Here, we present a unique case of acute cholecystitis caused by MRSA in an immunocompetent patient without bacteremia or underlying disease. A male patient aged 59 years was admitted complaining of severe abdominal pain and nausea. Subsequent investigation confirmed acute calculous cholecystitis and thereafter, the patient underwent laparoscopic cholecystectomy. Gallbladder fluid culture indicated elevated quantities of MRSA growths, and suitable antimicrobial therapy was given as part of the treatment process. This exceptional case underlines the significance of recognizing MRSA as a potential pathogen in severe acute cholecystitis cases, particularly those with severe symptoms. Rapid identification and usage of anti-MRSA antibiotics play a crucial role in managing MRSA-related situations. Healthcare providers need to bear in mind the possibility of cholecystitis associated with MRSA particularly when conventional risk factors are not present. Timely intervention is essential for favorable patient outcomes.

Tissue Penetration of Antimicrobials in Intensive Care Unit Patients: A Systematic Review—Part I

The challenging severity of some infections, especially in critically ill patients, makes the diffusion of antimicrobial drugs within tissues one of the cornerstones of chemotherapy. The knowledge of how antibacterial agents penetrate tissues may come from different sources: preclinical studies in animal models, phase I–III clinical trials and post-registration studies. However, the particular physiopathology of critically ill patients may significantly alter drug pharmacokinetics. Indeed, changes in interstitial volumes (the third space) and/or in glomerular filtration ratio may influence the achievement of bactericidal concentrations in peripheral compartments, while inflammation can alter the systemic distribution of some drugs. On the contrary, other antibacterial agents may reach high and effective concentrations thanks to the increased tissue accumulation of macrophages and neutrophils. Therefore, the present review explores the tissue distribution of beta-lactams and other antimicrobials acting on the cell wall and cytoplasmic membrane of bacteria in critically ill patients. A systematic search of articles was performed according to PRISMA guidelines, and tissue/plasma penetration ratios were collected. Results showed a highly variable passage of drugs within tissues, while large interindividual variability may represent a hurdle which must be overcome to achieve therapeutic concentrations in some compartments. To solve that issue, off-label dosing regimens could represent an effective solution in particular conditions.

Daptomycin Physiology-Based Pharmacokinetic Modeling to Predict Drug Exposure and Pharmacodynamics in Skin and Bone Tissues

BACKGROUND AND OBJECTIVE

Daptomycin has been recommended in the treatment of bone and joint infection. Previous work showed that the approved dosage of daptomycin may be insufficient to achieve optimal exposure in patients with bone and joint infection. However, those studies assumed that bone exposure was similar to steady-state daptomycin-free plasma concentrations. We sought to establish a physiologically based pharmacokinetic (PBPK) model of daptomycin to describe the dynamics of daptomycin disposition in bone and skin tissue.

METHODS

A PBPK model of daptomycin was built using PK-Sim^®. Daptomycin concentrations in plasma and bone were obtained from three previously published studies. Physicochemical drug characteristics, mass balance, anthropometrics, and experimental data were used to build and refine the PBPK model. Internal validation of the PBPK model was performed using the usual diagnostic plots. The final PBPK model was then used to run simulations with doses of 6, 8, 10, and 12 mg/kg/24 h. Pharmacokinetic profiles were simulated in 1000 subjects and the probabilities of target attainment for the area under the concentration-time curve over the bacterial minimum inhibitory concentration were computed in blood, skin, and bone compartments.

RESULTS

The final model showed a good fit of all datasets with an absolute average fold error between 0.5 and 2 for all pharmacokinetic quantities in blood, skin and bone tissues. Results of dosing simulations showed that doses ≥10 mg/kg should be used in the case of bacteremia caused by Staphylococcus aureus with a minimum inhibitory concentration >0.5 mg/L or Enterococcus faecalis with a minimum inhibitory concentration >1 mg/L, while doses ≥12 mg/kg should be used in the case of bone and joint infection or complicated skin infection. When considering a lower minimum inhibitory concentration, doses of 6-8 mg/kg would likely achieve a sufficient success rate. However, in the case of infections caused by E. faecalis with a minimum inhibitory concentration >2 mg/L, a higher dosage and combination therapy would be necessary to maximize efficacy.

CONCLUSIONS

We developed the first daptomycin PBPK/pharmacodynamic model for bone and joint infection, which confirmed that a higher daptomycin dosage is needed to optimize exposure in bone tissue. However, such higher dosages raise safety concerns. In this setting, therapeutic drug monitoring and model-informed precision dosing appear necessary to ensure the right exposure on an individual basis.

Physiologically based pharmacokinetic modeling of daptomycin dose optimization in pediatric patients with renal impairment

Background and Objective: Daptomycin is used to treat Gram-positive infections in adults and children and its dosing varies among different age groups. We focused on the pharmacokinetics of daptomycin in children with renal impairment, which has not been evaluated.

Methods: A physiologically based pharmacokinetic (PBPK) model of daptomycin was established and validated to simulate its disposition in healthy populations and adults with renal impairment, along with a daptomycin exposure simulated in pediatric patients with renal impairment.

Results: The simulated PBPK modeling results for various regimens of intravenously administered daptomycin were consistent with observed data according to the fold error below the threshold of 2. The Cmax and AUC of daptomycin did not differ significantly between children with mild-to-moderate renal impairment and healthy children. The AUC increased by an average of 1.55-fold and 1.85-fold in severe renal impairment and end-stage renal disease, respectively. The changes were more significant in younger children and could reach a more than 2-fold change. This scenario necessitates further daptomycin dose adjustments.

Conclusion: Dose adjustments take into account the efficacy and safety of the drug; however, the steady-state Cmin of daptomycin may be above 24.3 mg/L in a few instances. We recommend monitoring creatine phosphokinase more than once a week when using daptomycin in children with renal impairment.

Draft genome sequence data of a clinical Enterococcus faecalis isolate SHH039 from a patient with cholecystitis from a tertiary care hospital in Sabah, Malaysia

An Enterococcus faecalis strain SHH039 was isolated from a 68 year old man who was hospitalised with cholecystitis. The genomic sequence of this isolate which had a size of 2,990,081 bp and 2,663 proteins with functional assignments is presented here. Analysis of the genome revealed Enterococcus faecalis with multiple antibiotic resistance genes which may be associated with acute cholecystitis. It may be not clear if the infection symptoms are the consequence of enterococci manifestation. However, this opportunistic organism may play a minor role in the disease.

Clinical Pharmacokinetics of Daptomycin

Due to the low level of resistance observed with daptomycin, this antibiotic has an important place in the treatment of severe Gram-positive infections. It is the first-in-class of the group of calcium-dependent, membrane-binding lipopeptides, and is a cyclic peptide constituted of 13 amino acids and an n-decanoyl fatty acid chain. The antibacterial action of daptomycin requires its complexation with calcium. Daptomycin is not absorbed from the gastrointestinal tract and needs to be administered parenterally. The distribution of daptomycin is limited (volume of distribution of 0.1 L/kg in healthy volunteers) due to its negative charge at physiological pH and its high binding to plasma proteins (about 90%). Its elimination is mainly renal, with about 50% of the dose excreted unchanged in the urine, justifying dosage adjustment for patients with renal insufficiency. The pharmacokinetics of daptomycin are altered under certain pathophysiological conditions, resulting in high interindividual variability. As a result, therapeutic drug monitoring of daptomycin may be of interest for certain patients, such as intensive care unit patients, patients with renal or hepatic insufficiency, dialysis patients, obese patients, or children. A target for the ratio of the area under the curve to the minimum inhibitory concentration > 666 is usually recommended for clinical efficacy, whereas in order to limit the risk of undesirable muscular effects the residual concentration should not exceed 24.3 mg/L.

Global prevalence and distribution of vancomycin resistant, vancomycin intermediate and heterogeneously vancomycin intermediate Staphylococcus aureus clinical isolates: a systematic review and meta-analysis

Vancomycin-resistant Staphylococcus aureus (VRSA), Vancomycin-intermediate S. aureus (VISA) and heterogeneous VISA (hVISA) are subject to vancomycin treatment failure. The aim of the present study was to determine their precise prevalence and investigate prevalence variability depending on different years and locations. Several international databases including Medline (PubMed), Embase and Web of Sciences were searched (data from 1997 to 2019) to identify studies that addressed the prevalence of VRSA, VISA and hVISA among human clinical isolates around the world. Subgroup analyses and meta-regression were conducted to indicate potential source of variation. Publication bias was assessed using Egger's test. Statistical analyses were conducted using STATA software (version 14.0). Data analysis showed that VRSA, VISA and hVISA isolates were reported in 23, 50 and 82 studies, with an overall prevalence of 1.5% among 5855 S. aureus isolates, 1.7% among 22,277 strains and 4.6% among 47,721 strains, respectively. The overall prevalence of VRSA, VISA, and hVISA before 2010 was 1.2%, 1.2%, and 4%, respectively, while their prevalence after this year has reached 2.4%, 4.3%, and 5.3%. The results of this study showed that the frequency of VRSA, VISA and hVISA after 2010 represent a 2.0, 3.6 and 1.3-fold increase over prior years. In a subgroup analysis of different strain origins, the highest frequency of VRSA (3.6%) and hVISA (5.2%) was encountered in the USA while VISA (2.1%) was more prevalent in Asia. Meta-regression analysis showed significant increasing of VISA prevalence in recent years (p value ≤ 0.05). Based on the results of case reports (which were not included in the calculations mentioned above), the numbers of VRSA, VISA and hVISA isolates were 12, 24 and 14, respectively, among different continents. Since the prevalence of VRSA, VISA and hVISA has been increasing in recent years (especially in the Asian and American continents), rigorous monitoring of vancomycin treatment, it's the therapeutic response and the definition of appropriate control guidelines depending on geographical regions is highly recommended and essential to prevent the further spread of vancomycin-resistant S. aureus.

Antibiotics in the Biliary Tract: A Review of the Pharmacokinetics and Clinical Outcomes of Antibiotics Penetrating the Bile and Gallbladder Wall

Biliary tract infections (BTIs), including cholangitis and cholecystitis, are common causes of bacteremia. Bacteremic BTIs are associated with a mortality rate of 9-12%. The extent to which antibiotics are excreted in the bile and the ratio of their exposure to the minimum inhibitory concentration of the infecting organism are among the important factors for the treatment of BTIs. This review updates health care professionals on the distribution of antibiotics in the common bile duct, gallbladder, and gallbladder wall. Antibiotic efficacy in treating BTIs based on the latest available clinical studies is also discussed. The efficacy and pharmacokinetics of 50 antibiotics are discussed. Overall, most antibiotic classes exhibit biliary penetration that translates into clinical efficacy. Only seven antibiotics (amoxicillin, cefadroxil, cefoxitin, ertapenem, gentamicin, amikacin, and trimethoprim/sulfamethoxazole) had poor biliary penetration profiles. Three antibiotics (ceftibuten, ceftolozane/tazobactam, and doripenem) had positive clinical outcomes despite the lack of pharmacokinetic studies on their penetration into the biliary tract. Conflicting efficacy data were reported for ampicillin despite adequate biliary penetration, whereas conflicting pharmacokinetic data were reported with cefaclor and moxifloxacin. Even in the absence of supportive clinical studies, antibiotics with good biliary penetration profiles may have a place in the treatment of BTIs.

A new validated HPLC-UV method for therapeutic monitoring of daptomycin in comparison with reference mass spectrometry

Daptomycin, a cyclic lipopeptide antibiotic with a broad spectrum of activity against Gram-positive bacteria, is also active against multi-resistant bacterial strains, as well as methicillin-resistant S. aureus, vancomycin-resistant enterococci or penicillin-resistant S. pneumoniae. For these reasons it is a viable alternative for the treatment of persisting infections. However, the therapeutic drug monitoring of daptomycin is recommended because the known variability in drug disposition and the severe clinical conditions of patients. Therefore, we developed a simple and fast UV-HPLC method according to FDA guidelines to monitor plasma concentrations of the drug. Briefly, after a liquid-liquid extraction, plasma calibration samples, quality controls and patients' samples were injected in a HPLC instrument and peaks of daptomycin and gentamicin (internal standard) were resolved by a C₁₈ 250 × 4.6 mm, 5 μm stationary phase and peaks were monitored at UV = 262 nm. Mobile phase (isocratic flow of 1 mL/min) consisted of acetonitrile-buffer (KH₂PO₄ 20 mM pH = 3.2) 46:54, vol/vol. Under these conditions, IS and daptomycin peaked at 4.1 and 5.8 min after injection. Values of limits of detection and quantitation accounted for 1.65 and 5.00 (μg/ml), respectively. Values of method linearity (r²) in range 5-100 mg/L were 0.9975 and 0.9956 plasma samples and solvent standard, respectively. Inter- and intra-day variability coefficients were lower than 15 %. The comparison with a reference, commercially-available LC-MS/MS method on 122 patient plasma samples returned excellent correlation (r² = 0.9474). In conclusion, the present method demonstrated to be reliable and suitable for daptomycin TDM in clinical routine.

Failure of daptomycin β-Lactam combination therapy to prevent resistance emergence in Enterococcus faecium

Daptomycin β-Lactam combination therapy offers "protection" against daptomycin non-susceptibility (DNS) development in Enterococcus faecium. We report failure of this strategy and the importance of source control. Mutations were detected in the LiaF and cls genes in DNS isolates. A single DNS isolate contained an unrecognized mutation, which requires confirmation.

Persistent bacteraemia caused by Staphylococcus aureus in the gall bladder

Staphylococcus aureusbacteraemia (SAB) remains a complex disease with a high associated morbidity and mortality, especially when it is able to establish an occult nidus safe from antimicrobial eradication. Without rapid identification and intervention, the nidus can cause persistent relapse of disease, morbidity and mortality. Having a high clinical suspicion for the foci of occult S. aureus is important, and awareness of potential sites of infection is critical and can be life-saving.We present a unique case of a 65-year-old man with end-stage renal disease receiving haemodialysis who developed septic shock from SAB. Despite 18 days of appropriate antibiotics, the patient had persistent high-grade bacteraemia until his gall bladder was ultimately percutaneously drained. The day after drainage, he cleared his blood cultures, although he ultimately passed away as he decided to transition his care to focus on comfort measures.

Hiding in Fresh Fruits and Vegetables: Opportunistic Pathogens May Cross Geographical Barriers

Different microbial groups of the microbiome of fresh produce can have diverse effects on human health. This study was aimed at identifying some microbial communities of fresh produce by analyzing 105 samples of imported fresh fruits and vegetables originated from different countries in the world including local samples (Oman) for aerobic plate count and the counts of Enterobacteriaceae, Enterococcus, and Staphylococcus aureus. The isolated bacteria were identified by molecular (PCR) and biochemical methods (VITEK 2). Enterobacteriaceae occurred in 60% of fruits and 91% of vegetables. Enterococcus was isolated from 20% of fruits and 42% of vegetables. E. coli and S. aureus were isolated from 22% and 7% of vegetables, respectively. Ninety-seven bacteria comprising 21 species were similarly identified by VITEK 2 and PCR to species level. E. coli, Klebsiella pneumoniae, Enterococcus casseliflavus, and Enterobacter cloacae were the most abundant species; many are known as opportunistic pathogens which may raise concern to improve the microbial quality of fresh produce. Phylogenetic trees showed no relationship between clustering of the isolates based on the 16S rRNA gene and the original countries of fresh produce. Intercountry passage of opportunistic pathogens in fresh produce cannot be ruled out, which requires better management.

Spontaneous Bacterial Peritonitis Due to Methicillin-Resistant Staphylococcus Aureus in a Patient with Cirrhosis: The Potential Role for Daptomycin and Review of the Literature

Gram-positive cocci are emerging causes of spontaneous bacterial peritonitis (SBP), especially in patients with healthcare-associated infections. We report the case of a 68-year-old man with hepatitis C virus and alcohol-related cirrhosis who developed SBP due to methicillin-resistant Staphylococcus aureus treated with daptomycin. We discuss the potential role of daptomycin in this setting with a review of the literature about the use of daptomycin in primary or secondary bacterial peritonitis.

Bacterial biliary tract infections in liver transplant recipients

PURPOSE OF REVIEW

The purpose of this study is to provide an overview of bacterial biliary tract infections in liver transplant recipients with a focus on pathogenesis and conservative treatment strategies.

RECENT FINDINGS

The development of interventional endoscopic and radiologic interventions has improved the outcome of conservative treatments for bile tract strictures and bilomas. However, recent data show an important rise of infections with multidrug-resistant (MDR) pathogens in liver transplant recipients.

SUMMARY

Both recurrent cholangitis and infected bilomas are bacterial biliary tract infections in liver transplant recipients responsible for significant morbidity and graft loss, which require a multidisciplinary approach. Risk factors for biliary tract strictures and bilomas formation have recently been identified. With the improved outcome of a conservative management including prolonged and/or recurrent antibiotic treatments, the risk of selecting resistant pathogens is increased. There is an urgent need to develop new strategies to reduce the risk of secondary infections by MDR isolates in liver transplant recipients.

A current perspective on daptomycin for the clinical microbiologist

Daptomycin is a lipopeptide antimicrobial with in vitro bactericidal activity against Gram-positive bacteria that was first approved for clinical use in 2004 in the United States. Since this time, significant data have emerged regarding the use of daptomycin for the treatment of serious infections, such as bacteremia and endocarditis, caused by Gram-positive pathogens. However, there are also increasing reports of daptomycin nonsusceptibility, in Staphylococcus aureus and, in particular, Enterococcus faecium and Enterococcus faecalis. Such nonsusceptibility is largely in the context of prolonged treatment courses and infections with high bacterial burdens, but it may occur in the absence of prior daptomycin exposure. Nonsusceptibility in both S. aureus and Enterococcus is mediated by adaptations to cell wall homeostasis and membrane phospholipid metabolism. This review summarizes the data on daptomycin, including daptomycin's unique mode of action and spectrum of activity and mechanisms for nonsusceptibility in key pathogens, including S. aureus, E. faecium, and E. faecalis. The challenges faced by the clinical laboratory in obtaining accurate susceptibility results and reporting daptomycin MICs are also discussed.

Population pharmacokinetics of daptomycin in patients affected by severe Gram-positive infections

A population pharmacokinetic analysis of daptomycin was performed based on therapeutic drug monitoring (TDM) data from 58 patients receiving doses of 4-12 mg/kg for the treatment of severe Gram-positive infections. At a daily dose of 8 mg/kg, daptomycin plasma concentrations (mean ± S.D.) were 76.9 ± 9.8 mg/L at the end of infusion and 52.7 ± 15.4 mg/L and 11.4 ± 5.4 mg/L at 0.5 h and 23 h after drug administration, respectively. The final model was a one-compartmental model with first-order elimination, with estimated clearance (CL) of 0.80 ± 0.14 L/h and a volume of distribution (V(d)) of 0.19 ± 0.05 L/kg. Creatinine clearance (CL(Cr)) was identified as having a significant influence on daptomycin CL, and a decrease in CL(Cr) of 30 mL/min from the median value (80 mL/min) was associated with a reduction of daptomycin CL from 0.80 L/h to 0.73 L/h. These results confirm that the presence of severe infection may be associated with an altered disposition of daptomycin, with an increased Vd. MICs were available in 41 patients and results showed that 38 and 31 subjects achieved AUC/MIC values associated with bacteriostatic (>400) and bactericidal effects (>800), respectively. Of note, 31 of these 41 subjects experienced a clinical improvement or were cured. Although daptomycin pharmacokinetics may be influenced by infections, effective AUC/MIC values were achieved in the majority of patients. The present model may be applied in clinical settings for a TDM routine on the basis of a sparse blood sampling protocol.

Antibacterial effects of plant-derived extracts on methicillin-resistant Staphylococcus aureus

Natural chemicals have been reported to have antibacterial effects against a variety of bacteria. The present study evaluated the antibacterial effects of commercially available grape-seed extract (GSE), pomegranate polyphenols (PP), and lab-prepared cranberry proanthocyanidins (C-PAC) against two strains of methicillin-resistant Staphylococcus aureus (MRSA). GSE, PP, and C-PAC at concentrations of 2 mg/mL, 10 mg/mL, or controls were mixed with equal volumes of overnight cultures of MRSA at ~6 log₁₀ colony-forming units (CFU)/mL and incubated for 0, 1, 2, 8, and 24 h at 37°C. Treatments were neutralized/stopped using tryptic soy broth containing 3% beef extract. Serial dilutions of the treated MRSA strains and controls were spread-plated on trypticase soy agar and incubated for 24-48 h at 37°C and colonies were counted. Among the three tested agents, GSE at 1 and 5 mg/mL was found to be most effective against MRSA, resulting in a 2.9-4.0 log₁₀ CFU/mL reduction of both strains after 2 h at 37°C. PP at 1 and 5 mg/mL was found to cause 1.1-2.3 log₁₀ CFU/mL reduction, while C-PAC at 1 mg/mL caused <1 log₁₀ CFU/mL reduction of the two MRSA strains after 2 h at 37°C. All three extracts at the tested concentrations decreased the two MRSA strains to undetectable levels within 24 h, with the exception of 1 mg/mL PP for strain 33591. Scanning electron microscopy of MRSA after 2 h of treatment showed that GSE and PP caused bacterial cell wall alteration, with negligible effect observed by C-PAC treatment. However, the in vivo activity and clinical safety applications of GSE, PP, and C-PAC need to be evaluated before suggestion for use as a treatment/control measure.

Successful treatment of methicillin-resistant Staphylococcus aureus bacteraemia and cholecystitis

Although Staphylococcus aureus can cause a variety of infections, involvement of the biliary tract is rare. We present a middle-aged Caucasian woman who presented with methicillin-resistant S aureus (MRSA) bacteraemia. Subsequent investigation revealed a diagnosis of acute cholecystitis with MRSA-positive specimen cultures. The patient showed clinical improvement after vancomycin therapy and laparoscopic cholecystectomy. This case adds to the growing list of infections that can be attributed to MRSA.