Pharmacokinetics of long-acting cephapirin and cloxacillin after intramammary administration in dairy goats

Determining the pharmacokinetics of intramammary antimicrobials in goats can assist in predicting appropriate meat and milk withdrawal intervals for drugs that are effective at treating subclinical mastitis due to non-aureus Staphylococci during the dry period. Twenty-four healthy, lactating does were enrolled in this study. Half were administered 300 mg of cephapirin benzathine (ToMORROW, Boehringer Ingelheim Vetmedica, Duluth, GA) via intramammary infusion into each half of the udder. The remaining does had 500 mg cloxacillin benzathine (Orbenin DC, Merck & Co., Rahway, NJ) administered per half. Plasma was collected before treatment and for 7 days post-treatment followed by analysis via liquid chromatography with tandem mass spectroscopy. Pharmacokinetic parameters were determined using noncompartmental methods via commercial software (MonolixSuite). The mean maximum concentration (Cmax) of cephapirin of 0.073 μg/mL was noted at 7.06 h post-administration (Tmax). The area under the plasma concentration curve based on the final sampling point (AUClast) was 1.06 h × μg/mL. The mean residence time until the final sampling point (MRTlast) was 13.55 h. Mean terminal half-life (T½) of cephapirin was 6.98 h. In CLOX does, Cmax was 0.074 μg/mL with a Tmax of 18 h, AUClast was 5.71 h × μg/mL, T½ was 77.45 h, and MRTlast was 65.36 h. Despite both products being formulated with benzathine salts, marked differences were noted in pharmacokinetic parameters including AUC, T1/2, and MRTlast. This data will be used to plan sampling schedules for milk and tissue residue depletion studies for both products.

Assessment of Molecularly Imprinted Polymers as Selective Solid-Phase Extraction Sorbents for the Detection of Cloxacillin in Drinking and River Water

This paper describes a new methodology for carrying out quantitative extraction of cloxacillin from drinking and river water samples using a molecularly imprinted polymer (MIP) as a selective sorbent for solid-phase extraction (MISPE). Several polymers were synthesized via thermal polymerization using cloxacillin as a template, methacrylic acid (MAA) as a functional monomer, ethyleneglycoldimethacrylate (EGDMA) as a cross-linker and different solvents as porogens. Binding characteristics of the adequate molecularly imprinted and non-imprinted (NIP) polymers were evaluated via batch adsorption assays following the Langmuir and Freundlich isotherms and Scatchard assays. The parameters related to the extraction approach were studied to select the most appropriate polymer for cloxacillin determination. Using the optimized MIP as the SPE sorbent, a simple sample treatment methodology was combined with high-performance liquid chromatography (HPLC) to analyze cloxacillin residues in drinking and river water. Under the optimum experimental conditions, the MISPE methodology was validated using spiked samples. The linearity for cloxacillin was assessed within the limits of 0.05-1.5 µg L-1 and the recovery percentage was higher than 98% (RSD < 4%). The limits of detection and limits of quantification were 0.29 and 0.37 µg L-1 and 0.8 and 0.98 µg L-1 for drinking and river water, respectively. The selectivity of MIP against other ß-lactam antibiotics with similar structures (oxacillin, cefazoline, amoxicillin and penicillin V) was studied, obtaining a good recovery higher than 85% for all except cefazoline. The proposed MISPE-HPLC methodology was successfully applied for the detection of cloxacillin in drinking water from Canal de Isabel II (Madrid) and river water from the Manzanares River (Madrid).

Synergistic Combinations of FDA-Approved Drugs with Ceftobiprole against Methicillin-Resistant Staphylococcus aureus

New strategies are urgently needed to address the public health threat of antimicrobial resistance. Synergistic agent combinations provide one possible pathway toward addressing this need and are also of fundamental mechanistic interest. Effective methods for comprehensively identifying synergistic agent combinations are required for such efforts. In this study, an FDA-approved drug library was screened against methicillin-resistant Staphylococcus aureus (MRSA) (ATCC 43300) in the absence and presence of sub-MIC levels of ceftobiprole, a PBP2a-targeted anti-MRSA β-lactam. This screening identified numerous potential synergistic agent combinations, which were then confirmed and characterized for synergy using checkerboard analyses. The initial group of synergistic agents (sum of the minimum fractional inhibitory concentration ∑FIC_min ≤0.5) were all β-lactamase-resistant β-lactams (cloxacillin, dicloxacillin, flucloxacillin, oxacillin, nafcillin, and cefotaxime). Cloxacillin-the agent with the greatest synergy with ceftobiprole-is also highly synergistic with ceftaroline, another PBP2a-targeted β-lactam. Further follow-up studies revealed a range of ceftobiprole synergies with other β-lactams, including with imipenem, meropenem, piperacillin, tazobactam, and cefoxitin. Interestingly, given that essentially all other ceftobiprole-β-lactam combinations showed synergy, ceftaroline and ceftobiprole showed no synergy. Modest to no synergy (0.5 < ∑FIC_min ≤ 1.0) was observed for several non-β-lactam agents, including vancomycin, daptomycin, balofloxacin, and floxuridine. Mupirocin had antagonistic activity with ceftobiprole. Flucloxacillin appeared particularly promising, with both a low intrinsic MIC and good synergy with ceftobiprole. That so many β-lactam combinations with ceftobiprole show synergy suggests that β-lactam combinations can generally increase β-lactam effectiveness and may also be useful in reducing resistance emergence and spread in MRSA. IMPORTANCE Antimicrobial resistance represents a serious threat to public health. Antibacterial agent combinations provide a potential approach to combating this problem, and synergistic agent combinations-in which each agent enhances the antimicrobial activity of the other-are particularly valuable in this regard. Ceftobiprole is a late-generation β-lactam antibiotic developed for MRSA infections. Resistance has emerged to ceftobiprole, jeopardizing this agent's effectiveness. To identify synergistic agent combinations with ceftobiprole, an FDA-approved drug library was screened for potential synergistic combinations with ceftobiprole. This screening and follow-up studies identified numerous β-lactams with ceftobiprole synergy.

Chitosan can improve antimicrobial treatment independently of bacterial lifestyle, biofilm biomass intensity and antibiotic resistance pattern in non-aureus staphylococci (NAS) isolated from bovine clinical mastitis

Bovine mastitis is the most frequent and costly disease that affects dairy cattle. Non-aureus staphylococci (NAS) are currently one of the main pathogens associated with difficult-to-treat intramammary infections. Biofilm is an important virulence factor that can protect bacteria against antimicrobial treatment and prevent their recognition by the host's immune system. Previously, we found that chronic mastitis isolates which were refractory to antibiotic therapy developed strong biofilm biomass. Now, we evaluated the influence of biofilm biomass intensity on the antibiotic resistance pattern in strong and weak biofilm-forming NAS isolates from clinical mastitis. We also assessed the effect of cloxacillin (Clx) and chitosan (Ch), either alone or in combination, on NAS isolates with different lifestyles and abilities to form biofilm. The antibiotic resistance pattern was not the same in strong and weak biofilm producers, and there was a significant association (p ≤ 0.01) between biofilm biomass intensity and antibiotic resistance. Bacterial viability assays showed that a similar antibiotic concentration was effective at killing both groups when they grew planktonically. In contrast, within biofilm the concentrations needed to eliminate strong producers were 16 to 128 times those needed for weak producers, and more than 1,000 times those required for planktonic cultures. Moreover, Ch alone or combined with Clx had significant antimicrobial activity, and represented an improvement over the activity of the antibiotic on its own, independently of the bacterial lifestyle, the biofilm biomass intensity or the antibiotic resistance pattern. In conclusion, the degree of protection conferred by biofilm against antibiotics appears to be associated with the intensity of its biomass, but treatment with Ch might be able to help counteract it. These findings suggest that bacterial biomass should be considered when designing new antimicrobial therapies aimed at reducing antibiotic concentrations while improving cure rates.

Strong Biofilm Formation and Low Cloxacillin Susceptibility in Biofilm-Growing CC398 Staphylococcus aureus Responsible for Bacteremia in French Intensive Care Units, 2021

A prospective 3-month study carried out in 267 ICUs revealed an S. aureus nosocomial bacteremia in one admitted patient out of 110 in adult and pediatric sectors, and in one out of 230 newborns; 242 S. aureus bacteremias occurred during the study, including 7.9% MRSA-bacteremias. In one ICU out of ten, the molecular characteristics, antimicrobial susceptibility profiles and biofilm production of the strains responsible for S. aureus bacteremia were studied. Of the 53 strains studied, 9.4% were MRSA and 52.8% were resistant to erythromycin. MLST showed the predominance of CC398 (37.7% of the strains) followed by CC8 (17.0%), CC45 (13.2%) and CC30 (9.4%). The lukF/S genes were absent from our isolates and tst-1 was found in 9.4% of the strains. Under static conditions and without exposure to glucose, biofilm production was rare (9.4% of the strains, without any CC398). The percentage increased to 62.3% for strains grown in broth supplemented with 1% glucose (including 7 out of 9 CC8 and 17 out of the 20 CC398). Further study of the CC398, including whole genome sequencing, revealed (1) highly frequent patient death within seven days after CC398 bacteremia diagnosis (47.4%), (2) 95.0% of the strains producing biofilm when exposed to sub-inhibitory concentrations of cloxacillin, (3) a stronger biofilm production following exposure to cloxacillin than that observed in broth supplemented with glucose only (p < 0.001), (4) a high minimum biofilm eradication concentration of cloxacillin (128 mg/L) indicating a low cloxacillin susceptibility of biofilm-growing CC398, (5) 95.0% of the strains carrying a ϕSa-3 like prophage and its particular evasion cluster (i.e., yielding chp and scin genes), and (6) 30.0% of the strains carrying a ϕMR11-like prophage and yielding a higher ability to produce biofilm. Our results provide evidence that active surveillance is required to avoid spreading of this virulent staphylococcal clone.

The Effect of Short-Chain Fatty Acids on Growth of Cryptosporidium parvum In Vitro

In a previous study, we observed an increase in the severity of cryptosporidial infection corresponding to decreased levels of short-chain fatty acids (SCFAs). Therefore, we decided to examine the effect of SCFAs on Cryptosporidium growth in human ileocecal adenocarcinoma (HTC-8) cells. HTC-8 cells were infected with 1 × 105 C. parvum oocysts. After 48 h of incubation with selected SCFAs, cells were fixed and labeled with monoclonal antibody directed to all intracellular stages, and the number of parasites was quantitated using a fluorescent microscope. Acetate, butyrate, propionate and valproate significantly inhibited growth, with an EC50 between 4 and 10 mM. Additionally, when combined, butyrate, acetate and propionate showed increased efficacy. Butyrate also inhibited growth when incubated with sporozoites prior to infection of host cell monolayers. In addition, we looked at possible mechanisms of action of inhibition. A combination of C. parvum infection and butyrate treatment led to increases in apoptosis and certain inflammatory cytokines. We conclude that acetate, propionate and butyrate have direct inhibitory activities in host cells against C. parvum, and butyrate can also affect sporozoite infectivity directly. While not preventing infection, SCFAs may help in keeping the infection low or in check.

Cloxacillin-induced acute vanishing bile duct syndrome: a case study and literature review

Ductopenia is often regarded as a chronic process where ≥50% of portal tracts lack bile ducts, which is also known as vanishing bile duct syndrome (VBDS). One etiology is drug-induced liver injury. Cloxacillin, an anti-staphylococcal penicillin, typically causes "bland" cholestasis. We present the first case of cloxacillin-induced acute ductopenia or VBDS and a review of published cloxacillin-induced liver injuries. A 66-year-old woman with no prior liver disease, but known penicillin allergy, was treated for post-carotid angioplasty staphylococcal infection with 6 weeks of cloxacillin. She presented with a two-week history of weakness and jaundice. Laboratory work-up showed elevated liver enzymes with a cholestatic pattern, hyperbilirubinemia, and eosinophilia. She required ICU transfer for hypotension and was started empirically on prednisone. Liver biopsy revealed severe centrilobular cholestasis, mild necroinflammation, and ductopenia with epithelial injury, but no ductular reaction. Two-month later, she was discharged on hydrocortisone and ursodiol with persistently elevated alkaline phosphatase and bilirubin. She was considered for liver transplantation but died of liver failure four months later. Four additional articles were found with histopathologic descriptions of cloxacillin-related liver injury. These included portal inflammation, cholestasis and mild necroinflammation. Clinical features were reported in two cases; both had mild symptoms with cholestatic liver enzymes and hyperbilirubinemia. Both patients recovered completely within 10-60 days. Cloxacillin-induced cholestasis can be secondary to acute ductopenia, which can result in worse clinical outcomes than previously described "bland" cholestasis. Liver biopsy is recommended to identify cases with acute VBDS.

Carbapenemase-Producing Gram-Negative Bacteria in Andalusia, Spain, 2014-2018

The emergence and spread of carbapenemase-producing gram-negative bacteria is a major public health concern. We used data collected from microbiology laboratories as part of the PIRASOA program during 2014-2018 to study the epidemiology of carbapenemase-producing bacteria in Andalusia, Spain. Our findings highlight the importance of ongoing surveillance and epidemiologic studies for these bacteria.

Incidence and Risk Factors for Acute Kidney Injury during the Treatment of Methicillin-Sensitive Staphylococcus aureus Infections with Cloxacillin Based Antibiotic Regimens: A French Retrospective Study

BACKGROUND

Cloxacillin has been associated with the occurrence of acute kidney injury (AKI). The incidence of this complication in the literature is low (2.5-3.5%) and probably underestimated, since most studies were done by selecting the presence of AKI in discharge codes.

OBJECTIVES

The primary goal was to define the incidence of AKI in patients with a methicillin-sensitive Staphylococcus aureus infection treated with cloxacillin based antibiotic regimens. The secondary goals were to identify the risk factors associated with this complication and to describe the characteristics of AKI.

PATIENTS AND METHODS

We carried out a retrospective study. The inclusion criteria were adult patients hospitalized in a medical department at the Le Mans Hospital between 1 July 2012 and 1 July 2019 with a diagnosis of methicillin-sensitive Staphylococcus aureus infection treated with cloxacillin.

RESULTS

One hundred twenty-three patients were included in the study. Forty-two patients (34.2%) developed AKI. In the multivariate analysis, age, the use of diuretics and the presence of endocarditis were independently associated with AKI. Age was associated with an OR of 4.38 (p = 0.002) for patients older than 75, being treated with diuretics was associated with an OR of 2.94 (p = 0.036) for loop diuretics and an OR of 3.05 (p = 0.027) for non-loop diuretics; type of infection was associated with an OR of 3.42 (p = 0.012) for endocarditis.

CONCLUSIONS

The occurrence of AKI is frequent during cloxacillin based antibiotic regimens for methicillin-sensitive Staphylococcus aureus infections. Being older than 75, being treated with diuretics and the presence of endocarditis were the main risk factors for AKI in our population.

Adjunctive Daptomycin in the Treatment of Methicillin-susceptible Staphylococcus aureus Bacteremia: A Randomized, Controlled Trial

BACKGROUND

Bloodstream infections (BSIs) with methicillin-susceptible Staphylococcus aureus (MSSA) are associated with significant morbidity and mortality. Our objective in this study was to determine the efficacy of synergistic treatment with daptomycin when given with either cefazolin or cloxacillin for the treatment of MSSA BSI.

METHODS

A randomized, double-blind, placebo-controlled trial was performed at 2 academic hospitals in Montreal, Canada. Patients aged ≥18 years with MSSA BSI receiving either cefazolin or cloxacillin monotherapy were considered for inclusion. In addition to the standard-of-care treatment, participants received a 5-day course of adjunctive daptomycin or placebo. The primary outcome was the duration of MSSA BSI in days.

RESULTS

Of 318 participants screened, 115 were enrolled and 104 were included in the intention-to-treat analysis (median age, 67 years; 34.5% female). The median duration of bacteremia was 2.04 days among patients who received daptomycin vs 1.65 days in those who received placebo (absolute difference, 0.39 days; P = .40). In a modified intention-to-treat analysis that involved participants who remained bacteremic at the time of enrollment, we found a median duration of bacteremia of 3.06 days among patients who received daptomycin vs 3.0 days in those who received placebo (absolute difference, 0.06 days; P = .77). Ninety-day mortality in the daptomycin arm was 18.9% vs 17.7% in the placebo arm (P = 1.0).

CONCLUSIONS

Among patients with MSSA BSIs, the administration of adjunctive daptomycin therapy to standard-of-care treatment did not shorten the duration of bacteremia and should not be routinely considered.

CLINICAL TRIALS REGISTRATION

NCT02972983.

Efficacy Prediction of Four Pharmaceutical Formulations for Intramammary Administration Containing Aloe vera (L.) Burm. f. Combined With Ceftiofur or Cloxacillin in Lactating Cows as an Alternative Therapy to Treat Mastitis Caused by Staphylococcus aureus

Synergy or additive effect between Aloe vera (L.) Burm.f. and beta-lactam (β-lactam) antibiotics has been reported against Staphylococcus aureus, one of the most important etiological agents of cow mastitis. The goal of the present study was to predict the efficacy of intramammary formulations containing the Aloe vera gel extract in the combination with cloxacillin or ceftiofur at low concentrations in lactating cows as an alternative therapy. Each quarter of 20 healthy Holstein Friesian lactating cows were treated with a single dose of one of the following formulations, corresponding to one of these treatment groups: A1, A2, A3, and A4. A1 and A2 contained cloxacillin at 0.25 and 0.5 mg/ml, whereas A3 and A4 contained ceftiofur 0.25 and 0.5 mg/ml, respectively. In addition, all formulations contained 600 mg/ml of an alcoholic extract of Aloe vera. Milk samples were taken at predefined time points. Antibiotics and aloin (active compound of Aloe vera) concentrations were assessed by liquid chromatography mass spectrometry system (LC-MS/MS). Pharmacokinetic profiles were obtained, and the efficacy index, the fraction of dosing interval in which the antimicrobial concentration remains above the minimum inhibitory concentrations (MICs) (T > MIC) for each formulation, was calculated considering MIC values against Staphylococcus aureus ATCC 29213 as obtained for the combination Aloe vera + antibiotic and aloin concentration in the extract. Mammary gland safety assessment was performed for each combination. Values of the main efficacy index for this study, T > MIC (h) for Aloe vera were 23.29, 10.50, 27.50, and 13.89, whereas for cloxacillin or ceftiofur were 19.20, 10.9, 19.74, and 15.63, for A1, A2, A3, and A4, respectively. Only A1 and A3 reached aloin and antibiotic recommended values as predictors of clinical efficacy for cloxacillin, ceftiofur, and aloin (50, 70, and 60%, respectively), assuming a dose interval of 24 h. The efficacy index values obtained suggest that A1 and A3 might be an effective therapy to treat bovine mastitis caused by S. aureus after a single dose. Nevertheless, further trials in S. aureus mastitis clinical cases are mandatory to confirm the efficacy of Aloe vera formulations.

A Population Pharmacokinetic Analysis of Continuous Infusion of Cloxacillin during Staphylococcus aureus Bone and Joint Infections

Intravenous administration of antibiotics is recommended during the early phase of methicillin-susceptible S. aureus (MSSA) bone and joint infection (BJI). We sought to compare the plasma concentrations of cloxacillin administered alternately by continuous and intermittent infusion (CI and ItI) in patients with MSSA BJI. In this prospective crossover trial, patients were randomly assigned to receive either 3 days of CI (two 75-mg/kg 12-h cloxacillin infusions per day) and then 3 days of ItI (four 37.5-mg/kg 1-h cloxacillin infusions per day) or vice versa. The drug concentration measurement was performed on day 3 of each type of administration at 1, 6, and 11 h and at 1, 2, 3, 4, and 6 h after the beginning of CI and ItI, respectively. We used the nonparametric algorithm NPAG to estimate population pharmacokinetic (PK) parameters. The final model was used to perform pharmacokinetic/pharmacodynamic (PK/PD) simulations and calculate the probabilities of target attainment (PTA) for several ItI and CI dosing regimens. We considered two PK/PD targets of time spent above the MIC for free cloxacillin concentrations (fT _>MIC): 50 and 100%. Eighty-four concentrations from 11 patients were analyzed. A two-compartment model adequately described the data. ItI with q6h regimens and short 1-h infusions of 2,000 or 3,000 mg were associated with low PTA, even for the low target (50% fT _>MIC) while 3-h infusions and continuous infusions (6 to 12 g/day) were associated with a PTA of >90% for an MIC up to 0.5 mg/liter. These results support the use of prolonged or continuous infusion of cloxacillin in patients with BJI.

A Randomized Controlled Trial of Teat-Sealant and Antibiotic Dry-Cow Treatments for Mastitis Prevention Shows Similar Effect on the Healthy Milk Microbiome

Lactating cows are routinely treated at dry-off with antibiotic infusions in each quarter for the cure and prevention of pathogenic intramammary infection, which remains the most common disease in dairy herds. This approach is known as blanket dry-cow therapy, usually effective for the prevention and cure of infections, but has been shown to potentially contribute to the emergence and spreading of antibiotic resistant bacterial strains. Exploring the use of non-antibiotic treatments coupled with selective dry-cow therapy is necessary to reduce the risk of antibiotic resistance and potential interference with milk microbiome balance. The impact of selective dry-cow therapy on the physiological milk microbiome needs to be carefully evaluated. In this small-scale trial, five healthy (no mastits, SCC <200,000 cells mL-1) second-parity cows from dry-off to 5 days after calving were sampled. For every cow, each quarter received a different treatment: (i) bismuth salnitrate (internal teat sealant, OrbSeal®, Zoetis, Italy), front right quarter; (ii) cephalonium dihydrate (Cepravin®, MSD, Italy), rear right quarter; (iii) benzathine cloxacillin (Cloxalene dry, Ati, Italy), rear left quarter. No treatment was applied to the remaining quarter (front left) which served as experimental control. For 16S rRNA gene sequencing, bacterial DNA was extracted from 5 ml of milk samples, amplified using the primers for the V3-V4 hypervariable regions and sequenced in one MiSeq (Illumina) run with 2 × 250-base paired-end reads. Bacteriological results confirmed that the quarters were all healthy. The phyla Proteobacteria, Firmicutes, and Actinobacteria were the most abundant for all treatments and controls at all three timepoints, accounting for over 80% of the entire milk microbiota composition. No significant differences were found between treatments and controls in terms of the major alpha and beta diversity indexes, revealing that antibiotic, and non-antibiotic treatments for selective dry-cow therapy did not alter significantly the milk microbiome of dairy cows. The milk microbiota composition showed a clear evolution over the lactation cycle, and the overall changes in the milk microbiota diversity over the lactation cycle were mainly independent of treatments.

Changes in the Microbiome of Cryptosporidium-Infected Mice Correlate to Differences in Susceptibility and Infection Levels

Cryptosporidium spp. are opportunistic protozoan parasites that infect epithelial cells of the small intestine, causing diarrheal illness in humans. Differences in severity may be due to the immunological status of the host, malnutrition or prior exposure but may also be due to differences in the host gut flora. We examined changes in bacterial flora following antibiotic treatment to determine how cryptosporidial infections and gut integrity were affected by alterations in the microbiome. DNA was extracted from fecal and intestinal samples during peak infection. V4 region amplicons were generated and sequenced using 16sRNA on an Illumina MiSeq. Species evenness and richness were estimated using the Shannon diversity index. There was a significant decrease in anaerobes and overgrowth of Enterobacteriaceae in mice treated with cloxacillin. We also examined levels of short-chain fatty acids in fecal samples. There was a significant decrease in acetate, propionate, and butyrate in these same mice. Concurrent with the shift in bacterial infection was a significant increase in severity of cryptosporidial infection and increase in gut permeability. Treatment with other antibiotics significantly altered the microbiome but did not change the infection, suggesting that specific alterations in the host microbiome allow for more favorable growth of the parasite.

Efficacy of cloxacillin versus cefazolin for methicillin-susceptible Staphylococcus aureus bacteraemia (CloCeBa): study protocol for a randomised, controlled, non-inferiority trial

INTRODUCTION

Methicillin-susceptible Staphylococcus aureus (MSSA) bacteraemia is a common and severe disease responsible for approximately 65 000 deaths every year in Europe. Intravenous antistaphylococcal penicillins (ASP) such as cloxacillin are the current recommended antibiotics. However, increasing reports of toxicity and recurrent stock-outs of ASP prompted healthcare providers to seek for alternative antibiotic treatment. Based on retrospective studies, cefazolin, a first-generation cephalosporin, is recommended in patients at risk of severe ASP-associated toxicity.We hypothesised that cefazolin has a non-inferior efficacy in comparison to cloxacillin, with a better safety profile for the treatment of MSSA bacteraemia.

METHODS AND ANALYSIS

The CloCeBa trial is an open-label, randomised, controlled, non-inferiority trial conducted in academic centres throughout France. Eligible patients are adults with MSSA bacteraemia without intravascular device or suspicion of central nervous system infection. Patients will be randomised (1:1) to receive either cloxacillin or cefazolin by the intravenous route, for the first 14 days of therapy. The evaluation criteria is a composite criteria of negative blood cultures at day 5, survival, absence of relapse and clinical success at day 90 after randomisation. Secondary evaluation criteria include both efficacy and safety assessments. Three ancillary studies are planned to describe the epidemiology of β-lactamase encoding genes, the ecological impact and pharmacokinetic/pharmacodynamic parameters of cefazolin and cloxacillin. Including 300 patients will provide 80% power to demonstrate the non-inferiority of cefazolin over cloxacillin, assuming 85% success rate with cloxacillin and taking into account loss-to-follow-up, with a 0.12 non-inferiority margin and a one-sided type I error of 0.025.

ETHICS AND DISSEMINATION

This protocol received authorisation from the ethics committee Sud-Est I on 13 November 2017 (2017-87-PP)and French National Agency for Medicines and Health Products (170661A-43). Results will be disseminated to the scientific community through congresses and publication in peer-reviewed journals.

TRIAL REGISTRATION NUMBER

NCT03248063 and 2017-003967-36.

Combination of Cloxacillin and Essential Oil of Melaleuca armillaris as an Alternative Against Staphylococcus aureus

The emergence of resistance to antibiotics has been favored by abuse in the application of antimicrobials in human and animal medicine. Essential oils are a great resource to deal with this crisis. Melaleuca armillaris belongs to the family of Myrtaceae, rich in species with essential oils. Plant extracts has shown antimicrobial activity in many investigations. Cloxacillin (CLOX) is an antibiotic widely used in veterinary medicine against Staphylococcus aureus. Our aim was to assess pharmacodynamic interaction established by combining essential oil of M. armillaris (EO) with CLOX in search of a synergistic effect that maximizes the antibacterial activity against S. aureus. The EO was obtained by steam distillation and its composition was analyzed by a GC-FID-MS. The most abundant components in the EO were 1.8 cineole (72.3%), limonene (7.8%). and α-pinene (6%). We worked with wild type S. aureus strains (n = 3) isolated from Holstein cows, and S. aureus ATCC 29213 as the reference strain. The Minimum Inhibitory Concentration (MIC) of CLOX, EO and the combination was determined by microdilution in broth at pH 7.4; 6.5 and 5.0. The checkerboard method was applied to evaluate the interaction between CLOX and EO. The Fractional Inhibitory Concentration index (FIC) was established. From those combinations that yielded the lowest FIC values, we evaluated the index of antibacterial activity (E), established as the difference between the Log₁₀ values of the number of viable bacteria at the initial (nt₀) and at the end of the test (nt₂₄). So, time-killing curves with CLOX and EO/CLOX combination at 0.5, 1, 2, 4, and 8 fold the MIC in broth at pH 7.4; 6.5 and 5.0 were prepared. We considered Bacteriostatic effect (E = 0) Bactericidal effect (E = -3) and Effect of virtual eradication of bacteria (E = -4). A clear synergic activity between the EO and the CLOX was demonstrated, which allows reducing the MIC of β-lactam against S. aureus. This interaction was favored by acidification of the medium, where lower concentrations of CLOX achieved a bactericidal effect, close to virtual eradication, in the presence of small amounts of EO.

Successful desensitization to cloxacillin in a patient with sepsis, with infective endocarditis and clinical suspicion of hypersensitivity to penicillins, a case report

WHAT IS KNOWN AND OBJECTIVE

Beta-lactam antibiotic (BLA) therapy is frequently needed to treat infective endocarditis (IE). Hypersensitive reactions to BLA restrict BLA therapy in allergic patients. In the current case, we aim to describe the utility of desensitization (DS) in this context. Although the evidence is limited, DS is recommended.

CASE DESCRIPTION

This case report deals with a 79-year-old woman with a clinical suspicion of allergy to BLA and a methicillin-sensitive Staphylococcus aureus (MSSA) IE. A cloxacillin DS protocol was developed to enable treatment with cloxacillin.

WHAT IS NEW AND CONCLUSION

Alternative antibiotic treatments may be less effective or not available in MSSA IE. In this case report, DS allowed optimal cloxacillin treatment.

The Combination of Daptomycin and Fosfomycin Has Synergistic, Potent, and Rapid Bactericidal Activity against Methicillin-Resistant Staphylococcus aureus in a Rabbit Model of Experimental Endocarditis

We investigated whether the addition of fosfomycin or cloxacillin to daptomycin provides better outcomes in the treatment of methicillin-resistant Staphylococcus aureus (MRSA) experimental aortic endocarditis in rabbits. Five MRSA strains were used to perform in vitro time-kill studies using standard (10⁶) and high (10⁸) inocula. Combined therapy was compared to daptomycin monotherapy treatment in the MRSA experimental endocarditis model. A human-like pharmacokinetics model was applied, and the equivalents of cloxacillin at 2 g/4 h, fosfomycin at 2 g/6 h, and daptomycin at 6 to 10 mg/kg/day were administered intravenously. A combination of daptomycin and either fosfomycin or cloxacillin was synergistic in the five strains tested at both inocula. A bactericidal effect was detected in four of five strains tested with both combinations. The MRSA-277 strain (vancomycin MIC, 2 μg/ml) was used for the experimental endocarditis model. Daptomycin plus fosfomycin significantly improved the efficacy of daptomycin monotherapy at 6 mg/kg/day in terms of both the proportion of sterile vegetations (100% versus 72%, P = 0.046) and the decrease in the density of bacteria within the vegetations (P = 0.025). Daptomycin plus fosfomycin was as effective as daptomycin monotherapy at 10 mg/kg/day (100% versus 93%, P = 1.00) and had activity similar to that of daptomycin plus cloxacillin when daptomycin was administered at 6 mg/kg/day (100% versus 88%, P = 0.48). Daptomycin nonsusceptibility was not detected in any of the isolates recovered from vegetations. In conclusion, for the treatment of MRSA experimental endocarditis, the combination of daptomycin plus fosfomycin showed synergistic and bactericidal activity.

Acute kidney injury during treatment with high-dose cloxacillin: a report of 23 cases and literature review

BACKGROUND

International guidelines recommend high-dose cloxacillin for endocarditis or osteoarticular infections due to methicillin-susceptible staphylococci. However, data on the tolerability of these regimens are scarce.

METHODS

We used the computerized registry of suspected drug-related adverse events in our institution. Cases of acute kidney injury (AKI), as defined by KDIGO, in patients receiving high-dose cloxacillin were retrospectively reviewed. Data were collected from medical charts on a standardized questionnaire.

RESULTS

From 2009 to 2015, 23 consecutive patients (16 men, 7 women) with a median age of 75 years (interquartile range [IQR], 66-80) fulfilled inclusion criteria. By the time of AKI diagnosis, patients were treated with a median cloxacillin dose of 12 g/day (IQR, 10-12) after a median duration of 7 days (IQR, 4-10). Most patients (n=20) fulfilled RIFLE criteria for failure, with a median peak serum creatinine concentration of 339 µmol/L (IQR, 249-503). Urinalysis was indicative of tubular disease in 7 patients, 3 had hypereosinophilia and 8 had abnormal liver function tests. All patients presented at least one risk factor for AKI, including concomitant nephrotoxic drugs: gentamicin (n=19), diuretics (n=15), angiotensin-converting enzyme inhibitors (n=8) and angiotensin II receptor-blockers (n=6). Thirteen patients (57%) had cloxacillin plasma concentrations >50 µg/mL. Thirteen patients (57%) had complete recovery of renal function.

CONCLUSIONS

AKI during high-dose cloxacillin treatment mostly occurs in elderly patients taking concomitant nephrotoxic drugs. The outcome is usually favourable after cloxacillin discontinuation. Therapeutic drug monitoring may decrease the risk of AKI in patients treated with high-dose cloxacillin.

A comparison of the effect of short-acting and long-acting cloxacillin-based dry-cow therapy on somatic cell counts after calving in cows also given internal teat sealants

AIM

To compare, in cows treated with an internal teat sealant, the effect of short-acting and long-acting cloxacillin-based dry-cow therapy on somatic cell counts (SCC) after calving.

METHODS

Cows from a spring-calving, pasture-based dairy farm in the Manawatu-Whanganui region of New Zealand were randomly allocated to receive either a short-acting cloxacillin and ampicillin dry-cow therapy and internal teat sealant (n=291) or a long-acting cloxacillin and ampicillin dry-cow therapy and internal teat sealant (n=288) at the end of lactation. Cows were managed on-farm with routine husbandry procedures through the dry period and following calving. A multivariable logistic regression model was used to determine the association between length of action of dry-cow therapy and the proportion of cows with a SCC >150,000 cells/mL at the first herd test after calving.

RESULTS

Age of cow, mean SCC for the preceding season and interval from calving to the first post-calving herd test were all associated with the proportion of cows with an individual SCC >150,000 cells/mL at the first herd test (p<0.001) Treatment with the short-acting dry-cow therapy was not associated with decreased odds of cows having a SCC >150,000 cells/mL at the first herd test compared with treatment with long-acting dry-cow therapy (OR=0.724; 95% CI=0.40-1.30).

CONCLUSIONS AND CLINICAL RELEVANCE

In this herd, which routinely used internal teat sealants, the use of short-acting cloxacillin-based dry-cow therapy did not result in an increased proportion of cows with elevated SSC post-calving. This was a single farm, single year study but indicates that in this herd, changing from a long-acting to a short-acting antimicrobial may have no impact on the prevalence of subclinical mastitis.

Cloxacillin control of experimental arthritis induced by SEC(+) Staphylococcus aureus is associated with downmodulation of local and systemic cytokines

Staphylococcus aureus is the most common agent of septic arthritis (SA) that is a severe, rapidly progressive and erosive disease. In this work we investigated the clinical, histopathological and immunological characteristics of the SA triggered by an enterotoxin C producer S. aureus strain. The effect of a β-lactamic antibiotic over disease evolution and cytokine production was also evaluated. After confirmation that ATCC 19095 SEC(+) strain preserved its ability to produce enterotoxin C, this bacteria was used to infect C57BL/6 male mice. Body weight, clinical score and disease prevalence were daily evaluated during 14 days. Cytokine production by splenocytes, cytokine mRNA expression in arthritic lesions, transcription factors mRNA expression in inguinal lymph nodes and histopathological analysis were performed 7 and 14 days after infection. ATCC 19095 SEC(+) strain caused a severe arthritis characterized by weight loss, high clinical scores and a 100% disease prevalence. Histopathological analysis revealed inflammation, pannus formation and bone erosion. Arthritis aggravation was associated with elevated production of pro-inflammatory cytokines, higher local mRNA expression of these cytokines and also higher mRNA expression of T-bet, ROR-γ and GATA-3. Disease control by cloxacillin was associated with decreased production of pro-inflammatory cytokines but not of IL-10. These findings indicate that the ATCC 19095 SEC(+) strain is able to initiate a severe septic arthritis in mice associated with elevated cytokine production that can be, however, controlled by cloxacillin.

Compatibility of Cloxacillin Sodium with Selected Intravenous Drugs During Simulated Y-Site Administration

BACKGROUND

Data regarding Y-site compatibility of intravenous (IV) cloxacillin sodium with other drugs are scarce and incomplete.

OBJECTIVE

To establish the compatibility of IV cloxacillin with 89 injectable drugs during simulated Y-site administration.

METHODS

Cloxacillin sodium (10 mL, 100 mg/mL) was combined with 89 undiluted IV drugs (10 mL, each). Tests were duplicated and performed at room temperature. Visual evaluation and a light obscuration particle count test were performed on 1 of the 2 solutions immediately after mixing. The second mixture underwent visual evaluation after 15 minutes, 1 hour, and 4 hours, followed by a particle count test at 4 hours. Drugs were considered incompatible if the mixture precipitated or became turbid within the 4-hour period or exceeded the particle count limit allowed by Test 1.B of USP <788> initially or at 4 hours.

RESULTS

Of the 89 tested drugs, 64 were compatible for up to 4 hours. The remaining 25 drugs were incompatible. Of these incompatible drugs, 16 were identified visually, and 9 were identified by the light obscuration particle count test.

CONCLUSIONS

Sixty-four IV drugs were found to be compatible with cloxacillin via simulated Y-site, whereas 25 drugs were found to be incompatible with the antibiotic. The light obscuration particle count test should be used to complement visual evaluation when samples do not precipitate immediately.

Effect of vancomycin minimal inhibitory concentration on the outcome of methicillin-susceptible Staphylococcus aureus endocarditis

BACKGROUND

Staphylococcus aureus endocarditis has a high mortality rate. Vancomycin minimum inhibitory concentration (MIC) has been shown to affect the outcome of methicillin-resistant S. aureus bacteremia, and recent data point to a similar effect on methicillin-susceptible S. aureus bacteremia. We aimed to evaluate the effect of vancomycin MIC on left-sided S. aureus infective endocarditis (IE) treated with cloxacillin.

METHODS

We analyzed a prospectively collected cohort of patients with IE in a single tertiary-care hospital. Vancomycin, daptomycin, and cloxacillin MIC was determined by E-test. S. aureus strains were categorized as low vancomycin MIC (<1.5 µg/mL) and high vancomycin MIC (≥1.5 µg/mL). The primary endpoint was in-hospital mortality.

RESULTS

We analyzed 93 patients with left-sided IE treated with cloxacillin, of whom 53 (57%) had a vancomycin MIC < 1.5 µg/mL and 40 (43%) a vancomycin MIC ≥ 1.5 µg/mL. In-hospital mortality was 30% (n = 16/53) in patients with a low vancomycin MIC and 53% (n = 21/40) in those with a high vancomycin MIC (P = .03). No correlation was found between oxacillin MIC and vancomycin or daptomycin MIC. Logistic regression analysis showed that higher vancomycin MIC increased in-hospital mortality 3-fold (odds ratio, 3.1; 95% confidence interval, 1.2-8.2) after adjustment for age, year of diagnosis, septic complications, and nonseptic complicated endocarditis.

CONCLUSIONS

Our results indicate that vancomycin MIC could be used to identify a subgroup of patients with methicillin-susceptible S. aureus IE at risk of higher mortality. The worse outcome of staphylococcal infections with a higher vancomycin MIC cannot be explained solely by suboptimal pharmacokinetics of antibiotics.

Medication error - Inadvertent high dose intradermal cloxacillin induced skin necrosis

Medication error is one of the important causes of preventable adverse drug reactions. It can occur in the form of administration of a wrong drug, in the wrong dose, to the wrong patient, in an unsuitable dosage form, for the wrong duration or by using an inappropriate route of administration. Intradermal skin testing for cloxacillin hypersensitivity is done at low doses to check for drug allergy. In this report, three patients were given 50 times higher dose of cloxacillin than recommended for skin testing, resulting in pain and necrosis at the site of injection. The error occurred due to wrong dilution of the drug as done by a nursing intern. Some reasons for this could be overtime working, under trained staff, unsupervised nursing interns, complicated and unclear protocols, interpersonal communication gap between health care professionals and also poor availability of ideal resources. Pharmacovigilance centers must alert health care professionals about the significance of reporting medication errors through bulletins and journals.

Comparative Study of RP-HPLC and UV Spectrophotometric Techniques for the Simultaneous Determination of Amoxicillin and Cloxacillin in Capsules

Reversed-phase HPLC and UV spectrophotometric techniques using water as solvent have been developed and validated for the simultaneous determination of amoxicillin and cloxacillin in capsules. For both techniques, the linearity range of 60.073x2013;140.0 µg/mL was studied. The spectrophotometric data show that non-derivative techniques, such as absorbance ratio and compensation, and ratio spectra first-order derivative could be successfully used for the co-assay of amoxicillin and cloxacillin. Based on the statistical comparison of spectrophotometric and chromatographic data, the interchangeability between HPLC and UV spectrophotometric techniques has been suggested for the routine analysis.

High-dose cefazolin on consecutive hemodialysis in anuric patients with Staphylococcal bacteremia

Methicillin-sensitive Staphylococcus aureus (MSSA) bacteremia is a leading cause of infection in hemodialysis (HD) patients. Cloxacillin, cefazolin, and vancomycin are the mainstay antimicrobials. Cloxacillin administration leads to frequent drug dosing, longer length of stay (LOS), and higher cost, while resistance and poorer outcomes are associated with vancomycin use. Dosing cefazolin during HD allows for prolonged blood therapeutic levels. We assessed the outcomes and safety of a strategy of treating MSSA bacteremia with 2-3 g cefazolin on HD only. All HD patients with MSSA bacteremia admitted in June-December 2009 at our center and receiving this regime were compared with historical controls who received cloxacillin. Demographic characteristics and outcome measures like mortality, LOS, cost, recrudescence, and adverse drug reactions were assessed. Of 27 consecutive episodes reviewed, 14 and 13 patients received cefazolin and cloxacillin, respectively. Baseline demographics were comparable between the 2 treatment groups. More than one-third of the bacteremia was related to tunneled catheter infection. The 30-day mortality of cloxacillin- and cefazolin-treated patients was 15% and 7%, respectively (P=0.14). Two of the 11 survivors treated with cloxacillin (18%) had recrudescent bacteremia while none was observed in cefazolin-treated survivors. Cefazolin was associated with shorter LOS (10 vs. 20 days, P<0.05) and lower cost (US$8262.00 vs. US$15,367.00, P<0.05). Cefazolin use resulted in 3 idiosyncratic adverse drug reactions. Cefazolin dosed on each HD in MSSA bacteremia leads to earlier discharge and less cost. Larger prospective studies are, however, warranted to fully assess its safety and efficacy.

Severe cholestatic hepatitis following cloxacillin treatment

We describe a 77-year-old woman who developed fatigue, fever, a maculopapular rash and severe cholestatic hepatitis two weeks after receiving cloxacillin and ofloxacin.

Inactivation of D-alanine carboxypeptidase by penicillins and cephalosporins is not lethal in Bacillus subtilis

The D-alanine carboxypeptidase of Bacillus subtilis is a particulate enzyme that is irreversibly inactivated by penicillins and cephalosporins. However, the lethal concentrations of these antibiotics are not the same as those that inhibit enzymatic activity in vitro. 6-Aminopenicillanic acid inactivates at least 95% of the enzyme at nonlethal concentrations. Conversely, cephalothin is lethal at concentrations that do not inactivate the enzyme. Experiments with intact, growing cells confirm the results obtained in vitro. Therefore, a killing site distinct from the carboxypeptidase must be postulated.