Developing an intervention package to optimise the management of vancomycin therapy using theory informed co-design

BACKGROUND

Optimising the management of vancomycin by achieving target therapeutic concentrations early during therapy has been associated with reduced mortality and morbidity. Despite the availability of guidelines and training, the management of vancomycin remains suboptimal.

OBJECTIVES

The primary outcome was the development of interventions and associated implementation strategies to optimise the management of vancomycin therapy. This paper describes how co-design process was used to build a theory informed intervention package, which was implemented across a wide range of in-patient hospital settings in Queensland, Australia.

METHODS

This multiple methods study was conducted in four phases: 1) a baseline audit to identify the nature of the problem and associated determinants informed by stakeholder interviews 2) mapping these findings to the Theoretical Domains Framework (TDF) to identify behavioural correlates and modifiers 3) prioritising the behavioural modifiers and associated implementation strategies to inform a protype of the intervention in a series of co-design sessions and 4) implementing and evaluating the intervention package. The study was conducted across the four teaching hospitals in a large Queensland Hospital and Health Service across multiple healthcare disciplines namely nurses, doctors, and pharmacists. This intervention package was subsequently implemented across Queensland Health with the support of the local champions under the guidance of the steering group.

RESULTS

Clinicians identified that a multifaceted intervention package and training which can be tailored to the health-care professional disciplines, would be best suited to shift clinician behaviour to align with guidelines. The findings from the co-design process aligned with theory-informed intervention package. Each of the intervention strategies varied in their frequency and popularity of use.

CONCLUSIONS

The use of theory-informed and participatory approach assisted with the intervention development process and aligned the intervention content with the priorities of stakeholders. The TDF provided a structured process for developing intervention content which is both acceptable and useful to stakeholders and may improve the management of vancomycin.

An in vitro dynamic bioreactor model for evaluating antimicrobial effectiveness on periodontal polymicrobial biofilms: a proof-of-concept study

BACKGROUND

The aim of this study was to investigate an in vitro dynamic bioreactor model by evaluating the antimicrobial effect of clinically relevant amoxicillin doses on polymicrobial microcosm biofilms derived from subgingival plaque.

METHODS

Biofilms from pooled subgingival plaque were grown for 108  hours in control and experimental dynamic biofilm reactors. Amoxicillin was subsequently infused into the experimental reactor to simulate the pharmacokinetic profile of a standard 500 mg thrice-daily dosing regimen over 5 days and biofilms were assessed by live/dead staining, scanning electron microscopy, and quantitative polymerase chain reaction.

RESULTS

Following establishment of the oral microcosm biofilms, confocal imaging analysis showed a significant increase in dead bacteria at 8 hours (p = 0.0095), 48 hours (p = 0.0070), 96 hours (p = 0.0140), and 120 hours (p < 0.0001) in the amoxicillin-treated biofilms compared to the control biofilms. Nevertheless, viable bacteria remained in the center of the biofilm at all timepoints. Significant reductions/elimination in Campylobacter rectus, Tannerella forsythia, Aggregatibacter actinomycetemcomitans, and Peptostreptococcus anaerobius was observed among the amoxicillin-treated biofilms at the 96 and 120 hour timepoints.

CONCLUSION

A novel in vitro dynamic model of oral microcosm biofilms was effective in modeling the antimicrobial effect of a pharmacokinetically simulated clinically relevant dose of amoxicillin.

Evaluation of the stability of ceftazidime/avibactam in elastomeric infusion devices used for outpatient parenteral antimicrobial therapy utilizing a national stability protocol framework

Objectives

To evaluate the stability of ceftazidime/avibactam in elastomeric infusers, utilizing the UK's Yellow Cover Document (YCD) stability testing framework, in conditions representative of OPAT practice.

Methods

Ceftazidime/avibactam was reconstituted with sodium chloride 0.9% (w/v) in two elastomeric infusers at concentrations (dose) levels of 1500/375, 3000/750 and 6000 mg/1500 mg in 240 mL. The infusers were exposed to a fridge storage (2°C-8°C) for 14 days followed by 24 h in-use temperature (32°C).

Results

After 14 days of fridge storage and subsequent 24 h exposure to 32°C, mean ± SD of ceftazidime percent remaining was 75.5% ± 1.8%, 79.9% ± 1.1%, 82.4% ± 0.6%, for Easypump, and 81.7% ± 1.2%, 82.5% ± 0.5%, 85.4% ± 1.1% for Dosi-Fuser devices at the high, intermediate and low doses tested, respectively. For avibactam, mean ± SD percent remaining was 83.2% ± 1.8%, 87.4% ± 2.0%, 93.1% ± 0.9% for Easypump, and 85.1% ± 2.0%, 86.7% ± 0.1%, 92.5% ± 0.1% for Dosi-Fuser devices. The cumulative amount of pyridine generated in the devices ranged from 10.4 mg at low dose to 76.9 mg at high dose. Regression-based simulation showed that the degradation of both ceftazidime and avibactam was <10% for at least 12 h of the running phase, if stored in a fridge for not more than 72 h prior to in-use temperature exposure.

Conclusions

Whilst not meeting the strict UK YCD criteria for ≤5% degradation, ceftazidime/avibactam may be acceptable to administer as a continuous 12 hourly infusion in those territories where degradation of ≤10% is deemed acceptable.

Evaluation of Fosfomycin-Sulbactam Combination Therapy against Carbapenem-Resistant Acinetobacter baumannii Isolates in a Hollow-Fibre Infection Model

Static concentration in vitro studies have demonstrated that fosfomycin- or sulbactam-based combinations may be efficacious against carbapenem-resistant Acinetobacter baumannii (CRAB). In the present study, we aimed to evaluate the bacterial killing and resistance suppression potential of fosfomycin-sulbactam combination therapies against CRAB isolates in a dynamic infection model. We simulated clinically relevant dosing regimens of fosfomycin (8 g every 8 h, 1 h infusion) and sulbactam (12 g continuous infusion or 4 g every 8 h, 4 h infusion) alone and in combination for 7 days in a hollow-fibre infection model (HFIM) against three clinical isolates of CRAB. The simulated pharmacokinetic profiles in the HFIM were based on fosfomycin and sulbactam data from critically ill patients. Fosfomycin monotherapy resulted in limited bacterial killing. Sulbactam monotherapies resulted in ~ 3 to 4 log10 kill within the first 8 to 32 h followed by regrowth of up to 8 to 10 log10 CFU/mL. A combination of fosfomycin and continuous infusion of sulbactam led to a ~2 to 4 log10 reduction in bacterial burden within the first 24 h, which was sustained throughout the duration of the experiments. A combination of fosfomycin and extended infusion of sulbactam produced a ~4 log10 reduction in colony count within 24 h. This study demonstrated that fosfomycin in combination with sulbactam is a promising option for the treatment of MDR A. baumannii. Further studies are needed to further assess the potential clinical utility of this combination.

Pharmacodynamic evaluation of intermittent versus extended and continuous infusions of piperacillin/tazobactam in a hollow-fibre infection model against Escherichia coli clinical isolates

OBJECTIVES

To compare the bacterial killing and emergence of resistance of intermittent versus prolonged (extended and continuous infusions) infusion dosing regimens of piperacillin/tazobactam against two Escherichia coli clinical isolates in a dynamic hollow-fibre infection model (HFIM).

METHODS

Three piperacillin/tazobactam dosing regimens (4/0.5 g 8 hourly as 0.5 and 4 h infusions and 12/1.5 g/24 h continuous infusion) against a ceftriaxone-susceptible, non-ESBL-producing E. coli 44 (Ec44, MIC 2 mg/L) and six piperacillin/tazobactam dosing regimens (4/0.5 g 8 hourly as 0.5 and 4 h infusions and 12/1.5 g/24 h continuous infusion; 4/0.5 g 6 hourly as 0.5 and 3 h infusions and 16/2 g/24 h continuous infusion) were simulated against a ceftriaxone-resistant, AmpC- and ESBL-producing E. coli 50 (Ec50, MIC 8 mg/L) in a HFIM over 7 days (initial inoculum ∼107 cfu/mL). Total and less-susceptible subpopulations and MICs were determined.

RESULTS

All simulated dosing regimens against Ec44 exhibited 4 log10 of bacterial killing over 8 h without regrowth and resistance emergence throughout the experiment. For Ec50, there was the initial bacterial killing of 4 log10 followed by regrowth to 1011 cfu/mL within 24 h against all simulated dosing regimens, and the MICs for resistant subpopulations exceeded 256 mg/L at 72 h.

CONCLUSIONS

Our study suggests that, for critically ill patients, conventional intermittent infusion, or prolonged infusions of piperacillin/tazobactam may suppress resistant subpopulations of non-ESBL-producing E. coli clinical isolates. However, intermittent, or prolonged infusions may not suppress the resistant subpopulations of AmpC- and ESBL-producing E. coli clinical isolates. More studies are required to confirm these findings.

Evaluating Mono- and Combination Therapy of Meropenem and Amikacin against Pseudomonas aeruginosa Bacteremia in the Hollow-Fiber Infection Model

Debate continues as to the role of combination antibiotic therapy for the management of Pseudomonas aeruginosa infections. We studied the extent of bacterial killing by and the emergence of resistance to meropenem and amikacin as monotherapies and as a combination therapy against susceptible and resistant P. aeruginosa isolates from bacteremic patients using the dynamic in vitro hollow-fiber infection model. Three P. aeruginosa isolates (meropenem MICs of 0.125, 0.25, and 64 mg/L) were used, simulating bacteremia with an initial inoculum of ~1 × 105 CFU/mL and the expected pharmacokinetics of meropenem and amikacin in critically ill patients. For isolates susceptible to amikacin and meropenem (isolates 1 and 2), the extent of bacterial killing was increased with the combination regimen compared with the killing by monotherapy of either antibiotic. Both the combination and meropenem monotherapy were able to sustain bacterial killing throughout the 7-day treatment course, whereas regrowth of bacteria occurred with amikacin monotherapy after 12 h. For the meropenem-resistant P. aeruginosa isolate (isolate 3), only the combination regimen demonstrated bacterial killing. Given that tailored antibiotic regimens can maximize potential synergy against some isolates, future studies should explore the benefit of combination therapy against resistant P. aeruginosa. IMPORTANCE Current guidelines recommend that aminoglycosides should be used in combination with β-lactam antibiotics as initial empirical therapy for serious infections, and otherwise, patients should receive β-lactam antibiotic monotherapy. Given the challenges associated with studying the clinical effect of different antibiotic strategies on patient outcomes, useful data for subsequent informed clinical testing can be obtained from in vitro models like the hollow-fiber infection model (HFIM). Based on the findings of our HFIM, we propose that the initial use of combination therapy with meropenem and amikacin provides some bacterial killing against carbapenem-resistant P. aeruginosa isolates. For susceptible isolates, combination therapy may only be of benefit in specific patient populations, such as critically ill or immunocompromised patients. Therefore, clinicians may want to consider using the combination therapy for the initial management and ceasing the aminoglycosides once antibiotic susceptibility results have been obtained.

Pharmacodynamic Evaluation of a Single Dose versus a 24-Hour Course of Multiple Doses of Cefazolin for Surgical Prophylaxis

The optimal perioperative duration for the administration of cefazolin and other prophylactic antibiotics remains unclear. This study aimed to describe the pharmacodynamics of cefazolin for a single 2 g dose versus a 24 h course of a 2 g single dose plus a 1 g eight-hourly regimen against methicillin-susceptible Staphylococcus aureus. Static concentration time-kill assay and a dynamic in vitro hollow-fibre infection model simulating humanised plasma and interstitial fluid exposures of cefazolin were used to characterise the pharmacodynamics of prophylactic cefazolin regimens against methicillin-sensitive Staphylococcus aureus clinical isolates. The initial inoculum was 1 × 105 CFU/mL to mimic a high skin flora inoculum. The static time-kill study showed that increasing the cefazolin concentration above 1 mg/L (the MIC) did not increase the rate or the extent of bacterial killing. In the dynamic hollow-fibre model, both dosing regimens achieved similar bacterial killing (~3-log CFU/mL within 24 h). A single 2 g dose may be adequate when low bacterial burdens (~104 CFU/mL) are anticipated in an immunocompetent patient with normal pharmacokinetics.

Epidemiology of extended-spectrum β-lactamase and metallo-β-lactamase-producing Escherichia coli in South Asia

Aim: To determine the prevalence of extended-spectrum β-lactamase (ESBL) and metallo-β-lactamase (MBL)-producing Escherichia coli in South Asia. Methodology: A systematic review and meta-analysis of data published in PubMed, EMBASE, Web of Science and Scopus. Results: The pooled prevalence of ESBL and MBL-producing E. coli in South Asia were 33% (95% CI: 27-40%) and 17% (95% CI: 12-24%), respectively. The prevalence of bla_CTX-M type was 58% (95% CI: 49-66%) with bla_CTX-M-15 being the most prevalent (51%, 95% CI: 40-62%) variant. The most prevalent MBL variant was bla_NDM-1 (33%, 95% CI: 20-50%). Conclusion: This study suggests a high prevalence of ESBLs and MBLs among E. coli clinical isolates. Comprehensive resistance surveillance is required to guide clinicians prescribing antibiotics in South Asia.

Impact of the Epithelial Lining Fluid Milieu on Amikacin Pharmacodynamics Against Pseudomonas aeruginosa

Background

Even though nebulised administration of amikacin can achieve high epithelial lining fluid concentrations, this has not translated into improved patient outcomes in clinical trials. One possible reason is that the cellular and chemical composition of the epithelial lining fluid may inhibit amikacin-mediated bacterial killing.

Objective

The objective of this study was to identify whether the epithelial lining fluid components inhibit amikacin-mediated bacterial killing.

Methods

Two amikacin-susceptible (minimum inhibitory concentrations of 2 and 8 mg/L) Pseudomonas aeruginosa isolates were exposed in vitro to amikacin concentrations up to 976 mg/L in the presence of an acidic pH, mucin and/or surfactant as a means of simulating the epithelial lining fluid, the site of bacterial infection in pneumonia. Pharmacodynamic modelling was used to describe associations between amikacin concentrations, bacterial killing and emergence of resistance.

Results

In the presence of broth alone, there was rapid and extensive (> 6 − log₁₀) bacterial killing, with emergence of resistance identified in amikacin concentrations < 976 mg/L. In contrast, the rate and extent of bacterial killing was reduced (≤ 5 − log₁₀) when exposed to an acidic pH and mucin. Surfactant did not appreciably impact the bacterial killing or resistance emergence when compared with broth alone for either isolate. The combination of mucin and an acidic pH further reduced the rate of bacterial killing, with the maximal bacterial killing occurring 24 h following initial exposure compared with approximately 4–8 h for either mucin or an acidic pH alone.

Conclusions

Our findings indicate that simulating the epithelial lining fluid antagonises amikacin-mediated killing of P. aeruginosa, even at the high concentrations achieved following nebulised administration.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40268-021-00344-5.

Pharmacodynamics of once- versus twice-daily dosing of nebulized amikacin in an in vitro Hollow-Fiber Infection Model against 3 clinical isolates of Pseudomonas aeruginosa

This study aims to compare the bacterial killing of once- versus twice-daily nebulized amikacin against Pseudomonas aeruginosa and to determine the optimal duration of therapy. Three clinical P. aeruginosa isolates (amikacin MICs 2, 8, and 64 mg/L) were exposed to simulated epithelial lining fluid exposures of nebulized amikacin with dosing regimens of 400 mg and 800 mg once- or twice-daily up to 7-days using the in vitro hollow-fiber infection model. Quantitative cultures were performed. Simulated amikacin dosing regimens of 400 mg twice-daily and 800 mg once-daily achieved ≥2-log reduction in the bacterial burden within the first 24-hours of therapy for all isolates tested. No dosing regimen suppressed the emergence of amikacin resistance. No difference in bacterial killing or regrowth was observed between 3- and 7-days of amikacin. Amikacin doses of 800 mg once-daily for up to 3-days may be considered for future clinical trials.

Pharmacodynamic evaluation of intermittent versus extended and continuous infusions of piperacillin/tazobactam in a hollow-fibre infection model against Klebsiella pneumoniae

OBJECTIVES

To compare bacterial killing and the emergence of resistance to piperacillin/tazobactam, administered by intermittent versus prolonged infusion (i.e. extended or continuous), for ceftriaxone-resistant Klebsiella pneumoniae clinical isolates in an in vitro dynamic hollow-fibre infection model (HFIM).

METHODS

K. pneumoniae 68 (Kp68; MIC = 8 mg/L, producing SHV-106 and DHA-1) and K. pneumoniae 69 (Kp69; MIC = 1 mg/L, producing CTX-M-14) were studied in the HFIM over 7 days (initial inoculum ~107 cfu/mL). Six piperacillin/tazobactam dosing regimens for Kp68 (4/0.5 g 8 hourly as 0.5 and 4 h infusions, 12/1.5 g/24 h continuous infusion, 4/0.5 g 6 hourly as 0.5 and 3 h infusions and 16/2 g/24 h continuous infusion) and three piperacillin/tazobactam dosing regimens for Kp69 (4/0.5 g 8 hourly as 0.5 and 4 h infusions and 12/1.5 g/24 h continuous infusion) were simulated (piperacillin clearance = 14 L/h, creatinine clearance = 100 mL/min). Total and resistant populations and MICs were quantified/determined.

RESULTS

For Kp68, all simulated dosing regimens exhibited approximately 4 log10 of bacterial killing at 8 h followed by regrowth to approximately 1011 cfu/mL within 24 h. The MICs for resistant subpopulations exceeded 256 mg/L at 72 h. Similarly, for Kp69, all simulated dosing regimens exhibited approximately 4 log10 of bacterial killing over 8 h; however, only the continuous infusion prevented bacterial regrowth.

CONCLUSIONS

Compared with intermittent infusion, prolonged infusion did not increase initial bacterial killing and suppression of regrowth of plasmid-mediated AmpC- and ESBL-producing K. pneumoniae. However, continuous infusion may suppress regrowth of some ESBL-producing susceptible K. pneumoniae, although more data are warranted to confirm this observation.

Non-polymyxin-based combinations as potential alternatives in treatment against carbapenem-resistant Acinetobacter baumannii infections

Due to limited therapeutic options, combination therapy has been used empirically to treat carbapenem-resistant Acinetobacter baumannii (CRAB). Polymyxin-based combinations have been widely studied and used in the clinical setting. However, the use of polymyxins is often limited due to nephrotoxicity and neurotoxicity. This study aimed to evaluate the activity of non-polymyxin-based combinations relative to polymyxin-based combinations and to identify potential synergistic and bactericidal two-drug non-polymyxin-based combinations against CRAB. In vitro activity of 14 two-drug combinations against 50 A. baumannii isolates was evaluated using the checkerboard method. Subsequently, the two best-performing non-polymyxin-based combinations from the checkerboard assay were explored in static time-kill experiments. Concentrations of antibiotics corresponding to the fractional inhibitory concentrations (FIC) and the highest serum concentration achievable clinically were tested. The most synergistic combinations were fosfomycin/sulbactam (synergistic against 37/50 isolates; 74%), followed by meropenem/sulbactam (synergistic against 28/50 isolates; 56%). No antagonism was observed for any combination. Both fosfomycin/sulbactam and meropenem/sulbactam combinations exhibited bactericidal and synergistic activity against both isolates at the highest clinically achievable concentrations in the time-kill experiments. The meropenem/sulbactam combination displayed synergistic and bactericidal activity against one of two strains at concentrations equal to the FIC. Non-polymyxin-based combinations such as fosfomycin/sulbactam and meropenem/sulbactam may have a role in the treatment of CRAB. Further in vivo and clinical studies are required to scrutinise these activities further.

Continuous Ambulatory Peritoneal Dialysis in South Africa -A Four-Year Experience

This study describes our experience with continuous ambulatory peritoneal dialysis (CAPD) over a four year period, during which 88 patients were offered CAPD. It compares and contrasts the response to CAPD among four racial groups in Natal viz asiatics, blacks, coloureds and whites. Peritonitis -the major complication, occurred with an overall incidence of one episode every 4.41 patient months. CAPD remains a useful alternative therapy in developing countries where a high percentage of patients with chronic renal failure would be denied a chronic renal failure program because of lack of expertise in hemodialysis and/or renal transplantation, or limited financial resources.

Continuous ambulatory peritoneal dialysis (CAPD) was first described by Moncrief and Popovich (1) and, since its modification by Oreopoulos and his group (2), this technique has gained world wide usage. South Africa, like many developing countries has a high incidence of end-stage renal disease (ESRD) but because of lack of resources and economical problems, few patients with ESRD can be treated by dialysis or renal transplantation. CAPD affords a relatively simple and inexpensive form of therapy for these patients. At the present time about 200 patients are on CAPD in South Africa. Natal, the smallest of four provinces in South Africa, has a population of about five million, the majority being blacks. The minority groups include whites, asiatics and coloureds. There is only one chronic dialysis centre in Natal; situated in Durban, it serves the entire province including parts of the Transkei. This paper describes a four-year experience with CAPD in this mixed population and discusses problems unique to this situation.

Ceftolozane-tazobactam in an elastomeric infusion device for ambulatory care: an in vitro stability study

Objectives

Published in vitro stability data for ceftolozane-tazobactam supports intermittent short duration infusions. This method of delivery is not feasible for many outpatient antimicrobial therapy services that provide only one or two visits per day. This study aimed to assess time, temperature and concentration-dependent stability of ceftolozane-tazobactam in an elastomeric infusion device for continuous infusion across clinically relevant ranges encountered in outpatient antimicrobial therapy.

Methods

Ceftolozane-tazobactam was prepared to achieve initial concentrations representing total daily doses for 'renal', 'standard' and 'high' dose schedules in elastomeric infusion devices with a volume of 240 mL. Infusion devices incubated at room and body temperature were serially sampled over 48 hours. Refrigerated infusion devices were sampled over 10 days. Concentrations of ceftolozane and tazobactam were separately quantified using a validated ultra-high performance liquid chromatography-photodiode array method.

Results

The greatest loss of ceftolozane occurred at 37°C, however, stability remained above 90% at 24 hours. Tazobactam was more stable than ceftolozane under these conditions. There was minimal loss at 4°C for either component over 7 days.

Conclusions

Ceftolozane-tazobactam is suitable for ambulatory care delivered as a continuous infusion via an elastomeric infusion device.

Atherosclerotic vascular disease is more prevalent among black ESKD patients on long-term CAPD in South Africa

Background

Occurrence of cardiovascular disease (CVD) in the setting of chronic kidney disease (CKD) can be described as a “cruel alliance”, with CVD responsible for about half of all deaths among CKD patients. Chronic kidney disease patients are more likely to die from CVD than progress to end stage kidney disease (ESKD). Dyslipidaemia, a known traditional risk factor for CVD, is highly prevalent among CKD patients and with an even higher frequency among ESKD patients on dialytic therapies. Prolonged exposure of continuous ambulatory peritoneal dialysis (CAPD) patients to high glucose concentrations in CAPD fluid have been associated with increased risk of cardiovascular events. In this study, we investigated the relationship of atherosclerotic vascular disease (AsVD) to clinical and echocardiographic parameters among black South Africans with CKD (stage 3) and ESKD on CAPD and haemodialysis (HD).

Methods

This was a cross-sectional study of 40 adult (18–65 years) non-diabetic CKD patients (kidney disease outcome quality initiative [KDOQI] stage 3), 40 ESKD patients on CAPD, 40 ESKD patients on HD and 41 age and sex-matched healthy controls. An interviewer-administered questionnaire was used to obtain information on participants’ sociodemographic and cardiovascular risk factors. Anthropometric parameters were measured. Serum blood samples were analysed for creatinine, albumin and lipid profile; lipoprotein ratios, Framingham’s risk score and the 10-year risk of developing coronary heart disease (CHD) were calculated. Echocardiography was performed on all patients and carotid intima media thickness (CIMT) was measured in both right and left carotid arteries at 1 cm proximal to the carotid bulb. Spearman’s rank correlation and binary logistic regression were conducted to determine the relationship of AsVD to clinical and echocardiographic parameters.

Results

Atherosclerotic vascular disease was most prevalent among ESKD patients on CAPD (70%, n = 28/40). Chronic kidney disease and HD patients exhibited a similar prevalence (47.5%, n = 19/40), while the prevalence in controls was 17.1% (n = 7/41). Presence of AsVD was associated with significantly older age, higher waist hip ratio (WHR), left ventricular mass index (LVMI) and Framingham’s 10-year risk of developing CHD. Significant differences in clinical and echocardiographic parameters were observed when the study groups were compared. Age and LVH independently predicted AsVD.

Conclusion

Atherosclerotic vascular disease was more prevalent among CAPD patients compared to pre-dialysis CKD and HD patients. Among all lipoprotein ratios assessed, non-HDL-C showed the most consistent significant difference between the groups. Age (> 40 years) and presence of LVH were independent predictors of AsVD.

A UHPLC-MS/MS method for the simultaneous determination of piperacillin and tazobactam in plasma (total and unbound), urine and renal replacement therapy effluent

Piperacillin-tazobactam is a beta-lactam/beta-lactamase combination antibiotic used in patients with moderate to severe infection. Dosing of piperacillin-tazobactam requires an understanding of this patient group to maximise the effectiveness of this antibiotic and limit a further emergence of resistant pathogens. This is the first method that measures piperacillin and tazobactam simultaneously, across this range of clinically-relevant biological matrices. The calibration line was linear across the concentration range of 0.5-500μg/mL for piperacillin and 0.625-62.5μg/mL for tazobactam. All validation testing for matrix effects, precision and accuracy, specificity and stability were within 15%. A calibration equivalence study was performed to investigate the suitability of applying calibration curves prepared in an alternative matrix, with a mean bias of -10.8% identified for the application of a calibration line prepared for tazobactam in plasma only. Bias for all other calibration lines prepared in alternate matrices was within the 5% acceptance criteria. The method was successfully applied to a pharmacokinetic study of a critically ill patient receiving renal replacement therapy, with the results included.

Proteinuria, graft outcomes, and cardiovascular risk among kidney transplant recipients in a South African Public Hospital

Proteinuria is a marker of poor long-term graft survival and an independent risk factor for total and cardiovascular mortality in the transplant population. We investigated the prevalence of proteinuria and its relationship with graft function and cardiovascular risk factors in kidney transplant recipients (KTRs). Adult KTRs at the Charlotte Maxeke Johannesburg Academic Hospital were recruited. Patients' records were reviewed for information on their posttransplant follow-up. Echocardiography and carotid Doppler were performed for the assessment of cardiac status and carotid intima-media thickness (CIMT), respectively. Proteinuria was analyzed both as a categorical and continuous variable. Graft dysfunction was defined as estimated glomerular filtration rate of <60 mL/min/1.73 m 2 based on the modification of diet in renal disease formula. Framingham's risk score was used to categorize patients' cardiovascular risk. Inferential and modeling statistics were applied as appropriate using Statistical Package for Social Sciences, and P ≤0.05 was considered statistically significant. One hundred KTRs including 63% males were recruited. Proteinuria was present in 51%, the mean ± standard deviation 24 h urinary protein excretion per day was 1.67 ± 2.0 g/day with a range of 0.4-9.4 g/day. Graft dysfunction was found in 52% of patients and 36% had high cardiovascular disease (CVD) risk. Proteinuric KTRs had high CVD risk, P = 0.002. Proteinuria was associated with graft dysfunction, increased left ventricular mass index, increased CIMT, and anemia. Proteinuria is prevalent; it is a marker of graft dysfunction and is associated with markers of atherosclerosis.

Obesity and graft dysfunction among kidney transplant recipients: Increased risk for atherosclerosis

Weight gain after kidney transplant is common, and may be related to graft dysfunction and high cardiovascular risk. We investigated the prevalence of obesity and evaluated the relationship between obesity and graft dysfunction in kidney transplant recipients (KTRs). All patients who received kidney transplant at the Charlotte Maxeke Johannesburg Academic Hospital (CMJAH) between January 2005 and December 2009 were recruited. Information on demographics, clinical characteristics and post-transplant care were documented. All patients underwent transthoracic echocardiography and carotid Doppler ultrasound for the assessment of cardiac status and carotid intima-media thickness (cIMT), respectively. Inferential and modelling statistics were applied. One hundred KTRs were recruited, of which 63 were males. The mean age was 42.2 ± 12.42 years with a range of 19-70 years. The mean body mass index and waist circumference of the recipients were 26.4 ± 4.81 kg/m² and 90.73 ± 14.76 cm, respectively. Twenty-nine patients (29%) were obese; of these, 24 (82.8%) had moderate obesity, 4 (13.8%) had severe obesity, and 1 (3.4%) had morbid obesity. Graft dysfunction was present in 52%. Obese patients were older (P < 0.0001), had graft dysfunction (P = 0.03), higher mean arterial blood pressure (P = 0.022), total cholesterol (P = 0.019), triglycerides (P < 0.0001), left ventricular mass index (P = 0.035) and cIMT (P = 0.036). Logistic regression showed obesity to be independently associated with graft dysfunction (P = 0.033). Obesity after kidney transplantation is common and is associated with graft dysfunction and markers of atherosclerosis.

Stability of Antibiotics for Intraperitoneal Administration in Extraneal 7.5% Icodextrin Peritoneal Dialysis Bags (STAB Study)

♦

BACKGROUND AND OBJECTIVES

Patients with peritoneal dialysis (PD)-associated peritonitis may be advised to store PD-bags with pre-mixed antibiotics at home, although there is a paucity of antibiotic stability studies in the commonly used icodextrin solutions. The purpose of this study was to assess the stability of various antibiotics in PD-bags when stored at different temperatures over a 14-day period. ♦

METHODS

7.5% icodextrin PD-bags were dosed with gentamicin 20 mg/L (n = 9), vancomycin 1,000 mg/L (n = 9), cefazolin 500 mg/L (n = 9) and ceftazidime 500 mg/L (n = 9) as for intermittent dosing. Combinations of gentamicin/vancomycin (n = 9), cefazolin/ceftazidime (n = 9), and cefazolin/gentamicin (n = 9) were also tested. Nine drug-free bags were used as controls. Bags were stored in triplicate at 37°C, room-temperature (25°C), and refrigeration (4°C). Antibiotic concentrations were quantified at various time intervals using validated chromatography. Storage duration was considered unstable if the concentration of the antibiotic dropped ≤ 90% of the initial value. ♦

RESULTS

Gentamicin was stable for 14 days at all temperatures. Vancomycin was stable for 4 days at 37°C and for 14 days at both 25°C and 4°C. The gentamicin and vancomycin combination was stable for 4 days at 37°C and for 14 days at 25°C and 4°C. Cefazolin alone was stable for 24 hours at 37°C, 7 days at 25°C, and 14 days at 4°C. Ceftazidime alone was stable for only 6 hours at 37°C, 2 days at 25°C, and 14 days at 4°C. The cefazolin and ceftazidime combination was stable for 24 hours at 37°C, 2 days at 25°C, and 14 days at 4°C. The cefazolin and gentamicin combination was stable for 1 day at 37°C, 4 days at 25°C, and 14 days at 4°C. ♦

CONCLUSIONS

Antibiotics premixed in icodextrin PD-bags have varying stabilities with stability generally least at 37°C and best at 4(o)C, permitting storage for 14 days when refrigerated and prewarming to body temperature prior to administration. Further research confirming the sterility of these antibiotic-containing bags is recommended.

Impact of socio-economic factors on quality of life in patients on continuous ambulatory peritoneal dialysis in an African setting

BACKGROUND

Quality of life (QOL) is an important outcome following the treatment of disease. It is influenced by physical, psychological, social and economic factors. We proposed to determine the effect of some socioeconomic factors on QOL of patients on CAPD.

STUDY DESIGN

A cross sectional study in which all patients on CAPD attending three clinics attached to the University of the Witwatersrand, Johannesburg were recruited excluding those with intercurrent illness. The WHO quality of life instrument, WHOQOL-Bref, was used to measure QOL. The patients were grouped according to marital status, highest level of education attained, income, employment, and QOL domain scores were compared using ANOVA and Student t test.

RESULTS

A total of 140 patients comprising 80 males and 40 females were assessed. The mean age of patients was 41.9 ± 11.5 years, 95%of patients were black, 44.3% married, 69.3% had secondary education, 22% were employed and 51.4% had a monthly income of less than five thousand Rand (500 US dollars). Single patients scored better in the social relationships domain compared to separated patients (p=0.02, CI: 5.6-32.9). The group with secondary education scored low in the psychological domain compared with those with primary education (p=0.02, CI: 1.35-15.8) and those with tertiary education (p=0.02, CI: 1.72-18.07).The highest income group had best scores in all domains except the physical domain. Those in employment had better scores in the physical domain (p=0.04, CI: 0.356-12.549).

CONCLUSION

Income had the most impact on QOL in study participants.

Environmental isotopic and hydrochemical characteristics of groundwater from the Sandspruit Catchment, Berg River Basin, South Africa

The Sandspruit catchment (a tributary of the Berg River) represents a drainage system, whereby saline groundwater with total dissolved solids (TDS) up to 10,870 mg/l, and electrical conductivity (EC) up to 2,140 mS/m has been documented. The catchment belongs to the winter rainfall region with precipitation seldom exceeding 400 mm/yr, as such, groundwater recharge occurs predominantly from May to August. Recharge estimation using the catchment water-balance method, chloride mass balance method, and qualified guesses produced recharge rates between 8 and 70 mm/yr. To understand the origin, occurrence and dynamics of the saline groundwater, a coupled analysis of major ion hydrochemistry and environmental isotopes (δ(18)O, δ(2)H and (3)H) data supported by conventional hydrogeological information has been undertaken. These spatial and multi-temporal hydrochemical and environmental isotope data provided insight into the origin, mechanisms and spatial evolution of the groundwater salinity. These data also illustrate that the saline groundwater within the catchment can be attributed to the combined effects of evaporation, salt dissolution, and groundwater mixing. The salinity of the groundwater tends to vary seasonally and evolves in the direction of groundwater flow. The stable isotope signatures further indicate two possible mechanisms of recharge; namely, (1) a slow diffuse type modern recharge through a relatively low permeability material as explained by heavy isotope signal and (2) a relatively quick recharge prior to evaporation from a distant high altitude source as explained by the relatively depleted isotopic signal and sub-modern to old tritium values.

Living kidney donor transplants over a 16-year period in South Africa: a single center experience

BACKGROUND

Kidney transplantation is the treatment of choice for end-stage renal disease (ESRD). The number of patients on the waiting list is increasing due to an imbalance between organ supply and demand. This has led to an increase in the number of living donor transplants in most parts of the world. The benefits to the recipients must, however, be weighed against the risks to the donors. Long-term follow-up of the donors is therefore imperative to ascertain the risks of living kidney donation.

MATERIALS AND METHODS

We reviewed the records of 571 potential living kidney donors (PLDs) in Johannesburg hospital over a 16-year period between 1990 and 2005.

RESULTS

There were 1030 kidney transplants during this period, with 800 cadaveric and 230 actual living donor (ALD) transplants. There were 571 PLDs; however, 341 (59.7%) withdrew or were withdrawn because of medical and non-medical reasons. Among the 230 ALDs, the mean age of the donors was 35.2 ± 8.3 years; 55% were females; 24% were Blacks. Eighty-five percent were related to the recipients while 15% were unrelated. Mean duration of follow-up was 8.6 ± 6.4 years. The pattern of post-donation follow-up was excellent in 29.7%, adequate in 34% and unacceptable/poor in 36.3%, based on the number of clinic visits post-donation. Hypertension was noted in 24% of the donors during long-term follow-up. Three of the donors also developed significant microalbuminuria.

CONCLUSION

There is a need to encourage living kidney donation, especially amongst the Black populations, and to emphasize the value and significance of post-donation follow-up visits to all potential donors.

Is there a need for early detection programs for chronic kidney disease?

The aims of this paper are to examine whether early detection programs are needed to assist in detecting and managing chronic kidney disease (CKD). It draws on existing material which indicates that CKD and its precursor risk factors or illnesses such as hypertension, diabetes mellitus and HIV infection are very clearly major challenges faced by health systems worldwide. This paper evaluates whether CKD meets the epidemiological criteria to justify early screening. More compelling evidence is becoming available which indicates that the prevalence of CKD is significant in both developing and developed countries and that CKD can be easily detected and treated with only small changes to existing practice and this may be improved through screening programs. A brief evaluation of the challenges of establishing early detection programs is provided, as well as an examination of the capacity which exists for establishing such programs. It concludes that, despite the lack of randomized studies, these programs appear to provide an opportunity to integrate CKD management with common chronic illnesses and, through this approach, provide clinical and cost-effective management of both CKD and cardiovascular disease.

Chronic kidney disease in human immunodeficiency virus infection

The number of people living with human immunodeficiency virus (HIV) worldwide was estimated to be 39.5 million in 2006, 2.6 million more than in 2004. The manifestations of HIV infection in the kidney are multiple and varied, highlighting the complexity of the disease process. There is a wide spectrum of renal disease that occurs in the course of HIV infection. Biopsy studies reveal varying frequencies of histological patterns. HIV-associated nephropathy (HIVAN) is most common. A biopsy study at Chris Baragwanath Hospital in Soweto, South Africa showed that HIVAN was present in 27% and immune complex disease in 21%. Han et al. studied HIV-positive patients in Durban, South Africa and screened for proteinuria, including microalbuminuria. They found persistent proteinuria in 6%; HIVAN in 21/30 (72.4%) and the prevalence of HIVAN in patients with persistent microalbuminuria was 85.7%. Studies in black patients have shown a higher prevalence of both severe glomerular lesions (focal glomerulosclerosis) and nephrotic range proteinuria with renal dysfunction in the presence of normo-hypotension. There have been no prospective randomised controlled studies with any form of therapy for HIVAN to date. Therapy of HIVAN has included corticosteroids, cyclosporine and antiretroviral therapy (ART). ART appears to be a logical choice in the management of HIV-associated renal disease. Regimens containing protease inhibitors have been shown to be associated with significant slowing of the decline in creatinine clearance. Both peritoneal dialysis and haemodialysis are appropriate treatment modalities for HIV-infected patients with end stage renal disease. The choice of dialysis modality between haemodialysis and peritoneal dialysis is not a factor in predicting survival, if patients are stable on ART. Preliminary short-term data in case reports and small cohorts of liver, kidney, and heart transplant recipients suggest that patient survival rates may be similar to those in HIV-uninfected transplant recipients. However, high rates of acute and chronic rejection have been observed among HIV-infected kidney transplant recipients. The Infectious Diseases Society of America (IDSA) published guidelines in 2005, recommending that all individuals be assessed for kidney disease at the time of diagnosis of HIV infection with a screening urinalysis for proteinuria and a calculated estimate of renal function. Therefore any patient with persistent proteinuria, persistent haematuria or glomerular filtration rate < 60 mL/min per 1.73 m(2) should be referred to an institution where a specialist can evaluate this patient for further investigations. An integrated plan to reduce the progression to kidney failure together with lifestyle measures, focusing also on high risk groups with effective management at all levels of chronic kidney disease remains essential.

A cross-sectional study of HIV-seropositive patients with varying degrees of proteinuria in South Africa

Human immunodeficiency virus (HIV)-associated nephropathy (HIVAN) is the most common finding on renal biopsy in HIV-infected black patients and is also the commonest cause of end-stage renal disease in these patients. Early detection of HIVAN may be beneficial in evaluating early treatment. This study examined the pattern of renal diseases in HIV-infected South Africans and also attempted to diagnose HIVAN at an early stage. In this single-center cross-sectional study, 615 HIV-infected patients were screened for proteinuria. Thirty patients with varying degrees of proteinuria underwent renal biopsy. Patients with diabetes mellitus, uncontrolled hypertension, known causes of chronic kidney disease, and serum creatinine above 250 mumol/l were excluded. Patients in this study were not on antiretroviral therapy. HIVAN was found in 25 (83%) patients. Six of them (24%) had microalbuminuria. Altogether, seven patients with persistent microalbuminuria were biopsied and six (86%) showed HIVAN. Other biopsy findings included membranoproliferative nephropathy in two (7%) and interstitial nephritis in three (10%). Four patients with HIVAN had associated membranous nephropathy. HIVAN is the commonest biopsy finding among our study patients with HIV infection who present with varying degrees of proteinuria. Microalbuminuria is a manifestation of HIVAN in our study patients. Therefore, microalbuminuria may be an early marker of HIVAN, and screening for its presence may be beneficial. Renal biopsy may be considered in seropositive patients who present with persistent microalbuminuria, especially with low CD4 counts irrespective of good renal function. This will allow diagnosis and treatment of HIVAN at an early stage and may prevent further disease progression.

The pathogenesis of membranoproliferative glomerulonephritis in KwaZulu-Natal, South Africa is unrelated to hepatitis C virus infection

Idiopathic membranoproliferative glomerulonephritis (MPGN) is a well-defined clinicopathological entity with a poor prognosis, with 50% of patients progressing to end stage renal disease (ESRD) within 10 years. It was reported in about 36% of adult Black patients with nephrotic syndrome in our center previously [Seedat et al. 1988]. Hepatitis C virus (HCV) infection has been shown to be associated with cryoglobulinemic as well as non-cryoglobulinemic (or idiopathic glomerulonephritis). The aim of this study was to determine whether an association exists between HCV infection and idiopathic MPGN in a population with a relatively high prevalence of MPGN. We studied adult patients referred with glomerular disease over a two-year period, 104 patients had primary glomerulonephritis. All 23 (22%) patients with idiopathic MPGN were enrolled, as well as 32 age-matched patients presenting with other primary glomerular diseases. We examined serum from all 55 patients for evidence of HCV antibodies and HCV RNA. None of the 55 patients showed evidence of HCV infection. Chronic renal failure was present in 82.6% of the patients with idiopathic MPGN and it was advanced in 52,2%, who either were dialysis-requiring at presentation or progressed to ESRD soon thereafter; 30.4% had moderate chronic renal failure, while only 17.4% had normal renal function. HCV infection is not associated with idiopathic MPGN in our patients. Idiopathic MPGN remains an idiopathic disease, possibly with a poor prognosis in our population.

Endothelins: vasoactive modulators of renal function in health and disease

Vasoactive autocoids with directly opposing actions on the renal vasculature, glomerular function, and in salt and water homeostasis have been demonstrated in the kidney. In the renal cortex, endothelin (ET)-1 and angiotensin-II cause vasoconstriction, decreasing renal blood flow, and glomerular filtration rate, whereas bradykinin and atrial natriuretic peptide cause vasodilation and increase glomerular capillary permeability. ET-1 causes vasoconstriction of the afferent and efferent arteries and outer medullary descending vasa recta, thereby decreasing vasa recta and papillary blood flow, while bradykinin has the opposite effect. ET-1 stimulates cell proliferation, increasing the expression of several genes, including collagenase, prostaglandin endoperoxidase synthase, and platelet-derived growth factor. ET-1 promotes natriuresis via the ET-B receptor, causing down-regulation of the epithelial Na(+) channel in the renal tubule. Thus, ETs affect three major aspects of renal physiology: vascular and mesangial tone, Na(+) and water excretion, and cell proliferation and matrix formation.

Kallikrein and kinin receptor expression in inflammation and cancer

The kallikrein family of serine proteases has been investigated in many inflammatory disorders as molecular mapping, gene characterisation and cloning of kinin receptor genes have unfolded experimentally. In the molecular events of the inflammatory response the kallikrein cascade plays a significant role, since it is considered to initiate and maintain systemic inflammatory responses and immune-modulated disorders. A primary event is the chemotactic attraction of neutrophils which deliver the kallikrein-kinin cascade to sites of cellular injury and carcinogenic transformation of cells. The present study establishes the casual involvement of the kallikrein cascade in infection, inflammatory joint disease, acute transplant rejection, renal glomerular diseases, angiogenesis and carcinoma. We provide strong evidence for new or enhanced expression of kinin B1 receptors in inflammation, and additionally the induction of kallikrein genes in angiogenesis and carcinoma. The results provide insights into possible roles of kallikrein inhibitors and kinin receptor antagonists.

GB virus C/hepatitis G virus infection in KwaZulu Natal, South Africa

Sera from 70 patients on maintenance haemodialysis, 98 patients with chronic liver disease, and 232 volunteer blood donors in the province of KwaZulu Natal, South Africa, were screened for GB virus/hepatitis G virus (GBV-C/HGV) RNA and anti-E2 by reverse transcription-polymerase chain reaction (RT-PCR) and by an enzyme-linked immunosorbent assay (ELISA), respectively. GBV-C/HGV RNA was detected in 17/70 (24.3%) haemodialysis patients, 12/98 (12.2%) patients with chronic liver disease, and 44/232 (18.9%) blood donors (Africans [29/76; 38.2%]; Asians [2/52; 3.8%]; Whites [11/49; 22.4%], and "Coloureds" [persons of mixed origin; 2/55; 3.6%]). Overall (anti-E2 and/or RNA) 43.9% (43/98) of patients with chronic liver disease, 47.1% (33/70) of haemodialysis patients, and 31.9% (74/232) of blood donors (Africans [44/76; 5.9%]; Asians [5/52; 9.6%]; Whites [15/49; 30.6%], and Coloureds [9/54; 16.6%]) were exposed to GBV-C/HGV infection. There was a significant difference in the prevalence of GBV-C/HGV infection (RNA and/or anti-E2) between African blood donors and the other racial groups (P < .001), and between blood donors and haemodialysis patients (P = .02) and patients with chronic liver disease (P = .04). Anti-E2 antibodies and GBV-C/HGV RNA were almost mutually exclusive. GBV-C/HGV-infected haemodialysis patients received more transfusions (P = .03) than noninfected patients. There was no significant difference in liver biochemistry between GBV-C/HGV-infected and noninfected patients and between blood donors in each of the four racial groups. The high prevalence of GBV-C/HGV infection in blood donors and chronic liver disease patients, and the lack of elevated liver enzymes and clinical hepatitis in blood donors and haemodialysis patients, suggest that GBV-C/HGV may not be associated with liver disease.

Endothelin-1 and endothelin receptor status in kidney transplants undergoing acute rejection

Endothelin-1 (ET-1) is a potent vasoconstrictor with vasopressor and mitogenic effects. Blood samples were collected from 21 renal transplant patients undergoing acute rejection at the time of diagnostic kidney biopsy: there were 20 men and one woman, mean age 35.6 years. All patients were on triple immunosuppressive therapy with cyclosporine A, azathioprine and methylprednisolone. Twenty living kidney donors pre-uninephrectomy (11 men and nine women, mean age 34 years) served as controls. Control kidney was obtained from fresh autopsy material and normal kidney tissue from nephrectomies for malignancy. Mean plasma ET-1 was significantly increased at 1.56 +/- 0.2 pg ml(-1) during acute rejection compared to 0.74 +/- 0.06 pg ml(-1) in donors (p = 0.0009 unpaired t-test). ET(A) receptor immunolabelling was visualised in distal tubules and collecting ducts with minimal labelling in the glomeruli and blood vessels of control kidney tissue ET(A) receptor labelling was similar in kidney biopsies with acute rejection. ET(B) receptor immunolabelling was significantly increased in glomeruli (p = 0.002) and decreased in distal tubules (p = 0.004) in kidneys with acute rejection compared to control kidney tissue. While these findings may account for the oedema and hypertension observed during acute rejection, the exact significance needs to be studied further.

Tissue kallikrein and kinins in renal disease

The renal kallikrein-kinin system is involved in sodium and water homeostasis, blood pressure regulation and inflammation. Tissue kallikrein and kinin levels were measured in the urine of patients with renal disease and in the urine of living related kidney donors prior to uninephrectomy who served as controls. Tissue kallikrein and kinin B1 and B2 receptors were immunolocalised by confocal microscopy in renal biopsy material from patients with renal disease and controls (fresh autopsy material and normal kidney tissue from nephrectomies for malignancy). Urinary tissue kallikrein excretion was significantly decreased in patients with mild renal disease (16.6 +/- 6.7 ng tissue kallikrein (TK)/ng protein; p < 0.05) and more markedly so (1.8 +/- 0.7 ng TK/microg protein; p < 0.01) in patients with severe renal failure requiring dialysis compared to normal controls (78.9 +/- 31.7 ng TK/microg protein). Basal kinin values were unchanged in patients with renal disease (14 +/- 0.8 ng/ml) compared to controls (13.3 +/- 0.56 ng/ml). In control kidney tissue kallikrein was immunolocalised in the distal connecting tubules and collecting ducts whereas decreased immunolabelling was observed with renal disease. Kinin B2 receptor labelling was present in the entire nephron in the normal control kidney but was reduced with renal disease. While kinin B1 receptor immunolabelling was not observed in the control kidneys, labelling of distal tubules and collecting ducts was noted in renal disease, suggesting an upregulation of B1 receptors in renal parenchymal disease.

Tissue kallikrein in transplant kidney

Literature survey, thus far, has shown a decrease in the excretion of urinary tissue kallikrein (TK) in transplant patients with a further reduction of the enzyme during episodes of acute rejection. The study aims were to compare, at cellular and subcellular levels, the localisation of tissue kallikrein in biopsies of the transplant kidney to autopsy derived normal renal tissue. Renal biopsies from eighteen transplant patients with deteriorating renal function were obtained. Immunolabelling for tissue kallikrein, using a polyclonal goat anti-TK, antibody raised against recombinant TK, was performed following routine enzymatic, immunofluorescence and electron microscopic techniques. In normal kidney tissue, TK was immunolocalised in the distal connecting tubules and collecting ducts. By comparison the renal transplant tissue showed a reduction in the intensity of label, but maintained the sites of localisation. In the sections examined by electron microscopy, although TK was confined mainly at the luminal side of the cell, some label was noted along the basolateral membranes. In the transplant kidneys, there was a reduction in the overall number of gold particles counted, which correlated with the decreased intensity observed on immunocytochemistry. In addition, there was a shift to a basolateral orientation of the immunolabel. Acute rejection is characterised by oedema, tubulitis and vasculitis. Destruction of the tubule cells and leakage of TK into the interstitial tissue space and the resultant effect of the formed kinins on renal capillary vasculature could explain the observed renal parenchymal oedema and transplant rejection.