Survey on infectious disease telephone hotlines in primary care: General practitioners' satisfaction and compliance with advice.

OBJECTIVES: Infectious disease (ID) advice is a major part of antimicrobial stewardship programs. The objective of this study was to assess general practitioners' (GPs)' opinions and compliance with advice given by ID hotlines. PATIENTS AND METHODS: This multicenter survey was based on the 7-day assessment of initial advice requested by GPs to a hotline set up by volunteer hospital ID teams to record advice for 3 years. The primary endpoint was the GPs' satisfaction with the advice given by ID specialists. RESULTS: Ten ID teams participated in the study and recorded 4138 requests for advice, of which 1325 requests included a proposal for antibiotic therapy and justified a follow-up call at seven days. Only 398 follow-up calls (30%) were carried out because many GPs were not reachable. GPs were very satisfied with ID hotlines: 58% considered them indispensable and 38% very useful. The recommendations provided by ID specialists were followed by GPs in more than 80% of cases. The two main motivations for GPs to call the hotline were to get quick advice (86%) and to receive help in managing a patient (76%). CONCLUSIONS: The ID telephone consultations and advice systems for GPs are highly appreciated and are effective in terms of following the recommendations.

Impact of therapeutic drug monitoring of antibiotics in the management of infective endocarditis.

Treatment of infective endocarditis (IE) is based on high doses of antibiotics with a prolonged duration. Therapeutic drug monitoring (TDM) allows antibiotic prescription optimization and leads to a personalized medicine, but no study evaluates its interest in the management of IE. We conducted a retrospective, bicentric, descriptive study, from January 2007 to December 2019. We included patients cared for IE, defined according to Duke's criteria, for whom a TDM was requested. Clinical and microbiological data were collected after patients' charts review. We considered a trough or steady-state concentration target of 20 to 50 mg/L. We included 322 IE episodes, corresponding to 306 patients, with 78.6% (253/326) were considered definite according to Duke's criteria. Native valves were involved in 60.5% (185/306) with aortic valve in 46.6% (150/322) and mitral in 36.3% (117/322). Echocardiography was positive in 76.7% (247/322) of cases. After TDM, a dosage modification was performed in 51.5% (166/322) (decrease in 84.3% (140/166)). After initial dosage, 46.3% (82/177) and 92.8% (52/56) were considered overdosed, when amoxicillin and cloxacillin were used, respectively. The length of hospital stay was higher for patient overdosed (25 days versus 20 days (p = 0.04)), and altered creatinine clearance was associated with overdosage (p = 0.01). Our study suggests that the use of current guidelines probably leads to unnecessarily high concentrations in most patients. TDM benefits predominate in patients with altered renal function, but probably limit adverse effects related to overdosing in most patients.

Cerebrospinal fluid lactate concentration and bacterial encephalitis diagnosis.

OBJECTIVES: A French national study on infectious encephalitis enrolled 253 patients in 2007. Fifty-two per cent of patients had a proven etiological diagnosis; 16% had bacterial encephalitis. We aimed to assess the predictive value of CSF lactate concentration to diagnose bacterial encephalitis. PATIENTS AND METHODS: Patients from the 2007 cohort whose CSF lactate concentration was available were included. Clinical and biological features associated with a bacterial etiology were assessed using univariate analysis and multivariate logistic regression. The ROC curve of CSF lactate concentration was used to define the most appropriate cut-off associated with bacterial etiology. RESULTS: Fifty-seven patients (37 men, 20 women) were included. Ten patients had bacterial encephalitis, 20 patients had viral encephalitis. The mean CSF white blood cells (WBC), protein, glucose, and lactate levels were respectively 92 cells/mm3 (range: 0-450), 1.2g/L (range: 0.2-8.2), 3.9mmol/L (range: 0.8-8.8), and 2.8mmol/L (range: 0-9.4). In univariate analysis, CSF protein level (P<0.01), WBC count (P=0.02), and lactate concentration (P<0.01) were significantly associated with bacterial etiology. The only factor independently associated with bacterial etiology in the multivariate analysis was CSF lactate concentration. The area under the ROC curve of CSF lactate for the diagnosis of bacterial encephalitis was 0.86. The cut-off value of 3.4 mmol/L correctly classified 87.8% of patients with 70% sensitivity, 91.5% specificity, 64% positive predictive value, and 93% negative predictive value. CONCLUSION: A high CSF lactate level seems to be a better predictor than WBC or proteins to differentiate bacterial encephalitis from other etiologies.

Prolonged suppressive antibiotic therapy for prosthetic joint infection in the elderly: a national multicentre cohort study.

During prosthetic joint infection (PJI), optimal surgical management with exchange of the device is sometimes impossible, especially in the elderly population. Thus, prolonged suppressive antibiotic therapy (PSAT) is the only option to prevent acute sepsis, but little is known about this strategy. We aimed to describe the characteristics, outcome and tolerance of PSAT in elderly patients with PJI. We performed a national cross-sectional cohort study of patients >75 years old and treated with PSAT for PJI. We evaluated the occurrence of events, which were defined as: (i) local or systemic progression of the infection (failure), (ii) death and (iii) discontinuation or switch of PSAT. A total of 136 patients were included, with a median age of 83 years [interquartile range (IQR) 81-88]. The predominant pathogen involved was Staphylococcus (62.1%) (Staphylococcus aureus in 41.7%). A single antimicrobial drug was prescribed in 96 cases (70.6%). There were 46 (33.8%) patients with an event: 25 (18%) with an adverse drug reaction leading to definitive discontinuation or switch of PSAT, 8 (5.9%) with progression of sepsis and 13 died (9.6%). Among patients under follow-up, the survival rate without an event at 2 years was 61% [95% confidence interval (CI): 51;74]. In the multivariate Cox analysis, patients with higher World Health Organization (WHO) score had an increased risk of an event [hazard ratio (HR) = 1.5, p = 0.014], whereas patients treated with beta-lactams are associated with less risk of events occurring (HR = 0.5, p = 0.048). In our cohort, PSAT could be an effective and safe option for PJI in the elderly.

Is brain angio-MRI useful in infective endocarditis management?

In infective endocarditis (IE), brain magnetic resonance imaging (MRI) is helpful to diagnose clinically silent neurological events. We assessed the usefulness of systematic early brain MRI in IE diagnosis and medico-surgical management. Over a period of 1 year, all patients admitted in one of the three hospitals participating in and fulfilling the Duke criteria for definite or possible IE underwent cerebral MRI within 7 days of IE suspicion. Eight panels of experts analyzed the records a posteriori. For each case, one record with and one record without the MRI results were randomly assigned to two panels, which determined the theoretical diagnosis and treatment. Paired comparisons were performed using a symmetry test. Thirty-seven brain MRIs were performed within a median of 5 days after inclusion. MRI was pathological in 26 patients (70 %), showing 62 % microischemia and 58 % microbleeds. The expert advice did not differ significantly between the two evaluations (with or without the MRI results). The therapeutic strategies determined diverged in five cases (13.5 %). Diagnosis differed in two cases (5.4 %), with an upgrading of diagnosis from possible to definite IE using MRI results. Early brain MRI did not significantly affect the IE diagnosis and medico-surgical treatment plan. These results suggest that systematic use of early brain MRI is irrelevant in IE. Further studies are necessary to define whether MRI is mandatory in IE management within a multidisciplinary approach, with particular attention paid to better timing and the subset of patients in whom this imaging examination could be beneficial.

Is prosthesis retention effective for chronic infections in hip arthroplasties? A systematic literature review.

The success rate of prosthesis removal as the standard approach to manage chronic infection in hip arthroplasties (HA) is 80-90 %. The effectiveness of prosthesis retention, with or without surgical debridement, to treat patients with chronic HA infection (symptom duration of more than 4 weeks) has not been well established, whereas this strategy is sometimes used in clinical practice. This study aimed to explore the cumulative incidence of failure of chronic HA infections treated with prosthesis retention, with or without debridement. A systematic literature review was conducted in accordance with the methods described in the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). Studies concerning patients with chronically infected HA treated with prosthesis retention were included. The primary outcome was the cumulative risk of failure. We searched the MEDLINE, Embase, and Cochrane databases up to April 2014. The database searches provided a total of 1,213 studies for potential inclusion in the review. Six relevant studies were finally identified, corresponding to 29 patients included. Their treatments consisted of prosthesis retention with debridement. This strategy failed for 14 out of these 29 patients after a 1-year follow-up. The failure rate of the prosthesis retention approach associated to debridement for chronic infection in HA is 48.3 % in this review. Debridement and prosthesis retention in association with prolonged antimicrobial treatment may be an advantageous alternative to arthroplasty exchange for frail patients. The difficulty in finding relevant studies illustrates the challenges of interpreting the existing literature for the management of chronic prosthetic joint infection (PJI).

Evaluation of an intervention to improve blood culture practices: a cluster randomised trial.

This study aimed to evaluate an intervention to improve blood culture practices. A cluster randomised trial in two parallel groups was performed at the Grenoble University Hospital, France. In October 2009, the results of a practices audit and the guidelines for the optimal use of blood cultures were disseminated to clinical departments. We compared two types of information dissemination: simple presentation or presentation associated with an infectious diseases (ID) specialist intervention. The principal endpoint was blood culture performance measured by the rate of patients having one positive blood culture and the rate of positive blood cultures. The cases of 130 patients in the "ID" group and 119 patients in the "simple presentation" group were audited during the second audit in April 2010. The rate of patients with one positive blood culture increased in both groups (13.62 % vs 9.89 % for the ID group, p = 0.002, 15.90 % vs 13.47 % for the simple presentation group, p = 0.009). The rate of positive blood cultures improved in both groups (6.68 % vs 5.96 % for the ID group, p = 0.003, 6.52 % vs 6.21 % for the simple presentation group, p = 0.017). The blood culture indication was significantly less often specified in the request form in the simple presentation group, while it remained stable in the ID group (p = 0.04). The rate of positive blood cultures and the rate of patients having one positive blood culture improved in both groups. The ID specialist intervention did not have more of an impact on practices than a simple presentation of audit feedback and guidelines.

Pneumocystis jirovecii (Pj) quantitative PCR to differentiate Pj pneumonia from Pj colonization in immunocompromised patients.

Conventional polymerase chain reaction (PCR) in respiratory samples does not differentiate between Pneumocystis pneumonia (PCP) and Pneumocystis jirovecii (Pj) colonization. We used Pj real-time quantitative PCR (qPCR) with the objective to discriminate PCP from Pj colonization in immunocompromised patients. All positive Pj qPCR [targeting the major surface glycoprotein (MSG) gene] obtained in respiratory samples from immunocompromised patients presenting pneumonia at the Grenoble University Hospital, France, were collected between August 2009 and April 2011. Diagnoses were retrospectively determined by a multidisciplinary group of experts blinded to the Pj qPCR results. Thirty-one bronchoalveolar lavages and four broncho aspirations positive for the Pj qPCR were obtained from 35 immunocompromised patients. Diagnoses of definite, probable, and possible PCP, and pneumonia from another etiology were retrospectively made for 7, 4, 5, and 19 patients, respectively. Copy numbers were significantly higher in the "definite group" (median 465,000 copies/ml) than in the "probable group" (median 38,600 copies/ml), the "possible group" (median 1,032 copies/ml), and the "other diagnosis group" (median 390 copies/ml). With the value of 3,160 copies/ml, the sensitivity and specificity of qPCR for the diagnosis of PCP were 100 % and 70 %, respectively. With the value of 31,600 copies/ml, the sensitivity and specificity were 80 % and 100 %, respectively. The positive predictive value was 100 % for results with more than 31,600 copies/ml and the negative predictive value was 100 % for results with fewer than 3,160 copies/ml. qPCR targeting the MSG gene can be helpful to discriminate PCP from Pj colonization in immunocompromised patients, using two cut-off values, with a gray zone between them.

[Dermatofibrosarcoma protuberans in children]. / Le dermatofibrosarcome chez l'enfant.

Dermatofibrosarcoma protuberans is a malignant and locally invasive tumor. It generally affects young adults. However, in rare but not exceptional cases, children can suffer from this disease. In the literature, there are only few studies on this pathology occurring in children. The main treatment is surgical excision with large margins. We studied in our series 15 cases of dermatofibrosarcoma in children between 1995 and 2008. The data were retrospectively collected. The aim of our study is to underline the best support for this pathology in children. The mean age at the moment of diagnosis was 13 years old. None of our patients underwent surgery for dermatofibrosarcoma removal before. The diagnosis was confirmed by biopsy and immunology by FISH method. In 60% of the cases, the lesion, which is very polymorphic, was on the trunk. In three cases, a skin trauma was noted in the patient's history. Surgical management consisted in tumor's excision with a 3 cm margin laterally associated with the removal of the first unaffected anatomical layer in depth. Reconstruction was adapted to the defect's width, depth and topography. The mean follow-up was 7.8 years. There were no relapses reported in a 3-year period at least. Complications were two scars dehiscences which needed skin graft for repair and a scarring alopecia reconstructed secondarily by a skin expansion protocol. No functional sequelae were reported in our series. As dermatofibrosarcoma in children presents the same clinical aspect and evolution as in adults, we treated it the same way. This diagnosis should not be ignored in children, and should be made early to give the patient the most effective support.

[Treatment of sequelae of burns in children]. / Le traitement des séquelles de brûlure de l'enfant.

Burn sequelae in children are conveyed in the form of retraction, deformity and growth problems together with dyschromia and trophic disorders. All the plastic surgical procedures can be used to correct them: full thickness or split thickness skin grafts, Z plasty and its derivatives (trident plasty, IC flaps), expansion, flaps, artificial skin, and dermabrasion. In most cases, these procedures will be combined. The aim of surgical treatment coordinated with rehabilitation is to restore the function, correct the deformities induced, improve the morphological aspect and permit normal growth. Good knowledge of the paediatric environment is, however, required to cope with the specificities of the child: treat the severe local inflammation, get the family to participate in the projects of rehabilitation, sometimes with the help of social services, maintain normal schooling, accompany the disorders in body schema, and, finally, prolong follow-up until growth is complete, a challenge in these patients who are often very young at the time of the accident.

[Evaluation of urologic activity in ambulatory surgery: a single centre experience]. / Évaluation de la pratique de la chirurgie ambulatoire en urologie: expérience d'un centre.

OBJECTIVE: Ambulatory surgery is an alternative to traditional hospitalisation and an opportunity for savings for the healthcare system. Here, we analyze our experience in outpatient surgery in urology over a year. MATERIAL: A prospective database concerning outpatient activity was established in 2009, gathering age, ASA score, type of intervention, discharge and recovery for each patient. An individual questionnaire was sent retrospectively in February 2010, to collect data about history of outpatient surgery, overall satisfaction, preference for traditional hospitalization and emergency department visits within 48 hours after surgery. RESULTS: In 2009, 465 patients aged of 52±16 years (15-98) underwent urologic surgery on an outpatient basis. Median ASA score was 2 (1-3). Types of intervention were mainly endo-urology (44.5%), surgery for urinary incontinence (32.5%), and circumcision (12.3%). The postoperative hospitalization rate was 4.5%. The questionnaire response rate was 28%. Forty-six percent of the patients had already been supported in ambulatory, overall satisfaction was 3.3 out of 4 (±1.06) and 24% of patients would have preferred a traditional hospitalization. 11% of patients required emergency department care within 48 hours whatever the surgery undergone. CONCLUSION: An important part of urological procedures has been done on an outpatient basis without compromising quality of care and patient satisfaction.

Meningococcal purpura fulminans in children: I. Initial orthopedic management.

BACKGROUND: Purpura fulminans is a rare and extremely severe infection, mostly due to Neisseria meningitidis frequently causing early orthopedic lesions. Few studies have reported on the initial surgical management of acute purpura fulminans. The aim of this study is to look at the predictive factors in orthopedic outcome in light of the initial surgical management in children surviving initial resuscitation. METHODS: Nineteen patients referred to our institution between 1987 and 2005 were taken care of at the very beginning of the purpura fulminans. All cases were retrospectively reviewed so as to collect information on the total skin necrosis, vascular insufficiency, gangrene, and total duration of vasopressive treatment. RESULTS: All patients had multiorgan failure; only one never developed any skin necrosis or ischemia. Eighteen patients lost tissue, leading to 22 skin grafts, including two total skin grafts. There was only one graft failure. Thirteen patients were concerned by an amputation, representing, in total, 54 fingers, 36 toes, two transmetatarsal, and ten transtibial below-knee amputations, with a mean delay of 4 weeks after onset of the disease. Necrosis seems to affect mainly the lower limbs, but there is no predictive factor that impacted on the orthopedic outcome. We did not perform any fasciotomy or compartment pressure measurement to avoid non-perfusion worsening; nonetheless, our outcome in this series is comparable to existing series in the literature. V.A.C.(®) therapy could be promising regarding the management of skin necrosis in this particular context. While suffering from general multiorgan failure, great care should be observed not to miss any additional osseous or articular infection, as some patients also develop local osteitis and osteomyelitis that are often not diagnosed. CONCLUSIONS: We do not advocate very early surgery during the acute phase of purpura fulminans, as it does not change the orthopedic outcome in these children. By performing amputations and skin coverage some time after the acute phase, we obtained similar results to those found in the literature.

Spontaneously chosen crank rate variations in submaximal arm exercise with inexperienced subjects. Effects on cardiorespiratory and efficiency parameters.

The aim of the present study was to compare the physiological responses during arm exercises when the crank rate was chosen spontaneously (TS) or set at +/- 20 % (T-20, T+ 20) of the spontaneously chosen crank rate (SCCR). Eight physical education male students, aged 22 +/- 3.2 years, performed an upper body exercise in which intensities ranged from unload to 80 % of maximal power. No significant difference was observed in oxygen uptake, ventilation, gross and net efficiency values between TS and T+ 20 or T-20. Nevertheless, oxygen uptake and ventilation were significantly (p < 0.05) lower and gross and net efficiencies higher (p < 0.05) during T-20 than T+ 20. No significant difference was noticed for heart rate, delta and work efficiency between TS, T-20 and T+ 20. The hypothesis that SCCR is the most economical one according to the efficiency parameters was not quite verified. However, crank rates lower than SCCR could be interesting because they increase gross efficiency compared to higher crank rates. Moreover, the selection of crank rates depends on power output. Indeed, SCCR increased significantly (p < 0.05) with power output. In the physical reconditioning of injured or handicapped subjects, the latter are very sensitive to the power output, and the crank rate could be another constraint.

Nongenomic actions of estrogens and xenoestrogens by binding at a plasma membrane receptor unrelated to estrogen receptor alpha and estrogen receptor beta.

The molecular mechanism used by environmental chemicals to exert their hormone-like actions is still only partially resolved. Although it generally is accepted that xenoestrogens act at the genomic level by binding to intracellular estrogen receptors, we have shown here that they trigger nongenomic effects in pancreatic beta cells. Both xenoestrogens and the circulating hormone, 17beta-estradiol, bind with high affinity to a common membrane binding site unrelated to the intracellular estrogen receptors ERalpha and ERbeta. This binding site is shared by dopamine, epinephrine, and norepinephrine and has the pharmacological profile of the gammaadrenergic receptor. This study provides an outline of the membrane receptor involved in rapid xenoestrogen actions.

Histopathologic findings in cutaneous cytomegalovirus infection.

When cytomegalovirus (CMV) involves the skin, viral inclusions are typically present within mesenchymal cells, e.g., endothelial cells, fibrocytes, and sometimes within inflammatory cells, e.g., macrophages, in contrast to infection in other organs in which inclusions are usually present within ductal epithelial cells. Two cases of cutaneous CMV are presented, one showing prominent findings within eccrine ductal epithelium and the other revealing mostly endothelial cells affected by CMV. Due to the range of cytologic changes induced by CMV observed in these cases, there seem to be early, fully developed, and late cellular changes brought about by CMV analogous to how herpesvirus (varicella, zoster, simplex) induces different changes depending on its stage of infection.

[Reconstruction of the anterior cruciate ligament: arthrotomy versus arthroscopy]. / Reconstruction du ligament croisé antérieur: arthrotomie versus arthroscopie.

The aim of this study was to compare the results of arthroscopic with open arthrotomy reconstruction of the anterior cruciate ligament, as treatment of chronic anterior laxity. 54 knees (among 63) were evaluated, 33 reconstructions were performed according to Kenneth Jones technique with arthrotomy (from 1990 to may 1993) and 21 were arthroscopically-assisted (from may 1993 to 1996). Meniscectomy was associated respectively in 22 and 7 cases. The average interval between initial injury and surgery was 18 and 18.6 months. Follow-up was one year at least. We evaluated mobility, amyotrophy and quadriceps and hamstrings muscular deficit: static at 1 month and using Cybex isokinetic tests at 2, 3 and 6 months and 1 year. Postoperative residual laxity and Arpege cotation were evaluated at 1 year. Student and Mann Whitney tests were used for statistical evaluation. As complication we noted respectively after arthrotomy and after arthroscopy: 7 (21.2 p. 100) and 4 (19 p. 100) algodystrophy, 1 (3 p. 100) and 1 (4., 7 p. 100) Cyclops syndrome, and 2 (6 p. 100) and 1 (4.7 p. 100) anterior knee pain. Lack of extension and flexion were respectively -5.4 degrees/130 degrees and -1.9 degrees/136 degrees at 3 months (p = 0.04) and -3.5/134 degrees and -1.5 degrees/138 degrees at 6 months (not significative). At 1 month, static hamstrings deficit was 41.3 p. 100 after open arthrotomy and 29.6 p. 100 after arthroscopic assisted (p = 0.05). At 2 months, isokinetic hamstrings deficit was lower after arthroscopic assisted (21.6 p. 100 at 60 degrees; 20.8 p. 100 at 180 degrees) than after open arthrotomy (32.8 p. 100; 32.5 p. 100) (p = 0.039 and 0.008). This difference was found for hamstrings until 3 months. At 6 months and 1 year, no difference was found for Cybex tests. In Arpege score, at 1 year, 73.3 p. 100 were very satisfied or satisfied after open arthrotomy and 77.7 p. 100 after arthroscopy. Global results were excellent or good in 66 p. 100 after open arthrotomy and 83 p. 100 after arthroscopy. Radiological laxity was less than 5 mm in 88 p. 100 after open arthrotomy and 92 p. 100 after arthroscopic assisted. So, after arthroscopically assisted procedure, the number of algodystrophy and anterior knee pain was lower, and until 3 months, range of motion was better and hamstrings deficit was lower. After 6 months, difference about range of motion or muscular deficit were not significative. At 1 year, after arthroscopic procedure, results seemed better with a lower rate of residual laxity and better global results, but the number of medial meniscectomies was lower in this group. In conclusion, the arthroscopic-assisted procedure seems to allow a faster rehabilitation.

Long-term weekly treatment of colorectal metastatic cancer with fluorouracil and leucovorin: results of a multicentric prospective trial of fluorouracil dosage optimization by pharmacokinetic monitoring in 152 patients.

PURPOSE: A relationship between fluorouracil (5-FU) dose and response has been previously shown in advanced colorectal cancer. In a previous study with 5-FU stepwise dose escalation in a weekly regimen, and pharmacokinetic monitoring, we defined a therapeutic range for 5-FU plasma levels: 2,000 to 3,000 microg/L (area under the concentration-time curve at 0 to 8 hours [AUC0-8], 16 to 24 mg x h/L). The current study investigated 5-FU therapeutic intensification with individual dose adjustment in a multicentric phase II prospective trial. PATIENTS AND METHODS: Weekly high-dose 5-FU was administered by 8-hour infusion with 400 mg/m2 leucovorin. The initial dose of 5-FU (1,300 mg/m2) was adapted weekly according to 5-FU plasma levels, to reach the therapeutic range previously determined. RESULTS: A total of 152 patients entered the study from December 1991 to December 1994: 117 patients with measurable metastatic disease and 35 with assessable disease. Toxicity was mainly diarrhea (39%, with 5% grade 3) and hand-foot syndrome (30%, with 2% grade 3). Among 117 patients with measurable disease, 18 had a complete response (CR), 48 a partial response (PR), 35 a minor response (MR) and stable disease (SD), and 16 progressive disease (PD). Median overall survival time was 19 months. The 5-FU therapeutic plasma range was rapidly reached with a variable 5-FU dose in the patient population: mean, 1,803 +/- 386 mg/m2/wk (range, 950 to 3,396). Thirteen patients were immediately in the toxic zone, whereas 51 required a > or = 50% dose increase. CONCLUSION: Individual 5-FU dose adjustment with pharmacokinetic monitoring provided a high survival rate and percentage of responses, with good tolerance.

The active site region of the vitamin K-dependent carboxylase includes both the amino-terminal hydrophobic and carboxy-terminal hydrophilic domains of the protein.

In order to localize the active site of the vitamin K-dependent carboxylase, we developed an affinity probe containing the propeptide and the first two carboxylatable glutamate residues conserved in many native substrates. This probe crosslinked to both the hydrophobic amino-terminal and hydrophilic carboxy-terminal domains of the carboxylase, in contrast with previous work which localized both the catalytic and the propeptide binding site within the amino-terminal hydrophobic domain. Amino acid analysis revealed that the mass of an amino-terminal fragment is seriously underestimated by SDS-PAGE. Reanalysis of the published data in light of this information suggests that a portion of the propeptide binding site resides within the carboxy-terminal hydrophilic domain.