Barriers and motivation for presumptive tuberculosis case referral: qualitative analysis among operators of community medicine outlets in Ghana.

BACKGROUND: Community medicine outlets (CMOs) are the first point of call for individuals presenting with cough in Ghana. Although operators of CMOs comprising pharmacists and over-the-counter (OTC) medicine sellers largely support the public-private mix strategy which seeks to engage pharmacies in tuberculosis (TB) case detection, a significant proportion is not involved in TB referral services. The study explores the barriers to and motivation for presumptive TB case referral among CMO operators. METHODS: We used open- and close-ended questions nested in a telephone survey which assessed factors associated with presumptive TB case referral among CMO operators (n = 465). We interviewed participants using computer assisted telephone interviews and analysed the qualitative data using adjusted Mayring's structured qualitative content analysis. RESULTS: Based on participants' own experiences, non-referral was attributed to negative attitudes of presumed cases (48.2%) and inability to meet the financial demands of referred presumed cases (26.3%). Regarding their perception of barriers to TB referral for their professional colleagues, an assumed lack of TB training (44.5%) and an assumed negative attitude of operators (43.6%) were mentioned. From close-ended questions, most chosen barriers to referral were: the assumption of not having seen a presumptive TB case yet (31.8%), lack of TB training (22.2%) and no monetary motivation for operators (10.5%). Most operators (81.6%) view TB referral services as their social responsibility and feel self-motivated to refer cases in order to control the spread of TB in their communities. Of 152 further comments extracted as recommendations to improve referral, 101 (66.4%) of respondents would only refer with the availability of support systems in the form of TB training and making TB diagnostic testing more accessible. CONCLUSION: Operators of CMOs are predominantly self-motivated to refer presumptive TB cases. Barriers to referral might be mitigated by providing more training to operators and specific financial support such as reimbursement of travel costs to presumptive cases.

["I cannot kiss my wife"- An Analysis of Daily Experiences of MRSA-carriers]. / "Meine Frau kann ich nicht küssen" ­ Eine Analyse des Erlebens von MRSA-TrägerInnen.

Objectives: There are no data available on the quality of care after discharge from hospital and only limited data are available on the psychosocial effects of being an MRSA carrier within the German health system. Methods: Patients who tested positive for MRSA in the previous year were invited to take part in focus groups. Results: 2 focus groups with a total of 9 MRSA-carriers were conducted. The level of knowledge about MRSA differed between participants. In some cases, lack of information led to uncertainty and inappropriate measures to counteract MRSA. Some participants restricted their social contacts, especially to children, in order to prevent transmission. Patients experienced stigmatization in the health care system more often in inpatient care than in the outpatient sector. Only in a few cases both eradication therapy and swabs for control purposes were carried out. Conclusions: Information about the appropriate treatment and management of MRSA should be made available to patients more easily; in particular, patients need to be informed that MRSA is no threat to healthy individuals. Despite the desire of MRSA-carriers to become MRSA negative, treatment and control of MRSA seem to have low priority in the ambulant health care sector in Germany.

[Tuberculosis and Tobacco Smoking]. / Tuberkulose und Rauchen.

Worldwide there are annually about 9.6 million new cases and 1.5 million deaths due to tuberculosis (TB). Smoking is an independent risk factor causing approximately a twofold increase not only in active Tb disease but also in latent TB infection and mortality. In a mathematical model it is estimated that smoking would produce until 2050 an excess of 18 million tuberculosis cases from TB which would challenge the TB elimination goal of the WHO. Smoking cessation methods during and after TB treatment, which at present are insufficiently included into TB programmes, are urgently needed.

Recommendations of the German Central Committee against Tuberculosis (DZK) and the German Respiratory Society (DGP) for the Diagnosis and Treatment of Non-tuberculous Mycobacterioses.

Non-tuberculous mycobacterioses comprise a group of diseases caused by mycobacteria which do not belong to the Mycobacterium (M.) tuberculosis-complex and are not ascribed to M. leprae. These mycobacteria are characterized by a broad variety as to environmental distribution and adaptation. Some of the species may cause specific diseases, especially in patients with underlying immunosuppressive diseases, chronic pulmonary diseases or genetic predisposition, respectively. Worldwide, a rising prevalence and significance of non-tuberculous mycobacterioses is recognized. The present recommendations summarise current aspects of epidemiology, pathogenesis, clinical aspects, diagnostics - especially microbiological methods including susceptibility testing -, and specific treatment for the most relevant species. Diagnosis and treatment of non-tuberculous mycobacterioses during childhood and in HIV-infected individuals are described in separate chapters.

Test-retest reliability of an infectious disease questionnaire and evaluation of self-assessed vulnerability to infections : findings of Pretest 2 of the German National Cohort.

INTRODUCTION/OBJECTIVES: Large scale population-based studies focusing on infectious diseases are scarce. This may be explained by methodological obstacles concerning ascertainment of data on infectious diseases requiring, e.g. collection of data on relatively short-termed symptoms and/or collection of biosamples for pathogen identification during a narrow time window. In the German National Cohort (GNC), a novel self-administered questionnaire will be used in addition to biosampling to collect data on selected infectious diseases and symptoms. The aim of this study was to evaluate in Pretest 2 of the GNC newly added items on self-assessed vulnerability to several infectious diseases and to assess test-retest reliability of the questionnaire. METHODS: The study was conducted in two study centres (Hamburg and Hanover) during Pretest 2 of the GNC. A self-administered paper questionnaire was applied. In Hamburg, participants were asked to fill in the questionnaire during their regular visit at the study centre. For test-retest reliability, participants in Hanover filled in the same questionnaire at home twice. To evaluate agreement, item-related percentage agreement and kappa (κ) were calculated. In addition, we computed Bennet's S and Krippendorf's alpha (α). Items on self-assessed vulnerability to infections were evaluated by comparing them with the corresponding self-reported frequency of infections. An explanatory factor analysis was applied to construct the scores of self-reported infection frequency and self-assessed vulnerability to infections. RESULTS: The evaluation of the internal consistency of the five-item instrument of self-assessed vulnerability to infections resulted in a Cronbach's α of 0.78. The factor analysis yielded evidence of one factor. The factor was divided into three groups (lowest quintile classified as "less prone to infections" compared to peers; second, middle and fourth quintiles classified as "similarly prone to infections" and highest quintile classified as "more prone to infections"). Participants classified as "less prone to infections" reported fewer infections than participants classified as "more prone to infections". Spearman's correlation of the two scores (self-reported infection frequency and self-assessed vulnerability to infection) was 0.50 (p < 0.0001). For quantifying reliability, 88 participants with a median time of 8 days between filling in both questionnaires could be included in the analysis; for items sensitive to disease occurrence between both questionnaires only participants with no relevant disease in this time interval were included (n = 75). The weighted κ ranged between 0.65 and 0.87 for the items on infectious disease frequency in the last 12 months, for items on symptom frequency in the past 12 months between 0.77 and 0.90, and for items on vulnerability compared to peers between 0.68 and 0.76. CONCLUSION: A five-item instrument on self-assessed vulnerability to infections seems to be promising, but requires further evaluation. Overall, the questionnaire on self-reported infectious diseases used in Pretest 2 of the GNC is a moderately reliable instrument and, thus, can be applied in future studies on infectious diseases.

Collection of vaccination data in the German National Cohort : Findings of a feasibility study in three study centers.

BACKGROUND: Data about the vaccination status of participants are required in epidemiological cohort studies whenever infection or immunity is considered as potential exposure or outcome. Within Pretest 2 of the German National Cohort (GNC) we therefore investigated the acceptance and feasibility of extracting vaccination status from vaccination certificates provided by the participants of the study. METHODS: This study was conducted in three study centers (Bremen, n = 73; Hamburg, n = 200; Hannover, n = 193). In order to test if an additional reminder would prevent participants from forgetting their vaccination certificates at home persons willing to participate in Pretest 2 were randomly assigned to one of three invitation groups (IG). About one third of the participants received either no further reminder (IG1), a reminder card together with the appointment letter (IG2) or a separate reminder card 4 days before the appointment (IG3). At the study center, vaccination data were scanned or copied and entered into a database using a unique identification number. Participants were also asked to fill in a short questionnaire to assess the completeness of the provided vaccination data. Additionally, in one of the three participating study centers, general practitioners (GP) were asked to provide vaccination data from their records following respective participants' consent. Finally, we compared the influenza data from the vaccination certificates with the influenza data obtained from participants in Pretest 2 by use of a self-administered questionnaire (ID-Screen). RESULTS: Due to different starting dates of the study the intended reminder procedure was implemented only in Hamburg and Hannover. In Hamburg, significantly more vaccination certificates were submitted by the group which received the reminder card separately 4 days before the examination (IG3) compared to IG1 and IG2 (p = 0.04). In Hannover, in contrast, most vaccination certificates were brought by those who received the reminder card together with the appointment letter. Overall, the use of a reminder card had a positive but not significant effect as 89 % (185/209) of participants who received the reminder card submitted vaccination data versus 81 % (84/104) of participants who did not receive any reminder card (p = 0.06). Of all Pretest 2 participants in Hannover, 62 % (120/193) gave written consent for data collection by the GPs. In total, 114 practices were contacted of which 49 (43 %) sent vaccination data. All in all, 360 vaccination certificates with 5065 documented vaccinations were entered into a database, of which 4830 (95 %) were valid for analysis covering a period from 1946 to 2012. The comparison of influenza vaccination data from vaccination certificates to the remembered data from a self-completed questionnaire showed an agreement of data in 46 % (84/184) of cases (Kappa = 0.48). Influenza vaccinations were underreported in 4 % (7/170) of self-completed questionnaires. CONCLUSION: The reliable documentation of vaccinations within the context of the GNC proved to be feasible and thus recommendable at a large scale within the GNC as participants showed high willingness and compliance in providing available vaccination documents. An additional validation by means of documents provided by physicians seems to be possible for more than a quarter of participants. In order to maximize the likelyhood of participants' of bringing their vaccination certificates it would be sufficient to send a reminder card together with the appointment letter.

[Recommendations for diagnosis and treatment of nontuberculous mycobacterioses of the German Central Committee against tuberculosis and the German Respiratory Society]. / Empfehlungen zur Diagnostik und Therapie nichttuberkulöser Mykobakteriosen des Deutschen Zentralkomitees zur Bekämpfung der Tuberkulose (DZK) und der Deutschen Gesellschaft für Pneumologie und Beatmungsmedizin (DGP).

Nontuberculous mycobacterioses comprise a group of diseases caused by mycobacteria which do not belong to the Mycobacterium (M.) tuberculosis complex and are not ascribed to M. leprae. These mycobacteria are characterized by a broad variety as to environmental distribution and adaptation. Some of the species may cause specific diseases, especially in patients with underlying immunosuppressive diseases, chronic pulmonary diseases or genetic predisposition, respectively. Worldwide a rising prevalence and significance of nontuberculous mycobacterioses can be recognized. The present recommendations summarise actual aspects of epidemiology, pathogenesis, clinical aspects, diagnostics - especially microbiological methods including susceptibility testing -, and specific treatment for the most relevant species. Diagnosis and treatment of nontuberculous mycobacterioses during childhood and in HIV-infected individuals are described in separate chapters.

[Tuberculosis infection control - recommendations of the DZK]. / Infektionsprävention bei Tuberkulose - Empfehlungen des DZK.

The epidemiological situation of tuberculosis (TB) in Germany has improved considerably during the past few years. However, those in unprotected contact with infectious tuberculosis patients frequently and/or over longer periods of time and/or intensively continue to have a higher risk for TB infection. Rapid diagnosis, prompt initiation of effective treatment, and adequate infection control measures are of particular importance to prevent infection. The present recommendations depict the essentials of infection control as well as specific measures in the hospital (isolation, criteria for its duration and technical requirements, types of respiratory protection, disinfection measures, waste disposal). The specific requirements for outpatients (medical practice), at home, for ambulance services, and in congregate settings, including prisons, are also addressed. Compared with the previous recommendations the pattern of respiratory protection measures has been simplified. As a rule, hospital staff and those visiting infectious tuberculosis patients are advised to wear respiratory protection that satisfies the criteria of FFP2-masks (DIN EN 149), while patients should wear mouth-nose protectors (surgical masks) in the presence of others and outside the isolation room. A detailed depiction of criteria for isolation and its duration in smear positive and only culturally confirmed pulmonary tuberculosis has been added.

[International Standards of Tuberculosis Care (ISTC)--comments from the German point of view]. / International Standards of Tuberculosis Care (ISTC)--Kommentierung aus deutscher Sicht.

The "International Standards for Tuberculosis Care" (ISTC) were developed by the World Health Organisation (WHO) and others to provide internationally agreed and, if possible, evidence-based standards for tuberculosis care including the care by private providers who are not part of national tuberculosis programmes or health-care systems. Hence, the ISTC primarily address resource-restrained countries with high tuberculosis prevalence. In this article, the German translation of the 21 standards from 2009 is presented - addressing diagnostic and therapeutic standards, co-infection (especially with HIV) and public-health issues. The accompanying comments show how these standards have to be modified for Germany due to the medical resources available here and country-specific characteristics respectively.

[Recommendations for therapy, chemoprevention and chemoprophylaxis of tuberculosis in adults and children. German Central Committee against Tuberculosis (DZK), German Respiratory Society (DGP)]. / Empfehlungen zur Therapie, Chemoprävention und Chemoprophylaxe der Tuberkulose im Erwachsenen- und Kindesalter. Deutsches Zentralkomitee zur Bekämpfung der Tuberkulose (DZK), Deutsche Gesellschaft für Pneumologie und Beatmungsmedizin (DGP).

Several new international recommendations have been published since the German Central Committee against Tuberculosis (DZK) published its recommendations for drug treatment of tuberculosis (TB) in 2001 and for chemoprevention of latent tuberculosis infection (LTBI) in 2004. These international publications have been integrated in the present new recommendations which describe both the treatment of active TB and preventive treatment, pointing out specific adaptations for Germany. Separate sections deal with the current management of mono-, poly-, and multiresistance or drug intolerance, of TB in children, of different forms of extrapulmonary TB, of LTBI and of special situations such as HIV infection, renal or hepatic insufficiency, infection following BCG instillation in bladder cancer or in case of adverse drug reactions. The following aspects differ from the previous recommendations: A three-drug regimen for the so-called fully susceptible minimal TB is no longer recommended in adults. A dosage of 15 mg/kg body weight of ethambutol for adults is regarded as sufficient. Four secondline drugs (supplemented by pyrazinamide, where appropriate) are recommended for multidrug-resistant tuberculosis (MDR-TB). MDR-TB should be treated over a period of at least 20 months, with an injectable drug administered for a minimum of 8 months (initial phase). Ciprofloxacine and ofloxacine are no longer used to treat TB. It is also recommended to offer an HIV test to all TB patients to complement antiretroviral therapy, if necessary, and to adapt the antituberculous therapy accordingly.

[Tuberculosis infection control--recommendations of the DZK]. / Infektionsprävention bei Tuberkulose--Empfehlungen des DZK.

The epidemiological situation of tuberculosis (TB) in Germany has improved considerably during the past few years. However, those in unprotected contact with infectious tuberculosis patients frequently and/or over longer periods of time and/or intensively continue to have a higher risk for TB infection. Rapid diagnosis, prompt initiation of effective treatment, and adequate infection control measures are of particular importance to prevent infection. The present recommendations depict the essentials of infection control as well as specific measures in the hospital (isolation, criteria for its duration and technical requirements, types of respiratory protection, disinfection measures, waste disposal). The specific requirements for outpatients (medical practice), at home, for ambulance services, and in congregate settings, including prisons, are also addressed. Compared with the previous recommendations the pattern of respiratory protection measures has been simplified. As a rule, hospital staff and those visiting infectious tuberculosis patients are advised to wear respiratory protection that satisfies the criteria of FFP2-masks (DIN EN 149), while patients should wear mouth-nose protectors (surgical masks) in the presence of others and outside the isolation room. A detailed depiction of criteria for isolation and its duration in smear positive and only culturally confirmed pulmonary tuberculosis has been added.

[New recommendations for contact tracing in tuberculosis]. / Neue Empfehlungen für die Umgebungsuntersuchungen bei Tuberkulose*1.

In 2007, the German Central Committee against Tuberculosis (DZK) published recommendations for contact tracing that introduced the new interferon gamma release assays (IGRAs). Meanwhile, substantial progress has been made in documenting the utility of IGRAs. Because IGRAs are usually superior to the tuberculin skin test (TST) in detecting latent TB infection (LTBI) with respect to sensitivity and specificity in adult contact populations that are at least partially BCG vaccinated, it is now recommended that instead of two-step testing only IGRAs be used.[nl]As the literature does not yet provide sufficient data on the accuracy of IGRAs in children younger than 5 years, the TST remains the method of choice in that age group. To date, also, no clear body of data exists to substantiate better performance for IGRAs than for the TST in older children, thus in this age group using of either test is recommended. The new recommendations also underscore the importance of a diligent preselection of close contacts in order to achieve a high probability that positive test results represent recent infection and to thus increase the benefit of chemopreventive treatment for those identified as requiring it. In a third point of update, it is noted that re-testing of contacts individuals found positive for LTBI may produce a considerable number of false-negative results and should thus be avoided in case of documented exposure.

[New recommendations for contact tracing in tuberculosis. German Central Committee against Tuberculosis]. / Neue Empfehlungen für die Umgebungsuntersuchungen bei Tuberkulose. Deutsches Zentralkomitee zur Bekämpfung der Tuberkulose.

In 2007, the German Central Committee against Tuberculosis (DZK) published recommendations for contact tracing that introduced the new interferon gamma release assays (IGRAs). Meanwhile, substantial progress has been made in documenting the utility of IGRAs. Because IGRAs are usually superior to the tuberculin skin test (TST) in detecting latent TB infection (LTBI) with respect to sensitivity and specificity in adult contact populations that are at least partially BCG vaccinated, it is now recommended that instead of two-step testing only IGRAs be used.[nl]As the literature does not yet provide sufficient data on the accuracy of IGRAs in children younger than 5 years, the TST remains the method of choice in that age group. To date, also, no clear body of data exists to substantiate better performance for IGRAs than for the TST in older children, thus in this age group using of either test is recommended. The new recommendations also underscore the importance of a diligent preselection of close contacts in order to achieve a high probability that positive test results represent recent infection and to thus increase the benefit of chemopreventive treatment for those identified as requiring it. In a third point of update, it is noted that re-testing of contacts individuals found positive for LTBI may produce a considerable number of false-negative results and should thus be avoided in case of documented exposure.

Referral of presumptive TB among operators of community medicine outlets.

BACKGROUND: Case detection is an important part of TB control programmes. In 2007, the TB programme in Ghana join the WHO´s public-private partnership with community medicine outlet operators to increase referral of persons with presumptive TB for laboratory investigation. Information on factors likely to influence referral is scarce in Ghana. We assessed these factors among pharmacists and over-the-counter (OTC) medicine sellers.METHODS: In 2019-2020, we conducted computer-assisted telephone interviews among community pharmacists and OTC medicine sellers in the Eastern Region of Ghana. We used a structured questionnaire and collected data on respondents´ sociodemographics and professional characteristics. We used logistic regression to investigate characteristics associated with self-reported referral of presumptive TB cases.RESULTS: Of all respondents who completed the interviews, 68.7% (321/467) reported having ever referred a presumptive TB case and 72.1% (336/466) had received specific training. Associated factors of presumptive TB referral were having received specific training (OR 2.7, 95% CI 1.5-4.9); performing both dispensing and managerial functions (OR 2.8, 95% CI 1.4-5.5); operating from OTC shop (OR 6.2, 95% CI 1.6-23.4) and the availability of a TB laboratory within walking distance (OR 3.3, 95% CI 1.2-9.5).CONCLUSION: Interviewees largely support TB referral. However, a significant proportion does not follow the strategy closely. We recommend more specific TB training courses.

[Berlin Declaration on Tuberculosis: High Level Follow-Up of High Priority Countries for TB Control in the WHO-EURO Region 'Double Trouble or Double Success? Bringing Together Diseases and Programs' - a symposium report]. / Berlin Declaration on Tuberculosis: High Level Follow-Up of High Priority Countries for TB Control in the WHO-EURO Region 'Double Trouble or Double Success? Bringing Together Diseases and Programs' - ein Symposiumsbericht.

The global tuberculosis (TB) situation has deteriorated dramatically since the beginning of the 1990s. In 2007, the WHO identified 18 countries of the WHO European Region as 'high priority countries' and introduced a plan for these countries to improve the situation. To further promote solutions a WHO European Ministerial Forum 'All against Tuberculosis' took place in Berlin in 2007 and resulted in the 'Berlin Declaration' which was commonly endorsed. In October 2009 a meeting was organized by the German Ministry of Health under the title "Berlin Declaration on Tuberculosis: High Level Follow-Up of High Priority Countries for TB Control in the WHO-EURO Region 'Double Trouble or Double Success? Bringing together Diseases and Programs'". This article summarizes the symposium. Besides reporting on the recent epidemiological situation of the WHO-EURO Region (with partly dramatically developments) presentations on psychosocial issues, the role of the EU and the 'Global Fund to Fight AIDS, Tuberculosis and Malaria', the importance of new tools for the fight against tuberculosis and the need for further political commitment were given.

Respiratory chain inhibition induces tolerance to focal cerebral ischemia.

The authors show that the inhibitor of the succinate dehydrogenase, 3-nitroproprionic acid (3-NPA), which in high doses and with chronic administration is a neurotoxin, can induce profound tolerance to focal cerebral ischemia in the rat when administered in a single dose (20 mg/kg) 3 days before ischemia. Infarcts were approximately 70% and 35% smaller in the 3-NPA preconditioned groups of permanent and transient focal cerebral ischemia, respectively. This regimen of 3-NPA preconditioning neither induced necrosis, apoptosis, or any other histologically detectable damage to the brain, nor did it affect behavior of the animals. 3-NPA led to an immediate (1-hour) and long-lasting (3-day) decrease in succinate dehydrogenase activity (30% reduction) throughout the brain, whereas only a short metabolic impairment occurred (ATP decrease of 35% within 30 minutes, recovery within 2 hours). The authors found that 3-NPA induces a burst of reactive oxygen species and the free radical scavenger dimethylthiourea, when administered shortly before the 3-NPA stimulus, completely blocked preconditioning. Inhibition of protein synthesis with cycloheximide given at the time of 3-NPA administration completely inhibited preconditioning. The authors were unsuccessful in showing upregulation of mRNA for the manganese superoxide dismutase, and did not detect increased activities of the copper-zinc and manganese superoxide dismutases, prototypical oxygen free radicals scavenging enzymes, after 3-NPA preconditioning. The authors conclude that it is possible to pharmacologically precondition the brain against focal cerebral ischemia, a strategy that may in principal have clinical relevance. The data show the relevance of protein synthesis for tolerance, and suggests that oxygen free radicals may be critical signals in preconditioning.

Effect of exercise on balance, strength and reaction time in older people.

Twenty subjects enrolled to take part in an exercise programme (mean age = 62.5 years) and 20 control subjects (mean age = 65.5 years) underwent assessments of strength, reaction time, neuro-muscular control and body sway. The exercisers participated in one hour exercise sessions comprising a cardiorespiratory (walking) component and a gentle exercise component twice weekly for 20 weeks. All subjects were then re-tested for the same measures after the completion of the programme. The exercisers showed improved quadriceps strength, reaction time and reduced body sway when compared with the control group; the exercise group showing continued improvement throughout the programme in tests of body sway. The findings suggest that exercise can improve physical function in older people.

Physical activity program for older persons: effect on balance, strength, neuromuscular control, and reaction time.

Regular exercise has been recommended to improve balance, strength, and coordination in older persons. In this study, 44 persons, aged 50 to 75 years (mean 62.4 yrs) underwent assessments of quadriceps strength, reaction time, neuromuscular control, and body sway on two occasions before beginning a 10-week exercise program. The subjects were retested for the same measures at the end of the program. The mean number of classes attended for the 40 subjects who were retested was 16.2 (range 11 to 19). On completion of the program, the subjects showed improved performance in the tests of quadriceps strength, reaction time, body sway on a firm surface with the eyes closed, and a compliant surface with the eyes open and closed. In contrast, a group of nonexercisers showed no improvements in any of the test measures. These results suggest that exercise may play a role in improving a number of sensorimotor systems that contribute to stability in older persons.

DNA supercoiling determines the activation energy barrier for site specific recombination by Tn21 resolvase.

A kinetic analysis of site specific recombination by Tn21 resolvase has been carried out using DNA substrates of varying superhelicities. The rates for the formation of the recombinant product increased with increasing superhelicity up to a maximum value, after which further increases in superhelicity caused no further increase in rate. The reactions with DNA of reduced superhelicity were extremely slow, yet they eventually led to virtually all of the substrate being converted to product. Hence, the level of DNA superhelicity must determine the activation energy barrier for at least one of the steps within the reaction pathway that can be rate-limiting. In the presence (but not in the absence) of Mg2+ ions, the DNA was fully saturated with resolvase whenever the protein was in stoichiometric excess over resolvase binding sites on the DNA. Thus the process affected by DNA supercoiling cannot be coupled to the binding of resolvase. Instead, the step whose rate is determined by supercoiling seems to be located within the reaction pathway after the synapse. However, these reactions may involve two forms of the synaptic complex that are converted to the recombinant product at different rates.