Therapy of community-acquired acute bacterial meningitis: the clock is running

Prevalence, Antibiogram, and Associated Factors of Bacteria Isolated From Presumptive Meningitis Patients at Debre Markos Comprehensive Specialized Hospital, Northwest Ethiopia

OBJECTIVE

Bacterial meningitis (BM) is a public health threat with considerable mortality and morbidity worldwide; particularly in the meningitis belt of Africa where Ethiopia is located. The study aims to assess the prevalence, antibiogram, and associated factors of bacteria isolated from presumptive meningitis patients at Debre Markos Comprehensive Specialized Hospital (DMCSH), Northwest Ethiopia.

METHODS

We conducted a cross-sectional study between March 1, 2021, and May 30, 2021. Socio-demographic and clinical data were collected using structured questionnaires. Cerebrospinal fluid (CSF) was collected aseptically, and gram stain, culture, and biochemical tests were performed to identify bacterial isolates. An antimicrobial susceptibility test was conducted using the disc diffusion method on Mueller-Hinton agar (MHA). Data were entered into EpiData version 3.1 (Epidata Association, Denmark) and exported to SPSS version 23 software (IBM Corp., Armonk, NY) for analysis. P values ≤ 0.05 at 95% CI were considered statistically significant.

RESULTS

CSF samples from 152 study participants were analyzed and half (50%, 76/152) of them were males. Bacteria were isolated from 17 individuals with an overall prevalence rate of 11.2% (95% CI= 5.9-16.4). The predominant bacterial isolates were Staphylococcus aureus (S. aureus) and Klebsiella pneumonia (K. pneumoniae) each accounting for 29.4% (5/17). About 41% (7/17) of the isolated bacteria were found to be multi-drug resistant (MDR) with the predominance of gram-negative bacteria (6/7). Bacteria prevalence was significantly higher in individuals with stiff neck [adjusted odds ratio (AOR), 95% CI, 47.529 (3.2-10.92), P=0.023] and tonsillectomy [AOR, 95% CI, 137.015 (6.25-12.34), P=0.02].

CONCLUSION

S. aureus and K. pneumoniae were the leading isolates among presumptive meningitis patients. The alarming presence of a high rate of MDR isolates mandates the need to implement the antibiotic stewardship program in the study setting.

Antimicrobial sensitivity profile and bacterial isolates among suspected pyogenic meningitis patients attending at Hawassa University Hospital: Cross-sectional study

Background

Bacterial meningitis is a serious inflammation of the meninges. Antimicrobial therapy on early cerebrospinal fluid (CSF) examination has an important role in diagnosis. The disease is still challenging in developing countries because of poor (diagnostic set-up, socioeconomic conditions, management), and misuse of antimicrobial therapy results in emerging antimicrobial-resistant strains. Therefore, this hospital based cross sectional study was aimed to assess the antimicrobial sensitivity profile and bacterial isolates among patients suspected of pyogenic meningitis at Hawassa University Hospital from February 2017 to 2018.

Results

A total of 394 patients suspected as meningitis were included. Of these 210 (53.3%) were males and 184 (46.7%) were females. The carriage rate of bacterial pathogens was 27(6.9%). The common clinical presentations were fever 330 (83.8%), headache 205 (52.0%) and neck stiffness 179(45.4%) followed by altered mental status 125(31.7%). Neck stiffness P = 0.001 (AOR = 1.18, 95% CI 1.06–6.53), Hx of seizure P = 0.043, (AOR = 1.39, 95% CI 1.15–5.99), Nuchal rigidity P = 0.001* (AOR = 1.26, 95% CI 1.06–4.48) were significantly associated with culture positivity.

The pathogens isolated in this study were N. meningitidis the most frequent isolate 12(44.4%) followed by S. pneumoniae 5 (18.5%), E. coli 4(14.8%), H. influenza 3(13.6%), S. aureus 2(11.1%) and K. pneumoniae 1(3.7%). S. pneumoniae was (100%) resistance to penicillin, (80%) amoxicillin, and (20%) Cefotaxime. S. aureus was (100%) resistant to penicillin, amoxicillin, and ciprofloxacin. N. meningitidis was (100%) resistant to penicillin, (66.7%) Ceftriaxone and (41.7%) chloramphenicol. In this study a single isolate was also resistant to a different antibiotic.

Conclusion

The prevention of bacterial meningitis needs serious attention since the isolated bacteria showed single and multiple antimicrobial susceptibility patterns and the variable nature of isolated etiological agents makes it reasonable to provide continuous future updates on local resistance of common antibiotics and optimize the most frequent bacteria associated with meningitis in the hospital. Therefore; further, survey study with a better design of antimicrobial susceptibility at large scale to control the spread of antibiotic-resistant bacteria and the change in the causative organism of bacterial meningitis in the study area and at a national level is required.

Outcome of patients with acute bacterial meningitis in a teaching hospital in Ethiopia: A prospective study

BACKGROUND

The mortality and neurologic sequelae associated with acute bacterial meningitis (ABM) remain high despite advances in medical care. The main aim of this study was to evaluate short-term outcome in patients treated as bacterial meningitis at a teaching hospital in Ethiopia to identify factors that could be focused on to improve outcome in this setting.

METHODS

A hospital based longitudinal study was conducted at Jimma University Hospital in southwest Ethiopia from March 1, 2013 to December 31, 2015. Participants of this study were patients of age 18 years and older who were treated as confirmed or possible cases of ABM. Patients were followed throughout their hospital stay for change in their clinical course and predefined end points. A multivariable analysis was done to identify factors associated with unfavorable outcomes.

RESULT

90 patients admitted with diagnosis of acute bacterial meningitis were included in the study; cerebrospinal fluid was analysed for 85 (94.4%) of them. Causative bacteria were isolated in 26 (28.9%) patients only; most of these isolates (84.6%) were either Streptococcus pneumoniae or Neisseria meningitidis. Patients managed as cases of ABM at the hospital suffered from a high rate of unfavorable outcome (36.7%) and an overall mortality rate of 22.2%. Impaired level of consciousness (AOR = 0.766, 95% CI = 0.589-0.995), dexamethasone therapy (AOR = 4.676, 95% CI = 1.12-19.50) and fever persisting after two days of admission (AOR = 24.226, 95% CI = 5.24-111.96) were found to be independently associated with unfavorable outcome.

CONCLUSION

Outcome in patients treated for ABM at the hospital was found to be poor. Impaired mentation, treatment with adjunctive dexamethasone and persistent fever were found to be associated with poor outcome. Thus, development of clinical guidelines for treatment of ABM that suit the local context is essential to improve patient management and outcome.

Adjunctive dexamethasone therapy in unconfirmed bacterial meningitis in resource limited settings: is it a risk worth taking?

BACKGROUND

Bacterial meningitis is associated with significant morbidity and mortality despite advances in medical care. The main objective of this study was to assess the association of adjunctive dexamethasone treatment with discharge outcome of patients treated as bacterial meningitis in low income setting.

METHODS

A retrospective study was conducted at four teaching hospitals across Ethiopia. Patients of age 14 years and older treated as cases of bacterial meningitis between January 1, 2011 and April 30, 2015 were included in this study. Information regarding sociodemographic data, clinical presentations, laboratory data, treatments given and status at hospital discharge were retrieved from patients' medical records using a structured questionnaire. Predefined outcome variables at discharge were analysed using descriptive statistics. Multivariable logistic regression was used to identify factors independently associated with poor outcome.

RESULTS

A total of 425 patients treated with the presumptive clinical diagnosis of bacterial meningitis were included in this study (lumbar puncture done in 56 %; only 19 % had CSF findings compatible with bacterial meningitis, and only 3 % had proven etiology). The overall in hospital mortality rate was 20.2 %. Impaired consciousness, aspiration pneumonia, and cranial nerve palsy at admission were independently associated with increased mortality. Adjuvant dexamethasone, which was used in 50.4 % of patients, was associated with increased in-hospital mortality (AOR = 3.38; 95 % CI 1.87-6.12, p < 0.001) and low Glasgow outcome scale (GOS) at discharge (AOR = 4.46 (95 % CI 1.98-10.08). This association between dexamethasone and unfavorable outcome was found to be more pronounced in suspected but unproven cases and in those without CSF alterations compatible with bacterial meningitis.

CONCLUSION

Most patients treated for suspected bacterial meningitis did not receive proper diagnostic workup. Adjuvant dexamethasone use in clinically suspected but unproven cases of bacterial meningitis was associated with an increased mortality and poor discharge GOS. These findings show that there are potential deleterious effects in unconfirmed cases in this setting. Physicians practising under such circumstances should thus abide with the current recommendation and defer the use of adjuvant corticosteroid in suspected cases of bacterial meningitis.

Challenges of bacterial meningitis case management in low income settings: an experience from Ethiopia

OBJECTIVE

To investigate the current diagnostic and therapeutic strategies used in the care of patients with suspected bacterial meningitis at teaching hospitals in Ethiopia.

METHODS

This was a hospital-based retrospective study conducted at four teaching hospitals in different regions of Ethiopia. Participants were patients aged 14 years and older treated for suspected bacterial meningitis. Presenting complaints, diagnostic strategies used and treatments given were obtained from clinical records.

RESULT

A total of 425 patients were included in the study; 52.7% were men and 83.8% were younger than 50 years. Fever, headache, neck stiffness and impaired consciousness were the most common clinical presentations; 55.5% underwent lumbar puncture. Overall, only 96 (22.6%) patients had cerebrospinal fluid abnormalities compatible with bacterial meningitis. A causative bacterium was identified in only 14 cases. Ceftriaxone was used as the empiric treatment of choice, either alone or in combination with other antibiotics; 17.6% of patients were also given vancomycin. Adjunctive dexamethasone was given to 50.4%.

CONCLUSION

Most patients treated as bacterial meningitis did not receive a proper diagnostic workup. The choice of antibiotic was not tailored to the specific clinical condition of the patient. Such an approach may result in poor treatment outcomes and lead to antibiotic resistance. Management of patients with suspected bacterial meningitis should be supported by analysis of cerebrospinal fluid, and treatment should be tailored to local evidence and current evidence-based recommendations.

Evolution of antimicrobial resistance and serotype distribution of Streptococcus pneumoniae isolated from children with invasive and noninvasive pneumococcal diseases in Algeria from 2005 to 2012

Pneumococcal infections are a major cause of morbidity and mortality in developing countries. The introduction of pneumococcal conjugate vaccines (PCVs) has dramatically reduced the incidence of pneumococcal diseases. PCVs are not currently being used in Algeria. We conducted a prospective study from 2005 to 2012 in Algeria to determine antimicrobial drug resistance and serotype distribution of Streptococcus pneumoniae from children with pneumococcal disease. Among 270 isolated strains from children, 97 (36%) were invasive disease; of these, 48% were not susceptible to penicillin and 53% not susceptible to erythromycin. A high rate of antimicrobial nonsusceptibility was observed in strains isolated from children with meningitis. The serotype distribution from pneumococci isolated from children with invasive infections was (by order of prevalence): 14, 1, 19F, 19A, 6B, 5, 3, 6A and 23F. Multidrug resistance was observed in serotypes 14, 19F, 19A and 6B. The vaccine coverage of serotypes isolated from children aged <5 years was 55.3% for PCV7, 71.1% for PCV10 and 86.8% for PCV13. Our results highlight the burden of pneumococcal disease in Algeria and the increasing S. pneumoniae antibiotic resistance. The current pneumococcal vaccines cover a high percentage of the circulating strains. Therefore, vaccination would reduce the incidence of pneumococcal disease in Algeria.

Metabolische Störungen

Im folgenden Kapitel werden die verschiedenen metabolischen Störungen betrachtet. Zunächst wird auf die allgemeinen und spezifischen neurologischen Komplikationen bei Organtransplantation eingegangen. Dann geht es um die metabolischen Enzephalopathien: Störungen der Gehirntätigkeit bei angeborenen und erworbenen Stoffwechselerkrankungen im engeren Sinn, Elektrolytstörungen, Hypovitaminosen, zerebrale Folgen einzelner Organdysfunktionen, zerebrale Hypoxien, Endotheliopathien und Mitochondropathien. Anschließend werden das Alkoholdelir und die Wernicke-Enzephalopathie erörtert. Bei zahlreichen akuten Erkrankungen von Gehirn, Rückenmark und peripherem Nervensystem treten typische Störungen vegetativer Systeme auf, deren Erkennung und Therapie insbesondere bei Intensivpatienten eine vitale Bedeutung haben kann: die autonomen Störungen. Bei der zentralen pontinen Myelinolyse kommt es zu einer akuten, vorwiegend fokal-symmetrischen Demyelinisierung im Hirnparenchym. Auch Basalganglienerkrankungen können intensivmedizinisch relevant werden. Und schließlich wird die akute Stressreaktion betrachtet, die aufgrund der vielfältigen metabolischen und endokrinen Veränderungen bei kritischen Erkrankungen entsteht. Gerade das RCVS als neuere Krankheitsentität und wichtige Differenzialdiagnose zur Vaskulitis des ZNS verdient einen eigenen Platz, in diesem Unterkapitel werden ebenfalls verwandte Syndrome wie die hypertensive Enzephalopathie und das PRES abgehandelt.

Infektionen

In diesem Kapitel werden zunächst die für die Neurointensivmedizin wesentlichen bakteriellen Infektionen (Meningitis, spinale und Hirnabszesse, Spondylodiszitis, septisch-embolische Herdenzephalitis) abgehandelt, die trotz gezielt eingesetzter Antibiotika und neurochirurgischer Therapieoptionen noch mit einer erheblichen Morbidität und Mortalität behaftet sind. Besonderheiten wie neurovaskuläre Komplikationen, die Tuberkulose des Nervensystems, Neuroborreliose, Neurosyphilis und opportunistische Infektionen bei Immunsuppressionszuständen finden hierbei besondere Berücksichtigung. Der zweite Teil dieses Kapitels behandelt akute und chronische Virusinfektionen des ZNS sowie in einem gesonderten Abschnitt die HIVInfektion und HIV-assoziierte Krankheitsbilder sowie Parasitosen und Pilzinfektionen, die in Industrieländern seit Einführung der HAART bei HIV zwar eher seltener, aber mit zunehmender Globalisierung auch in unseren Breiten immer noch anzutreffen sind.

Leukocyte attraction by CCL20 and its receptor CCR6 in humans and mice with pneumococcal meningitis

We previously identified CCL20 as an early chemokine in the cerebrospinal fluid (CSF) of patients with pneumococcal meningitis but its functional relevance was unknown. Here we studied the role of CCL20 and its receptor CCR6 in pneumococcal meningitis. In a prospective nationwide study, CCL20 levels were significantly elevated in the CSF of patients with pneumococcal meningitis and correlated with CSF leukocyte counts. CCR6-deficient mice with pneumococcal meningitis and WT mice with pneumococcal meningitis treated with anti-CCL20 antibodies both had reduced CSF white blood cell counts. The reduction in CSF pleocytosis was also accompanied by an increase in brain bacterial titers. Additional in vitro experiments showed direct chemoattractant activity of CCL20 for granulocytes. In summary, our results identify the CCL20-CCR6 axis as an essential component of the innate immune defense against pneumococcal meningitis, controlling granulocyte recruitment.

Neuroinfectious diseases at a European neurological tertiary care center: one-third of patients require treatment in the neurological intensive care unit

BACKGROUND AND PURPOSE

Studies on the impact of infectious diseases affecting the nervous system are sparse.

METHODS

All patients with neuroinfectious diseases (NIDs) who were treated at our Department of Neurology from 2005 until 2009 were retrospectively analyzed.

RESULTS

Patients with NIDs required treatment at the intensive care unit in 34.8%. The mortality rate of patients with NIDs was significantly higher than that of other inpatients with neurological diseases (5.1% vs. 3.0%, respectively, P = 0.018).

CONCLUSION

In summary, this study shows that patients with NIDs are severely ill and mortality is high.

Bacterial meningitis: current therapy and possible future treatment options

Despite targeted therapy, case-fatality rates and neurologic sequelae of bacterial meningitis remain unacceptably high. The poor outcome is mainly due to secondary systemic and intracranial complications. These complications seem to be both a consequence of the inflammatory response to the invading pathogen and release of bacterial components by the pathogen itself. Therefore, within the last decades, research has focused on the mechanism underlying immune regulation and the inhibition of bacterial lysis in order to identify new targets for adjuvant therapy. The scope of this article is to give an overview on current treatment strategies of bacterial meningitis, to summarize new insights on the pathophysiology of bacterial meningitis, and to give an outlook on new treatment strategies derived from experimental models.

Infektionen

Trotz Weiterentwicklung moderner Antibiotika in den letzten Jahren sind die Letalitätszahlen der bakteriellen (eitrigen) Meningitis weiterhin hoch; Überlebende haben häufig neurologische Residuen. Die ungünstigen klinischen Verläufe der bakteriellen Meningitis sind meist Folge intrakranieller Komplikationen, wie z. B. eines generalisierten Hirnödems, einer zerebrovaskulären arteriellen oder venösen Beteiligung oder eines Hydrozephalus.

β-Lactam resistance, serotype distribution, and genotypes of meningitis-causing Streptococcus pneumoniae, Rio de Janeiro, Brazil

BACKGROUND

Here, we report a laboratory-based study of Streptococcus pneumoniae recovered from patients with meningitis in Rio de Janeiro State, Brazil.

METHODS

The aim of this study was to determine the evolution of β-lactam resistance, antimicrobial susceptibility pattern, serotypes, and genetic diversity of S. pneumoniae, isolated from meningitis patients between 2000 and 2008.

RESULTS

A total of 264 S. pneumoniae recovered from patients between 2000 and 2008 were included. Susceptibility testing (E-test) of S. pneumoniae showed resistance to penicillin, ceftriaxone, oxacillin, cotrimoxazole, tetracycline, ofloxacin, erythromycin, chloramphenicol, and rifampicin. Penicillin resistance (PEN-R, minimal inhibitory concentration [MIC] ≥ 0.12 μg/mL) increased from 8% of isolates in 2000-2002, to 12% in 2003-2005, and to 20% in 2006-2008. Ceftriaxone resistance (MIC ≥ 1.0 μg/mL) was detected among some PEN-R isolates (13%) from 2004 onward. Within the PEN-R isolates, serotypes that are included in 10-valent pneumococcal conjugate vaccine predominated (90%), and resistance was detected mostly in isolates of serotypes 14 (61%), 23F (16%), 6B (10%), and 19F (3%). Multilocus sequence typing showed that 52% of the PEN-R isolates, and 89% of those with MICs ≥ 0.5 μg/mL, were sequence type (ST)-156 or single-locus variants of this ST (ST-557 or ST-4388); all of these isolates were serotype 14 and were assigned to the Spain-3 clone.

CONCLUSIONS

β-lactam resistance increased recently among cerebrospinal fluid isolates and was mainly due to the surge of the ST-4388, a previously undescribed gki single-locus variants of ST-156. Regional surveillance is shown to be essential to provide optimal antimicrobial therapy, monitor highly successful clones, and formulate adequate vaccination strategy.

Arterial cerebrovascular complications in 94 adults with acute bacterial meningitis

Introduction

Intracranial vascular complications are an important complication of acute bacterial meningitis. Ischemic stroke in meningitis is reported as a result of vasculitis, vasospasm, endocarditis or intraarterial thrombosis. The aim of the study was to identify the value of measuring cerebral blood flow velocity (CBFv) on transracranial doppler (TCD) in the identification of patients at risk for meningitis-associated stroke.

Methods

We retrospectively studied patients with acute bacterial meningitis who were treated in our university hospital from 2000 to 2009. Data were analyzed with the main focus on the incidence of an increase of CBFv on TCD, defined as peak systolic values above 150 cm/s, and the development of stroke.

Results

In total, 114 patients with acute bacterial meningitis were treated, 94 of them received routine TCD studies during their hospital stay. 41/94 patients had elevated CBFv values. This increase was associated with an increased risk of stroke (odds ratio (95% confidence intervall) = 9.15 (1.96-42.67); p < 0.001) and unfavorable outcome (Glasgow Outcome Score < 4; odds ratio (95% confidence intervall) = 2.93 (1.23-6.98); p = 0.018). 11/32 (34.4%) patients with an increase of CBFv who received nimodipine and 2/9 (22.2%) patients with an increase of CBFv who did not receive nimodipine developed stroke (p = 0.69).

Conclusions

In summary, TCD was found to be a valuable bedside test to detect arterial alterations in patients with bacterial meningitis. These patients have an increased risk of stroke.

Single nucleotide polymorphisms in TLR9 are highly associated with susceptibility to bacterial meningitis in children

BACKGROUND

Bacterial meningitis (BM) is a severe infection mainly caused by Streptococcus pneumoniae and Neisseria meningitidis (NM). However, genetically determined susceptibility to develop severe infections by these microorganisms is variable between individuals. Toll-like receptor 9 (TLR9) recognizes bacterial DNA leading to intracellular inflammatory signaling. Single nucleotide polymorphisms (SNPs) within the TLR9 gene are associated with susceptibility to several diseases, no such association with meningitis has been described.

METHODS

We studied the role of TLR9 SNPs in host defense against BM. Two TLR9 SNPs and 4 TLR9 haplotypes were determined in 472 survivors of BM and compared to 392 healthy controls.

RESULTS

Carriage of the TLR9+2848-A mutant was significantly decreased in meningococcal meningitis (MM) patients compared with controls (p: .0098, odds ratio [OR]: .6, 95% confidence interval [CI]: .4-.9). TLR9 haplotype I was associated with an increased susceptibility to MM (p: .0237, OR 1.3, 95% CI: 1.0-1.5). In silico analysis shows a very strong immunoinhibitory potential for DNA of NM upon recognition by TLR9 (CpG index of -106.8).

CONCLUSIONS

We report an association of TLR9 SNPs with susceptibility to BM, specifically MM indicating a protective effect for the TLR9+2848-A allele. We hypothesize that the TLR9+2848-A mutant results in an up-regulation of TLR9 induced immune response compensating the strong inhibitory potential of NM CpG DNA.

Headaches attributable to infectious diseases

Headache is the most common symptom that humans experience. While the vast majority of headaches are due to benign primary headache disorders, a small but important minority of headaches are due to secondary causes. Whereas significant emphasis is placed on educating physicians regarding prompt recognition of subarachnoid hemorrhage and headaches secondary to brain tumors, attention toward headaches secondary to infectious causes is often neglected. Unfortunately, a missed or delayed diagnosis of a headache secondary to meningitis, encephalitis, brain abscess, subdural empyema, or other infectious etiologies can lead to dire consequences for both the patient and physician. Accordingly, this article provides an overview of headaches attributed to systemic and intracranial infectious causes.

Meningitis in neonates: bench to bedside

The clinical outcome of central nervous system infection is determined by the characteristics of the pathogen and the brain's response to the invading bacteria. How infection leads to brain injury remains unresolved. An impediment to progress is the complexity of pathophysiologic processes. Some of the mechanisms involved have been identified in experimental models, providing insights into the molecular basis of brain injury and regeneration, and hinting at targets for therapy. Adjuvant therapies have been proposed. Interventions that protect the brain are evaluated for their potential to preserve neuro-integrative functions in long-term survivors of bacterial meningitis. This article summarizes current studies evaluating pharmacologic interventions in experimental models of bacterial meningitis and discusses how the knowledge gathered could translate into more effective therapies.

Early severe inflammatory responses to uropathogenic E. coli predispose to chronic and recurrent urinary tract infection

Chronic infections are an increasing problem due to the aging population and the increase in antibiotic resistant organisms. Therefore, understanding the host-pathogen interactions that result in chronic infection is of great importance. Here, we investigate the molecular basis of chronic bacterial cystitis. We establish that introduction of uropathogenic E. coli (UPEC) into the bladders of C3H mice results in two distinct disease outcomes: resolution of acute infection or development of chronic cystitis lasting months. The incidence of chronic cystitis is both host strain and infectious dose-dependent. Further, development of chronic cystitis is preceded by biomarkers of local and systemic acute inflammation at 24 hours post-infection, including severe pyuria and bladder inflammation with mucosal injury, and a distinct serum cytokine signature consisting of elevated IL-5, IL-6, G-CSF, and the IL-8 analog KC. Mice deficient in TLR4 signaling or lymphocytes lack these innate responses and are resistant, to varying degrees, to developing chronic cystitis. Treatment of C3H mice with the glucocorticoid anti-inflammatory drug dexamethasone prior to UPEC infection also suppresses the development of chronic cystitis. Finally, individuals with a history of chronic cystitis, lasting at least 14 days, are significantly more susceptible to redeveloping severe, chronic cystitis upon bacterial challenge. Thus, we have discovered that the development of chronic cystitis in C3H mice by UPEC is facilitated by severe acute inflammatory responses early in infection, which subsequently are predisposing to recurrent cystitis, an insidious problem in women. Overall, these results have significant implications for our understanding of how early host-pathogen interactions at the mucosal surface determines the fate of disease.