Serum bactericidal test

High Activity of N-Acetylcysteine in Combination with Beta-Lactams against Carbapenem-Resistant Klebsiella pneumoniae and Acinetobacter baumannii

Aim: The aim of the study was to evaluate the in vitro activity of N-acetylcysteine (NAC), alone or in combination with beta-lactams, against carbapenem-resistant Klebsiella pneumoniae (CR-Kp) and Acinetobacter baumannii (CR-Ab). Methods: The antibacterial activity of each compound was tested by broth microdilution and the synergism was evaluated by the checkerboard method. Killing studies of NAC alone and in combination with beta-lactams were performed. Bacterial morphological changes were investigated with scanning electron microscopy (SEM). Results: Overall, 30 strains were included (15 CR-Kp and 15 CR-Ab). The NAC Minimal Inhibitory Concentrations (MIC)50/90 were 5/5 and 2.5/5 mg/mL for CR-Kp and CR-Ab, respectively. For both microorganisms, NAC, in addition to beta-lactams (meropenem for CR-Kp, meropenem and ampicillin/sulbactam for CR-Ab, respectively), was able to enhance their activity. The killing studies showed a rapid and concentration-dependent activity of NAC alone; the addition of NAC to meropenem or ampicillin/sulbactam at subinhibitory concentrations induced a fast and lasting bactericidal activity that persisted over time. The SEM analyses showed evident morphological alterations of the bacterial cells following incubation with NAC, alone and in combination with meropenem. Conclusions: NAC demonstrated a high in vitro activity against CR-Kp and CR-Ab and was able to enhance beta-lactams’ susceptibility in the tested strains. The preliminary data on the SEM analyses confirmed the in vitro results.

Cefiderocol for compassionate use in the treatment of complicated infections caused by extensively and pan-resistant Acinetobacter baumannii

OBJECTIVE

This study presents real-life experience with cefiderocol used on a compassionate basis for treatment of three patients with severe infections caused by extensively/pan-drug resistant (XDR/PDR) Acinetobacter baumannii (Ab).

METHODS

Serum bactericidal activity was determined and considered as a surrogate of cefiderocol susceptibility.

RESULTS

Clinical improvement and microbiological eradication of A. baumannii were observed in all three patients, who were affected by extremely complex conditions either for type of infection, adverse effect or resistance profile of A. baumannii.

CONCLUSION

Cefiderocol for XDR/PDR-Ab infections might be reconsidered, especially in light of the recent disappointing results of the CREDIBLE-CR study.

Dalbavancin and telavancin in the treatment of infective endocarditis: a literature review

Glycopeptides have an established role in the management of infective endocarditis, and feature in current treatment guidelines. Newer lipoglycopeptide agents (dalbavancin, telavancin and oritavancin), which are analogues of glycopeptides with structural modifications giving rise to added novel mechanisms of antimicrobial activity, are approved for the treatment of Gram-positive skin and skin structure infections, and also for nosocomial pneumonia (only telavancin has approval for the latter indication). Recent evidence has also emerged to support their use in the treatment of bone and joint infections. This article reviews the current literature on dalbavancin and telavancin in the treatment of infective endocarditis, a condition for which the role of these agents is yet to be established.

Serum bactericidal titres for monitoring antimicrobial therapy: current status and potential role in the management of multidrug-resistant Gram-negative infections

BACKGROUND

Serum bactericidal titres (SBTs) were widely used in the 1970s and 1980s to monitor antimicrobial therapy but are now seldom recommended. It is the only laboratory test that integrates drug pharmacodynamics, host pharmacokinetics and synergistic or antagonistic interactions of antimicrobial combinations into a single index of antimicrobial activity. We hypothesized that SBTs could play a renewed role in monitoring antibiotic treatment of multidrug-resistant Gram-negative infections. However, the last critical appraisal of the test was published over 30 years ago.

OBJECTIVES

This narrative review provides an updated assessment of the SBT test and its methodological limitations. We performed a diagnostic meta-analysis to estimate the value of SBTs for predicting clinical failure or death during antibiotic treatment.

SOURCES

A comprehensive literature search of PubMed including all English publications was performed in December 2019 using the Medical Subject Headings (MeSH search terms "serum", "bactericidal", "inhibitory", "titre", "monitoring", "anti-infective agents" "antimicrobial therapy" and "therapeutic drug monitoring").

CONTENT

Although standardized methods for performing SBTs were approved in 1999, the test remains labour intensive, and results may not be available until 72 hr. However, the use of non-culture-based endpoints (i.e. spectrophotometric or fluorescent) may shorten test time to 24 hr. Despite considerable heterogeneity in published studies, a meta-analysis of 11 evaluable studies published from 1974 to 2007 indicated a critical SBT result (peak SBT ≤1:8 or trough ≤1:2) is associated with a diagnostic odds ratio for clinical failure during antibiotic treatment of 12.27 (95% confidence interval 5.28-28.54) and a 5.32 (95% 1.32-21.42) odds of death.

IMPLICATIONS

SBTs have prognostic value for identifying patients at high risk for antibiotic treatment failure, but the slow turnaround time of the current test limits its clinical utility. Standardization of a more rapid SBT testing method is needed.

Serum Bactericidal Activity Levels Monitor to Guide Intravenous Dalbavancin Chronic Suppressive Therapy of Inoperable Staphylococcal Prosthetic Valve Endocarditis: A Case Report

Here we describe a case of a methicillin-resistant coagulase-negative staphylococci prosthetic valve endocarditis in a patient considered not eligible for valve replacement due to high perioperative mortality risk and who did not tolerate oral antibiotic treatment. Under these circumstances, intravenous long-term chronic suppressive antibiotic therapy with dalbavancin, scheduling the doses using the serum bactericidal activity titers, proved to be safe and effective.

Comparative serum bactericidal activity of meropenem-based combination regimens against extended-spectrum beta-lactamase and KPC-producing Klebsiella pneumoniae

Combination therapies are frequently used in the treatment of multidrug-resistant Klebsiella pneumoniae infection without consensus regarding which combination is the most effective. We compared bactericidal titres from sera collected from critically ill patients receiving meropenem plus tigecycline (n = 5), meropenem plus colistin (n = 5), or meropenem, colistin and tigecycline (n = 5) against K. pneumoniae isolates that included ESBL-producing (n = 7) and KPC-producing strains (n = 14) with varying sensitivity patterns to colistin and tigecycline. Meropenem concentrations (C_min) were measured in all samples by LC-MS/MS, and indexed to respective pathogen MICs to explore differences in patterns of bactericidal activity for two versus three drug combination regimens. All combination regimens achieved higher SBTs against ESBL (median reciprocal titre 128, IQR 32-256) versus KPC (4, IQR 2-32) strains. Sera from patients treated with meropenem-colistin yielded higher median SBTs (256, IQR 64-512) than either meropenem-tigecycline (32, IQR 8-256; P < 0.001). The addition of tigecycline was associated with a lower probability of achieving a reciprocal SBT above 8 when meropenem concentrations were below the MIC (P = 0.04). Although the clinical significance is unknown, sera from patients receiving tigecycline-based combination regimens produce lower serum bactericidal titres against ESBL or KPC-producing K. pneumoniae. SBTs may represent a useful complimentary endpoint for comparing pharmacodynamics of combinations regimens for MDR Enterobacteriaceae.

Choosing optimal antimicrobial therapies

Life-threatening infectious disease emergencies require immediate, aggressive parenteral administration of antimicrobial agents to ensure high bactericidal concentrations of drug at the site of infection. Usually initial treatment is empiric until culture results and antimicrobial sensitivities are reported. This approach necessitates the use of broad-spectrum bactericidal agents that will eradicate the presumed infecting organism(s), which potentially could be multidrug resistant. For infections potentially attributable to gram-positive bacteria, vancomycin is commonly used because it will be effective for highly resistant strains such as MRSA and multidrug-resistant S pneumoniae. For gram-negative infections, broad-spectrum β-lactams, such as ceftriaxone, piperacillin-tazobactam, and the carbapenems, are commonly chosen. Excellent alternatives include the fluoroquinolone antibiotics. For nosocomial infections whereby P aeruginosa and other highly resistant organisms may be the cause, antipseudomonal β-lactams such as cefepime, ceftazidime, piperacillin-tazobactam, or doripenem may be used as well as the fluoroquinolone, ciprofloxacin. For anaerobic infections, it is usually necessary to add either metronidazole or clindamycin. Once an infection is under control and the culture and sensitivity results are reported, it is important to switch to the most narrow-spectrum agent possible. Taking this action will decrease the potential for adverse drug effects and the risk of development of antibiotic-induced resistance.

Rifampin combination therapy for nonmycobacterial infections

The increasing emergence of antimicrobial-resistant organisms, especially methicillin-resistant Staphylococcus aureus (MRSA), has resulted in the increased use of rifampin combination therapy. The data supporting rifampin combination therapy in nonmycobacterial infections are limited by a lack of significantly controlled clinical studies. Therefore, its current use is based upon in vitro or in vivo data or retrospective case series, all with major limitations. A prominent observation from this review is that rifampin combination therapy appears to have improved treatment outcomes in cases in which there is a low organism burden, such as biofilm infections, but is less effective when effective surgery to obtain source control is not performed. The clinical data support rifampin combination therapy for the treatment of prosthetic joint infections due to methicillin-sensitive S. aureus (MSSA) after extensive debridement and for the treatment of prosthetic heart valve infections due to coagulase-negative staphylococci. Importantly, rifampin-vancomycin combination therapy has not shown any benefit over vancomycin monotherapy against MRSA infections either clinically or experimentally. Rifampin combination therapy with daptomycin, fusidic acid, and linezolid needs further exploration for these severe MRSA infections. Lastly, an assessment of the risk-benefits is needed before the addition of rifampin to other antimicrobials is considered to avoid drug interactions or other drug toxicities.

Clindamycin in the treatment of group G beta-haemolytic streptococcal infections

We report a case of severe streptococcal cellulitis in a healthy 47 year old male, where the sole microbial isolate was a beta-haemolytic group G Streptococcus. Treatment failure with high dose penicillin was observed despite in vitro sensitivity. The addition of clindamycin resulted in dramatic clinical improvement. This may indicate an Eagle-type effect (whereby antibiotics exhibit paradoxically reduced bactericidal activities at high drug concentrations), in group G beta-haemolytic infections. Although well documented with group A streptococcal infections, this phenomenon has not been fully recognised with group G beta-haemolytic streptococcal infections. This may have important implications for clinical management.

The Importance of Bactericidal Drugs: Future Directions in Infectious Disease

BACKGROUND

Although a considerable amount of research has gone into the study of the role of bactericidal versus bacteriostatic antimicrobial agents in the treatment of different infectious diseases, there is no accepted standard of practice.

METHODS

A panel of infectious diseases specialists reviewed the available literature to try to define specific recommendations for clinical practice.

RESULTS

In infections of the central nervous system, the rapidity with which the organism is killed may be an important determinant, because of the serious damage that may occur during these clinical situations. The failure of bacteriostatic antibiotics to adequately treat endocarditis is well documented, both in human studies and in animal models.

CONCLUSION

The bulk of the evidence supports the concept that, in treating endocarditis and meningitis, it is important to use antibacterial agents with in vitro bactericidal activity. This conclusion is based on both human and animal data. The data to support bactericidal drugs' superiority to bacteriostatic drugs do not exist for most other clinical situations, and animal models do not support this concept in some situations. Clinicians should be aware that drugs that are bacteriostatic for one organism may in fact be bactericidal for another organism or another strain of the same organism.

Outpatient parenteral antimicrobial therapy (OPAT) for the treatment of osteomyelitis: evaluation of efficacy, tolerance and cost

OBJECTIVES

To evaluate the feasibility, efficacy, and cost of outpatient parenteral antimicrobial therapy (OPAT) in the treatment of osteomyelitis.

SUBJECTS

39 patients with an osteomyelitis requiring parenterally administered antibiotics for more than 4 weeks, and able to receive antibiotics at home.

METHODS

All patients had a totally implanted catheter. Antibiotics were administered by continuous infusion using a portable elastomeric infusion system, which was changed every day by the patient or by the home-care nurse. Laboratory monitoring and surveillance were performed weekly. Clinical efficacy, adverse effects and quality of life were recorded.

RESULTS

The most commonly used antibiotics were vancomycin (51%) and beta-lactam (44%) antibiotics. Thirty patients were available for follow-up for a minimum of 12 months after completion of therapy. Twenty-eight (93%) were considered cured of their infection with a mean of 24 +/- 4 months after completion of antibiotic therapy. Adverse effects among the study patients were rare. The 39 patients in our OPAT programme resulted in a potential saving of US $1 873 885 relative to conventional therapy.

CONCLUSION

OPAT is practicable and effective and may be the best alternative treatment for patients suffering from osteomyelitis requiring intravenous therapy.

Pharmacodynamics of ceftriaxone and cefixime against community-acquired respiratory tract pathogens

Over the last decade or so there has been a growing interest in routes of antimicrobial administration other than by the conventional intravenous route for institutionalized patients and for some outpatients. Both oral (PO) and intramuscular (IM) routes of administration are less costly than giving antimicrobial agents by vein (IV). In addition, fewer complications such as catheter-related sepsis and phlebitis are associated with non-IV routes of administration. Furthermore, a reduced-dosage, reduced-volume IM administration of ceftriaxone may provide a tolerable route of administration and equivalent bactericidal activities compared with higher dose IV ceftriaxone. The purpose of this study was to determine the time that the drug concentration remained in excess of the minimum inhibitory concentration (MIC) (T > MIC) and the duration of bactericidal activities of ceftriaxone one gram administered IV, ceftriaxone 250 mg given IM and cefixime 400 mg given orally against clinical isolates of Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis in adult volunteers. Single doses of each agent were administered and serum concentrations were collected over the standard dosing period of 24 h for all study regimens. Ceftriaxone, regardless of route of administration and dose, resulted in bactericidal activities and T > MIC for 100% of the dosing period for S. pneumoniae, H. influenzae, and M. catarrhalis. Cefixime maintained at least 50% T > MIC and bactericidal activity against both isolates each of H. influenzae and M. catarrhalis. Against both isolates of S. pneumoniae, cefixime achieved T > MIC for at least 50% of the dosing period, but did not maintain bactericidal activity. Reduced dose ceftriaxone given IM seems to be a viable alternative to ceftriaxone IV if the pathogen, susceptibility and infection site are known. Based on T > MIC exceeding 50% of the dosing interval, cefixime would be considered an effective alternative to IV therapy against common respiratory tract pathogens. Clinical studies need to be conducted to confirm these findings.

Conventional and genetic laboratory tests used to guide antimicrobial therapy

Detection of antimicrobial resistance is important so that clinicians can make rational decisions about optimal antimicrobial therapy for their patients. During the past decade, new types of antimicrobial resistance have emerged, some of which present new challenges for the clinical microbiology laboratory. In most cases, conventional culture-based testing methods continue to be useful. In other situations in which the organism responsible for infection grows slowly (for example, Mycobacterium tuberculosis), culture methods are technically difficult (such as for human immunodeficiency virus), or genotypes are inconsistently expressed (for instance, methicillin resistance in staphylococci), genetic susceptibility testing methods may offer special advantages. Determining serum concentrations of antimicrobial agents may be useful both to ensure adequacy of treatment and to prevent toxicity. In this review, methods are described for conventional and genetic tests used to guide antimicrobial therapy.

Pharmacokinetics and serum bactericidal titers of ciprofloxacin and ofloxacin following multiple oral doses in healthy volunteers

Fourteen adult males participated in a randomized three-way crossover study to compare the pharmacokinetics and serum bactericidal titers (SBTs) of 500 mg of ciprofloxacin (regimen A), 750 mg of ciprofloxacin (regimen B), and 400 mg of ofloxacin (regimen C) administered every 12 h for seven doses. Mean steady-state peak concentrations in serum for regimens A, B, and C were 3.0, 4.4, and 6.5 micrograms/ml, respectively (P < 0.01, all comparisons) and mean half-lives were 4.5, 4.3, and 6.5 h, respectively (P < 0.05, C versus A and B). Mean steady-state areas under the concentration-time curve were 14.1, 21.1, and 48.1 micrograms/h/ml for regimens A, B, and C, respectively (P < 0.05, all comparisons). SBTs were determined at different times postdose for three isolates each of Streptococcus pneumoniae, Staphylococcus aureus, Escherichia coli, Enterobacter cloacae, and Pseudomonas aeruginosa. Mean steady-state peak SBTs for regimens A, B, and C, respectively, were as follows: S. pneumoniae, < 1:2, 1:8, 1:8, S. aureus, 1:16, 1:16, 1:16; E. coli, 1: > or = 128, 1: > or = 128, 1:64; E. cloacae, 1: > or = 128, 1: > or = 128, 1:64; P. aeruginosa, 1:8, 1:8, 1:2. These differences in SBTs within each genus were statistically significant. The majority of predicted SBTs were within one dilution of measured SBTs. Areas under the serum bactericidal time curves for E. coli, E. cloacae, and P. aeruginosa were significantly higher for ciprofloxacin; areas under the serum bactericidal time curves for S. pneumoniae and S. aureus were significantly greater for ofloxacin. Ofloxacin achieved higher concentrations in serum than ciprofloxacin, but differences in in vitro activity were a more important determinant of SBTs.

Tests for bactericidal effects of antimicrobial agents: technical performance and clinical relevance

Bactericidal testing has been used for several decades as a guide for antimicrobial therapy of serious infections. Such testing is most frequently performed when bactericidal antimicrobial agent therapy is considered necessary (such as when treating infectious endocarditis or infection in an immunocompromised host). It has also been used to ensure that the infecting organism is killed by (not tolerant to) usually bactericidal compounds. However, few data are available to support the role of such tests in direct patient care. Several important variables affect the reproducibility of the test results; however, proposed reference methods are now available for performing the MBC test. With minor modifications, these can provide a standardized approach for laboratories that need to perform them. Currently, little evidence is available to support the routine use of such testing for the care of individual patients. However, testing of new (investigational) antimicrobial agents can be beneficial in determining their potential to provide bactericidal antimicrobial activity during clinical use. New methods to assess bactericidal activity are being developed, but as yet none have been rigorously tested in patient care settings; further, for most of these methods, little information is available as to which technical parameters affect their results. In clinical laboratories, all bactericidal tests must be performed with rigorously standardized techniques and adequate controls, bearing in mind the limitations of the currently available test procedures.

Laboratory tests used to guide antimicrobial therapy

Laboratory tests that are usually considered helpful in guiding antimicrobial therapy include antimicrobial agent susceptibility tests, determination of bacterial production of beta-lactamase, and assay of specific antimicrobial levels in serum and other body fluids. Susceptibility tests should be performed primarily on clinically significant isolates from critical specimens (such as blood or other normally sterile body fluids or tissues) with use of standardized methods established by the National Committee for Clinical Laboratory Standards. Reporting of results should be selective so that clinicians are encouraged to use the least expensive but useful agent in a group--for example, first-generation rather than third-generation cephalosporins. Because standardized methods are not available for assays of serum inhibitory and bactericidal activity, the accuracy and clinical utility of these tests are as yet undetermined. Determination of bacterial resistance to antimicrobial agents is the most important goal of susceptibility testing. Special methods are needed to detect methicillin-resistant staphylococci, high-level aminoglycoside- and glycopeptide-resistant enterococci, and antimicrobial-resistant strains of Neisseria gonorrhoeae, Streptococcus pneumoniae, and Haemophilus influenzae. Accurate measurement of serum concentrations of antimicrobial agents is important to ensure that therapeutic levels have been obtained and to avoid excessive levels of potentially toxic agents such as aminoglycosides and glycopeptides, especially when renal function is compromised.

Minimal bactericidal and inhibitory concentrations of ofloxacin on Mycobacterium fortuitum at pH 7 and 5: therapeutic implications

Mycobacterium fortuitum infections of sternotomy wounds have been successfully treated with ofloxacin, a fluoroquinolone. We studied the MBCs and MICs in vitro of this antibiotic on the organism under neutral pH (7) and acidic pH (5) and found marked escalation of these values under the latter condition. This provides hints on the therapy of these infections under in vivo settings.

Effects of supraphysiologic temperature and broth dilution on serum protein binding

Pooled human serum, unheated (UU) and heated at 56 degrees C for 30 (HU-30) and 60 (HU-60) min, and these media diluted 1:1 with broth (UD, HD-30, and HD-60) were used to assess the effects of supraphysiologic temperature and broth dilution on the serum protein binding of ceftriaxone. Protein binding was determined by ultrafiltration and subsequent high-performance liquid chromatography analysis. Significant differences in protein binding between UU and HU-60 (P less than 0.05), UD and HD-60 (P less than 0.01), HD-30 and HD-60 (P less than 0.01), and all undiluted and diluted media (P less than 0.01) were found. These alterations in protein binding may influence the in vitro microbiologic testing of highly protein-bound antibiotics.

Influence of rifampin therapy on serum bactericidal activity in the presence of cloxacillin and vancomycin

In this study the effect of rifampin on serum inhibitory and serum bactericidal titres was examined. Sera were prepared from pooled human serum to contain vancomycin (10 mg/L), cloxacillin (5 mg/L) or rifampin (1 mg/L), and the combinations cloxacillin/rifampin and vancomycin/rifampin. These five sera were tested by a microtitre method for serum inhibitory power and serum bactericidal titre against 11 strains of Staphylococcus aureus. A 48 h incubation period was required to detect full colony growth for subculture plates. It was found with all strains that the effect of the addition of rifampin to the other two antibiotics was to increase the serum inhibitory power, lower the serum bactericidal titre, increase the inhibitory/cidal ratio, and slow colony growth on subculture. In the clinical part of the study it was shown that only three of 38 sera (8%) from patients receiving betalactam or vanomycin but not rifampin gave an inhibitory/cidal ratio greater than 8, but that nine of 10 sera (90%) from patients receiving rifampin in addition to betalactam or vancomycin gave a ratio greater than 8 (P<0.001). The study verified that the effect of rifampin in serum was to increase inhibitory power and decrease bactericidal titre. The clinical significance of these results is not known and it is suggested that a high ratio of inhibitory to bactericidal titre in the presence of rifampin is to be expected, and that a low bactericidal titre under these circumstances is not necessarily an indication to modify therapy.

Clinical implications of positive blood cultures

Positive blood cultures can be classified according to their veracity (true-positive or false-positive culture), clinical severity (inconsequential or life threatening), place of origin (community acquired or nosocomial), source (primary or secondary), duration (transient, intermittent, or continuous), pattern of occurrence (single episode, persistent, or recurrent), or intensity (high or low grade). In general, however, positive blood cultures identify a patient population at high risk of death. In my studies, patients with positive blood cultures were 12 times more likely to die during hospitalization than patients without positive blood cultures. Many bacteremias and fungemias occur in complicated clinical settings, and it appears that only about one-half of the deaths among affected patients are due directly to infection. Hence, it is appropriate to speak of "crude mortality" and "attributable mortality." Among hospitalized patients, recent trends include rising incidences of Staphylococcus aureus and coagulase-negative staphylococcal and enterococcal bacteremias and a dramatic increase in the incidence of fungemias. The diagnostic and therapeutic implications of blood cultures positive for specific microorganisms continue to evolve and are the subject of a large and growing medical literature.

Serum inhibitory and bactericidal activity of ciprofloxacin following intravenous administration

Serum inhibitory and bactericidal titers were measured in nine healthy volunteers following single iv doses of ciprofloxacin 100, 150, and 200 mg. The median peak serum bactericidal titer (5 minutes following completion of a 30-minute infusion) against two highly susceptible strains of Escherichia coli ranged between 1:64 and 1:1024 and titers exceeded 1:8 for six hours for all dose levels. The bactericidal titers against two strains of Pseudomonas aeruginosa and a methicillin-resistant strain of Staphylococcus aureus were considerably lower, the median peak being 1:2 at all dose levels. Measured inhibitory and bactericidal titers at five minutes and one hour postinfusion were significantly greater than those predicted (measured serum ciprofloxacin concentration to minimum inhibitory concentration [MIC] or minimum bactericidal concentration [MBC]) for only one strain of E. coli. Intravenous doses of ciprofloxacin 100-200 mg produce high and sustained serum bactericidal titers against highly susceptible bacteria; considerably lower levels of activity are seen against bacteria having higher MICs and MBCs but still considered susceptible to the drug.

Susceptibility testing today: myth, reality, and new direction

Recent concerns about the clinical relevance of susceptibility testing echo those expressed previously by a number of authors.’-” These concerns are well founded and are perhaps even more important today because of the proliferation of new antibiotics and the changes in reimbursement philosophy.” Ultimately, the question becomes that raised by David Greenwood: “In vitro veritas?” The following discussion will review the role of susceptibility testing in clinical medicine with emphasis on myth versus reality. In addition, new directions for susceptibility testing that promise increased clinical relevance will be covered.