Bacterial meningitis: an update of new treatment options

The outcome of bacterial meningitis critically depends on the rapid initiation of bactericidal antibiotic therapy and adequate management of septic shock. In community-acquired meningitis, the choice of an optimum initial empirical antibiotic regimen depends on the regional resistance patterns. Pathogens resistant to antibacterials prevail in nosocomial bacterial meningitis. Dexamethasone is recommended as adjunctive therapy for community-acquired meningitis in developed countries. In comatose patients, aggressive measures to lower intracranial pressure <20 mmHg (in particular, external ventriculostomy, osmotherapy and temporary hyperventilation) were effective in a case–control study. Although many experimental approaches were protective in animal models, none of them has been proven effective in patients. Antibiotics, which are bactericidal but do not lyse bacteria, and inhibitors of matrix metalloproteinases or complement factor C5 appear the most promising therapeutic options. At present, vaccination is the most efficient method to reduce disease burden. Palmitoylethanolamide appears promising to enhance the resistance of the brain to infections.     

Meningitis (II)--acute bacterial meningitis

Acute meningitis is a medical emergency, particularly in patients with rapidly progressing disease, mental status changes or neurological deficits. The majority of cases of bacterial meningitis are caused by a limited number of species, i.e. Streptococcus pneumoniae, Neisseria meningitis, Listeria monocytogenes, group B Streptococci (Streptococcus agalactiae), Haemophilus influenzae and Enterobacteriaceae. Many other pathogens can occasionally cause bacterial meningitis, often under special clinical circumstances. Treatment of meningitis includes two main goals: Eradication of the infecting organism, and management of CNS and systemic complications. Empiric therapy should be initiated without delay, as the prognosis of the disease depends on the time when therapy is started. One or two blood cultures should be obtained before administering the first antibiotic. Empiric therapy is primarily based on the age of the patient, with modifications if there are positive findings on CSF gram stain or if the patient presents with special risk factors. It is safer to choose regimens with broad coverage, as they can usually be modified within 24-48 hours, when antibiotic sensitivities of the infecting organism become available. Adjunctive therapy with dexamethasone is also administered in severely ill patients concomitantly with the first antibiotic dose. In patients who are clinically stable and are unlikely to be adversely affected if antibiotics are not administered immediately, including those with suspected viral or chronic meningitis, a lumbar puncture represents the first step, unless there is clinical suspicion of an intracerebral mass lesion. Findings in the CSF and on CT scan, if performed, will guide the further diagnostic work-up and therapy in all patients.     

Treatment of bacterial meningitis

Major epidemiological changes have altered the empiric therapy of patients with bacterial meningitis, a disease with significant morbidity and mortality. We offer recommendations for empiric management decisions and specific antibiotic choices for patients with bacterial meningitis.     

Prevention of brain injury by the nonbacteriolytic antibiotic daptomycin in experimental pneumococcal meningitis

Bacteriolytic antibiotics cause the release of bacterial components that augment the host inflammatory response, which in turn contributes to the pathophysiology of brain injury in bacterial meningitis. In the present study, antibiotic therapy with nonbacteriolytic daptomycin was compared with that of bacteriolytic ceftriaxone in experimental pneumococcal meningitis, and the treatments were evaluated for their effects on inflammation and brain injury. Eleven-day-old rats were injected intracisternally with 1.3 x 10(4) +/- 0.5 x 10(4) CFU of Streptococcus pneumoniae serotype 3 and randomized to therapy with ceftriaxone (100 mg/kg of body weight subcutaneously [s.c.]; n = 55) or daptomycin (50 mg/kg s.c.; n = 56) starting at 18 h after infection. The cerebrospinal fluid (CSF) was assessed for bacterial counts, matrix metalloproteinase-9 levels, and tumor necrosis factor alpha levels at different time intervals after infection. Cortical brain damage was evaluated at 40 h after infection. Daptomycin cleared the bacteria more efficiently from the CSF than ceftriaxone within 2 h after the initiation of therapy (log(10) 3.6 +/- 1.0 and log(10) 6.3 +/- 1.4 CFU/ml, respectively; P < 0.02); reduced the inflammatory host reaction, as assessed by the matrix metalloproteinase-9 concentration in CSF 40 h after infection (P < 0.005); and prevented the development of cortical injury (cortical injury present in 0/30 and 7/28 animals, respectively; P < 0.004). Compared to ceftriaxone, daptomycin cleared the bacteria from the CSF more rapidly and caused less CSF inflammation. This combined effect provides an explanation for the observation that daptomycin prevented the development of cortical brain injury in experimental pneumococcal meningitis. Further research is needed to investigate whether nonbacteriolytic antibiotic therapy with daptomycin represents an advantageous alternative over current bacteriolytic antibiotic therapies for the treatment of pneumococcal meningitis.     

Development status of new antibacterials

The increase of the infections caused by multi-drug-resistant bacteria is a serious problem worldwide. As for Gram-positive bacteria, the community-acquired methicillin-resistant Staphylococcus aureus and vancomycin- or linezolid-resistant strains have been increasing. As for Gram-negative bacteria, multi-drug-resistant strains of Enterobacteriaceae, Pseudomonas aeruginosa and Acinetobacter baumannii have been increasing due to the carbapenemase production recently. During these 10 years, various types of novel antibacterials targeted for Gram-positive bacteria have been approved in US and EU, but not in Japan. On the other hand, the discovery of new antibacterials targeted for Gram-negative bacteria is still immature. In this review, the status of the discovery of new antibacterials targeted for these multi-drug-resistant bacteria will be reviewed.     

One-step heminested PCR for amplification of Neisseria meningitidis DNA in cerebrospinal fluid

A one-step polymerase chain reaction (Heminested-PCR) was designed to target the 16S rRNA fragment simultaneously using a set of primers for the universal bacterial group and a Neisseria meningitidis species-specific sequence for diagnostic purposes. The diagnostic features of the Heminested-PCR were evaluated in the study of 168 cerebrospinal fluid (CSF) specimens from 84 patients with a N. meningitidis infection, meningitis caused by unrelated bacteria and other etiologies (57 patients), or suspicious cases (27 patients) with clinical symptoms of bacterial meningitis but with negative results from bacteriological procedures. About 90% of patients with bacterial meningitis, including those suspicious cases, had prior antibiotic therapy. The sensitivity, specificity, positive, and negative predictive values found in relation to culture and/or microscopy were 91.7, 100, 100, 100, and 90.5%, respectively. In patients suspected of having bacterial meningitis, the Heminested-PCR revealed 51.9% (14 patients) positive for N. meningitidis infection and 40.7% (11 patients) positive for unrelated bacterial infections. The agreement of the Heminested-PCR with culture and/or microscopy was high and ranked as almost perfect (kappa indices > 0.856), in contrast to its agreement with other techniques. These findings speak in favor of the molecular diagnosis of meningococcal meningitis in patients who are culture- and/or microscopy-negative, due to their prior antibiotic treatment.     

The impact of new diagnostic methodologies in the management of meningitis in adults at a teaching hospital

BACKGROUND:Suspected meningitis is a frequent reason for admission to hospital in the UK. While bacterial meningitis requires prompt antibiotic therapy to reduce mortality and morbidity, enteroviral meningitis, the most frequent viral cause, is almost invariably a benign disease. Aim: To determine the clinical presentation, laboratory findings and outcome of meningitis by microbiological aetiology and patient age, and to assess the clinical management of adults presenting with meningitis, with reference to national guidelines. DESIGN:Retrospective case-note review. METHODS:Adult (>14 years) admissions to Addenbrooke's Hospital with meningitis or meningococcal septicaemia March 1996-September 2001 were audited retrospectively. The case definition was: symptoms compatible with meningitis, and either abnormal CSF (leukocytes >5x10(9)/ml) or meningococcal disease. The only exclusion criterion was the presence of a ventricular shunt. RESULTS:Only 30% of patients seen by a General Practitioner were given pre-admission antibiotics. In a substantial number of cases, including those with bacterial meningitis, antibiotic administration was delayed either because patients were sent for CT head scans (delaying a lumbar puncture) or because the diagnosis was not considered, especially in elderly patients with reduced conscious levels. There were no confirmed cases of H. influenzae meningitis. Overall outcomes in terms of mortality and disability were similar to UK national data. A surprising number of patients (40%) were afebrile on admission. DISCUSSION:The proportion of patients with meningitis given pre-hospital antibiotics by GPs is still worryingly low, although early hospital management has improved. Improved diagnostic facilities, particularly viral PCR assays, reduce antibiotic usage and hospital stay, with considerable financial savings.     

Therapy of Penicillin- and Cephalosporin-resistant Pneumococcal Infections

Streptococcus pneumoniae has recently developed resistance to almost every agent that has been used for therapy, including the extended-spectrum cephalosporins. The empiric therapy of penicillin-resistant pneumococcal meningitis should include cefotaximine or ceftriaxone plus vancomycin pending cephalosporin susceptibility results. Intermediate penicillin-resistant pneumococcal infections outside the central nervous system will usually respond to high dose intravenous β-lactam antibiotic therapy. Highly penicillin-resistant pneumococcal infections may not respond to penicillin therapy, in which case therapy with vancomycin, imipenem or a macrolide (if susceptible) can be considered. Pneumococcal resistance to commonly used oral agents varies geographically and the efficacy of a particular agent can only be assured once the infecting strain is known to be susceptible. It is imperative to determine the susceptibility of every pneumococcal isolate to the agent(s) being used for therapy, particularly in cases of meningitis and to document rapid sterilization of infected body sites or fluids.     

Klebsiella pneumoniae meningitis: timing of antimicrobial therapy and prognosis

We analysed the clinical course of 30 adult patients with Klebsiella pneumoniae meningitis, 18 community-acquired and 12 hospital-acquired, to assess whether the timing of appropriate antimicrobial therapy had a major effect on prognosis. Of the 30 patients, 29 received appropriate antibiotics. The time from initial symptoms to the start of appropriate therapy, antibiotic resistance of K. pneumoniae isolates, underlying disease severity, diabetes mellitus, age, gender, and acquisition settings were all not significantly correlated with outcome. However, a Glasgow coma scale (GCS) score of 7 points or less at the start of appropriate antimicrobial therapy was a valid predictor of death or a permanent vegetative state (sensitivity 82%, specificity 93%, p=0.005), even after adjusting for the effect of confounding variables by logistic regression. Timing of appropriate antimicrobial therapy, as defined by consciousness level but not by symptom duration, is a major determinant of survival and neurological outcome for patients with K. pneumoniae meningitis, and the first dose of an appropriate antibiotic should be administrated before their consciousness deteriorates to a GCS score of 7 points or less.     

Meningitis (I)--differential diagnosis; aseptic and chronic meningitis

Meningitis is the most common serious manifestation of infection of the central nervous system. Inflammatory involvement of the subarachnoid space with meningeal irritation leads to the classical triad of headache, fever, and meningism, and to a pleocytosis of the cerebrospinal fluid (CSF). Meningitis is clinically categorized into an acute and chronic disease based on the acuity of symptoms. Acute meningitis develops over hours to days, while in chronic meningitis symptoms evolve over days or even weeks. Aseptic meningitis, in which no bacterial pathogen can be isolated by routine cultures, can mimic bacterial meningitis, but the disease has a much more favorable prognosis. Many cases of aseptic meningitis are caused by viruses, primarily enteroviruses, but bacteria and noninfectious etiologies also cause meningitis with negative cultures. Symptoms of meningeal inflammation with CSF pleocytosis that persist for more than 4 weeks define the chronic meningitis syndrome. The diagnosis is based on the patient history, clinical evidence of meningitis, CSF examination, and often imaging studies. The differential diagnosis is broad, and the predominant CSF cell type can provide clues as to the underlying disease. Empiric therapy is primarily based on the age of the patient, with modifications if there are positive findings on CSF gram stain or if the patient presents with special risk factors. In patients with chronic meningitis, a definite diagnosis is often not available or delayed for days, in which case empiric therapy may have to be initiated. It is important to cover the treatable causes of meningitis, for which the outcome is poor if treatment is delayed.     

Adjunctive dexamethasone therapy for pediatric bacterial meningitis

There have been numerous studies performed to assess the impact of adjunctive corticosteroid therapy on the outcome of pediatric bacterial meningitis. Much of these data are conflicting, which can result in confusion regarding therapeutic efficacy. The present article will review the pathophysiology of this disease, critique the body of medical literature on this aspect of therapy, and provide guidelines for the emergency physician on the use of dexamethasone therapy for bacterial meningitis in children.     

Cerebrospinal fluid outflow resistance in rabbits with experimental meningitis. Alterations with penicillin and methylprednisolone.

Acute bacterial meningitis may be associated with increased intracranial pressure, neurological sequelae such as communicating hydrocephalus, and a slow response to antibiotic therapy. Alterations in cerebrospinal hydrodynamics are at least partially responsible for these complications. Constant, low-flow short-duration manometric infusion studies through a hollow-bore pressure monitoring device in direct continuity with the supracortical subarachnoid space were performed in rabbits with experimental meningitis. Maximal resistance to cerebrospinal fluid (CSF) outflow from the subarachnoid to vascular space was markedly increaed in acute pneumococcal meningitis when compared to control, uninfected animals (6.77 +/- 3.52 vs. 0.26 +/- 0.04 mm Hg/microliter per min, P less than 0.001). Similar elevations (8.93 +/- 4.15 mm Hg/microliter per min were found in experimental Escherichia coli meningitis. Despite eradication of viable bacteria from the CSF by penicillin therapy during the acute stage of pneumococcal meningitis, resistance remained elevated (6.07 +/- 4.68 mm Hg/microliter per min) and had not returned to normal up to 15 d later. Administration of methylprednisolone during the early stages of acute pneumococcal meningitis reduced mean peak outflow resistance towards control values (0.59 mm Hg/microliter per min) and no "rebound" effect was apparent 24 h later. These hydrodynamic alterations in experimental meningitis prevent normal CSF absorption and decrease the ability of the bran to compensate for changes in intracranial volume and pressure.     

The 2000 Garrod lecture. Factors impacting on the problem of antibiotic resistance.

Antibiotic resistance has become a major clinical and public health problem within the lifetime of most people living today. Confronted by increasing amounts of antibiotics over the past 60 years, bacteria have responded to the deluge with the propagation of progeny no longer susceptible to them. While it is clear that antibiotics are pivotal in the selection of bacterial resistance, the spread of resistance genes and of resistant bacteria also contributes to the problem. Selection of resistant forms can occur during or after antimicrobial treatment; antibiotic residues can be found in the environment for long periods of time after treatment. Besides antibiotics, there is the mounting use of other agents aimed at destroying bacteria, namely the surface antibacterials now available in many household products. These too enter the environment. The stage is thus set for an altered microbial ecology, not only in terms of resistant versus susceptible bacteria, but also in terms of the kinds of microorganisms surviving in the treated environment. We currently face multiresistant infectious disease organisms that are difficult and, sometimes, impossible to treat successfully. In order to curb the resistance problem, we must encourage the return of the susceptible commensal flora. They are our best allies in reversing antibiotic resistance.     

Randomized comparison of meropenem with cefotaxime for treatment of bacterial meningitis. Meropenem Meningitis Study Group.

Broad-spectrum cephalosporins are drugs of choice for the treatment of meningitis in communities which can afford them. The emergence of cephalosporin-resistant pneumococci demands the clinical trial of alternate agents. Carbapenems are active against the bacteria causing meningitis, but the use of imipenem-cilastatin was frustrated by drug-associated seizures. The safety and efficacy of meropenem, a new carbapenem, were compared to those of cefotaxime in a prospective randomized trial of 190 children with bacterial meningitis. Seizures occurred within 24 h before antibiotic therapy in 16 of 98 patients (16%) randomized to receive meropenem and in 6 of 92 patients (7%) randomized to receive cefotaxime. In patients without seizures before therapy, seizures occurred during therapy in 5 of 82 patients (6%) receiving meropenem and in 1 of 86 patients (1%) receiving cefotaxime (95% confidence interval: -0.7%, 10.6%). None were thought to be drug related. Twenty-four meropenem-treated patients (24%) and 11 cefotaxime-treated patients (12%) had neurological abnormalities before therapy. In patients without pretherapy neurological abnormalities, these abnormalities were present after treatment in 4 of 74 meropenem-treated patients (5%) and in 2 of 81 cefotaxime-treated patients (2%) (95% confidence interval: -3.2%, 9.1%). Of 75 meropenem-treated and 64 cefotaxime-treated patients with pretherapy positive cerebrospinal-fluid cultures, 68 and 59, respectively, had repeat lumbar punctures. Bacterial eradication was found to be 100% in both groups. Our data suggest that meropenem may be a carbapenem agent that is well tolerated and effective in the treatment of bacterial meningitis.     

Meningococcal meningitis in critical care: an overview, new treatments/preventions, and a case study

Meningococcal meningitis (MM) is a disease process that can become insidious and deadly in a short amount of time if not properly diagnosed. New and effectively known treatments and preventions are the key to improve recovery. The Neisseria meningitidis (NM) bacteria is the culprit in the MM discussed in this article. The pathophysiology, symptoms, and assessment are important to review, as well as typical antibiotic therapy and other treatments. Morbidity and mortality is affected by the improvement of these therapies. Critical care nurses must correctly and prudently assess their patients quickly for rapid response to treatment. The vaccine for the NM bacteria associated with the serotype B is not available at this time. College freshmen are the most vulnerable population in contracting the disease because of small living spaces and lifestyle habits that increase their association with the disease. The issue of prophylactically giving the vaccine is controversial but may become necessary because of the increase in incidence in the last 5 years on college campuses. Chemoprophylaxis efficacy may also be of help to those healthcare workers exposed as well as to those individuals at high risk for contracting the disease after an exposure. Public health concerns with community and college campus participation and education can be key to a sense of well-being among those possible individuals who may be exposed. Steroid, coagulapathy, and immunotherapy, as well as other new treatments, are worth investigating and pursuing in these times of increased risk to certain vulnerable populations of people.     

Discovery of a Novel Class of Boron-Based Antibacterials with Activity against Gram-Negative Bacteria

Gram-negative bacteria cause approximately 70% of the infections in intensive care units. A growing number of bacterial isolates responsible for these infections are resistant to currently available antibiotics and to many in development. Most agents under development are modifications of existing drug classes, which only partially overcome existing resistance mechanisms. Therefore, new classes of Gram-negative antibacterials with truly novel modes of action are needed to circumvent these existing resistance mechanisms. We have previously identified a new a way to inhibit an aminoacyl-tRNA synthetase, leucyl-tRNA synthetase (LeuRS), in fungi via the oxaborole tRNA trapping (OBORT) mechanism. Herein, we show how we have modified the OBORT mechanism using a structure-guided approach to develop a new boron-based antibiotic class, the aminomethylbenzoxaboroles, which inhibit bacterial leucyl-tRNA synthetase and have activity against Gram-negative bacteria by largely evading the main efflux mechanisms in Escherichia coli and Pseudomonas aeruginosa. The lead analogue, AN3365, is active against Gram-negative bacteria, including Enterobacteriaceae bearing NDM-1 and KPC carbapenemases, as well as P. aeruginosa. This novel boron-based antibacterial, AN3365, has good mouse pharmacokinetics and was efficacious against E. coli and P. aeruginosa in murine thigh infection models, which suggest that this novel class of antibacterials has the potential to address this unmet medical need.     

Meningococcal disease: treatment and prevention

Many countries have been experiencing a significant increase in meningococcal disease. With the strains currently circulating, septicaemia is now a more frequent manifestation than meningitis and early recognition of disease manifestations by patient, parent or physician as well as early recognition of disease severity are the most important factors in attempting to reduce mortality and morbidity. Ceftriaxone is the treatment of choice but must be accompanied by aggressive supportive therapy in those with severe disease. The role of steroids is unknown. The evidence to support their use in both meningitis and severe systemic sepsis is discussed. The purified polysaccharide vaccines that have been available for some years may play a limited role in disease prevention. The recently introduced conjugate vaccine for preventing serogroup C disease represents a major advance but no vaccine is currently available to prevent serogroup B disease, cases of which will continue to challenge clinical practice.     

An experimental analysis of the curative action of penicillin in acute bacterial infections. III. The effect of suppuration upon the antibacterial action of the drug

The results of the experimental analysis reported in this and the two preceding papers (10, 11) indicate that in murine pneumococcal infections penicillin per se destroys the invading organisms only in those parts of the lesions where the bacteria are multiplying rapidly and are thus maximally susceptible to the bactericidal action of the drug. In areas where the bacterial growth rate is slowed, either because the pneumococci have reached a maximum population density, or because the accumulated exudate affords a relatively poor medium for rapid growth, the destructive effect of the antibiotic is greatly diminished. In such portions of the lessions the cellular defenses of the host are observed to play a major role in eliminating the bacteria. In sites where frank suppuration has developed, however, even the combined actions of the penicillin and the cellular defenses of the host are relatively ineffective in ridding the tissues of bacteria. Here, because of the poor medium provided by the pus, the pneumococci remain metabolically sluggish and therefore are not killed rapidly by the penicillin. At the same time the leucocytes in the necrotic exudate have deteriorated to the point where they cannot effectively perform their phagocytic functions. As a result, bacteria persist in such lesions for many days in spite of the most intensive penicillin treatment administered both locally and systemically. A strict analogy cannot be drawn between the action of penicillin upon specific pneumococcal lesions produced in the laboratory and its effect upon acute bacterial infections in man. Host-parasite relationships in acute bacterial infections are determined not only by the strain of parasite and the specific host involved, but also by the site in the body at which the infection occurs (16). Nevertheless, in spite of the number of variables involved, it may be possible, by means of selected laboratory models, to illustrate general principles of infection which in all probability apply to human disease. Bearing in mind the limitations of the methods employed in the present experiments, it would appear justifiable to draw the following conclusions concerning the clinical use of penicillin in acute infections caused by penicillin-sensitive bacteria. The earlier that treatment is begun the more likely is penicillin to effectuate a rapid cure. When therapy is started before the bacteria have reached a maximum population density in any part of the lesion, and before a cellular exudate is formed, the great majority of the infecting organisms will be in a state of active multiplication and thus will be killed promptiy by the bactericidal action of the drug. If, on the other hand, treatment is delayed until the bacterial growth has attained its maximum in older parts of the lesion, and the inflammatory reaction has become well advanced, the resultant slowing of bacterial metabolism will so interfere with the bactericidal action of the penicillin that ultimate destruction of many of the bacteria will have to depend upon the slower clearing effect of the phagocytic cells. In such instances of delayed therapy specific antibody, which is formed relatively slowly, may play an important role in recovery (6). If relapse is to be avoided, however, penicillin therapy must often be continued longer in well established infections than in those treated at a very early stage. Still further delay in treating infections which are prone to cause tissue destruction and suppuration, may lead to the establishment of abscesses. Fully developed abscesses often will not respond to chemotherapy alone; they will ultimately require drainage. As shown by the present murine experiments, the relative ineffectiveness of penicillin under these circumstances is due not only to the failure of the drug to kill the metabolically sluggish bacteria surviving in the pus, but also to the ineffectiveness of the phagocytic cells, most of which are non-motile or dead. Even if specific antibody gains access to such purulent foci, many of the bacteria will continue to survive because of the degenerated state of the leucocytes. It is evident, therefore, that the stage of the infection at which penicillin treatment is begun is often crucial. Equally critical may be the location of the infection. Bacterial lesions in different sites of the body vary greatly in their responses to penicillin therapy. This inconstancy of therapeutic effectiveness is due primarily to the participation of host factors of defense which differ widely in various tissues and at the same time play a major role in the curative action of the antibiotic. In cases of pneumococcal pneumonia, for example, in which each milliliter of the patient's blood contains more than 1000 pneumococci, blood cultures may become negative in a matter of minutes after the start of intensive treatment (17). The remarkable promptness with which penicillin therapy controls such acute bacteriemia is due, first, to its suppressive effect upon the primary infection in the lungs and regional lymph nodes from which the bacteria are being poured into the blood stream (16) and, secondly, to its synergistic action with the cellular defenses of the circulation. The latter are known to be extraordinarily efficient, perhaps more so than in any other tissue of the body (18). Assisting them in destroying the circulating bacteria is the penicillin's own bactericidal effect, which operates rapidly upon the metabolically active organisms in the plasma. Rarely, if ever, as they often do in other tissues of the body (10), do bacteria in the bloodstream reach such numbers, or do inflammatory cells accumulate intravascularly to such an extent, as to create metabolic conditions which depress the bactericidal actions of the antibiotic. In contrast, more prolonged and extensive penicillin therapy is needed to cure pneumococcal endocarditis (19), meningitis (19, 20), or infections of the serous cavities (3, 4). The cellular defenses of the heart valves and of the "open" fluid-containing cavities of the body are relatively inefficient as compared to those that operate in the bloodstream and in tissues with tightiy knit architectures such as the lungs and lymph nodes (16). In endocarditis relatively few phagocytic cells ever reach the site of the offending bacteria (21), and in infections of fluid-containing cavities, the phagocytic efficiency of the mobilized leucocytes is seriously interfered with by the "dilution effect" of the fluid (22, 23). Accordingly, final destruction of the bacteria must depend primarily upon the bactericidal effect of the antibiotic itself, since little assistance is provided by phagocytosis. It is no wonder, therefore, that such infections, as compared to bacteriemia, are relatively refractory to penicillin therapy. Certainly penicillin, in spite of its remarkable therapeutic properties, falls far short of being a therapia sterilans magna (24). Its effectiveness does not depend solely upon the inherent susceptibility of the infecting agent to its antimicrobial action. How readily it will cure a given infection is determined also by the state of growth of the bacteria in the various zones of the lesions, the influence of the purulent exudate upon the bactericidal action of the drug, and the destructive effect of the inflammatory phagocytes upon the invading bacteria. Optimal use of penicillin as a therapeutic agent requires due consideration of all of these factors. Finally, it should be emphasized that the conclusions drawn from this experimental analysis cannot be applied to antibiotic therapy in general. They pertain only to the action of penicillin in acute infections caused by penicillin-sensitive bacteria which act in the host as extracellular parasites (16). The most common human infections included in this category are those caused by pneumococci and Group A beta hemolytic streptococci.⁷ Whether they apply also to infections due to penicillin-sensitive staphylococci may be questioned because of recent evidence that certain pathogenic strains will survive phagocytosis (27). In diseases such as tuberculosis, brucellosis, and typhoid fever, which are treated with antibiotics having properties different from those of penicillin (28) and which are caused by bacteria capable of intracellular parasitism (28), factors other than those considered in the present analysis must certainly be involved in the curative effect of antimicrobial therapy.     

Détection génotypique des résistances bactériennes : de la phénotypie à la génotypie,deux méthodes complémentaires

The problem of emerging resistance urges clinicians to prescribe narrow-spectrum antibiotic targeted to the specific causative pathogen. In hospital, a high level of antibiotic use and a propensity for genetic exchange between bacteria provide a perfect environment for multiresistant micro-organisms. Detection of antimicrobial resistance is important to optimise decisions about antimicrobial therapy. In order to prevent or to slow the spread of resistance among bacterial strains, clinicians must know as soon as possible which bacteria they are dealing with and to which antibiotic the strain is susceptible. This essential information can take several days up to weeks using traditional culture-based methods. In most cases such phenotypic susceptibility tests continue to be useful and get improve. Now automated systems are available to determine the infectious strain and its susceptibility to antibiotics within hours. In the near future, genetic methods as DNA-based solutions will be able to identify an infectious agent and its resistance pattern in less than an hour. Applied DNA technology progresses and will lead to the development and application of sophisticated new strategies for the analysis of antibiotic resistant bacterial strains. In the present knowledge, both methods for the determination of antimicrobial resistance, the phenotypic and the genotypic tests, are complementary.     

Meningococcal disease: treatment and prevention

Many countries have been experiencing a significant increase in meningococcal disease. With the strains currently circulating, septicaemia is now a more frequent manifestation than meningitis and early recognition of disease manifestations by patient, parent or physician as well as early recognition of disease severity are the most important factors in attempting to reduce mortality and morbidity. Ceftriaxone is the treatment of choice but must be accompanied by aggressive supportive therapy in those with severe disease. The role of steroids is unknown. The evidence to support their use in both meningitis and severe systemic sepsis is discussed. The purified polysaccharide vaccines that have been available for some years may play a limited role in disease prevention. The recently introduced conjugate vaccine for preventing serogroup C disease represents a major advance but no vaccine is currently available to prevent serogroup B disease, cases of which will continue to challenge clinical practice.