Listeria monocytogenes meningitis in adults. Sixteen consecutive cases 1973-1982

Three-year multicenter surveillance of community-acquired Listeria monocytogenes meningitis in adults

Background

Listeria monocytogenes is the third most frequent cause of bacterial meningitis. The aim of this study is to know the incidence and risk factors associated with development of acute community-acquired Lm meningitis in adult patients and to evaluate the clinical features, management, and outcome in this prospective case series.

Methods

A descriptive, prospective, and multicentric study carried out in 9 hospitals in the Spanish Network for Research in Infectious Diseases (REIPI) over a 39-month period. All adults patients admitted to the participating hospitals with the diagnosis of acute community-acquired bacterial meningitis (Ac-ABM) were included in this study. All these cases were diagnosed on the basis of a compatible clinical picture and a positive cerebrospinal fluid (CSF) culture or blood culture. The patients were followed up until death or discharge from hospital.

Results

Two hundred and seventy-eight patients with Ac-ABM were included. Forty-six episodes of Lm meningitis were identified in 46 adult patients. In the multivariate analysis only age (OR 1.026; 95% CI 1.00-1.05; p = 0.042), immunosupression (OR 2.520; 95% CI 1.05-6.00; p = 0.037), and CSF/blood glucose ratio (OR 39.42; 95% CI 4.01-387.50; p = 0.002) were independently associated with a Lm meningitis. The classic triad of fever, neck stiffness and altered mental status was present in 21 (49%) patients, 32% had focal neurological findings at presentation, 12% presented cerebellum dysfunction, and 9% had seizures. Twenty-nine (68%) patients were immunocompromised. Empirical antimicrobial therapy was intravenous ampicillin for 34 (79%) of 43 patients, in 11 (32%) of them associated to aminoglycosides. Definitive ampicillin plus gentamicin therapy was significantly associated with unfavourable outcome (67% vs 28%; p = 0.024) and a higher mortality (67% vs 32%; p = 0.040).The mortality rate was 28% (12 of 43 patients) and 5 of 31 (16.1%) surviving patients developed adverse clinical outcome.

Conclusions

Elderly or immunocompromised patients, and a higher CSF/blood glucose ratio in patients with Ac-ABM must alert clinicians about Lm aetiology. Furthermore, we observed a high incidence of acute community-acquired Lm meningitis in adults and the addition of aminoglycosides to treatment should be avoid in order to improve the patients' outcome. Nevertheless, despite developments in intensive care and antimicrobial therapy, this entity is still a serious disease that carries high morbidity and mortality rates.

Listeria monocytogenes encephalitis mimicking Herpes Simplex virus encephalitis: the differential diagnostic importance of cerebrospinal fluid lactic acid levels

Listeria monocytogenes is a common cause of bacterial meningitis in elderly patients and in those with impaired cellular immunity. The most common central nervous system infection caused by L. monocytogenes is acute bacterial meningitis; meningoencephalitis is uncommon and encephalitis is rare. Early diagnosis of L. monocytogenes meningitis is difficult because only 50% of cerebrospinal fluid (CSF) Gram stains are negative. L. monocytogenes is one of the few central nervous system pathogens associated with red blood cells in the CSF. When L. monocytogenes presents as encephalitis with red blood cells in the CSF, the clinical presentation mimics most closely herpes simplex virus (HSV)-1 encephalitis. Because the therapies for L. monocytogenes and HSV-1 are different, early diagnostic differentiation is clinically important. The CSF lactic acid is the best way to rapidly differentiate between these two entities; the CSF lactic acid level is elevated in L. monocytogenes but is not elevated in HSV-1 encephalitis. The case presented is an elderly man with chronic lymphocytic leukemia who presented with encephalitis. Advanced age and chronic lymphocytic leukemia predispose him to a wide variety of pathogens, but the rapidity and severity of his clinical presentation made L. monocytogenes and HSV-1 encephalitis the most likely diagnostic possibilities. The CSF Gram stain was negative, but the elevated CSF lactic acid levels with encephalitis and red blood cells in the CSF indicated L. monocytogenes as the most likely pathogen. We present a case of L. monocytogenes encephalitis mimicking HSV-1 encephalitis. While receiving ampicillin therapy, the patient remained unresponsive for more than 1 week and then suddenly regained consciousness and recovered without neurologic sequelae.

Listeria monocytogenes encephalitis mimicking West Nile encephalitis

We present a case of a 50-year-old man who presented to Winthrop-University Hospital in the midst of the 2002 West Nile encephalitis (WNE) outbreak with the cardinal clinical findings of WNE, ie, fever, encephalopathy, weakness, and muscle tremors. During the summer of 2002, several cases of aseptic meningitis/viral encephalitis were admitted to our emergency room weekly. In addition, cases of WNE were being admitted at the same time. During this period we had 3 cases of WNE. Our patient presented with the clinical findings of WNE. However, laboratory and radiologic findings suggested the possibility of Listeria monocytogenes encephalitis. The cerebrospinal fluid findings included red blood cells, which, in the absence of a traumatic tap or HSV encephalitis, argue against the diagnosis of WNE but are consistent with L. monocytogenes encephalitis. Computed tomography scan showed communicating hydrocephalus, which also suggests the possibility of L. monocytogenes and argued against the diagnosis of WNE. Clinicians should be vigilant for the mimics of WNE in geographical areas where WNE outbreaks are occurring.

Bacterial meningitis

In recent years, investigators have made significant advances in understanding the pathogenesis of bacterial meningitis, particularly with regard to understanding the cascade of biologic events that cause excessive inflammation within the central nervous system (CNS). Nevertheless, the most important event in the field of bacterial meningitis in the past decade is the dramatic decline in the incidence of Haemophilus influenzae meningitis in children as a result of the widespread use of the conjugated H. influenzae type b vaccine. Currently, the most important clinical challenge in this field is the emergence of the drug-resistant Streptococcus pneumoniae. This problem has significantly complicated initial management of patients with suspected bacterial meningitis. Preliminary data show promise with new conjugated S. pneumoniae vaccines.

Central nervous system infection with Listeria monocytogenes. 33 years' experience at a general hospital and review of 776 episodes from the literature

We reviewed 776 previously reported and 44 new cases of CNS listeriosis outside of pregnancy and the neonatal period, and evaluated the epidemiologic, diagnostic, and therapeutic characteristics of this infection. Among patients with Listeria meningitis/meningoencephalitis, hematologic malignancy and kidney transplantation were the leading predisposing factors, but 36% of patients had no underlying diseases recognized. The infection occurred throughout life, with a higher incidence before the age of 3 and after the age of 45-50 years. Fever, altered sensorium, and headache were the most common symptoms, but 42% of patients had no meningeal signs on admission. Compared with patients with acute meningitis due to other bacterial pathogens, patients with Listeria infection had a significantly lower incidence of meningeal signs, and the CSF profile was significantly less likely to have a high WBC count or a high protein concentration. Gram stain of CSF was negative in two-thirds of cases of CNS listeriosis. One-third of patients had focal neurologic findings, and approximately one-fourth developed seizures over their course. Mortality was 26% overall, and was higher among patients with seizures and those older than 65 years of age. Relapse occurred in 7% of episodes. Ampicillin for a minimum of 15-21 days (with an aminoglycoside for at least the first 7-10 days) remains the treatment of choice. Cerebritis/abscess due to L. monocytogenes, without meningeal involvement, is less common but may be diagnosed by blood cultures and CNS imaging, or by stereotactic biopsy. Longer antibiotic therapy (at least 5-6 weeks) is needed in the presence of localized CNS involvement.

Antimicrobial chemotherapy of human infection due to Listeria monocytogenes

Listeriosis is an uncommon infection, but when it occurs it carries a high mortality rate. Early diagnosis is essential and thereafter appropriate antimicrobial chemotherapy. Ampicillin or penicillin plus gentamicin remains the treatment of choice for most manifestations of listeriosis, and adequate doses must be given, i.e. greater than 6g/day of ampicillin or penicillin. Co-trimoxazole appears to be an excellent alternative agent with good penetration into the cerebrospinal fluid. Vancomycin is an appropriate agent for the treatment of primary bacteraemia but does not cross the blood-brain barrier sufficiently well to be useful in meningitis, while erythromycin may be used to treat listeriosis in cases of pregnancy. Treatment of bacteraemia requires one to two weeks' therapy, while meningitis cases may need to be treated for longer; for example, it has been found that most patients with acute meningitis in the UK were treated for 20 days. Infective endocarditis needs treatment for six to eight weeks. Doses should be varied with patients' altered organ function and antimicrobial serum monitoring performed when appropriate.

Acute Therapy of Bacterial Meningitis

Antimicrobial therapy for bacterial meningitis has markedly reduced mortality rates from this disorder. The efficacy of an antibiotic in meningitis depends on many factors, including its penetration into cerebrospinal fluid (CSF), the bactericidal efficacy of the antibiotic within purulent CSF, and the need for bactericidal activity in CSF because bacterial meningitis represents an infection in an area of impaired host defense. Penicillin G and ampicillin are equally efficacious for meningitis caused by Streptococcus pneumoniae or Neisseria meningitidis. This recommendation may change, however, with the emergence of strains of pneumococci or meningococci that are relatively or highly resistant to penicillin; a third-generation cephalosporin (cefotaxime or ceftriaxone) should be used for meningitis due to relatively resistant strains and vancomycin for pneumococcal meningitis caused by strains that are highly resistant to penicillin. With the high percentage of strains of Haemopbilus influenzae type b that produce β-lactamase, empiric therapy when this organism is suspected should consist of a third-generation cephalosporin; these agents are also used for meningitis caused by enteric gram-negative bacilli, and one agent, ceftazidime, is effective against Pseudomonas aeruginosa meningitis. Despite the availability of effective bactericidal antibiotics, morbidity and mortality from bacterial meningitis remains unacceptably high. Recent studies using animal models of infection have demonstrated the beneficial effect of antiinflammatory agents in attenuating the CSF inflammatory response that may lessen many of the pathophysiological consequences of meningitis. Studies of adjunctive dexamethasone therapy suggest that these agents may reduce morbidity (specifically sensorineural hearing loss) and mortality (due to S. pneumoniae) in patients with bacterial meningitis. Controversy remains, however, concerning the use of dexamethasone in all patients with bacterial meningitis and further studies are necessary. In critically ill patients with bacterial meningitis, control of increased intracranial pressure and seizures may be useful and necessary in improving outcome.

Listeria monocytogenes, a food-borne pathogen

The gram-positive bacterium Listeria monocytogenes is an ubiquitous, intracellular pathogen which has been implicated within the past decade as the causative organism in several outbreaks of foodborne disease. Listeriosis, with a mortality rate of about 24%, is found mainly among pregnant women, their fetuses, and immunocompromised persons, with symptoms of abortion, neonatal death, septicemia, and meningitis. Epidemiological investigations can make use of strain-typing procedures such as DNA restriction enzyme analysis or electrophoretic enzyme typing. The organism has a multifactorial virulence system, with the thiol-activated hemolysin, listeriolysin O, being identified as playing a crucial role in the organism's ability to multiply within host phagocytic cells and to spread from cell to cell. The organism occurs widely in food, with the highest incidences being found in meat, poultry, and seafood products. Improved methods for detecting and enumerating the organism in foodstuffs are now available, including those based on the use of monoclonal antibodies, DNA probes, or the polymerase chain reaction. As knowledge of the molecular and applied biology of L. monocytogenes increases, progress can be made in the prevention and control of human infection.

Characterization of a Listeria monocytogenes-specific protein capable of inducing delayed hypersensitivity in Listeria-immune mice

Recovery of the host after infection by the intracellular pathogen Listeria monocytogenes is dependent on cell-mediated immunity. Little is known of the nature of listerial antigens that induce cell-mediated responses in the infected host. In this study we report on the identification and cloning of an Escherichia coli recombinant encoding a listerial antigen, designated ImaA, capable of eliciting a specific delayed-type hypersensitivity response in Listeria-immune mice. Nucleotide sequencing of the Listeria DNA insert in plasmid pLM10 showed that the ImaA gene product consisted of 170 amino acids with a molecular weight of 17,994. The predicted amino acid sequence suggests that the protein is localized to the bacterial plasma membrane or cell wall. The ImaA gene was unique to the pathogenic species L. monocytogenes and Listeria ivanovii; it was not present in any other species of the genus Listeria.

A selective and diagnostic medium for use in the enumeration of Listeria spp. in foods

A new medium, called RAPAMY agar, has been elaborated for the isolation from and the enumeration of Listeria spp. in foods. It is based on Ralovich's nalidixic acid-trypaflavin-agar with the following modifications: (i) the slight inhibitory properties of that medium were overcome by the use of Columbia Blood agar base instead of tryptose agar and the addition of 0.05% ferric ammonium citrate and 2.5% egg yolk emulsion; (ii) selectivity was improved by the addition of 0.25% 2-phenyl ethanol and incubation under microaerobic conditions; (iii) the medium was provided with two diagnostic traits by the addition of (a) aesculin + ferric ammonium citrate; and (b) D-mannitol and phenol red. The growth of Enterococcus spp., the only organisms other than Listeria spp. which grow on RAPAMY agar, was not inhibited by the addition of 20 microgram.ml-1 Cefoxitin (Moxolactam). Higher levels inhibited some Listeria spp., but not the enterococci. The medium recovered Listeria spp. quantitatively and allowed recovery from foods colonized by Enterococcus spp. at levels upto 10(2) per g.