Prevalence of Neisseria meningitidis relatively resistant to penicillin in the United States, 1991. Meningococcal Disease Study Group

Meningococcal pneumonia: a review

Background

Although Neisseria meningitidis is one of the major causes of meningitis, meningococcal pneumonia is the most common non-neurological organ disease caused by this pathogen.

Methods

We conducted a review of the literature to describe the risk factors, pathogenesis, clinical features, diagnosis, treatment and prevention of meningococcal pneumonia.

Results

Meningococcal pneumonia was first described in 1907 and during the 1918–1919 influenza pandemic large numbers of cases of meningococcal pneumonia occurred in patients following the initial viral infection. A number of publications, mainly case series or case reports, has subsequently appeared in the literature. Meningococcal pneumonia occurs mainly with serogroups Y, W-135 and B. Risk factors for meningococcal pneumonia have not been well characterised, but appear to include older age, smoking, people living in close contact (e.g. military recruits and students at university), preceding viral and bacterial infections, haematological malignancies, chronic respiratory conditions and various other non-communicable and primary and secondary immunodeficiency diseases. Primary meningococcal pneumonia occurs in 5–10% of patients with meningococcal infection and is indistinguishable clinically from pneumonia caused by other common pathogens. Fever, chills and pleuritic chest pain are the most common symptoms, occurring in > 50% of cases. Productive sputum and dyspnoea are less common. Diagnosis of meningococcal pneumonia may be made by the isolation of the organism in sputum, blood, or normally sterile site cultures, but is likely to underestimate the frequency of meningococcal pneumonia. If validated, PCR-based techniques may be of value for diagnosis in the future. While penicillin was the treatment of choice for meningococcal infection, including pneumonia, prior to 1991, a third generation cephalosporin has been more commonly used thereafter, because of concerns of penicillin resistance. Chemoprophylaxis, using one of a number of antibiotics, has been recommended for close contacts of patients with meningococcal meningitis, and similar benefits may be seen in contacts of patients with meningococcal pneumonia. Effective vaccines are available for the prevention of infection with certain meningococcal serogroups, but this field is still evolving.

Conclusion

Meningococcal pneumonia occurs fairly frequently and should be considered as a possible cause of pneumonia, particularly in patients with specific risk factors.

Meningococcal Pneumonia in a Young Healthy Male

A 23-year-old male presented to the emergency department with one-day history of right-sided pleuritic chest pain, haemoptysis, and fever. In the emergency department, the blood pressure was 140/60 mmHg, heart rate 89/min, body temperature 40°C, respiratory rates 20 breaths/min, and oxygen saturation 98% in room air. Physical examination revealed rales and bronchial breathing in the right infrascapular region. Laboratory analysis showed raised white blood cell counts and elevated inflammation markers. Chest X-ray showed right lower lobe consolidation. Intravenous(IV) ceftriaxone and doxycycline were started for the management of community-acquired pneumonia as per the local guideline. Later, on admission, blood culture was positive for Neisseria meningitidis (N. meningitidis). Ceftriaxone was continued for 4 days, and the patient was discharged while being on oral amoxicillin (1 gm TDS) for another 3 days. He remained well during the outpatient follow-up.

Population-Based Surveillance of Neisseria meningitidis Antimicrobial Resistance in the United States

Isolates of Neisseria meningitidis collected in 2004, 2008, 2010, and 2011 from an active population-based surveillance system in the United States were tested for susceptibility to antimicrobials used for treatment and chemoprophylaxis of meningococcal disease. Susceptibility remains high and stable.

Background. Antimicrobial treatment and chemoprophylaxis of patients and their close contacts is critical to reduce the morbidity and mortality and prevent secondary cases of meningococcal disease. Through the 1990's, the prevalence of antimicrobial resistance to commonly used antimicrobials among Neisseria meningitidis was low in the United States. Susceptibility testing was performed to ascertain whether the proportions of isolates with reduced susceptibility to antimicrobials commonly used for N meningitidis have increased since 2004 in the United States.

Methods. Antimicrobial susceptibility testing was performed by broth microdilution on 466 isolates of N meningitidis collected in 2004, 2008, 2010, and 2011 from an active, population-based surveillance system for susceptibility to ceftriaxone, ciprofloxacin, penicillin G, rifampin, and azithromycin. The molecular mechanism of reduced susceptibility was investigated for isolates with intermediate or resistant phenotypes.

Results. All isolates were susceptible to ceftriaxone and azithromycin, 10.3% were penicillin G intermediate (range, 8% in 2008–16.7% in 2010), and <1% were ciprofloxacin, rifampin, or penicillin G resistant. Of the penicillin G intermediate or resistant isolates, 63% contained mutations in the penA gene associated with reduced susceptibility to penicillin G. All ciprofloxacin-resistant isolates contained mutations in the gyrA gene associated with reduced susceptibility.

Conclusions. Resistance of N meningitidis to antimicrobials used for empirical treatment of meningitis in the United States has not been detected, and resistance to penicillin G and chemoprophylaxis agents remains uncommon. Therapeutic agent recommendations remain valid. Although periodic surveillance is warranted to monitor trends in susceptibility, routine clinical testing may be of little use.

Nosocomial Infection Caused by Antibiotic-Resistant Organisms in the Intensive-Care Unit

Resistance to antimicrobial agents is an evolving process, driven by the selective pressure of heavy antibiotic use in individuals living in close proximity to others. The intensive care unit (ICU), crowded with debilitated patients who are receiving broad-spectrum antibiotics and being cared for by busy physicians, nurses, and technicians, serves as an ideal environment for the emergence of antibiotic resistance. Problem pathogens presently include multiply resistant gram-negative bacilli, methicillin-resistantStaphylococcus aureus, and the recently emerged vancomycin-resistant enterococci. The prevention of antimicrobial resistance in ICUs should focus on recognition via routine unit-based sur veillance, improved compliance with handwashing and barrier precautions, and antibiotic-use policies tailored to individual units within hospitals.

Practice patterns of infectious disease physicians for management of meningococcal disease

BACKGROUND

Although empiric treatment regimens for acute bacterial meningitis are well established, there are many uncertainties regarding management of meningococcal disease. A survey was conducted among infectious disease specialists to assess meningococcal disease practice patterns and availability of antimicrobial susceptibility testing for Neisseria menigitidis.

METHODS

An online survey was distributed to 1342 pediatric and adult infectious disease specialists to assess common practices and opinions regarding the diagnosis, treatment and prevention of meningococcal disease. Specialists were also asked about the availability of antimicrobial susceptibility testing for Neisseria meningitidis at their clinical microbiology laboratory.

RESULTS

Six hundred fifty members responded to the survey (48%). Pediatric infectious disease specialists were more likely than adult specialists to use penicillin as definitive therapy for meningococcal disease (56% versus 46%; P = 0.038). Most pediatric specialists who would narrow therapy report that they would only switch to penicillin upon confirmation of penicillin susceptibility (55%), although 44% would narrow therapy based on a N. meningitidis species confirmation alone. More than one third of respondents reported that susceptibility testing for N. meningitidis is not routinely performed. There was also wide variation in complement deficiency screening criteria and meningococcal disease chemoprophylaxis practices among respondents.

CONCLUSIONS

Infectious disease specialists vary significantly in their practices regarding several aspects of meningococcal disease diagnosis, treatment and prevention. Antimicrobial susceptibility testing for N. meningitidis is not routinely performed in many practices. Consideration of these variations would be useful when developing treatment and prevention recommendations.

Bacterial meningitis: epidemiology, pathogenesis and management update

Bacterial meningitis continues to be an important disease throughout the world and can be a life-threatening emergency if not suspected, appropriately diagnosed and managed expeditiously. The epidemiology of bacterial meningitis has changed dramatically over the last 20 years, primarily as a result of the introduction of conjugate vaccines against the common meningeal pathogens, such that in the developed world where vaccination is routinely utilized, bacterial meningitis has become a disease of adults rather than of infants and children. The management approach to patients with suspected or proven bacterial meningitis includes emergent cerebrospinal fluid analysis and initiation of appropriate antimicrobial and adjunctive therapies. The choice of empirical antimicrobial therapy is based on the patient's age and underlying disease status; once the infecting pathogen is isolated, antimicrobial therapy can be modified for optimal treatment. Many patients with suspected or proven bacterial meningitis should also receive adjunctive dexamethasone therapy. This is based on experimental animal model data which demonstrated that the subarachnoid space inflammatory response that results from antimicrobial-induced bacterial lysis can contribute to morbidity and mortality. Clinical studies have demonstrated the benefit of adjunctive dexamethasone in infants and children with Haemophilus influenzae type B meningitis, and adults with pneumococcal meningitis, in which mortality and adverse outcome are reduced. Use of adjunctive dexamethasone in adults with meningitis caused by other bacteria, and in infants and children with pneumococcal meningitis, is controversial. To be effective, adjunctive dexamethasone should be administered concomitant with or just prior to the first antimicrobial dose for maximal effect on the subarachnoid space inflammatory response.

Acute bacterial meningitis in infants and children

Bacterial meningitis continues to be an important cause of mortality and morbidity in neonates and children throughout the world. The introduction of the protein conjugate vaccines against Haemophilus influenzae type b, Streptococcus pneumoniae, and Neisseria meningitidis has changed the epidemiology of bacterial meningitis. Suspected bacterial meningitis is a medical emergency and needs empirical antimicrobial treatment without delay, but recognition of pathogens with increasing resistance to antimicrobial drugs is an important factor in the selection of empirical antimicrobial regimens. At present, strategies to prevent and treat bacterial meningitis are compromised by incomplete understanding of the pathogenesis. Further research on meningitis pathogenesis is thus needed. This Review summarises information on the epidemiology, pathogenesis, new diagnostic methods, empirical antimicrobial regimens, and adjunctive treatment of acute bacterial meningitis in infants and children.

Neisseria meningitidis intermediately resistant to penicillin and causing invasive disease in South Africa in 2001 to 2005

Neisseria meningitidis strains (meningococci) with decreased susceptibility to penicillin (MICs, >0.06 microg/ml) have been reported in several parts of the world, but the prevalence of such isolates in Africa is poorly described. Data from an active national laboratory-based surveillance program from January 2001 through December 2005 were analyzed. A total of 1,897 cases of invasive meningococcal disease were reported, with an average annual incidence of 0.83/100,000 population. Of these cases, 1,381 (73%) had viable isolates available for further testing; 87 (6%) of these isolates tested intermediately resistant to penicillin (Pen(i)). Pen(i) meningococcal isolates were distributed throughout all provinces and age groups, and there was no association with outcome or human immunodeficiency virus infection. The prevalence of Pen(i) was lower in serogroup A (7/295; 2%) than in serogroup B (24/314; 8%), serogroup C (9/117; 8%), serogroup Y (22/248; 9%), or serogroup W135 (25/396; 6%) (P = 0.02). Pulsed-field gel electrophoresis grouped 63/82 Pen(i) isolates into nine clusters, mostly according to serogroup. The clustering of patterns from Pen(i) isolates was not different from that of penicillin-susceptible isolates. Twelve sequence types were identified among 18 isolates arbitrarily selected for multilocus sequence typing. DNA sequence analysis of the penA gene identified 26 different alleles among the Pen(i) isolates. Intermediate penicillin resistance is thus widespread among meningococcal serogroups, has been selected in a variety of lineages, and, to date, does not appear to be associated with increased mortality. This is the first report describing the prevalence and molecular epidemiology of Pen(i) meningococcal isolates from sub-Saharan Africa.

Multilaboratory evaluation of disk diffusion antimicrobial susceptibility testing of Neisseria meningitidis isolates

In 2005, the Clinical and Laboratory Standards Institute published MIC interpretive criteria for 13 antimicrobial agents used for either therapy or prophylaxis of Neisseria meningitidis infections. The MIC method includes the use of lysed horse blood-supplemented Mueller-Hinton broth with incubation in 5% CO2 for 20 to 24 h. Since some clinical laboratories might prefer the option of disk diffusion testing for infrequently encountered isolates a multicenter collaborative study was conducted to evaluate the reproducibility of a disk diffusion method for testing isolates of N. meningitidis. Interpretive criteria were developed for 12 antimicrobial agents. Four laboratories tested a common collection of 50 meningococcal strains and then tested 25 unique isolates per laboratory. Isolates were tested using Mueller-Hinton sheep blood agar plates incubated for 20 to 24 h in 5% CO2; they were also tested by the reference broth microdilution method in parallel. Pooling of the MIC and disk diffusion data from the common and unique isolates provided a sufficient sample size to develop susceptible, intermediate, and resistant zone diameter interpretive criteria using the error rate-bounded method for the following agents: chloramphenicol, trimethoprim-sulfamethoxazole, ciprofloxacin, and rifampin. Due to the lack of resistant strains at the present time, "susceptible only" interpretive criteria were proposed for cefotaxime, ceftriaxone, meropenem, azithromycin, and minocycline. The numbers of minor interpretive errors with penicillin and ampicillin disk tests were unacceptably high and precluded recommended testing of those agents by the disk method. However, amdinocillin, an agent that preferentially binds to the altered penicillin binding protein responsible for diminished penicillin susceptibility, has potential utility as a surrogate screening reagent for ampicillin resistance. A disk diffusion breakpoint was derived for nalidixic acid to serve as a surrogate marker for gyrase A mutations associated with diminished fluoroquinolone susceptibility. Disk diffusion testing with meningococci can be performed in a reproducible manner with several antimicrobial agents and represents a practical and cost-effective option for testing sporadic clinical isolates or for surveillance purposes by resource-limited laboratories.

Pneumonia and empyema caused by penicillin-resistant Neisseria meningitidis: a case report and literature review

Pneumonia is an uncommon manifestation of Neisseria meningitidis infection, and empyema is rarely reported. Uniform penicillin susceptibility has been assumed for meningococcal infections for many years, but decreased penicillin susceptibility has been recognized recently with increasing frequency. Breakpoints to define different categories of susceptibility were published recently by the Clinical and Laboratory Standards Institute. We report the case of a teenage girl with sepsis and extensive bilateral pneumonia with empyema caused by an N meningitidis isolate that was resistant to penicillin. Her protracted clinical course suggested that penicillin resistance contributed to her delayed recovery. Our experience with this patient suggests that susceptibility testing should be performed in every case of N meningitidis isolation, and treatment with a third-generation cephalosporin should be provided until the susceptibility results are known. Clinical suspicion of N meningitidis as a possible cause of respiratory symptoms accompanied by hypotension, even in the absence of a rash, may aid in diagnosis and therefore in the treatment and provision of prophylaxis to contacts of patients with meningococcal disease.

Prospects for vaccine prevention of meningococcal infection

Neisseria meningitidis is the leading cause of bacterial meningitis in the United States and worldwide. A serogroup A/C/W-135/Y polysaccharide meningococcal vaccine has been licensed in the United States since 1981 but has not been used universally outside of the military. On 14 January 2005, a polysaccharide conjugate vaccine that covers meningococcal serogroups A, C, W-135, and Y was licensed in the United States for 11- to 55-year-olds and is now recommended for the routine immunization of adolescents and other high-risk groups. This review covers the changing epidemiology of meningococcal disease in the United States, issues related to vaccine prevention, and recommendations on the use of the new vaccine.

Three days of intravenous benzyl penicillin treatment of meningococcal disease in adults

New Zealand has experienced an epidemic of predominantly serogroup B meningococcal disease during the past decade. In a prospective study, we treated adults (age, >15 years) with meningococcal disease with intravenous benzyl penicillin (12 MU [7.2 g] per day) for 3 days. Sixty-one adults with suspected meningococcal disease were consecutively admitted during the 33-month period; 3 patients were excluded. The 58 patients had a mean age (+/- standard deviation [SD]) of 27.9+/-14.5 years (median, 21 years; range, 15-70 years). Forty-four patients had confirmed and 14 patients had probable meningococcal disease. Fifty-seven patients received 12 MU (7.2 g) and 1 received 8 MU (4.8 g) of benzyl penicillin per day. Thirteen patients received additional antibiotics within the first 24 h because of diagnostic uncertainties. Patients received a mean (+/-SD) of 3.0+/-0.5 days of treatment. No patients relapsed. Five patients died. All but 1 death occurred during benzyl penicillin treatment, and the only posttreatment death was not due to meningococcal disease. Three days of intravenous benzyl penicillin is sufficient treatment for adults with meningococcal disease. The usual recommendations for duration of treatment are excessive.

Meningococcal vaccines: a progress report

Neisseria meningitidis causes a wide range of human disease and remains a common cause of septicaemia and meningitis. Meningococcal serogroups A, B, C and Y cause the majority of cases of invasive disease in the US and throughout the world, with epidemics usually caused by serogroups A and C. Most patients with meningococcaemia, with or without meningitis, respond to standard antimicrobial therapy with either penicillin or ampicillin, but the recent emergence of meningococcal strains that are intermediately resistant to penicillin may alter these recommendations in the future. Given the devastating nature of meningococcal disease and emergence of these resistant strains, prevention (specifically through vaccination) remains the best approach to control this serious infection. A polysaccharide meningococcal vaccine is efficacious against disease caused by serogroups A, C, Y and W135, but is not effective in infants and children aged <2 years, and the duration of efficacy decreases markedly during the first 3 years after a single dose of the vaccine. Conjugate meningococcal vaccines have been developed to address these concerns. Initial studies with the meningococcal C conjugate vaccine have shown that the vaccine is safe and immunogenic and provides a T cell-dependent antigen that can be boosted by further doses of vaccine, or following exposure to the homologous organism or cross-reacting antigens. The UK recently implemented routine vaccination with the meningococcal C conjugate vaccine to all infants, and to all persons aged >1 year in a catch-up programme to immunise all school-aged children and young adults up to 20 years of age. Early postlicensure data indicate that this vaccine has shown significant efficacy in reduction of invasive meningococcal disease in these age groups. The full impact of vaccination will be determined once all age groups are immunised.

Fatal outcome from meningococcal disease--an association with meningococcal phenotype but not with reduced susceptibility to benzylpenicillin

Penicillin has been the mainstay of treatment for meningococcal disease. Isolates of Neisseria meningitidis that are less susceptible to penicillin have been reported in several countries and in recent years have become more common. The clinical significance of this reduced susceptibility has not been investigated on a large scale. Hence, N. meningitidis isolates from culture-confirmed cases of meningococcal disease in England and Wales, between 1993 and 2000, were routinely serogrouped, serotyped and tested for susceptibility to penicillin. These data were linked to death registrations and analysed retrospectively. The changing trends in susceptibility were described and multivariate logistic regression was used to examine associations between strain characteristics and fatal outcome. The frequency of N. meningitidis isolates less susceptible to penicillin increased from < 6% in 1993 to > 18% in 2000. In particular, isolates expressing serogroup C with serotype 2b and serogroup W135 had a higher frequency of reduced penicillin susceptibility (49% and 55%, respectively). There was no evidence of an association between fatal outcome and infection with a less penicillin-susceptible isolate. Fatal outcome was associated with serogroup and serotype, with the odds of death for cases infected with C:2a and B:2a strains three-fold higher when compared with the baseline. For this large dataset the serogroup and serotype of the infecting strain influenced mortality from meningococcal disease and may be markers for hypervirulence. No association was found between reduced penicillin susceptibility and fatal outcome, but the increasing frequency of isolates less susceptible to penicillin highlights the need for continued surveillance.

Neisseria meningitidis with decreased susceptibility to penicillin in Istanbul, Turkey

This study was conducted to estimate the rate of decreased susceptibility to penicillin (MIC > 0.06-1 microg/ml) in Neisseria meningitidis isolates in Istanbul, Turkey. A total of 30 isolates collected during a 1-y period from patients with meningitis and from nasopharyngeal carriers were tested for penicillin and cefotaxime susceptibility using the E-test. Two out of 12 (17%) clinical isolates and 11/18 (61%) nasopharyngeal isolates showed decreased susceptibility to penicillin with MICs in the range 0.094-1.0 microg/ml, giving an overall resistance of 43% (n = 13). These data show that continued surveillance of trends in antimicrobial susceptibility of N. meningitidis is important for detecting the emergence of N. meningitidis strains with MICs > 1 microg/ml which may pose serious therapeutic problems.

Treatment of Bacterial Meningitis

The therapeutic approach to acute bacterial meningitis has changed in recent years as a result of changes in in vitro susceptibility of many meningeal pathogens to previously standard antimicrobial therapy. Given the emergence of strains of Streptococcus pneumoniae that are resistant to penicillin and the cephalosporins, the combination of vancomycin plus a third-generation cephalosporin is recommended as empiric therapy for suspected or proven pneumococcal meningitis, pending results of in vitro susceptibility testing. Strains of Neisseria meningitidis with reduced susceptibility to penicillin have also been described, although most patients with these resistant strains have recovered with standard penicillin therapy. Although the third-generation cephalosporins have greatly improved outcome in patients with meningitis caused by aerobic gram-negative bacilli, many organisms in this group are now resistant to these drugs; the carbapenems and fluoroquinolones may be effective alternative agents and have been successfully used in small case series. Further surveillance of the in vitro antimicrobial susceptibility patterns of meningeal pathogens is critical for future recommendations in the treatment of bacterial meningitis.

Neisseria meningitidis with decreased susceptibility to penicillin: report from the SENTRY antimicrobial surveillance program, North America, 1998-99

The purpose of this study was to estimate the prevalence of Neisseria meningitidis with decreased susceptibility to penicillin (MIC, >0.06 microg/mL) in North America (NA). Antimicrobial susceptibility testing by Etest (AB BIODISK, Solna, Sweden) was performed on 53 invasive clinical isolates obtained from 11 SENTRY Antimicrobial Surveillance Program participants in NA (9 states, 2 provinces) during 1998-99. All strains were markedly susceptible to ciprofloxacin (MIC(90), 0.008 microg/mL) and cefotaxime (MIC(90), < or = 0.002 microg/mL). Only 54.7% were susceptible to trimethoprim-sulfamethoxazole (TMP/SMX) at < or = 0.5/9.5 microg/mL. One strain was resistant to rifampin (MIC, > 32 microg/mL) and 16 isolates (30.2%) were relatively resistant to penicillin with MICs ranging from 0.094 to 0.25 microg/mL. No beta-lactamase production was detected. The serogroup distribution was 40% Y, 28% B, 24% C, 2% W-135, and 6% of strains were nongroupable. The prevalence of N. meningitidis with decreased susceptibility to penicillin in NA appears higher than previous reports.

Antibacterial agents in infections of the central nervous system

Experimental animal models have provided information applicable to antimicrobial therapy of infections of the central nervous system. The efficacy of an antimicrobial agent in the therapy of bacterial meningitis depends on its ability to penetrate the blood-brain barrier, its activity in purulent cerebrospinal fluid, and a demonstration of rapid bactericidal activity against the offending pathogen. The recent emergence of resistant pathogens is challenging the therapy for bacterial meningitis. Various strategies for treating resistant pathogens have been evaluated in experimental animal models. Encouraging results have led to clinical trials to evaluate the efficacy of newer agents, alone or in combination with standard regimens.

Update on meningococcal disease with emphasis on pathogenesis and clinical management

The only natural reservoir of Neisseria meningitidis is the human nasopharyngeal mucosa. Depending on age, climate, country, socioeconomic status, and other factors, approximately 10% of the human population harbors meningococci in the nose. However, invasive disease is relatively rare, as it occurs only when the following conditions are fulfilled: (i) contact with a virulent strain, (ii) colonization by that strain, (iii) penetration of the bacterium through the mucosa, and (iv) survival and eventually outgrowth of the meningococcus in the bloodstream. When the meningococcus has reached the bloodstream and specific antibodies are absent, as is the case for young children or after introduction of a new strain in a population, the ultimate outgrowth depends on the efficacy of the innate immune response. Massive outgrowth leads within 12 h to fulminant meningococcal sepsis (FMS), characterized by high intravascular concentrations of endotoxin that set free high concentrations of proinflammatory mediators. These mediators belonging to the complement system, the contact system, the fibrinolytic system, and the cytokine system induce shock and diffuse intravascular coagulation. FMS can be fatal within 24 h, often before signs of meningitis have developed. In spite of the increasing possibilities for treatment in intensive care units, the mortality rate of FMS is still 30%. When the outgrowth of meningococci in the bloodstream is impeded, seeding of bacteria in the subarachnoidal compartment may lead to overt meningitis within 24 to 36 h. With appropriate antibiotics and good clinical surveillance, the mortality rate of this form of invasive disease is 1 to 2%. The overall mortality rate of meningococcal disease can only be reduced when patients without meningitis, i.e., those who may develop FMS, are recognized early. This means that the fundamental nature of the disease as a meningococcus septicemia deserves more attention.

Update on meningococcal disease with emphasis on pathogenesis and clinical management

The only natural reservoir of Neisseria meningitidis is the human nasopharyngeal mucosa. Depending on age, climate, country, socioeconomic status, and other factors, approximately 10% of the human population harbors meningococci in the nose. However, invasive disease is relatively rare, as it occurs only when the following conditions are fulfilled: (i) contact with a virulent strain, (ii) colonization by that strain, (iii) penetration of the bacterium through the mucosa, and (iv) survival and eventually outgrowth of the meningococcus in the bloodstream. When the meningococcus has reached the bloodstream and specific antibodies are absent, as is the case for young children or after introduction of a new strain in a population, the ultimate outgrowth depends on the efficacy of the innate immune response. Massive outgrowth leads within 12 h to fulminant meningococcal sepsis (FMS), characterized by high intravascular concentrations of endotoxin that set free high concentrations of proinflammatory mediators. These mediators belonging to the complement system, the contact system, the fibrinolytic system, and the cytokine system induce shock and diffuse intravascular coagulation. FMS can be fatal within 24 h, often before signs of meningitis have developed. In spite of the increasing possibilities for treatment in intensive care units, the mortality rate of FMS is still 30%. When the outgrowth of meningococci in the bloodstream is impeded, seeding of bacteria in the subarachnoidal compartment may lead to overt meningitis within 24 to 36 h. With appropriate antibiotics and good clinical surveillance, the mortality rate of this form of invasive disease is 1 to 2%. The overall mortality rate of meningococcal disease can only be reduced when patients without meningitis, i.e., those who may develop FMS, are recognized early. This means that the fundamental nature of the disease as a meningococcus septicemia deserves more attention.

Meningococcal pneumonia: characterization and review of cases seen over the past 25 years

Fifty-eight cases of meningococcal pneumonia were included in this review. Fifty cases previously described in the literature from 1974 through 1998 and 8 new cases were included in this series. The median age of patients was 57.5 years, and pleuritic chest pain was described in 21 (53.9%) of 39 cases. Blood cultures were positive in 42 (79.3%) of 53 cases for which results were mentioned. Despite the presence of bacteremia, patients did not develop the syndrome of meningococcemia with its associated complications. Serogroup Y meningococci were most commonly recovered and accounted for 44.2% of identified isolates. Therapy has dramatically changed over the past 25 years; prior to 1991, penicillin antibiotics were most often used. Since 1991, 12 (80%) of 15 patients received cephalosporin antibiotics. Only 5 (8.62%) of 58 patients died. Secondary cases of meningococcal infections following exposure to patients with meningococcal pneumonia were noted in 2 instances.

Bacterial resistance and antibiotic use in the emergency department

Antibiotic resistance among bacteria that are commonly encountered in the pediatric emergency department is a fact of nature. New antibiotics will provide some help, but probably only temporarily. Vaccine strategies seem to provide the best answer to resistance, and many physicians eagerly await the conjugated pneumococcal vaccines, which we can only hope to be as successful as the H. influenzae type b vaccines. Vaccines against other resistant organisms are likely further off. At this point, a major goal must be to limit the prevalence of antibiotic resistance. In considering this goal, two complementary strategies are key. The first is to avoid antibiotics in situations in which they are unlikely to provide benefit, such as for colds, URIs, and bronchitis. The second is to use narrow-spectrum antibiotics as much as possible to minimize selective pressure. Emerging evidence shows that these strategies can be effective. In a day-care center in Omaha, Nebraska, Boken et al showed that nasopharyngeal carriage of highly resistant S. pneumoniae decreased dramatically among attendees when antibiotic use decreased. In Iceland, a nationwide campaign that resulted in decreased antibiotic use was followed by a decrease in the incidence of penicillin-resistant pneumococcal infections from 20.0% to 16.9% and a decrease in the rate of carriage of resistant pneumococci among day-care-center attendees from 49% to 15%. In Finland, erythromycin resistance in Group A streptococci recovered from pharyngeal and pus samples had reached 13% in 1990. National guidelines that recommended a reduction in the use of erythromycin and other macrolide antibiotics in the treatment of outpatients with respiratory and skin infections were instituted, and by 1996, macrolide antibiotic consumption had decreased by 50%, with a similar 50% decrease in frequency of erythromycin-resistant isolates. In the absence of such national strategies, it is incumbent on physicians treating infections on a daily basis in the emergency department to consider carefully the judicious use of antibiotics.

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.

Frontiers of occupational health. New vaccines, new prophylactic regimens, and management of the HIV-infected worker

New prophylactic or treatment options are available for a number of infectious diseases that may be transmitted in the health care setting. Infectious diseases that can now be prevented by vaccination of the employee include hepatitis A, pertussis, hepatitis B, and primary varicella. New prophylactic or treatment regimens are available for Neisseria meningitidis, Streptococcus pyogenes, and Bordetella pertussis; treatment of multidrug-resistant tuberculosis is also discussed. Finally, management of the HIV-infected health care worker is reviewed.

Pattern of bacterial meningitis in Italy, 1994

During 1994, 603 cases of bacterial meningitis were reported in Italy. Seventy-five percent of cases with determined etiology was due to three agents: Neisseria meningitidis (33.4%), Streptococcus pneumoniae (23.4%) and Haemophilus influenzae (18.6%). The majority of cases due to N. meningitidis and H. influenzae occurred in subjects below five years of age (35.7% and 84.8%, respectively) while S. pneumoniae accounted for 52.8% of meningitis cases in subjects older than 44 year of age. The estimated incidence of N. meningitidis on the national population in 1994 was 0.27 per 100,000. Serogroup B accounted for 62.5% of the serotyped isolates, group C for 23.1%, group A for 7.2%, group W135 for 3.6%, group Y for 1.8%. All tested meningococcal strains were susceptible to penicillin as well as to rifampin. Incidence of meningococcal meningitis in 1994 has been low suggesting that its relative importance compared to other bacteria causing meningitis is likely to change in the future. Therefore, extended surveillance on bacterial meningitis by other etiological agents has to be maintained and implemented in order to undertake the appropriate control measures and evaluate their effect.

Comparative evaluation of etest for susceptibility testing Neisseria meningitidis with eight antimicrobial agents. An investigation using U.S. Food and Drug Administration regulatory criteria

Invasive infections caused by Neisseria meningitidis continue to be a serious clinical problem for therapy, epidemiology, and potential prophylaxis. Multiple antimicrobial resistances have emerged among meningococcal strains including elevated MICs to penicillin, sulfonamides, tetracyclines, and rifampin. Thus, the need to perform accurate susceptibility testing of meningococci in clinical practice and for surveillance programs has renewed priority. In this study, for the first time Etest (AB Biodisk, Solna, Sweden) was compared to a reference agar dilution method using a large number (100) of clinical strains selected for a range of drug resistances. Etest quantitative accuracy (+/-one log2 dilution agreement) ranged from 94% (penicillin) to 100% (three drugs) for the eight clinically useful antimicrobial agents tested. Intermethod categorical accuracy for all drug ranged from 92% (penicillin, erythromycin) to 100% (five drugs), without false-susceptible or -resistant errors using Etest. Etest and reference methods were highly reproducible (99.6 to 100.0%, respectively). Quantitative discords between methods (> or = two log2 dilutions) were not reproducible and resolved following repeated testing. Etest method proved to be an accurate and reproducible quantitative method for testing N. meningitidis strains for the compared antimicrobial agents (eight) often utilized for therapy and prophylaxis of serious meningococcal disease.

Meningococcemia

Meningococcal infection is a contagious disease that is spread via the respiratory route through pharyngeal secretions. Clinical manifestations range from occult bacteremia to overwhelming septicemia or meningitis. Skin manifestations often develop and may be the first sign that leads to clinical suspicion of meningococcemia. Treatment consists of antibiotic therapy and supportive care, which may include aggressive fluid resuscitation, oxygen, ventilatory support, and inotropic support. The use of chemoprophylaxis and in certain circumstances vaccination are important in preventing secondary cases of meningococcal disease.

Comparison of broth microdilution and E-test for susceptibility testing of Neisseria meningitidis

The susceptibilities of 54 clinical isolates of Neisseria meningitidis to penicillin, cefotaxime, ceftriaxone, cefepime, imipenem, ciprofloxacin, chloramphenicol, and rifampin were determined by the microdilution method in both cation-adjusted Mueller-Hinton broth (CAMHB) and Haemophilus test medium (HTM). Poor growth was observed in 16.6 and 9% of the strains in CAMHB and HTM, respectively. As a result, the growth of the 54 N. meningitidis strains was evaluated in three other commercially available batches of CAMHB and in one in-house batch of HTM. Poor growth was observed for 9.3 to 16.6% of the strains in all four batches. More important, three of the CAMHB batches failed to support growth for 3.7 to 33.3% of the strains; 3.7% of the strains did not grow in the in-house-prepared HTM. Ten (18.7%) strains were relatively resistant to penicillin (RRP; MIC, > 0.125 mu g/ml) in CAMHB and 13 (24%) strains were RRP in HTM. The percentages of agreement obtained by using CAMHB as the reference ranged from 78% for cefepime to 100% for ceftriaxone. Seven minor errors were observed for penicillin; five of them were for strains susceptible to penicillin in CAMHB and RRP in HTM. All strains were susceptible to the other antimicrobial agents evaluated. The growth of N. meningitidis was also evaluated in four batches of Mueller-Hinton agar (MHA). In two of them, 3.7 and 44.4% of the strains did not grow, and considering all four batches, 5.5 to 11.1% grew poorly. All strains grew adequately in MHA supplemented with blood (MHA-b). The activities of penicillin and cefotaxime were also evaluated by the E-test in MHA and MHA-b. The proportion of RRP strains were 24% in MHA and 59% in MHA-b. For penicillin, the percentages of agreement of the E-test with the microdilution method in CAMHB (reference) were 64.8 and 70.3% in MHA and MHA-b, respectively. For cefotaxime, the agreement was 98.1%. Minor errors for the penicillin MIC were detected for 38% of the strains tested. Further studies are needed to define adequate culture media for reference methods to evaluate the susceptibility of N. meningitidis to antimicrobial agents.

In vitro activities of ciprofloxacin, cefotaxime, ceftriaxone, chloramphenicol, and rifampin against fully susceptible and moderately penicillin-resistant Neisseria meningitidis

Moderately penicillin-resistant Neisseria meningitidis was responsible for an outbreak of meningococcal disease in Saskatoon, Saskatchewan, Canada in 1993. We tested fully susceptible and moderately resistant strains of N. meningitidis against ciprofloxacin, cefotaxime, ceftriaxone, chloramphenicol, penicillin, and rifampin. Eighteen percent of the isolates were moderately resistant to penicillin (MIC > or = 0.06 microgram/ml) whereas susceptibility was 100% for the other agents tested.

Antibody responses to the capsular polysaccharide of Neisseria meningitidis serogroup B in patients with meningococcal disease

We measured antibody responses to meningococcal serogroup B (MenB) polysaccharide (PS) by enzyme-linked immunosorbent assay (ELISA) in sera from 94 patients from The Netherlands with disease caused by Neisseria meningitidis group B. The patients ranged in age from 3 to 73 years (mean age, 18.8 years). In initial studies we showed that the binding of a panel of MenB PS-reactive human immunoglobulin M (IgM) paraproteins to biotinylated MenB PS bound to avidin-coated microtiter wells was inhibited > 90% by the addition of soluble MenB PS or encapsulated group B meningococci. In contrast, inhibition of IgM anti-MenB PS antibody-binding activity in many of the patient sera was less than 50% (range, 20 to 94%). These data suggested a high frequency of nonspecific binding in the patient sera. Therefore, all serum samples were assayed in replicate in the presence or absence of soluble MenB PS, and only the inhibitable fraction of the binding signal was used to calculate the anti-MenB PS antibody concentrations. In 17 control patients with meningococcal disease caused by serogroup A or C strains, there was no significant difference in the respective IgM or IgG anti-MenB PS antibody concentrations in paired acute- and convalescent-phase sera. In contrast, in patients with MenB disease, the geometric mean IgM anti-MenB PS antibody concentration increased from 3.9 units/ml in acute-phase serum to 10.5 units/ml in convalescent-phase serum (P < 0.001). The corresponding geometric mean IgG anti-MenB PS antibody titers were 1:27 and 1:36 (P < 0.05). There was only a weak relationship between age and the magnitude of the logarithm of the antibody concentrations in convalescent-phase sera (for IgM, r2 = 0.06 and P < 0.05; for IgG, r2 = 0.08 and P < 0.01). Our data indicate that precautions are needed to avoid nonspecificity in measuring serum antibody responses to MenB PS by ELISA. Furthermore, although this PS is thought to be a poor immunogen, patients as young as 3 years of age recovering from MenB disease demonstrate both ImG and IgG antibody responses in serum.

Neisseria meningitidis with decreased susceptibility to penicillin in Saskatchewan, Canada

Moderately penicillin-resistant Neisseria meningitidis is rare in North America. We report an outbreak of meningococcal disease in Saskatoon, Saskatchewan, Canada, with serogroup C N. meningitidis. The MICs of penicillin ranged from 0.12 to 0.25 micrograms/ml, and all isolates showing decreased susceptibility had identical genomic fingerprints when they were compared by pulsed-field gel electrophoresis. Our data indicate that N. meningitidis that is moderately resistant to penicillin is prevalent in Saskatchewan, Canada.