Staphylococcus aureus meningitis in adults: A comparative cohort study of infections caused by meticillin-resistant and meticillin-susceptible strains

BACKGROUND

Staphylococcus aureus meningitis is an uncommon nosocomial infection usually associated with neurosurgical procedures, but spontaneous infections may occasionally appear.

AIMS

To compare the features of meningitis caused by meticillin-resistant (MRSA) and meticillin-susceptible (MSSA) S. aureus and examine the prognostic factors for mortality, including MRSA infection and combined antimicrobial therapy.

METHODS

Retrospective cohort study of 350 adults with S. aureus meningitis admitted to 11 hospitals in Spain (1981-2015). Logistic regression and propensity score matching were used to analyse prognostic factors.

RESULTS

There were 118 patients (34%) with MRSA and 232 (66%) with MSSA. Postoperative infection (91% vs 73%) and nosocomial acquisition (93% vs 74%) were significantly more frequent in MRSA than in MSSA meningitis (P < 0.001). Combined therapy was given to 118 (34%) patients. Overall 30-day mortality rate was 23%. On multivariate analysis, mortality was associated with severe sepsis or shock (odds ratio (OR) 9.9, 95% confidence interval (CI) 4.5-22.0, P < 0.001), spontaneous meningitis (OR 4.2, 95% CI 1.9-9.1, P < 0.001), McCabe-Jackson score rapidly or ultimately fatal (OR 2.8, 95% CI 1.4-5.4, P = 0.002), MRSA infection (OR 2.6, 95% CI 1.3-5.3, P = 0.006), and coma (OR 2.6, 95% CI 1.1-6.1, P < 0.029). In postoperative cases, mortality was related to retention of cerebrospinal devices (OR 7.9, 95% CI 3.1-20.3, P < 0.001).

CONCLUSIONS

Clinical and epidemiological differences between MRSA and MSSA meningitis may be explained by the different pathogenesis of postoperative and spontaneous infection. In addition to the severity of meningitis and underlying diseases, MRSA infection was associated with increased mortality. Combined antimicrobial therapy was not associated with increased survival.

Safe Reduction in CD4 Cell Count Monitoring in Stable, Virally Suppressed Patients With HIV Infection or HIV/Hepatitis C Virus Coinfection

BACKGROUND

It has been suggested that routine CD4 cell count monitoring in human immunodeficiency virus (HIV)-monoinfected patients with suppressed viral loads and CD4 cell counts >300 cell/μL could be reduced to annual. HIV/hepatitis C virus (HCV) coinfection is frequent, but evidence supporting similar reductions in CD4 cell count monitoring is lacking for this population. We determined whether CD4 cell count monitoring could be reduced in monoinfected and coinfected patients by estimating the probability of maintaining CD4 cell counts ≥200 cells/µL during continuous HIV suppression.

METHODS

The PISCIS Cohort study included data from 14 539 patients aged ≥16 years from 10 hospitals in Catalonia and 2 in the Balearic Islands (Spain) since January 1998. All patients who had at least one period of 6 months of continuous HIV suppression were included in this analysis. Cumulative probabilities with 95% confidence intervals were calculated using the Kaplan-Meier estimator stratified by the initial CD4 cell count at the period of continuous suppression initiation.

RESULTS

A total of 8695 patients were included. CD4 cell counts fell to <200 cells/µL in 7.4% patients, and the proportion was lower in patients with an initial count >350 cells/µL (1.8%) and higher in those with an initial count of 200-249 cells/µL (23.1%). CD4 cell counts fell to <200 cells/µL in 5.7% of monoinfected and 11.1% of coinfected patients. Of monoinfected patients with an initial CD4 cell count of 300-349 cells/µL, 95.6% maintained counts ≥200 cells/µL. In the coinfected group with the same initial count, this rate was lower, but 97.6% of coinfected patients with initial counts >350 cells/µL maintained counts ≥200 cells/µL.

CONCLUSIONS

From our data, it can be inferred that CD4 cell count monitoring can be safely performed annually in HIV-monoinfected patients with CD4 cell counts >300 cells/µL and HIV/HCV-coinfected patients with counts >350 cells/µL.

Experimental study of cerebrospinal fluid tumor necrosis factor-alpha release in penicillin- and cephalosporin-resistant pneumococcal meningitis treated with different antibiotic schedules

BACKGROUND/PURPOSE

To measure the inflammatory response in terms of tumor necrosis factor-alpha (TNF-α) levels in cerebrospinal fluid (CSF), using bacteriolytic versus nonbacteriolytic antibiotic therapy and adjunctive treatment with dexamethasone in an experimental rabbit model of pneumococcal meningitis.

METHODS

In a rabbit model of pneumococcal meningitis, we tested CSF TNF-α levels in several samples from rabbits infected with the HUB 2349 strain and treated with ceftriaxone 100 mg/kg/d, ceftriaxone plus vancomycin 30 mg/kg/d, or daptomycin at 15 mg/kg or 25 mg/kg. Daptomycin schedules were compared with the same doses in combination with dexamethasone at 0.125 mg/kg every 12 hours over a 26-hour period.

RESULTS

The ceftriaxone group had the highest levels of TNF-α. TNF-α levels were significantly higher after ceftriaxone administration than in both daptomycin groups. The high-dose daptomycin group presented the lowest inflammatory levels in CSF samples. Adjunctive treatment with dexamethasone in this group modulated the inflammatory response, bringing down CSF TNF-α levels.

CONCLUSION

CSF TNF-α levels were significantly lower in rabbits treated with daptomycin than in rabbits treated with ceftriaxone. Daptomycin avoided the inflammatory peak after administration observed in ceftriaxone-treated rabbits. The use of daptomycin plus dexamethasone achieved a significantly larger reduction in CSF TNF-α levels.

Effect of dexamethasone on the efficacy of daptomycin in the therapy of experimental pneumococcal meningitis

This study aimed to determine the effect of dexamethasone in combination with low-dose or high-dose daptomycin for the treatment of penicillin- and cephalosporin-resistant pneumococcal meningitis. Efficacy (ΔCFU/mL) and cerebrospinal fluid (CSF) levels of daptomycin at 15mg/kg and 25mg/kg were studied in a rabbit model of pneumococcal meningitis, comparing them with the same doses in combination with dexamethasone at 0.125mg/kg every 12h over a 26-h period against two different Streptococcus pneumoniae strains, HUB 2349 and ATCC 51916 with daptomycin minimum inhibitory concentrations (MICs) of 0.09mg/L and 0.19mg/L, respectively. Daptomycin levels in CSF were lower when dexamethasone was given concurrently. Against strain HUB 2349, therapeutic failure occurred with daptomycin 15mg/kg+dexamethasone; daptomycin 25mg/kg+dexamethasone was better at reducing bacterial counts than the lower dose throughout treatment. Against the highly cephalosporin-resistant ATCC 51916 strain, daptomycin 15mg/kg+dexamethasone achieved a lower bacterial decrease than daptomycin 15mg/kg alone, and therapeutic failure at 24h occurred in the daptomycin 15mg/kg+dexamethasone group. Addition of dexamethasone to a 25mg/kg daptomycin dose did not affect the efficacy of daptomycin: it remained bactericidal throughout treatment. In conclusion, against the studied strains, low-dose (15mg/kg/day) daptomycin is affected by concomitant use of dexamethasone: CSF levels are reduced and its bacterial efficacy is affected. At a higher daptomycin dose (25mg/kg/day), however, the use of dexamethasone does not alter efficacy; the combination appears to be a good choice for the treatment of pneumococcal meningitis.

Disseminated adiaspiromycosis: case report of a liver transplant patient with human immunodeficiency infection, and literature review

Disseminated adiaspiromycosis is a rare infection that is sometimes associated with immunocompromised situations. We report the case of a patient, infected with human immunodeficiency virus and receiving highly active antiretroviral therapy, who had a liver transplant for hepatocellular carcinoma. The patient presented skin and pulmonary lesions due to adiaspiromycosis during immunosuppressive therapy. A review of >60 cases in the literature shows that adiaspiromycosis is a rare infection and Emmonsia is a dimorphic fungus that is difficult to grow. It should be considered a possible diagnosis in case of fungal infection and pulmonary granulomatosis. We should be aware of emerging adiaspiromycosis in patients with risk factors of immunosuppression, particularly transplant recipients. In these patients in particular, liposomal amphotericin B therapy should be considered.

Efficacy of fosfomycin and its combination with linezolid, vancomycin and imipenem in an experimental peritonitis model caused by a Staphylococcus aureus strain with reduced susceptibility to vancomycin

The objective of this study was to evaluate the in vitro and in vivo efficacies of therapies including fosfomycin against clinical Staphylococcus aureus isolates with reduced susceptibility to vancomycin (hGISA). Time-kill curves were performed over 24 h. Peritonitis in C57BL/6 mice was induced by intraperitoneal inoculation of 10(8) CFU/ml. Four hours later (0 h), therapy was started and the treatment groups were: control (not treated), fosfomycin (100 mg/kg/5 h), vancomycin (60 mg/kg/5 h), imipenem (30 mg/kg/5 h), fosfomycin plus linezolid, fosfomycin plus vancomycin and fosfomycin plus imipenem, receiving subcutaneous therapy over 25 h. Bacterial counts in peritoneal fluid, bacteraemia and mortality rates were determined. In vitro, fosfomycin showed a synergistic effect when combined with the other antimicrobials tested. In the animal model, fosfomycin combinations were effective and significantly reduced the bacteraemia rates achieved in the control, imipenem and vancomycin groups (p < 0.05). The best combination in vivo was fosfomycin plus imipenem. Also, fosfomycin plus linezolid was significantly better than vancomycin alone, reducing the bacterial concentration in the peritoneal fluid. In conclusion, in vitro and in vivo, fosfomycin in combination with linezolid, vancomycin or imipenem exerted a good activity. Fosfomycin plus imipenem was the most active combination, decreasing 3 log CFU/ml, and appears to be a promising combination for clinical practice.

Community-acquired bacterial meningitis in cirrhotic patients

The Hospital Universitari de Bellvitge (Barcelona, Spain) records all cases of bacterial meningitis in a 120-variable database. The characteristics of bacterial meningitis in cirrhotic patients are not well-known, and all cases of community-acquired bacterial meningitis occurring in cirrhotic patients were therefore identified. During 1977-2002, there were 602 episodes of community-acquired bacterial meningitis in adults, of which 29 (4.8%) occurred in cirrhotic patients. Compared to non-cirrhotic patients, there were significant differences in: duration of disease for >4 days at the time of diagnosis; absence of nuchal rigidity; certain aetiologies, e.g., Escherichia coli and Listeria monocytogenes; renal and liver function impairment; relapse of fever; and incidence of relapse and mortality. Overall, bacterial meningitis in cirrhotic patients was associated with a high mortality rate and a large number of complications. A high index of suspicion is necessary because of the frequent absence of meningeal signs. In addition to the classic meningeal pathogens, other aetiologies, including E. coli and L. monocytogenes, should be considered when prescribing empirical therapy.

Efficacy of high doses of levofloxacin in experimental foreign-body infection by methicillin-susceptible Staphylococcus aureus

Antimicrobial efficacy in orthopedic device infections is diminished because of bacterial biofilms which express tolerance to antibiotics. Recently, the use of high doses of levofloxacin with rifampin has been recommended for staphylococcal infections. In the present study, we evaluated the efficacy of levofloxacin at doses of 50 mg/kg/day and 100 mg/kg/day (mimicking the usual and high human doses of 500 mg/day and 750 to 1,000 mg/day, respectively) and compared it to that of to linezolid, cloxacillin, vancomycin, and rifampin in a rat tissue cage model of experimental foreign-body infection by Staphylococcus aureus. The antimicrobial efficacy in vitro (by MIC, minimum bactericidal concentration, and kill curves) for logarithmic- and stationary-phase bacteria was compared with the in vivo efficacy. In vitro bactericidal activity at clinically relevant concentrations was reached by all drugs except rifampin and linezolid in the log-phase studies but only by levofloxacin in the stationary-phase studies. The bacterial count decreases from in vivo tissue cage fluids (means) for levofloxacin at 50 and 100 mg/kg/day, rifampin, cloxacillin, vancomycin, linezolid, and controls, respectively, were: -1.24, -2.26, -2.1, -1.56, -1.47, -1.15, and 0.33 (all groups versus controls, P < 0.05). Levofloxacin at 100 mg/kg/day (area under the concentration-time curve/MIC ratio, 234) was the most active therapy (P = 0.03 versus linezolid). Overall, in vivo efficacy was better predicted by stationary-phase studies, in which it reached a high correlation coefficient even if the rifampin group was excluded (r = 0.96; P < 0.05). Our results, including in vitro studies with nongrowing bacteria, pharmacodynamic parameters, and antimicrobial efficacy in experimental infection, provide good evidence to support the use of levofloxacin at high doses (750 to 1,000 mg/day), as recently recommended for treating patients with orthopedic prosthesis infections.

Experimental study of teicoplanin, alone and in combination, in the therapy of cephalosporin-resistant pneumococcal meningitis

OBJECTIVES

The aim of the study was to determine the efficacy of teicoplanin, alone and in combination with ceftriaxone, in a rabbit model of cephalosporin-resistant pneumococcal meningitis, and to assess the effect of concomitant therapy with dexamethasone.

METHODS

In vitro killing curves of teicoplanin, with and without ceftriaxone, were performed. Groups of eight animals per treatment were inoculated with a cephalosporin-resistant pneumococcal strain (penicillin MIC, 4 mg/L; ceftriaxone MIC, 2 mg/L; teicoplanin MIC, 0.03 mg/L) and treated over a 26 h period. Teicoplanin was administered at a dose of 15 mg/kg, alone and in combination with ceftriaxone at 100 mg/kg with or without dexamethasone at 0.25 mg/kg. CSF samples were collected at different time-points, and bacterial titres, white blood cell counts, lactate and protein concentrations and bacteriostatic/bactericidal titres were determined. Blood and CSF teicoplanin pharmacokinetic and pharmacodynamic parameters were determined.

RESULTS

Teicoplanin alone promoted a decrease in bacterial counts at 6 h of -2.66 log cfu/mL and was bactericidal at 24 h, without therapeutic failures. Similar good results were obtained when dexamethasone was used simultaneously, in spite of the penetration of teicoplanin into the CSF being significantly reduced, from 2.31% to 0.71%. Teicoplanin and ceftriaxone combinations were synergic in vitro, but not in the meningitis model.

CONCLUSIONS

Teicoplanin alone was very effective in this model of cephalosporin-resistant pneumococcal meningitis. The use of concomitant dexamethasone resulted in lower CSF teicoplanin levels, but not in therapeutic failures. The combination of teicoplanin plus ceftriaxone and dexamethasone might be a good alternative for the empirical therapy of pneumococcal meningitis. Additional data should confirm our experiments, in advance of clinical trials to assess efficacy in humans.

Experimental Study of Clinafloxacin Alone and in Combination in the Treatment of Ciprofloxacin-Susceptible and -Resistant Pneumococcal Meningitis

The increasing incidence of ciprofloxacin resistance in Streptococcus pneumoniae may limit the efficacy of the new quinolones in difficult-to-treat infections such as meningitis. The aim of the present study was to determine the efficacy of clinafloxacin alone and in combination with teicoplanin and rifampin in the therapy of ciprofloxacin-susceptible and ciprofloxacin-resistant pneumococcal meningitis in rabbits. When used against a penicillin-resistant ciprofloxacin-susceptible strain (Clinafloxacin MIC 0.12 microg/ml), clinafloxacin at a dose of 20 mg/kg per day b.i.d. decreased bacterial concentration by -5.10 log cfu/ml at 24 hr. Combinations did not improve activity. The same clinafloxacin schedule against a penicillin- and ciprofloxacin-resistant strain (Clinafloxacin MIC 0.5 microg/ml) was totally ineffective. Our data suggest that a moderate decrease in quinolone susceptibility, as indicated by the detection of any degree of ciprofloxacin resistance, may render these antibiotics unsuitable for the management of pneumococcal meningitis.

Efficacy of colistin versus beta-lactams, aminoglycosides, and rifampin as monotherapy in a mouse model of pneumonia caused by multiresistant Acinetobacter baumannii

The treatment of life-threatening infections due to carbapenem-resistant Acinetobacter baumannii has become a serious challenge for physicians worldwide. Often, only colistin shows in general good in vitro activity against these carbapenem-resistant strains, but its antibacterial efficacy in comparison with the antibiotics most used in clinical practice is not well known. We studied the efficacy of colistin versus those of imipenem, sulbactam, tobramycin, and rifampin in an experimental pneumonia model with immunocompetent mice. We used three strains of A. baumannii corresponding to the main clones (A, D, and E) involved in the outbreaks of our hospital, with different grades of resistance to imipenem (imipenem MICs of 1, 8, and 512 microg/ml, respectively) and to the other antibiotics. The MIC of colistin was 0.5 microg/ml for the three strains. Reduction of log(10) CFU/g in lung bacterial counts, clearance of bacteremia, and survival versus results with controls were used as parameters of efficacy. Imipenem and sulbactam (Deltalung counts: -5.38 and -4.64 log(10) CFU/ml) showed the highest level of bactericidal efficacy in infections by susceptible and even intermediate strains. Tobramycin and rifampin (-4.16 and -5.15 log(10) CFU/ml) provided good results against intermediate or moderately resistant strains, in agreement with killing curves and pharmacodynamics. On the contrary, colistin showed the weakest antibacterial effect among the antibiotics tested, both in killing curves and in the in vivo model (-2.39 log(10) CFU/ml; P < 0.05). We conclude that colistin did not appear as a good option for treatment of patients with pneumonia due to carbapenem-resistant A. baumannii strains. Other alternatives, including combinations with rifampin, may offer better therapeutic profiles and thus should be studied.

Experimental study of the efficacy of vancomycin, rifampicin and dexamethasone in the therapy of pneumococcal meningitis

The object of the study was to assess the efficacy of rifampicin and the combination of rifampicin plus vancomycin in a rabbit model of experimental penicillin-resistant pneumococcal meningitis. We also studied the effect of concomitant dexamethasone on the CSF antibiotic levels and inflammatory parameters. The rabbit model of pneumococcal meningitis was used. Groups of eight rabbits were inoculated with 106 cfu/mL of a cephalosporin-resistant pneumococcal strain (MIC of cefotaxime/ceftriaxone 2 mg/L). Eighteen hours later they were treated with rifampicin 15 mg/kg/day, vancomycin 30 mg/kg/day or both plus minus dexamethasone (0.25 mg/kg/day) for 48 h. Serial CSF samples were withdrawn to carry out bacterial counts, antibiotic concentration and inflammatory parameters. Rifampicin and vancomycin promoted a reduction of >3 log cfu/mL at 6 and 24 h, and cfu were below the level of detection at 48 h. Combination therapy with vancomycin plus rifampicin was not synergic but it had similar efficacy to either antibiotic alone and it was able to reduce bacterial concentration below the level of detection at 48 h. Concomitant use of dexamethasone decreased vancomycin levels when it was used alone (P< 0.05), but not when it was used in combination with rifampicin. Rifampicin alone at 15 mg/kg/day produced a rapid bactericidal effect in this model of penicillin-resistant pneumococcal meningitis. The combination of vancomycin and rifampicin, although not synergic, proved to be equally effective. Using this combination in the clinical setting may allow rifampicin administration without emergence of resistance, and possibly concomitant dexamethasone administration without significant interference with CSF vancomycin levels.

Relationship between penicillin and cephalosporin resistance of Streptococcus pneumoniae strains and its inflammatory activity in the experimental model of meningitis

Using a rabbit model of meningitis, we sought to compare the inflammatory activity induced by three pneumococcal strains with different susceptibilities to penicillin and cephalosporins, belonging to the serotypes 3, 6B and 23F at different inoculum sizes. These serotypes are prevalent in Western Europe and are believed to produce a moderate-to-severe cerebrospinal fluid (CSF) inflammatory response. Only minor differences were observed in the inflammatory activity evoked by the three strains in the subarachnoid space, and most were probably related to differences in bacterial counts. Infection by serotype 23F caused secondary bacteremia in all challenged animals. Our findings reinforce the concept that resistant pneumococci are not more virulent, a fact that should be taken into account when evaluating the efficacy of different anti-pneumococcal therapies. However, the frequent induction of secondary bacteremia by the resistant serotype 23F requires further study.

Impact of antibiotic resistance on chemotherapy for pneumococcal infections

Over the past three decades, penicillin-resistant pneumococci have emerged worldwide. In addition, penicillin-resistant strains have also decreased susceptibility to other beta-lactams (including cephalosporins) and these strains are often resistant to other antibiotic groups, making the treatment options much more difficult. Nevertheless, the present in vitro definitions of resistance to penicillin and cephalosporins in pneumococci could not be appropriated for all types of pneumococcal infections. Thus, current levels of resistance to penicillin and cephalosporin seem to have little, if any, clinical relevance in nonmeningeal infections (e.g., pneumonia or bacteremia). On the contrary, numerous clinical failures have been reported in patients with pneumococcal meningitis caused by strains with MICs > or = 0.12 microg/ml, and penicillin should never be used in pneumococcal meningitis except when the strain is known to be fully susceptible to this drug. Today, therapy for pneumococcal meningitis should mainly be selected on the basis of susceptibility to cephalosporins, and most patients may currently be treated with high-dose cefotaxime (+/-) vancomycin, depending on the levels of resistance in the patient's geographic area. In this review, we present a practical approach, based on current levels of antibiotic resistance, for treating the most prevalent pneumococcal infections. However, it should be emphasized that the most appropriate antibiotic therapy for infections caused by resistant pneumococci remains controversial, and comparative, randomized studies are urgently needed to clarify the best antibiotic therapy for these infections.

Evaluation of combined ceftriaxone and dexamethasone therapy in experimental cephalosporin-resistant pneumococcal meningitis

The treatment of meningitis caused by strains of Streptococcus pneumoniae with decreased susceptibility to third-generation cephalosporins is an increasingly frequent and difficult problem. In this study a rabbit model of meningitis was used to determine the efficacy of ceftriaxone at different dosages, and to establish the effect of the addition of dexamethasone to the chemotherapeutic regimen. Groups of eight rabbits were inoculated with 10(6) cfu/mL of a cephalosporin- resistant strain of S. pneumoniae (MIC of cefotaxime/ceftriaxone 2 mg/L). Eighteen hours after inoculation, ceftriaxone (50 or 100 mg/kg/day) with or without dexamethasone (0. 25 mg/kg/ day) was administered for a period of 48 h. The ceftriaxone dose of 50 mg/kg/day was not fully effective in this model (therapeutic failure rate 28%). With a dose of 100 mg/kg/day there were no therapeutic failures and all CSF cultures were below the level of detection at 48 h. CSF ceftriaxone concentrations, area under the time-concentration curve and time above the MIC were not significantly different with or without dexamethasone. However, concomitant use of dexamethasone resulted in higher CSF bacterial counts and a higher number of therapeutic failures (57% with the 50 mg/kg/day dose and 28% with the 100 mg/kg/day dose). Increasing doses of ceftriaxone might be an effective mode of therapy for meningitis caused by S. pneumoniae with MIC </= 2 mg/L. However, in contrast to cephalosporin-sensitive cases, in cases caused by ceftriaxone-resistant strains, concomitant use of dexamethasone was associated with a higher failure rate even when a higher dosage of ceftriaxone was used.

Streptococcal meningitis in adult patients: current epidemiology and clinical spectrum

Streptococci other than Streptococcus pneumoniae are a rare cause of bacterial meningitis in adults. We report 29 cases of streptococcal meningitis (1977-1997). The patients comprised 19 men and 10 women, with a mean age +/- standard deviation of 47 +/- 18 years. Nine cases were secondary to neurosurgical procedures, seven to brain abscess, five to cerebrospinal fluid pericranial fistula, and three to endocarditis. Causative microorganisms included the following: viridans group streptococci, 20 cases; anaerobic streptococci, 3; Streptococcus agalactiae, 3; Streptococcus bovis, 2; and Streptococcus pyogenes, 1. Four Streptococcus mitis strains showed decreased susceptibility to penicillin (MIC, 0.5-2 microg/mL). Five patients (17%) died. The infection is increasing in the hospital setting. Streptococci resistant to penicillin should be considered in the empirical treatment of nosocomial meningitis. In cases of community-acquired infection, anaerobic streptococci or streptococci of the Streptococcus milleri group should alert the clinician to the presence of an undiagnosed brain abscess, whereas oral streptococci of the viridans group suggest the diagnosis of bacterial endocarditis.

Current usefulness of procaine penicillin in the treatment of pneumococcal pneumonia

The aim of this study was to determine whether procaine penicillin could be used in the treatment of suspected pneumococcal pneumonia of mild to moderate severity in an area with a high prevalence of penicillin resistance. Forty-nine patients were treated with 1.2 x 10(6) U of i.m. procaine penicillin every 12 h. By intent-to-treat analysis, 40 of 49 patients were cured and no patient died. Streptococcus pneumoniae could be demonstrated in 17 patients; 5 of 17 isolates were resistant to penicillin (MICs 0.25-4 microg/ml). Fifteen of 17 patients were cured with procaine penicillin, one presented allergy, and one was a therapeutic failure. Mean penicillin serum levels were 2.39 +/- 1.16 microg/ml (peak) and 0.61 +/- 0.38 microg/ml (trough). The results suggest that procaine penicillin may still be useful in the empirical therapy of suspected pneumococcal pneumonia.

[In vitro bactericide activity of different antibiotic combinations to Streptococcus pneumoniae resistant to penicillin and cefotaxime]

BACKGROUND

To determinate the bactericidal activity of vancomycin, rifampicin, cefotaxime, ceftriaxone and their double and triple combinations against penicillin and third generation cephalosporin-resistant. Streptococcus pneumoniae strain.

METHODS

A study of the bactericidal activity of antibiotics alone and in combination was performed by killing-curves with fixed concentration of 2 micrograms/ml, equivalent to 1 < MIC for cefotaxime and ceftriaxone, to 8 x MIC for vancomycin and to 32 < MIC for rifampin.

RESULTS

Vancomycin was the only antibiotic with bactericidal effect at 6 hours. Cefotaxime had bactericidal effect at 12 hours. Rifampin had no bactericidal effect. The association of vancomycin plus third generation cephalosporins (cefotaxime and ceftriaxone) showed indifferent effect. Rifampin decreased the bactericidal activity of vancomycin at 12 hours, when both were studied in combination, and it demonstrated antagonistic effect in the double and triple combination in which rifampicin was included.

CONCLUSIONS

All associations of vancomycin plus third generation cephalosporins were bactericidal effects, but they did no show synergistic effects against penicillin- and third generation cephalosporin S. pneumoniae strain 2349. All combinations with rifampin showed decreased bactericidal activity or antagonistic effects. However, these results may be interpreted with caution because the in vivo experience of an experimental meningitis model in rabbits showed that the associations of vancomycin plus rifampin and vancomycin plus cefotaxime and rifampin were effective combinations. More in vivo and in vitro comparative studies are needed to demonstrate the reliability of in vitro results.

High doses of cefotaxime in treatment of adult meningitis due to Streptococcus pneumoniae with decreased susceptibilities to broad-spectrum cephalosporins

We treated nine patients (10 episodes) with meningitis caused by Streptococcus pneumoniae isolates with decreased susceptibilities to broad-spectrum cephalosporins with high doses of cefotaxime (300 mg/kg of body weight per day; maximum dose, 24 g/day). Early adjunctive therapy with dexamethasone was also administered. Cefotaxime MICs were 0.5 (three episodes), 1 (five episodes), and 2 (two episodes) micrograms/ml, and MBCs ranged from 1 to 4 micrograms/ml. Therapy was well tolerated, and all patients experienced prompt clinical improvement. One patient died 8 days after the end of therapy, the central nervous system infection had already been cured, and the remaining patients recovered without relapses.

Penetration of the blood-brain barrier: enhancement of drug delivery and imaging by bacterial glycopeptides

The blood-brain barrier restricts the passage of many pharmacological agents into the brain parenchyma. Bacterial glycopeptides induce enhanced blood-brain barrier permeability when they are present in the subarachnoid space during meningitis. By presenting such glycopeptides intravenously, blood-brain barrier permeability in rabbits was enhanced in a reversible time- and dose-dependent manner to agents < or = 20 kD in size. Therapeutic application of this bioactivity was evident as enhanced penetration of the antibiotic penicillin and the magnetic resonance imaging contrast agent gadolinium-diethylene-triamine-pentaacetic acid into the brain parenchyma.

Influence of dexamethasone on efficacy of ceftriaxone and vancomycin therapy in experimental pneumococcal meningitis

Using a rabbit model of meningitis, we sought to determine whether concomitant use of dexamethasone affects the penetration and efficacy of ceftriaxone or vancomycin in cerebrospinal fluid. Rabbits were inoculated with a penicillin-sensitive strain of Streptococcus pneumoniae and treated with ceftriaxone or vancomycin with or without dexamethasone. In the ceftriaxone-treated groups, no statistically significant differences were seen between the group treated with dexamethasone and that without dexamethasone; however, in the vancomycin-treated groups we found statistically significant lower cerebrospinal fluid vancomycin levels at 2 h in the dexamethasone-treated rabbits and differences in bacterial killing.

Resistance to penicillin and cephalosporin and mortality from severe pneumococcal pneumonia in Barcelona, Spain

BACKGROUND

Penicillin-resistant strains of Streptococcus pneumoniae are now found worldwide, and strains with resistance to cephalosporin are being reported. The appropriate antibiotic therapy for pneumococcal pneumonia due to resistant strains remains controversial.

METHODS

To examine the effect of resistance to penicillin and cephalosporin on mortality, we conducted a 10-year, prospective study in Barcelona of 504 adults with culture-proved pneumococcal pneumonia.

RESULTS

Among the 504 patients, 145 (29 percent) had penicillin-resistant strains of S. pneumoniae (minimal inhibitory concentration [MIC] of penicillin G, 0.12 to 4.0 micrograms per milliliter), and 31 patients (6 percent) had cephalosporin-resistant strains (MIC of ceftriaxone or cefotaxime, 1.0 to 4.0 micrograms per milliliter). Mortality was 38 percent in patients with penicillin-resistant strains, as compared with 24 percent in patients with penicillin-sensitive strains (P = 0.001). However, after the exclusion of patients with polymicrobial pneumonia and adjustment for other predictors of mortality, the odds ratio for mortality in patients with penicillin-resistant strains was 1.0 (95 percent confidence interval, 0.5 to 1.9; P = 0.84). Among patients treated with penicillin G or ampicillin, the mortality was 25 percent in the 24 with penicillin-resistant strains and 19 percent in the 126 with penicillin-sensitive strains (P = 0.51). Among patients treated with ceftriaxone or cefotaxime, the mortality was 22 percent in the 59 with penicillin-resistant strains and 25 percent in the 127 with penicillin-sensitive strains (P = 0.64) The frequency of resistance to cephalosporin increased from 2 percent in 1984-1988 to 9 percent in 1989-1993 (P = 0.002). Mortality was 26 percent in patients with cephalosporin-resistant S. pneumoniae and 28 percent in patients with susceptible organisms (P = 0.89). Among patients treated with ceftriaxone or cefotaxime, mortality was 22 percent in the 18 with cephalosporin-resistant strains and 24 percent in the 168 with cephalosporin-sensitive organisms (P = 0.64).

CONCLUSIONS

Current levels of resistance to penicillin and cephalosporin by S. pneumoniae are not associated with increased mortality in patients with pneumococcal pneumonia. Hence, these antibiotics remain the therapy of choice for this disease.

A single daily dose of ceftriaxone for bacterial meningitis in adults: experience with 84 patients and review of the literature

Although the pharmacokinetics of ceftriaxone allows its administration in a single daily dose, this practice is not standard in the treatment of bacterial meningitis. Herein, we review our experience and that of other investigators with this mode of therapy. We used a single daily dose of ceftriaxone (50 mg/[kg.d]; maximum, 4 g/d) for the treatment of bacterial meningitis in 84 adult patients. Meningitis was due to Neisseria meningitidis in 34 cases, to Streptococcus pneumoniae in 25, to Escherichia coli in three, to Klebsiella pneumoniae in two, to Haemophilus influenzae in two, to viridans streptococci in two, and to an unknown agent in 16. Eleven patients died, for an overall mortality of 13%; therapy failed in three additional cases. The mean trough levels of ceftriaxone in cerebrospinal fluid was 3.5 micrograms/mL; the median trough bactericidal titer at this site was 1:128. Both our experience and that in the literature suggest that a single daily dose is optimal when ceftriaxone is used for the treatment of bacterial meningitis.

[Protective effect of dexamethasone and phenytoin in the treatment of experimental pneumococcal meningitis]

BACKGROUND

Pneumococcal meningitis has a high morbidity and mortality rate despite effective antibiotherapy, probably due to an exaggerated inflammatory response of the CNS. The use of dexamethasone and phenytoin reduced mortality in adults with pneumococcal meningitis.

OBJECTIVE

We sought to determine the effect of dexamethasone, phenytoin or the association of both in several inflammatory parameters in experimental bacterial meningitis.

METHODS

The study was performed using a modification of the rabbit model of Dacey and Sande. New Zealand white rabbits were intracisteranly inoculated simultaneously with heat-killed S. pneumoniae R6 dexamethasone, phenytoin or both. CSF leucocytes and concentration of proteins and lactate were determined over 6 hours, as well as the presence of brain edema.

RESULTS

Treatment with dexamethasone alone or in association with phenytoin reduced all inflammatory parameters. The administration of phenytoin alone did not prevent an increase of CSF leucocytes or protein concentration, but did prevent the development of brain edema. A trend to wards a protective effect on the lactate concentration was observed.

CONCLUSIONS

Our results gives support to the antiinflammatory effect of dexamethasone in experimental pneumococcal meningitis, and suggest that phenytoin may have also a protective effect on brain ischemia. This protective action and the prevention of brain edema could contribute, beyond its anticonvulsivant properties, to the great reduction in the mortality rate observed in some clinical studies in patients with pneumococcal meningitis.

The impact of dexamethasone on hearing loss in experimental pneumococcal meningitis

Bacterial meningitis, particularly that resulting from Streptococcus pneumoniae, is a common cause of acquired profound sensorineural deafness in children. The pathogenesis of meningogenic hearing loss has been investigated in an experimental rabbit model. In this study significant deafness was documented within the first 15 hours of infection. Initiation of antibiotic therapy at this time diminished the severity of hearing loss in most animals. The addition of dexamethasone to antibiotic therapy prevented the development of profound deafness. These results suggest this model will be useful in developing antiinflammatory strategies to improve the outcome of bacterial meningitis.

Hypersensitivity hepatitis due to pyrazinamide

Pyrazinamide hepatotoxicity is considered secondary to a direct and dose-related toxic effect. At currently used doses, pyrazinamide provides effective short-term treatment and is free from serious side effects. We report a case of pyrazinamide-induced hepatitis for which the rechallenge data strongly suggest a hypersensitivity mechanism.

Progression of hearing loss in experimental pneumococcal meningitis: correlation with cerebrospinal fluid cytochemistry

The development of hearing loss and concomitant cerebrospinal fluid (CSF) cytochemical changes in a model of pneumococcal meningitis were examined. Rabbits were injected intracisternally with 10(5) pneumococci. Auditory evoked potentials to clicks and to 10- and 1-kHz tone bursts were recorded hourly; CSF was analyzed every 4 h. Sensorineural hearing loss developed in all animals beginning 12 h after infection and progressed to severe deafness. The onset of hearing loss was preceded by a CSF leukocytosis of > 2000 cells/microL and elevation of CSF protein and lactate concentrations to > or = 1 mg/mL. Temporal bone histopathology showed pneumococci and leukocytes extending from the CSF to the perilymph via the cochlear aqueduct. Hearing loss can develop early in the course of meningitis and is preceded by the abrupt onset of inflammatory changes in CSF. Progression of hearing loss is rapid and proceeds from cochlear base to apex in parallel with the degree of inflammation.

The biologic activities of peptidoglycan in experimental Haemophilus influenzae meningitis

While gram-positive bacterial cell walls are known to incite inflammation, the contribution of gram-negative peptidoglycan to disease has not been characterized. The ability of cell wall, purified peptidoglycan, and soluble peptidoglycan subcomponents from Haemophilus influenzae to provoke inflammation was determined in a rabbit model of meningitis. Haemophilus peptidoglycan, with or without associated proteins, produced brain edema at > or = 0.1 micrograms/mL of cerebrospinal fluid (CSF); leukocytosis and protein accumulation in CSF occurred only at > or = 10.0 micrograms/mL of CSF. Solubilized peptidoglycan was 10-fold more active than intact cell wall. The bioactivity of peptidoglycan from ampicillin-resistant H. influenzae was at least twofold greater than that of ampicillin-sensitive strains. Consistent with these pathologic effects of purified peptidoglycan, ampicillin-induced bacterial lysates in which endotoxin was neutralized induced brain edema and protein influx but little leukocytosis. Thus, peptidoglycan seems to contribute to the pathology of gram-negative meningitis, particularly brain edema.

Differing roles for platelet-activating factor during inflammation of the lung and subarachnoid space. The special case of Streptococcus pneumoniae

Although well-characterized in the lung, the role of platelet-activating factor (PAF) in inflammation in the central nervous system is undefined. Using rabbit models of meningitis and pneumonia, PAF was found to induce significant blood-brain barrier permeability and brain edema at doses five times lower than those required to generate leukocyte recruitment to the subarachnoid space. Both leukocytosis and increased vascular permeability occurred in response to PAF in the lung. Antibody to the CD-18 family of leukocyte adhesion molecules inhibited leukocyte recruitment in response to PAF in the brain (greater than 80%); a similar level of inhibition in the lung required treatment with a combination of a PAF receptor antagonist (L-659,989) and anti-CD18 antibody. Treatment with L-659,989 decreased abnormal cerebrospinal fluid cytochemical values induced by intracisternal challenge with pneumococci but not Haemophilus influenzae, indicating a special role for PAF in pneumococcal disease. Antibodies directed at phosphorylcholine, a unique, shared determinant of bioactivity of PAF and pneumococcal cell wall, obviated the inflammatory potential of both agents. However, no evidence for a direct PAF-like activity of pneumococcal cell wall components was detected in vitro by bioassay using platelets or neutrophils. It is concluded that PAF can induce inflammation in the subarachnoid space. In brain, PAF effects appear to be mediated through CD-18-dependent events, while in lung, PAF effects independent of CD-18 are also evident. At both sites, PAF is of particular clinical importance during inflammation induced by pneumococci apparently due to a unique proinflammatory relationship between the pneumococcal cell wall teichoic acid and PAF.

Bacterial components and the pathophysiology of injury to the blood-brain barrier: does cell wall add to the effects of endotoxin in gram-negative meningitis?

In animal models, the lipopolysaccharide (LPS) from Haemophilus influenzae contributes to all the signs of meningitis associated with living bacteria. However, when tested in vitro, the amount of LPS in cerebrospinal fluid (CSF) in natural disease shows much greater effects on leukocytes than on endothelial permeability. To investigate whether other bacterial components act with LPS to incite meningeal inflammation, animals were challenged intracisternally with H. influenzae lysates. Upon neutralization of endotoxin, leukocytosis was greatly attenuated, but protein accumulation in CSF persisted. Cell wall from H. influenzae induced meningeal inflammation in a pattern opposite to that of LPS. Its ability to induce blood-brain barrier permeability greatly exceeded its ability to induce leukocytosis in vivo. Thus, cell wall, by acting on endothelia, and LPS, by inducing leukocytosis, may cooperate to induce inflammation in H. influenzae meningitis. Optimal reduction of inflammation and tissue damage in meningitis may require agents directed against cell wall as well as LPS.

Integrin-mediated localization of Bordetella pertussis within macrophages: role in pulmonary colonization

The adherence of Bordetella pertussis to human respiratory cilia is critical to the pathogenesis of whooping cough but the significance of bacterial attachment to macrophages has not been determined. Adherence to cilia and macrophages is mediated by two large, nonfimbrial bacterial proteins, filamentous hemagglutinin (FHA), and pertussis toxin (PT). PT and FHA both recognize carbohydrates on cilia and macrophages; FHA also contains an Arg-Gly-Asp (RGD) sequence which promotes bacterial association with the macrophage integrin complement receptor 3 (CR3). We determined that virulent B. pertussis enter and survive in mammalian macrophages in vitro and that CR3 is important for this uptake process. We then determined the relative contribution of CR3 versus carbohydrate-dependent interactions to in vivo pulmonary colonization using a rabbit model. B. pertussis colonized the lung as two approximately equal populations, one extracellular population attached to ciliary and macrophage surface glycoconjugates and another population within pulmonary macrophages. Loss of the CR3 interaction, either by mutation of FHA or treatment with antibody to CR3, disrupted accumulation of viable intracellular bacteria but did not prevent lung pathology. In contrast, elimination of carbohydrate-bound bacteria, either by a competitive receptor analogue or an anti-receptor antibody, was sufficient to prevent pulmonary edema. We propose that CR3-dependent localization of B. pertussis within macrophages promotes persistence of bacteria in the lung without pulmonary injury. On the other hand, the presence of extracellular bacteria adherent to cilia and macrophages in carbohydrate-dependent interactions is associated with pulmonary pathology.

Intravenous ciprofloxacin therapy in severe infections

Fifty evaluable patients (34 men and 16 women; mean age, 47 years) with severe infections were given intravenous ciprofloxacin (200 mg every 12 hours) for a mean of 14 days. Therapy was continued with oral ciprofloxacin 500 to 750 mg every 12 hours in 34 cases for a mean of 57 days. The sources of the infections were bone and joint (26 patients), respiratory tract (10 patients), urinary tract (four patients), soft tissue (four patients), abdominal (three patients), bacteremia of unknown origin (two patients), and right-sided endocarditis (one patient). Fifteen patients (30 percent) were bacteremic. Causative organisms included Pseudomonas aeruginosa (32 patients), other gram-negative bacilli (18 patients), and gram-positive cocci (nine patients). Minimal inhibitory concentrations ranged between 0.03 and 1 microgram/ml. Mean peak serum concentrations were 1.58 micrograms/ml (intravenous) and 2 micrograms/ml (oral); mean trough serum concentrations were 0.23 micrograms/ml (intravenous) and 0.32 micrograms/ml (oral). Serum bactericidal activity values achieved after intravenous and oral therapy were similar. Response to therapy was evaluated separately in patients with or without osteomyelitis. In 30 patients with infections other than osteomyelitis, clinical cure was achieved in 27 (90 percent), and therapy failure occurred in three patients. In the 20 remaining patients with osteomyelitis, 15 (75 percent) had a satisfactory response, with apparent cure after a mean follow-up of 11 months, whereas five had therapeutical failure (P. aeruginosa became resistant in four of them). Overall, no major adverse effects were encountered. Superinfection by a resistant P. aeruginosa was observed in three patients. Intravenous ciprofloxacin is an effective and safe agent for the therapy of severe infections caused by susceptible organisms.