Christian T. Brandt

Danish Integrated Antimicrobial Resistance Monitoring and Research Program

This program has led to changes in the use of antimicrobial agents in Denmark and other countries.

Bacteremia causes hippocampal apoptosis in experimental pneumococcal meningitis.

BackgroundBacteremia and systemic complications both play important roles in brain pathophysiological alterations and the outcome of pneumococcal meningitis. Their individual contributions to the development of brain damage, however, still remain to be defined.MethodsUsing an adult rat pneumococcal meningitis model, the impact of bacteremia accompanying meningitis on the development of hippocampal injury was studied. The study comprised of the three groups: I. Meningitis (n = 11), II. meningitis with attenuated bacteremia resulting from iv injection of serotype-specific pneumococcal antibodies (n = 14), and III. uninfected controls (n = 6).ResultsPneumococcal meningitis resulted in a significantly higher apoptosis score 0.22 (0.18-0.35) compared to uninfected controls (0.02 (0.00-0.02), Mann Whitney test, P = 0.0003). Also, meningitis with an attenuation of bacteremia by antibody treatment resulted in significantly reduced apoptosis (0.08 (0.02-0.20), P = 0.01) as compared to meningitis.ConclusionsOur results demonstrate that bacteremia accompanying meningitis plays an important role in the development of hippocampal injury in pneumococcal meningitis.

Factors Associated with the Occurrence of Hearing Loss after Pneumococcal Meningitis

BACKGROUND On the basis of a nationwide registration during a 5-year period (1999-2003), the frequency and severity of hearing loss was investigated retrospectively in 343 consecutive Danish patients who survived pneumococcal meningitis, to identify important risk factors (including the pneumococcal serotype) for development of hearing loss. METHODS Results of blood and cerebrospinal fluid (CSF) biochemistry, bacterial serotyping, follow-up audiological examinations, and medical records were collected, and disease-related risk factors for hearing loss were identified. The mean pure-tone hearing threshold levels were compared with normative data. RESULTS Of 240 patients examined by use of audiometry, 129 (54%) had a hearing deficit, and 50 (39%) of these 129 patients were not suspected of hearing loss at discharge from hospital. Of the 240 patients, 16 (7%) had profound unilateral hearing loss, and another 16 (7%) had bilateral profound hearing loss. Significant risk factors for hearing loss were advanced age, the presence of comorbidity, severity of meningitis, a low CSF glucose level, a high CSF protein level, and a certain pneumococcal serotype (P < .05). By applying multivariate logistic regression analysis, we found that advanced age, female sex, and a certain serotype were significant risk factors, because fewer patients with serotype 6B had hearing loss than did patients with serotype 12F (P = .03), which was the most commonly occurring serotype. CONCLUSION Hearing loss is common after pneumococcal meningitis, and audiometry should be performed on all those who survive pneumococcal meningitis. Important risk factors for hearing loss are advanced age, female sex, severity of meningitis, and bacterial serotype.

Impact of bacteremia on the pathogenesis of experimental pneumococcal meningitis.

BACKGROUND Bacteremia plays a major role in the outcome of pneumococcal meningitis. This experimental study investigated how bacteremia influences the pathophysiologic profile of the brain. METHODS Rats with Streptococcus pneumoniae meningitis were randomized to 1 of 3 groups of infected study rats: (1) rats with attenuated bacteremia resulting from intravenous injection of serotype-specific pneumococcal antibody, (2) rats with early-onset bacteremia resulting from concomitant intravenous infection, or (3) a meningitis control group. The blood-brain barrier (BBB) breakdown, ventricle size, brain water distribution, and brain pathologic findings were analyzed using magnetic resonance morphological and functional imaging. Laboratory data and clinical disease scores were obtained. RESULTS Attenuation of the bacteremic component of pneumococcal meningitis improved clinical disease symptoms and significantly reduced ventricle expansion and BBB breakdown (P< .05). Early-onset bacteremia did not further increase ventricle size or BBB leakage. Significantly increased brain edema developed among rats with both attenuated and early-onset bacteremia (P< .05). Focal brain pathologic findings were unaffected by bacteremia and were found to be associated with cerebrospinal fluid inflammation. CONCLUSION Although brain lesions appear to result from local meningeal infection, systemic infection significantly contributes to clinical disease presentation and the pathophysiology of BBB breakdown and ventricle expansion. The different end points affected by the systemic and local infectious processes should be addressed in future studies.

The Effect of S. Pneumoniae Bacteremia on Cerebral Blood Flow Autoregulation in Rats

In the present study, we studied the effect of bacteremia on cerebral blood flow (CBF) autoregulation in a rat model of pneumococcal bacteremia and meningitis. Anesthetized rats were divided into five groups (A to E) and inoculated with pneumococci intravenously and normal saline intracisternally (group A, N = 10); saline intravenously and pneumococci intracisternally (group B, N = 10); pneumococci intravenously and pneumococci intracisternally (group C, N = 5); saline intravenously, antipneumococcal antibody intravenously (to prevent bacteremia), and pneumococci intracisternally (group D, N = 10); or saline intravenously and saline intracisternally (group E, N = 10), respectively. Positive cultures occurred in the blood for all rats in groups A, B, and C, and in the cerebrospinal fluid for all rats in groups D and E. Twenty-four hours after inoculation, CBF was measured with laser-Doppler ultrasound during incremental reductions in cerebral perfusion pressure (CPP) by controlled hemorrhage. Autoregulation was preserved in all rats without meningitis (groups A and E) and was lost in 24 of 25 meningitis rats (groups B, C, and D) (P <0.01). In group A, the lower limit was higher than that of group E (P <0.05). The slope of the CBF/CPP regression line differed between the meningitis groups (P < 0.001), being steeper for group B than groups C and D, with no difference between these two groups. The results suggest that pneumococcal bacteremia in rats triggers cerebral vasodilation, which right shifts the lower limit of, but does not entirely abolish, CBF autoregulation in the absence of meningitis, and which may further aggravate the vasoparalysis induced by concomitant pneumococcal meningitis.

Routes, dynamics, and correlates of cochlear inflammation in terminal and recovering experimental meningitis

To examine the routes, dynamics and correlates of cochlear inflammation in meningitis to provide information on the pathogenesis of the associated hearing loss and indications for rational pharmacotherapeutical intervention.

Multidrug-resistant organisms in refugees: prevalences and impact on infection control in hospitals.

Introduction: The refugee crisis is a great challenge to the social and healthcare system in European countries, especially in Germany. An abundance of data has been published on the refugees’ health problems (infections as well as physical diseases and psychiatric problems) and their prevention (i.e., sanitary and vaccination programs). However, data on prevalences of multidrug-resistant organisms (MDRO) in refugees are scarce, although it is known that most refugees are from or travelled through countries with high prevalences of MDRO. This paper presents current data on MDRO colonization of refugees admitted to hospitals, and the impact of screening upon admission and infection control in hospitals is discussed. Methods: Anonymous data obtained by screening upon hospital admission were reported by hospitals in the Rhine-Main region of Germany to the local public health department. Screening and microbiological analyses were performed from December 2015 to March 2016 according to standardized and validated methods. Results: 9.8% of the refugees screened (32/325) exhibited colonization with methicillin-resistant Staphylococcus aureus (MRSA), and 23.3% of the refugees (67/290) were colonized with Gram-negative bacteria with extended spectrum beta-lactamases, and/or enterobacteria with resistance against 3 or 4 groups of antibacterials, so-called 3MRGN (multidrug-resistant Gram-negative bacteria with resistance against penicillins, cephalosporins and quinolones) and 4MRGN (with additional resistance against carbapenems). Carbapenem-resistant Gram-negative bacteria (CRGN) were detected in 2.1% (6/290) of the refugees. Conclusion: The data confirms the studies published between 2014 and 2016, encompassing refugees tested in Germany, the Netherlands and Israel, with prevalences of MRSA and CRGN up to 13.5% and 5.6%. The MDRO prevalences are higher than those of “risk groups” for MRSA, such as hemodialysis patients and patients depending on outpatient home-nursing care or residing in nursing homes. Therefore, screening and special infection control in hospitals is strongly suggested when refugees are admitted to hospitals, in order to ensure best medical practice and safety for all hospital patients regardless of their country of origin.

Bacterial invasion of the inner ear in association with pneumococcal meningitis.

Objective To examine the pathways of bacterial invasion and subsequent spreading in the inner ear during pneumococcal meningitis. Study Design A well-established adult rat model of Streptococcus pneumoniae meningitis was used. Methods Thirty rats were inoculated intrathecally with S. pneumoniae serotype 1, 3 or 9 V and received no additional treatment. The rats were sacrificed when reaching terminal illness or on Day 7 and then prepared for serial sectioning and PAS-Alcian blue staining for light microscopy. Results During the first few days after inoculation, bacteria invade the inner ear through the cochlear aqueduct, into the scala tympani of the cochlea (perilymphatic space). From here, bacteria spreads apically toward the helicotrema and subsequently basally through the scala vestibuli, toward the vestibule and the vestibular system. When the bacteria after 5 to 6 days had reached scala vestibuli of the basal turn of the cochlea, hematogenous spreading occurred to the spiral ligament and into the cochlear endolymph, subsequently to the vestibular endolymph. We found no evidence of alternative routes for bacterial invasion in the inner ear. Several internal barriers to bacterial spreading were found within the inner ear. Bacterial elimination was evidenced by engulfment by macrophages within the inner ear. Conclusion From the meninges, pneumococci invade the inner ear through the cochlear aqueduct during the first days of infection, whereas hematogenous invasion via the spiral ligament capillary bed occur at later stages. Although internal barriers exist within the inner ear, the spreading of bacteria occurs via the natural pathways of the fluid compartments. Bacterial elimination occurs by local macrophage engulfment.

Intratympanic steroid prevents long-term spiral ganglion neuron loss in experimental meningitis.

Hypothesis: Intratympanic steroid treatment prevents hearing loss and cochlear damage in a rat model of pneumococcal meningitis. Background: Sensorineural hearing loss is a long-term complication of meningitis affecting up to a third of survivors. Streptococcus pneumoniae is the bacterial species most often associated with a hearing loss. Methods: Rats were randomly assigned to 3 treatment groups: a group treated with intratympanic betamethasone and 2 control groups treated with either intratympanic or systemic saline. Treatment was initiated 21 hours after infection and repeated once a day for 3 days. Hearing loss and cochlear damage were assessed by distortion product otoacoustic emissions, auditory brainstem response at 16 kHz, and spiral ganglion neuron density. Results: Fifty-six days after infection, auditory brainstem response showed no significant differences between groups, and distortion product otoacoustic emissions showed significant hearing loss at the low frequencies in animals treated with intratympanic steroid compared with animals treated with systemic saline (p < 0.05; Mann-Whitney test). However, intratympanic steroid significantly increased the number of viable neurons in the spiral ganglion compared with both intratympanic and systemic saline (p = 0.0082 and p = 0.0089; Mann-Whitney test). Histology revealed fibrosis of the tympanic membrane and cavity in steroid-treated animals, which plausibly caused the low-frequency hearing loss. Conclusion: Intratympanic betamethasone treatment prevents long-term spiral ganglion neuron loss in experimental pneumococcal meningitis. This finding is clinically relevant in relation to postmeningitic hearing rehabilitation by cochlear implantation. However, the drug instillation in the middle ear induced local fibrosis and a concurrent low-frequency hearing loss.

Systemic Steroid Reduces Long-Term Hearing Loss in Experimental Pneumococcal Meningitis

Sensorineural hearing loss is a common complication of pneumococcal meningitis. Treatment with corticosteroids reduces inflammatory response and may thereby reduce hearing loss. However, both experimental studies and clinical trials investigating the effect of corticosteroids on hearing loss have generated conflicting results. The objective of the present study was to determine whether systemic steroid treatment had an effect on hearing loss and cochlear damage in a rat model of pneumococcal meningitis.