Antibiotic sensitivity of important pathogens of bacterial respiratory tract infections in Northeast Germany

BACKGROUND: There is still a lack of comprehensive study results about resistance of bacterial respiratory pathogens from the east of the Federal Republic of Germany. METHODS: In Greifswald we isolated in 1995 and 1996 320 strains of typical pathogens and tested their susceptibility to 14 antibiotics, using the microbouillon dilution method. RESULTS: Pneumococci and beta-haemolytic streptococci were completely susceptible to penicillin and all other beta-lactam-antibiotics, clindamycin and vancomycin. 4.8% of pneumococci and 10.0% of Streptococcus pyogenes isolates were resistant to erythromycin. This should lead to a more differentiated use of macrolides as concerns these pathogens, especially as penicillin still has high efficacy in these cases. Pneumococci had resistance rates of 4.8%, 9.5% and 6.7% to cotrimoxazole, tetracycline and ofloxacin, respectively. No strain of Haemophilus influenzae produced a beta-lactamase, 2.6% of strains were relatively resistant to ampicillin, even in combination with sulbactam. Cefaclor, erythromycin and tetracycline had restricted efficacy of 16.7%, 14.1% and 53.8%, respectively. Cefuroxime, cefixime, cefepime, imipenem and ofloxacin all had complete efficacy. 77.8% of Moraxella catarrhalis isolates were beta-lactamase positive. Strains were susceptible to erythromycin, ofloxacin and all tested beta-lactam-antibiotics except ampicillin and cefaclor. There was a relative resistance to clindamycin and tetracyclin of 22.2% and 2.2%, respectively. DISCUSSION: We present our results in national and international comparison, describe tendencies of resistance, give reasons for the low incidence of penicillin resistance in pneumococci in Germany and draw conclusions for empirical chemotherapy.     

Mycobacteria as pathogens of respiratory infection

As the result of a formidable effort, the recent TB epidemic in the United States has abated; however, major questions remain as the risk of TB diminishes. Will we maintain an adequate public health effort not only to prevent another resurgence of TB but also to renew our pursuit of TB elimination? Do we have the will to extend the fight against TB worldwide as the TB threat in the United States declines? What is the best way to incorporate new diagnostic technology into routine practice? What are the best strategies for preventing and treating TB in AIDS patients? From the standpoint of NTM lung diseases, the major challenges are to educate clinicians about the variety and clinical presentation of NTM lung pathogens in order to recognize NTM lung disease as early as possible and to maximize treatment options. Hopefully, we can also improve upon the recent unprecedented progress in treatment regimens for NTM diseases of all types.     

A modified PCR-based method for rapid non-radioactive detection of clinically important pathogens

We have devised a sensitive and rapid method for the detection of several bacterial pathogens in clinical specimens using PCR. This method has been named Direct Labeling and Detection Procedure (DLDP) and is based on the direct incorporation of a nonradioactive digoxigenin label (DIG-11-dUTP) into a microbial species-specific gene fragment during amplification. Following amplification, the resulting PCR products are cleansed of nonincorporated DIG-11-dUTP, spotted onto a nylon membrane, fixed by UV-crosslinking and the labeled DNA is visualized by digoxigenin detection reagents. Using cultivated reference bacteria (Staphylococcus aureus, Streptococcus pneumoniae, Pseudomonas aeruginosa) we were able to demonstrate a rapid and sensitive detection of < 20 CFU of bacteria in human secretions (sputum, urine, mucous). The present study suggests that DLDP can be used as a reliable method for indication of bacteria in clinical or environmental specimens with the proviso that the selected corresponding oligonucleotide primers provide amplification of strong species-specific genes.     

Activities of new fluoroquinolones against fluoroquinolone-resistant pathogens of the lower respiratory tract

The activities of six new fluoroquinolones (moxifloxacin, grepafloxacin, gatifloxacin, trovafloxacin, clinafloxacin, and levofloxacin) compared with those of sparfloxacin and ciprofloxacin with or without reserpine (20 microg/ml) were determined for 19 Streptococcus pneumoniae isolates, 5 Haemophilus sp. isolates, and 10 Pseudomonas aeruginosa isolates with decreased susceptibility to ciprofloxacin from patients with clinically confirmed lower respiratory tract infections. Based upon the MICs at which 50% of isolates were inhibited (MIC50s) and MIC90s, the most active agent was clinafloxacin, followed by (in order of decreasing activity) trovafloxacin, moxifloxacin, gatifloxacin, sparfloxacin, and grepafloxacin. Except for clinafloxacin (and gatifloxacin and trovafloxacin for H. influenzae), none of the new agents had improved activities compared with that of ciprofloxacin for P. aeruginosa and H. influenzae. A variable reserpine effect was observed for ciprofloxacin and S. pneumoniae; however, for 9 of 19 (47%) isolates the MIC of ciprofloxacin was decreased by at least fourfold, suggesting the presence of an efflux pump contributing to the resistance phenotype. The laboratory parC (Ser79) mutant strain of S. pneumoniae required eightfold more ciprofloxacin for inhibition than the wild-type strain, but there was no change in the MIC of sparfloxacin and only a 1-dilution increase in the MICs of the other agents. For efflux pump mutant S. pneumoniae the activities of all the newer agents, except for levofloxacin, were reduced. Except for clinafloxacin, all second-step laboratory mutants required at least 2 microg of all fluoroquinolones per ml for inhibition.     

A one-year survey of respiratory and urinary pathogens and their antimicrobial susceptibility

Human cytomegalovirus (CMV) infection is often associated with myelosuppression and acute inflammatory reaction in immunocompromised patients. We have previously documented that CMV exposure of bone marrow (BM) stromal cells reduces the capacity of these cells to support hematopoiesis because of a decreased production of colony-stimulating factors. This study examines the potential role of CMV on constitutive and lipopolysaccharide (LPS)-stimulated production of cytokines involved in inflammatory reaction, interleukin-6 (IL-6) and leukemia inhibitory factor (LIF) by BM stromal cells. The release of IL-6 was already detectable 2 hours post CMV-infection (2.5-fold increase in production) and the cumulative production of IL-6 after 5 days of infection was 23 +/- 1.2 ng/mL (ninefold increase in production). CMV was also able to induce a time-dependent production of LIF that was maximal 8 hours after CMV infection (2.5-fold increase in production). Concomitantly, there was no detectable release of granulocyte colony-stimulating factor (G-CSF) and granulocyte-macrophage CSF (GM-CSF) by CMV-infected stromal cells. The similar IL-6 and LIF production in the presence of polymyxin B ruled out the possibility that this increase could be caused by contamination of the viral stock by endotoxin. In addition, ultraviolet-inactivated virus behaved similarly to live virus and caused the release of IL-6 and LIF. However, heat-inactivated CMV was unable to induce IL-6 and LIF secretion by BM stromal cells. The production of IL-6 and LIF was also evaluated after stimulation by LPS. After 5 days of CMV exposure, the LPS-stimulated production of IL-6 and LIF was significantly lower than uninfected controls. This LPS-induced release of cytokine production was found to be dependent of viral replication. The experiments have shown that CMV is a potent inducer of IL-6 and LIF with differential effect on constitutive and LPS-stimulated cytokine production by stromal cells; we suggest that CMV induction of IL-6 and LIF during the first hours of infection could play a role in CMV-induced inflammatory reaction. Moreover, our results show that human CMV can disturb the balanced cytokine network involved in the regulation of hematopoiesis.     

An important role for intestinally derived T cells in respiratory defence

Margaret Dunkley, Reinhard Pabst and Allan Cripps discuss the role of intestinally derived T cells in protecting the lung against Gram-negative bacterial infection. They describe the factors directing T-cell migration from gut-associated lymphoid tissue to lung, and focus on the role of T cells and T-cell-derived cytokines in bacterial clearance from the lung.     

Bacteriological activity of trovafloxacin, a new quinolone, against respiratory tract pathogens

BACKGROUND: Corpus callosum (CC) morphology has recently been investigated in schizophrenia using refined imaging and analytic techniques; however, methodological problems and small sample sizes have led to inconsistent findings. METHODS: This study used a large sample of male schizophrenics (n = 79) and male controls (n = 65) to investigate size and shape of the CC on midsagittal magnetic resonance images. Size was determined by tracing the area of the CC, and shape was determined using a landmark-based analysis. In addition, the relationship between CC morphology and phenomenologic variables such as age of onset, length of illness, exposure to medications, and symptom severity was explored. RESULTS: After controlling for age, height, and parental socioeconomic status, there was a main effect of diagnosis on CC size (F = 5.05, df = 1,139, p < .03), with patients' CCs being significantly smaller. No difference was found between patients and controls in CC shape (F = 1.07, df = 18,125, p > .38) or orientation (F = 0.79, df = 18,125, p > .70), using a landmark-based technique. Finally, there was a significant inverse correlation between size of CC and severity of negative symptoms. CONCLUSIONS: These findings support previous studies that have found a decrease in size of the CC in patients with schizophrenia. Moreover, the decrement in volume is generalized, not regional, and is related to the severity of negative symptoms.     

Bronchoalveolar distribution of cefuroxime axetil and in-vitro efficacy of observed concentrations against respiratory pathogens

The concentrations of cefuroxime in human alveolar macrophages (AM), epithelial lining fluid (ELF), bronchial mucosal biopsies and serum were measured after a single dose, equivalent to 500 mg of cefuroxime base, given in the form of the orally-administered pro-drug, cefuroxime axetil. Fourteen patients undergoing fibreoptic bronchoscopy with bronchoalveolar lavage were studied. The mean ELF concentration was 0.7 mg/L, that of bronchial biopsies was 1.8 mg/kg and that of serum 3.5 mg/L. AM-associated cefuroxime was detected in nine patients. To assess the in-vitro activity of the concentrations achieved at the potential sites of infection, clinical isolates of common respiratory pathogens were exposed to two concentrations of cefuroxime, based on the observed concentrations in ELF and bronchial mucosa. ELF and mucosal site concentrations were effective against Streptococcus pneumoniae (except one strain with reduced susceptibility to benzyl penicillin) and Haemophilus influenzae. The ELF concentration was less effective against Moraxella catarrhalis.     

Rhinoviruses induce interleukin-8 mRNA and protein production in human monocytes

Ultraviolet light irradiation of DNA in vitro and in vivo induces cyclobutane dimers, (6-4) pyrimidine-pyrimidone photoproducts and a variety of minor products. Using a defined DNA fragment, we have identified two classes of sites that can be cleaved by Escherichia coli endonuclease III: single cytosines whose heat lability corresponds to that of cytosine hydrates and more heat-stable dipyrimidines containing cytosine. The dipyrimidine products are induced at sites suggestive of (6-4) photoproducts but are not recognized as (6-4) photoproducts by radioimmunoassay. Use of oligonucleotides containing a single cyclobutane thymine dimer, a (6-4) photoproduct or the Dewar photoisomer of the (6-4) photoproduct also indicated that these products are not substrates for endonuclease III. We have therefore identified a minor UV photoproduct that has the same sequence specificity as the two major dipyrimidine photoproducts; it may be a minor isomer, a unique derivative or an oxidative lesion confined to dipyrimidine sites. Its biological significance is not yet known but may be masked by the preponderance of major products at the same sites. Its occurrence at the particular site in dipyrimidine sequences involved in the mutagenic action of UV photoproducts suggests that it may play a role in generating C to T transitions that are common UV-induced mutations.     

Bronchoalveolar lavage or oropharyngeal cultures to identify lower respiratory pathogens in infants with cystic fibrosis

As collections of lower respiratory tract specimens from young children with cystic fibrosis (CF) are difficult, we determined whether oropharyngeal cultures predicted lower airway pathogens. During 1992-1994, 75 of 90 (83%) infants with CF diagnosed by neonatal screening had 150 simultaneous bronchoalveolar lavage (BAL) and oropharyngeal specimens collected for quantitative bacterial culture at a mean age of 17 months (range, 1-52). Ten children undergoing bronchoscopy for stridor served as controls. Total and differential cell counts and interleukin-8 concentrations were measured in BAL fluid. A subset of bacterial pathogens were typed by pulsed field gel electrophoresis. A non-linear relationship with inflammatory markers supported a diagnosis of lower airway infection when > or = 10(5) colony-forming units/ml were detected. This criterion was met in 47 (31%) BAL cultures from 37 (49%) children. Staphylococcus aureus (19%), Pseudomonas aeruginosa (11%), and Hemophilus influenzae (8%) were the major lower airway pathogens. In oropharyngeal cultures, S. aureus (47%), Escherichia coli (23%), H. influenzae (15%), and P. aeruginosa (13%) predominated. The sensitivity, specificity, and positive and negative predictive values of oropharyngeal cultures for pathogens causing lower respiratory infections were 82%, 83%, 41%, and 97%, respectively. When there was agreement between paired oropharyngeal and BAL cultures, genetic fingerprinting showed some strains of the same organism were unrelated. We conclude that oropharyngeal cultures do not reliably predict the presence of bacterial pathogens in the lower airways of young CF children.     

Newer oral antimicrobials for resistant respiratory tract pathogens. Which show the most promise?

As antimicrobial resistance to tried-and-true drugs continues to build, an arsenal of new drugs aimed at resistant respiratory tract pathogens is needed. Penicillin is now ineffective against several common pathogens, including many pneumococcal organisms. Newer antimicrobials, including macrolides, cephalosporins, and fluoroquinolones, have been developed to take its place. The authors of this article present a progress report of the fight against respiratory tract infection and an assessment of the most promising newer agents for use against multidrug-resistant pathogens.     

Susceptibility testing interpretive criteria for levofloxacin when testing respiratory pathogens, Haemophilus influenzae and Moraxella catarrhalis

The more active L-isomer, levofloxacin, of the racemic ofloxacin mixture has been under development for therapeutic use. In this study, we evaluated the activity of ofloxacin, levofloxacin, and D-ofloxacin against the fastidious respiratory tract pathogens Haemophilus influenzae and Moraxella catarrhalis. Levofloxacin was two-fold more active than ofloxacin against H. influenzae (MIC90, 0.015 microgram/ml), and D-ofloxacin was least active (MIC90, 1 microgram/ml). For M. catarrhalis the MIC90 values were 0.03 microgram/ml, 0.06 microgram/ml, and 2 micrograms/ml for levofloxacin, ofloxacin, and D-ofloxacin, respectively. For disk diffusion susceptibility testing, Chocolate Mueller-Hinton agar (CMH) was considered preferable to Haemophilus test medium (HTM) because it supported the growth of all of 105 H. influenzae strains whereas five strains failed to grow on HTM. In addition, the margins of the zones of inhibition were more distinct on CMH and the Haemophilus species strains with elevated fluoroquinolone MICs were readily distinguished. The superior growth on CMH was reflected in a reduction of inhibition zone diameters of 2-3 mm relative to the inhibition zone diameters on HTM. The previously proposed interpretive criteria for the 5 microgram disk diffusion susceptibility test (susceptible at > or = 17 mm) results in complete categorical agreement with the reference microdilution broth method for M. catarrhalis on Mueller Hinton agar and for H. influenzae on HTM and CMH. However, the minimum diameter of the zone of inhibition recorded for a member of the dominant population of either species was considerably greater (25 mm) than 17 mm on any of the media tested.     

Ipriflavone: an important bone-building isoflavone

Ipriflavone, an isoflavone synthesized from the soy isoflavone daidzein, holds great promise in the prevention and treatment of osteoporosis and other metabolic bone diseases. It has been widely studied in humans and found effective for inhibiting bone resorption and enhancing bone formation, the net result being an increase in bone density and a decrease in fracture rates in osteoporotic women. While ipriflavone appears to enhance estrogen's effect, it does not possess intrinsic estrogenic activity, making it an attractive adjunct or alternative to conventional hormone replacement therapy. Preliminary studies have also found ipriflavone effective in preventing bone loss associated with chronic steroid use, immobility, ovariectomy, renal osteodystrophy, and gonadotrophin hormone-releasing hormone agonists. In addition, it holds promise for the treatment of other metabolic diseases affecting the bones, including Paget's disease of the bone, hyperparathyroidism, and tinnitus caused by otosclerosis.     

Avian tumor viruses: persistent and evolving pathogens

Most neoplasias of lymphoid and other hematopoietic cells in commercial poultry are caused by viruses which belong to one of four distinct groups. Marek's disease virus (MDV) is an oncogenic herpesvirus. Avian leukosis virus (ALV), reticuloendotheliosis virus (REV) and lymphoproliferative disease virus (LPDV) are oncogenic retroviruses. Each group is distinguished by nucleic acid type, molecular structure, antigenicity, epidemiology, host range and other characteristics. However, most of these viruses have in common a unique ability to persist, both in the host and in the ecosystem. In addition, both the viruses and the virus-host relationships for several members of the group have demonstrated a propensity to evolve with time, creating new dilemmas for diagnosis and control. A focus on the persistence and evolution of avian tumor viruses will be used to address a number of current issues with individual viruses of economic importance. Issues of primary concern include (1) the evolution of MDV towards greater virulence with concomitant reduction of vaccine efficacy and expansion of host range, (2) the emergence of subgroup J ALV as a major pathogen in meat-type breeder stocks, and (3) the increasing prevalence of REV and its evolving role as a pathogen in chickens and turkeys.