K. P. Schaal

Actinomycete infections in humans — a review

Diseases caused by pathogenic aerobic and facultatively anaerobic actinomycetes differ considerably with respect to their etiology, pathogenesis, clinical appearance and epidemiology. Facultatively anaerobic (fermentative) actinomycetes may not only be involved etiologically in the three classical forms of cervicofacial, thoracic and abdominal actinomycoses, but also in infections of the female genital organs, the eye, the tissue adjacent to dental implantation elements and tooth extraction wounds. The species distribution of the fermentative actinomycetes isolated from these conditions varied to a certain, but characteristic, extent, as did the concomitant actinomycotic flora. The sex ratio reported for human Actinomyces infections (male:female = 3:1) appeared to be restricted to actinomycotic abscesses and empyemas. The prevailing pathogenic, obligately aerobic actinomycete species in Germany was found to be Nocardia farcinica followed by Nocardia asteroides. The comparatively high incidence of N. farcinica infections was chiefly due to the occurrence of nosocomial postoperative wound infections by this pathogen observed in two German hospitals. Besides surgical treatment, immunosuppressive treatment appeared to be the most common factor predisposing for nocardiosis. Recent observations strongly suggested that the spectrum of human nocardial infections in Germany has been changing, as regards the overall incidence, the prevalence of N. farcinica, the sex ratio, the mean age of patients, as well as the role of N. farcinica as a possibly important nosocomial pathogen.

The cell wall porin of Nocardia farcinica: biochemical identification of the channel-forming protein and biophysical characterization of the channel properties

A channel‐forming protein was identified in cell wall extracts of the Gram‐positive, strictly aerobic bacterium Nocardia farcinica. The cell wall porin was purified to homogeneity and had an apparent molecular mass of about 87 kDa on tricine‐containing SDS–PAGE. When the 87 kDa protein was boiled for a longer time in sodium dodecylsulphate (SDS) it dissociated into two subunits with molecular masses of about 19 and 23 kDa. The 87 kDa form of the protein was able to increase the specific conductance of artificial lipid bilayer membranes from phosphatidylcholine (PC) phosphatidylserine (PS) mixtures by the formation of ion‐permeable channels. The channels had on average a single‐channel conductance of 3.0 nS in 1 M KCl, 10 mM Tris‐HCl, pH 8, and were found to be cation selective. Asymmetric addition of the cell wall porin to lipid bilayer membranes resulted in an asymmetric voltage dependence. The single‐channel conductance was only moderately dependent on the bulk aqueous KCl concentration, which indicated point charge effects on the channel properties. The analysis of the single‐channel conductance data in different salt solutions using the Renkin correction factor, and the effect of negative charges on channel conductance suggested that the diameter of the cell wall porin is about 1.4–1.6 nm. Channel‐forming properties of the cell wall porin of N. farcinica were compared with those of mycobacteria and corynebacteria. The cell wall porins of these members of the order Actinomycetales share common features because they form large and water‐filled channels that contain negative point charges.

Nocardial cerebral abscess cured with imipenem/amikacin and enucleation

A 72 year old female with cerebral abscess due to Nocardia farcinica is reported. Needle aspiration, antimicrobial therapy using a new combination of imipenem and amikacin, and, finally, surgical excision led to prompt and complete recovery. This is the oldest patient to survive cerebral nocardiosis reported in the literature. This infection, is usually regarded as opportunistic and is encountered with increasing frequency in immunocompromised conditions (organ transplantation, chemotherapy, underlying disabling disorder, acquired immunodeficiency syndrome, etc.). The literature is extensively reviewed for various aspects of this disease including prognostic factors, recent developments in antibiotic therapy (imipenem, amikacin, minocycline etc.) and the essential role of surgery in the treatment strategy.

Identification of mycobacterial isolates by thin-layer and capillary gas-liquid chromatography under diagnostic routine conditions

The mycolic acid patterns of 75 strains of mycobacteria belonging to 46 different species were studied by thin-layer chromatography (TLC). Additionally, the mycolic acid pyrolytic cleavage products were determined by capillary gas-liquid chromatography (C-GLC). Eleven different patterns based on number, type and Rf values of the detected lipid spots were identified. The mycolic acid methyl ester profiles of clinical isolates were compared with those of reference strains. In this way, it was possible to relate these clinical isolates to mycobacterial groups defined by their mycolic acid profiles. The 11 patterns and the methods used are described in detail.

Recurrent bacteremia due to Brevibacterium casei in an immunocompromised patient

A case of an immunocompromised patient who experienced two episodes of septicemia caused by a coryneform bacterium is reported. Biochemical characteristics and analysis of cellular fatty acids and of cell wall components showed two identical strains ofBrevibacterium casei to be responsible for these infections. The lack of easy-to-perform methods for identification may have led, in the past, to an underestimation of the role of this bacterium, especially in immunocompromised patients.

The cell wall porin of the gram-positive bacterium Nocardia asteroides forms cation-selective channels that exhibit asymmetric voltage dependence.

Abstract Detergent-solubilized cell wall extracts of the gram-positive, strictly aerobic bacterium Nocardia asteroides contain channel-forming activity as judged from reconstitution experiments using lipid bilayer membranes. The cell wall porin was identified as a protein with an apparent molecular mass of about 84 kDa based on SDS-PAGE. The porin was purified to homogeneity using preparative SDS-PAGE. The 84-kDa protein was no longer observed after heating in SDS buffer. The presumed dissociation products were not observed on SDS-polyacrylamide gels. The cell wall porin increased the specific conductance of artificial lipid bilayer membranes from phosphatidylcholine/phosphatidylserine mixtures by the formation of cation-selective channels, which had an average single-channel conductance of 3.0 nS in 1 M KCl. The single-channel conductance was only moderately dependent on the bulk aqueous KCl concentration, which indicated negative point charge effects on the channel properties. The analysis of the concentration dependence of the single-channel conductance using the effect of negative charges on channel conductance suggested that the diameter of the cell wall channel is about 1.4 nm. Asymmetric addition of the cell wall porin to lipid bilayer membranes resulted in an asymmetric voltage dependence. The cell wall channel switched into substates, when the cis side of the membrane, the side of the addition of the protein, had negative polarity. Positive potentials at the cis side had no influence on the conductance of the cell wall channel.

European multicentre evaluation of a commercial system for identification of methicillin-resistant staphylococcus aureus

A commercial system for the rapid detection of methicillin-resistantStaphylococcus aureus, the BBL Crystal MRSA test (C-MRSA ID; Becton Dickinson, USA), was evaluated prospectively and compared with a polymerase chain reaction test for the presence of themecA gene. Ten European centres tested a total of 676 isolates ofStaphylococcus aureus from blood cultures. The system correctly identified 661 (97.8%) isolates within 4 h. All but threemecA gene-negative isolates (99.4% specificity) yielded a negative C-MRSA ID reaction, and 158 of 170mecA gene-positive isolates were accurately detected (92.9% sensitivity). After repeated testing of discrepant results, sensitivity and specificity increased to 99% and 100%, respectively.

Cellular fatty acid methyl ester profiles as a tool in the differentiation of members of the genus Mycobacterium

The cellular fatty acid profiles of 84 strains belonging to 53 different species of the genus Mycobacterium were determined by gas liquid chromatography-mass spectrometry (GCMS). Two main types and four subtypes of fatty acid profiles were recognizable. The first main type is the G type, nominally referring to M. gordonae, members of which lack tuberculostearic acid or other 10-methyl branched-chain fatty acids, but contain normal saturated and unsaturated fatty acids. This type is further subdivided into the G alpha subtype that is characterized by 2-methyl tetradecanoic acid (2-Me-C14:0) as the only 2-methyl branched fatty acid. Strains belonging to the second main type, the T type, nominally referring to tuberculosis, contain tuberculostearic acid and other 10-methyl branched acids in addition to the normal saturated and unsaturated ones. This type has been further subdivided into three subtypes: the T alpha subtype that does not contain any 2-methyl branched fatty acids; the T beta subtype that contains both 2-methyl tetradecanoic (2-Me-C14:0) and 2,4-dimethyl tetradecanoic (2,4-DMe-C14:0) acids as 2-methyl branched fatty acids; the T gamma subtype which contains 2-methyl dodecanoic (2-Me-C12:0), 2,4-dimethyl dodecanoic (2,4-DMe-C12:0) and 2,4-dimethyl tetradecanoic (2,4-DMe-C14:0) acids as 2-methyl branched-chain acids. Fatty acid analysis showed a great homogeneity within the genus and the profiles produced were not very helpful in distinguishing between members of the genus Mycobacterium except for the identification of M. gordonae, M. kansasii, and M. gastri.

Phage susceptibility, enterotoxigenicity and antibiograms of Staphylococcus aureus strains isolated from human wounds and diarrhoea

The phage types, enterotoxigenicity and antibiograms of Staphylococcus aureus strains isolated from human diarrhoea and skin wounds in Nigeria were determined. Of 194 strains tested, 140 (72.2%) were typable using a combination of phages in the International Phage Set (IPS) for human strains of S. aureus and the bovine phage set. IPS phages lysed 118 (60.8%) strains while 96 (49.5%) were susceptible to bovine phages. S. aureus strains from adult diarrhoea were significantly (P less than or equal to 0.01; x2) more sensitive to bovine phages (52.8%) than to IPS human phages (16.7%). Strains isolated from wounds were however significantly (P less than or equal to 0.001; x2) more susceptible to IPS human phages (72.9%) than to bovine phages (41.5%). Phage group III strains were predominant amongst diarrhoeal isolates while wound strains were most susceptible to group II phages. Phage 119, a bovine phage, lysed all 19 strains of diarrhoeal origin sensitive to group M phages but all wound strains were resistant. Overall, 132 (68.0%) strains were enterotoxigenic producing staphylococcal enterotoxins A (SEA), B (SEB), C (SEC) or a combination of these. A majority of diarrhoeal strains elaborated SEC while SEB production was predominant amongst wound strains. Of the eight antimicrobial agents used, S. aureus strains were most resistant to penicillin (71.6%) and least to sulfamethoxazole/trimethoprim (1.0%). Occurrence of resistance to one or more antibiotics was higher amongst wound strains (97.5%) than amongst strains isolated from diarrhoea (52.6%). It was concluded that bovine phage 119 may be a useful epidemiologic marker for S. aureus strains of bovine origin associated with human diarrhoea in Nigeria. It is however difficult to ascribe any aetiological significance to these strains because other enteropathogens not assayed for may have been present.

Case Report. Maxillary sinus infection due to Emericella nidulans

Summary.  Fungal infections of the maxillary sinus are frequently caused by Aspergillus species, particularly A. fumigatus. In otherwise healthy persons there is an association with overfilling of dental root canals, when zinc‐containing filling materials were used. Below, a maxillary sinus aspergilloma is reported in a young immunocompetent female patient caused by Aspergillus (Emericella) nidulans.