Characteristics and outcome of 16 periprosthetic shoulder joint infections.

PURPOSE: Shoulder arthroplasties are increasingly performed, but data on periprosthetic joint infections (PJI) in this anatomical position are limited. We retrospectively investigated the characteristics and outcome of shoulder PJI after primary arthroplasty from 1998 to 2010 in a single centre. METHODS: Periprosthetic joint infection was defined as periprosthetic purulence, presence of sinus tract or microbial growth. A Kaplan-Meier survival method was used to estimate relapse-free survival of prosthesis. RESULTS: From 1,571 primary shoulder prostheses, we evaluated 16 patients with a PJI at different stages, i.e, early (n = 4), delayed (n = 6) and late (n = 6) infections. The median patient age was 67 (range 53-86) years, and 69 % were females. The most commonly isolated microorganism was Propionibacterium acnes in 38 % of patients (monobacterial in four and polymicrobial in two patients). In 14 of the 16 patients, surgical interventions consisting of debridement and implant retention (6 patients), exchange (7) and explantation (1) were performed. Four patients had a relapse of infection with P. acnes (n = 3) or Bacteroides fragilis (n = 1). The relapse-free survival of the prosthesis was 75 % (95 % confidence interval 46-90 %) after 1 and 2 years, 100 % in six patients following the treatment algorithm for hip and knee PJI and 60 % in 10 patients not followed up. All but one of the relapses were previously treated without exchange of the prosthesis. CONCLUSIONS: As recommended for hip and knee PJI, we suggest treating shoulder PJI with a low-grade infection by microorganisms such as P. acnes with an exchange of the prosthesis. Cohort studies are needed to verify our results.

Prospective evaluation of a semiquantitative dip slide method compared with quantitative bacterial cultures of BAL fluid.

BACKGROUND: Quantitative bacteriologic workup of BAL fluid (BALF) has evolved as a sensitive and specific technique for the diagnosis of bacterial pneumonia. Conventional quantitative cultures are expensive, time-consuming, and often unavailable on a 24-h basis. Therefore, we evaluated a dip slide method for the semiquantitative measurement of bacterial cultures in BALF specimens and compared the results with those from conventional quantitative cultures. METHODS: Fifty BALF specimens from 45 patients with suspected pulmonary infection were examined prospectively with both methods. We compared the microbiologic results of conventional quantitative cultures with those of the dip slide method that is commercially available for blood cultures. Cost-effectiveness analysis of both methods was performed. RESULTS: In 37 BALF specimens, 64 bacterial strains were detected with both techniques. The dip slide method and conventional cultures showed a high correlation with respect to the colony counts of the individual organisms per milliliter BALF (r=0.935; p= 0.0001) and the sum of colony counts in individual patients (r=0.947; p=0.0001). Although five strains were not detected by the dip slide technique, the diagnostic accuracy was not influenced. In 13 BALF samples, there was no growth of bacteria with both techniques. While the diagnostic yield of both methods was similar, the dip slide technique was 44 to 66% less expensive than conventional cultures. CONCLUSIONS: The examination of BALF with a clip slide method is highly comparable to conventional quantitative culture techniques, less expensive, and can be used independently of a specialized microbiology laboratory on a 24-h basis.

The role of two-segment bronchoalveolar lavage in the diagnosis of pulmonary infections.

STUDY OBJECTIVE: To determine if performing bronchoalveolar lavage (BAL) from more than one lung segment augments the diagnostic yield in patients with pulmonary infection. PATIENTS AND STUDY DESIGN: Seventy-six patients who underwent bisegmental BAL for the diagnosis or exclusion of pulmonary infection were studied prospectively. MAIN RESULTS: In patients with AIDS, the concentration of Pneumocystis carinii was higher in the upper lobes than in the middle lobes, regardless of whether the patients had been receiving pentamidine prophylaxis. In patients without HIV infection, the number of P carinii clusters was much lower. In 2 of 5 HIV-negative patients, P carinii organisms were detectable but in one of two lavage specimens, whereas in only 1 of 19 AIDS patients, P carinii organisms were not found in both lavaged segments. In bacterial pneumonia, BAL fluid from a segment of the radiologically most involved area had a much higher cell concentration, percentage of neutrophils, and concentration of bacteria than from the segment that was not or less severely involved on chest radiograph. In two of nine patients with AIDS and cytomegalovirus (CMV) pneumonia, cytopathogenic CMV effects were not found in both lavaged segments. In one of eight patients, mycobacteria could be cultured only from one of two radiologically involved segments. CONCLUSION: An increase in the diagnostic sensitivity by performing BAL in two lung segments is limited to cases where P carinii pneumonia is a relevant consideration in immunocompromised patients without HIV infection. In bacterial pneumonia, BAL can be performed in a single radiographically involved lung segment without a loss in diagnostic sensitivity. Since our study population of patients with CMV pneumonitis, mycobacterial infections, and fungal infections was small, no reliable conclusions are possible and BAL of more than one lung segment seems justified until more information is available.

Branhamella catarrhalis: fatty acid and lipopolysaccharide analysis of an atypical strain from blood culture.

A Branhamella catarrhalis-like organism was isolated from blood cultures; it was atypical in showing negative nitrate and nitrite and positive gamma-glutamylaminopeptidase reactions, in agglutinating with Neisseria meningitidis antisera, and in forming butyrous colonies. Cell-wall fatty-acid and lipopolysaccharide analysis provided evidence that this isolate was an atypical B. catarrhalis.

Genetic and molecular characterisation of resistance determinants in methicillin-resistant Staphylococcus-aureus.

A genetic analysis of resistance to antibiotics in methicillin-resistant Staphylococcus aureus was performed. Demonstration of plasmid-specific DNA either in transductants that had received antibiotic-resistance markers from multiply-resistant strains, or in segregants of methicillin-resistant strains that had lost unstable determinants except the one under study, indicated that markers of resistance to penicillin, chloramphenicol and neomycin are present on separate, mutually compatible plasmids. Absence of covalently closed circular DNA was demonstrated in transductants that were resistant to methicillin, tetracycline, erythromycin and streptomycin, as well as in segregants that had lost the penicillinase, chloramphenicol and neomycin plasmid, but were still resistant to methicillin, tetracycline, erythromycin, streptomycin and the sulphonamides. Analysis of plasmid DNA either in a 5-20% neutral sucrose gradient or by electron microscopy revealed the presence of three readily distinguishable plasmids. The molecular weights of these plasmids were estimated by comparing the sedimentation rate constants with those of known reference plasmids and by contour-length measurements. The molecular weight of the penicillinase plasmid was estimated to be 20 X 10(6) daltons, that of the chloramphenicol plasmid 3 X 10(6) daltons and that of the plasmid carrying the neomycin resistance marker 37 X 10(6) daltons.

Soft tissue infections of the upper extremities with special consideration of abscesses in parenteral drug abusers. A prospective study.

Despite surgical advances and new antibiotics, upper extremity infections continue to present a serious problem. Soft tissue infections of the upper extremities were prospectively examined to elucidate incidence, cause, bacterial pathogens involved, and treatment. Special attention was paid to infections associated with parenteral drug abuse. During an 18-month period all patients over 16 years of age presenting for treatment of an established infection were included in the study. Conservative treatment consisted of immobilization and antibiotics. Radical débridement with removal of all necrotic tissue was the guideline for operative care. In addition, for both regimens a penicillinase-resistant antibiotic was administered. A total of 415 patients (271 men and 144 women; mean age 36.7 +/- 14.5 years) were enrolled into the study, 55 of whom were parenteral drug abusers; 45 of these were HIV-reactive. Infections of fingers (excluding paronychia), paronychia and abscesses at injection sites were the most common diagnoses. Operative and conservative treatment were performed in 285 and 130 patients respectively. Staphylococcus and streptococcus species were the predominant organisms recovered from 212 specimens of pus. Anaerobic bacteria and yeasts were of minor importance. Therefore, a penicillinase-resistant antibiotic is a good initial choice.

Experience of gas-liquid chromatography in clinical microbiology.

In clinical microbiology, gas-liquid chromatography (GLC) is used mainly for the following applications: (1) demonstration of microbial metabolites in cultures: studies of short-chain fatty acids (chain length 2 to 6 carbon atoms) and of the non-volatile lactic and succinic acids are the basis of taxonomy of obligate anaerobes on the genus level. Demonstration of these compounds in spent culture media is also used for identification of anaerobic bacteria in the clinical laboratory. (2) Investigation of long-chain fatty acids of cell membranes and the cell wall: analysis of fatty acids with chain lengths of 9 to 20 carbon atoms are used primarily for taxonomic purposes. A practical application for use in clinical bacteriology is the Microbial Identification System (MIS) based on equipment built by Hewlett-Packard. Although this system is excellently suited for quantitative analysis of long chain fatty acids and gives valuable preliminary or confirmative information, it often requires additional testing for identification of bacteria to species level. (3) Direct rapid diagnosis of infection: demonstration of metabolic products in body fluids can be of value in infections with anaerobes (demonstration of fatty acids) and yeasts (sugars). GLC combined with mass spectrometry or frequency-pulsed electron capture GLC techniques have been applied to studies of sera, fecal specimens, and cerebrospinal fluids. These latter applications are still in an experimental stage. However, the rapid diagnosis of tuberculosis directly from cerebrospinal fluid and sputum is well advanced. The potential of direct diagnosis without the resort to cultures warrants continued research with these techniques.

[The sensitivity of anaerobic bacteria to chemotherapeutic agents (Zurich, 1991)]. / Die Empfindlichkeit anaerober Bakterien gegen Chemotherapeutika (Zürich, 1991).

There have been numerous reports on resistance of anaerobic bacteria against antimicrobial agents. Therefore, to assess the situation in Zurich, 187 anaerobic strains of various bacterial genera, isolated from clinical specimens during winter 1990/91, were tested for their susceptibility to antimicrobial agents active against anaerobic bacteria. Besides the Bacteroides fragilis group, which is naturally resistant against penicillin, 30% of isolates of other Bacteroides species were also resistant against penicillin. In general, anaerobes have remained susceptible to cefoxitin, chloramphenicol, clindamycin, imipenem, the 5-nitroimidazoles (metronidazole, ornidazole) as well as combinations of beta-lactam antibiotics with beta-lactamase inhibitors (clavulanic acid, sulbactam and tazobactam). Because rare strains resistant against cefoxitin, clindamycin and beta-lactams plus beta-lactamase inhibitors can be found, at least isolates from specific clinical situations should be tested for antimicrobial susceptibility. These are strains isolated from patients with brain abscess, endocarditis, osteomyelitis, arthritis, infected implants and prosthesis as well as those from persisting or recurrent bacteremia. Because the agar diffusion test yields unreliable results, minimal inhibitory concentration should be determined. Maybe the new 'E test' or the spiral gradient procedure can be used after evaluation.

[Bacterial sensitivity to chemotherapeutic agents (Zurich, 1990)]. / Die Empfindlichkeit von Bakterien gegen Chemotherapeutika (Zürich, 1990).

This paper describes the incidence of susceptibility of gram-negative and positive bacteria towards antibacterial agents. The data are based on all susceptibility tests performed at the Department of medical microbiology of the University of Zurich. The evaluation of the results from 1975 to 1990 shows that susceptibilities against the antimicrobial agents tested have not changed markedly in this period. These tables may be a help for the physician in his decision for a "calculated chemotherapy" of bacterial infections.

[The problems of rapid diagnosis of Clostridium difficile as causative agent of antibiotic-associated pseudomembranous colitis]. / Zur Problematik der Schnelldiagnose von Clostridium difficile als Erreger der Antibiotika-assoziierten pseudomembranösen Kolitis.

This paper compares three common methods for the detection of Clostridium difficile, i.e. latex agglutination, culture and cytotoxic activity. The sensitivity of the latex agglutination test alone is 70%, of the culture 100% and of the cytotoxin test 66%. Specificities are 93, 96 and 100%, respectively. The latex agglutination has positive and negative predictive values of 58 and 96%; the respective values for the culture are 77 and 100%, for the cytotoxin assay 100 and 96%. Whereas all tests are fairly reliable for the exclusion of diarrhea associated to Clostridium difficile (CAD), the positive predictive values of latex agglutination and culture are too low. If one requests two positive test results for proof of CAD, about two third of all cases are detected by any combination of laboratory tests, while the specificity approaches 100%. We recommend that two of the three tests are performed; the choice is influenced by the possibilities of the laboratory.

[Bacterial susceptibility to chemotherapeutic agents (Zurich, 1987)]. / Die Empfindlichkeit von Bakterien gegen Chemotherapeutika (Zürich, 1987).

This paper describes the frequency of susceptibility of Gram-positive and Gram-negative bacteria against antibacterial agents. The data are based on all susceptibility tests performed at the Department of Medical Microbiology of the University of Zurich. The evaluation of the results from 1975 to 1987 shows that susceptibility against standard antimicrobial agents has not decreased in this period. These tables may be a valuable help for the physician in his decision for a "calculated chemotherapy".

[Multicenter evaluation of oral antibiotics: resistance behavior in 5 Swiss centers]. / Multizentrische Evaluation oraler Antibiotika: Resistenzverhalten in fünf schweizerischen Zentren.

The susceptibility of 2196 fresh clinical isolates to twelve different oral compounds was assessed in five Swiss microbiology institutions during summer 1992. A standardized microdilution system including all other material necessary was employed to assess the antibacterial activity of penicillin G, ampicillin, ampicillin + sulbactam, amoxycillin + clavulanic acid, cefadroxil, cephalexin, cefaclor, cefuroxime, cefetamet, doxycycline, erythromycin and clindamycin. The aminopenicillins (including the beta-lactamase inhibitor combinations) were highly active against the streptococci, in combination with a beta-lactamase inhibitor they covered the majority of the bla+ E. coli and Proteus mirabilis and between 60 to 80% of the Klebsiella spp. and Proteus vulgaris isolates. All the cephalosporins exhibited good activity against the streptococci, they were active against Gram-negative fermentative rods to a varying degree. Cefetamet was also active against many cefaclor and cefuroxime-resistant isolates. A considerable part of the species studied exhibited resistance to doxycycline; the observed resistance of S. agalactia, P. mirabilis, and Morganella morganii agreed with previous findings. Most of the Streptococcus spp. were inhibited by erythromycin and clindamycin. There were only single penicillin resistant S. pneumoniae isolates in the five Swiss centers. Taking account of the above particulars the epidemiology of antimicrobial resistance in Switzerland can be considered satisfactory.

[Antimicrobial resistance among E. coli in urinary specimens: prevalence data from three laboratories in Zurich between 1985 and 2010]. / Antibiotikaresistenzen von E.coli in Urinproben: Prävalenzdaten dreier Laboratorien im Raum Zürich von 1985 bis 2010.

Urinary tract infections in women are common. Drug resistance among Escherichia coli, the most frequent uropathogen, has increased worldwide. In a prevalence study we investigated the local antibiotic susceptibility of this microorganism in urinary specimens of three laboratories in Zurich. Resistance rates against trimethoprim-sulfamethoxazole 2010 were 28%, 16% against quinolones and 16% against amoxicillin/clavulanic acid. Resistance prevalence for nitrofurantoin and fosfomycin were low with 3,6%, resp. 0,7%. The rate of extended-spectrum beta-lactamase-producing E. coli has rapidly increased to 4,3% in 2010. Based on this data and according to the international guidelines for the treatment of uncomplicated cystitis, therapy with trimethoprim-sulfamethoxazole and quinolones are no longer recommended. Nitrofurantoin and Fosfomycin are an appropriate choice. Microbiological testing is advised.

Road factors and bicycle-motor vehicle crashes at unsignalized priority intersections.

In this study, the safety of cyclists at unsignalized priority intersections within built-up areas is investigated. The study focuses on the link between the characteristics of priority intersection design and bicycle-motor vehicle (BMV) crashes. Across 540 intersections that are involved in the study, the police recorded 339 failure-to-yield crashes with cyclists in four years. These BMV crashes are classified into two types based on the movements of the involved motorists and cyclists: • type I: through bicycle related collisions where the cyclist has right of way (i.e. bicycle on the priority road); • type II: through motor vehicle related collisions where the motorist has right of way (i.e. motorist on the priority road). The probability of each crash type was related to its relative flows and to independent variables using negative binomial regression. The results show that more type I crashes occur at intersections with two-way bicycle tracks, well marked, and reddish coloured bicycle crossings. Type I crashes are negatively related to the presence of raised bicycle crossings (e.g. on a speed hump) and other speed reducing measures. The accident probability is also decreased at intersections where the cycle track approaches are deflected between 2 and 5m away from the main carriageway. No significant relationships are found between type II crashes and road factors such as the presence of a raised median.

Characteristics and outcome of 27 elbow periprosthetic joint infections: results from a 14-year cohort study of 358 elbow prostheses.

Elbow arthroplasty is increasingly performed in patients with rheumatic and post-traumatic arthritis. Data on elbow periprosthetic joint infection (PJI) are limited. We investigated the characteristics and outcome of elbow PJI in a 14-year cohort of total elbow arthroplasties in a single centre. Elbow prosthesis, which were implanted between 1994 and 2007 at Schulthess Clinic in Zurich, were retrospectively screened for infection. PJI was defined as periprosthetic purulence, the presence of sinus tract or microbial growth. A Kaplan-Meier survival method and Cox proportional hazard analysis were performed. Of 358 elbow prostheses, PJI was identified in 27 (7.5%). The median patient age (range) was 61 (39-82) years; 63% were females. Seventeen patients (63%) had a rheumatic disorder and ten (37%) had osteoarthritis. Debridement and implant retention was performed in 78%, followed by exchange or removal of the prosthesis (15%) or no surgery (7%).The relapse-free survival (95% CI) was 79% (63-95%) after 1 year and 65% (45-85%) after 2 years. The outcome after 2 years was significantly better when patients were treated according to the algorithm compared to patients who were not (100% vs. 33%, p <0.05). In 21 patients treated with debridement and retention, the cure rate was also higher when the algorithm was followed (100% vs. 11%, p <0.05). The findings of the present study suggest that the treatment algorithm developed for hip and knee PJI can be applied to elbow PJI. With proper patient selection and antimicrobial therapy, debridement and retention of the elbow prosthesis is associated with good treatment outcome.

[Rapid diagnosis of anaerobic infections by means of the direct gaschromatographic study of clinical materials]. / Schnelldiagnose anaerober Infektionen mit der direkten gaschromatographischen Untersuchung von klinischem Material.

Current methods for isolation and identification of obligately anaerobic bacteria are laborious and time-consuming. Direct gas-liquid chromatography of purulent and serous specimens for short-chain fatty acids allows a presumptive diagnosis of anaerobic infection. Good correlation was found for the cultural recovery of anaerobic bacteria and the presence of propionic acid in concentrations of greater than or equal to 1 muMol/ml, isobutyric, butyric, isovaleric, valeric, isocaproic and caproic acid at greater than or equal to 0.1 muMol/ml, and succinic acid at greater than or equal to 2 muMol/ml (either as single acids or in combination). Specimens yielding no anaerobic bacteria in culture contained only acetic, lactic and small amounts of succinic acid, but none of the volatile acids.

In vitro susceptibility of anaerobes to co-trimoxazole.

The minimal inhibitory concentrations (MIC) of sulfamethoxazole and trimethoprim against 144 strains of obligately anaerobic bacteria were determined on supplemented Diagnostic Sensitivity Test (Oxoid) agar or broth. 58% of the strains were susceptible to sulfamethoxazole alone (MIC less than or equal to 16 micrograms/ml), only 12% were susceptible to trimethoprim alone (less than or equal to 1 microgram/ml), and 85% were susceptible to the combination of sulfamethoxazole plus trimethoprim (less than or equal to 16 micrograms/ml) at a ratio of 19:1. All 45 strains of the Bacteroides fragilis group were susceptible to the combination. At a ratio of 1:1, 78% of the strains showed synergistic activity, at a ratio of 16:1 there were synergism in 54% of the strains. When the strains were tested by a modification of the broth-disc method in Diagnostic Sensitivity Test broth, there was over 98% correlation with the MIC. There was poor correlation between inhibition zone diameters by an agar diffusion method and MIC.

[Bacteriological diagnosis of anaerobic infections]. / Die bakteriologische Diagnose anaerober Infektionen.

To avoid false positive results it is very important that specimens for culture of anaerobic bacteria are not contaminated with normal flora from the skin or mucous membranes (mouth, intestinal tract, genital tract). The specimen should be transported to the laboratory as fast as possible without exposure to oxygen. Liquid specimens, such as aspirates, are superior to swabs. For rapid presumptive diagnosis suitable methods are gram stain and direct gas-liquid chromatography for fatty acids. Culture is laborious and time-consuming.