Epidemic spread of a single clone of methicillin-resistant Staphylococcus aureus among injection drug users in Zurich, Switzerland

We describe an outbreak of methicillin-resistant Staphylococcus aureus (MRSA) among injection drug users (IDUs). From August 1994 through December 1999, we registered 31 IDUs with MRSA infections (12 with soft-tissue infection, 7 with pneumonia [fatal in 1], 7 with endocarditis [fatal in 1], 2 with osteomyelitis, 2 with septic arthritis, and 1 with ulcerative tonsillitis), with a marked increase in the number of IDUs registered during 1998 and 1999. Of 31 patients, 15 (48%) were infected with human immunodeficiency virus. A point-prevalence study among IDUs who frequented outpatient facilities in Zurich revealed an MRSA carriage rate of 10.3% (range, 0%-28.6%) in various facilities. In all but 1 case, pulsed-field gel electrophoresis banding patterns of isolates obtained from these patients were indistinguishable from isolates of the initial 31 IDUs registered. Risk factors for MRSA carriage were disability and prior hospitalization in a hospice. In summary, MRSA became endemic in IDUs in Zurich as a result of the spread of a single clone. This clone caused major morbidity and was responsible for a lethal outcome in 2 cases.

International multicenter evaluation of latex agglutination tests for identification of Staphylococcus aureus

A newly marketed rapid agglutination kit for the identification of Staphylococcus aureus, Slidex Staph Plus (bioMérieux), was compared to Staphaurex Plus (Murex Diagnostics) and Pastorex Staph-Plus (Sanofi Diagnostics Pasteur). The study took place in three clinical microbiology laboratories in three different European countries. A total of 892 staphylococcal isolates, including 278 methicillin-sensitive S. aureus (MSSA) isolates, 171 methicillin-resistant S. aureus (MRSA) isolates, and 443 coagulase-negative staphylococcal isolates, were analyzed. The sensitivities (MSSA/MRSA) and specificities, respectively, were 98. 2% (98.9%/97.1%) and 98.9% for Slidex Staph Plus, 98.2% (98.2%/98. 2%) and 96.2% for Staphaurex Plus, and 98.7% (98.6%/98.8%) and 95.7% for Pastorex Staph Plus. The specificity of the Slidex Staph Plus kit was statistically significantly higher than the specificities of Staphaurex Plus and Pastorex Staph-Plus. The Slidex Staph Plus is a very reliable test for the identification of S. aureus.

Intestinal infection due to enteroaggregative Escherichia coli among human immunodeficiency virus-infected persons

To investigate the pathogenic role of enteroaggregative Escherichia coli (EAggEC) among human immunodeficiency virus-infected persons, 111 outpatients with and 68 without diarrhea were evaluated. Examination of stool samples included the HeLa cell adherence assay and an EAggEC polymerase chain reaction (PCR) assay using primers complementary for the plasmid locus CVD432. The pCVD432 genotype, adherence phenotype, and patient characteristics were correlated with occurrence of diarrhea by multivariate analyses. EAggEC PCR and adherence assays were positive in 7 (6%) and 24 (22%) patients with diarrhea and in 1 (1%) and 21 (31%) asymptomatic control patients, respectively. Clinical manifestations associated with EAggEC PCR-positive isolates were nonspecific; EAggEC infections were independent of CD4 lymphocyte counts. Of the pCVD432 genotype, 5 (71%) of 7 were resistant to cotrimoxazole and ampicillin, and 1 strain was resistant to ciprofloxacin. Overall, pCVD432 PCR-positive E. coli was the most prevalent intestinal organism associated with diarrhea. The adherence assay results did not correlate with diarrhea.

Streptobacillus moniliformis endocarditis in an HIV-positive patient

Streptobacillus moniliformis is the causative agent of rat bite fever, with endocarditis being a rare but well-documented complication. We report the case of an HIV-positive man who acquired S. moniliformis endocarditis through a rat bite. No predisposing cardiac lesion was known. He was treated with ceftriaxone 2 g/day i.v. for 3 weeks, gentamicin 120 mg/day i.v. for 2 weeks and penicillin 24x10(6) units/day for 1 week. At the end of the antibiotic therapy he suffered a generalized Candida albicans infection, which was treated with fluconazole for 1 week. He was subsequently discharged in a satisfactory condition.

Brevibacterium casei sepsis in an 18-year-old female with AIDS

Brevibacterium sp. was isolated from the blood of an acutely ill 18-year-old female with AIDS. The isolate was identified as Brevibacterium casei by use of carbohydrate assimilation tests. Treatment was successful with intravenously administered ciprofloxacin. To our knowledge, this is the first report of sepsis caused by B. casei in a human immunodeficiency virus-infected patient.

Diagnosis of Cardiobacterium hominis endocarditis by broad-range PCR from arterio-embolic tissue

A case of culture-negative endocarditis is reported, in which the diagnosis of Cardiobacterium hominis endocarditis was made from arterio-embolic tissue removed by percutaneous transluminal embolectomy by broadrange polymerase chain reaction amplification of the 16 rRNA gene, followed by single-strand sequencing. The use of this technique to identify etiologic agents from arterio-embolic material has not been reported so far. A serologic assay employing complement fixation against a crude antigen of Cardiobacterium hominis confirmed the diagnosis of endocarditis caused by this unusual fastidious etiologic agent.

Infection of a hip prosthesis by Actinomyces naeslundii

We present the case of a 77-year-old woman who developed an Actinomyces naeslundii infection of a hip prosthesis. The isolate grew well aerobically with 5% CO(2). Possible diagnostic problems may arise in the microbiological laboratory because aerobic growth is not sufficiently accounted for in some of the traditional identification schemes and commercial test kits. Therefore, besides presenting an unusual pathogen in this setting, this report focuses on possible diagnostic problems in the microbiological laboratory.

Retroperitoneal abscess and bacteremia due to Mycoplasma hominis in a polytraumatized man

We report a case of a retroperitoneal abscess due to Mycoplasma hominis in a young polytraumatized man who developed septicemia under treatment with rifampin and flucloxacillin. M. hominis was recovered from blood cultures as well as from the abscess near the left iliac spine. After 10 days of therapy with clindamycin the patient improved, and intraoperatively taken swabs were culture negative but still positive by PCR.

Characterization of blood culture isolates of Streptococcus dysgalactiae subsp. equisimilis possessing Lancefield's group A antigen

For three human blood culture isolates of beta-hemolytic streptococci with Lancefield's serogroup A antigen, phylogenetic analysis of the 16S rRNA genes confirmed biochemical identification as Streptococcus dysgalactiae subsp. equisimilis. Genes encoding M or M-like proteins, which are considered to be major virulence determinants in streptococci, were detected in all of these strains. Our data clearly demonstrate that for beta-hemolytic streptococci, the species assignment should not be based on the results of serogrouping alone.

The role of syringe filters in harm reduction among injection drug users

OBJECTIVES

Three filters were tested for in situ efficacy in reducing bacterial contamination associated with injection drug use.

METHODS

In a self-matched control design with blinded laboratory testing, injection drug users were asked to use 3 filters in random succession when loading their syringes with drug solute.

RESULTS

The 0.22-micron filter proved significantly better than both the cigarette filter (relative risk [RR] = 18.0) and the 20-micron filter (RR = 4.5) in rendering syringes bacteria-free.

CONCLUSIONS

The 15- to 20-micron syringe filter currently provided injection drug users in Switzerland does not significantly reduce contamination associated with common bacterial infections among users. Filters with pore width 1/100th as large are recommended.

Enteric infections and diarrhea in human immunodeficiency virus-infected persons: prospective community-based cohort study. Swiss HIV Cohort Study

BACKGROUND

Persons infected with human immunodeficiency virus (HIV) are at increased risk for diarrhea and enteric infections. We studied (1) the epidemiology of enteric pathogens associated with diarrhea, (2) the diagnostic yield of stool examination and endoscopic evaluation, (3) risks to develop diarrhea, and (4) the impact of diarrhea on patients' survival.

METHODS

A total of 1933 participants in the Swiss HIV Cohort Study were prospectively followed up for a median of 25.5 months. A total of 560 diarrheal episodes were evaluated by standardized stool examination. Endoscopic evaluation was performed in 25% of patients with chronic diarrhea.

RESULTS

The incidence of diarrhea was 14.2 per 100 person-years (95% confidence interval, 13.0-15.4). Among patients with CD4 cell counts below 0.05 x 10(9)/L, the probability to develop diarrhea within 1, 2, and 3 years was 48.5%, 74.3%, and 95.6%, respectively. The risk to develop diarrhea was increased among patients with severe immunodeficiency, homosexual men, and patients taking antiretroviral therapy. Pneumocystis carinii chemoprophylaxis did not reduce the risk of diarrhea. Diarrhea was an independent negative predictor of survival. Enteric pathogens were detected in 16.5% of 212 acute diarrheal episodes and in 46% of 348 chronic diarrheal episodes. The sensitivity of histological and stool examination was similar except for the diagnosis of intestinal cytomegalovirus infection and leishmaniasis, which required invasive evaluation.

CONCLUSIONS

Intestinal infections were diagnosed in less than 50% of chronic diarrheal episodes. The prevalence of enteric pathogens tended to decrease during the observation period, possibly because of improved antiretroviral therapy. Endoscopic evaluation did not improve the diagnostic yield compared with stool examination except for the diagnosis of cytomegalovirus enteritis and leishmaniasis.

False-positive beta-lactamase results with Staphylococcus lugdunensis in the Vitek AutoMicrobic system

The Vitek AutoMicrobic system in combination with the Gram-positive susceptibility card detects beta-lactamase in staphylococci by utilizing penicillin as the substrate coupled with oxacillin as an inducer. The beta-lactamase activity of 21 clinical isolates and two reference strains of Staphylococcus lugdunensis was determined with this automated system and compared with a liquid nitrocefin assay after induction with oxacillin. Eight (38%) clinical isolates and the reference strain ATCC 49576 of S. lugdunensis showed production of beta-lactamase in both tests. Thirteen (62%) clinical isolates and the type strain ATCC 43809 were nitrocefin-negative. The Vitek AutoMicrobic system reported false-positive beta-lactamase results for 9 of those 13 isolates and for the type strain of S. lugdunensis. Results for disk diffusion (ampicillin) were concordant with the nitrocefin assay. With one exception, the MICs for penicillin of the nitrocefin-negative strains were in the equivocal range of 0.06-0.12 mg/l according to NCCLS. However, none of the nitrocefin-negative and Vitek-positive strains revealed any of the known staphylococcal genes for beta-lactamase as investigated by Southern hybridization, supporting the fact that false-positive beta-lactamase results may occur in the Vitek AutoMicrobic system. We conclude from our data that it may be justified to include S. lugdunensis in the quality control of Vitek cards containing beta-lactamase tests.

Group G streptococcus sacroilitis with sepsis in a 15-y-old adolescent

Group G streptococci cause invasive infections of different tissues. Most infected patients have underlying diseases and are of adult age. Invasive group G streptococcal infections rarely occur in childhood and adolescence. A 15-y-old boy with a beta-haemolytic group G streptococcus sacroiliitis, sepsis and secondary pulmonary manifestations resembling an acute respiratory distress syndrome is described.

Septicemia caused by dysgonic fermenter 3 in a severely immunocompromised patient and isolation of the same microorganism from a stool specimen

Dysgonic fermenter 3 (DF-3)-associated bacteremia occurred in a febrile patient with acute myelocytic leukemia during aplasia. Another DF-3 isolate, identical by ribotyping, was grown 10 weeks later from stool collected in the absence of diarrhea. This is the first case in which DF-3 was isolated from blood and stool specimens from the same patient.

Endocarditis due to Aerococcus urinae: diagnostic tests, fatty acid composition and killing kinetics

Two cases of Aerococcus urinae endocarditis are reported. The organism is not included in any database of commercial identification systems at this time. Formation of tetrades and positive reactions for leucine arylamidase and beta-glucuronidase pointed strongly to A. urinae. The cellular fatty acid pattern was similar to that of Aerococcus viridans, with predominantly C16:0, C18:1 omega 9c and C18:0; the presence of C18:1 omega 7t differentiated our isolates from A. viridans and can support the diagnosis of A. urinae. Furthermore, susceptibility to penicillin but resistance to cotrimoxazole represents a pattern opposite to that of A. viridans. Minimal inhibition concentrations of gentamicin and netilmicin were < or = 64 mg/l but those of tobramycin were > or = 256 mg/l. Penicillin combined with either gentamicin or netilmicin showed distinct synergy in killing kinetics. These combinations seem to be the appropriate regimen to treat A. urinae endocarditis.

[Severity of respiratory syncytial virus infection influenced by clinical risk factors and subtype A and B in hospitalized children]

BACKGROUND

Since it is possible to identify the subgroups of RSV, A-subtype and B-subtype, there are findings indicating that the subtype may influence severity of RSV infection. Our study was designed to assess the hypothesis that A-subtype infections were more severe than B-subtype infections among hospitalized children.

PATIENTS

All medical records of patients hospitalized with RSV infection between March 1990 and March 1993 were reviewed. A total of 107 children with proven RSV infection were identified.

METHODS

Nasal waste specimens for culture were obtained from infants with suspected RSV infection. Subtype determination was done on frozen virus cultures. The following risk factors were defined: age < or = 3 months, weight < 5 kg, prematurity and underlying cardiac or respiratory disease and immune deficiency. To analyse the relationship between risk factors, subtype and severity a multivariate analysis was performed. Severity was measured by clinical observations as following: pH, PCO2, SaO2, oxygen supplementation, history of apnea and length of hospital stay.

MAIN RESULTS

Of the enrolled patients 11 had underlying disease and 17 were premature. The age range was 1 week to 4.2 years, median 3.5 months. 46 children were younger than 3 months, 33 had a weight of less than 5 kg. The isolates of 84 children were typeable: 63 isolates were subtype A and 21 subtype B. Underlying disease and prematurity were associated with SaO2 < 87% (p = 0.003) and oxygen supplementation (p = 0.017). A weight of less than 5 kg was correlated with a PCO2 > or = 50 mmHg. The RSV subtype was not significantly correlated with severity.

CONCLUSIONS

RSV infection even in very young children is predominantly influenced by underlying disease, prematurity and weight. The RSV subtype was no independent risk factor for an increased morbidity in this retrospective study. Therefore, in our opinion, RSV subtype is less meaningful to predict the severity of RSV infection than known risk factors.

Enteroaggregative Escherichia coli as a potential cause of diarrheal disease in adults infected with human immunodeficiency virus

Stools of 68 human immunodeficiency virus (HIV)-infected adults with diarrhea and 60 without diarrhea were examined for enteroaggregative Escherichia coli (EAggEc) by HeLa cell adherence assay. EAggEc were present in stools of 30 patients with and 18 without diarrhea (P = .05). CD4 cell counts of patients with EAggEc and diarrhea were significantly lower than those of patients with EAggEc without diarrhea (P = .02). There was no difference in the mean duration of diarrheal symptoms or in the number of stools per day between patients with EAggEc and those without. None of the EAggEc strains were positive by polymerase chain reaction for adherence fimbria, but 11 strains were positive for EAggEc heat-stable toxin EAST/1. Of the EAggEc strains, 51% were resistant to trimethoprim-sulfamethoxazole and 65% were resistant to ampicillin. EAggEc may be a pathogen in HIV-infected patients with diarrhea; HIV-infected patients with EAggEc appear to be more symptomatic when HIV disease is more advanced.

Antibody response in six HACEK endocarditis cases under therapy

The antibody response to bacteria of the so-called HACEK group, i.e. Haemophilus spp., Actinobacillus actinomycetemcomitans, Cardiobacterium hominis, Eikenella corrodens and Kingella kingae, was measured in sera of six patients with endocarditis. The corresponding isolates from their blood cultures were identified by conventional methods, including reactions for nitrate reduction and catalase as well as acid production from sugars. Crude antigens were prepared by glycine extraction and sonification of the blood culture isolates, and used to determine titers by complement fixation. A patient with Haemophilus parainfluenzae bacteremia received a short course of antibiotic therapy, and relapsed with spondylitis and endocarditis 5 months later. Titers of sera against his own isolate rose from 1:40 to 1:320 and fell to 1:40 after therapy within one year. A patient with C. hominis endocarditis had a similarly prolonged course. The complement fixation titer against his own isolate was already 1:240 before antibiotics were administered. Another patient with C. hominis endocarditis presented a titer of 1:320 2 weeks after the diagnosis. These three patients revealed C-reactive protein values over 50 mg/l in the first serum sample. Decrease of both antibody titers and C-reactive protein values correlated with clinical improvement. Two patients with prosthetic valve replacement 5 months earlier developed C. hominis and K. kingae endocarditis, respectively. At admission, C-reactive protein values were 64 and 82, respectively, and therapy was instituted immediately. The first sera were received 3 and 6 weeks, respectively, after isolation of the corresponding blood culture isolates and revealed already low titers, i. e. 1:80 and 1:60, respectively. A woman with A. actinomycetemcomitans endocarditis received immediate therapy and did not develop titers against her own isolate. CRP was 100 at admission and remained over 50 5 weeks later. We conclude that the complement fixation assay with individual antigen preparations was easy to perform and allowed monitoring of the antibody response in 5 of 6 HACEK endocarditis cases under therapy, but the usefulness of this method to find culture-negative HACEK endocarditis needs to be established.

[Sensitivity of bacteria to therapeutic drugs (Zurich 1996)]

This paper describes the frequency of susceptibility of Gram-negative and Gram-positive bacteria against antibacterial agents. The data are based on all susceptibility tests performed in 1996 at the Department of Medical Microbiology of the University of Zurich and at the private medical laboratory "medica" in Zurich. The evaluation of the results from 1975 to 1996 shows that susceptibilities against the antimicrobial agents tested have not changed markedly in this period with few exceptions. The tables may be a help for the physician in his decision for a "calculated chemotherapy" of bacterial infections.

Serological evidence of human granulocytic ehrlichiosis in Switzerland

To investigate whether human granulocytic ehrlichiosis (HGE) is prevalent in Switzerland, 1515 human serum samples from individuals with different risks for tick exposure were tested for antibodies to Ehrlichia phagocytophila, a surrogate marker of the agent of HGE. The distribution of titres showed marked differences between sera of individuals with no or low risk for tick exposure and those with a high risk. The results of serological testing provided evidence of HGE in Switzerland as well as evidence of two types of coinfections: those with the agent of HGE and Borrelia burgdorferi, and those with the agent of HGE and the central European tickborne encephalitis virus.

IgM to Bartonella henselae in cat-scratch disease and during acute Epstein-Barr virus infection

The diagnostic value of IgM to Bartonella henselae was evaluated in 20 children with cat-scratch disease (CSD) and controls consisting of 20 blood donors and 20 children with enlarged lymph nodes without CSD by two indirect immunofluorescence assays (IFA). One was based on B. henselae cocultivated with Vero cells (host cell-associated IFA), and the other on B. henselae grown on agar (host cell-free IFA). With the host cell-associated IFA, 18 of 20 children with CSD revealed IgM, whereas only 14 did so with the host cell-free IFA. Sera of two blood donors as well as sera from three children with enlarged lymph nodes without CSD showed also positive IgM to cell-associated B. henselae. This study reveals that the IFA applied had sensitivities of 70-90% and specificities of 87.5-100% for detecting IgM to B. henselae. Additionally, 20 patients with IgM to Epstein-Barr virus (EBV) capsid antigen were tested for IgM to B. henselae. Sera of 16 and 9 of these patients revealed IgM to B. henselae with the host cell-associated and the host cell-free IFA, respectively. Using Western blot these sera were demonstrated to react against linearized proteins of Vero cells and of B. henselae. Thus, since acute EBV infection may substantially reduce the specificity of B. henselae-specific IgM tests, we conclude that diagnosis of CSD should be confirmed by a significant IgG titer to B. henselae or by detection of this pathogen.

[Decreased penicillin sensitivity of pneumococci]

The mechanism of penicillin-resistance of Streptococcus pneumoniae involves the development of altered forms of penicillin-binding proteins (PBPs) that have a decreased affinity for penicillin. PBPs are involved in the assembly of the cell wall. Normal forms of PBPs are inhibited by penicillin but altered forms are not. It appears that the altered PBP genes arose by interspecies recombinational events in which segments of the PBPs structural genes had been replaced by regions derived from PBP genes of oral streptococcal species. Altered PBP genes of penicillin-resistant pneumococci can be spread horizontally to sensitive pneumococci by transformation. Highly resistant pneumococci have several altered PBPs and also show resistance to the third-generation cephalosporins and other antibiotics. Some clones of resistant pneumococci seem to have an increased epidemic potential to spread. In Austria, Germany, Italy, and Switzerland approximately 95% of pneumococci are still penicillin-sensitive. However, an increase of the highly resistant pneumococci would change the empirical therapy of severe pneumococcal infections in the near future. Reasonable use of antimicrobials might reduce the selective antimicrobial pressure and the spread of penicillin-resistant strains.