Reno Frei

Throat Swabs Are Necessary to Reliably Detect Carriers of Staphylococcus aureus

The anterior nares are the most important screening site of colonization with Staphylococcus aureus. We screened 2966 individuals for S. aureus carriage with swabs of both nares and throat. A total of 37.1% of persons were nasal carriers, and 12.8% were solely throat carriers. Screening of throat swabs significantly increases the sensitivity of detection among carriers by 25.7%.

Highly Effective Regimen for Decolonization of Methicillin-Resistant Staphylococcus aureus Carriers

OBJECTIVE To evaluate the efficacy of a standardized regimen for decolonization of methicillin-resistant Staphylococcus aureus (MRSA) carriers and to identify factors influencing decolonization treatment failure. DESIGN Prospective cohort study from January 2002 to April 2007, with a mean follow-up period of 36 months. SETTING University hospital with 750 beds and 27,000 admissions/year. PATIENTS Of 94 consecutive hospitalized patients with MRSA colonization or infection, 32 were excluded because of spontaneous loss of MRSA, contraindications, death, or refusal to participate. In 62 patients, decolonization treatment was completed. At least 6 body sites were screened for MRSA (including by use of rectal swabs) before the start of treatment. INTERVENTIONS Standardized decolonization treatment consisted of mupirocin nasal ointment, chlorhexidine mouth rinse, and full-body wash with chlorhexidine soap for 5 days. Intestinal and urinary-tract colonization were treated with oral vancomycin and cotrimoxazole, respectively. Vaginal colonization was treated with povidone-iodine or, alternatively, with chlorhexidine ovula or octenidine solution. Other antibiotics were added to the regimen if treatment failed. Successful decolonization was considered to have been achieved if results were negative for 3 consecutive sets of cultures of more than 6 screening sites. RESULTS The mean age (+/- standard deviation [SD]) age of the 62 patients was 66.2 +/- 19 years. The most frequent locations of MRSA colonization were the nose (42 patients [68%]), the throat (33 [53%]), perianal area (33 [53%]), rectum (36 [58%]), and inguinal area (30 [49%]). Decolonization was completed in 87% of patients after a mean (+/-SD) of 2.1 +/- 1.8 decolonization cycles (range, 1-10 cycles). Sixty-five percent of patients ultimately required peroral antibiotic treatment (vancomycin, 52%; cotrimoxazole, 27%; rifampin and fusidic acid, 18%). Decolonization was successful in 54 (87%) of the patients in the intent-to-treat analysis and in 51 (98%) of 52 patients in the on-treatment analysis. CONCLUSION This standardized regimen for MRSA decolonization was highly effective in patients who completed the full decolonization treatment course.

Rapid and Reliable Diagnostic Algorithm for Detection of Clostridium difficile

ABSTRACT We evaluated a two-step algorithm for detection of Clostridium difficile in 1,468 stool specimens. First, specimens were screened by an immunoassay for C. difficile glutamate dehydrogenase antigen (C.DIFF CHEK-60). Second, screen-positive specimens underwent toxin testing by a rapid toxin A/B assay (TOX A/B QUIK CHEK); toxin-negative specimens were subjected to stool culture. This algorithm allowed final results for 92% of specimens with a turnaround time of 4 h.

Killing of nongrowing and adherent Escherichia coli determines drug efficacy in device-related infections.

Antimicrobial therapy of device-related infections often fails, despite the in vitro susceptibility of the infecting strain. Therefore, alternative laboratory-based in vitro tests are required to predict the outcome. Fleroxacin, ciprofloxacin, aztreonam, and co-trimoxazole were tested against Escherichia coli ATCC 25922 in vitro and in the tissue-cage animal model. The importance of early treatment was evaluated by starting the drugs either 30 min before or 4, 12, and 24 h after bacterial challenge. Results were compared with the in vitro drug efficacy against nongrowing and adherent Escherichia coli ATCC 25922. The alternative in vitro tests correlated highly with the outcome in the tissue-cage animal model. In the prophylaxis group (drug given 30 min before bacterial challenge), co-trimoxazole was less efficacious than the other three drugs (P less than 0.001). In delayed treatment, ciprofloxacin showed the highest cure rate. It was also more potent than the other drugs against nongrowing and adherent E. coli ATCC 25922. The efficacies of aztreonan, fleroxacin, and ciprofloxacin dropped significantly (P less than 0.01) when the time interval between bacterial challenge and the start of treatment was delayed to greater than 4 h. These data emphasize (i) the need for proper timing of prophylaxis in patients undergoing implant surgery, and (ii) the possibility of successful treatment of established device-related infections with drugs which kill not only growing but also nongrowing and adherent bacteria.

Exclusive Staphylococcus aureus Throat Carriage: At-Risk Populations

BACKGROUND Approximately 25% of Staphylococcus aureus carriers have exclusive throat carriage. We aimed to identify the populations at risk for exclusive throat carriage to improve sensitivity to detect carriers. METHODS Four groups underwent nasal and throat screening for S. aureus. Three groups of individuals in the community (n = 2632) with different estimated levels of exposure to the health care system (HCS) were screened, including 1500 healthy blood donors, 498 patients from a school of dental medicine, and 634 health care workers (HCWs) at a trade fair. The fourth group comprised in-hospital patients and HCWs (n = 832) and was considered the group with the highest estimated exposure to the HCS. As a primary outcome, we analyzed risk factors for exclusive throat carriage in exclusive throat carriers vs all nasal carriers. RESULTS Of 3464 individuals screened, 428 (12.4%) had exclusive throat carriage, and 1260 (36.4%) had carriage in the nares only or in the nares and the throat. The most important independent risk factor for exclusive throat carriage was age 30 years or younger (odds ratio, 1.66; P < .001). Exposure to the HCS was a significant protective factor for exclusive throat carriage (odds ratio, 0.67; P = .001). Healthy blood donors were almost twice as likely to have exclusive throat carriage than in-hospital patients and HCWs (30.2% vs 18.4% of all carriers, P < .001). CONCLUSIONS Absence of exposure to the HCS and younger age predicted exclusive throat carriers, a population at high risk for community-onset methicillin-resistant S. aureus. Screening for S. aureus should include swabs from the anterior nares and from the throat to improve the likelihood of detecting carriers.

Molecular Typing of Methicillin-Resistant Staphylococcus aureus: Can PCR Replace Pulsed-Field Gel Electrophoresis?

ABSTRACT Pulsed-field gel electrophoresis (PFGE) is considered the “gold standard” for molecular typing of methicillin-resistant Staphylococcus aureus (MRSA). However, the method is time-consuming and expensive, and its discriminatory power may not be necessary in outbreak situations. We used a rapid multiplex PCR-based method with published primers and compared the results with those obtained by PFGE. A total of 75 clinical isolates were typed: 59 strains originated from our prospectively collected clinical strains and were epidemiologically unrelated; 16 strains came from an outbreak that was epidemiologically well defined in time and space. A primer mix of the spa gene, the coa gene, and the hypervariable region adjacent to mecA gene was used for multiplex PCR. Both PFGE and PCR clustered the 75 strains into 41 different genotypes. Concordance of the results was 100% for strains originating from the outbreak. Overall, both methods produced concordant results in 72% of cases. A total of 16% were clustered together by PFGE, but not by PCR and 12% were clustered together by PCR but not by PFGE, respectively. The turnaround time was only 8 h for PCR but 5 days for PFGE. This PCR-based method is excellent for rapid and inexpensive typing of MRSA in an outbreak setting, but the discriminatory power and reproducibility are still insufficient to replace PFGE in longitudinal studies in the endemic setting.

Bacterial Colonization and Infection of Electrophysiological Cardiac Devices Detected With Sonication and Swab Culture

Background— Electrophysiological cardiac devices are increasingly used. The frequency of subclinical infection is unknown. We investigated all explanted devices using sonication, a method for detection of microbial biofilms on foreign bodies. Methods and Results— Consecutive patients in whom cardiac pacemakers and implantable cardioverter/defibrillators were removed at our institution between October 2007 and December 2008 were prospectively included. Devices (generator and/or leads) were aseptically removed and sonicated, and the resulting sonication fluid was cultured. In parallel, conventional swabs of the generator pouch were performed. A total of 121 removed devices (68 pacemakers, 53 implantable cardioverter/defibrillators) were included. The reasons for removal were insufficient battery charge (n=102), device upgrading (n=9), device dysfunction (n=4), or infection (n=6). In 115 episodes (95%) without clinical evidence of infection, 44 (38%) grew bacteria in sonication fluid, including Propionibacterium acnes (n=27), coagulase-negative staphylococci (n=11), Gram-positive anaerobe cocci (n=3), Gram-positive anaerobe rods (n=1), Gram-negative rods (n=1), and mixed bacteria (n=1). In 21 of 44 sonication-positive episodes, bacterial counts were significant (≥10 colony-forming units/mL of sonication fluid). In 26 sterilized controls, sonication cultures remained negative in 25 cases (96%). In 112 cases without clinical infection, conventional swab cultures were performed: 30 cultures (27%) were positive, and 18 (60%) were concordant with sonication fluid cultures. Six devices and leads were removed because of infection, growing Staphylococcus aureus, Streptococcus mitis, and coagulase-negative staphylococci in 6 sonication fluid cultures and 4 conventional swab cultures. Conclusions— Bacteria can colonize cardiac electrophysiological devices without clinical signs of infection.

Clinical Implications of Mycobacterium kansasii Species Heterogeneity: Swiss National Survey

ABSTRACT Several subtypes of Mycobacterium kansasii have been described, but their respective pathogenic roles are not clear. This study investigated the distribution of subtypes and the pathogenicity of M. kansasii strains (n = 191) isolated in Switzerland between 1991 and 1997. Demographic, clinical, and microbiological information was recorded from clinical files. Patients were classified as having an infection according to the criteria of the American Thoracic Society. Subtypes were defined by PCR-restriction enzyme analysis of the hsp65 gene. Subtype 1 comprised 67% of the isolates (n = 128), while subtypes 2 and 3 comprised 21% (n = 40) and 8% (n = 15), respectively. Other subtypes (subtypes 4 and 6 and a new subtype, 7) were recovered from only 4% of patients (n = 8). M. kansasii subtype 1 was considered pathogenic in 81% of patients, while M. kansasii subtype 2 was considered pathogenic in 67% of patients and other subtypes were considered pathogenic in 6% of patients. The majority of patients with M. kansasii subtype 2 were immunocompromised due to the use of corticosteroids (21% of patients) or coinfection with HIV (62.5% of patients). Subtyping M. kansasii may improve clinical management by distinguishing pathogenic from nonpathogenic subtypes.

Rate of Transmission of Extended-Spectrum Beta-Lactamase–Producing Enterobacteriaceae Without Contact Isolation

BACKGROUND Extended-spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae are emerging worldwide. Contact isolation is recommended; however, little is known about the rate of transmission without contact isolation in the non-epidemic setting. Therefore, we aimed to estimate the rate of spread (R(0)) of ESBL-producing Enterobacteriaceae in a tertiary care center with 5 intensive care units. METHODS In this observational cohort study performed from June 1999 through April 2011, all patients at the University Hospital Basel, Switzerland, who were hospitalized in the same room as a patient colonized or infected with an ESBL-producing Enterobacteriaceae for at least 24 hours (index case) were screened for ESBL carriage by testing of rectal swab samples, swab samples from open wounds or drainages, and urine samples from patients with foley catheters. Strains with phenotypic evidence for ESBL were confirmed by polymerase chain reaction. Nosocomial transmission was assumed when the result of screening for ESBL carriage in a contact patient was positive and molecular typing by pulsed-field gel electrophoresis (PFGE) revealed clonal relatedness with the strain from the index patient. RESULTS Active screening for ESBL carriage could be performed in 133 consecutive contact patients. Transmission confirmed by PFGE occurred in 2 (1.5%) of 133 contact patients, after a mean exposure to the index case of 4.3 days. CONCLUSIONS The estimated rate of spread of ESBL-producing Enterobacteriaceae-in particular, Escherichia coli-was low in a tertiary care university-affiliated hospital with high levels of standard hygiene precautions. The low level of nosocomial transmission and the rapid emergence of community-acquired ESBL challenge the routine use of contact isolation in a non-epidemic setting, saving resources and potentially improving patient care.

Fungemia with Saccharomyces cerevisiae after treatment with Saccharomyces boulardii

Usually considered a nonpathogenic yeast, Saccharomyces boulardii has been used to prevent antibiotic-associated diarrhea and to treat recurrent Clostridium difficile colitis and other diarrheal illnesses (1). It has been available in Europe in standardized lyophilised form since 1962. S boulardii is registered under the name S cerevisiae Hansen CBS 5926, but the manufacturer states that S boulardii is not the same as baker’s yeast (S cerevisiae) (2). We present a patient with S cerevisiae fungemia after treatment with S boulardii.