Steckelberg, James M.

Background— The American Heart Association published updated guidelines for infective endocarditis (IE) prevention in 2007 that markedly restricted the use of antibiotic prophylaxis in certain at-risk patients undergoing dental and other invasive procedures. The incidence of IE caused by viridans group streptococci (VGS) in the United States after publication of the 2007 American Heart Association guidelines has not been reported. Methods and Results— We performed a population-based review of all definite or possible cases of VGS-IE using the Rochester Epidemiology Project of Olmsted County, Minnesota. Patient demographics and microbiological data were collected for all VGS-IE cases diagnosed from January 1, 1999, through December 31, 2010. We also examined the Nationwide Inpatient Sample hospital discharge database to determine the number of VGS-IE cases included between 1999 and 2009. We identified 22 cases with VGS-IE in Olmsted County over the 12-year study period. Rates of incidence (per 100 000 person-years) during time intervals of 1999–2002, 2003–2006, and 2007–2010 were 3.19 (95% confidence interval, 1.20–5.17), 2.48 (95% confidence interval, 0.85–4.10), and 0.77 (95% confidence interval, 0.00–1.64), respectively ( P =0.061 from Poisson regression). The number of hospital discharges with a VGS-IE diagnosis in the Nationwide Inpatient Sample database during 1999–2002, 2003–2006, and 2007–2009 ranged between 15 318 to 15 938, 16 214 to 17 433, and 14 728 to 15 479, respectively. Conclusions— On the basis of data complete through 2010, there has been no perceivable increase in the incidence of VGS-IE in Olmsted County, Minnesota, since the publication of the 2007 American Heart Association endocarditis prevention guidelines.

ABSTRACT Rifampin monotherapy was compared to the combination of linezolid or vancomycin with rifampin in an experimental rat model of methicillin-resistant Staphylococcus aureus (MRSA) chronic foreign body osteomyelitis. MRSA was inoculated into the proximal tibia, and a titanium wire was implanted. Four weeks after infection, rats were treated intraperitoneally for 21 days with rifampin alone ( n = 16), linezolid plus rifampin ( n = 14), or vancomycin plus rifampin ( n = 13). Thirteen animals received no treatment. At completion of treatment, qualitative cultures of the wire and quantitative cultures of the bone (reported as median values) were performed. Quantitative cultures from the control, rifampin monotherapy, linezolid-plus-rifampin, and vancomycin-plus-rifampin groups revealed 4.54, 0.71, 0.10, and 0.50 log 10 CFU/gram of bone, respectively. The bacterial load was significantly reduced in all treatment groups compared to that in the control group. Rifampin resistance was detected in isolates from 10, 2, and 1 animal in the rifampin, linezolid-plus-rifampin, and vancomycin-plus-rifampin groups, respectively. Cultures of the removed wire revealed bacterial growth in 1 and 2 animals in the rifampin and linezolid-plus-rifampin groups, respectively, with no growth in the vancomycin-plus-rifampin group and growth from all wires in the untreated group. In conclusion, we demonstrated that combination treatment with linezolid plus rifampin or vancomycin plus rifampin is effective in an animal model of MRSA foreign body osteomyelitis in the context of retention of the infected foreign body.

Background— Infection is a serious complication of cardiovascular implantable electronic device (CIED) placement and requires device removal for attempted cure. Methods and Results— We studied the rate, risk factors, and outcomes of CIED infection in 74 consecutive patients with bacteremia caused by Gram-positive cocci (GPC) other than Staphylococcus aureus between 2001 and 2007. CIED infection was defined as the presence of signs of infection at the generator site, lead vegetations seen on echocardiography, or microbiological growth from device cultures. Twenty-two (30%) of 74 patients with non– S aureus GPC bacteremia had CIED infections. Coagulase-negative staphylococci (CoNS) accounted for 73% of CIED infections. The rate of CIED infection in patients with CoNS bacteremia was almost 2-fold that of non-CoNS GPC bacteremia (36% versus 20%, P =0.13). The number of leads, the presence of abandoned leads, and prior generator replacement were associated with CIED infection. Among 33 patients without identifiable CIED infection at initial evaluation who did not undergo device removal, 5 (15%) had relapsing bacteremia within 12 weeks of completing antibiotic therapy. CoNS accounted for all relapses, and none had evidence of CIED infection at relapse. Conclusions— Patients with a CIED and bacteremia caused by GPC other than S aureus frequently had evidence of underlying CIED infection on clinical evaluation that included transesophageal echocardiography. This was particularly true among those with CoNS bacteremia. No evidence of underlying CIED infections was identified in the subgroup of patients who did not have manifestations of CIED infection on initial evaluation but subsequently had relapsing bacteremia caused by CoNS.

ABSTRACT Staphylococcus lugdunensis is a coagulase-negative staphylococcus that has several similarities to Staphylococcus aureus . S. lugdunensis is increasingly being recognized as a cause of prosthetic joint infection (PJI). The goal of the present retrospective cohort study was to determine the laboratory and clinical characteristics of S. lugdunensis PJIs seen at the Mayo Clinic in Rochester, MN, between 1 January 1998 and 31 December 2007. Kaplan-Meier survival methods and Wilcoxon sum-rank analysis were used to determine the cumulative incidence of treatment success and assess subset comparisons. There were 28 episodes of S . lugdunensis PJIs in 22 patients; half of those patients were females. Twenty-five episodes (89%) involved the prosthetic knee, while 3 (11%) involved the hip. Nine patients (32%) had an underlying urogenital abnormality. Among the 28 isolates in this study tested by agar dilution, 24 of 28 (86%) were oxacillin susceptible. Twenty of the 21 tested isolates (95%) lacked mecA , and 6 (27%) of the 22 isolates tested produced β-lactamase. The median durations of parenteral β-lactam therapy and vancomycin therapy were 38 days (range, 23 to 42 days) and 39 days (range, 12 to 60 days), respectively. The cumulative incidences of freedom from treatment failure (standard deviations) at 2 years were 92% (±7%) and 76% (±12%) for episodes treated with a parenteral β-lactam and vancomycin, respectively ( P = 0.015). S. lugdunensis is increasingly being recognized as a cause of PJIs. The majority of the isolates lacked mecA . Episodes treated with a parenteral β-lactam antibiotic appear to have a more favorable outcome than those treated with parenteral vancomycin.

ABSTRACT Members of the Streptococcus bovis group are important causes of endocarditis. However, factors associated with their pathogenicity, such as adhesins, remain uncharacterized. We recently demonstrated that endocarditis-derived Streptococcus gallolyticus subsp. gallolyticus isolates frequently adhere to extracellular matrix (ECM) proteins. Here, we generated a draft genome sequence of an ECM protein-adherent S. gallolyticus subsp. gallolyticus strain and found, by genome-wide analyses, 11 predicted LPXTG-type cell wall-anchored proteins with characteristics of MSCRAMMs, including a modular architecture of domains predicted to adopt immunoglobulin (Ig)-like folding. A recombinant segment of one of these, Acb, showed high-affinity binding to immobilized collagen, and cell surface expression of Acb correlated with the presence of acb and collagen adherence of isolates. Three of the 11 proteins have similarities to major pilus subunits and are organized in separate clusters, each including a second Ig-fold-containing MSCRAMM and a class C sortase, suggesting that the sequenced strain encodes three distinct types of pili. Reverse transcription-PCR demonstrated that all three genes of one cluster, acb - sbs7 - srtC1 , are cotranscribed, consistent with pilus operons of other gram-positive bacteria. Further analysis detected expression of all 11 genes in cells grown to mid to late exponential growth phases. Wide distribution of 9 of the 11 genes was observed among S. gallolyticus subsp. gallolyticus isolates with fewer genes present in other S. bovis group species/subspecies. The high prevalence of genes encoding putative MSCRAMMs and pili, including a collagen-binding MSCRAMM, among S. gallolyticus subsp. gallolyticus isolates may play an important role in the predominance of this subspecies in S. bovis endocarditis.

ABSTRACT Treatment with low-amperage (200 μA) electrical current was compared to intravenous doxycycline treatment or no treatment in a rabbit model of Staphylococcus epidermidis chronic foreign body osteomyelitis to determine if the electricidal effect is active in vivo. A stainless steel implant and 10 4 CFU of planktonic S. epidermidis were placed into the medullary cavity of the tibia. Four weeks later, rabbits were assigned to one of three groups with treatment administered for 21 days. The groups included those receiving no treatment ( n = 10), intravenous doxycycline ( n = 14; 8 mg/kg of body weight three times per day), and electrical current ( n = 15; 200 μA continuous delivery). Following treatment, rabbits were sacrificed and the tibias quantitatively cultured. Bacterial load was significantly reduced in the doxycycline (median, 2.55 [range, 0.50 to 6.13] log 10 CFU/g of bone) and electrical-current (median, 1.09 [range, 0.50 to 2.99] log 10 CFU/g of bone) groups, compared to the level for the control group (median, 4.16 [range, 3.70 to 5.66] log 10 CFU/g of bone) ( P < 0.0001). Moreover, treatment with electrical current was statistically significantly more efficacious ( P = 0.035) than doxycycline treatment. The electricidal effect (the bactericidal activity of low-amperage electrical current against bacterial biofilms) is active in vivo in the treatment of experimental S. epidermidis chronic foreign body osteomyelitis.

ABSTRACT We established a murine model of Candida albicans central nervous system (CNS) infection and evaluated the efficacy of anidulafungin. Ten milligrams/kg/day anidulafungin, amphotericin B, or voriconazole significantly reduced mortality and fungal burden in brain tissue, although amphotericin B and 10 mg/kg/day anidulafungin reduced fungal burden in brain tissue to a greater extent than did voriconazole. This suggests a potential role for anidulafungin in the treatment of candidal CNS infection.

ABSTRACT Planktonic and sessile susceptibilities to micafungin were determined for 30 clinical isolates of Candida albicans obtained from blood or other sterile sites. Planktonic and sessile MIC 90 s for micafungin were 0.125 and 1.0 μg/ml, respectively.

ABSTRACT We recently described a sonication technique for the diagnosis of prosthetic knee and hip infections. We compared periprosthetic tissue culture to implant sonication followed by sonicate fluid culture for the diagnosis of prosthetic shoulder infection. One hundred thirty-six patients undergoing arthroplasty revision or resection were studied; 33 had definite prosthetic shoulder infections and 2 had probable prosthetic shoulder infections. Sonicate fluid culture was more sensitive than periprosthetic tissue culture for the detection of definite prosthetic shoulder infection (66.7 and 54.5%, respectively; P = 0.046). The specificities were similar (98.0% and 95.1%, respectively; P = 0.26). Propionibacterium acnes was the commonest species detected among culture-positive definite prosthetic shoulder infection cases by periprosthetic tissue culture (38.9%) and sonicate fluid culture (40.9%). All subjects from whom P. acnes was isolated from sonicate fluid were male. We conclude that sonicate fluid culture is useful for the diagnosis of prosthetic shoulder infection.

ABSTRACT Capsular contracture is the most common and frustrating complication in women who have undergone breast implantation. Its cause and, accordingly, treatment and prevention remain to be elucidated fully. The aim of this prospective observational pilot study was to test the hypothesis that the presence of bacteria on breast implants is associated with capsular contracture. We prospectively studied consecutive patients who underwent breast implant removal for reasons other than overt infection at the Mayo Clinic from February through September 2008. Removed breast implants were processed using a vortexing/sonication procedure and then subjected to semiquantitative culture. Twenty-seven of the 45 implants collected were removed due to significant capsular contracture, among which 9 (33%) had ≥20 CFU bacteria/10 ml sonicate fluid; 18 were removed for reasons other than significant capsular contracture, among which 1 (5%) had ≥20 CFU/10 ml sonicate fluid ( P = 0.034). Propionibacterium species, coagulase-negative staphylococci, and Corynebacterium species were the microorganisms isolated. The results of this study demonstrate that there is a significant association between capsular contracture and the presence of bacteria on the implant. The role of these bacteria in the pathogenesis of capsular contracture deserves further study.