The relationship of initial concentration of Staphylococcus epidermidis in blood cultures and time to positivity (TTP) in an automated, continuously monitored blood culture system was assessed. Blood and 1 to 1,000 CFU of S. epidermidis per ml in stationary or exponential phase were inoculated in BACTEC Pediatric Plus F bottles and incubated. The TTP was inversely proportional to the initial inoculated concentration. Blood culture bottles with initial bacterial densities of <10 CFU/ml had a TTP of >20 h (upper limit of 95% prediction interval, 20.7 h) and bottles with initial bacterial densities of >50 CFU/ml had a TTP of <15 h (lower limit of 95% prediction interval, 13.4 h).Coagulase-negative staphylococci (CoNS) are ubiquitous skin commensals, and their isolation from a blood culture frequently reflects contamination. CoNS can also cause sepsis, particularly in premature infants, immunocompromised hosts, and patients with intravascular devices such as vascular catheters. In fact, CoNS are the most common cause of nosocomial bacteremia (6) as well as the most common blood culture contaminant.The significance of CoNS grown from blood cultures from febrile patients can be difficult to determine because their recovery may reflect bloodstream infection or blood culture contamination (or colonization of intravascular catheters or transient bacteremia). The differentiation is particularly difficult in pediatric patients, from whom only a single blood culture is frequently obtained. Quantitative cultures can aid interpretation. For example, in neonates a peripheral blood culture with Ն50 CFU of CoNS per ml of blood is generally considered indicative of infection (15), whereas a blood culture with Ͻ5 to 10 CFU/ml of blood is often considered indicative of contamination (8,12,15).Quantitative blood cultures can also aid in determining if bacteremia, occurring in either pediatric or adult patients, is vascular catheter related. A blood culture drawn via a central catheter with Ͼ100 CFU/ml of blood is suggestive of catheterrelated bloodstream infection (4,7,8,12,15). Catheter-related bloodstream infection is likely when quantitative cultures reveal that blood obtained via a catheter has Ն4 to 10 times greater bacterial density than found in peripheral blood (3,4,7,9).Quantitative blood cultures are not routinely available to clinicians. However, automated continuous-monitoring blood culture systems are in widespread use. Although these systems do not provide quantitative data, the incubation time to positivity (TTP), the time the blood culture bottle incubates in the instrument before microbial activity is detected, is available (5). TTP has been suggested as a surrogate for the initial bacterial density (2, 7, 11) and may potentially provide useful information to aid in interpreting the clinical significance of blood cultures growing CoNS and the diagnosis of vascular catheter-associated CoNS bacteremia. In the present study, the TTP of simulated blood cultures was determined by inoculating culture bottles with human bl...

Acinetobacter baumannii is a frequent cause of hospital-acquired pneumonia, and has recently increased in incidence as the causative agent of severe disease in troops wounded in Afghanistan and Iraq. Clinical approaches are limited since A. baumannii strains isolated from patients are extremely resistant to current antimicrobials. A. baumannii can survive desiccation and during outbreaks has been recovered from various sites in the patients' environment. To better understand its prevalence in hospital settings, we used a stainless steel washer (SSW) platform to investigate A. baumannii biofilm formation on abiotic surfaces. Scanning electron microscopy demonstrated that A. baumannii forms strong biofilms on stainless steel surfaces. This platform was combined with a colorimetric 2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)-5-[(phenylamino)carbonyl]-2H-tetrazolium hydroxide (XTT) reduction assay to observe the metabolic activity of bacterial cells, and to facilitate the manipulation and comparison of multiple A. baumannii clinical strains. A strong correlation between XTT and c.f.u. assays was demonstrated. To complement the cell viability assays, A. baumannii biofilm mass was measured by crystal violet staining. Furthermore, the effect of commonly used disinfectants and environmental stressors on A. baumannii biofilms and planktonic cells was compared and characterized. Biofilms on SSWs were significantly more resistant than their planktonic counterparts, providing additional evidence that may allow us to understand the high prevalence of this microbe in hospital settings. Our results validate that SSWs are a simple, versatile and innovative method to study A. baumannii biofilms in vitro.

Candida albicans is a leading fungal cause of burn infections in hospital settings, and sepsis is one of the principle causes of death after a severe burn. The prevalence of invasive candidiasis in burn cases varies widely, but it accounts for 3–23% of severe infection with a mortality rate ranging from 14 to 70%. Therefore, it is imperative that we develop innovative therapeutics to which this fungus is unlikely to evolve resistance, thus curtailing the associated morbidity and mortality and ultimately improving our capacity to treat these infections. An inexpensive and stable nitric oxide (NO)-releasing nanoparticle (NO-np) platform has been recently developed. NO is known to have direct antifungal activity, modulate host immune responses and significantly regulate wound healing. In this study, we hypothesized that NO-np would be an effective therapy in the treatment of C. albicans burn infections. Using a murine burn model, NO-np demonstrated antifungal activity against C. albicans in vivo, most likely by arresting its growth and morphogenesis as demonstrated in vitro. NO-np demonstrated effective antimicrobial activity against yeast and filamentous forms of the fungus. Moreover, we showed that NO-np significantly accelerated the rate of wound healing in cutaneous burn infections when compared to controls. The histological evaluation of the affected tissue revealed that NO-np treatment modified leukocyte infiltration, minimized the fungal burden, and reduced collagen degradation, thus providing potential mechanisms for the therapeutics’ biological activity. Together, these data suggest that NO-np have the potential to serve as a novel topical antifungal which can be used for the treatment of cutaneous burn infections and wounds.

Vancomycin-resistant Streptococcus salivarius-like bacteria were isolated from the blood and gastrostomy tube of a 6-month-old child during vancomycin therapy for Staphylococcus epidermidis central venous catheter-associated bacteremia. The isolates produced D-(-)-lactate and ethanol from glucose, hydrolyzed esculin, and produced no ammonia from arginine, thus fulfilling the major criteria as Leuconostoc spp. The enzymatic profile of the bacteria suggested that they were not lactobacilli or streptococci. Resistance to vancomycin and penicillin tolerance were noted. The formula fed through the gastrostomy tube was suspected as the vehicle that transmitted the organism to the patient. Penicillin and tobramycin therapy was used successfully.

This study evaluated personal digital assistant (PDA) microbial colonization before and after cleaning with alcohol. Samples from 75 PDAs were processed. Before cleaning, 96% of the samples were culture positive. After cleaning, 75% became culture negative. PDAs cleaned with an alcohol swab demonstrated significant reduction in colonization.

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Leuconostoc species are gaining importance as pathogenic organisms. We present the first case of odontogenic infection caused by Leuconostoc spp. Isolates initially identified as streptococci were found to be vancomycin resistant. Rigorous bacteriologic investigation subsequently classified these organisms as Leuconostoc mesenteroides.