Aim: We compared the MBEC™‐HTP assay plates made of polystyrene with metal discs composed of TMZF® and CrCo as substrates for biofilm formation. Methods and Results: Staphylococcus aureus was grown ...on polystyrene and on metal discs made of titanium and chrome–cobalt. Antibiotic susceptibility was assessed by examining the recovery of cells after antibiotic exposure and by measuring the biofilm inhibitory concentration (BIC). The minimal inhibitory concentration (MIC) was assessed with planktonic cells. Bacterial growth was examined by scanning electron microscopy. The antibiotic concentration for biofilm inhibition (BIC) was higher than the MIC for all antibiotics. Microscopic images showed the biofilm structure characterized by groups of cells covered by a film. Conclusions: All models allowed biofilm formation and testing with several antibiotics in vitro. Gentamicin and rifampicin are the most effective inhibitors of Staph. aureus biofilm‐related infections. We recommend MBEC™‐HTP assay for rapid testing of multiple substances and TMZF® and CrCo discs for low‐throughput testing of antibiotic susceptibility and for microscopic analysis. Significance and Impact of the Study: In vitro assays can improve the understanding of biofilms and help developing methods to eliminate biofilms from implant surfaces. One advantage of the TMZF® and CrCo discs as biofilm in vitro assay is that these metals are commonly used for orthopaedic implants. These models are usable for future periprosthetic joint infection studies.
Freezing is the most common method for storing bones until use in skeletal reconstruction. However, the effect of freezing on antibiotic delivery from antibiotic-coated bone has not been evaluated. ...In this study, we compared antibiotic delivery in vitro from gentamicin-coated human bone stored at different temperatures. Bone chips obtained from human femur heads were chemically cleaned and mixed with gentamicin sulfate. Samples were stored for 4 months at −20 °C, 4 months at −80 °C, or evaluated immediately without freezing. Antibiotic release from the bone chips was measured using
Bacillus subtilis
as an indicator strain. Zones of inhibition and rates of gentamicin release were similar in all three groups. Storage at −20 and −80 °C for bone allografts has no effect on gentamicin release from chemically cleaned bone chips.
Clostridium difficile (CD) is one of the most common causes of diarrhea in solid organ transplantation (SOT). Between 1996 and 2005, a total of 2474 solid organ transplants were performed at our ...institution, of which 43 patients developed CD-associated diarrhea. There were 3 lung, 3 heart, 20 liver, 8 kidney-pancreas, 6 kidney, 1 composite tissue, and 2 multivisceral recipients. Onset of CD infection ranged from 5 to 2453 days posttransplant. All patients presented with abdominal pain and watery diarrhea. Toxins A and B were detected using rapid immunoassay or enzyme immunoassay. Treatment consisted of reduction of immunosuppression, fluid and electrolyte replacement, metronidazole (n=20), oral vancomycin (n=20), and a combination of metronidazole and vancomycin (n=2). Toxic megacolon was seen in five patients. Two of them had colonoscopic decompression, and the remaining three required colonic resection. One of these patients died due to multiorgan failure after cured CD enteritis. The remaining patients were discharged with well-functioning grafts and all are currently alive. CD colitis was a rare complication prior to 2000; 38 of the 43 cases occurred thereafter. We conclude that CD colitis represents a severe complication following SOT. Recently, a dramatic increase in the incidence of this complication has been observed. The development of life-threatening toxic megacolon must be considered in solid organ recipients.
Bone allografts are a useful and sometimes indispensable tool for the surgeon to repair bone defects. Microbial contamination is a major reason for discarding allografts from bone banks. To improve ...the number of safe allografts, we suggest chemical cleaning of the grafts followed by antibiotic impregnation. Comparison of two chemical cleaning processes for bone allografts aiming for antibiotic impregnation and consequently delivery rates in vitro. Bone chips of 5–10 mm were prepared from human femoral heads. Two cleaning methods (cleaning A and cleaning B) based on solutions containing hydrogen peroxide, paracetic acid, ethanol and biological detergent were carried out and compared. After the cleaning processes, the bone chips were impregnated with gentamicin.
Bacillus subtilis
bioassay was used to determine the gentamicin release after intervals of 1–7 days. Differences were compared with non-parametric Mann–Whitney
U
tests. The zones of inhibition obtained from the bone grafts cleaned with both cleaning processes were similar between the groups. The concentration of the released antibiotic was decreasing gradually over time, following a similar pattern for both groups. The cleaning procedure A as well as the cleaning procedure B for bone allografts allowed the impregnation with gentamicin powder in the same concentrations in both groups. The delivery of gentamicin was similar for both groups. Both cleaning procedures were easy to be carried out, making them suitable for routine use at the bone banks.
Ralstonia pickettii can be isolated from water, soil and plants, and can also form part of the commensal flora of the oral cavity and the upper respiratory tract of healthy individuals. R. pickettii ...is an infrequent pathogen, but can cause infections, mainly of the respiratory tract, in immunocompromised and cystic fibrosis patients. It can be isolated from a variety of clinical specimens, including sputum, blood, wound infections, urine, ear and nose swabs, and cerebrospinal fluid. Resistance can occur to ciprofloxacin, trimethoprim–sulphamethoxazole, piperacillin–tazobactam, imipenem–cilastatin and ceftazidime. Early detection of R. pickettii allows prompt appropriate antimicrobial therapy with a favourable outcome, but removal of infected indwelling devices is mandatory.
The development of bacterial resistance during selective decontamination of the digestive tract (SDD) is controversial. We studied effects on bacterial resistance one year before and during a ...randomized, placebo-controlled trial of SDD in a surgical intensive care unit. We randomized patients within two different topical regimens (PTA, PCA) or placebo, administered four-times daily to both the oropharynx and gastrointestinal tract. All patients received intravenous ciprofloxacin (200 mg b.d.) for four days. Both SDD regimens successfully reduced aerobic Gram-negative intestinal colonization. There was no increase in resistance of Enterobacteriaceae or
Pseudomonas aeruginosa.
Acinetobacter calcoaceticus developed multi-resitance over one year, but differences between groups were not significant. We detected a shift towards Gram-positive organisms. Oxacillin-resistant
Staphylococcus aureus increased in concert with ciprofloxacin resistance, from 17 to 80·7%, and frequencies of resistance were significantly higher in SDD patients (
P < 0·001). Resistance of coagulase-negative staphylococci (CNS) to oxacillin increased initially (25 to 66·9%), but values returned to baseline in controls. Ciprofloxacin resistance in CNS remained higher (
P < 0·001) in SDD-treated patients (52·5 vs. 23·3%). The incidence of late respiratory tract infections was unaltered by the prophylactic regimen (SDD 35·2%; Placebo 41·2%; n.s.). We cannot recommend SDD as a prophylactic tool in critically ill patients.
Background Anal abscesses are commonly associated with fistulas‐in‐ano and are usually polymicrobial in nature, with gram‐negative rods and anaerobes being the most prevalent isolates. Group Milleri ...Streptococci (GMS) comprise a heterogeneous group of cocci, which are capable of causing severe purulent infection with a high recurrence rate.
Method All anorectal infections caused by GMS, which were identified at our centre during a 4‐year period were retrospectively analysed. The 18 patients with GMS‐positive anorectal abscesses were matched with 36 GMS‐negative anorectal abscesses to identify outcome characteristics of this clinical entity.
Results During the study period, 358 patients underwent surgical treatment for anal infections; GMS were isolated in 46 individuals (13%) including 18 perianal abscesses, 11 pilonidal sinuses, eight fistulae in and nine miscellaneous infections. Seventy‐two per cent of perianal GMS infections were polymicrobial with E. coli and Bacteroides fragilis being the predominant second bacteria. Nine patients (20%) developed recurrent abscesses and fistulae‐in‐ano and underwent additional surgical interventions with resolution at follow‐up. Additional antibiotic treatment was administered in 10 patients with complex anal infections. Matched pair analysis revealed that GMS‐positive perianal abscesses were more commonly polymicrobial, and that the recurrence rate was higher (55.6% GMS‐positive and 22.2% GMS‐negative patients, P = 0.017).
Conclusions Our data confirm the propensity of GMS to form deep and recurrent abscesses with a higher recurrence rate than non‐GMS infections. First‐line treatment includes surgical drainage, and antibiotic treatment may be useful in selected patients.
To investigate the epidemiology, microbiology and outcome of infections caused by Capnocytophaga spp. at a single center.
We report on ten documented infectious episodes caused by Capnocytophaga ...observed between 1994 and 1999 at the Innsbruck University Hospital.
In seven of ten patients, Capnocytophaga septicemia was diagnosed during periods of neutropenia. In contrast, the remaining three patients had normal white blood cell counts when acquiring Capnocytophaga septicemia (one) and pleural empyema (two). Blood cultures containing long, slender, Gram-negative rods, which grew slowly under anaerobic conditions and lacked susceptibility to metronidazole, were subcultivated in a CO2-enriched atmosphere (5%). Subcultivation yielded Capnocytophaga in all ten cases within 2-12 days. The patients were then placed on appropriate antibiotic therapy, with or without additional surgical intervention, and the organism was eradicated.
Identification of Capnocytophaga facilitates appropriate, and in most cases effective, antimicrobial therapy.
Recent data show an emergence of resistance in the Bacteroides fragilis group against several antimicrobial agents and inducible resistance against metronidazole in nim-positive strains. The aim of ...the present study was to investigate inducible metronidazole resistance in nim-positive as well as in nim-negative B. fragilis group strains.
Of 18 B. fragilis strains (including four nim-positive reference strains and one ATCC strain), two Bacteroides ovatus strains, and one Bacteroides thetaiotaomicron DSM strain minimum inhibitory concentration (MIC) values for metronidazole were determined by Etest and analyzed for nim genes (nimA to -G) by PCR. For this purpose bacterial suspensions were incubated on supplemented Columbia agar plates containing metronidazole at twice the MIC value of the specific strain and incubated under anaerobic conditions for 48 hours. After incubation, growing bacteria were harvested and thereafter incubated at four times the original MIC. This procedure was repeated with increasing antibiotic concentrations. The resulting MIC values were confirmed by Etest.
The MIC values for metronidazole of the four nim-positive reference strains ranged from 3 to 8 mg/l. The B. fragilis ATCC 25285 strain and the B. thetaiotaomicron DSM 2255 strain were nim negative with MIC values of 0.19 mg/l and 0.75 mg/l, respectively. Three clinical isolates of B. fragilis strains showed MIC values of > 256 mg/l. In all three strains, nim genes were detected by PCR. The other clinical isolates were nim negative. In these strains, MIC values ranged from 0.19 to 0.75 mg/l. After several passages on metronidazole containing agar, all B. fragilis group strains exhibited MIC values of > 256 mg/l determined by Etest.
Metronidazole resistance can be selected not only in nim-positive strains but also in nim-negative strains, suggesting that mechanisms other than nim genes are involved. These findings and the emerging resistance of the B. fragilis group against several antimicrobial agents underscore the importance of susceptibility testing of anaerobes even in routine laboratories.
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