Can Pseudomonas aeruginosa growth be modulated by natural compounds?

Pseudomonas aeruginosa is an opportunistic human pathogen that frequently induces antibiotic resistance, as it mainly tends to form biofilms. Iron chelation may be an intriguing strategy to contrast bacterial growth. Lactoferrin is a natural compound able to chelate iron. A new multi-component medical device also contains lactoferrin. This study analyzed this compound investigating the in vitro capacity to inhibit Pseudomonas aeruginosa growth. In conclusion, this study demonstrated that a multicomponent medical device (Saflovir), also containing lactoferrin, could inhibit the in vitro growth of P. aeruginosa. This activity could be positively used in the prevention of respiratory nasal infections.

Fusidic acid betamethasone lipid cream.

Bacterial infections of the skin and soft tissues are frequent disorders. They can be primitive infections (e.g. impetigo, folliculitis) or secondary infections complicating other diseases, particularly atopic dermatitis. The most common aetiologic agent is Staphylococcus aureus. Topical antibiotic therapy may be sufficient in many instances to control these infections. Fusidic acid is an antibiotic used topically on the skin which is very active against S. aureus, including methicillin-resistant strains, and other Gram-positive bacteria. Resistance rates to fusidic acid are stably low. A fusidic acid and betamethasone formulation in a lipid-enriched cream (lipid cream) has been recently developed in order to provide effective antibacterial and anti-inflammatory activities in conjunction with a powerful emollient and moisturising effect. This preparation may be especially useful in patients with atopic-infected eczema.

Prolonging culture to 15 days improves bacterial detection in bone and joint infections.

Since the optimal incubation period of cultures for diagnosis of bone and joint infections is still a matter of debate, the present study aimed to evaluate the effects of different incubation periods (5 and 15 days) on microbial isolation. Samples from 387 patients with bone and joint infections (including prosthetic ones) were analyzed from March 2012 to February 2014. In 197 patients (51 %) growth was obtained within 48 hrs, while in 124 (32 %) and 66 (17 %) patients cultures yielded positive results within and after 5 days of incubation, respectively. Of 449 microorganisms isolated, 247 grew within 48 hrs, 131 within the first 5 days of incubation while 71 were isolated after 5 days. Staphylococcus aureus was the most frequently isolated pathogen within 48 hrs, while Propionibacteria were prevalently isolated after 5 days of incubation. Interestingly, about 25 % of microorganisms isolated after 5 days of incubation were coagulase-negative staphylococci. Extending incubation period of broth cultures improves isolation rates of pathogens involved in bone and joint infections thus improving management of these infections.

Iron status evaluation as a marker of postoperative joint infection: a pilot study.

We evaluated the effect of different inflammatory conditions on iron status and, as a consequence, the possible use of iron markers as indicators of infection in the diagnosis of postoperative prosthetic orthopaedic joint infections. The study population was consisted of 26 patients undergoing revision of total hip or total knee joint arthroplasty and subdivided into three groups according to the cause of prosthesis implant failure: 10 as having had previous infection (Group A), 10 patients were categorized as having infection (Group B); and the remaining 6 (Group C) as not having infection. These patients were assayed for mean corpuscular haemoglobin concentration (MCHC) and serum values of iron (Fe), ferritin (Fer), transferrin (Tf), soluble transferrin receptor (sTfR), and transferrin saturation (sat Tf). Septic patients display statistically significant lower serum iron concentration, higher sTfR and ferritin levels, lower, but not statistically significant, MCHC compared to non septic ones. Little differences were observed for Tf, sat Tf, tibc, TfR index, among the three groups of patients. Our study suggests that iron status parameters, in particular serum iron, ferritin, sTfR and TfR index, could be useful tools for the early detection and the diagnosis of orthopaedic prosthetic joint infections.

Dental unit water content and antibiotic resistance of Pseudomonas aeruginosa and Pseudomonas species: a case study.

Background: Many studies consider the contamination of dental unit waterlines (DUWLs), but few of them have studied the possible presence of antibiotic resistant Pseudomonas aeruginosa in the DUWLs. Aims: Investigation of the presence of P. aeruginosa and Pseudomonas spp. strains in DUWLs and evaluation of their resistance to six antibiotics (ceftazidime, netilmicin, piperacillin/tazobactam, meropenem, levofloxacin, colistin sulfate) at a public dental clinic in Milan, Italy. Results: Dental units were contaminated by P. aeruginosa with loads of 2-1,000 CFU/L and were mainly located on the mezzanine floor, with a range of 46-54%, while Pseudomonas spp. were primarily found on the first and second floors, ranging from 50 to 91%. P. aeruginosa was antibiotic resistant in 30% of the strains tested, andPseudomonas spp. in 31.8% . Cold water from controls was also contaminated by these microorganisms. Conclusion: Monitoring antibiotic resistance in the water and adopting disinfection procedures on DUs are suggested within the Water Safety Plan.

Comparative evaluation of synergy of combinations of beta-lactams with fluoroquinolones or a macrolide in Streptococcus pneumoniae.

OBJECTIVES: Streptococcus pneumoniae has shown a great ability to develop efficacious mechanisms of resistance to the main drugs for the treatment of pneumonia, such as ß-lactams, macrolides and fluoroquinolones. The present study aimed to compare the antipneumococcal activity of combinations of respiratory fluoroquinolones with cephalosporins (either parenteral or oral) or protected penicillin versus the standard combinations (i.e. a macrolide with a protected penicillin or cephalosporin) against 100 isolates with different susceptibilities to macrolides and/or penicillin. METHODS: Chequerboard assays for all isolates and time-kill curves for nine isolates with different patterns of susceptibility were performed. Synergy between antibiotics at serum peak concentrations was also determined. RESULTS: The combination of levofloxacin with ceftriaxone produced the highest rate of synergy (54/100), mainly against macrolide-resistant strains (22/30). Antagonism was not observed for any tested combination apart from clarithromycin with amoxicillin/clavulanic acid (22/100 isolates). Although the killing activities of all antibiotics improved when they were tested in combination, synergy was observed only for some combinations after 12 and/or 24 h. Serum concentrations were effective in inhibiting the growth of the tested strains. CONCLUSIONS: Combinations of levofloxacin with parenteral cephalosporins were the most active among all the tested combinations, while antagonism occurred when clarithromycin and amoxicillin/clavulanic acid were tested.

Procalcitonin, C-reactive protein, interleukin-6, and soluble intercellular adhesion molecule-1 as markers of postoperative orthopaedic joint prosthesis infections.

There is a universally recognized need to identify new, reliable markers of inflammation that can aid in the rapid diagnosis of orthopaedic joint prosthesis infections (OJP-Is). Since prompt diagnosis is key to timely intervention in the course of infection, different molecules have been studied. In this study, we examined three groups of patients: those with prosthesis infection, those without infection, and a third group with previous infection in whom the infection had been cleared. Four presumed markers of infection were tested: procalcitonin (PCT); C-reactive protein (CRP); interleukin-6 (IL-6); and soluble intercellular adhesion molecule-1 (sICAM-1). The results showed that PCT cannot be considered as a good marker of periprosthetic infection as no statistically significant difference in serum PCT levels emerged between patients with infection and controls or patients without infection. In contrast, both sICAM-1 and CRP may be considered as good markers of infection, as measurement of their levels allowed us to distinguish between patients with and without infection, and between patients with infection and those with previous infection, since marker levels quickly returned to baseline values after clearance of the infection. IL-6 was found to be a good marker for inflammation, as it distinguished between patients with infection and the other groups. In the patients with previous infection, the IL-6 values remained high versus the controls but lower and with a statistically significant difference versus the patients with infection. Further studies are needed to determine the cut-off value of IL-6 between patients with infection and those with previous infection.

Modulation of biofilm of strains isolated from patients with chronic obstructive pulmonary disease by levofloxacin, moxifloxacin, ciprofloxacin, amoxicillin/clavulanic acid and ceftriaxone.

The ability of levofloxacin, moxifloxacin, ciprofloxacin, amoxicillin/clavulanic acid and ceftriaxone to interfere on biofilm produced by Pseudomonas aeruginosa, Haemophilus influenzae and Streptococcus pneumoniae isolated from patients with chronic obstructive pulmonary disease was evaluated. The effects of antibiotics were evaluated on formation of biofilm (at 1/2, 1/4 and 1/8 X MIC) and on preformed biofilm (at epithelial lining fluid peak concentrations) by means of a spectrophotometric method. Levofloxacin was the most active compound followed by ciprofloxacin, moxifloxacin and amoxicillin/clavulanic acid and ceftriaxone. Levofloxacin may contribute to clear the reservoir of pathogens involved in chronic obstructive pulmonary disease, thus leading to decreased occurrence of acute exacerbations.

A new urinary catheter design reduces in-vitro biofilm formation by influencing hydrodynamics.

AIM: To evaluate the performance of a new catheter design based on different hydrodynamics aiming to reduce the development of biofilm, and compare it with a conventional Foley catheter (FC). METHODS: The new proposed design (NPD) catheter is a modification of the FC, based on asymmetric positioning of the balloon and additional drainage holes allowing continuous urine drainage and complete voiding of the bladder. A first experiment was undertaken to assess drainage capability, and a second experiment was performed using a bioreactor with a set-up simulating the bladder and using the test catheter as a flow-through system. The biofilm formation of five bacterial species associated with catheter-associated urinary tract infection (CAUTI) was determined after 24 h of incubation using an MTT assay. Morphological evaluation was performed using scanning electron microscopy. In-vitro determination of residual fluid, and quantitative and morphological data on biofilm formation on the intravesical and intraluminal parts of the tested catheters were assessed. RESULTS: Residual fluid was significantly higher in the FC (5.60 ± 0.43 mL) compared with the NPD catheter (0.2 ± 0.03 mL). The NPD catheter showed significantly less biofilm formation (P<0.0001) than the FC. Catheter design had a variable effect on biofilm formation depending on the bacterial strain tested. There was significantly less intraluminal biomass compared with intravesical biomass in both catheters (P<0.0001). Multi-layered biofilms that covered the FC surfaces completely were seen for all tested strains, while the NPD catheter surfaces showed reduced biofilm formation. CONCLUSIONS: Modifications of the hydrodynamic characteristics of a catheter can significantly reduce bacterial colonization. Integrated design approaches combining chemical, mechanical and topographical elements can help to reduce the occurrence of CAUTI.

Antibacterial and antibiofilm effects of radioactive thermal water.

OBJECTIVE: Most of the infections of the upper respiratory tract are caused by biofilm-forming microorganisms belonging to the Pseudomonas, Streptococcus, Staphylococcus, and Enterobacter genus. Many of these microorganisms also show antibiotic resistance, partly related to biofilm formation. The treatment of these affections may include inhalation of radioactive thermal water (RTW). The present study aimed to evaluate the in vitro antibiofilm effect of RTW collected from Merano springs, Italy. MATERIALS AND METHODS: A series of experiments were performed evaluating the effect of RTW against planktonic cultures (1 h exposure) and on biofilms (10 min and 1 h exposure) formed by Staphylococcus aureus, Streptococcus pneumoniae, Pseudomonas aeruginosa, and Escherichia coli. Viable biomass was assessed using a colorimetric assay. A model based on the infection by the same strains of a reconstituted human respiratory epithelium (RHRE) was used to morphologically evaluate the antibiofilm effect of RTW. RESULTS: RTW decreased the viability of S. aureus and S. pneumoniae planktonic cultures by about 20%. RTW also decreased biofilm viability by all strains except for E. coli at both time points. In the RHRE model, bacterial adherence and colonization occurred in all specimens, showing a particular affinity for the epithelium's cilia. Bacterial infections caused significant alterations in the epithelium structure, showing enlargement of the intercellular spaces, and damage to the cell structure. Specimens infected with S. aureus showed slightly lower colonization levels after RTW treatment. CONCLUSIONS: Results of this in vitro study showed a significant effect of RTW against Gram-positive planktonic bacterial cells as well as a significant antibiofilm activity.

Prevalence of the internalization-associated gene prtF1 in a bacterial population of Streptococcus pyogenes isolated from children with acute pharyngotonsillitis before and after antibiotic therapy.

The prevalence of the internalization-associated prtF1 gene was studied in 837 isolates of Streptococcus pyogenes obtained from 713 pediatric patients presenting with acute pharyngotonsillitis before and after antibiotic therapy. Its association with macrolide resistance and with bacteriological treatment failure was determined. The bacterial population isolated from baseline pharyngeal swabs showed an overall prtF1 positivity rate of 33%. A higher prtF1 positivity was found among erythromycin-resistant strains (45%) showing, however, marked differences between the inducible (iMLS), constitutive (cMLS), and efflux pump (M) resistance phenotypes. The prevalence was statistically higher (p < 0.001) in strains belonging to iMLS (84%) and cMLS (67%) phenotypes as compared to the M phenotype (15%). Interestingly, the prevalence of the prtF1 gene was significantly lower (p = 0.04) in strains belonging to M resistance phenotype as compared to erythromycin-susceptible strains (28%). Failed bacterial eradication was demonstrated in 124 patients. The prtF1 positivity rate remained unchanged in strains isolated before and after therapy in patients treated with macrolides (9/54). On the other hand, the positivity rate for the prtF1 gene was significantly higher (p = 0.015) in strains isolated after therapy with beta-lactams (21/70) as compared to baseline isolates (6/70), indicating a differential selection imposed on the organism by these agents. Finally, a high overall eradication rate (88%) of prtF1-positive isolates, belonging to both the erythromycin-susceptible and -resistant phenotypes, was demonstrated following macrolide treatment.

Antibiotic susceptibility of group A streptococci in 2 Italian cities: Milano and Catania.

Resistance to macrolides has increasingly been reported for Group A streptococci. In this study, the in vitro antibiotic susceptibility pattern of 305 clinical isolates of S. pyogenes was determined. Strains were isolated during 1996 from pharyngeal swabs of children with uncomplicated pharyngitis living in 2 Italian cities: Milano and Catania, situated in the North and South of Italy, respectively. All isolates were found to be fully susceptible to penicillin and other beta-lactam agents tested. Susceptibility to macrolides differed markedly between the two centers with relatively high resistance rates to erythromycin being observed in Milano (30%) as compared to Catania (3%). Resistance to erythromycin was always crossed with that of the other 14- and 15-membered macrolides tested. However, resistance to josamycin and clindamycin was generally found in approximately 25% of the erythromycin-resistant (ER) strains. The erythromycin-resistant isolates from Milano and Catania (58 strains) were further subdivided into the three previously described resistance phenotypes: constitutive, inducible, and novel resistance phenotypes. The novel resistance phenotype accounted for 58% of all resistant strains, while 17% and 26% were found to be of the inducible and constitutive resistance phenotypes. Strains of the novel resistance phenotype were characterized by lower MIC values (MIC90 = 16 mg/L) to 14 and 15 carbon atom macrolides as compared to the other two phenotypes (MIC90 > 128 mg/L), and retained susceptibility to clindamycin and to josamycin, a 16 carbon atom macrolide. Resistance to tetracyclines was found in 25% to 36% of the ER isolates as compared to 2% to 10% of the susceptible strains. In particular, resistance to this agent was more commonly associated to isolates belonging to the novel and constitutive resistance phenotypes. MIC values for chloramphenicol in all isolates were within the susceptible or intermediate range; decreased susceptibility to this agent did not appear to be associated with erythromycin resistance.

High incidence of erythromycin-resistant Streptococcus pyogenes in Monza (North Italy) in untreated children with symptoms of acute pharyngo-tonsillitis: an epidemiological and molecular study.

A retrospective analysis of susceptibility data available for Group A streptococcal isolates collected between January 1990 and January 1996 at the Hospital Microbiology Laboratory of Monza (North Italy), showed a sharp rise in the erythromycin resistance rates during the last 3 years. Streptococcus pyogenes resistant to erythromycin accounted for approximately 1% of strains isolated between 1990 and 1992; the percentage then rose from 5% in 1993 to almost 39% in 1995. In January 1996, the resistance rates peaked to 81%. A prospective controlled study performed between March and May of 1996 to determine the percentage of erythromycin-resistant Group A streptococci isolated in Monza from untreated children with acute pharyngo-tonsillitis, gave further confirmation of a high rate of erythromycin resistance (47%) in this area. Molecular characterization by T-serotyping and pulse-field gel electrophoresis analysis of 25 erythromycin-resistant Group A streptococcal isolates, showed a relatively high degree of heterogeneity among these strains, demonstrating that the increased resistance is not caused by the spread of a single clone.

Bacteriological and clinical efficacy of various antibiotics used in the treatment of streptococcal pharyngitis in Italy. An epidemiological study.

A total of 123 community paediatricians and 23 microbiology laboratories studied the clinical and bacteriological efficacy of treatment of group A streptococcal pharyngitis in Italy. Of 1065 patients, from whom Streptococcus pyogenes was isolated, 723 returned to follow up and of these 138 (19%) still had a positive throat culture. The erythromycin resistance (ER) rate was 23.7% with resistance phenotype distribution of: 31.7% constitutive (CR), 26.6% inducible (IR) and 41.7% efflux pump (M) resistance phenotype. All strains were susceptible to the beta-lactam agents tested. CR strains were highly resistant to all 14, 15 and 16 membered macrolides with the exception of rokitamycin which showed activity against 37.8% of isolates. All phenotype M and some IR isolates were susceptible to clindamycin, rokitamycin, josamycin and spiramycin; clarithromycin was active against a small percentage of strains belonging to the IR and M phenotype. Bacterial eradication was found in 85.5, 78.7 and 75.8% of the penicillin, macrolide and cephalosporin treated groups. Genotyping of strains showed that 8.7% of the 19% of cases classified as 'failed bacterial eradication' were due to recolonization with a different isolate, observed exclusively among beta-lactams treated patients. Clinical cure was achieved in a high percentage of cases, irrespective of the antibiotic prescribed, with the best clinical efficacy being found following therapy with amoxycillin and clarithromycin (90.9%).

Distribution and antibiotic resistance of isolates from lower respiratory tract and blood cultures from patients in three Italian intensive care units: a 2-year comparison.

The distribution and antibiotic resistance of major pathogens isolated from patients in ICUs were studied by three Italian microbiological laboratories. Consecutive aerobic strains were collected over two different time periods from protected brushing bronchoscopy, broncho-alveolar lavage and blood cultures. A total of 420 strains were isolated during the first period (47.3% gram-negative and 52.7% gram-positive) and 412 over the second period (50.5% gram-negative and 49.5% gram-positive). Pseudomonas aeruginosa was the most frequently isolated organism from the respiratory tract followed by Staphylococcus aureus. Methicillin resistance was 47.9 and 44.5% in S. aureus and 63.0 and 65.1% in coagulase-negative staphylococci over the two periods. No glycopeptide-resistance was found in gram-positive organisms. Ceftazidime-resistance in Klebsiella pneumoniae was very high.

In-vitro activity of cefpodoxime proxetil (RU 51807): a comparative disk diffusion study on isolates from geriatric patients.

997 strains isolated from clinical specimens arrived at the "Pio Albergo Trivulzio" microbiology laboratory were tested using disks of cefpodoxime, amoxicillin + clavulanic acid, cefaclor, cefuroxime, ofloxacin, cotrimoxazole, ceftriaxone and cefalexin. Gram-positive strains were tested also with erythromycin, while gram-negative bacteria were tested against aztreonam. Cefpodoxime overall activity was well above the effectiveness of the other oral cephalosporins and on the same order as ceftriaxone and ofloxacin. Cefpodoxime proved to be also more active than the combination amoxicillin-clavulanic acid.

Microbiological patterns of four new imidazole derivatives.

The authors present an in vitro experimental study concerning the microbiological properties of four imidazole derivatives, with a piperazine group between two benzene rings. Seventy strains of Gram-positive and Gram-negative bacteria, 30 of yeasts, 14 of filamentous fungi and 10 strains of Trichomonas vaginalis were tested. The new compounds revealed a good inhibitory activity against Gram-positive bacteria, yeasts and dermatophytes. These results compare well with those obtained with the other known imidazoles. Moreover any mutagenic activity is absent.

Influence of sulbactam plus ampicillin on theophylline clearance.

The effect of sulbactam/ampicillin (500 mg/1000 mg) every 12 hours taken for seven days on the steady-state pharmacokinetics of theophylline was studied among 12 patients suffering from chronic obstructive pulmonary disease. Theophylline concentrations were measured serially for 12 h by the method of polarized immunofluorescence (Abbott TDx system). No influence of sulbactam/ampicillin was detectable on the theophylline half-life, clearance or volume of distribution. It was concluded that both drugs could be administered concomitantly without any dosage adjustment of theophylline.

[Controlled clinical trial of a new antibiotic "CM 9164" (Midecacin) in dental and stomatological practice]. / Sperimentazione clinica controllata di un nuovo antibiotico "CM 9164" (Midecacin) in campo odontostomatologico.

The action of a new antibiotic identified as CM 9164 ("Midecamycin") and provisionally called "Midecacin", has been experimented on patients admitted for dental conditions. The research was carried out on an open basis and erythromycin was used as a comparison. After a short review of the chemicophysical properties and toxicological and pharmacological features of Midecamycin, the purpose, materials and methods of the research, which was done on two groups of patients, are presented. The results demonstrated the therapeutics usefulness of the new antibiotic as its activity is certainly on a par if not greater than that of erythromycin whether considered "historically" or from the viewpoint of the comparison group. The tolerance of the antibiotic was clinically better than that of the other substances. The doses used were much lower than those required with erythromycin. On the basis of these results, the use of Midecamycin is therefore recommended in the treatment of Gram-positive infections in the dental field.

In vitro selection of antibiotic resistance in the probiotic strain Lactobacillus rhamnosus GG ATCC 53103.

Antibiotic resistance in probiotic strains is a matter of interest due to the increase in consumption of probiotic products. Many studies have evaluated the antibiotic susceptibility of lactobacilli or the presence of resistance determinants, while knowledge on selection of resistance during exposure to antibiotics is still limited. Our aim was to evaluate the behavior of Lactobacillus rhamnosus GG ATCC 53103, a well-known probiotic microorganism, during exposure to erythromycin, tetracycline, amoxicillin/ clavulanate and ciprofloxacin. Our study demonstrated that prolonged exposure to erythromycin and ciprofloxacin could select mutants with reduced susceptibility, even if these modifications in susceptibility could not be attributed to known antibiotic resistance genes or genetic mutations.