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.

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.

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.

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.

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.

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.

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.

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.

Antibacterial activity of cefditoren against major community-acquired respiratory pathogens recently isolated in Italy.

In this study we evaluated the in vitro activities of cefditoren--a broad-spectrum oral cephalosporin--and other comparator agents against 2,396 fresh isolates from community-acquired respiratory tract infections, collected from 6 clinical Italian microbiology laboratories. On penicillin-susceptible pneumococci and Streptococcus pyogenes, cefditoren demonstrated to be the most active antibiotic (MIC(90)values of 0.03 and 0.06 mg/L respectively), showing only a slight decrease in potency on penicillin-intermediate and resistant pneumococci (MIC(90)value 0.5 mg/L, 1.0 mg/L respectively). All the other comparators displayed MIC(90 )values of 4 - 8 mg/L for penicillins and of 4 to >64 mg/L for the oral cephalosporins. Cefditoren and levofloxacin were the most active against MSSA (MIC(90)0.5 mg/mL). Cefditoren displayed a uniformly potent inhibitory activity (MIC(90)of 0.03 mg/L) against all strains of Haemophilus influenzae, regardless of their ampicillin resistance (mediated or not by beta-lactamase production), while against Moraxella catarrhalis MIC(90)values were higher against beta-lactamase-positive (0.25 mg/L). Cefditoren was active also against Klebsiella pneumoniae and Escherichia coli : in this case its activity was comparable with that of levofloxacin. In conclusion, cefditoren, due to its potent activity, is a new effective therapeutic option for the treatment of respiratory tract infections.

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.

Pharmacodynamics of levofloxacin and ciprofloxacin in a murine pneumonia model: peak concentration/MIC versus area under the curve/MIC ratios.

During the last decade some studies have shown that the area under the curve (AUC)/MIC ratio is the pharmacodynamic index that best predicts the efficacies of quinolones, while other studies suggest that the predictive value of the peak concentration/MIC (peak/MIC) ratio is superior to the AUC/MIC ratio in explaining clinical and microbiological outcomes. In classical fractionated dose-response studies with animals, it is difficult to differentiate between the AUC/MIC ratio and the peak/MIC ratio because of colinearity. Three different levofloxacin and ciprofloxacin dosing regimens were studied in a neutropenic mouse pneumonia model. The different regimens were used with the aim of increasing the AUC/MIC ratio without changing the peak/MIC ratio and vice versa. The first regimen (RC) consisted of daily doses of 5 up to 160 mg/kg of body weight divided into one, two, or four doses. In the second regimen (R0), mice were given 1.25 mg/kg every hour from 1 to 23 h, while the dose given at 0 h was 2.5, 5, 10, 20, 40, or 80 mg/kg. In the third regimen (R11), mice also received 1.25 mg/kg every hour from 0 to 23 h; but in addition, they also received 2.5, 5, 10, 20, 40, or 80 mg/kg at 11 h. The level of protein binding was also evaluated. The results indicate that the unbound fraction (f(u)) was concentration dependent for both levofloxacin and ciprofloxacin and ranged from approximately 0.67 to 0.88 for both drugs between concentrations of 0.5 and 80 mg/liter. The relationships between the AUC/MIC ratio and the number of CFU were slightly better than those between the peak/MIC ratio and the number of CFU. There was no clear relationship between the amount of time that the concentration remained above the MIC and effect (R(2) < 0.1). For both drugs, the peak/MIC ratio that resulted in a 50% effective concentration was lower for the R0 and R11 dosing regimens, indicating the importance of the AUC/MIC ratio. The same was true for the static doses. Survival studies showed that for mice treated with the low doses the rate of survival was comparable to that for the controls, but with the higher doses the rate of survival was better for mice receiving the R0 regimen. We conclude that for quinolones the AUC/MIC ratio best correlates with efficacy against pneumococci and that the effect of the peak/MIC ratio found in some studies could be partly explained by concentration-dependent protein binding.

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.

Sensitivity to sparfloxacin and other antibiotics, of Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis strains isolated from adult patients with community-acquired lower respiratory tract infections: a European multicentre study. SPAR Study Group. Surveillance Programme of Antibiotic Resistance.

A survey of resistance to sparfloxacin was carried out in ten European countries, namely Slovakia, France, Germany, Great Britain, Hungary, the Republic of Ireland, Italy, The Netherlands, Portugal and Spain. Respiratory samples were collected from 4297 patients with lower respiratory tract infections and cultured for the presence of Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis. Altogether 2101 strains were isolated and tested for their susceptibility to sparfloxacin, ciprofloxacin, erythromycin, tetracycline and penicillin G (S. pneumoniae) or amoxycillin (H. influenzae and M. catarrhalis). Each country tested strains using methods commonly used in that country, and with breakpoints selected based on those used in that country. Penicillin resistance in pneumococci was seen in those countries in which it had been reported previously, namely Spain, France and Hungary. Only four strains of pneumococci were resistant to sparfloxacin (MIC > or = 2 mg/L), while ciprofloxacin-resistant strains were isolated more frequently, particularly in the Republic of Ireland and Hungary. Almost all of the strains of H. influenzae tested were resistant to erythromycin, (MIC50 > or = 4 mg/L), but all strains were highly sensitive to sparfloxacin (MIC90 < or = 0.06 mg/L). The number of strains of H. influenzae producing beta-lactamase varied between countries, whereas most strains of M. catarrhalis produced beta-lactamase. In M. catarrhalis, erythromycin and tetracycline resistance was rare, but sensitivity to amoxycillin varied. Sparfloxacin was particularly active against H. influenzae and M. catarrhalis, and was the most active compound tested. Overall, the activity of sparfloxacin was greater than that of ciprofloxacin against all three pathogens, and resistance to it was rare.