Minimum Inhibitory Concentration Of Chlorhexidine Research Articles

Effect of daily chlorhexidine bathing on acquisition of carbapenem-resistant Acinetobacter baumannii (CRAB) in the medical intensive care unit with CRAB endemicity

There is insufficient evidence for daily chlorhexidine bathing to reduce nosocomial spread of carbapenem-resistant Acinetobacter baumannii (CRAB) in endemic situations. An interrupted time series study was performed to evaluate the effect of daily chlorhexidine bathing on the acquisition of CRAB in a medical intensive care unit (ICU) with CRAB endemicity. There was a 14-month control period and 12-month chlorhexidine bathing period. Segmented Poisson regression analysis was performed to assess the impact of chlorhexidine bathing on the level and trend of the series of prevalence rates and incidence density. Also, chlorhexidine susceptibility testing was performed on CRAB isolates collected during the chlorhexidine bathing period. There was a 51.8% reduction of CRAB acquisition rates after an introduction of daily chlorhexidine bathing (44.0 vs 21.2 cases/1,000 at-risk patient days, P<.001). There was a significant reduction in the level (-0.604; 95% CI,-0.904to-0.305; P<.001) of incidence density of CRAB, whereas there was no significant change in both level and trend of CRAB prevalence rates. Minimum inhibitory concentration of chlorhexidine against a total of 98 CRAB isolates ranged from 8-64 μg/mL. Daily chlorhexidine bathing significantly reduces the acquisition of CRAB in a medical ICU with CRAB endemicity.

Long-term evaluation of the antimicrobial susceptibility and microbial profile of subgingival biofilms in individuals with aggressive periodontitis.

This study evaluates the antimicrobial susceptibility and composition of subgingival biofilms in generalized aggressive periodontitis (GAP) patients treated using mechanical/antimicrobial therapies, including chlorhexidine (CHX), amoxicillin (AMX) and metronidazole (MET). GAP patients allocated to the placebo (C, n = 15) or test group (T, n = 16) received full-mouth disinfection with CHX, scaling and root planning, and systemic AMX (500 mg)/MET (250 mg) or placebos. Subgingival plaque samples were obtained at baseline, 3, 6, 9 and 12 months post-therapy from 3–4 periodontal pockets, and the samples were pooled and cultivated under anaerobic conditions. The minimum inhibitory concentrations (MICs) of AMX, MET and CHX were assessed using the microdilution method. Bacterial species present in the cultivated biofilm were identified by checkerboard DNA-DNA hybridization. At baseline, no differences in the MICs between groups were observed for the 3 antimicrobials. In the T group, significant increases in the MICs of CHX (p < 0.05) and AMX (p < 0.01) were detected during the first 3 months; however, the MIC of MET decreased at 12 months (p < 0.05). For several species, the MICs significantly changed over time in both groups, i.e., Streptococci MICs tended to increase, while for several periodontal pathogens, the MICs diminished. A transitory increase in the MIC of the subgingival biofilm to AMX and CHX was observed in GAP patients treated using enhanced mechanical therapy with topical CHX and systemic AMX/MET. Both protocols presented limited effects on the cultivable subgingival microbiota.

SUSCEPTIBILIDADE DE AMOSTRAS CLÍNICAS DE PSEUDOMONAS AERUGINOSA A ANTIBIÓTICOS E A CLOREXIDINA

Backgound and Objectives: Aimed to investigate whether there is a possible association between antibiotic resistance and susceptibility to chlorhexidine of 65 clinical strains of Pseudomonas aeruginosa isolated from patients in a Brazilian hospital. Methods: The samples were identified by the MicroScan system and the sensitivity to antibiotics was performed by the disk diffusion technique. The minimum inhibitory concentration (MIC) of chlorhexidine was evaluated by broth dilution method and bactericidal activity at concentrations of 0.2% and 2%, was evaluated by the test suspension, according to the European Standard 1040. Results: All strains tested showed sensitivity to polymyxin, followed by piperacillin / tazobactam (75.4%), ceftazidime and cefepime (41.5%), tobramycin (36.9%), aztreonam and amikacin (33.8%), levofloxacin (30.8%), ciprofloxacin (29.2%), ofloxacin (27.3%), gentamicin (26.2%) and ceftriaxone (7.7%). The MIC of chlorhexidine ranged from 2.5 to 40 micrograms / ml, with MIC50 and MIC90 of 10 and 20 mg / ml. In a suspension test, the concentration of chlorhexidine in 2% destroy any bacterial cell inoculum of 65 samples. At the concentration of 0.2% chlorhexidine removed 24.2% (15/65) of samples. A sample showed reduced susceptibility chlorhexidine, ie, in the test suspension, the reduction of viable bacteria in the inoculum was less than 5 log10. Three other samples were very close to a logarithmic reduction of 5. Conclusion: In our study, the results of in vitro tests with chlorhexidine were homogeneous, seeming to indicate an association of biocide with multiple antibiotic resistance of P aeruginosa samples tested. Noteworthy is the finding of a sample of P. aeruginosa with reduced susceptibility to chlorhexidine use in dilution of 0.2%. KEYWORDS: Pseudomonas aeruginosa. Chlorhexidine. Resistance.

A periodontitis-associated multispecies model of an oral biofilm.

While single-species biofilms have been studied extensively, we know notably little regarding multispecies biofilms and their interactions. The purpose of this study was to develop and evaluate an in vitro multispecies dental biofilm model that aimed to mimic the environment of chronic periodontitis. Streptococcus gordonii KN1, Fusobacterium nucleatum ATCC23726, Aggregatibacter actinomycetemcomitans ATCC33384, and Porphyromonas gingivalis ATCC33277 were used for this experiment. The biofilms were grown on 12-well plates with a round glass slip (12 mm in diameter) with a supply of fresh medium. Four different single-species biofilms and multispecies biofilms with the four bacterial strains listed above were prepared. The biofilms were examined with a confocal laser scanning microscope (CLSM) and scanning electron microscopy (SEM). The minimum inhibitory concentrations (MIC) for four different planktonic single-species and multispecies bacteria were determined. The MICs of doxycycline and chlorhexidine for four different single-species biofilms and a multispecies biofilm were also determined. The CLSM and SEM examination revealed that the growth pattern of the multispecies biofilm was similar to those of single-species biofilms. However, the multispecies biofilm became thicker than the single-species biofilms, and networks between bacteria were formed. The MICs of doxycycline and chlorhexidine were higher in the biofilm state than in the planktonic bacteria. The MIC of doxycycline for the multispecies biofilm was higher than were those for the single-species biofilms of P. gingivalis, F. nucleatum, or A. actinomycetemcomitans. The MIC of chlorhexidine for the multispecies biofilm was higher than were those for the single-species biofilms of P. gingivalis or F. nucleatum. To mimic the natural dental biofilm, a multispecies biofilm composed of four bacterial species was grown. The 24-hour multispecies biofilm may be useful as a laboratory dental biofilm model system.

Reduced susceptibility to chlorhexidine among extremely-drug-resistant strains of Klebsiella pneumoniae

Over the last decade, extremely-drug-resistant (XDR) strains of Klebsiella pneumoniae have emerged worldwide, mainly as a result of patient-to-patient spread. The predominant clone, sequence type 258 (ST258), is associated with high morbidity and mortality, and is a worldwide threat to public health. It was hypothesized that reduced susceptibility to chlorhexidine, the most widely used hospital disinfectant, may contribute to the endemic nature of this strain. To characterize and compare the susceptibility of the epidemic K.pneumoniae clone ST258 and non-epidemic K.pneumoniae clones to chlorhexidine. The minimum inhibitory concentration (MIC) of chlorhexidine was determined in 126 XDR K.pneumoniae clinical isolates using agar dilution. Expression of three different efflux pumps -cepA, acrA and kdeA - was investigated in the absence and presence of chlorhexidine using quantitative real-time polymerase chain reaction. Heteroresistance to chlorhexidine was identified using population analysis. The MIC of chlorhexidine was higher for K.pneumoniae ST258 (N=70) than other K.pneumoniae sequence types (N=56); 99% of ST258 isolates had MICs >32μg/mL, compared with 52% of other K.pneumoniae sequence types (P<0.0001). Reduced susceptibility to chlorhexidine appeared to be independent of the expression of cepA, acrA and kdeA efflux pumps. Chlorhexidine-resistant subpopulations were observed independent of the bacterial sequence type or the MIC. Reduced susceptibility to chlorhexidine may contribute to the success of XDR K.pneumoniae as a nosocomial pathogen, and may provide a selective advantage to the international epidemic strain K.pneumoniae ST258. The heterogeneous nature of chlorhexidine-resistant subpopulations suggests that this phenomenon might not be rendered genetically.

Inhibition of the growth in vitro of Trichophyton mentagrophytes, Trichophyton erinacei and Microsporum persicolor by miconazole and chlorhexidine

An agar dilution technique was used to assess the minimum inhibitory concentrations (MICs) of miconazole, chlorhexidine and a 1:1 combination of both agents for 9 isolates of Trichophyton mentagrophytes, 9 isolates of Trichophyton erinacei and 5 isolates of Microsporum persicolor. MICs of chlorhexidine did not vary significantly between the three dermatophyte species tested, but the MICs of miconazole alone and in combination with chlorhexidine for T. erinacei were significantly greater that those for T. mentagrophytes and M. persicolor. A synergistic drug interaction was noted with one isolate of T. erinacei and one isolate of M. persicolor. An additive effect was demonstrated for 13 isolates (5 T. mentagrophytes, 6 T. erinacei, 2 M. persicolor), and indifference was noted in 8 isolates (4 T. mentagrophytes, 2 T. erinacei, 2 M. persicolor). Although synergy was less often seen when compared with a previous study of Microsporum canis, the synergistic or additive effects seen with the majority (15 out of 23) of isolates studied in vitro provides a rationale for the combined use of miconazole and chlorhexidine in the adjunctive topical therapy of dermatophytosis caused by T. mentagrophytes, T. erinacei and M. persicolor.

Susceptibility of some oral microorganisms to chlorhexidine and paramonochlorophenol

Since the use of antimicrobial agents is required in endodontic therapies, this study aimed at determining the minimum inhibitory concentrations (MICs) of chlorhexidine digluconate and paramonochlorophenol (PMC) against microorganisms commonly found in endodontic infections. Both agents were tested by agar dilution tests against Pseudomonas aeruginosa, Staphylococcus aureus, Enterococcus faecalis, Escherichia coli, Candida albicans, Prevotella intermedia, Porphyromonas gingivalis, Porphyromonas endodontalis, Prevotella denticola and Prevotella melaninogenica. The MIC of chlorhexidine ranged from 2.67 to 80.00 microg/ml, and the MIC of PMC from 46.67 to 213.33 microg/ml. The highest MIC value of PMC was detected for E. faecalis whereas E. coli was the most susceptible microorganism to this agent. The highest MIC values of chlorhexidine were observed for P. aeruginosa whereas E. coli and P. denticola were the most susceptible microorganisms to this agent. Since the MIC values observed are much lower than the concentrations currently used in the endodontic therapy, it is suggested that both agents are effective in reducing the microbiota in the root canal.

IN-VITRO ANTIMICROBIAL ACTIVITY OF CHLORHEXIDINE POLYMERIC FILMS

The minimum inhibitory concentration (MIC) of chlorhexidine for Staphylococcus aureus, Bacillus subtilus, Escherichia Coli and Candida albicans was studied. Chlorhexidine polymeric films composed of ethylcellulose (EC) and hydroxypropyl methyl- cellulose (HPMC) in a ratio of 8:2 were prepared. The inhibition zone diameters of chlorhexidine polymeric film were compared with that of chlorhexidine gauze dressing. Also, the inhibition zone sizes of different concentrations of chlorhexidine (0.5, 1 and 5%) in films plasticized with 20% propylene glycol, in presence of 10% Tween 80 as enhancer, or plasticized with 20% polyethylene glycol 400 were evaluated. Results indicated that the MIC of chlorhexidine was ranged from 1 to 1.8 ug/ml. Also the inhibition zone diameters of the selected polymeric film was higher than that of gauze dressing. There were correlation between drug concentrations and inhibition zone sizes. Also polymeric film containing 20% propylene glycol and 10% Tween 80 showed relatively higher response than polymeric film containing 20% ployethylene glycol 400. It can be concluded that the tested microorganisms were susceptible to chlorhexidine and the use of polymeric films as drug delivery system enhanced chlorhexidine in-vitro antimicrobial activity. Accordingly, it was recommended to use chlorhexidine polymeric films for topical antisepsis.

Daily scrub with chlorhexidine reduces skin colonization by antibiotic-resistant Staphylococcus epidermidis

The aim of this study was to establish whether long-term use of chlorhexidine would prevent skin colonization by antibiotic-resistant Staphylococcus epidermidis. Ten nurses, working on a ward for haematological disorders, volunteered to participate in the test. They washed one arm every morning for three weeks with chlorhexidine gluconate, (‘Hibiscrub’ ICI Pharmaceuticals). The other arm served as a negative control. Samples from the antecubital fossa of both arms were taken two to three times a week during the wash period and two weeks thereafter, giving a total of 216 samples. The appearance of resistant S. epidermidis with different antibiograms was analysed. During the wash period the total bacterial counts and the counts of the resistant S. epidermidis strains on the test arm were both about one-tenth of those on the control arm, a significant difference ( P < 0·05). Moreover, there were significantly fewer resistant S. epidermidis on the test arm, 1·3 per sample, than on the control arm, 2·5 per sample ( P < 0·01). Most of the resistant S. epidermidis were only found once or a few times on the same site, after which they disappeared, though a few persisted on the skin even during ‘Hibiscrub’ washing. In an agar dilution test, chlorhexidine minimum inhibitory concentrations (MICs) of persisting strains were the same as for strains disappearing from the skin following ‘Hibiscrub’ washing, 1·0 or 2·0 mg 1 −1, but somewhat higher than MICs of strains isolated from healthy carriers outside the hospital whose MICs were 0·5 mg 1 −1. The relative contribution to the skin counts by those S. epidermidis strains found only occasionally were compared with those found repeatedly but no difference in reduction was found between these categories during ‘Hibiscrub’ washing.

The in vitro effects of chlorhexidine on subgingival plaque bacteria.

The purpose of this study was to determine the susceptibility to chlorhexidine of a range of bacteria which may be isolated from subgingival plaque. In addition, the effect of chlorhexidine on the survival of bacteria in subgingival plaque samples from patients with chronic inflammatory periodontal disease was investigated. The minimum inhibitory concentration (MIC) of chlorhexidine for 52 strains of bacteria ranged from 8 to 500 micrograms/ml. The modal value of the MIC was found to be 62 micrograms/ml, 64% of the strains tested being inhibited at this concentration. A concentration of 250 micrograms/ml of chlorhexidine inhibited the growth of all bacteria in the 25 subgingival plaque samples investigated. The MIC of chlorhexidine for the samples ranged from 31 to 250 micrograms/ml, the modal value being 125 micrograms/ml.

Assessment of susceptibility of plaque bacteria to chlorhexidine after six months' oral use

Changes in the susceptibility of plaque bacteria to chlorhexidine treatment were investigated by determining the minimum inhibitory concentration (MIC) of chlorhexidine on two kinds of bacteria commonly found in supragingival plaque. Streptococci and actinomyces were isolated from plaque samples collected from subjects participating in a clinical trial comparing a 0.12% chlorhexidine gluconate mouthrinse to a placebo mouthrinse. The isolates were inoculated onto media containing varying concentrations of chlorhexidine to determine the MIC of chlorhexidine during the six‐month treatment period and three months after cessation of treatment. While significant differences in the sensitivity of these two bacterial strains to chlorhexidine were seen sporadically, no consistent pattern of resistance emerged. It was concluded that prolonged use of a 0.12% chlorhexidine gluconate mouthrinse did not alter the composition of the oral microflora toward organisms less sensitive to chlorhexidine. This conclusion was further supported by the clinical findings in this trial that showed chlorhexidine's effects on plaque and gingivitis indices were maintained throughout the six‐month treatment period. Three months after the mouthrinse was discontinued, the MIC's of chlorhexidine on isolates from placebo‐treated and chlorhexidine‐treated subjects were the same as pretreatment values. Thus, no residual change in resistance was observed nor were there any adverse changes in the microbial profile.

In vitro susceptibility of hospital isolates of various bacterial genera to chlorhexidine

Chlorhexidine (Hibitane@) is an effective agent against both Gram-positive and Gram-negative bacteria and is widely used in hospitals for skin disinfection. The concentrations recommended by the manufacturer range from 100-40,OOO mg 1-l in liquid preparations and up to 10,000 mg 1 -l in solid or semi-solid preparations. Originally, Davies et al. (1954) reported that lo-15 mg l-1 of chlorhexidine was required to inhibit the growth of Gram-negative species but recently there have been a number of reports in the literature of resistant strains of Proteus and Providencia spp. (Stickler and Thomas, 1980), Serratia marcescens (Marrie and Costerton, 1981) and Pseudomonas aeruginosa (Nakahara and Kozokue, 1982) with minimum inhibitory concentration (MIC) values in excess of 200 mg 1 -l. We have investigated, by a standard test, the MIC and minimum bactericidal concentration (MBC) of chlorhexidine against a wide range of bacterial genera, in particular those bacteria which are most frequently isolated from hospitalacquired infections (Meers et al., 1981).