Anaerobic and aerobic skin bacteria before and after skin-disinfection with chlorhexidine: an experimental study in volunteers

Repertoire of human breast and milk microbiota: a systematic review

Breastfeeding is a major determinant of human health. Breast milk is not sterile and ecological large-scale sequencing methods have revealed an unsuspected microbial diversity that plays an important role. However, microbiological analysis at the species level has been neglected while it is a prerequisite before understanding which microbe is associated with symbiosis or dysbiosis, and health or disease. We review the currently known bacterial repertoire from the human breast and milk microbiota using a semiautomated strategy. Total 242 articles from 38 countries, 11,124 women and 15,489 samples were included. Total 820 species were identified mainly composed of Proteobacteria and Firmicutes. We report variations according to the analytical method (culture or molecular method), the anatomical site (breast, colostrum or milk) and the infectious status (healthy control, mastitis, breast abscess, neonatal infection). In addition, we compared it with the other human repertoires. Finally, we discuss its putative origin and role in health and disease.

Evaluation of Skin Antisepsis Prior to Blood Culture in Neonates

In our Intensive Care Nursery, coagulase-negative staphylococcus is the most frequent blood culture isolate. As skin antisepsis is critical in preventing blood culture contamination, we examined the efficacy of the chlorhexidine tincture (CH) used in our nursery for this purpose. Staphylococcus epidermidis colonized the forearms of 88% of infants tested, in a mean density of 104 organisms/cm2. Following a 60-second application of CH (0.5% in 70% ethanol), bacterial growth from forearm skin remained abundant in 15/38 infants (39.4%). Cleansing with 70% isopropyl alcohol, followed by CH as above, left abundant residual growth in only 1/37 infants (2.7%) (P<0.001). All 136 S. epidermidis tested were susceptible to CH (MIC<5(μg/ml) and 14 of 15 exposed to CH 0.02% were rapidly killed (≥98% fall in viable counts within 90 sec). We conclude that two-phase antisepsis using isopropanol followed by CH is a more effective preparation for blood culture in neonates than is CH alone.

Enhanced chlorhexidine skin penetration with eucalyptus oil

BACKGROUND

Chlorhexidine digluconate (CHG) is a widely used skin antiseptic, however it poorly penetrates the skin, limiting its efficacy against microorganisms residing beneath the surface layers of skin. The aim of the current study was to improve the delivery of chlorhexidine digluconate (CHG) when used as a skin antiseptic.

METHOD

Chlorhexidine was applied to the surface of donor skin and its penetration and retention under different conditions was evaluated. Skin penetration studies were performed on full-thickness donor human skin using a Franz diffusion cell system. Skin was exposed to 2% (w/v) CHG in various concentrations of eucalyptus oil (EO) and 70% (v/v) isopropyl alcohol (IPA). The concentration of CHG (μg/mg of skin) was determined to a skin depth of 1500 μm by high performance liquid chromatography (HPLC).

RESULTS

The 2% (w/v) CHG penetration into the lower layers of skin was significantly enhanced in the presence of EO. Ten percent (v/v) EO in combination with 2% (w/v) CHG in 70% (v/v) IPA significantly increased the amount of CHG which penetrated into the skin within 2 min.

CONCLUSION

The delivery of CHG into the epidermis and dermis can be enhanced by combination with EO, which in turn may improve biocide contact with additional microorganisms present in the skin, thereby enhancing antisepsis.

Bacterial skin contamination before and after surgical preparation of the foot, ankle, and lower leg in patients with diabetes and intact skin versus patients with diabetes and ulceration: a prospective controlled therapeutic study

Eradication of bacterial flora from the foot, especially the nailfolds and toe webspaces, through surgical preparation remains a challenge. All previous studies have involved healthy patients undergoing elective foot and ankle surgery or healthy volunteers. However, the patient with diabetes is considered an immunocompromised host with decreased ability to combat invasive bacterial infections. The use of an efficacious surgical preparation is therefore of paramount importance. The author conducted a prospective study involving patients with diabetes with and without ulceration who underwent the current "best evidence available" surgical preparation (i.e., chlorhexidine gluconate [4%] scrub followed by alcohol impregnated with iodine [1%] solution). Qualitative aerobic cultures before and after completion of this surgical preparation technique were obtained from the hallux nailfold; second, third, and fourth toe webspaces (as one culture); and distal anterior tibia. A total of 120 organisms were cultured before surgical preparation with 64 in the elective group and 56 in the ulcerated group. The most commonly isolated organism was methicillin-resistant Staphylococcus epidermidis, which was identified in 46 pre-preparation cultures (38.3%). This was followed by methicillin-sensitive S. epidermidis (16.7%) and "other" organisms (10.0%). There was a significant reduction for both numbers of organisms identified and positive cultures for the 3 most commonly isolated organisms after surgical preparation. Based on the results of this study, the surgical preparation used here appears to be an efficacious surgical preparation technique for eradicating aerobic bacterial pathogens from the foot in patients with diabetes both with and without ulceration. The high incidence of methicillin-sensitive and methicillin-resistant S. epidermidis found in this patient population is a cause for concern, especially when metallic fixation is intended to be implanted.

Pitfalls in efficacy testing--how important is the validation of neutralization of chlorhexidine digluconate?

Background

Effective neutralization of active agents is essential to obtain valid efficacy results, especially when non-volatile active agents like chlorhexidine digluconate (CHG) are tested. The aim of this study was to determine an effective and non-toxic neutralizing mixture for a propan-1-ol solution containing 2% CHG.

Methods

Experiments were carried out according to ASTM E 1054-02. The neutralization capacity was tested separately with five challenge microorganisms in suspension, and with a rayon swab carrier. Either 0.5 mL of the antiseptic solution (suspension test) or a saturated swab with the antiseptic solution (carrier test) was added to tryptic soy broth containing neutralizing agents. After the samples were mixed, aliquots were spread immediately and after 3 h of storage at 2 – 8°C onto tryptic soy agar containing a neutralizing mixture.

Results

The neutralizer was, however, not consistently effective in the suspension test. Immediate spread yielded a valid neutralization with Staphylococcus aureus, Staphylococcus epidermidis and Corynebacterium jeikeium but not with Micrococcus luteus (p < 0.001) and Candida albicans (p < 0.001). A 3-h storage period of the neutralized active agents in suspension resulted in significant carry-over activity of CHG in addition against Staphylococcus epidermidis (p < 0.001) and Corynebacterium jeikeium (p = 0.044). In the carrier test, the neutralizing mixture was found to be effective and non toxic to all challenge microorganisms when spread immediately. However, after 3 h storage of the neutralized active agents significant carry-over activity of CHG against Micrococcus luteus (p = 0.004; Tukey HSD) was observed.

Conclusion

Without effective neutralization in the sampling fluid, non-volatile active ingredients will continue to reduce the number of surviving microorganisms after antiseptic treatment even if the sampling fluid is kept cold straight after testing. This can result in false-positive antiseptic efficacy data. Attention should be paid during the neutralization validation process to the amount of antiseptic solution, the storage time and to the choice of appropriate and sensitive microorganisms.

Chlorhexidine provides superior skin decontamination in foot and ankle surgery: a prospective randomized study

Feet are prone to bacterial contamination. We hypothesized that chlorhexidine scrub and isopropyl alcohol paint provide superior local flora reduction than povidone-iodine scrub and paint. Patients with intact, uninfected skin having clean elective foot and ankle surgery were prospectively enrolled and randomly assigned to skin preparation with povidone-iodine (Group 1) or chlorhexidine scrub and isopropyl alcohol paint (Group 2). Culture swabs (aerobic, anaerobic, acid fast, fungus, and routine antibiotic sensitivity) were taken from all web spaces, nail folds, toe surfaces, and proposed surgical incision sites. One-hundred twenty-seven patients were enrolled (mean age, 46 years; range, 16-85 years). Sixty-seven patients were assigned to Group 1; 60 patients were assigned to Group 2. In Group 1, 53 of 67 patients (79%) had positive cultures; in Group 2, 23 of 60 patients (38%) had positive cultures. These data indicate that chlorhexidine and alcohol provide better reduction in bacterial carriage than povidone-iodine. Based on these data, we recommended chlorhexidine as the surgical preparatory agent for the foot and ankle.

LEVEL OF EVIDENCE

Therapeutic study, Level I-1a (significant difference). See the Guidelines for Authors for a complete description of levels of evidence.

Comparison of in vivo antibacterial activity of hydro-alcoholic solutions of hexamidine and of chlorhexidine

Samples of cutaneous flora were obtained from the antecubital fossa of 20 healthy volunteers before and after treatment with hydro-alcoholic solutions of chlorhexidine (CHX) and of hexamidine (HXM). Percentage reductions in bacterial flora were statistically greater (p less than 0.001) after CHX (99 to 100%) than after HXM (about 70 to 90%). Furthermore, CHX had a smaller disturbing effect upon the natural balance of the bacterial population than HXM with a more rapid return towards the initial proportions of the different organisms one hr after treatment.

A review of the literature on use of chlorhexidine in dentistry

In addition to its plaque-inhibiting effect, chlorhexidine possesses other properties beneficial for use in dentistry. These effects are outlined, and specific recommendations are given regarding chlorhexidine's use by general practitioners. The side effects of long-term use, such as staining, and the availability of chlorhexidine also are discussed.

Effect of antiseptic agents on skin flora of the perineum of men with spinal cord injury

Male patients with spinal cord injury are frequently colonized with P. aeruginosa and K. pneumoniae on the perineum. Regular bathing with bar soap has not influenced this colonization. We have attempted to remove these bacteria using antiseptic agents. The number of P. aeruginosa, K. pneumoniae and total aerobic bacteria on the perineum and the penile shaft was determined before and after cleaning with bar soap, chlorhexidine, povidone-iodine and pHresh. Povidone-iodine and chlorhexidine had no advantage over bar soap or pHresh in the removal of P. aeruginosa or K. pneumoniae from the perineum of patients with spinal cord injury.

Whole body disinfection with chlorhexidine: is shower bathing more effective than bathing?

Whole body washing with chlorhexidine gluconate solution BP (equivalent to 4 per cent w/v chlorhexidine gluconate) achieved a variable reduction in total skin microbial colony counts whether applied in a standard bath or a shower bath. No significant differences between the two techniques were demonstrable.

Total body bathing with 'Hibiscrub' (chlorhexidine) in surgical patients: a controlled trial

Total body bathing with 'Hibiscrub' (chlorhexidine-detergent) solution was compared with non-medicated soap in 224 patients admitted for surgery. Some 9.6 per cent of patients were found to be nasal carriers of Staphylococcus aureus on admission but 17.3 per cent were colonized at some time during their inpatient stay. Skin colonization by Staph, aureus was only seen in four patients (2 per cent), three were cleared by 'Hibiscrub' bathing but carriage persisted in the other patient who used non-medicated soap. A greater reduction in the total bacterial count on the skin and in the perianal region was seen in patients using 'Hibiscrub'. An increase in the bacterial count was frequently seen in patients using non-medicated soap. Postoperative staphylococcal wound infection occurred in nine patients (4-0 per cent) but nasal or skin carriage was only present in two patients. Although there was no difference in the rates of infection using 'Hibiscrub' or ordinary soap, pre-operative bathing with 'Hibiscrub' may be beneficial as there is a greater reduction in the total bacterial count. The use of non-medicated soap is of dubious value and may even increase the numbers of bacteria on the skin.

Contamination of urological wounds by aerobic bacteria. Transvesical prostatectomy used as a model

The density of aerobic bacteria in the subcutaneous wound was quantified by the velvet pad rinse technique before (first stage) and after (second stage) opening of the bladder in 13 patients undergoing transvesical prostatectomy. Six patients had bacteria in the urine preoperatively (group A) and the same bacteria were isolated from bladder puncture during the operation and during second stage. Seven patients (group B) had sterile urine preoperatively and the bacteria isolated during first and second stage were commensals of the skin and the upper-respiratory tract. The bacterial density in group B was median 3.1 viable counts (v.c.) x 10(-1)/cm2 during first stage rising to median 4.7 v.c. x 10-1/cm2 during second stage, while group A showed an increase from median 4.3 v.c. x 10(-1)/cm2 during first stage to median 169,5 v.c. x 10(-1)/cm2 during second stage. The results of the study indicate the possibility of using selective antibiotic prophylaxis, with the relevant antibiotic for the bacteria isolated in the urine preoperatively, to reduce postoperative wound infection in urological surgery with opening of the urinary bladder.

A bacteriological evaluation of a programme for preoperative total body-washing with chlorhexidine gluconate performed by patients undergoing orthopaedic surgery

Twenty-eight orthopaedic patients were taught to wash their entire bodies with chlorhexidine gluconate on two consecutive days preoperatively, starting in their homes. The operation field was also washed a third time. A bacteriological evaluation was performed using contact plates. A significant reduction of the skin flora, including Staph. aureus, was registered. No adverse side effects of total body-washing were observed.

Propionibacteria as a cause of shunt and postneurosurgical infections

Propionibacterium acnes was isolated from postoperative specimens from nine neurosurgical patients. The role of P. acnes in postneurosurgical infection is discussed.

Effect of plastic skin and wound drapes on the density of bacteria in operation wounds

Operation wounds were sampled quantitatively by the velvet pad rinse technique to determine the effect of impervious plastic skin and wound drapes on the density of bacteria. A controlled trial (clean operations) revealed no significant difference between the bacterial density of herniotomy wounds for which the skin had been covered with adhesive plastic drapes, and the bacterial density of wounds in which skin drapes had not been used. The bacterial density in the wounds did not differ significantly from that on the adjacent skin; both densities were slightly higher at the end of operation than at the beginning. Within the operation wound, sites of low bacterial density were close to sites with a high density. Staphylococcus epidermidis predominated, while Staphylococcus aureus occurred only once; intestinal species were not isolated. In another controlled trial (potentially contaminated operations) plastic wound drapes gave an equally high reduction in bacterial density before closure of laparotomy wounds after either truncal vagotomy and pyloroplasty or gastric and colorectal operations. The reduction in the density of intestinal species was close to 100 per cent and did not differ significantly from that of alpha-haemolytic streptococci, the density of this species being significantly more reduced than that of staphylococci, diphteroids and bacilli. It is concluded that plastic skin drapes were without influence on the species and density of bacteria in operation wounds. Plastic wound drapes, on the other hand, considerably reduced not only exogenous but in particular endogenous bacteria, which otherwise would have remained in the operation wounds.

Flaming of biopsy specimens for bacteriological culture: surface sterilization and effect on bacteria in the underlying tissue

The effect of flaming (i.e. dipping biopsy specimens in alcohol and igniting them by drawing them rapidly through an open flame) on the reduction of bacterial surface contamination and on true bacterial concentrations in underlying tissue was investigated in different sizes of liver biopsy specimens in an experimental model suitable for quantitative and statistical calculations. Different degrees of surface contamination and of bacterial concentrations in underlying tissue were examined after a varying number of flaming procedures, the study comprising a total of 400 biopsy specimens. The flaming procedure repeated three times was able to eradicate a surface contamination of up to 10(4) E. coli per biopsy specimen, whereas a contamination of 10(6) E. coli per biopsy specimen was reduced to only 10(3) E. coli. Undesirable reduction in the true bacterial concentrations in tissue did not invalidate the method from a quantitative bacteriological point of view, since the median reduction in bacteria per gram tissue in biopsy specimens of 1 cm3 size did not exceed a factor of 3 after three repeated flamings. It is concluded that in regard to surface sterilization the method is unreliable as a routine in postmortem bacteriological studies.