Survival of gram-negative and gram-positive bacteria artificially applied on the hands

A process optimization approach for microwave vacuum drying of concentrated skim milk

Microwave vacuum drying (MVD) of concentrated skim milk and its resulting powder properties have been studied to a very limited extent. To explore the potential of this technology for the manufacture of milk powder, MVD of concentrated skim milk (37.5% total solids) was evaluated with respect to product properties and drying efficiency. A custom factorial design was used to optimize drying parameters, which enabled us to find optimal drying conditions with a minimal number of drying experiments (16). Vacuum level (3.3-13.3 kPa), specific power input (0.86-1.72 W·g^-1), and product layer thickness (1-4 mm) were studied as factors. Total drying time, product foaming at the beginning of the process, product temperature in the last drying interval, browning, insolubility index, and calculated product yield were used as responses to identify optimal MVD processing parameters. Optimal drying of concentrated skim milk that maximized yield and minimized drying time while maintaining good product quality was achieved at a layer thickness of 2 mm, pressure of 6.0 kPa, and a specific power input of 1.29 W·g^-1. Under constant power output, layer thickness was found to be the most important processing parameter to control product temperature during the final drying stage. Maximum product temperatures below 55°C yielded powder with good solubility. The findings of this exploratory study for MVD of concentrated skim milk yield important information and guidelines for production of good quality milk powders or preservation of starter cultures in a dairy matrix such as infant formula.

Isolation and identification of microorganisms associated with automated teller machines on Federal Polytechnic Ede campus

Automated Teller Machines (ATM) are visited everyday by millions of people. This machine is accessible to the general public irrespective of class, age or race. The contact point of all ATM machines is the hand which on their own are ‘vaults’ of microorganisms. An elaborate survey was taken for complete assessment of possible microbial contamination in the Federal Polytechnic Ede campus. Selected ATM machines on campus were used as case study to characterize, identify and determine the degree of bacterial contamination of microorganisms and their potential as reservoir of microbes. Swabs were collected from each ATM screen, buttons, floor, user’s hand, and exposure of plates. After collection of the samples, they were plated in nutrient agar. The results showed the presence of increased bacterial count subsequently, most pathogens on characterization revealed the genus of the particular organisms E. coli, Pseudomonas, Staphylococcus aureus, Klebsiella, Micrococcus, Salmonella and Serratia. The study showed the potential hazard inherent in ATM machine usage and draws attention to our level of hand hygiene compliance.

Asymmetric transfer efficiencies between fomites and fingers: Impact on model parameterization

BACKGROUND

Healthcare-associated infections (HAIs) affect millions of patients every year. Pathogen transmission via fomites and healthcare workers (HCWs) contribute to the persistence of HAIs in hospitals. A critical parameter needed to assess risk of environmental transmission is the pathogen transfer efficiency between fomites and fingers. Recent studies have shown that pathogen transfer is not symmetric. In this study,we evaluated how the commonly used assumption of symmetry in transfer efficiency changes the dynamics of pathogen movement between patients and rooms and the exposures to uncolonized patients.

METHODS

We developed and analyzed a deterministic compartmental model of Acinetobacter baumannii describing the contact-mediated process among HCWs, patients, and the environment. We compared a system using measured asymmetrical transfer efficiency to 2 symmetrical transfer efficiency systems.

RESULTS

Symmetric models consistently overestimated contamination levels on fomites and underestimated contamination on patients and HCWs compared to the asymmetrical model. The magnitudes of these miscalculations can exceed 100%. Regardless of the model, relative percent reductions in contamination declined after hand hygiene compliance reached approximately 60% in the large fomite scenario and 70% in the small fomite scenario.

CONCLUSIONS

This study demonstrates how healthcare facility-specific data can be used for decision-making processes. We show that the incorrect use of transfer efficiency data leads to biased effectiveness estimates for intervention strategies. More accurate exposure models are needed for more informed infection prevention strategies.

Removal of Escherichia coli and Enterococcus faecalis after Hand Washing with Antimicrobial and Nonantimicrobial Soap and Persistence of These Bacteria in Rinsates

Food handlers are important sources of contamination in the agricultural environment. This study was conducted (i) to evaluate the activity of antimicrobial soaps against Escherichia coli and Enterococcus faecalis using a hand washing model with soiled hands and (ii) to determine the survival and persistence of these bacteria in rinsates. Sterilized agricultural soil from tomato and pepper farms was inoculated with E. coli or E. faecalis at 10³ or 10⁶ CFU/g. Decontaminated hands were placed in contact with contaminated soil for 2 min and were then washed with soaps with or without antimicrobial compounds (citric extracts, chloroxylenol, triclosan, or chlorhexidine gluconate). As the control, hands were washed with sterile distilled water. The levels of bacteria remaining on the hands and recovered from the rinsates were determined using a membrane filtration method and selective media. Antimicrobial soaps removed levels of E. coli similar to those removed by distilled water and nonantimicrobial soap on hands contaminated with E. coli at 10³ CFU/g. However, when hands were contaminated with E. coli at 10⁶ CFU/g, more E. coli was removed with the chlorhexidine gluconate soap. When hands were contaminated with E. faecalis at 10³ CFU/g, bacteria were removed more effectively with soaps containing chloroxylenol or chlorhexidine gluconate. When hands were contaminated with E. faecalis at 10⁶ CFU/g, all of the antimicrobial soaps were more effective for removing the bacteria than were distilled water and nonantimicrobial soap. E. coli grew in all of the hand washing rinsates except that containing triclosan, whereas E. faecalis from the 10⁶ CFU/g treatments grew in rinsates containing chlorhexidine gluconate and in the distilled water rinsates. Washing with antimicrobial soap was more effective for reducing bacteria on soiled hands than was washing with water or nonantimicrobial soap. However, persistence or growth of bacteria in these rinsates poses health risks.

Antibiogram of bacteria isolated from automated teller machines in Hamadan, West Iran

Aim: Bacteria are ubiquitous in the environment. In keeping with the continued expansion of urbanization and the growing population, an increasing number of people use automated banking, i.e. automated teller machines (ATMs). The aim of this study was to investigate the bacterial contamination and its antibiotic sensitivity on computer keyboards located at ATMs in Hamadan province, Iran.

Method: Out of 360 ATMs at four locations in Hamadan, 96 were randomly selected for this study. The antibiotic susceptibility pattern of all isolates was determined by the agar disk diffusion method using gentamicin (10 µg), vancomycin (30 µg), trimethoprim/sulfamethoxazole (25 µg), amikacin (30 µg), tobramycin (10 µg), cephalotin (30 µg), norfloxacin (5 µg), and ceftizoxim (30 µg) disks.

Results: Melli and Saderat Banks had the most frequently contaminated ATMS, with 18 (27.7%) and 12 (18.5%), respectively. The most frequently isolated bacteria were Staphylococcus epidermidis in 12 (18.5%) ATMs, Pseudomonas aeruginosa in 12 (18.5%), Bacillus subtilis in 11 (16.9%), Escherichia coli in 6 (9.2%), Klebsiella spp. in 8 (12.3%), Enterobacter spp. in 2 (3.1%), Bacillus cereus in 6 (9.2%), Staphylococcus aureus in 3 (4.6%), and Micrococcaceae spp. in 5 (7.69%) cases. All isolated bacteria were susceptible to gentamicin, cephalotin, tobramycin, amikacin, norfloxacin, and vancomycin. The S. aureus resistance rate to trimethoprim/sulfamethoxazole was 50%.

Conclusion: All tested ATM keyboards were contaminated with at least one species of bacteria. Based on these findings, it is recommendable to disinfect the hands after entering one’s own apartment, work area or a hospital, in order to hinder the spread of critical pathogens in the personal environment or in the hospital.

Outbreaks where food workers have been implicated in the spread of foodborne disease. Part 6. Transmission and survival of pathogens in the food processing and preparation environment

This article, the sixth in a series reviewing the role of food workers in foodborne outbreaks, describes the source and means of pathogen transfer. The transmission and survival of enteric pathogens in the food processing and preparation environment through human and raw food sources is reviewed, with the main objective of providing information critical to the reduction of illness due to foodborne outbreaks. Pathogens in the food preparation area can originate from infected food workers, raw foods, or other environmental sources. These pathogens can then spread within food preparation or processing facilities through sometimes complex pathways and may infect one or more workers or the consumer of foods processed or prepared by these infected workers. The most frequent means of worker contamination is the fecal-oral route, and study results have indicated that toilet paper may not stop transmission of pathogens to hands. However, contact with raw foods of animal origin, worker aerosols (from sneezes), vomitus, and exposed hand lesions also have been associated with outbreaks. Transfer of pathogens has been documented through contaminated fabrics and carpets, rings, currency, skin surfaces, dust, and aerosols and though person-to-person transmission. Results of experiments on pathogen survival have indicated that transmission depends on the species, the inoculum delivery route, the contact surface type, the duration and temperature of exposure, and the relative humidity. Generally, viruses and encysted parasites are more resistant than enteric bacteria to adverse environmental conditions, but all pathogens can survive long enough for transfer from a contaminated worker to food, food contact surfaces, or fellow workers.

Survival on uncommon fomites of feline calicivirus, a surrogate of noroviruses

BACKGROUND

Norovirus (NoV) transmission occurs mainly through food and fomites. Contaminated human fingers can transfer the virus to inanimate objects, which may then spread the virus to susceptible persons. However, no information is available on the survival of NoVs on fomites, which may be of importance in the transmission of NoVs in institutional settings such as hospitals and nursing homes.

METHODS

In the absence of any in vitro cultivation system for NoVs, feline calicivirus (FCV) was used as a surrogate. Several fomites such as computer mouse, keyboard keys, telephone wire, telephone receiver, telephone buttons, and brass disks representing faucets and door handle surfaces were artificially contaminated with known amounts of FCV. Samples were taken at regular time intervals, and virus was titrated in feline kidney cells to determine its survival on these surfaces.

RESULTS

Survivability of FCV varied with fomite type. The virus survived for up to 3 days on telephone buttons and receivers, for 1 or 2 days on computer mouse, and for 8 to 12 hours on keyboard keys and brass. The time for 90% virus reduction was <4 hours on computer keys, mouse, brass, and telephone wire; 4 to 8 hours on telephone receiver; and 12 to 24 hours on telephone buttons.

CONCLUSION

The results of this study confirm that FCV (and perhaps NoV) can survive on fomites such as computers, telephones, and faucets and may be transmitted to humans using these contaminated materials. This may necessitate regular cleaning or disinfection of these items, especially in hospitals and nursing homes and after known outbreaks of NoVs.

Use of the 'ex vivo' test to study long-term bacterial survival on human skin and their sensitivity to antisepsis

AIMS

To determine bacterial survival on human skin and their sensitivity to antisepsis.

METHODS AND RESULTS

An 'ex vivo' protocol which uses human skin samples placed into diffusion cells, and electron microscopy (EM), were used to study the growth of Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa inoculated onto skin samples over a 46-h incubation period at 32 degrees C. Concurrently variation in skin pH was evaluated at different time intervals during this period. In addition the antimicrobial activity of three antiseptics against the incubated micro-organisms was assessed quantitatively with the 'ex vivo' test, while their detrimental effects against bacteria were observed by EM. All three bacteria were still present in high number after 46 h inoculation on skin, although the concentration of E. coli and S. aureus were reduced by 2.74 and 1.58 log(10) reduction, respectively, over this period of time. Electron micrographs showed clear evidence of cell division and some bacteria appeared to be embedded into the skin layers. The antiseptics tested had some antibacterial activity against bacteria incubated on skin for 3 and 10 h, and EM evidence showed some morphological damages including cellular blebbing and the presence of fibrillar material around the cells. All micro-organisms had an acidifying effect on skin samples.

CONCLUSIONS

Here, it was shown that bacterial pathogens can survive and grow when incubated on human skin. In addition, it is possible that they can penetrate the stratum corneum, which can provide some protection against antisepsis.

SIGNIFICANCE AND IMPACT OF THE STUDY

The apparent low bactericidal activity of biocides attributed in part to bacterial protection from skin layers is particularly important to assess in order to ensure antisepsis efficacy.

Distribution of bacteria on hands and the effectiveness of brief and thorough decontamination procedures using non-medicated soap

Our perception of the role of hand washing in the clinical situation is based on experimental studies in which test-bacteria are usually inoculated onto the skin surface and removed using hand washing preparations containing antiseptics. In this study, we have investigated the distribution of bacteria on the hands of volunteers and the effectiveness of long (3 minute) and brief (10 second) washes in removing both naturally-occurring and artificially-inoculated bacteria (Micrococcus sp.), using only soap and water. There was a tenfold reduction in median counts of artificially inoculated bacteria following both long and brief washes. However, less than 50% of naturally-occurring bacteria were removed and, for hands previously disinfected by immersion in 70% ethanol, the washing procedure increased bacterial counts. In both unwashed hands, and hands washed following a strict protocol, the mean variation in counts of naturally-occurring bacteria at different sites (wrists, dorsal surface, palmar surface, fingertips and interdigital spaces) was only two-fold. The efficiency of recovery of naturally-occurring organisms was estimated by repeated swabbing, to be more than 60%. The data question the value of typical hand wash procedures recommended by many authorities for use in clinical situations and of the perfunctory hand washes frequently adopted by nursing staff in busy wards. Experimental evidence is required to justify procedures and to identify the precise circumstances in which they are of value.

Gram-negative bacteria. The challenge of preventing cross-infection in hospital wards: a review of the literature

Gram-negative bacteria are responsible for a high proportion of nosocomial infections, particularly among the critically ill and those in hospital for long periods. Colonization (asymptomatic carriage on the skin) occurs before the emergence of overt clinical infection (appearance of the signs and symptoms of disease) and is therefore worth reducing. Spread is principally via the hands of staff, so handwashing is the chief method of prevention. Gram-negative bacteria survive best in a moist environment and are more readily transferred via damp than dry surfaces; hands and equipment should therefore be kept as dry as possible. Good skin can also help prevent cross-infection as Gram-negative bacteria colonize damaged skin more readily than if it is in good condition.

Outbreaks of infection with methicillin-resistant Staphylococcus aureus on neonatal and burns units of a new hospital

Multiple introductions of methicillin-resistant Staphylococcus aureus (MRSA) strains occurred to a new hospital in Hong Kong. Two years of clinical microbiological surveillance of the resulting outbreaks was combined with laboratory investigation by phage and antibiogram typing, and plasmid profiling. The outbreaks on the special care baby (SCBU) and burns (BU) units were studied in detail, and colonization of staff and contamination of the environment were investigated. MRSA were spread by the hands of staff on the SCBU, where long-term colonization of dermatitis was important, but were probably transmitted on the BU by a combination of the airborne, transient hand-borne and environmental routes. Simple control measures to restrict hand-borne spread on the SCBU were highly effective, but control was not successful on the BU.

New method for determination of efficacy of health care personnel hand wash products

A method of studying the effects of health care personnel hand wash products is described. The fingernail regions of the hands of volunteers are inoculated with a mixture of Escherichia coli and Serratia marcescens, and the areas are dried for a standard time. After routine hand washing, each fingernail region is individually scrubbed with an electric toothbrush which moves longitudinally to the handle into collection fluid contained in a petri dish. The test bacteria in the fluid are then enumerated. (Bacillus subtilis spores may be included as tracers to show degree of physical removal of the procedure.) This method has several advantages over the frequently used glove juice technique. Experimental designs with large numbers of volunteers, multiple sampling sites, and many hand wash products may be performed. Ten sampling sites (fingers) are available, versus the two gloved hands for testing products. (Efficiency is almost 100% in the recovery of spore tracers placed on the fingernails.) Many commercial health care personnel hand wash products containing antimicrobial agents substantive to the skin do not rapidly reduce numbers of inoculated bacteria in the fingernail regions to any greater extent than nonantimicrobial hand washes. Products containing isopropanol or ethanol are very effective in decreasing bacteria in areas around and under the fingernails.

Microbiologic flora of human fingernails

The incidence of and nature of fingernail flora was studied in 20 patients. These patients underwent routine preoperative hand scrubbing in a clinical setting, without nail trimming or cleaning. Nineteen (95%) of 20 had a moderate to heavy growth of Staphylococcus epidermidis. These isolates were very susceptible to antibiotics. Thirteen (65%) of 20 patients had fungi (molds and yeast). In spite of adequate preoperative hand scrubbing, the fingernails were heavily contaminated. Such organisms may become pathogens and should not always be considered contaminants. This study also confirmed the importance of preoperative fingernail trimming and cleaning.

Increasing handwashing compliance with more accessible sinks

The frequency of handwashing in two intensive care units (ICUs) was observed. Handwashing after direct contact with patients or their support equipment was recorded. The ratio of beds to sinks was 1:1 in the medical ICU and 4:1 in the surgical ICU. Surveillance of physicians, nurses, and other personnel demonstrated a greater frequency of handwashing by nurses (63%) compared with physicians (19%) and other personnel (25%). The nurses in the unit with one sink per bed had a significantly greater number of handwashes (76%) than those in the unit with fewer sinks (51%).

In vitro contamination of "piggyback/heparin lock" assemblies: prevention of contamination with a closed, positive locking device (Click-Lock)

Direct contact and airborne transmission are established modes of microbial contamination of standard intravenous (iv) assemblies such as piggyback and heparin lock. In this study, 60% of the standard iv assemblies inoculated with Staphylococcus aureus (S. aureus) at the barrel of their exposed needle grew these organisms when cultured in a Soy Casein Digest Broth (SCDB). Also, 40 closed, positive locking iv assemblies (Click-Lock) were inoculated at possible contamination sites, and none of these assemblies grew S. aureus in a SCDB. These in vitro studies suggest that a closed, positive locking iv assembly such as the Click-Lock device may substantially reduce, and potentially prevent contamination of iv systems.