Difference In Contamination Rates Research Articles

Urine Clean Catch Collection in the Paediatric Emergency Department: Success, Time to Void and Contamination Rates

Abstract BACKGROUND: Young children frequently require investigation for urinary tract infection (UTI). Clean catch urine (CCU) is a common urine collection method in pre-continent children but can be time consuming or unsuccessful, and contaminated cultures may lead to an inability to diagnose or exclude UTI. There are few data available examining the success and time required for CCU and factors influencing contamination. We hypothesise that time taken to obtain CCU influences contamination, due to accidental contamination during collection. OBJECTIVES: To determine the time taken to obtain CCU in pre-conti-nent children, and if time to collection is related to the contamination rate. DESIGN/METHODS: Prospective observational study of CCU collection in pre-continent children aged 2-48 months at a paediatric emergency department in Australia. A standardised CCU collection protocol was used. Primary outcome was time to first void; secondary outcomes were success of obtaining (catching) CCU and contamination of urine cultures obtained. Contamination was defined as per hospital microbiology standards. Descriptive analysis of time to void included median and interquartile range (IQR). We performed a regression analysis of key factors possibly related to contamination, including age, sex and time to collection. RESULTS: Of the 218 recruited patients, 61% were male, mean age 11.4 months (SD 8.5). The main indication for CCU was: 128 fever of unknown origin (59%), 31 vomiting (14%), 27 specifically suspected UTI (12%), 32 other reason (15%). From first CCU attempt, 174 voided (80%) of which 139 were successful catches (64%) and 34 were missed on voiding (16%). 44 first CCU attempts were stopped before voiding (20%), 26 patients had 2 attempts (12%), and 2 patients had 3 CCU attempts (1%). Median time to first void was 25 minutes (IQR 8 – 49). 27 children (12%) voided <5 minutes, 33 (19%) voided >1hr. Of the 130 patients who had urine culture results available, 50 were contaminated (38%). There was no significant difference in contamination rate by age, sex or time to sample collection. Of 218 patients where ED clinicians set out to collect CCU in the emergency department, only 80 (37%) resulted in a successful CCU attempt with an uncontaminated culture. CONCLUSION: Contamination rates are high in clean catch urine, but not related to the time taken for sample collection. CCU attempts are often unsuccessful, and have a low diagnostic yield for investigation of UTI in young children in clinical practice.

Neonatal resuscitation equipment: A hidden risk for our babies?

Neonatal infections carry a heavy burden of morbidity and mortality. Poor practice can result in unintentional colonisation of medical equipment with potentially pathogenic organisms. This study will determine the prevalence and type of bacterial contamination on exposed neonatal resuscitation equipment in different clinical settings and explore simple measures to reduce contamination risk. A survey determined the rates of resuscitation equipment usage. All environmentally exposed items were identified on resuscitaires hospital-wide and swabbed for bacterial contamination. A new cleaning and storage policy was implemented and the prevalence of environmentally exposed equipment re-measured post-intervention. Resuscitation equipment was used in 28% of neonatal deliveries. Bacterial colony forming units were present on 44% of the 236 exposed equipment pieces swabbed. There was no significant difference in contamination rates between equipment types. Coagulase negative staphylococcus was the most prevalent species (59 pieces, 25%) followed by Escherichia coli and Enterobacter cloacae (20 pieces, 9% each). Opened items stored inside plastic remained sterile, whilst those in low-use areas had significantly less contamination than those in high-use areas (22% vs. 51%, P < 0.05). Implementing a simple educational programme led to a significant reduction in environmentally exposed equipment (79% reduction, P < 0.01). Pathogenic bacteria can colonise commonly used pieces of neonatal resuscitation equipment. Whilst the clinical significance remains uncertain, equipment should be kept packaged until required and discarded once open, even if unused. Standardising cleaning policies results in rapid and significant improvements in equipment storage conditions, reducing microbial colonisation opportunities.

Comparison of keypads and touch-screen mobile phones/devices as potential risk for microbial contamination.

Touch-screen mobile phones/devices (TMPs/Ds) are increasingly used in hospitals. They may act as a mobile reservoir for microbial pathogens. The rates of microbial contamination of TMPs/Ds and keypad mobile phones (KMPs) with respect to different variables including use by healthcare workers (HCWs)/non-HCWs and the demographic characteristics of users were investigated. A total of 205 mobile phones/devices were screened for microbial contamination: 76 devices belonged to HCWs and 129 devices belonged to the non-HCW group. By rubbing swabs to front screen, back, keypad, and metallic surfaces of devices, 444 samples were collected. Of 205 mobile phones/devices, 143 (97.9%) of the TMPs/Ds and 58 (98.3%) of the KMPs were positive for microbial contamination, and there were no significant differences in contamination rates between these groups, although TMPs/Ds had significantly higher microbial load than KMPs (p <0.05). The significant difference in this analysis was attributable to the screen size of mobile phones ≥ 5". Microbial contamination rates increased significantly as phone size increased (p <0.05). Higher numbers of coagulase-negative Staphylococci (CNS) were isolated from KMPs than TMPs/Ds (p = 0.049). The incidence of Enterococcus spp. was higher on the KMPs of HCWs, and methicillin resistant CNS was higher from the TMPs/Ds of non-HCWs (p <0.05). Isolation of CNS, Streptococcus spp. and Escherichia coli was higher from the TMPs/Ds of HCWs (p <0.05). We found no significant difference between TMP/Ds and KMPs in terms of microbial contamination, but TMP/Ds harboured more colonies and total microbial counts increased with screen size.

Effectiveness of Preanalytic Practices on Contamination and Diagnostic Accuracy of Urine Cultures: a Laboratory Medicine Best Practices Systematic Review and Meta-analysis.

SUMMARYBackground.Urinary tract infection (UTI) in the United States is the most common bacterial infection, and urine cultures often make up the largest portion of workload for a hospital-based microbiology laboratory. Appropriately managing the factors affecting the preanalytic phase of urine culture contributes significantly to the generation of meaningful culture results that ultimately affect patient diagnosis and management. Urine culture contamination can be reduced with proper techniques for urine collection, preservation, storage, and transport, the major factors affecting the preanalytic phase of urine culture.Objectives.The purposes of this review were to identify and evaluate preanalytic practices associated with urine specimens and to assess their impact on the accuracy of urine culture microbiology. Specific practices included collection methods for men, women, and children; preservation of urine samples in boric acid solutions; and the effect of refrigeration on stored urine. Practice efficacy and effectiveness were measured by two parameters: reduction of urine culture contamination and increased accuracy of patient diagnosis. The CDC Laboratory Medicine Best Practices (LMBP) initiative's systematic review method for assessment of quality improvement (QI) practices was employed. Results were then translated into evidence-based practice guidelines.Search strategy.A search of three electronic bibliographic databases (PubMed, SCOPUS, and CINAHL), as well as hand searching of bibliographies from relevant information sources, for English-language articles published between 1965 and 2014 was conducted.Selection criteria.The search contained the following medical subject headings and key text words: urinary tract infections, UTI, urine/analysis, urine/microbiology, urinalysis, specimen handling, preservation, biological, preservation, boric acid, boric acid/borate, refrigeration, storage, time factors, transportation, transport time, time delay, time factor, timing, urine specimen collection, catheters, indwelling, urinary reservoirs, continent, urinary catheterization, intermittent urethral catheterization, clean voided, midstream, Foley, suprapubic, bacteriological techniques, and microbiological techniques.Main results.Both boric acid and refrigeration adequately preserved urine specimens prior to their processing for up to 24 h. Urine held at room temperature for more than 4 h showed overgrowth of both clinically significant and contaminating microorganisms. The overall strength of this body of evidence, however, was rated as low. For urine specimens collected from women, there was no difference in rates of contamination for midstream urine specimens collected with or without cleansing. The overall strength of this evidence was rated as high. The levels of diagnostic accuracy of midstream urine collection with or without cleansing were similar, although the overall strength of this evidence was rated as low. For urine specimens collected from men, there was a reduction in contamination in favor of midstream clean-catch over first-void specimen collection. The strength of this evidence was rated as high. Only one study compared midstream collection with cleansing to midstream collection without cleansing. Results showed no difference in contamination between the two methods of collection. However, imprecision was due largely to the small event size. The diagnostic accuracy of midstream urine collection from men compared to straight catheterization or suprapubic aspiration was high. However, the overall strength of this body of evidence was rated as low. For urine specimens collected from children and infants, the evidence comparing contamination rates for midstream urine collection with cleansing, midstream collection without cleansing, sterile urine bag collection, and diaper collection pointed to larger reductions in the odds of contamination in favor of midstream collection with cleansing over the other methods of collection. This body of evidence was rated as high. The accuracy of diagnosis of urinary tract infection from midstream clean-catch urine specimens, sterile urine bag specimens, or diaper specimens compared to straight catheterization or suprapubic aspiration was varied.Authors' conclusions.No recommendation for or against is made for delayed processing of urine stored at room temperature, refrigerated, or preserved in boric acid. This does not preclude the use of refrigeration or chemical preservatives in clinical practice. It does indicate, however, that more systematic studies evaluating the utility of these measures are needed. If noninvasive collection is being considered for women, midstream collection with cleansing is recommended, but no recommendation for or against is made for midstream collection without cleansing. If noninvasive collection is being considered for men, midstream collection with cleansing is recommended and collection of first-void urine is not recommended. No recommendation for or against is made for collection of midstream urine without cleansing. If noninvasive collection is being considered for children, midstream collection with cleansing is recommended and collection in sterile urine bags, from diapers, or midstream without cleansing is not recommended. Whether midstream collection with cleansing can be routinely used in place of catheterization or suprapubic aspiration is unclear. The data suggest that midstream collection with cleansing is accurate for the diagnosis of urinary tract infections in infants and children and has higher average accuracy than sterile urine bag collection (data for diaper collection were lacking); however, the overall strength of evidence was low, as multivariate modeling could not be performed, and thus no recommendation for or against can be made.

Fungal contamination of nebuliser devices used by people with cystic fibrosis

BackgroundPoor nebuliser hygiene can result in bacterial contamination and risk of infections. The aim of this study was to assess the prevalence of fungal contamination of nebulisers used by adults with cystic fibrosis. MethodsA total of 170 nebulisers from 149 subjects were screened by wetting a sterile cotton swab with sterile water and swabbing each drug chamber. The swab was then plated out on Sabouraud and on Scel+agar and incubated at 27°C for up to 2weeks. ResultsFungal cultures were positive in 86 (57.7%) patient's devices. In 28/149 (18.8%), 39/149 (26.2%), 47/149 (31.5%) and 20/149 (13.4%) of subjects Aspergillus species, yeasts, moulds and both yeasts and moulds were isolated respectively. There was no difference in contamination rates between different devices. ConclusionNebuliser devices are frequently contaminated by moulds and yeasts and emphasis should be placed on ensuring adequate nebuliser hygiene.

113 Sphygmomanometer Cuffs: A Potential Source of Infection!

BackgroundSphygmomanometers which are used to assess a patient’s haemodynamic status in the healthcare setting come into direct contact with patients’ skin. However, there has been no study conducted in the...

Amount of Usage and Involvement in Explosions Not Associated with Increased Contamination of Prehospital Vehicles with Multi-drug-resistant Organisms

The role of explosions and patient transport vehicles as sources and vectors of Gram-negative, multidrug-resistant organisms (MDROs) that predominate infections following lengthy evacuations after disasters due to natural hazards and in current war-trauma patients is unknown. Damaged or heavily-used vehicles could be sources of the MDROs subsequently linked to nosocomial infections. From January through May 2008 in Iraq, inside surfaces of heavily-used, tactical vehicles (Experimental Group) were sampled with sterile, pre-moistened swabs. Swabs, along with positive and negative controls, were shipped to the reference laboratory in Washington, DC, where they underwent culture, identification and susceptibility testing, and pulsed-field gel electrophoresis. Multidrug-resistant organisms were defined according to the standard Centers for Disease Control and Prevention definitions. High risk organisms (HROs) were defined as susceptible E. coli, A. baumannii, P. aeruginosa, Enterobacter spp, or Klebsiella spp. Concurrently, new counterparts (Control Group) were similarly surveyed in a storage lot in Georgia, USA. Groups were compared using the Chi-squared test. One hundred thirty-nine consecutive vehicles including all available ambulances were sampled, yielding 153 swabs. Nineteen were lost or damaged during shipping. Seventy-nine swabs yielded growth of one or more Gram-negative bacteria. The amount and genotype of MDROs in heavily-used vehicles, including those involved in roadside bombings, were compared to control vehicles and to strains isolated from wounds and environmental surfaces at the base hospital. Predominant organisms included P. agglomerans (34%), S. flexneri (8%), E. vulneris (6%), Pseudomonas sp. (6%), and K. pneumonia (6%). No MDROs were isolated. Thirteen vehicles (eight of 94 experimental and five of 45 control) yielded HRO. There was no difference in contamination rates (P = .63). No HROs were isolated from ambulances. No clonal association existed between vehicle and hospital strains. Given the implications that this knowledge gap has on military and civilian prehospital reservoirs of infection, further study is warranted to confirm these findings and identify targets for preventive intervention throughout civilian disaster and military casualty evacuation chains.

The effect of surgical preparation technique on the bacterial load of surgical needles and suture material used during strabismus surgery

To investigate the effectiveness of 3 surgical preparation techniques in decreasing bacterial contamination of needles and suture material during strabismus surgery. Consecutive patients requiring 2-muscle strabismus surgery were randomized into 1 of 3 groups. In Group A, patients' periocular skin and bulbar conjunctivae underwent preparation with 5% povidone-iodine; the drape was placed without regard to eyebrows; and an open wire-loop lid speculum was used. Group B patients underwent the same preparation as Group A patients; however, the eyelashes and eyebrows were scrubbed with 5% povidone-iodine on cotton tip applicators, and the drape was placed to exclude the eyebrows from the surgical field. Group C patients underwent the same preparation as Group B patients; however, a bladed lid speculum was used during surgery to exclude some of the eyelashes from the surgical field. After the procedure, all needles and suture materials were sent separately for aerobic culture. The data were analyzed for differences in contamination rates between the groups. Of 77 patients, 24 (31.4%) had either a needle and/or suture contaminant. Groups A, B, and C had mean contamination rates of 29.6%, 34.6%, and 29.2%, respectively. There was no significant statistical variation in contamination among the 3 groups. The most common organism identified was a coagulase-negative staphylococcus strain. More meticulous sterile preparation of the surgical field did not result in a meaningful reduction in suture or needle contamination rates during strabismus surgery.

Contact Lens Case Contamination During Daily Wear of Silicone Hydrogels

Contamination of contact lens cases has been associated with the production of adverse responses in the eye during contact lens wear. This study aimed to evaluate the contamination rate and types of microbes contaminating cases during use of contact lens disinfecting solutions and silicone hydrogel lenses. Two hundred thirty-two participants were allocated to one or more groups. The participants wore one or more of three silicone hydrogel lenses and used one or more of four contact lens disinfecting solutions. Cases were collected after use for 1 month and sent for routine microbial testing. The rate of contamination of cases and the types of microbes contaminating cases were evaluated. Between 76 and 92% of all cases were contaminated. Use of different contact lenses did not affect contamination rate or the types of microbes isolated from cases. Use of AQuify (PHMB as disinfectant) was associated with the highest contamination rate (92%; p = 0.015) of cases for any microbe. Level and type of contamination with use of ClearCare (H2O2) was similar to use of PHMB (polyhexamethylene biguanide)- or Polyquat/Aldox-containing solutions. There was no difference in contamination rate of cases by fungi or Gram-positive bacteria, but for Gram-negative bacteria, use of Opti-Free Express (Polyquat and Aldox as disinfectants) resulted in a lower contamination rate (7% vs. 29 to 45%; p < 0.001). The average number of microbes contaminating a case was significantly less for Opti-Free Express (223 +/- 1357 cfu/case) compared with Opti-Free RepleniSH (Polyquat and Aldox as disinfectants; 63,244 +/- 140,630 cfu/case; p < 0.001), driven mostly by differences in numbers of Gram-negative bacteria, particularly contamination by Delftia acidovorans in cases exposed to Opti-Free RepleniSH. Different disinfecting solutions used during storage in cases result in different levels of contamination and contamination by different types of microbes. These differences are not simply because of the types of disinfectants used, suggesting that other excipients in, or formulation of, the solution affect contact lens storage case contamination.

Catheter-drawn blood cultures: is withdrawing the heparin lock beneficial?

To assess the potential benefit of withdrawing or flushing away the heparin lock before collecting blood for culture from a central venous catheter. We compared the contamination rates of 152 pairs of blood samples aspirated from central venous catheters in afebrile renal dialysis or cancer patients. We also assessed the antimicrobial effect of 2000 U of heparin in Bactec Plus Aerobic/F culture bottles inoculated with a volunteer's blood plus one of six common bloodstream pathogens. There was no significant difference in contamination rates between first-drawn (26 of 152, 17.1%) and second-drawn (24 of 152, 15.8%) samples. There was no significance difference in yield (58 of 60 [97%] versus 52 of 53 [98%]) or time to flagging positive (16.6 versus 16.7 h) between the bottles with and without heparin. Our results do not support the practice of withdrawing or flushing away the heparin lock before collecting blood for culture from a central venous catheter.

Contamination of breast milk obtained by manual expression and breast pumps in mothers of very low birthweight infants

The objective of this study was to compare the rates of bacterial contamination of expressed breast milk (EBM) obtained by manual expression and breast pumps in mothers of very low birthweight (VLBW) infants (<1501g). This was a randomized, controlled study carried out on 28 mothers of such babies and 92 specimens of EBM were collected: 41 specimens from 13 mothers assigned to the manual group and 51 specimens from 15 mothers in the breast-pump group. EBM was cultured quantitatively by the Miles and Misra method. Breast milk expressed by breast pumps (86.3% or 44/51 specimens) had a significantly higher rate of bacterial contamination than milk expressed by the manual method (61.0% or 25/41 specimens) (P= 0.005). When breast milk was expressed in the hospital, there was no significant difference in contamination rates between the two methods. When breast milk was expressed at home, the rates of bacterial contamination by staphylococci (P= 0.003) and Gram-negative bacilli (P= 0.002) were significantly higher in the breast-pump group than the manual group. In conclusion, the rate of bacterial contamination of EBM of mothers of VLBW infants was high, especially when EBM was obtained by the breast pump or when expression was carried out at home.

Outpatient Urine Culture

Dysuria is one of the most common presenting complaints of young women, and urinalysis is one of the most common laboratory tests performed. Despite the fact that the midstream clean-catch technique is commonly used for urine collection, contaminated urine cultures occur with distressing regularity. The midstream clean-catch technique is time-consuming to explain, frequently not performed correctly by patients, costly for supplies, often embarrassing for patients and staff, and of unproven benefit. Therefore, we designed a study to compare various methods of obtaining specimens for culture from acutely dysuric young women. A total of 242 consecutive female patients who presented with symptoms suggestive of a urinary tract infection were randomized into 3 groups. The first group (n = 77) was instructed to urinate into a clean container. No cleansing was done, and the specimen was not obtained midstream. The second group (n = 84) was instructed to collect a midstream urine sample with perineal cleansing and spreading of the labia. In an attempt to decrease contamination from the vagina, the third group (n = 81) was given the same instructions as group 2, with the addition of using a vaginal tampon. Contamination rates were calculated for all 3 groups. Contamination rates for the 3 groups were nearly identical (29%, 32%, and 31%, respectively). Comparing the no-cleansing group with the combined cleansing, midstream groups also showed no difference in contamination rates (28.6% and 31.5%, respectively, with P =.65). In young, outpatient women with symptoms suggestive of a urinary tract infection, the midstream clean-catch technique does not decrease contamination rates.

Effects of lipolytic enzymes Pseudomonas fluorescens on liberation of fatty acids from milk fat

Effects of thermostable lipolytic enzymes Pseudomonas fluorescens 66 ZB in pasteurized milk on concentration of free fatty acids (VMK) in milk were studied in selected milk samples. Identical bulk milk samples were analysed by the method specified in previous papers (Vyletělová et al. 1999a, b, 2000). Reference milk samples (without bacterial strains) and the experimental ones (containing Ps. fl. 150 th. CFU/ml and 2800 th. CFU/ml, resp.) were stored at 6.5°C and 14°C and analysed at regular time intervals (24 h) – Table 1. An extractive-titric method (Kadlec et al. 1996; Table 2 and Fig. 2) was used for monitoring of fatty acid (MK) liberation. Precise analyses of MK and VMK were made by the chromatographic method (Figs. 1, 3 and 4). Medium-chain fatty acids (C12–C16) are liberated first of all; short-chain acids (C6–C10) were found sporadically or in very small quantities (Table 2). Dissociation constant of the specific fatty acid liberated from milk fat affects principally relationships between pH and free fatty acid concentration. The predominating proportion of long-chain acids in liberated fatty acid formation is associated with lower reduction of pH as compared to the predomination of fatty acids with shorter chains associated with more substantial reduction of pH. In our study, a rapid decrease of pH was noted before 168 h (Table 24); this corresponds to low concentrations of short-chain free fatty acids. Vyletělová et al. (2000) found significant relations between pH and contents of VMK (measured by the extractive-titric method); in some samples, correlation coefficients amounted to r = –0.93*** (P £ 0.001). The extractive-titric method analysing VMK concentrations (mmol/kg milk fat) provides results characterized by a systematic rise (e.g., 32.0 mmol/kg instead of 13.0 mmol/kg in raw milk). According to Kratochvíl (1992) 20 mmol VMK/kg milk fat signalized the starting point characterizing flavour degradation of milk caused by activities of fatty acids C12–C14 above all; the transformed value (respecting specifics of the extractive-titric method) amounts to 49 mmol/kg. In case of higher storage temperature a significant break is found after 144 h; in case of lower temperature this break is after 192 h (Table 2). Limits determining potential lipolytic modifications of milk flavour (RLZCHV) as related to specific samples and temperatures at VMK levels amounting to 49 mmol/kg or 20 mmol/kg are outlined in Fig. 2. Milk samples No. 5 and No. 6 stored at higher temperature surpassed this risk limit at 56 h and 64 h, respectively (Table 2, Fig. 2). On the contrary, milk samples stored temperatures corresponding to the standard storage temperature (storage of raw milk, transport, storage of pasteurized milk) surpass the mentioned risk level after 90 h and 140.5 h. Obtained results document the predominant role of storage temperature in the whole complex (production and processing of milk as a raw material or an intermediate product); evident differences in contamination rates (105 an 106) can be characterized as secondary effects in this case (Table 2). As related to practical conditions, the mentioned facts imply immediate processing of raw milk and pasteurized milk. This postulate must be respected namely by dairy plants producing delicate milk products. Vyletělová et al. (2000) found a notable VMK increase/24 h (7–11 mmol/kg milk fat) under specific temperatures and microbial contamination.

Contamination susceptibility of three needleless and one standard needle injection systems.

To compare in vitro the contamination susceptibility of three needleless and one standard needle injection systems. The Baxter InterLink, St. Paul Medical Key-Lok, Braun SafSite, and Becton Dickinson heparin lock, were compared. Fifty of each were studied. Each system was connected to a culture bottle and injected 30 times over 72 hr. The manufacturers' directions were followed except for Braun's, which recommend that a new sterile cap be used after each injection. Instead, the same cap was used after each injection to reflect day-to-day clinical practice. Culture bottles were subsequently analyzed for bacterial growth. The contamination rates for the heparin lock, InterLink, Key-Lok, and SafSite were 3/50 (6%), 6/50 (12%), 4/50 (8%), and 36/50 (72%), respectively. All positive cultures grew coagulase-negative staphylococcus species. There was no difference in contamination rates between the InterLink, Key-Lok, and heparin lock designs. The contamination rate of the SafSite was higher (P < 0.001) than the other three systems. The InterLink and Key-Lok systems had a similarly low contamination susceptibility as a standard needle injection system. It was not clear if the high contamination rate found with the SafSite system was due to non-adherence to the manufacturer's directions for handling.

Titrated intravenous opioids from the same syringe: an infection risk?

OBJECTIVE: (1) To compare the rate of contamination of syringes prepared under laminar flow conditions in pharmacy with those prepared by nurses in the emergency department; (2) to determine whether...

Evaluation of Vitrectomy Machines as a Source of False-Positive Culture Contamination in Endophthalmitis

We sought to determine whether a venturi-aspiration vitrectomy machine could contaminate a vitrectomy culture. Ninety vitrectomies were simulated in a hospital operating room and were cultured with standard techniques. An additional 90 control specimens were cultured in the exact same manner, but the vitrectomy machine was not used. Instead, the control specimens were placed directly into a sterile vitrectomy cassette. Contamination rates in the two groups were compared. Contamination occurred in four of 90 vitrectomy-simulation cultures and in three of 90 control cultures. This difference in contamination rate was not statistically significant. Although the result of a culture of the vitrectomy effluent can be false-positive, the source of contamination is not likely to be the vitrectomy machine.

Effect of needle changing and intravenous cannula collection on blood culture contamination rates

We tested the hypotheses that blood culture positivity and contamination rates were not increased by not changing needles between venipuncture and inoculation of blood culture bottles or by taking blood for culture by freshly inserted IV cannulae. A prospective study of blood cultures collected by venipuncture or IV cannulae taken from an emergency department population. Venipuncture samples were randomized into needle change (standard method) or no needle change before inoculation into blood culture bottles. Nine hundred forty patients requiring blood cultures after assessment in the ED. A standard disinfection procedure using 0.5% chlorhexidine in 70% alcohol was used. Blood was collected by venipuncture and inoculated with or without needle change. Blood collected by IV cannula was inoculated with a fresh needle applied to the collection syringe. There was no statistically significant difference in contamination rates for blood collected by venipuncture with no needle change (6.4%) compared with needle change (4.2%, P > .30). No significant difference in contamination rates was noted for blood taken by freshly inserted IV cannulae (4.3%) compared with venipuncture with needle change after sampling (4.2%, P > .90). Some problems with randomization resulted in unequal numbers in the needle-change (286) versus no-needle-change (141) subgroups, and this may have introduced bias. A higher rate of pathogen growth was observed in blood taken by IV cannula (11.4%) compared with the standard method (6.3%) (P < .025). A significantly greater rate of Gram-negative sepsis was noted in the IV cannula group (6.6%) compared with direct venipuncture with needle change (1.1%) and no needle change (4.2%, P < .01). The results of this study do not support the practice of changing needles before inoculating blood samples into blood culture bottles. Collection of blood for culture through freshly inserted IV cannulae is associated with a low contamination rate and is an acceptable alternative to direct venipuncture. Sources of bias in this study suggest that further research is needed to determine the optimal technique for collecting blood cultures.

A Prospective Randomized Trial Comparing Manual and Automated Endoscope Disinfection Methods

To compare the efficacy of endoscope disinfection using automated and manual systems. Prospective randomized trial. A 1,000-bed tertiary care referral center. All endoscopes underwent a three-stage decontamination process including brushing and cleaning with water and detergent, manual or automated disinfection with 2% glutaraldehyde, and 70% alcohol rinse with forced air drying. Cultures were obtained from endoscopes from both groups before and after alcohol rinse and then after overnight storage. Cultures from 8/30 (27%) automated and 11/30 (37%) manually disinfected (P = 0.58) endoscopes grew gram-negative bacteria and/or nontuberculous mycobacteria before the alcohol rinse. After alcohol rinse, 3 (10%) of 30 automated and 8 (27%) of 30 manually disinfected endoscopes remained contaminated (P = 0.28). Manually disinfected endoscopes were contaminated more frequently with coliform bacteria, whereas endoscopes undergoing automated disinfection were more frequently contaminated with nontuberculous mycobacteria, but the differences were not statistically significant. After alcohol rinse and forced air drying, there was no difference in contamination rates between freshly disinfected endoscopes and those stored overnight (7/30 (23%) versus 4/30 (13%), P = 0.50). Colonoscopes and duodenoscopes were contaminated more often than gastroscopes (P = 0.00001). The persistent endoscope contamination after manual and automated disinfection indicates the importance of developing more reliable and effective disinfection methods.

Evaluation of the shelf life of sterile instrument packs

No published studies have specifically addressed the shelf life of sterile packaging materials commonly used in dentistry. This study examined the effect of time on the sterile integrity: paper envelopes, peel pouches, and nylon sleeves. Seven thousand two hundred sample packs, each containing three glass rods, were prepared and steam sterilized. After sterilization, half the packs (control packs) were immediately opened and the contents were analyzed for bacterial contamination. The other half (test packs) were randomly sorted and stored in dental treatment operatories. At monthly intervals for 12 months, 100 packs of each type were similarly opened and analyzed. The contamination rates between the control packs were not significantly different from one another. Differences in contamination rates between control packs and test packs for both the paper envelopes (0.4% and 0.7%) and the peel pouches (0.2% and 0.2%) were also insignificant. However, a significant difference ( p < 0.01) between control and test packs (0.3% and 1.5%) was found for the nylon sleeves. This increase was not time related and was attributed to difficulty in removing the glass rods from the nylon packs in a sterile manner. The most important finding was the absence of a trend toward an increased rate of contamination over time for any pack type. This indicates that when these materials are placed in covered storage in dental operatories, a 12-month storage period is not detrimental to their sterile integrity.

Bacterial contamination rate of soft contact lens cases

The bacterial contamination rate of contact lens cases in different care systems was investigated and a comparison was made between the case caps and the case wells. Contact lens cases were collected from 39 hydrogen peroxide care system users and 14 non-hydrogen peroxide care system users at the Southern California College of Optometry during routine follow-up care. The total contamination rate of all the case samples was found to be 19% (10/53). Fifteen percent of the cap samples (8/53) and 19% of the well samples (10/53) were found to be contaminated. Of the samples that were contaminated, 80% (8/10) were found to be contaminated in both the cap and the well and 80% were found to be positive for the Pseudomonas aeruginosa strain of bacteria. There was no difference in contamination rate between hydrogen peroxide and non-hydrogen peroxide disinfecting systems. These results indicate a lower incidence of lens case contamination than in previous investigations, but emphasize the need for regular cleaning or disinfecting of the entire contact lens case as part of routine care by contact lens patients.