Presentation on theme: "ABSTRACT ID: IRIA 1175 Ultrasound gel is a potential mode of infection transmission in postoperative patients. A prospective study."— Presentation transcript:
ABSTRACT ID: IRIA 1175 Ultrasound gel is a potential mode of infection transmission in postoperative patients. A prospective study.
AIM Ultrasound is one of the equipments that are known to transmit nosocomial infections. The study was conducted to identify the incidence of infection in post operative patients following ultrasound study and the significance of disinfection methods.
INTRODUCTION Ultrasonography(USG) is a commonly used imaging technique in modern medicine. It is a preferred imaging method, as it is non- invasive, non-ionizing as well as portable . A gel is used as a coupling media during ultrasound to displace the air and allow the ultrasound waves to enter the body. The gel is an inert material containing carbamer, Ethelene diamine tetra acetic acid, propylene glycol, trolamine and distilled water. Coupling gel and the probes have been traced to be a source of infection [2,3,4,5,6,7]. Hence, the specialty of Diagnostic Radiology is not an exception and is a source of nosocomial infection .
With the increase in the number of post operative and immunocompromised patients being scanned, effective guidelines for prevention of infection and disinfection are necessary . Literature shows limited studies regarding infection in post operative patients following ultrasound [6,7]. A number of organisms such as Staphylococcus aureus, Staphylococcus epidermidis and Enterococcus faecalis, Klebsiella, Stentrophomonas maltophilia and Acinetobacter baumannii have been isolated from the gel.
Hence, every precaution for prevent of infection transmission should be taken. This study highlights the organisms that might contaminate the gel and ultrasound equipments and the incidence of infection following ultrasound study in post operative patients. Despite the publishing of many articles regarding infection, the response from various international governments is lukewarm. International guidelines for disinfection of probes are available but not for disinfection of gel [5,9]. Certain governments such as the Canadian government issued guidelines to be followed at ultrasound units .
Materials & Methods This prospective study was conducted in our ultrasound department and included operated patients in the month of march 2014 over a period of 30 days. 65 patients were included in the study and the same number of controls were examined. Ethical committee and patient’s consent were obtained. The study included patients who have under gone abdominal and breast surgeries as these are the patients who might require an USG following surgery. Patients who underwent any neurosurgery as well as laparoscopic surgery were excluded as the requirement in neurosurgery is almost nil and in case of laparoscopic surgery, the surgical incision is very small and does not require direct contact of the transducer with the scar site. Patients with wound gapping were also included in the study.
The patients underwent sonogram on the third postoperative day. Two transducers (curvilinear and linear) were used for the sonography study. First culture swab was taken from the scar site before the ultrasound from each patient. After the ultrasound the wound was dressed with gauze without any antiseptics and the probe was cleaned with a gauze piece. A second culture swab was taken from the scar after 48hours following the first swab. So a total of two culture swabs were taken from each patients. Swabs were taken from the transducers and ultrasound gel at the beginning of the study, at the middle of the study and at the end of the study. Hence, a total of 139 swabs were taken(130 swabs from 65 patients and 9 swabs from the transducer and gel).
The collected samples were inoculated in 5% sheep blood agar (M1 YYA), Mac Conkey agar (Mo8Za) and Saborauds dextrose agar (M0167). Antimicrobial susceptibility testing, was carried out for the isolated organisms, on Mueller – Hinton agar (M173), by using the Kirby-Baver disc diffusion method. The samples were read at 24 and 48hrs after inoculation. Mac CONKEY AGAR SHEEP BLOOD AGAR Mueller-Hinton agar
RESULTS The initial swabs from the gel bottle and probes showed heavy contamination with Klebsella pneumoniae and Acinetobactor, both resistant to Amoxicillin / Clavulanic acid. High incidence of Escherichia coli infection was noted in first sample on the 3rd post operative day (16.9%)(Table 1)
Organism FrequencyPercent Cumulative Percent E.coli 1116.9 Ps. aeruginosa 23.120.0 Staph aureus 710.830.8 Ps. aeruginosa + Staph. aureus 11.532.3 E.coli + Klebsiella 11.533.8 No growth 4366.2100.0 Total 65100.0 TABLE 1 Table-1: First sample taken at the postoperative site on 3rd postoperative day.
An increase of 4.7% in infection rate was noted in the second sample at 48hours after ultrasound (p=0.0001) [table 2 & 3]. Organism FrequencyPercent Cumulative Percent E. coli 913.8 Ps. aeruginosa 23.116.9 Staph. aureus 710.827.7 Klebsiella 46.233.8 E coli + Klebsiella 23.136.9 Ps. aeruginosa + Staph.aureus 11.538.5 No growth 4061.5100.0 Total 65100.0 Table -2: Second sample taken after ultrasound
Klebsiella was isolated in 4 patients while one patient had Escherichia coli and Klebsiella following ultrasound with an increase in overall infection rate following ultrasound (p<0.0001) [table 2&3]. No patient had growth of Acinetobactar. The culture of the gel from the bottle at the end of the study showed persistence of Klebsiella colony.
sample 1 Sample 2 E. coli Ps. aerugin osa Staph. aureus Klebsiel la Escherich ia coli + Klebsiella Psuedomon as +Staph. aureus No growth Total Pearson chisquare value E. coli 900110011 2.840 # Ps. aeruginosa 02000002 Staph. aureus 00700007 Ps. auriginosa + staph.aureus 00000101 E.coli+ Klebsiella 00001001 No growth 0003004043 Total 9274214065 TABLE 3 Table-3: # P =0.000. E. coli- Escherichia coli; Staph. aureus- Staphylococcus aureus; Ps.aeruginosa-Pseudomonas aeruginosa
DISCUSSION An infection acquired within 48 hours after the admission of the patient in the hospital is known as nosocomial infection . Poor surgical asepsis, type of wound, Poor socio Economic status, over crowded hospitals, lack of guidelines, unawareness among health workers, increasing number of immunocompromised patients are some of the factors increasing the risk of developing nosocomial infections . (Global patient safety challenge 2005-2006, www.who.int/patientsafety) Gel and the probe has been proved to be a source of infection by various studies [2,4,5,6,7,13,14]. The coupling gel is commonly used in radiology, cardiology and physiotherapy [3,5]. As patients with open wound or fresh scar are at high risk of infection, necessary precaution is to be followed to reduce the risk of nosocomial infection.
Sykes et al have reported a high level (64.5%) of contamination in ultrasound equipment's . Prospective studies have reported the bacterial colonisation in the transducer, the property of the gel to harbour bacteria and the methods of cleaning the probe[5,16]. Infection transmission from the gel has been reported by Hutchinson et al and Spencer et al but no reported gel contamination with klebsiella [2,12]. Outbreaks following ultrasound, both after diagnostic as well as intervention has been reported as cross infection [6,12,17,18]. The gel supports bacterial contamination and has no bactericidal agent . An increase in incidence of infection by 4.7% following ultrasound in our study is statistically significant(p<0.0001) and the presence of Klebseilla in 5 patients following ultrasound clearly indicates that the source of infection is the gel since, the probe was cleaned after every ultrasound. The contamination of gel at the manufacturing unit as in our case should be avoided by following aseptic precautions.
Fumigation of the room does not eliminate the bacteria from either the gel bottle or from the larger gel container. Addition of bactericidal agents to the gel can help prevent nosocomial infection. As the gel is used for ECG leads, it may contribute to infection in cardiothoracic intensive care units. Use of sterile pack will prevent infection transmission. Outbreak of infection following prostate biopsy has proved the importance of use of sterile gel as well as probe covers during intervention . As the cost of a sterile gel pack is high, its use has not gained popularity among radiologists and sonologists in India. But it’s use has to be insisted in ICU and post operative patients. We agree with muradali et al and Hutchinson et al that single wipe of the probe does significantly reduce the bacterial contamination [2,5]. But, it does not elimnate the bacteria in the gel. Reduction of bacteria by 45% has been reported by single wipe technique, which is adequate for a routine Ultrasound clinics . Double cleaning methods with use of cloth and disinfectant is better than the single cloth wipe [13,14]
As our study shows a significant increase(p=0.0001) in infection, it is recommended all probes be cleaned by any of the methods at the end of the day [5,18,19]. Most cost effective method is by cleaning with 0.05% chlorhexidine at the end of the day . Soap and water, 70% alcohol and chlorine can be used for vaginal probes sterilization . Safety instructions and guidelines has to be followed as recommended [4,10]. Probe vendors should provide instructions for cleaning the probe. Ultraviolet light can be used for cleaning probe in operation theatres with a microbial reduction of 100% . As probe covers and sterile gels are used, the incidence will be less when compared to ultrasound done at the wards. In conclusion, ultrasound gel permits bacterial growth and is a significant source of infection in postoperative patients. Use of sterile gel is recommended in post operative patients along with probe sterilisation to prevent increase of nosocomial infection.
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