Disinfectant Susceptibility Research Articles

Environmental persistence and disinfectant susceptibility of Klebsiella pneumoniae recovered from pinnipeds stranded on the California Coast

Hypermucoviscous K. pneumoniae (HMV) are emergent zoonotic pathogens associated with increased invasiveness and pathogenicity in terrestrial and marine mammals. In this study, HMV and non-HMV isolates recovered from stranded pinnipeds were used to investigate: 1) their persistence in sea and fresh water microcosms at 10 and 20°C, 2) their capacity to form biofilms, and 3) the biocide efficacy of four disinfectants on their planktonic and biofilm phenotypes. Results indicated that although HMV isolates were significantly more mucoviscous, non-HMV isolates displayed significantly greater capacity to form biofilms (p < 0.05). Additionally, non-HMV isolates persisted in greater numbers in both sea- and freshwater, particularly at 20°C. These two phenomena could be associated with the greater growth observed for non-HMV isolates in in-vitro growth-curve assays (p < 0.05). Similar susceptibility to disinfectants was detected in HMV and non-HMV isolates when exposed for 24 h; however, the minimal biofilm disinfectant eradication concentration for HMV isolates was significantly higher than that for non-HMV when exposed to disinfectants for 0.5 h. This information should be taken into consideration when developing biosecurity protocols in facilities holding marine mammals in captivity.

Limited association between disinfectant use and either antibiotic or disinfectant susceptibility of Escherichia coli in both poultry and pig husbandry

BackgroundFarm disinfectants are widely used in primary production, but questions have been raised if their use can select for antimicrobial resistance. The present study examined the use of disinfectants in poultry and pig husbandry and its contribution to the antibiotic and disinfectant susceptibility of Escherichia coli (E. coli) strains obtained after cleaning and disinfection. On those field isolates antibiotic susceptibility was monitored and susceptibility to commonly used active components of farm disinfectants (i.e. glutaraldehyde, benzalkoniumchloride, formaldehyde, and a formulation of peracetic acid and hydrogen peroxide) was tested.ResultsThis study showed a high resistance prevalence (> 50%) for ampicillin, sulfamethoxazole, trimethoprim and tetracycline for both production animal categories, while for ciprofloxacin only a high resistance prevalence was found in broiler houses. Disinfectant susceptibility results were homogenously distributed within a very small concentration range. Furthermore, all E. coli strains were susceptible to in-use concentrations of formaldehyde, benzalkoniumchloride and a formulation of peracetic acid and hydrogen peroxide, indicating that the practical use of disinfectants did not select for disinfectant resistance. Moreover, the results showed no indications for the selection of antibiotic resistant bacteria through the use of disinfectants in agricultural environments.ConclusionOur study suggests that the proper use of disinfectants in agricultural environments does not promote antibiotic resistance nor reduce E. coli disinfectant susceptibility.

Disinfectant Susceptibility of Biofilm Formed by Listeria monocytogenes under Selected Environmental Conditions.

Listeria monocytogenes is a one of the most important food-borne pathogens. Its ability to form biofilm contributes to increased resistance to disinfectants and inefficient disinfection, posing a serious threat for the food industry, and in the end the consumer. The aim of this study was the comparison of the biofilm formation ability of L. monocytogenes strains on stainless steel, under different environmental conditions (temperature, pH, NaCl concentration, nutrients availability), and the assessment of biofilm susceptibility to disinfectants. The bactericidal activity of four disinfectants in two concentrations (100% and 50% of working solution) against biofilm was conducted on four clinical strains, four strains isolated from food and one reference strain ATCC 19111. It was found that biofilm susceptibility to disinfectants was influenced by environmental conditions. Biofilm susceptibility correlated with the decrease of temperature, pH, nutrients availability and salinity of the environment. The least sensitive to disinfectants was biofilm produced at pH = 4 (the bacterial number ranged from 0.25 log CFU × cm−2 to 1.72 log CFU × cm−2) whereas the most sensitive was biofilm produced at pH = 9 (5.16 log CFU × cm−2 to 7.84 log CFU × cm−2). Quatosept was the most effective disinfectant, regardless of the conditions. In conclusion, biofilm susceptibility to disinfectants is strain-dependent and is affected by environmental conditions.

Disinfectant and Antimicrobial Susceptibility Profiles of Campylobacter coli Isolated in 1998 to 1999 and 2015 from Swine and Commercial Pork Chops.

Susceptibility profiles were determined for 111 Campylobacter coli strains obtained in 1998 to 1999 and 2015 from market age pigs and pork chops against 22 disinfectants and 9 antimicrobials. Resistance to tetracycline (TET) was observed in 44.4% of 1998 to 1999 strains, and the antibiotic resistance profile was TET. But strains obtained in 2015 from swine and retail pork chops had 75% TET resistance and the antibiotic resistance profile was TET, followed by azithromycin-erythromycin-TET-telithromycin-clindamycin. Antimicrobial resistance increased in 2015 strains. All strains were resistant to triclosan, and 84.1% and 95.8% of strains in 1998 to 1999 and 2015, respectively, were chlorhexidine resistant. All strains were susceptible to benzalkonium chloride. There was a shift toward higher susceptibility to chlorhexidine, triclosan, P-128, OdoBan, CPB, and CPC in 2015 swine and pork chop strains compared with 1998 to 1999 strains. The disinfectants Tek-Trol and providone-iodine, tris(hydroxylmethyl)nitromethane (THN) and formaldehyde demonstrated the highest susceptibilities. Didecyldimethylammonium chloride (C10AC) appeared to be about equally effective as benzyldimethyltetradecylammonium chloride (C14BAC) for inhibiting C. coli, and both were more effective than C8AC and C12BAC, but C16BAC was not efficient at inhibiting C. coli. The BACs, C12BAC and C14BAC, were the most effective ingredients in DC&R. Also, C12BAC and C14BAC, or these two in synergy with C10AC were responsible for inhibition of C. coli at high P-128 MICs. No cross-resistance was observed between antibiotics and disinfectants. The continued use of THN and formaldehyde in DC&R should be evaluated since these components are not effective, and their inclusion adds unwanted chemicals in the environment. PRACTICAL APPLICATION: Campylobacter species cause diarrheal disease throughout the world. Disinfectants are often used on the farm, in veterinary medicine, by the food processing industry, in restaurants, and in consumer's homes. Limited information is available in the literature showing how disinfectants or disinfectant components may affect the many different foodborne pathogens, and, specifically, Campylobacter coli studied here. The knowledge generated in this study concerning the interactions of a broad array of disinfectants against C. coli may well affect the types of disinfectants and disinfectant formulations allowable for use by medical personnel, producers, food processors, restaurants, and consumers.

Genetic similarity, antibiotic resistance and disinfectant susceptibility of Listeria monocytogenes isolated from chicken meat and chicken-meat processing environment in Mato Grosso, Brazil

A trial was conducted to determine the genotypic and phenotypic profiles of Listeria monocytogenes (LM) isolated from chicken meat and chicken-meat processing environment in an export-authorized industrial facility in Brazil. A total of 37 LM isolates were separated according to their genetic similarity by pulsed-field gel electrophoresis (PFGE), classified by serotype and lineage using multiplex PCR, tested for antibiotic resistance using the disk-diffusion technique, and analyzed for disinfectant susceptibility using the minimal inhibitory concentration (MIC) approach. The majority of the isolates belonged to lineage II, serotypes 1/2a or 3a. Genotypically, isolates from packaged frozen carcasses and knives & boards of the cutting room were similar to those of carcasses after chiller. Isolates from packaged frozen boneless thighs, however, were very peculiar. Regardless the origin, high level of resistance to peracetic acid, ampicillin and sulfonamides were detected. Overall, our findings suggest that the prevalence of LM in the cutting room is not sustained by the continuous flow of new bacteria, but mainly by an already established microbiota that persists in the environment. Therefore, more effective strategies of cleaning and disinfection must be adopted by the chicken meat industry in order to reduce the prevalence of LM in the processing environment.

Antibiotic and Disinfectant Susceptibility Patterns of Airborne Bacteria Isolated from Restaurants in Nigeria.

Antibiotics resistant airborne bacteria in restaurants have considerable effect on not only the life of food handlers, but also the quality and stability of food products. This study was carried out with the objectives of identifying the type of airborne bacteria associated with the restaurants and their susceptibility patterns to commonly used antibiotics and disinfectants. Using depositional sampling technique, air samples were collected from restaurant kitchens and dining rooms and cultured aerobically. Bacterial isolates were identified based on biochemical tests and selective/differential plating. Among the ten (10) bacterial species isolated and identified, Staphylococcus aureus 7 (19%), Micrococcus spp. 6 (17%), Staphylococcus spp. 5 (14%), and Bacillus subtilis 4 (11%) were predominant. A total of fourteen antibiotics were used in this study: Amoxicillin + clavulanic acid (AU) (25), gentamycin (CN) (10μg), pefloxacin (PEF) (10μg), ofloxacin (OFX) (30μg), streptomycin (S) (30μg), chloramphenicol (CH) (30μg), co-trimoxazole. (SXT) (30μg), fluoroquinolone (SP) (10μg), ciprofloxacin (CPX) ((10μg)), amoxicillin (AM) (30μg), ampiclox (APX) (30μg), erythromycin (E) (19μg), ceftriaxone (CTR) (30μg) and cefuroxime (Z) (20μg). Antimicrobial susceptibility test results revealed that S. aureus had susceptibility of 6 (85.7%) each to ciprofloxacin and gentamycin but resistant to amoxicillin, ampiclox and cefuroxime while Pseudomonas aeruginosa had susceptibility of 3 (100%) each to amoxicillin + clavulanic acid and gentamycin but resistant to fluoroquinolone and co-trimoxazole. Susceptibility to Jik and Dettol was appreciable; they were bacteriostatic at 25-100% concentrations (Minimum Inhibition Concentrations (MIC) and bactericidal (Minimum Bactericidal Concentrations (MBC) at mostly 100% concentration. ‘Mama Lemon’ was bacteriostatic to only two isolates at 50 and 100% concentrations but not bactericidal. Enterobacter sp. was susceptible to neither the antibiotics nor the disinfectants. All the three disinfectants showed no efficacy at concentrations lower than 25%. The presence of potentially pathogenic bacteria which are not susceptible to antibiotics and disinfectants in the air of restaurants constitutes a serious health hazard not only to the restaurant workers and their customers, but also the general public.

Disinfectant Susceptibility Testing of Non-Fermenting Gram Negative Bacilli

Context: Non-fermenting Gram negative bacilli (NFGNB) are the major cause of nosocomial infections worldwide. This will be life threatening, if not monitored with proper surveillance and treatment. If disinfectants are diluted, the ineffectiveness of disinfectants leads to microbial resistance. Objective: This study was conducted to identify the disinfectant (both skin and surface disinfectant) susceptibility of NFGNB with three different concentrations. Materials and methods: In this study, 3500 samples were cultured by agar plating technique. Out of which 240 yielded NFGNB which were identified by conventional biochemical tests. Agar cup diffusion method was done for disinfectant susceptibility testing. Results and discussion: Among 240 NFGNB, 100% were sensitive to chlorhexidine gluconate at manufacturer’s concentration. If the concentration was reduced the susceptibility percentage also was reduced. 97% and 39% of isolates were susceptible to hydrogen peroxide and povidone iodine respectively, irrespective to the concentration. Conclusion: Hence, it can be stated that NFGNB has its own susceptibility to individual disinfectant at manufacturer’s concentration. But none showed 100% sensitivity when the concentration was reduced than manufacturer’s concentration. Thus complete surveillance and monitoring of these organisms with disinfectant suceptibility is mandatory to control the hospital acquired infections.

Evidence of antimicrobial and disinfectant resistance in a remote, isolated wild pig population

The spread of antimicrobial resistant E. coli within the environment is a global concern. Wildlife such as feral pigs have been identified as a possible reservoir of antimicrobial resistant bacteria. A cross-sectional survey of free-ranging, feral pigs within the Kimberley region of northwestern Australia was conducted to estimate the prevalence of antimicrobial and disinfectant resistant E. coli in this population. Of the 493 faecal samples collected, 115 E. coli isolates were randomly selected and their identity confirmed by matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF MS). Isolates were screened for susceptibility to 14 veterinary antimicrobials (including antimicrobials not permitted for use in Australia) using MIC broth microdilution using Sensititre™ (BOPO6F) and breakpoints according to CLSI and EUCAST guidelines. Isolates also underwent disinfectant susceptibility testing to six disinfectants at their recommended concentration for use as well as at a twofold dilution, based on methods adapted from the CLSI agar plate dilution method. A moderate prevalence of resistance was observed to sulfadimethoxine (50.4%; 58/115) and florfenicol (27.0%; 31/115). A low prevalence of resistance was estimated to chlortetracycline (5.2%; 6/115) and multi-drug resistance was only identified in 1.7% (2/115) of E.coli isolates tested. Isolates were susceptible to five of the six disinfectants screened. Feral pigs could potentially act as a reservoir of antimicrobial resistance in the environment with possible implications for domestic livestock. The role that feral pigs might play in transmission of antimicrobial resistance requires further investigation, and the occurrence of resistance in such isolated populations needs to be considered when attempting to infer source attribution of antimicrobial resistance in livestock and human populations.

Characterization of NDM-7 Carbapenemase-Producing Escherichia coli Isolates in the Arabian Peninsula.

The purpose of this study was to characterize the New Delhi metallo-beta lactamase (NDM)-7-producing Enterobacteriaceae isolated in the Arabian Peninsula. Enterobacteriaceae identified to carry blaNDM-7 in a collection of 157 NDM-producing isolates from Kuwait, Oman, Saudi Arabia, and the United Arab Emirates (UAE) were investigated for their antibiotic and disinfectant susceptibility, and resistance gene content. The virulence profile, phylogenetic and sequence types of the isolates were also determined. The plasmids carrying the blaNDM-7 were transferred, and their complete nucleotide sequence was determined. Four NDM-7-producing Escherichia coli isolated in Kuwait, Oman, and the UAE, respectively, were identified. They were clonally unrelated, carried a few virulence determinants only, and belonged to clonal complexes CC10 and CC23, or ST448. They were all multi-drug resistant but remained susceptible to fosfomycin, tigecycline, and colistin. In all isolates, blaNDM-7 was located on IncX3 type plasmids of a variable size, not harboring any further resistance genes. The plasmids exhibited a high degree of similarity to each other and to pKpN01-NDM7 from Canada, with various size deletions and insertions. Our findings show that IncX3 type plasmids play an important role in the spread of the currently rare NDM-7 variant in the Arabian Peninsula. This association of blaNDM-7 with the IncX3-type plasmid is particularly worrisome, as this type of plasmid was proved to spread other carbapenemases in various species of Enterobacteriaceae worldwide at a high efficiency.

Disinfectant susceptibility in south east Australian pig herds

Disinfectant susceptibility in south east Australian pig herds

Disinfectant and Antimicrobial Susceptibility Profiles of Salmonella Strains from Feedlot Water-Sprinkled Cattle: Hides and Feces

Disinfectant and Antimicrobial Susceptibility Profiles of Salmonella Strains from Feedlot Water-Sprinkled Cattle: Hides and Feces

Isolation of indigenous bacteria from a cafeteria kitchen and their biofilm formation and disinfectant susceptibility

Bacterial biofilm formation in foodservice facilities is a continuous cross-contamination risk through survival and persistence despite disinfectant treatments. In this study, we evaluated biofilm formation and disinfectant susceptibility of 178 strains obtained from a cafeteria kitchen and 70 foodborne pathogens and analyzed results by multivariate data analyses. A total of 23 areas in a cafeteria kitchen were selected for bacterial isolation and identification. The capacity for biofilm formation was tested using a crystal violet assay, and disinfectant susceptibility was examined using an agar well diffusion assay and resazurin reduction assay. The most frequently isolated genera were Bacillus (33%), Acinetobacter (17%), Kocuria (12%) and Staphylococcus (5%). The genus Bacillus showed the strongest capacity of the biofilm formation. The foodborne bacteria exhibited a wide range of susceptibility to disinfectants, such as sodium hypochlorite, hydrogen peroxide, benzalkonium chloride, lactic acid and citric acid. However, the susceptibilities changed after biofilm formation in a strain-dependent manner, and the relative resistance levels changed among the isolates. Overall, this study will be a great resource for selecting and using disinfectants in foodservice facility hygienic practices.

Disinfectant and Antimicrobial Susceptibility Profiles of the Big Six Non-O157 Shiga Toxin–Producing Escherichia coli Strains from Food Animals and Humans

The disinfectant and antimicrobial susceptibility profiles of 138 non-O157 Shiga toxin-producing Escherichia coli strains (STECs) from food animals and humans were determined. Antimicrobial resistance (AMR) was moderate (39.1% of strains) in response to 15 antimicrobial agents. Animal strains had a lower AMR prevalence (35.6%) than did human strains (43.9%) but a higher prevalence of the resistance profile GEN-KAN-TET. A decreasing prevalence of AMR was found among animal strains from serogroups O45 > O145 > O121 > O111 > O26 > O103 and among human strains from serogroups O145 > O103 > O26 > O111 > O121 > O45. One animal strain from serogroups O121 and O145 and one human strain from serogroup O26 had extensive drug resistance. A high prevalence of AMR in animal O45 and O121 strains and no resistance or a low prevalence of resistance in human strains from these serogroups suggests a source other than food animals for human exposure to these strains. Among the 24 disinfectants evaluated, all strains were susceptible to triclosan. Animal strains had a higher prevalence of resistance to chlorhexidine than did human strains. Both animal and human strains had a similar low prevalence of low-level benzalkonium chloride resistance, and animal and human strains had similar susceptibility profiles for most other disinfectants. Benzyldimethylammonium chlorides and C10AC were the primary active components in disinfectants DC&R and P-128, respectively, against non-O157 STECs. A disinfectant FS512 MIC ≥ 8 μg/ml was more prevalent among animal O121 strains (61.5%) than among human O121 strains (25%), which may also suggest a source of human exposure to STEC O121 other than food animals. Bacterial inhibition was not dependent solely on pH but was correlated with the presence of dissociated organic acid species and some undissociated acids.

Disinfectant susceptibility of different Salmonella serotypes isolated from chicken and egg production chains.

The study aimed to serotype the Salmonella isolates recovered from chicken and egg production chains, and to investigate the disinfectant resistance phenotypes and genotypes of these isolates. The Salmonella isolates were serotyped, and the minimal inhibitory concentrations (MICs) of disinfectants were determined. Results showed that the Salmonella isolates recovered from both chains were diverse, and the serotypes in each part of the production chain and between the two production chains were significantly different. In the chicken production chain, 19 different serotypes were recovered, while only five serotypes were found in the egg production chain. The isolates showed a high susceptibility to didecyldimethylammonium bromide (DDAB) but a low susceptibility to benzalkonium chloride (BC), benzalkonium bromide (BAB) and chlorhexidine (CHX). Salmonella Enteritidis and Salmonella Typhimurium were more resistant to BC and BAB. The qacEΔ1 and qacF resistance genes were detected in 26·7 and 7·7% of the isolates respectively. The qacEΔ1 gene was frequently found in Salmonella Derby and Salm.Enteritidis (P<0·05). Our findings indicated that Salmonella was commonly present in both chains, and could serve as a critical vector in spreading disinfectant resistance associated with different serotypes. This study first demonstrated disinfectant resistance phenotypes and genotypes of serotyped Salmonella. The study highlights the need for monitoring the disinfectant resistance varied in different Salmonella serotypes.

Cleaning and Disinfection of Bacillus cereus Biofilm.

Methodology has been evolving for the testing of disinfectants against bacterial single-species biofilms, as the difficulty of biofilm remediation continues to gain much-needed attention. Bacterial single-species biofilm contamination presents a real risk to good manufacturing practice-regulated industries. However, mixed-species biofilms and biofilms containing bacterial spores remain an even greater challenge for cleaning and disinfection. Among spore-forming microorganisms frequently encountered in pharmaceutical manufacturing areas, the spores of Bacillus cereus are often determined to be the hardest to disinfect and eradicate. One of the reasons for the low degree of susceptibility to disinfection is the ability of these spores to be encapsulated within an exopolysachharide biofilm matrix. In this series of experiments, we evaluated the disinfectant susceptibility of B. cereus biofilms relative to disassociated B. cereus spores and biofilm from a non-spore-forming species. Further, we assessed the impact that pre-cleaning has on increasing that susceptibility.

Phenotypic Detection of Virulence Markers, Antibiotic and Disinfectant Susceptibility of Bacterial Isolates from Automated Teller Machine Keypads, Computer Keyboards and Mice in Uyo, Nigeria

Phenotypic Detection of Virulence Markers, Antibiotic and Disinfectant Susceptibility of Bacterial Isolates from Automated Teller Machine Keypads, Computer Keyboards and Mice in Uyo, Nigeria

Characterization of antibiotic and disinfectant susceptibility profiles among Pseudomonas aeruginosa veterinary isolates recovered during 1994-2003.

To evaluate susceptibility of Pseudomonas aeruginosa veterinary isolates to antibiotics and disinfectants. Pseudomonas aeruginosa isolates collected from dogs (n = 155) and other animals (n = 20) from sixteen states during 1994-2003 were tested for susceptibility. Most isolates were resistant to twenty-one antimicrobials tested, and the highest prevalence of resistance was to β-lactams (93.8%) and sulphonamides (93.5%). Fluoroquinolone resistance did not increase from 1994 to 2003. Ciprofloxacin and enrofloxacin had a 5 and 16% prevalence of resistance, respectively, while sarafloxacin and nalidixic acid had a prevalence of resistance of 97 and 98%, respectively. Strains were pan-resistant to triclosan and chlorhexidine, were highly resistant to benzalkonium chloride and demonstrated high susceptibility to other disinfectants. Didecyldimethylammonium chloride was the most active ammonium chloride. Inducible resistance was observed to cetyl ammonium halides, chlorhexidine and benzyl ammonium chlorides, which formulate disinfectants used in veterinary clinics and dairies. Organic acid inhibition was associated with the dissociated acid species. Dissociated organic acids appear able to inhibit Ps. aeruginosa, and rates of fluoroquinolone resistance merit sustained companion animal isolate surveillance. This is the first report of Ps. aeruginosa susceptibility to 24 disinfectants and illustrates the high resistance of Ps. aeruginosa to both antibiotics and disinfectants.

Achromobacter bacteraemia outbreak in a paediatric onco-haematology department related to strain with high surviving ability in contaminated disinfectant atomizers

Achromobacter spp. are Gram-negative bacilli from aqueous environments, occasionally involved in bacteraemia in immunocompromised hosts and in outbreaks. We describe the characteristics of an achromobacter bacteraemia outbreak in a paediatric onco-haematology department. Throughout a one-year period, 16 blood cultures from seven patients were positive for Achromobacter sp. All patients were immunocompromised, febrile, and central venous catheter (CVC) holders. A microbiological study was performed in patients' rooms, completed with an analysis of the disinfectant atomizers (didecyl diammonium chloride 0.25%, Surfanios, DMA). In total, 41 clinical and environmental strains were analysed by enterobacterial repetitive intergenic consensus (ERIC) polymerase chain reaction (PCR), repetitive PCR, and random amplified polymorphic DNA (RAPD)-PCR, and pulsed-field gel electrophoresis (PFGE). The bactericidal activity of DMA was studied on two Achromobacter sp. representative strains and one Pseudomonas aeruginosa reference strain, comparing biofilm and planktonic growth models. The seven patients, including two severe cases, were successfully treated by systemic antimicrobial therapy and/or catheter removal. The 25 environmental isolates were recovered with the following chronology: hospital filtered tap water, disinfectant atomizers, and patients' rooms. All environmental, patient, and atomizer strains had identical PCR and PFGE patterns. The disinfectant susceptibility assay revealed that the strain isolated from the atomizers had high survival abilities in biofilm conditions and remained resistant to DMA after short contact periods. The use of disinfectant atomizers associated with the survival of Achromobacter in the atomizer pipes may explain the contamination and colonization of the CVC. Control measures (non-atomizer containers and use of sterile water) allowed the eradication of the source and the outbreak control.

Susceptibility of high-risk human papillomavirus type 16 to clinical disinfectants

Little to nothing is known about human papillomavirus (HPV) susceptibility to disinfection. HPV is estimated to be among the most common sexually transmitted diseases in humans. HPV is also the causative agent of cervical cancersand other anogenital cancers and is responsible for a significant portion of oropharyngeal cancers. While sexual transmission is well documented, vertical and non-sexual transmission may also be important. Using recombinant HPV16 particles (quasivirions) and authentic HPV16 grown in three-dimensional organotypic human epithelial culture, we tested the susceptibility of high-risk HPV to clinical disinfectants. Infectious viral particles were incubated with 11 common clinical disinfectants, appropriate neutralizers were added to inactivate the disinfectant and solutions were filter centrifuged. Changes in the infectivity titres of the disinfectant-treated virus were measured compared with untreated virus. HPV16 is a highly resistant virus; more so than other non-enveloped viruses previously tested. The HPV16 quasivirions showed similar resistance to native virions, except for being susceptible to isopropanol, the triple phenolic and the lower concentration peracetic acid-silver (PAA-silver)-based disinfectant. Authentic virus and quasivirus were resistant to glutaraldehyde and ortho-phthalaldehyde and susceptible to hypochlorite and the higher concentration PAA-silver-based disinfectant. We present the first disinfectant susceptibility data on HPV16 native virions, which show that commonly used clinical disinfectants, including those used as sterilants in medical and dental healthcare facilities, have no effect on HPV16 infectivity. Policy changes concerning disinfectant use are needed. The unusually high resistance of HPV16 to disinfection supports other data suggesting the possibility of fomite or non-sexual transmission of HPV16.

Antimicrobial Drug Resistance and Disinfectants Susceptibility of Pseudomonas aeruginosa Isolates from Clinical and Environmental Samples in Jimma University Specialized Hospital, Southwest Ethiopia

P. aeruginosa is one of the most important pathogen that causes nosocomial infections often acquired from hospital environment and contaminated medical devices. The infections caused by this bacterium are particularly problematic because it is inherently resistant to several unrelated antimicrobial agents and antiseptics. Hence, the aim of this study was to determine drug resistance and disinfectants susceptibility of P. aeruginosa isolated from clinical samples and hospital environments. A laboratory based cross sectional study was conducted from May to September, 2012 on a total of 81 P. aeruginosa isolates. A standard bacteriological technique (conventional biochemical tests and pigment production) was used to identify the bacterium. Drug resistance and disinfectant susceptibility tests were determined by Kirby-Bauer disc-diffusion and through the classic method of successive dilutions respectively. In this study a total of 305 (160 clinical and 145 environmental) samples were investigated for P. aeruginosa and 81 isolates were obtained. This gives an overall P. aeruginosa isolation rate of 26.5% (81/305). About 47.5% of the clinical and 34.2% environmental isolates were detected from wounds and ward sinks respectively. Of these P. aeruginosa isolates, 95.1% were resistance to Trimethoprim-sulphametoxazole, 62% to Gentamicin, and 58% to Ceftriaxone. But, only 4.9% of isolates were resistance to Amikacin. Moreover, disinfectant susceptibility test revealed that hydrogen peroxide and sodium hypochlorite had a higher (92.6% & 91.4%) bactericidal activity compared to ethanol and savlon at the recommended user dilution. In general, our results indicated that P. aeruginosa was significantly resistance to commonly prescribed antimicrobial drugs, a situation that demands a more rational and appropriate use of antibiotics. Hydrogen peroxide and sodium hypochlorite were relatively more effective when used in recommended dilution. However, all tested disinfectants or antiseptics showed reduced bactericidal activities in higher dilutions. Therefore, strict adherence to the recommended dilution is important for better activity. The correct use of them also has to be considered appropriately as part of infection control practices.