Disinfectant Susceptibility Research Articles

Disinfectant and Antibiotic Susceptibility Profiles of Escherichia coli O157:H7 Strains from Cattle Carcasses, Feces, and Hides and Ground Beef from the United States

The disinfectant and antibiotic susceptibility profiles of 344 Escherichia coli O157:H7 strains from cattle carcasses, feces, and hides and ground beef from the United States were determined. A low prevalence of antibiotic resistance was observed (14%). The highest prevalences of resistance were to sulfisoxazole (10.5%), tetracycline (9.9%), streptomycin (7%), and chloramphenicol (4.9%). Four strains were resistant to eight antibiotics (two strains from ground beef and one strain each from hide and preevisceration carcass swabs of cull cattle at harvest). Pulsed-field gel electrophoresis analysis of the E. coli O157:H7 strains revealed two major groups (designated 1 and 2) composed of 17 and 20 clusters, respectively. Clusters 1A, 1B, 1C, and 1G.1 were associated with multidrug-resistant strains. There was no observed correlation between disinfectant resistance and antibiotic resistance. Sixty-nine (20%) of the 344 strains were resistant to chlorhexidine or benzalkonium chloride or the MICs of benzyldimethyldodecylammonium chloride were elevated. Inducible resistance was observed at elevated concentrations of antibiotics (1.4%) and disinfectants (6.1%). The highest rate of disinfectant inducible resistance was to OdoBan, quaternary ammonium chlorides, and the surface disinfectants F25, FS512, and MG, which are used in dairies, restaurants, and food processing plants. High MICs (1,024 to 4,096 m g/ml) of acetic, lactic, and citric acids were found. The decreasing order of acid potency based on molar MICs (MICs(molar)) was acetic, citric, and lactic acid. The correlation of the concentration of dissociated organic acids and MICs(molar) strongly suggests that the observed inhibition of E. coli O157:H7 was primarily due to dissociated forms of the acids.

A Predominant Multidrug-Resistant Salmonella enterica Serovar Saintpaul Clonal Line in German Turkey and Related Food Products

Recently, Salmonella enterica subsp. enterica serovar Saintpaul has increasingly been observed in several countries, including Germany. However, the pathogenic potential and epidemiology of this serovar are not very well known. This study describes biological attributes of S. Saintpaul isolates obtained from turkeys in Germany based on characterization of their pheno- and genotypic properties. Fifty-five S. Saintpaul isolates from German turkeys and turkey-derived food products isolated from 2000 to 2007 were analyzed by using antimicrobial agent, organic solvent, and disinfectant susceptibility tests, isoelectric focusing, detection of resistance determinants, plasmid profiling, pulsed-field gel electrophoresis (PFGE), and hybridization experiments. These isolates were compared to an outgroup consisting of 24 S. Saintpaul isolates obtained from humans and chickens in Germany and from poultry and poultry products (including turkeys) in Netherlands. A common core resistance pattern was detected for 27 German turkey and turkey product isolates. This pattern included resistance (full or intermediate) to ampicillin, amoxicillin-clavulanic acid, gentamicin, kanamycin, nalidixic acid, streptomycin, spectinomycin, and sulfamethoxazole and intermediate resistance or decreased susceptibility to ciprofloxacin (MIC, 2 or 1 mug/ml, respectively) and several third-generation cephalosporins (including ceftiofur and cefoxitin [MIC, 4 to 2 and 16 to 2 mug/ml, respectively]). These isolates had the same core resistance genotype, with bla(TEM-1), aadB, aadA2, sul1, a Ser83-->Glu83 mutation in the gyrA gene, and a chromosomal class 1 integron carrying the aadB-aadA2 gene cassette. Their XbaI, BlnI, and combined XbaI-BlnI PFGE patterns revealed levels of genetic similarity of 93, 75, and 90%, respectively. This study revealed that a multiresistant S. Saintpaul clonal line is widespread in turkeys and turkey products in Germany and was also detected among German human fecal and Dutch poultry isolates.

Enhanced Decontamination ofBacillusSpores in a Simulated Drinking Water System by Germinant Addition

Contact with germinant solutions followed by commonly used disinfectants as a means to decontaminate Bacillus spores in a model drinking water system was investigated. Biofilms composed of indigenous water system bacteria were accumulated on materials commonly used for residential plumbing, polyvinyl chloride (PVC), and copper, in a continuously stirred tank reactor for controlled shear. Once the biofilms were established, Bacillus thuringiensis kurstaki or B. anthracis Sterne spores were added to the reactor. Pipe surfaces were studied for biofilm accumulation, spore adhesion, and disinfectant (chlorine and monochloramine) susceptibility before and after germinant (1 mM inosine and 8 mM L-alanine) addition. High disinfectant concentrations (up to 100 mg/L free chlorine and 10 mg/L monochloramine) yielded less than a 2 log10 reduction in biofilm-associated viable spores after 60 min. A 4 log10 reduction in the associated spores was observed when coupons were contacted with germinants (24 h) prior to sampling. Germinant contact followed by heat (50°C, 25 min) or disinfection resulted in a greater than 4 log10 reduction in the associated viable spores. Contact with germinants resulted in dramatically enhanced susceptibility of surface-associated spores to elevated water temperature and disinfectants.

Model systems allowing quantification of sensitivity to disinfectants and comparison of disinfectant susceptibility of persistent and presumed nonpersistentListeria monocytogenes

To determine if Listeria monocytogenes persistent strains differ from presumed nonpersistent strains in disinfection susceptibility and to examine the influence of attachment and NaCl on susceptibility. Two model-systems that allowed quantitative inter-strain comparison of disinfectant sensitivity were developed. Persistent L. monocytogenes were not more tolerant to the disinfectants Incimaxx DES and Triquart SUPER than presumed nonpersistent isolates. When calibrating the systems with respect to presence of biological material and cell density, attached bacteria were as sensitive to disinfectants as were planktonic bacteria. Growth with 5% NaCl increased the tolerance of planktonic cells to Incimaxx DES. All strains of spot inoculated L. monocytogenes survived well 20 h of drying when protected by growth media and 5% NaCl, but were not protected by NaCl against disinfection. Persistent strains of L. monocytogenes are as susceptible to disinfectants as are presumed nonpersistent strains and attachment does not render the strains more tolerant to disinfectants. Growth with NaCl affected the susceptibility of the planktonic L. monocytogenes to Incimaxx DES and protected spot inoculated cells during drying. Attachment to surfaces does not per se offer protection to L. monocytogenes against disinfectants and disinfection tolerances do not appear to influence the ability of a strain to persist.

Association and decontamination of Bacillus spores in a simulated drinking water system

The objective of this work was to elucidate the disinfectant susceptibility of Bacillus anthracis Sterne (BA) and a commercial preparation of Bacillus thuringiensis (BT) spores associated with a simulated drinking water system. Biofilms composed of indigenous water system bacteria were accumulated on copper and polyvinyl chloride (PVC) pipe material surfaces in a low-flow pipe loop and uniformly mixed tank reactor (CDC biofilm reactor). Application of a distributed shear during spore contact resulted in approximately a 1.0 and 1.6 log 10 increase in the number of spores associated with copper and PVC surfaces, respectively. Decontamination of spores in both free suspension and after association with biofilm-conditioned pipe materials was attempted using free chlorine and monochloramine. Associated spores required 5- to 10-fold higher disinfectant concentrations to observe the same reduction of viable spores as in suspension. High disinfectant concentrations (103 mg/L free chlorine and 49 mg/L monochloramine) yielded less than a 2-log 10 reduction in viable associated spores after 60 min. Spores associated with biofilms on copper surfaces consistently yielded higher Ct values than PVC.

Antibiotic and Disinfectant Susceptibility Profiles of Vancomycin-Resistant Enterococcus faecium (VRE) Isolated from Community Wastewater in Texas

Vancomycin-resistant Enterococcus faecium (VRE) from human wastewater effluents in a nonclinical semiclosed agri-food system in Texas were characterized for susceptibility to antibiotics and disinfectants. The 50 VRE were resistant to eight fluoroquinolones and 10 of 17 antimicrobials typically active against Gram-positive organisms. The VRE were susceptible to quinupristin/dalfopristin and linezolid. Lack of the insertion element IS1251 correlated with VRE susceptibility to streptomycin and gentamicin at p < 0.0001 and p = 0.033, respectively. An association was observed between pulsed-field gel electrophoresis genotypes Ic and II and susceptibility to streptomycin at p = 0.0006. VRE susceptibility for nine disinfectants and five disinfectant components is shown. Ninety-two percent of the isolates had a minimum inhibitory concentration (MIC) for triclosan > or =2 ppm. Triclosan MICs for many of the VRE were well over expected product application levels. No association was observed between antibiotic resistance and disinfectant susceptibility in these VRE. Enterococci multiply-resistant to vancomycin and aminoglycosides were found in a non-hospital environment where one would not expect to find them.

Double-blind comparative study on the care of the neonatal umbilical cord using 80% ethanol with or without chlorhexidine

We conducted a double-blind comparative study on the effectiveness of 80% ethanol (EtOH), with or without chlorhexidine (CHD), in the prevention of neonatal umbilical colonization by Staphylococcus aureus, the most frequently isolated pathogen on the neonatal umbilicus in the early period. A total of 100 neonates born at the National Tokyo Medical Centre from March to May 2000 and nursed at a maternity ward were enrolled. Forty-eight were randomly allocated to the group for whom umbilical cord disinfection was performed using 80% EtOH containing 0.5% CHD (CHD group) and 52 to disinfection with 80% EtOH alone (EtOH group). The mothers of the neonates and the nursing staff were unaware as to which disinfectant was being used. Disinfection of the umbilicus and the surrounding area was done immediately after birth and twice daily thereafter, after bathing and in the evening, throughout the hospitalization period. Specimens for bacterial culture were taken from the umbilical cord and surrounding skin on day 4 or 5 after birth. As a disinfectant susceptibility test, we checked the minimum killing concentration (MKC) of CHD and EtOH. There was no statistically significant difference between the two groups with respect to sex, gestation period, birthweight, APGAR score or delivery method. In the CHD group, S. aureus was isolated from 25% of the patients, while it was isolated from 57.7% in the EtOH group ( P<0.001). In the CHD group, 50% of the S. aureus strains were MRSA, compared with 73.3% in the EtOH group (non-significant). All the S. aureus strains were killed by the combination of both CHD and EtOH at the concentrations used. In terms of the MKC 90, there was no significant difference between the CHD group and the EtOH group. For the daily care of the neonatal umbilicus, disinfection using 80% EtOH containing CHD was found to be more effective than that using 80% EtOH alone in preventing colonization by S. aureus.

Molecular epidemiology and disinfectant susceptibility of Listeria monocytogenes from meat processing plants and human infections

We have investigated the molecular epidemiology of Listeria monocytogenes from the meat processing industry producing cold cuts and from cases of human listeriosis by discriminative pulsed-field gel electrophoresis (PFGE). A subset of the isolates was also investigated for susceptibility to a disinfectant based on quaternary ammonium compounds (QAC) frequently used in the meat processing industry. The purpose of this investigation was to obtain knowledge of sources, routes of contamination and genetic types of L. monocytogenes present along the production line in the meat processing industry, and to compare meat industry isolates and human isolates. Of the 222 isolates from four meat-processing plants, 200 were from two plants responsible for nearly 50% of the production of cold cuts in the Norwegian market. The strain collection included historical routinely sampled isolates (1989–2002) and isolates systematically sampled through a one year period (November 2001 to November 2002) from fresh meat and production environments in three plants. No isolates were obtained in samples from employees (throat, faeces). Human strains included all available reported isolates from Norwegian patients in selected time periods. The L. monocytogenes PFGE data showed a large genetic heterogeneity, with isolates separated into two genetic lineages and further subdivided into 56 different PFGE profiles. Certain profiles were observed on both sides of production (before and after heat treatment) indicating contamination of end products by fresh meat or fresh meat environments. While fresh meat isolates almost exclusively grouped within lineage I, isolates from end products showed a more balanced distribution between lineages I and II. Ten profiles were common among isolates from human and meat industry. Typing of human isolates identified a previously unrecognised outbreak. Generally, a higher QAC resistance incidence was observed among isolates from the meat processing industry than among human isolates although large plant to plant differences were indicated. No correlation between resistance and PFGE profile or resistance and persistence was observed.

Molecular epidemiology and disinfectant susceptibility of Listeria monocytogenes from meat processing plants and human infections

We have investigated the molecular epidemiology of Listeria monocytogenes from the meat processing industry producing cold cuts and from cases of human listeriosis by discriminative pulsed-field gel electrophoresis (PFGE). A subset of the isolates was also investigated for susceptibility to a disinfectant based on quaternary ammonium compounds (QAC) frequently used in the meat processing industry. The purpose of this investigation was to obtain knowledge of sources, routes of contamination and genetic types of L. monocytogenes present along the production line in the meat processing industry, and to compare meat industry isolates and human isolates. Of the 222 isolates from four meat-processing plants, 200 were from two plants responsible for nearly 50% of the production of cold cuts in the Norwegian market. The strain collection included historical routinely sampled isolates (1989–2002) and isolates systematically sampled through a one year period (November 2001 to November 2002) from fresh meat and production environments in three plants. No isolates were obtained in samples from employees (throat, faeces). Human strains included all available reported isolates from Norwegian patients in selected time periods. The L. monocytogenes PFGE data showed a large genetic heterogeneity, with isolates separated into two genetic lineages and further subdivided into 56 different PFGE profiles. Certain profiles were observed on both sides of production (before and after heat treatment) indicating contamination of end products by fresh meat or fresh meat environments. While fresh meat isolates almost exclusively grouped within lineage I, isolates from end products showed a more balanced distribution between lineages I and II. Ten profiles were common among isolates from human and meat industry. Typing of human isolates identified a previously unrecognised outbreak. Generally, a higher QAC resistance incidence was observed among isolates from the meat processing industry than among human isolates although large plant to plant differences were indicated. No correlation between resistance and PFGE profile or resistance and persistence was observed.

Disinfectant susceptibility testing of avian and swine Campylobacter isolates by a filtration method

The susceptibility testing of disinfectants against Campylobacter jejuni and Campylobacter coli strains from broilers and pigs was investigated. The filtration method European standard EN 1040 was adapted to Campylobacter cultures and validated with reference strains. Two disinfectants were tested: 1% benzalkonium chloride active matter, as quaternary ammonium compound, and 0.63% sodium hypochlorite as chlorine-releasing agent. Both disinfectants were effective against the 34 Campylobacter strains tested after 5 min exposure under in vitro conditions. No link between resistance to disinfectants and antibiotics could be observed.

Antibiotic and disinfectant susceptibility in Enterobacteriaceae isolated from minced meat

The resistance of Enterobacteriaceae isolated from minced to and an amphoteric surfactant, was examined. Despite the wide range of antibiotic resistance occurring in the strains tested, resistance to the disinfectant was not observed.

Efficacy of a variety of disinfectants against Listeria spp

The efficacy of 14 disinfectants against Listeria innocua and two strains of Listeria monocytogenes in the presence of organic matter was studied. Quantitative efficacy tests were used. Many of the disinfectants tested were not as effective on Listeria spp. when the test organisms were dried onto the surface of steel disks (carrier tests) as they were when the organisms were placed in suspension (suspension test). The presence of whole serum and milk (2% fat) further reduced the disinfectant capacities of most of the formulations studied. Only three disinfectants (povidone-iodine, chlorhexidine gluconate, and glutaraldehyde) were effective in the carrier test in the presence of serum; however, all three were ineffective when challenged with milk (2% fat). Only one solution, sodium dichloroisocyanurate, was effective in the presence of milk. All but four formulations (chloramine-T, phosphoric acid, an iodophor, and formaldehyde) were effective in the suspension tests, regardless of the organic load. L. monocytogenes was observed to be slightly more resistant to disinfection than L. innocua was. There was no difference in disinfectant susceptibility between the two strains of L. monocytogenes. These findings emphasize the need for caution in selecting an appropriate disinfectant for use on contaminated surfaces, particularly in the presence of organic material.