Antiseptic Resistance Genes Research Articles

Molecular study of resistance of Staphylococcus aureus to antiseptic quaternary ammonium compounds.

This study determined the prevalence of qac and smr genes in clinical Staphylococcus aureus isolates from hospital-acquired infections and their susceptibility to quaternary ammonium compounds (QACs) and antibiotics, and correlated the presence of antiseptic resistance genes with antibiotic resistance. Susceptibility of 150 non-duplicate clinical S. aureus isolates to antimicrobials and benzalkonium chloride (BAC) was determined by disk diffusion and MIC method, respectively. Resistant strains were analysed by multiplex PCR for the presence of qac and smr genes. Reduced susceptibility to BAC was detected in 30% of isolates (MIC cut-off >8mg/L). QAC resistance genes were detected in 13 isolates with reduced BAC susceptibility. The most frequently detected genes were qacA/B (10 isolates; 22.2%), followed by qacJ (10; 22.2%), smr (8; 17.8%), qacG (8; 17.8%) and qacH (3; 6.7%). There was a strong positive correlation between presence of QAC resistance genes and higher BAC MIC associated with qacA/B, qacJ and smr genes. There was a statistically significant prevalence of antiseptic resistance genes among isolates resistant to cefoxitin, ciprofloxacin, clindamycin, oxacillin, tetracycline and erythromycin. This study highlights the prevalence of qac and smr genes in clinical S. aureus isolates with resistance to QACs. There was an association between the presence of antiseptic resistance genes and resistance to different antibiotics, which may be attributed to the presence of both groups of genes on the same plasmid or to selection of resistant strains. More studies are needed on the clinical relevance of the presence of genes controlling resistance to antiseptics.

Development of a real-time assay to determine the frequency of qac genes in methicillin resistant Staphylococcus aureus

PurposeThe emergence of antiseptic resistance and/or antiseptic-resistance genes in methicillin-resistant Staphylococcus aureus (MRSA) may result in failure of decolonization treatments. Plasmid-encoded efflux pump genes qacA/B and qacC (smr) confer tolerance to chlorhexidine and quaternary ammonium compounds. The objective of this study was to develop and validate a multiplex real time-PCR assay for detection of antiseptic-resistance genes, apply the assay on 200 MRSA isolates and explore if carriage of these genes was associated with resistance to topical antibiotics. MethodologyA SYBR-Green based multiplex real time-PCR assay was developed to detect qacA/B, qacC, and mecA (internal control) simultaneously. The multiplex assay was compared against conventional single-plex PCR followed by agarose gel electrophoresis, using DNA from the first 73 MRSA isolates, followed by multiplex testing of the remaining 127 MRSA isolates. All 200 MRSA isolates were tested for susceptibility to mupirocin, retapamulin, neomycin, bacitracin and octenidine. The genetic diversity of the isolates was investigated by spa-typing. ResultsThe concordance between multiplex and conventional PCR, in assignments of qacA/B and qacC status were 99%(72/73) and 100%(73/73) respectively. Among 200 MRSA isolates, 48(24%) and 44(23%) were found to harbour qacA/B and qacC genes, respectively. These isolates remained susceptible to many common decolonization agents, except mupirocin. The predominant spa-types were t020 and t1081 (41 and 32 isolates respectively). ConclusionThe real-time assay performed acceptably for the detection of qac genes. A high prevalence of antiseptic-resistance genes were detected in the MRSA isolates in our population and appeared to be associated with spa-type t1081.

Resistance pattern and distribution of carbapenemase and antiseptic resistance genes among multidrug-resistant Acinetobacter baumannii isolated from intensive care unit patients.

Nosocomial infections caused by multidrug resistant Acinetobacter baumannii have emerged as a serious problem in healthcare settings worldwide. A total of 100 A. baumannii clinical isolates from immunocompromised patients hospitalized in ICUs in Iran were investigated for antimicrobial susceptibility and the presence of carbapenemase and antiseptic resistance genes. All isolates were resistant to one or more antibiotics, with the most frequent resistance found against ciprofloxacin and imipenem (100 %) and piperacillin (99 %). The MICs of biocides were determined by the agar dilution method. No apparent resistance to biocides was seen among the 100 A. baumannii isolates. All isolates were effectively inhibited by the user's defined concentrations of cetrimide, benzalkonium chloride and glutardaldehyde. The intrinsic β-lactamase gene, blaOXA-51-like, was detected in all A. baumannii isolates. Coexistence of blaOXA-51 andblaOXA-23 was encountered in 89 % of isolates. However, genes blaOXA-58, blaSIM and blaIMP were not detected in any isolates. While A. baumannii isolates were sensitive to biocides, they carried qac genes with the qacEΔ1 gene being the most common, at a frequency of 91 %. Our study revealed the high frequency of multidrug- and carbapenem-resistant isolates of A. baumannii in ICU patients, with a high prevalence of the genes blaOXA-23 and blaOXA-51. However, no apparent biocide resistance was seen in A. baumannii isolates. It appears that appropriate surveillance and control measures are essential to prevent the emergence and transmission of MDR A. baumannii in Iran.

Molecular Characterization of Nasal Methicillin-Resistant Staphylococcus aureus Isolates Showing Increasing Prevalence of Mupirocin Resistance and Associated Multidrug Resistance following Attempted Decolonization.

Sequential methicillin-resistant Staphylococcus aureus (MRSA) isolates from patients following attempted mupirocin nasal decolonization showed an increase in mupirocin resistance (MR) from 6.6% to 20%. MR isolates from patients who failed decolonization yielded indistinguishable spa types and carried multiple antimicrobial and antiseptic resistance genes, which may guide infection control and prevention.

Prevalence of antiseptic-resistance genes in Staphylococci isolated from orthokeratology lens and spectacle wearers in Hong Kong

Purpose: To investigate the prevalence of antiseptic-resistance genes in Staphylococci isolated from periorbital tissues and accessories of orthokeratology (ortho-k) lens and spectacle wearers. To characterize gene positive isolates for minimum inhibitory concentrations (MIC) to antiseptics and susceptibility to antibiotics.

Investigating antibiotics, antibiotic resistance genes, and microbial contaminants in groundwater in relation to the proximity of urban areas.

Groundwater is an essential public and drinking water supply and its protection is a goal for global policies. Here, we investigated the presence and prevalence of antibiotic residues, antibiotic resistance genes (ARGs), mobile genetic elements (MGEs), and microbial contamination in groundwater environments at various distances from urban areas. Antibiotic concentrations ranged from below detection limit to 917 ng/L, being trimethoprim, macrolide, and sulfonamide the most abundant antibiotic classes. A total of eleven ARGs (aminoglycoside, β-lactam, chloramphenicol, Macrolide-Lincosamide-Streptogramin B - MLSB, sulfonamide, and tetracycline), one antiseptic resistance gene, and two MGEs were detected by qPCR with relative abundances ranging from 6.61 × 10-7 to 2.30 × 10-1 copies/16S rRNA gene copies. ARGs and MGEs were widespread in the investigated groundwater environments, with increased abundances not only in urban, but also in remote areas. Distinct bacterial community profiles were observed, with a higher prevalence of Betaproteobacteria and Bacteroidetes in the less-impacted areas, and that of Firmicutes in the contaminated groundwater. The combined characteristics of increased species diversity, distinct phylogenetic composition, and the possible presence of fecal and/or pathogenic bacteria could indicate different types of contamination. Significant correlations between ARGs, MGEs and specific taxa within the groundwater bacterial community were identified, revealing the potential hosts of resistance types. Although no universal marker gene could be determined, a co-selection of int1, qacEΔ1 and sulI genes, a proxy group for anthropogenic pollution, with the tetC, tetO, tetW resistance genes was identified. As the tet group was observed to follow the pattern of environmental contamination for the groundwater samples investigated in this study, our results strongly support the proposal of this group of genes as an environmental tracer of human impact. Overall, the present study investigated several emerging contaminants in groundwater habitats that may be included in monitoring programs to enable further regulatory and protection measures.

Frequency of antiseptic resistance genes in clinical staphycocci and enterococci isolates in Turkey

BackgroundDisinfectants and antiseptics are biocides widely used in hospitals to prevent spread of pathogens. It has been reported that antiseptic resistance genes, qac’s, caused tolerance to a variety of biocidal agents, such as benzalkonium chloride (BAC) and chlorhexidine digluconate (CHDG) in Staphylococcus spp. isolates. We aimed to search the frequency of antiseptic resistance genes in clinical Staphylococcus spp. and Enterococcus spp. isolates to investigate the possible association with antiseptic tolerance and antibiotic resistance.MethodsAntiseptic resistance genes (qacA/B, smr, qacG, qacH, and qacJ) isolated from Gram-positive cocci (69 Staphylococcus spp. and 69 Enterococcus spp.) were analyzed by PCR method. The minimum inhibitory concentrations (MICs) of BAC and CHDG were determined by agar dilution method, whereas antibiotic susceptibility was analyzed by disk diffusion method according to Clinical and Laboratory Standards Institute (CLSI) criteria.ResultsThe frequency of antiseptic resistance genes was found to be high (49/69; 71.0%) in our clinical staphylococci isolates but absent (0/69; 0%) in enterococci isolates. The frequency of qacA/B and smr genes was higher (25/40; 62.5% and 7/40; 17.5%, respectively) in coagulase negative staphylococci (CNS) when compared to Staphylococcus aureus strains (3/29; 10.3%, and 4/29; 13.8%, respectively). In contrast, the frequency of qacG and qacJ genes was higher (11/29; 37.9% and 8/29; 27.5%, respectively) in S. aureus than those of CNS (5/40; 12.5%, 10/40; 25.0%) strains. qacH was not identified in none of the strains. We found an association between presence of antiseptic resistance genes and increased MIC values of BAC (>4 μg/mL) in staphylococci and it was found to be statistically statistically significant (p < 0.01). We also showed that MICs of BAC and CHDG of vancomycin-resistant enterococci (VRE) isolates were significantly higher than those of vancomycin-susceptible enterococci (VSE) isolates (p < 0.01).ConclusionsFor our knowledge, our study is the first to investigate antiseptic resistance genes in enterococci and also qacG, qacH, and qacJ genes in staphylococci isolates in Turkey. Further studies are needed to revise the biocide policy and to support infection control programs to avoid the development of new resistance mechanisms.

The treatment of wastewater containing pharmaceuticals in microcosm constructed wetlands: the occurrence of integrons (int1\u20132) and associated resistance genes (sul1\u20133, qacE\u03941)

The aim of this study was to analyze the occurrence of sulfonamide resistance genes (sul1–3) and other genetic elements as antiseptic resistance gene (qacEΔ1) and class 1 and class 2 integrons (int1–2) in the upper layer of substrate and in the effluent of microcosm constructed wetlands (CWs) treating artificial wastewater containing diclofenac and sulfamethoxazole (SMX), which is a sulfonamide antibiotic. The bacteria in the substrate and in the effluents were equipped with the sul1–2, int1, and qacEΔ1 resistance determinants, which were introduced into the CW system during inoculation with activated sludge and with the soil attached to the rhizosphere of potted seedlings of Phalaris arundinacea ‘Picta’ roots (int1). By comparing the occurrence of the resistance determinants in the upper substrate layer and the effluent, it can be stated that they neither were lost nor emerged along the flow path. The implications of the presence of antibiotic resistance genes in the effluent may entail a risk of antibiotic resistance being spread in the receiving environment. Additionally, transformation products of SMX were determined. According to the obtained results, four (potential) SMX transformation products were identified. Two major metabolites of SMX, 2,3,5-trihydroxy-SMX and 3,5-dihydroxy-SMX, indicated that SMX may be partly oxidized during the treatment. The remaining two SMX transformation products (hydroxy-glutathionyl-SMX and glutathionyl-SMX) are conjugates with glutathione, which suggests the ability of CW bacterial community to degrade SMX and resist antimicrobial stress.

Distribution of antiseptic resistance genes in Staphylococcus spp. from bovine mastitis

The purpose of this study was the determination of antiseptic resistance genes (qacA/B and qacC) from staphylococcal mastitis in cattle in various regions of Turkey. In total, 283 isolates (Burdur: 36, Hatay: 47 and Van: 200) were studied, and the antiseptic resistance genes were detected using simplex PCR. The distribution of the qacA/B and qacC genes, mediating resistance against quaternary ammonium compounds, was found to vary among the different isolates. The qacA/B genes were found in three of the Burdur isolates, six of the Hatay isolates and seven of the Van isolates. The qacC gene was found in two of the Burdur isolates, none of the Hatay isolates and two of the Van isolates. The presence of these genes and transmission among Staphylococcus spp. strains may pose risks in the control of mastitis, as well as to public health.

Novel Multiplex PCR Assay for Detection of Chlorhexidine-Quaternary Ammonium, Mupirocin, and Methicillin Resistance Genes, with Simultaneous Discrimination of Staphylococcus aureus from Coagulase-Negative Staphylococci.

Methicillin-resistant Staphylococcus aureus (MRSA) is a clinically significant pathogen that is resistant to a wide variety of antibiotics and responsible for a large number of nosocomial infections worldwide. The Agency for Healthcare Research and Quality and the Centers for Disease Control and Prevention recently recommended the adoption of universal mupirocin-chlorhexidine decolonization of all admitted intensive care unit patients rather than MRSA screening with targeted treatments, which raises a serious concern about the selection of resistance to mupirocin and chlorhexidine in strains of staphylococci. Thus, a simple, rapid, and reliable approach is paramount in monitoring the prevalence of resistance to these agents. We developed a simple multiplex PCR assay capable of screening Staphylococcus isolates for the presence of antiseptic resistance genes for chlorhexidine and quaternary ammonium compounds, as well as mupirocin and methicillin resistance genes, while simultaneously discriminating S. aureus from coagulase-negative staphylococci (CoNS). The assay incorporates 7 PCR targets, including the Staphylococcus 16S rRNA gene (specifically detecting Staphylococcus spp.), nuc (distinguishing S. aureus from CoNS), mecA (distinguishing MRSA from methicillin-susceptible S. aureus), mupA and mupB (identifying high-level mupirocin resistance), and qac and smr (identifying chlorhexidine and quaternary ammonium resistance). Our assay demonstrated 100% sensitivity, specificity, and accuracy in a total of 23 variant antiseptic- and/or antibiotic-resistant control strains. Further validation of our assay using 378 randomly selected and previously well-characterized local clinical isolates confirmed its feasibility and practicality. This may prove to be a useful tool for multidrug-resistant Staphylococcus monitoring in clinical laboratories, particularly in the wake of increased chlorhexidine and mupirocin treatments.

Frequency of antiseptic resistance genes and reduced susceptibility to biocides in carbapenem-resistant Acinetobacter baumannii.

The aim of this study is to determine the frequency of quaternary ammonium compound-resistant genes, including qacA/B, qacC/D, qacE, qacΔE1, qacG, qacJ, and β-lactamase genes, including blaCTX-M, blaTEM, blaSHV, blaOXA-23, blaVIM, blaIMP, blaNDM and blaGIM in 51 isolates of carbapenem-resistant Acinetobacter baumannii collected over a period of 2 years and to determine the MIC of chlorhexidine and quaternary ammonium compound-based disinfectant benzalkonium chloride. The qac and bla genes were detected by the PCR method. The MICs were determined using the broth microdilution method. The MIC of benzalkonium chloride was in the range of 4 to 64 µg l-1 and chlorhexidine in the range of 4 to 64 µg l-1. The qacΔE1 gene was detected in 96.07 % (49/51) isolates and qacE in 31.37 % (16/51), qacG in 23.52 % (12/51) and qacA/B in 13.72 % (7/51). The qacC/D genes and qacJ were not found in any of these strains in this study. The frequency of bla genes was as follows: 84.31 % (43/51) for blaOXA-23, 33.33 % (17/51) for blaTEM, 27.45 % (14/51) for blaVIM, 19.61 % (10/51) for blaSHV, 17.65 % (9/51) for blaNDM, 11.76 % (6/51) for blaGIM and 7.8 % (4/51) for the blaIMP. The blaCTX-M genes were negative in all the strains. From the study, we concluded that reduced susceptibility to the two disinfectants, as well as qac and bla genes, was prevalent among A. baumannii isolates from the hospital environment. This study may offer hospitals important information about the control of nosocomial infections caused by A. baumannii.

Detection of Antiseptic Resistance Genes among Staphylococcus aureus Colonising Nurses and Coagulase-Negative Staphylococci Isolated from Clinical Specimens at Teaching Hospitals in Southwest of Iran

Background: The wide application of antibiotics and antiseptics for patient therapy and medical equipment and surfaces disinfection has resulted in the emergence of resistant microorganisms. Staphylococcus aureus and coagulase-negative Staphylococci (CoNS) are found as a part of the normal resident flora in human so that up to two-thirds of the healthy populations are permanently or transiently colonized by S. aureus and CoNS. Chlorhexidine is an antiseptic agent particularly effective against Gram-positive bacteria. It is widely used for hygienic hand wash to prevent transmission of Staphylococci nosocomial infections. The plasmid-borne qacA/B, qacC, and smr genes confer resistance to cationic antiseptic agents in S. aureus and CoNS. Objectives: The objective of the current study was to characterize the antibiotic resistance and susceptibility to quaternary ammonium compounds (QACs) in methicillin-sensitive S. aureus (MSSA), methicillin-resistant S. aureus (MRSA), methicillin-sensitive coagulase-negative staphylococci (MSCoNS), and methicillin-resistant coagulase-negative Staphylococci (MRCoNS). Methods: In this study, the antibiotic susceptibility and resistance to Chlorhexidine in 120 Staphylococcal strains were evaluated by disc diffusion and Minimum inhibitory concentration (MIC) of Chlorhexidine gluconate (CHG) methods, respectively. The MICs of CHG were determined in triplicate by broth micro-dilution, and the presence of mecA, qacA/B, qacC, and smr genes was examined by PCR assay. Results: Of total 60 S. aureus isolates, 51 (85%) were MRSA, and of 60 CoNS, 7 (11.66%) were MRCoNS. The results showed that the MIC of Chlorhexidine for all 120 isolates was 1-16 _g/mL. 15 (12.5%) isolates carried qacA/B gene, 26 (21.7%) carried qacC gene, and 38 (31.7%) carried smr gene. Conclusions: Maintenance of MRSA isolates in the attendance of low amounts of antiseptics could result in the decreased susceptibility to antiseptics.

Frequency of Antiseptic Resistance Among Staphylococcus aureus and Coagulase-Negative Staphylococci Isolated From a University Hospital in Central Iran.

Reduced biocide susceptibility in Staphylococci is associated with various antiseptic resistance genes encoding efflux systems. Our aim was to determine the susceptibility to three disinfectant agents, including benzalkonium chloride (BAC), benzethonium chloride (BZT), and chlorhexidine digluconate (CHDG) among clinical isolates of Staphylococcus aureus and coagulase-negative Staphylococci (CoNS). The minimum inhibitory concentration (MIC) of 60 methicillin-resistant S. aureus (MRSA), 54 methicillin-sensitive S. aureus (MSSA) and 51 CoNS isolates from a single hospital to three biocidal agents (BAC, BZT, and CHDG) was determined. Biocide resistance genes (qacA/B, smr, qacG, qacH, qacJ, and norA) were analyzed by the polymerase chain reaction assay. All isolates had MICs for BAC and BZT from 0.25 to 8 µg/mL, and for CHDG from 0.5 to 64 µg/mL. qacA/B was the most common biocide resistance gene among all 165 Staphylococcus isolates (76; 46%), which comprised 38 (63.3%) MRSA, 14 (25.9%) MSSA, and 24 (47%) CoNS. Eleven (6.7%) and 24 (14.5%) isolates among the 165 Staphylococci carried smr and norA genes, respectively. In contrast, other resistance genes such as qacG, qacH, and qacJ were absent in all Staphylococci studied. The qacA/B and smr genes were detected concomitantly in 3% of isolates, and 23.6% strains of the total 165 Staphylococcus isolates were negative for each studied gene. The carriage of several biocide resistance genes, including qacA/B, smr, and norA, alone or concurrently, is associated with reduced susceptibility. Use of antiseptics may select for antibiotic-resistant strains and assist their survival in the healthcare environment.

PCR-based detection of composite transposons and translocatable units from oral metagenomic DNA.

A composite transposon is a mobile genetic element consisting of two insertion sequences (ISs) flanking a segment of cargo DNA often containing antibiotic resistance (AR) genes. Composite transposons can move as a discreet unit. There have been recently several reports on a novel mechanism of movement of an IS26-based composite transposon through the formation of a translocatable unit (TU), carrying the internal DNA segment of a composite transposon and one copy of a flanking IS. In this study, we determined the presence of composite transposons and TUs in human oral metagenomic DNA using PCR primers from common IS elements. Analysis of resulting amplicons showed four different IS1216 composite transposons and one IS257 composite transposon in our metagenomic sample. As our PCR strategy would also detect TUs, PCR was carried out to detect circular TUs predicted to originate from these composite transposons. We confirmed the presence of two novel TUs, one containing an experimentally proven antiseptic resistance gene and another containing a putative universal stress response protein (UspA) encoding gene. This is the first report of a PCR strategy to amplify the DNA segment on composite transposons and TUs in metagenomic DNA. This can be used to identify AR genes associated with a variety of mobile genetic elements from metagenomes.

Prevalence of antiseptic resistance genes increases in staphylococcal isolates from orthokeratology lens wearers over initial six-month period of use.

The purpose of this study was to investigate the prevalence of antiseptic-resistance (QAC) genes in staphylococci colonizing periorbital tissues and accessories of orthokeratology (ortho-k) lens wearers over a 6-month period and determine the effect of their presence on minimum inhibitory (MIC) and bactericidal concentrations (MBC) of disinfectants and log reduction of multipurpose contact lens solutions (MPS). Staphylococci were isolated from periorbital tissues and accessories of patients before commencing ortho-k therapy and at two subsequent visits. Presence of QAC genes in 116 S. aureus and 67 CNS isolates was determined by PCR and association with period of ortho-k use determined. MICs and MBCs of staphylococci gene-positive were compared with gene-negative strains and the effectiveness of four MPS for rigid contact lenses investigated. S. aureus carriage rates in the conjunctiva decreased significantly from 41.2% (baseline) to 11.8% (3-months), and 13.3% (6-months) (p trend 0.03), while CNS increased from 58.8%(baseline) to 94.1% (3-months), and 93.3% (6-months) (p trend 0.02). Prevalence of qacA/B increased considerably over time (S. aureus: 4.4% to 15.4%, CNS: 6.7% to 25%), but frequency of smr was relatively stable. Only five CNS isolates harboured qacH. MICs and MBCs of gene-positive isolates were significantly increased and three MPS did not achieve a 3-log reduction of many QAC-positive strains. Ortho-k lens wear contributed to changes of staphylococcal carriage rates in the conjunctival sac. Use of MPS containing quaternary ammonium compounds may select for the carriage of organisms harbouring QAC genes, as the low concentration of disinfecting agents is not adequate for killing gene-positive strains.

Antiseptic Resistance in Methicillin Sensitive and Methicillin Resistant Staphylococcus aureus Isolates from Some Major Hospitals, Iran.

Extensive use of antibiotics and biocide in treatment of patients and cleaning of surfaces and medical equipment has led to the emergence of resistant microorganisms. The current research goals to determine the antiseptics Minimum Inhibitory Concentration value in Staphylococcus aureus (methicillin -resistant Staphylococcus aureus and methicillin sensitive Staphylococcus aureus) isolates from some major hospitals in Iran and to detect qacA/B, norA , smr and blaZ genes. Two hundred isolates of S. aureus including 100 MRSA and 100 MSSA clinical isolates were collected from 4 hospitals in the west of Iran during period 2012 to 2013. Detection of disinfectant resistant genes (qac A/B, smr and norA), antimicrobial resistance genes (mecA and blaZ) and SCCmec typing of MRSA isolates was performed by PCR. MIC of chlorhexidine digluconate (CHX) in 70% of MRSA and 30% of MSSA strains was 8-16 µg/ml. High level of MIC of citrimide (>2 µg/ml) in MRSA and MSSA isolates was 20% and 5% , respectively. MIC of benzalkonium chloride (BC) in 80% of MRSA and 83% of MSSA isolates was less than 2 µg/ml; only 9% of MRSA had MIC higher than 2 µg/ml. Frequency of antiseptic and antibiotic resistance genes norA, blaZ and qacA/B in MRSA isolates were 83%, 98% and 9%, respectively; while this value for MSSA isolates were 62%, 8% and 0%, respectively. The smr gene was not detected in both MRSA and MSSA isolates. In all biocides high MIC were observed in SCCmec type III and IVc. High frequency of qacA/B gene was found in SCCmec type III,Vc and IVb, which were 66.6% ,22% and 11.1% respectively. We found SCCmec types III, Vc was related to high MIC of biocide in MRSA isolates.

Characterization of Staphylococcus aureus infections in children with Down syndrome

Staphylococcus aureus infections in the Down syndrome (DS) population have not been well characterized. This study determined clinical and molecular characteristics of S. aureus infections in children with DS followed at Texas Children's Hospital (TCH), from 2001 to 2011. Patients were retrospectively identified from an ongoing S. aureus surveillance study. Medical records were reviewed. Isolates were characterized by antimicrobial susceptibility, pulsed-field gel electrophoresis patterns, and detection of PVL genes (pvl), mupA (high-level mupirocin resistance gene), smr (chlorhexidine resistance conferring gene), and Staphylococcal Chromosomal Cassette mec (SCCmec) type. Twenty-six patients with DS had a total of 34 S. aureus infections (8 recurrent); 61% were MRSA. DS patients represented 16.8 per 10,000 community onset S. aureus infections seen at TCH. Among 26 initial infections 17 were skin and soft tissue (SSTI), 7 were outer or middle ear and 2 were invasive infections. Seventeen patients were hospitalized. Thirteen (65%) of 20 available isolates were USA300, 14 were pvl+, 5 were mupA+, and 8 were smr+. Five of 8 (63%) recurrent infections were ear infections. All 4 recurrent ear isolates available for study were smr+, ciprofloxacin non-susceptible and treated with ciprofloxacin otic drops. S. aureus infections among patients with DS were similar in presentation to other patient groups, except for a greater proportion being associated with ear infections. Seventy percent of ear fluid isolates carried antiseptic and fluoroquinolone resistance genes. A study of a greater number of DS patients is warranted to further explore these findings.

Prevalence of antiseptic-resistance genes in staphylococci isolated from orthokeratology lens and spectacle wearers in Hong Kong.

To compare isolation of staphylococci from periorbital tissues and accessories of orthokeratology (ortho-k) lens and spectacle wearers and investigate prevalence of antiseptic-resistance (QAC) genes. To determine minimum inhibitory concentrations (MIC) of antiseptics and antibiotic susceptibility of isolates. Staphylococci were isolated from eyelids, eyelashes, and conjunctival sacs of 23 ortho-k lens wearers and 20 spectacle wearers. Samples were also collected from ortho-k lenses, lens cases, and spectacle frames. Isolations of Staphylococcus aureus were compared between ortho-k subjects and controls for all samples and for coagulase-negative staphylococci (CNS) from conjunctival sacs. QAC genes were amplified in 110 S. aureus and 59 CNS isolates and prevalence compared in isolates from ortho-k lens and spectacle wearers. Associations were assessed between presence of QAC genes and antibiotic and antiseptic susceptibility. Although isolation of S. aureus did not differ significantly in periorbital samples from ortho-k and control subjects, QAC genes were significantly more common in both S. aureus and CNS from ortho-k subjects (odds ratio 4.4 and 10.74, respectively). Overall, qacA/B was the predominant gene detected, being present in 26.5% CNS and 11% S. aureus. smr and qacH were present in 12% of CNS, but were less common in S. aureus. QAC gene-positive isolates had higher MICs to benzalkonium chloride and chlorhexidine digluconate. Our results suggest that long-term use of multipurpose solutions containing quaternary ammonium compounds may select for carriage of organisms harboring QAC genes. As these genes are associated with antibiotic resistance, their increased prevalence in isolates from contact lens wearers is a concern.

Methicillin-susceptible and -resistant Staphylococcus aureus with high-level antiseptic and low-level mupirocin resistance in Malaysia.

The prevalence and spread of mupirocin and antiseptic resistance among colonizing and infectious Staphylococcus aureus were determined. S. aureus isolated from anterior nares and infection sites of patients hospitalized in the largest tertiary care referral hospital in Malaysia was investigated for mupirocin and antiseptic susceptibility testing, and for PCR detection of mupA, qacA/B, and smr genes. Twelve isolates showed resistance to mupirocin by disk diffusion, of which 10 (3.8%) harbored the mupA gene. Minimum inhibitory concentrations (MICs) ranged from 64 to 768 μg/ml for mupA positive and below 46 μg/ml for negative isolates. The mupA was more common among ST239 isolates (70%). The qacA/B was carried in 67 out of 95 methicillin-resistant Staphylococcus aureus (MRSA) (70.5%) and 3 out of 164 methicillin-susceptible Staphylococcus aureus (MSSA) (1.8%), while smr was carried in 6 out of 95 MRSA (6.3%) strains. MICs ranged from 3.9 to 15.6 μg/ml for benzethonium chloride (BTC) and benzalkonium chloride (BKC), and from 10.3 to 20.7 μg/ml for chlorhexidine digluconate (CHG). Isolates with qacA/B and smr or qacA/B alone showed higher MIC (20.7 μg/ml for CHG and 15.6 μg/ml for BTC and BKC) than the isolates that lacked antiseptic resistance genes (10.3 μg/ml for CHG and 3.9 μg/ml for BTC and BKC). In 16 cases, ST239 was isolated from the infection site and the nares simultaneously, and shared identical resistance patterns (qacAB or qacAB+smr), suggesting possible endogenous infection. Spread of low-level mupirocin resistance expressing ST239 MRSA and high-level resistance expressing emerging ST1, co-existing with antiseptic-resistant genes showing elevated MICs, should be monitored for effective infection control.

Detection of Antiseptic-Resistance Genes in Pseudomonas and Acinetobacter spp. Isolated From Burn Patients

Quaternary ammonium compounds (QAC), which contain benzalkonium chloride as the most widely used agent, are employed as wound and skin antiseptics, as well as disinfectants in hospitals. The resistance mechanism to disinfectants is usually determine by genes which are related to resistance to quaternary ammonium compounds, namely, qacE, qacΔE1, qacΔE1 that are found in Gram-negative bacteria. The aim of this study was to determine the incidence of antiseptic resistance genes, qacE and qacΔE1, in clinical isolates of Pseudomonas aeruginosa and Acinetobacter bumanii. In this study, 83 clinical isolates of Pseudomonas aeruginosa, and 5 isolates of Acinetobacter baumannii from burn hospitals in Tehran and Isfahan provinces in 2010-2011, were tested by the PCR method. Out of the 83 clinical isolates of Pseudomonas aeruginosa, 49 isolates (50%) had the qacE gene, and 76 isolates (91.5%) had the qacΔE1 gene. In addition, in 5 isolates of Acinetobacter bumanii, 2 isolates (40%) had the qacE gene, and 4 isolates (80%) had the qacΔE1 gene. This study shows that the genes which harbored resistance to quaternary ammonium compound antiseptics are widespread among Pseudomonas aeruginosa and Acinetobacter bumanii isolates in burn patients.