Cloning of a Cation Efflux Pump Gene Associated with Chlorhexidine Resistance in
            <i>Klebsiella pneumoniae</i>

Fang, Chi-Tai; Chen, Haur-Chuan; Chuang, Yung-Yu; Chang, Shan-Chwen; Wang, Jann-Tay

doi:10.1128/aac.46.6.2024-2028.2002

Cited by 66 publications

(58 citation statements)

References 19 publications

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“…The same condition was reported for S. enterica (17). Garaizar Typhimurium LT2 by microarray analysis and reported that a region including 13 genes responsible for the anaerobic assimilation of allantoin as a nitrogen source was absent in all S. enterica serovar [4,5,12:i:Ϫ] strains but was present in serovar Typhimurium LT2 strains. However, the physiological implication of the deletion in S. enterica remains unclear.…”

Section: Discussionmentioning

confidence: 61%

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Isolation of a Chromosomal Region ofKlebsiella pneumoniaeAssociated with Allantoin Metabolism and Liver Infection

et al. 2004

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Klebsiella pneumoniae liver abscess with metastatic complications is an emerging infectious disease in Taiwan. To identify genes associated with liver infection, we used a DNA microarray to compare the transcriptional profiles of three strains causing liver abscess and three strains not associated with liver infection. There were 13 clones that showed higher RNA expression levels in the three liver infection strains, and 3 of these 13 clones contained a region that was absent in MGH 78578. Sequencing of the clones revealed the replacement of 149 bp of MGH 78578 with a 21,745-bp fragment in a liver infection strain, NTUH-K2044. This 21,745-bp fragment contained 19 open reading frames, 14 of which were proven to be associated with allantoin metabolism. The K2044 (⌬allS) mutant showed a significant decrease of virulence in intragastric inoculation of BALB/c mice, and the prevalence of this chromosomal region was significantly higher in strains associated with liver abscess than in those that were not (19 or 32 versus 2 of 94; P ‫؍‬ 0.0001 [ 2 test]). Therefore, the 22-kb region may play a role in K. pneumoniae liver infection and serve as a marker for rapid identification.

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Section: Discussionmentioning

confidence: 61%

“…The phagemid library was obtained by using a Gigapack III Gold packaging kit (Stratagene) as previously described (12). A total of 5,760 clones were amplified by PCR with primers in vector ( Table 2), and 3,146 of these clones were randomly selected for the microarray.…”

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confidence: 99%

Isolation of a Chromosomal Region ofKlebsiella pneumoniaeAssociated with Allantoin Metabolism and Liver Infection

et al. 2004

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“…A few AcrAB multidrug efflux systems have been characterized in Klebsiella spp. (7,20,23,28), but the sequencing data of K. pneumoniae strain MGH78578 show that many others potentially are present, as in closely related E. coli species (3). In this study, we characterized a gene cluster in K. pneumoniae LM21 that exhibits strong homologies with the EefABC RND efflux system-encoding operon, initially described in E. aerogenes (18).…”

Section: Discussionmentioning

confidence: 99%

A Tripartite Efflux Pump Involved in Gastrointestinal Colonization by Klebsiella pneumoniae Confers a Tolerance Response to Inorganic Acid

et al. 2008

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In vivo assays showed that a ⌬eefA isogenic mutant strain normally colonized the gastrointestinal tract in single-strain tests but was significantly impaired in competition against wild-type strain LM21. Although the cecum was the compartment with the highest number of CFU, the ⌬eefA mutant also was detected in the stomach in numbers smaller than those of the wild-type strain. The expression of this potential efflux pump could not be linked to any antimicrobial drug resistance phenotype, but it conferred on the bacteria an acid tolerance response to inorganic acid. The expression of the eef promoter region, measured via a lacZ reporter construction, was slightly induced by an acidic environment and also by hyperosmolarity but not by the presence of bile salts. These results suggest that an efflux pump can confer measurable ecological benefits on K. pneumoniae in an environment with high competition potential.Klebsiella pneumoniae is an opportunistic pathogen responsible for many nosocomial infections, and most clinical strains exhibit high levels of resistance to a wide variety of structurally unrelated antibiotics. Epidemiological studies have shown that, whatever the infection site, the first stage in nosocomial infections due to K. pneumoniae consists of the colonization of the patient's gastrointestinal (GI) tract (6,16). This pathogen therefore has to sense and respond to numerous different environments in order to survive and, consequently, to persist in the GI tract of the host. The first major barrier encountered following oral consumption is stomach acidity. The bacteria then enter the small intestine, where they encounter stresses associated with volatile fatty acids, variations in pH and osmolarity, and competition with endogenous flora. Using signature-tagged mutagenesis (STM) in a murine model, we previously identified 13 genes encoding factors required for the in vivo colonization of the GI tract by K. pneumoniae LM21 (14). All of these mutants were selected for their inability to colonize the murine intestinal tract under competitive conditions. One of the identified genes potentially encoded a protein involved in a cryptic efflux pump, EefABC, previously described in Enterobacter aerogenes (18). This pump is thought to belong to the resistance-nodulation-division (RND) family and to be composed of an inner membrane protein, EefB, a periplasmic intermediate, EefA, and an outer membrane protein, EefC (18). No specific function has been attributed to this structure so far, whose expression is repressed by the H-NS repressor in the heterologous host Escherichia coli (18). In addition to the export of antimicrobials, several recent publications have highlighted the natural physiological role of efflux pumps in exporting noxious substances out of the bacterial cell, thereby allowing the bacteria to survive in hostile environments and facilitating intestinal colonization (11,13,24,30). In this report, we characterized the eef-like operon of K. pneumoniae and investigated the role of the potentially enc...

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“…Although the evidence is still ambiguous, assertions have been made that other antimicrobials might similarly select for resistance and that biocides in general could affect susceptibilities to chemically unrelated compounds (11,24,25,40). With respect to CHX, use of this biocide has been associated with decreased susceptibility in hospital surveys (1,21), while a recent report has associated a cation efflux pump with decreased CHX susceptibility in Klebsiella pneumoniae (8). Daily dental hygiene applications of CHX in human volunteers over 2 years, however, resulted in only a slight change in distribution toward those organisms which were less sensitive to CHX (38).…”

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confidence: 99%

Effects of a Chlorhexidine Gluconate-Containing Mouthwash on the Vitality and Antimicrobial Susceptibility of In Vitro Oral Bacterial Ecosystems

McBain

Bartolo

Catrenich

et al. 2003

Appl Environ Microbiol

119

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Oral bacterial microcosms, established using saliva inocula from three individuals, were maintained under a feast-famine regime within constant-depth film fermenters. Steady-state communities were exposed four times daily, postfeeding, to a chlorhexidine (CHX) gluconate-containing mouthwash (CHXM) diluted to 0.06% (wt/vol) antimicrobial content. The microcosms were characterized by heterotrophic plate counts and PCRdenaturing gradient gel electrophoresis (DGGE). CHXM caused significant decreases in both total anaerobe and total aerobe/facultative anaerobe counts (P < 0.05), together with lesser decreases in gram-negative anaerobes. The degree of streptococcal and actinomycete inhibition varied considerably among individuals. DGGE showed that CHXM exposure caused considerable decreases in microbial diversity, including marked reductions in Prevotella sp. and Selenomonas infelix. Pure-culture studies of 10 oral bacteria (eight genera) showed that Actinomyces naeslundii, Veillonella dispar, Prevotella nigrescens, and the streptococci were highly susceptible to CHX, while Lactobacillus rhamnosus, Fusobacterium nucleatum, and Neisseria subflava were the least susceptible. Determination of the MICs of triclosan, CHX, erythromycin, penicillin V, vancomycin, and metronidazole for microcosm isolates, before and after 5 days of CHXM exposure, showed that CHXM exposure altered the distribution of isolates toward those that were less susceptible to CHX (P < 0.05). Changes in susceptibility distributions for the other test agents were not statistically significant. In conclusion, population changes in plaque microcosms following repeated exposure to CHXM represented an inhibition of the most susceptible flora with a clonal expansion of less susceptible species.Chlorhexidine (CHX), a cationic bis-biguanide biocide with low mammalian toxicity and broad-spectrum antibacterial (6) activity, was first described in 1954 (5). The primary mechanism of action of this biocide is membrane disruption, causing concentration-dependent growth inhibition and cell death (18). Secondary interactions causing inhibition of proteolytic and glycosidic enzymes may also be significant (15). With respect to dental hygiene applications, the cationic nature of CHX enables it to bind to tooth surfaces and oral mucosa, reducing pellicle formation and increasing substantivity through controlled release of the agent (2). The efficacy of CHX in reducing oral bacterial viability (14,36,42), strongly inhibiting plaque regrowth, and preventing gingivitis (25) has been demonstrated in many studies (7). Relatively few investigations have considered longer-term effects of CHX use. An early study, however, demonstrated that oral treatment of human volunteers with CHX resulted in a 30 to 50% reduction in total bacterial counts with an associated reduction in counts of Streptococcus mutans (38).Recent reports have demonstrated that the chlorinated diphenylether antibacterial triclosan (TCS) can select for mutants in the FabI gene of Escherichia coli at sublethal co...

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Cloning of a Cation Efflux Pump Gene Associated with Chlorhexidine Resistance in Klebsiella pneumoniae

Cited by 66 publications

References 19 publications

Isolation of a Chromosomal Region ofKlebsiella pneumoniaeAssociated with Allantoin Metabolism and Liver Infection

Isolation of a Chromosomal Region ofKlebsiella pneumoniaeAssociated with Allantoin Metabolism and Liver Infection

A Tripartite Efflux Pump Involved in Gastrointestinal Colonization by Klebsiella pneumoniae Confers a Tolerance Response to Inorganic Acid

Effects of a Chlorhexidine Gluconate-Containing Mouthwash on the Vitality and Antimicrobial Susceptibility of In Vitro Oral Bacterial Ecosystems

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