L. K. Siu

A global emerging disease of Klebsiella pneumoniae liver abscess: is serotype K1 an important factor for complicated endophthalmitis?

Background and aims: Over the past two decades in Taiwan, pyogenic liver abscess has usually been caused by a single microorganism, Klebsiella pneumoniae, and is frequently associated with the serious complication of endophthalmitis, especially in diabetic patients. However, the relationship between the clinical presentation and bacterial factors remains unclear. The aim of this study was to investigate the clinical features of patients and the serotype and ribotype of K pneumoniae liver abscess. Methods: From July 1991 to June 1998, a total of 134 cases of K pneumoniae liver abscess with 248 K pneumoniae isolates from the same patients were collected from two large medical centres in northern Taiwan. Clinical data were collected from medical records. Serotyping and ribotyping were performed using the countercurrent immunoelectrophoresis method and automated Riboprinter. Results: Serotyping revealed that the most common serotypes were K1 (63.4%) and K2 (14.2%). K1 isolates occurred at a significantly higher frequency (p<0.01) than all other serotypes. Among 134 patients, 105 (78.4%) had suffered from diabetes mellitus for 3–15 years. Fourteen patients (10.4%) had metastatic infection to the eye causing septic endophthalmitis. Liver aspirates, and blood and vitreous pus cultures yielded the same serotype of K pneumoniae in all patients. Among patients with septic endophthalmitis, 92.3% (13/14) were diabetic, and 85.7% (12/14) of the isolates belonged to serotype K1. For molecular typing, different degrees of genetic polymorphism among isolates with the same K1 serotype suggested no particular prevalence of any one strain in K pneumoniae liver abscess. Conclusion: K pneumoniae serotype K1 was significantly associated with liver abscess and the complication of endophthalmitis, especially in diabetic patients. Physicians should request an immediate report of serotyping and susceptibility test results simultaneously if a diagnosis of pyogenic liver abscess has been made so that early and appropriate management for possible complications will not be delayed. The use of ceftriaxone because of its higher concentration in the aqueous humor is suggested to decrease the chance of septic endophthalmitis.

Extended-Spectrum Cephalosporin Compared to Cefazolin for Treatment of Klebsiella pneumoniae-Caused Liver Abscess

ABSTRACT From January 1995 to May 2000, a total of 107 adults with liver abscess due to Klebsiella pneumoniae admitted at a large medical center in northern Taiwan were reviewed. Patients were considered to have received cefazolin or an extended-spectrum cephalosporin if they received at least 3 days of that antibiotic within the first 5 days of hospitalization. Fifty-nine (55.1%) patients received cefazolin, and 48 (44.9%) patients received an extended-spectrum cephalosporin. The demographic data, clinical features, severities of illness, and rates of early drainage for the two groups were comparable. However, the rates of developing complications for the two groups were significantly different (37.3 versus 6.3%, respectively; P < 0.001). Furthermore, six independent factors preventing severe complications following liver abscess due to K. pneumoniae were identified: normal platelet count, alkaline phosphatase less than 300 U/liter, no gas formation in the abscess, APACHE III score less than 40, use of an extended-spectrum cephalosporin, and early drainage. In conclusion, cefazolin therapy may be suboptimal for patients with liver abscess due to K. pneumoniae despite active in vitro susceptibility. Use of an extended-spectrum cephalosporin and early drainage for patients with liver abscess due to K. pneumoniae are suggested.

Differences in phenotypic and genotypic characteristics among imipenem-non-susceptible Acinetobacter isolates belonging to different genomic species in Taiwan.

In this study, we investigated the distribution of genes encoding various carbapenemases as well as their association with carbapenem resistance in clinical isolates of Acinetobacter genomic species from Taiwan. A total of 129 imipenem-non-susceptible and 79 imipenem-susceptible isolates were examined, of which 185 (88.9%) were Acinetobacter baumannii. Among the 185 A. baumannii isolates, imipenem non-susceptibility was more common in isolates with ISAba1-bla(OXA-51-like) (72/75; 96%), bla(OXA-58-like) (33/33; 100%) or bla(OXA-24-like) (7/7; 100%) than in isolates with only bla(OXA-51-like) (4/72; 5.6%). A metallo-beta-lactamase (MBL) gene was present in two isolates of imipenem-resistant A. baumannii, and bla(OXA-58-like) was also present in these isolates. A total of 18% and 1% of imipenem-non-susceptible isolates of A. baumannii were resistant to tigecycline and colistin, respectively. Among the 23 isolates of non-baumannii Acinetobacter spp., bla(OXA-58-like) and MBL genes were widely disseminated in the imipenem-resistant isolates, and isolates with bla(OXA-58-like) and MBL genes had higher imipenem minimum inhibitory concentrations than those with bla(OXA-58-like) alone. Although the rate of non-susceptibility to colistin was 26.7% among the imipenem-non-susceptible isolates of non-baumanniiAcinetobacter, 93.3% and 100% were susceptible to ciprofloxacin and tigecycline, respectively. In conclusion, different isolates of imipenem-non-susceptible A. baumannii and non-baumanniiAcinetobacter contained different carbapenemases and had different antimicrobial susceptibilities.

High-Level Expression of AmpC β-Lactamase Due to Insertion of Nucleotides between −10 and −35 Promoter Sequences in Escherichia coli Clinical Isolates: Cases Not Responsive to Extended-Spectrum-Cephalosporin Treatment

ABSTRACT Two Escherichia coli isolates were recovered from the blood of two cancer patients and were demonstrated to produce high levels of the AmpC β-lactamase with isoelectric points of >9.0. The hypertranscription of ampC RNA was observed by Northern blot hybridization in both isolates. One isolate (isolate EC44) had a point mutation (G→A at position −28) and insertion of thymidine between positions −20 and −19 of the ampC promoter gene (GenBank accession no. AE000487 ). The single nucleotide insertion of T between positions −19 and −20 created an optimal distance (17 bp) in the Pribnow box for ampC hyperproduction. The other isolate (isolate EC38) had two point mutations (G→A at position −28 and C→T at position +58) and a 2-base (GT) insertion between positions −14 and −15. Although the insertion of GT between positions −14 and −15 may create a new promoter next to the original promoter, cloning of the ampC region with truncated nucleotides of the original −35 region of EC38 failed to verify the hypothesis that a new promoter would be created by such a nucleotide insertion. Instead, multiple start sites for ampC transcription at −1, +1, +2, and +3 were observed in an S1 nuclease protection assay. These results suggest that the RNA polymerase is flexible in the selection of a start site in ampC hypertranscription. In conclusion, nucleotide insertions between the −35 and −10 ampC promoter sequences was the mechanism for the hyperproduction of AmpC β-lactamase and resistance to oxyimino-cephalosporins. The failure of the two patients to respond to treatment with oxyimino-cephalosporins highlights the important role of such a resistance mechanism in the clinical setting.

Influence of teicoplanin MICs on treatment outcomes among patients with teicoplanin-treated methicillin-resistant Staphylococcus aureus bacteraemia: a hospital-based retrospective study

OBJECTIVES Higher vancomycin MIC values (≥1.5 mg/L via Etest) may be associated with vancomycin treatment failure among patients with serious methicillin-resistant Staphylococcus aureus (MRSA) infections. As there were limited similar data for teicoplanin, this retrospective cohort study intended to determine the predictive value of teicoplanin MICs for treatment failure among patients with MRSA bacteraemia. PATIENTS AND METHODS All patients with at least one blood culture positive for MRSA admitted to the hospital between January 2010 and January 2011 were reviewed. Patients with an age ≥18 years and receipt of teicoplanin therapy throughout the course or receipt of <72 h of vancomycin therapy and then teicoplanin for >3 days were enrolled. Teicoplanin Etest(®) MICs and treatment outcomes for MRSA bacteraemia were reviewed to identify the breakpoint of teicoplanin MICs influencing treatment outcomes. RESULTS Of the 101 patients enrolled, 56 had a lower teicoplanin MIC (≤1.5 mg/L) for MRSA and 45 had a higher MIC (>1.5 mg/L) for MRSA. A lower teicoplanin MIC was associated with a favourable outcome [37 (66.1%) versus 13 (28.9%); P<0.001] and a lower rate of bloodstream infection-related mortality [15 (26.8%) versus 22 (48.9%); P=0.022]. Patients with chronic obstructive pulmonary disease, bacteraemic pneumonia or higher Pittsburgh bacteraemia score had an unfavourable outcome (P=0.028, 0.022 and <0.001, respectively). Multivariate analysis showed that teicoplanin MIC >1.5 mg/L, higher Pittsburgh bacteraemia score and bacteraemic pneumonia were independent risk factors for unfavourable outcome. CONCLUSIONS A higher teicoplanin MIC value (>1.5 mg/L) may predict an unfavourable outcome and higher mortality rate among teicoplanin-treated MRSA bacteraemic patients.

Clinical and microbiological characteristics of community-acquired thoracic empyema or complicated parapneumonic effusion caused by Klebsiella pneumoniae in Taiwan

Klebsiella pneumoniae is the major cause of community-acquired pyogenic infections in Taiwan and is becoming an increasing problem in acute thoracic empyema. This study evaluated the clinical and microbiological characteristics of community-acquired thoracic empyema or complicated parapneumonic effusion caused by K. pneumoniae in Taiwanese adults treated during the period 2001–2008 at a tertiary medical center. All clinical isolates were examined for capsular serotypes K1/K2, and pulsed-field gel electrophoresis (PFGE) was performed on strains of the same serotype. K. pneumoniae was the most frequent cause of community-acquired thoracic empyema or complicated parapneumonic effusion. It was associated with high mortality (32.4%) and was an independent risk factor for fatal outcome. Diabetes mellitus, liver cirrhosis, and bronchogenic carcinoma were independent risk factors for K. pneumoniae infection. Serotypes K1 (9/37, 24.3%) and K2 (13/37, 35.1%) were the prevalent strains but did not predispose patients to poor outcome compared with other non-K1/K2 serotypes. There was no major cluster of isolates found among serotype K1/K2 strains. In summary, physicians should be aware of the risk factors for thoracic empyema or complicated parapneumonic effusion caused by K. pneumoniae and the associated high mortality, and monitor these patients more closely.

Methicillin-resistant Staphylococcus aureus and Acinetobacter baumannii on computer interface surfaces of hospital wards and association with clinical isolates.

BackgroundComputer keyboards and mice are potential reservoirs of nosocomial pathogens, but routine disinfection for non-water-proof computer devices is a problem. With better hand hygiene compliance of health-care workers (HCWs), the impact of these potential sources of contamination on clinical infection needs to be clarified.MethodsThis study was conducted in a 1600-bed medical center of southern Taiwan with 47 wards and 282 computers. With education and monitoring program of hand hygiene for HCWs, the average compliance rate was 74% before our surveillance. We investigated the association of methicillin-resistant Staphylococcus aureus (MRSA), Pseudomonas aeruginosa and Acinetobacter baumannii, three leading hospital-acquired pathogens, from ward computer keyboards, mice and from clinical isolates in non-outbreak period by pulsed field gel electrophoresis and antibiogram.ResultsOur results revealed a 17.4% (49/282) contamination rate of these computer devices by S. aureus, Acinetobacter spp. or Pseudomonas spp. The contamination rates of MRSA and A. baumannii in the ward computers were 1.1% and 4.3%, respectively. No P. aeruginosa was isolated. All isolates from computers and clinical specimens at the same ward showed different pulsotypes. However, A. baumannii isolates on two ward computers had the same pulsotype.ConclusionWith good hand hygiene compliance, we found relatively low contamination rates of MRSA, P. aeruginosa and A. baumannii on ward computer interface, and without further contribution to nosocomial infection. Our results suggested no necessity of routine culture surveillance in non-outbreak situation.

Eradication of multidrug-resistant Acinetobacter baumannii from the respiratory tract with inhaled colistin methanesulfonate: a matched case-control study

Repeated isolation of multidrug-resistant Acinetobacter baumannii (MDRAB) from respiratory secretions poses a great challenge for infection control. We conducted a retrospective case-control study to evaluate the efficacy and adverse effect of inhaled colistin methanesulfonate (CMS) in the eradication of MDRAB from the respiratory tract. Patients who were admitted to Taipei Veterans General Hospital between February 2009 and June 2010, had at least two sets of monomicrobial culture of MDRAB from respiratory secretions, and remained in hospital for at least 14 days after the first isolation of MDRAB (index day) were included. Patients who received intravenous CMS were excluded. Patients who received CMS inhalation for ≥ 3 days were selected as cases whereas the controls were matched for age and Acute Physiology and Chronic Health Evaluation II score. Thirty-nine cases and controls were identified. The duration of CMS inhalation was 10.9 ± 3.6 days. The use of inhaled CMS was the only independent factor associated with the eradication of MDRAB within 14 days after the index day (OR 266.33; 95% CI 11.26-6302.18, p <0.001), and shortened the duration of MDRAB recovery from the respiratory tract by 13.3 ± 1.45 days. The adverse effects were similar for both groups. The increase of colistin minimal inhibitory concentrations in the last isolate compared with the index isolate from the same patient did not differ between the two groups. In conclusion, our study demonstrated that inhaled CMS enhanced the eradication of MDRAB from the respiratory tract without significant clinical adverse effect or impact on colistin resistance.

Contribution of outer membrane protein K36 to antimicrobial resistance and virulence in Klebsiella pneumoniae

OBJECTIVES Loss of outer membrane protein (Omp) is commonly encountered in multidrug-resistant Klebsiella pneumoniae. However, little is known about the association between Omp loss and virulence. In the present study, this association was investigated in K. pneumoniae. METHODS An OmpK36-deficient mutant (DeltaOmpK36) was derived from a virulent clinical isolate by targeted gene insertion. Antimicrobial susceptibility was tested by microbroth dilution and disc diffusion. Virulence was assessed by serum resistance, phagocytosis, clearance of viable bacteria in the liver and lethality in mice following inoculation with bacteria. RESULTS Susceptibility tests showed that DeltaOmpK36 contributed to the resistance to cefazolin and cefoxitin but not to resistance to late-generation cephalosporins. In vitro assays demonstrated that loss of OmpK36 decreased the resistance to neutrophil phagocytosis and increased the resistance to serum killing during the first hour of the assay, but did not influence the growth rate when compared with the parental strain. Intraperitoneal injection of similar doses ( approximately 4 x 10(4) cfu) of the parental strain and DeltaOmpK36 led to significantly fewer viable bacteria in the liver 24 h post-inoculation in DeltaOmpK36-inoculated mice. In the mice LD(50) (the bacterial dose that caused 50% death) assay, the parental strain was approximately 100-fold more lethal ( approximately 10(3) cfu) than the DeltaOmpK36 mutant ( approximately 10(5) cfu). CONCLUSIONS Loss of OmpK36 in K. pneumoniae resulted in increased antimicrobial resistance, increased susceptibility to neutrophil phagocytosis, increased resistance to serum killing and reduced virulence.

Emergence of carbapenem-resistant Escherichia coli in Taiwan: resistance due to combined CMY-2 production and porin deficiency.

Abstract Eight pairs of Escherichia Coli isolates with various carbapenem susceptibilities from 8 patients were prospectively collected to study the development of resistance. All carbapenem-resistant E. coli isolates were resistant to all tested β-lactams antibiotics except tigecycline. identical pulsed-field gel electrophoresis (PFGE) patterns were found in carbapenem-susceptible and -resistant isolates but different PFGE patterns occurred among patients. A CMY-2 β-lactamase was found in all E. coli isolates. No previously reported carbapenemase genes were detected. Examination of outer membrane protein (OMP) profiles revealed that OmpA was not found in all isolates, while OmpC and Ompf were lost in carbapenem-resistant isolates. loss of both OmpC and Ompf represents the major mechanism of the development of carbapenem resistance in those patients with CMY-2-producing E. coli infections.