Yin-Ching Chuang

In Vitro and In Vivo Activities of Newer Fluoroquinolones against Vibrio vulnificus

ABSTRACT The MICs of six fluoroquinolones as well as minocycline and cefotaxime for 46 clinical isolates of Vibrio vulnificus were determined by the agar dilution method. All the drugs tested had good activities against all isolates, with the MICs at which 90% of the isolates tested were inhibited (MIC90s) by five of the fluoroquinolones ranging between 0.03 and 0.06 μg/ml. The MIC90 of lomefloxacin, on the other hand, was 0.12 μg/ml. Time-kill studies were conducted with these agents and a clinical strain of V. vulnificus, VV5823. When approximately 5 × 105 CFU of V. vulnificus/ml was incubated with any one of the above-mentioned six fluoroquinolones at concentrations of two times the MIC, there was an inhibitory effect on V. vulnificus that persisted for more than 48 h with no noted regrowth. The efficacies of the fluoroquinolones were further evaluated in vivo in the mouse model of experimental V. vulnificus infection and compared to the efficacy of a combination therapy using cefotaxime plus minocycline. With an inoculum of 1.5 × 107 CFU, 28 (87.5%) of 32 mice in the cefotaxime-minocycline-treated group survived and 29 (91%) of the 32 mice in the moxifloxacin-treated group survived while none of the 32 mice in the control group did. With an inoculum of 3.5 × 107 CFU, the difference in survival rates among groups of 15 mice treated with levofloxacin (13 of 15), moxifloxacin (10 of 15), gatifloxacin (10 of 15), sparfloxacin (11 of 15), ciprofloxacin (12 of 15), or lomefloxacin (10 of 15) was not statistically significant while none of the 15 mice treated with saline survived. We concluded that the newer fluoroquinolones as single agents are as effective as the cefotaxime-minocycline combination in inhibiting V. vulnificus both in vitro and in vivo.

National surveillance study on carbapenem non-susceptible Klebsiella pneumoniae in Taiwan: the emergence and rapid dissemination of KPC-2 carbapenemase

Objectives The global spread and increasing incidence of carbapenem non-susceptible Klebsiella pneumoniae (CnSKP) has made its treatment difficult, increasing the mortality. To establish nationwide data on CnSKP spread and carbapenem-resistance mechanisms, we conducted a national surveillance study in Taiwanese hospitals. Methods We collected 100 and 247 CnSKP isolates in 2010 and 2012, respectively. The tests performed included antibiotic susceptibility tests; detection of carbapenemase, extended-spectrum β-lactamases (ESBL), and AmpC β-lactamases genes; outer membrane porin profiles; and genetic relationship with pulsed-field gel electrophoresis and multilocus sequence type. Results The resistance rate of CnSKP isolates to cefazolin, cefotaxime, cefoxitin, ceftazidime, and ciprofloxacin was over 90%. Susceptibility rate to tigecycline and colistin in 2010 was 91.0% and 83.0%, respectively; in 2012, it was 91.9% and 87.9%, respectively. In 2010, carbapenemase genes were detected in only 6.0% of isolates (4 bla IMP-8 and 2 bla VIM-1). In 2012, carbapenemase genes were detected in 22.3% of isolates (41 bla KPC-2, 7 bla VIM-1, 6 bla IMP-8, and 1 bla NDM-1). More than 95% of isolates exhibited either OmpK35 or OmpK36 porin loss or both. Impermeability due to porin mutation coupled with AmpC β-lactamases or ESBLs were major carbapenem-resistance mechanisms. Among 41 KPC-2-producing K. pneumoniae isolates, all were ST11 with 1 major pulsotype. Conclusions In 2010 and 2012, the major mechanisms of CnSKP in Taiwan were the concomitance of AmpC with OmpK35/36 loss. KPC-2-KP dissemination with the same ST11 were observed in 2012. The emergence and rapid spread of KPC-2-KP is becoming an endemic problem in Taiwan. The identification of NDM-1 K. pneumoniae case is alarming.

Needlestick and sharps injuries among health-care workers in Taiwan

Sharps injuries are a major cause of transmission of hepatitis B and C viruses and human immunodeficiency virus in health-care workers. To determine the yearly incidence and causes of sharps injuries in health-care workers in Taiwan, we conducted a questionnaire survey in a total of 8645 health care workers, including physicians, nurses, laboratory technicians, and cleaners, from teaching hospitals of various sizes. The reported incidence of needlestick and other sharps injuries was 1.30 and 1.21 per person in the past 12 months, respectively. Of most recent episodes of needlestick/sharps injury, 52.0% were caused by ordinary syringe needles, usually in the patient units. The most frequently reported circumstances of needlestick were recapping of needles, and those of sharps injuries were opening of ampoules/vials. Of needles which stuck the health-care workers, 54.8% had been used in patients, 8.2% of whom were known to have hepatitis B or C, syphilis, or human immunodeficiency virus infection. Sharps injuries in health-care workers in Taiwan occur more frequently than generally thought and risks of contracting blood-borne infectious diseases as a result are very high.

Invasive Group A Streptococcal Disease in Taiwan Is Not Associated with the Presence of Streptococcal Pyrogenic Exotoxin Genes

We reviewed the clinical features of 44 patients with invasive group A streptococcal (GAS) disease who were treated at two teaching hospitals in southern Taiwan from 1991 to 1994. Genes encoding streptococcal pyrogenic exotoxin types A (speA), B (speB), C (speC), and F (speF) and serotypes of M1, M6, and M12 were determined by polymerase chain reaction to target specific sequences in the 44 isolates recovered from these patients and in 28 isolates recovered from upper respiratory sites in 28 additional patients during the study period. The protease activity of these isolates was tested by using the casein plate method. Of the 44 patients with invasive diseases, 25 (57%) had no obvious underlying diseases, and 14 (32%) had preexisting neoplastic diseases or had previously used steroids. Twenty-five patients (57%) presented with cellulitis or necrotizing fasciitis, 24 (55%) had bacteremia, and eight (18%) had streptococcal toxic shock syndrome (STSS). Eight patients (18%) died of invasive GAS disease; seven had STSS, and seven had underlying diseases. All eight patients died within 48 hours after hospitalization. The presence of speA, speC, or speF was not implicated in any particular clinical syndrome in patients with invasive GAS disease. High-level protease activity and the M1 serotype of the isolates were significantly associated with the clinical signs of STSS and with mortality. M1 serotype and protease activity, as well as host immune status, might play significant roles in the pathogenesis of invasive GAS disease in Taiwan.

Suppurative Acinetobacter baumanii Thyroiditis with Bacteremic Pneumonia: Case Report and Review

Suppurative thyroiditis is rare, and the major pathogens are Staphylococcus and Streptococcus species. We present a case caused by Acinetobacter baumanii, which has never before been reported. We review another 191 cases from the English-language literature (1980 to April 1997) and make a comparison with a review of 224 cases (1900-1980). As the numbers of immunocompromised patients increase, cases of suppurative thyroiditis are increasing. Pneumocystis carinii has become an important pathogen. Most patients (83.1%) with bacterial infections were euthyroid, whereas those with fungal or mycobacterial infections tended to be hypothyroid (62.5%) and hyperthyroid (50%), respectively.

In vitro efficacy of fosfomycin-containing regimens against methicillin-resistant Staphylococcus aureus in biofilms

OBJECTIVES To compare the in vitro antibacterial efficacy of antistaphylococcal antibiotics in combination with fosfomycin or rifampicin, using a biofilm model. METHODS The antibacterial activities of fusidic acid, linezolid, vancomycin, teicoplanin, rifampicin, minocycline, fosfomycin and tigecycline, individually and in fosfomycin or rifampicin combinations, were measured against planktonic or biofilm-embedded methicillin-resistant Staphylococcus aureus (MRSA) with susceptible and resistant breakpoint concentrations (SBCs and RBCs, respectively), using the MTT-staining method and by counting the number of cfu in the biofilms. RESULTS Linezolid alone at its SBC, and fosfomycin, linezolid, minocycline and tigecycline at their RBCs, exhibited killing effects on biofilm-embedded MRSA (P < 0.0001). Of the eight fosfomycin combinations studied, fosfomycin combined with linezolid, minocycline, vancomycin or teicoplanin at their respective SBCs, exhibited enhanced antibacterial activities (P < 0.0001) when compared with the control group, and outperformed rifampicin combinations (P < 0.01). The killing effects of fosfomycin combinations at their respective RBCs were better than those at their respective SBCs (P < 0.05). Significantly enhanced killing effects were observed with fosfomycin in combination with vancomycin or teicoplanin, compared with vancomycin or teicoplanin alone. For 10 randomly selected MRSA isolates, the results of colony counting in biofilms were comparable with those of the MTT-staining method. CONCLUSIONS Fosfomycin enhanced the activities of linezolid, minocycline, vancomycin and teicoplanin. These combinatorial treatments were even better than rifampicin combination regimens, and may provide therapeutic advantages in catheter-related or prosthetic joint infections.

Mixed Infection in Adult Bacterial Meningitis

Summary12 adult patients suffering from bacterial meningitis caused by mixed infection were identified at Kaohsiung Chang Gung Memorial Hospital over a period of 13 years (1986–1998), and they accounted for 6.5% (12/184) of our culture-proven adult bacterial meningitis. The 12 cases included seven males and five females, aged 17–74 years. Six of the 12 cases had community-acquired infections and the other six had nosocomially-acquired infections. Ten of the 12 cases had associated underlying diseases, with head trauma and/or neurosurgical procedure being the most frequent. Both gram-negative and gram-positive pathogens were identified in these 12 cases with gram-negative pathogens outnumbering the gram-positive ones. The implicated pathogens, starting with the most frequent, included Enterobacter species (Enterobacter cloacae, Enterobacter aerogenes), Klebsiella species (Klebsiella pneumoniae, Klebsiella oxytoca), Escherichia coli, Staphylococcus species (Staphylococcus aureus, Staphylococcus haemolyticus), Pseudomonas aeruginosa, Acinetobacter baumannii, Enterococcus, Serratia marcescens, Citrobacter diversus, Proteus mirabilis, Streptococcus viridans and Neisseria meningitidis. Six of the 12 cases were found to have multi-antibiotic-resistant strains, which included E. cloacae in one, A. baumannii in one, K. pneumoniae in one and S. aureus in three. The management of these 12 cases included appropriate antibiotics and neurosurgical procedures including shunt revision. Despite the complexity of implicated pathogens and the high incidence of emergence of resistant strains, the overall mortality rate (8.3%, 1/12) was not higher than that in adult bacterial meningitis. However, complete recuperation was difficult in adult patients with mixed bacterial meningitis.

KPC-2-encoding plasmids from Escherichia coli and Klebsiella pneumoniae in Taiwan

OBJECTIVES Two plasmids carrying bla(KPC-2) isolated from carbapenem-resistant Escherichia coli (CR-EC) and carbapenem-resistant Klebsiella pneumoniae (CR-KP), respectively, were completely sequenced. The CR-KP strain was selected from an outbreak in 2012, and the CR-EC strain was the first blaKPC-2-carrying E. coli identified in the same carbapenem resistance monitoring programme in Taiwan. METHODS Antimicrobial susceptibility tests, multilocus sequence typing (MLST) and the conjugal transfer of plasmids were performed. Complete sequencing of the plasmids was performed using a shotgun approach. RESULTS The CR-EC and CR-KP strains in this study were determined to be ST410 and ST11, respectively, by MLST. From CR-EC, we identified a 145 kb conjugative plasmid that carries bla(KPC-2), bla(CMY-2), bla(CTX-M-3) and bla(TEM-1). The plasmid is a chimera composed of three regions related to IncI, IncN and RepFIC replicons. From CR-KP, we identified an 86.5 kb plasmid, pKPC-LK30, which carries bla(KPC-2) and bla(SHV-11). The plasmid is very similar to two bla(KPC-2)-carrying IncFII(K) plasmids, but lacks one of the replication origins and cannot conjugate. CONCLUSIONS The differences in cross-species transferability of the two plasmids can be explained by genetic differences between their backbones and could have resulted in the confined bla(KPC-2)-carrying CR-KP outbreak in Taiwan. Plasmid pKPC-LKEc is the first bla(KPC-2)-carrying plasmid identified from CR-EC in Taiwan. With relatively high transferability it should be closely monitored.

The impact of central line insertion bundle on central line-associated bloodstream infection

BackgroundKnowledge about the impact of each central line insertion bundle on central line-associated bloodstream infection (CLABSI) is limited.MethodsA quality-improvement intervention, including education, central venous catheter (CVC) insertion bundle, process and outcome surveillance, have been introduced since March 2013. Outcome surveillances, including CLABSI per 1,000 catheter-days, CLABSI per 1,000 inpatient-days, and catheter utilization rates (days of catheter use divided by total inpatient-days), were measured. As a baseline measurement for a comparison, we retrospectively collected data from March 1, 2012 to December 31, 2012.ResultsDuring this 10-month period, there were a total of 687 CVC insertions, and 627 (91.2%) insertions were performed by intensivists. The rate of CLABSI significantly declined from 1.65 per 1000 catheter-day during the pre-intervention period to 0.65 per 1000 catheter-day post-intervention period (P = 0.039). CLABSI more likely developed in subjects in which a maximal sterile barrier was not used compared with subjects in which it was used (P = 0.03). Moreover, CVC inserted by non-intensivists were more likely to become infected than CVC inserted by intensivists (P = 0.010).ConclusionsThis multidisciplinary infection control intervention, including a central line insertion care bundle, can effectively reduce the rate of CLABSI. The impact of different care bundle varies, and a maximal sterile barrier precaution during catheter insertion is an essential component of the care line insertion bundle.

Efficacy of combination oral antimicrobial agents against biofilm-embedded methicillin-resistant Staphylococcus aureus

BACKGROUND The combination of fusidic acid and rifampicin has a demonstrated synergistic effect against methicillin-resistant Staphylococcus aureus (MRSA), including planktonic and biofilm-related organisms. However, the in vitro efficacy of other combinations of oral anti-MRSA antibiotics in biofilm models has not been established. METHODS The antibacterial activity of fusidic acid, linezolid, rifampicin, and minocycline against 33 biofilm-embedded MRSA isolates in low susceptibility and high resistance breakpoint concentrations was investigated using the 3-[4, 5-dimethyl-2-thiazolyl]-2, 5-diphenyl-2H-tetrazolium-bromide staining method. The compounds were further examined to determine their antibacterial efficacies in combination. The optical density ratio (ODr) was used to evaluate the antibacterial effects of these antibiotics, and the results indicate higher survival rates of MRSA on biofilm. A biofilm-positive phenotype (determined using the crystal violet stain) was defined as an optical density ≥ 0.17 at 492 nm, and strong biofilm formation was defined as an optical density ≥ 1.0. RESULTS One-third of the MRSA isolates demonstrated weak biofilm formation, and two-thirds demonstrated strong biofilm formation. At low concentrations, linezolid alone lowered the ODr to 0.55 and was effective against biofilm-embedded MRSA (p < 0.001). The activity of minocycline was concentration-dependent and more effective against MRSA isolates that demonstrated weak biofilm formation. The effect of minocycline seems to be further enhanced when used in combination with either fusidic acid or linezolid at low concentrations, with the obtained results equal to those obtained with rifampicin-based regimens (p < 0.001). Rifampicin plus minocycline was also effective against MRSA in biofilm. CONCLUSION In comparison with monotherapy, minocycline-based combinations exhibit highly effective bactericidal effects against biofilm-embedded MRSA.