Comparison between Pseudomonas aeruginosa siderophores and desferrioxamine for iron acquisition from ferritin

Background: Siderophore is an iron chelator produced by microorganism. Pseudomonas aeruginosa produces two siderophores (pyoverdin and pyochelin). Desferrioxamine is a siderophore used in thalassemia patients to treat an iron overload of vital organs. Objective: Compare the ability of pyoverdin, pyochelin, and desferrioxamine for iron mobilization from ferritin. Materials and Methods: In vitro experiment, the ability of P. aeruginosa siderophores and desferrioxamine for iron mobilization from ferritin was compared by using a dialysis membrane assay at pH values of 7.4 and 6.0. Stimulation of P. aeruginosa PAO1 growth by all siderophores was studied in glucose minimum medium. Results: All three compounds were capable of iron mobilization at both pHs. At pH 6.0, the most effectiveness compound was desferrioxamine (31.6%), followed by pyoverdin (21.5%) and pyochelin (13.7%) compared on weight basis, each at 10 μg/mL. At equimolar concentration, their activities were desferrioxamine (38.5±1.2%), followed by pyoverdin (32.0±4.8%) and pyochelin (26.7±1.9%), respectively. Conclusion: The most effective compound in iron mobilization from ferritin was desferrioxamine, followed by pyoverdin and pyochelin respectively.

Prevalence of extended-spectrum beta-lactamase and class 1 integron integrase gene intl1 in Escherichia coli from Thai patients and healthy adults.

Among 120 Escherichia coli isolates from Thai patients, 37 and 9 isolates were extended-spectrum beta-lactamase (ESBL) and suspected ESBL producers respectively while 5 E. coli isolates from 120 Thai healthy adults were suspected ESBL producers. Integrase (intl1) gene was detected in 99% of the clinical and 87% of the non-clinical isolates. Among 37 ESBL producers, percent recovery of bla(TEM), bla(CTX-M), bla(SHV) and bla(VEB) was 78%, 78%, 8% and 8%, respectively. Twenty-five isolates of ESBL producers carried both bla(TEM) and bla(CTX-M), 2 isolates carried 3 genes (bla(TEM), blac(CTX-M), and bla(SHV)) and 3 showed no detectable bla gene. Among the 14 suspected ESBL producers, intl1 and bla(TEM) were detected in 13 isolates. ESBL producers from clinical samples were resistant to most of the tested antimicrobial agents compared to non-ESBL producers and isolates from healthy adults with about half of the latter susceptible to all tested antimicrobial agents. Only one clinical isolate was resistant to imipenem. Susceptibility to trimethoprim/sulfamethoxazole among the clinical isolates in ESBL producer group (27%) and non-producer group (33%) were comparable, whereas the percent susceptibility of the non-clinical isolates was about twice that of the clinical isolates.

Antimicrobial susceptibility of Streptococcus pneumoniae isolated from patients with respiratory tract infections in Thailand.

A total of 400 clinical Streptococcus pneumoniae strains from patients with respiratory diseases were collected from January 2002 to December 2005. In this study, an increased prevalence of penicillin-nonsusceptible S. pneumoniae (PNSP) from 63% in 2002-2003 to 69% in 2004-2005 was found. During 2004-2005, 56% were erythromycin-nonsusceptible S. pneumoniae (ENSP) and 54% were both PNSP and ENSP. The PNSP, ENSP and PNSP+ENSP groups showed similar trends, ie, sensitive to amoxicillin/clavulanate (range 97.2-98.5%), levofloxacin (range 90.7-92.4%), ceftriaxone (range 87.1-89.4%), and ofloxacin (range 64.8-66.1%). Lower levels of susceptibility were detected for azithromycin, clarithromycin, cefdinir, cefprozil, clindamycin, co-trimoxazole, chloramphenicol and tetracycline in penicillin and erythromycin-nonsusceptible strains. Of the macrolide-resistant S. pneumoniae, 55% of strains exhibited the M phenotype and 45% the constitutive MLS(B) phenotype. No pneumococci with the inducible MLS(B) phenotype were detected in Thailand.

Preliminary study of randomly-amplified polymorphic DNA analysis for typing extended-spectrum beta-lactamase (ESBL)-producing Klebsiella pneumoniae.

Objective: Extended-spectrum beta-lactamases (ESBLs) are most prevalent in Klebsiella pneumoniae. This organism is frequently isolated from clinical specimens and can cause septicemia, pneumonia or urinary tract infection. There were occasionally suspicious outbreaks of ESBL-producing K. pneumoniae in patients' wards. The objective is to determine whether the randomly amplified polymorphic DNA (RAPD), which is a polymerase chain reaction (PCR)-based typing technique, can be used as a typing method for studying the molecular epidemiology of ESBL-producing K. pneumoniae. MATERIAL AND METHOD: The present study was carried out by using 30 ESBL-producing K. pneumoniae isolates obtained from different patients admitted to Siriraj Hospital between January and February 2004. RAPD was evaluated for three primers. All isolates were re-examined by using Southern blot hybridization. RESULTS: It was found that 29 DNA band patterns were generated individually by either AP4 or HLWL74 and R108 primers (30 patterns) for RAPD analysis and 30 patterns for Southern blot hybridization with class 1 integron (intI1) probe. Different patterns indicated that these 30 isolates could not be the cause of an outbreak in Siriraj Hospital. CONCLUSION: The RAPD typing is good and can be used as a screening, rapid and inexpensive'test for ESBL-producing K. pneumoniae during investigation of outbreaks.

Bartonella henselae: first reported isolate in a human in Thailand.

This is the first reported case of bacillary angiomatosis associated with Bartonella henselae in Thailand. The clinical, pathological, and microbiological findings are presented. The bacterium was isolated from a biopsy of skin lesions obtained on admission and identified by cellular morphology, characteristics of colonies on chocolate agar, extensive biochemical tests and 16S ribosomal DNA sequencing.

Roseomonas gilardii subsp rosea, a pink bacterium associated with bacteremia: the first case in Thailand.

Roseomonas is a pink-pigmented, non-fermentative, gram-negative coccobacillus bacterium. Human infections caused by Roseomonas are very rare. We report the first case of bacteremia associated with Roseomonas gilardii subsp rosea in Thailand. The bacterium was isolated from blood culture and identified by cellular morphology, characteristics of colonies on blood agar, extensive biochemical tests and 16S ribosomal DNA sequencing.

Five-year study of antimicrobial susceptibility and beta-lactamase production in Haemophilus influenzae.

We evaluated 582 Haemophilus influenzae isolates from patients between January 2000 and December 2004. Overall, 433 isolates were obtained from sputum and bronchial washings, 124 isolates were from pus, 19 isolates were from blood and 6 isolates form cerebrospinal fluid. H. influenzae was sensitive to amoxicillin/clavulanate, ampicillin/sulbactam, gentamicin, cefuroxime, ceftriaxone, cefotaxime, ciprofloxacin, ofloxacin, imipenem, meropenem (range 97-100%), chloramphenicol (75%), ampicillin/amoxicillin (52%), but resistant to trimethoprim-sulphamethoxazole. As for beta-lactamase production, 48.4% of the isolates tested were positive.

A surveillance study of bacteriologic profile in rhinosinusitis.

Objective: To review the types of bacteria found in rhinosinusitis and the prevalence of a beta-lactamase producing organism in a tertiary care hospital during the year 2004 and compared with our previous reports. Methods: Charts of patients who underwent endoscopic sinus surgery or maxillary antral puncture or endoscopic-guided culture at the Rhinology & Allergy Division, Department of Otolaryngology and the Department of Microbiology, Siriraj Hospital from January 2004 to December 2004 were reviewed. Information regarding the patient’s age, site of specimens, culture and sensitivity results were obtained. Results: There were 162 specimens and 29 bacterial species isolated. There were 50.4% positive aerobic cultures, gram-negative bacteria were more common than gram-positive bacteria (68.5% vs 31.5%). Common aerobes were Pseudomonas aeruginosa (16.2%), non-fermentative gram negative rod: NF-GNR (10.8%), Coagulase- negative Staphylococcus aureus :CNS (9.9%) and Klebsiella pneumoniae (9.9%).The most common anaerobes were Peptostreptococcus sp., Bacteroides fragilis and Fusobacterium sp. Conclusion: Contrary to our previous studies, gram negative organisms play a more important role than gram positive organisms. The causative pathogens of rhinosinusitis should be studied continuously because rapid progress in the development of new antimicrobial agents has a significant impact on their bacteriologic profile.

Epidemiology of Staphylococcus aureus infections and the prevalence of infection caused by community-acquired methicillin-resistant Staphylococcus aureus in hospitalized patients at Siriraj Hospital.

BACKGROUND: The CA-MRSA infections have emerged in many parts of the world over the past decade. To our knowledge, the prevalence of CA-MRSA infections in Thai patients is unknown. OBJECTIVE: To determine an epidemiology of Staphylococcus aureus (S. aureus) infections in hospitalized patients in Siriraj Hospital and the prevalence of infections caused by community-acquired methicillin-resistant S. aureus (CA-MRSA). MATERIAL AND METHOD: The study was carried out at Siriraj Hospital from January to May 2005. The eligible patients were hospitalized patients whom S. aureus were isolated from their clinical specimens submitted to Department of Microbiology. S. aureus isolate was classified into infection or colonization. S. aureus infections were further classified into methicillin-resistant S. aureus (MRSA) or methicillin-sensitive S. aureus (MSSA) infections, and hospital-acquired (HA) or community-acquired (CA) infections. CA-MRSA infection is defined as infection caused by MRSA isolated from the patient within 72-hour of hospitalization and has no features of HA MRSA infections. RESULTS: There were 669 S. aureus isolates from 448 patients. Two hundred and sixty two patients (58.5%) were MSSA whereas 186 (41.5%) were MRSA infections. CA-MRSA was found in three isolates (0.9% of total MRSA) from two patients. CONCLUSION: The prevalence of CA-MRSA infections in hospitalized patients in Siriraj Hospital was uncommon and these patients could probably be HA MRSA infections.

Respiratory tract infection caused by bacteria (non-Mycobacterium) and their antibiogram in HIV-positive patients.

Abstract. This study was undertaken from 1995-2000 to investigate the cause of respiratory tract infection among 481 patients with human immunodeficiency virus (HIV) at Siriraj Hospital, Bangkok, Thailand. The positive rate of bacterial pathogens was 38.46%. Pseudomonas aeruginosa appeared to be the most common pathogen (32.97%), followed by Staphylococcus aureus (18.92%), Klebsiella pneumoniae (10.81 %), Haemophilus influenzae (7.57%), and Acinetobacter baumannii (5.95%). P. aeruginosa was sensitive to netilmycin, amikacin, imipenem, meropenem, cefoperazone/sulbactam, piperacillin/tazobactam, and gentamicin (67-84%). S. aureus was sensitive to vancomycin and teicoplanin (100%).

Bacteremia and antimicrobial susceptibilities in HIV-infected patients at Siriraj Hospital.

Bacterial infections in human immunodeficiency virus (HIV) infected patients may frequently develop into septicemia. Our study evaluated the bacterial pathogens isolated from hemocultures of HIV-infected patients at Siriraj Hospital and their antimicrobial susceptibility tests. The percentages of positive hemocultures were 24.64, 21.38, 23.88, and 28.46% in 1996, 1997, 1998, and 1999, respectively. Salmonella spp was the most pathogen isolated, followed by Escherichia coil (10.93%), Staphylococcus aureus (8.2%), coagulase-negative staphylococci (6.56%), nonfermentative gram-negative rods (6.01%), Pseudomonas aeruginosa (5.46%), Klebsiella pneumoniae (4.37%), and Enterobacter spp (4.37%). Salmonella, serogroup C was the most frequently isolated serogroup. It was sensitive to amoxicillin/clavulanate in 100%, ampicillin/sulbactam in 89%, cefazolin, cefuroxime, cefotaxime, ceftriaxone, ceftazidime, imipenem, gentamicin, amikacin, netilmycin, ofloxacin, and ciprofloxacin in 100%. The changing spectrum of bacteria and antimicrobial susceptibility patterns in HIV-1 infected patients may provide a guideline for the selection of appropriate drugs for treatment.

Salmonella meningitis and antimicrobial susceptibilities.

Meningitis caused by Salmonella species is not uncommon in many developing countries. Patients suspected of bacterial meningitis who were admitted to Siriraj Hospital were enrolled in this study during 1986-2001. There were only 19 cases of Salmonella meningitis. Salmonella serogroup D ranked first, followed by serogroup C, serogroup B and then serogroup H. Most patients were children under 1 year of age. The antimicrobial susceptibility pattern for Salmonella meningitis may provide a guideline for the selection of appropriate drug treatment.

Prevalence and antimicrobial susceptibility of Pseudomonas aeruginosa mucoid and non-mucoid type.

Pseudomonas aeruginosa is a leading cause of nosocomial infections. One thousand two hundred and twenty strains of mucoid and non-mucoid types of P. aeruginosa isolated from different patients were examined at Siriraj Hospital from January 2001-October 2003. The prevalences of P. aeruginosa mucoid type and non-mucoid type were 3.6% and 96.4%, respectively. Susceptibility testing was performed by Kirby-Bauer disk diffusion method as recommended by NCCLS. The isolates with mucoid phenotypes were more susceptible than the non-mucoid isolates. The antimicrobial susceptibility pattern of both types should provide guidelines for the selection of appropriate drugs for treatment.

Bacterial isolation and antimicrobial susceptibilities in patients with infective endocarditis.

Infective endocarditis is life-threatening and urgent treatment is needed. We review here 6217 patients with infective endocarditis admitted to Siriraj Hospital during a 20 year period, 1982-2001. In this retrospective study, we obtained our data from hemoculture results. Bacterial pathogens were found in only 834 patients (13.41%). Of the five most common pathogens, nonfermentative gram-negative rods (N.F.) ranked first (20.94%), followed by coagulase-negative staphylococci (12.47%), viridans streptococci (10.23%), Staphylococcus aureus (9.29%), and Escherichia coli (8.59%). Of the N.F., the sensitivities were: cefoperazone/sulbactam (86%), piperacillin/tazobactam (86%), meropenem (84%), imipenem (83%), ceftazidime (78%), ofloxacin (85%), ciprofloxacin (71%), and co-trimoxazole (71%).

Six-year report of mycobacteria recovered from automated culture system at Siriraj Hospital.

An increased incidence of tuberculosis and other mycobacterial infections among immunocompromised patients has created a serious health crisis, especially in resource-poor countries. In addition, disseminated disease occurs more frequently in these patients. Rapid isolation and accurate identification of causative agents are necessary for selecting an appropriate treatment regimen. Since an isolation of Mycobacterium tuberculosis and slowly growing mycobacteria require 3-4 weeks for conventional culture, the automated system can reduce the detection time to 7-10 days. The present study demonstrated the mycobacteria recovered from hemocultures and other sterile body fluids, using the BACTEC 9000 system. Overall, 5,490 samples during the period 1998-2003 were submitted for hemocuture and the isolated mycobacteria were identified by using molecular techniques, like multiplex PCR and PCR-REA. The results demonstrated that~18-28% of hemocultures were positive for mycobacteria. Of these, M. tuberculosis appeared to be the most common species among mycobacteria isolates whereas the M. avium complex was found to be the second most common. The combined use of an automated culture system and molecular techniques as shown in this study is a useful procedure for rapid isolation and identification of mycobacteria that can reduce the time from 6-8 weeks to 2-3 weeks.

Serological study of Mycoplasma pneumoniae infections.

Mycoplasma pneumoniae antibody was determined in 811 sera of different patients admitted to Siriraj Hospital with respiratory tract infection from July 1, 2000 to August 31, 2003 by agglutination with gelatin particle agglutination test kit (SERODIA-MYCO II, Fujirebio Inc. Japan) in microtiter plates. Three hundred and three sera were positive (37.36%). The five most positive titer were found in patients 5-9 yr (40.26%), followed by patients 1-4 yr (24.75%), 10-14 yr (19.80%), 30-39 yr (5.28%) and 20-29 yr (3.96%). The positive titers ranged from 40 to > 20,480. Female:male ratio in positive patients was approximately the same (1.19:1). High titers (> or = 320) were found in 146 out of 303 patients (48.18%). The infection was mostly found in children aged 5-9 yr. Detection of antibody to M. pneumoniae infection showed that 37.36% of patients who were suspected of having atypical bacterial pneumonia were positive.

Pulmonary rhodococcosis an unrecognized pulmonary infection in AIDS patients.

Pulmonary rhodococcosis is an uncommon pulmonary infection in human beings, but the case reports have been increasing in HIV-infected patients. We report a female AIDS patient presenting with fever, productive cough and weight loss over 6 weeks. Chest x-ray showed a cavitary lesion with air fluid level in the right upper lobe infiltration. Sputa for AFB stain were negative for 3 consecutive days. Fiberoptic bronchoscopy was performed and bronchoalveolar lavage fluid was examined. It showed a gram-positive, weakly acid-fast coccobacilli. The culture grew only Rhodococcus equi. She was treated with erythromycin and rifampin and responded well.