Antimicrobial Resistance of Clinically Important Bacteria Isolated from 12 Hospitals in Korea in 2005 and 2006 / 대한임상미생물학회지

BACKGROUND: Emergence and spread of antimicrobial resistant bacteria make it difficult to treat infections. A rapid increase in antimicrobial-resistant bacteria has become a serious problem in many countries including Korea, and it is important to perform a nationwide study of antimicrobial resistance to obtain some basic data that will help solve these problems. The aim of this study was to determine the nationwide prevalence of resistance among frequently isolated bacterial pathogens in 2005 and 2006 in Korea. METHODS: We collected routine susceptibility data for medically important bacterial pathogens from 12 university and general hospital laboratories in Korea from April to September in 2005 and from January to June in 2006. Collected data was analyzed by patient group. RESULTS: The proportions of methicillin-resistant Staphylococcus aureus (MRSA) were 65% in 2005 and 72% in 2006, respectively. The resistance rates of Enterococcus faecium to vancomycin were 29% in 2005 and 24% in 2006. The non-susceptible rates of Streptococcus pneumoniae to penicillin were 68% in 2005 and 74% in 2006. The resistant rates of Escherichia coli and Klebsiella pneumoniae to the 3rd generation cephalosporin were 10~12% and 25~39%, respectively, in 2005 and 11~15% and 30~34% in 2006. In Citrobacter freundii, Enterobacter cloacae and Serratia marcescens, the resistance rates to 3rd generation cephalosporin were 23~31%, 32~34%, and 17~27%, respectively, in 2005 and 21~37%, 37~43%, and 13~31% in 2006. The resistance rates to imipenem and meropenem were 21% and 18%, respectively, in Pseudomonas aeruginosa and 18% and 25% in Acinetobacter baumannii in 2005; 29% and 20% in P. aeruginosa and 18% and 23% in A. baumannii in 2006. Cotrimoxazole and levofloxacin resistance rates of Stenotrophomonas maltophilia were 5% and 13%, respectively, in 2005 and 3% and 7% in 2006. There were no isolates resistant to 3rd generation cephalosporin and fluoroquinolone among non-typhoidal Salmonella in 2005. CONCLUSION: Antimicrobial resistance of medically important bacteria is still a serious problem in Korea. To manage the problem, a continuous nationwide surveillance and diversified investigation and effort have become more important.

Once-daily Dosing of Arbekacin Can Suppress the Formation of Small Colony Variants of Methicillin Resistant Staphylococcus aureus in an in vitro Pharmacodynamic Infection Model

BACKGROUND: Small colony variants (SCVs) of Staphylococcus aureus have emerged to be commonly associated with persistent and relapsing infections. Arbekacin (ABK) is one of a few alternatives to vancomycin in intractable case of methicillin resistant S. aureus (MRSA) infection. However, it has not yet been defined whethter ABK tends to be efficacious to the MRSA SCVs. In this study, we employed an in vitro pharmacodynamic infection model (IVPDIM) to define efficacies of ABK against MRSA SCVs. MATERIALS AND METHODS: Using four strains of clinically isolated MRSA (MRSA122, MRSA160, MRSA18, MRSA123), we adopted IVPDIM comprised of two-compartment in which effective surface-to-volume ratio of 5.34 cm(-1). Human pharmacokinetic regimen simulations of ABK were as follows: 100 mg every 12 h (q12h), 200 mg q24h, 200 mg q12h, and 400 mg q24h. Samples were taken from each model at 0, 1, 2, 4, 6, 12, 24, and 30 h, and the bacterial colony counts were determined. The experiments were repeated twice with ABK-administered groups and control group. RESULTS: MICs of ABK for MRSA122, MRSA160, MRSA18, and MRSA123 were 2, 2, 2, and 1 microgram/mL, respectively. In case of MRSA122, MRSA160, MRSA18, C(max)/MIC were less than 9.0 except for ABK 400 mg q24h regimen. In MRSA123, C(max)/MIC were 8.9 on average at ABK 100 mg q12h regimen. But, other regimen showed C(max)/MIC >9. Four regimens for 4 strains showed statistically different colony counts at 30 h (P=0.000). The more dosage or less frequent dosing interval, the more colonies tended to reduce in all strains. In 100 mg q12h groups, SCVs were observed in all strains within 24 h. With increment of dosage or changing dosing interval from q12h to 24h, SCVs were reduced (P=0.000). Regimen of 400 mg q24h did not let SCVs appear in all strains of MIC 2 microgram/mL during the experiments. CONCLUSION: SCVs were observed when MIC of ABK against MRSA were 1-2 microgram/mL, especially in most cases of C(max)/MIC <9. Those findings were also associated with re-growth of colony during the experiments. Once-daily dosing of ABK could reduce or eliminate the appearance of SCV.

Once-daily Dosing of Arbekacin Can Suppress the Formation of Small Colony Variants of Methicillin Resistant Staphylococcus aureus in an in vitro Pharmacodynamic Infection Model

BACKGROUND: Small colony variants (SCVs) of Staphylococcus aureus have emerged to be commonly associated with persistent and relapsing infections. Arbekacin (ABK) is one of a few alternatives to vancomycin in intractable case of methicillin resistant S. aureus (MRSA) infection. However, it has not yet been defined whethter ABK tends to be efficacious to the MRSA SCVs. In this study, we employed an in vitro pharmacodynamic infection model (IVPDIM) to define efficacies of ABK against MRSA SCVs. MATERIALS AND METHODS: Using four strains of clinically isolated MRSA (MRSA122, MRSA160, MRSA18, MRSA123), we adopted IVPDIM comprised of two-compartment in which effective surface-to-volume ratio of 5.34 cm(-1). Human pharmacokinetic regimen simulations of ABK were as follows: 100 mg every 12 h (q12h), 200 mg q24h, 200 mg q12h, and 400 mg q24h. Samples were taken from each model at 0, 1, 2, 4, 6, 12, 24, and 30 h, and the bacterial colony counts were determined. The experiments were repeated twice with ABK-administered groups and control group. RESULTS: MICs of ABK for MRSA122, MRSA160, MRSA18, and MRSA123 were 2, 2, 2, and 1 microgram/mL, respectively. In case of MRSA122, MRSA160, MRSA18, C(max)/MIC were less than 9.0 except for ABK 400 mg q24h regimen. In MRSA123, C(max)/MIC were 8.9 on average at ABK 100 mg q12h regimen. But, other regimen showed C(max)/MIC >9. Four regimens for 4 strains showed statistically different colony counts at 30 h (P=0.000). The more dosage or less frequent dosing interval, the more colonies tended to reduce in all strains. In 100 mg q12h groups, SCVs were observed in all strains within 24 h. With increment of dosage or changing dosing interval from q12h to 24h, SCVs were reduced (P=0.000). Regimen of 400 mg q24h did not let SCVs appear in all strains of MIC 2 microgram/mL during the experiments. CONCLUSION: SCVs were observed when MIC of ABK against MRSA were 1-2 microgram/mL, especially in most cases of C(max)/MIC <9. Those findings were also associated with re-growth of colony during the experiments. Once-daily dosing of ABK could reduce or eliminate the appearance of SCV.

Emergence of CTX-M-12, PER-1 and OXA-30 beta-Lactamase-Producing Klebsiella pneumoniae / 대한임상미생물학회지

BACKGROUND: The aim of this study was to determine a nation-wide prevalence of Ambler class A and D extended-spectrum-lactamases (ESBL) in Klebsiella pneumoniae isolates in Korea. METHODS: During the period of April to May 2005, 189 isolates of K.pneumoniae were collected from 11 Korean hospitals. Antimicrobial susceptibilities to ceftazidime and cefotaxime were tested by the disk diffusion method, and ESBL production was determined by double-disk synergy test. Determinants of ceftazidime or cefotaxime-resistance were transferred to Escherichia coli J53 (azide-resistant) by transconjugation. Genotypes of class A and D ESBL genes were determined by PCR amplification and sequencing. RESULTS: One hundred-sixty isolates of K.pneumoniae showed positive results in double-disk synergy test. The most prevalent ESBL was SHV-12 (n=148). Also detected were genes encoding ESBLs including TEM-52 (n=1), SHV-2a (n=2), CTX-M-3 (n=15), CTX-M-9 (n=6), CTX-M-12 (n=2), CTX-M-14 (n=9), CTX-M-15 (n=1), PER-1 (n=1), GES-5 (n=3), and OXA-30 (n=2) beta-lactamases. CONCLUSION: With the emergence of CTX-M-12, PER-1, and OXA-30 beta-lactamases, the ESBLs in K.pneumoniae isolates are becoming more diverse in Korea.

Emergence of CTX-M-12 and A Novel CTX-M Type Extended-Spectrum beta-Lactamaseproducing Klebsiella pneumoniae / 대한진단검사의학회지

BACKGROUND: The aims of this study were to survey the nation-wide susceptibilities of Klebsiella pneumoniae isolates against ceftazidime and cefotaxime and to determine the prevalence of class A extended-spectrum beta-lactamases (ESBLs). METHODS: During the period of February to July 2004, K. pneumoniae isolates intermediate or resistant to ceftazidime and/or cefotaxime were collected from 12 hospitals in Korea. Antimicrobial susceptibilities were determined by the disk diffusion and the agar dilution methods and ESBL-production was by double-disk synergy test. Ceftazidime or cefotaxime-resistance determinants of the ESBLproducers were transfered to Escherichia coli J53 by transconjugation. Searches for class A ESBL genes were performed by PCR amplication. RESULTS: Among 212 clinical K. pneumoniae isolates, 172 (81%) isolates showed positive results in double-disk synergy test; the most prevalent ESBL was SHV-12 (n=104). Genes encoding ESBLs including SHV-2 (n=6), SHV-2a (n=17), CTX-M-3 (n=18), CTX-M-9 (n=6), CTX-M-12 (n=1), CTX-M- 14 (n=27), CTX-M-15 (n=3), and a novel CTX-M-type beta-lactamases were also detected. CONCLUSIONS: It is concluded that diversity of ESBLs in K. pneumoniae isolates are increasing in Korea. CTX-M-12 has never been reported in Asia, and a novel CTX-M-type ESBL has emerged.

Mechanism of VanB Phenotype in Vancomycin-Resistant Enterococci carrying vanA gene / 대한진단검사의학회지

BACKGROUND: Recently, vancomycin-resistant enterococci (VRE) with the vanA genotype that are susceptible to teicoplanin have been described in Japan, Taiwan, and Korea. The investigators suggested three point mutations in the putative sensor domain of vanS or impairment of accessory proteins VanY and VanZ as an explanation for the VanB phenotype-vanA genotype VRE. In this study, we analyzed Tn1546-like elements to determine the molecular mechanisms responsible for the impaired glycopeptide resistance of clinical VRE isolates with VanB phenotype-vanA genotype from Korea. METHODS: From 2001 to 2004, 28 clinical isolates of Enterococcus faecium with VanB phenotypevanA genotype were collected from 8 different university hospitals in diverse geographic areas in Korea. For structural analysis of Tn1546-like elements, PCR amplifications for internal regions of Tn1546 were performed. The purified PCR products were directly sequenced with an ABI Prism 3100 DNA sequencer. RESULTS: The sequence data of the vanS regulatory gene revealed that none of the isolates had any point mutations in this gene. All 28 isolates had a complete or incomplete deletion of vanY gene. Of these, 13 strains represented a complete deletion of vanZ, and 2 strains showed the deletion of nucleotides near the end point of vanX. CONCLUSIONS: The mechanism of VanB phenotype-vanA genotype in VRE isolates from Korea is not point mutations of vanS but the rearrangements of vanX, vanY and vanZ.

Prevalence of Ambler Class A Extended-Spectrum beta-Lactamase-Producing Escherichia coli and Klebsiella pneumoniae Isolates in Korea / 대한임상미생물학회지

BACKGROUND: The aim of this study is to determine the nationwide prevalence of Ambler class A extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli and Klebsiella pneumoniae and to characterize genotypes of ESBLs. METHODS: During the period of February through July, 2003, E.coli and K.pneumoniae isolates were collected from 12 hospitals in Korea. Antimicrobial susceptibilities were tested by disk diffusion method, and ESBL-production was determined by the double-disk synergy test. MICs of beta-lactam antibiotics were tested by agar dilution method. Searches for bla TEM, bla SHV, bla CTX-M, bla PER-1, bla VEB, bla IBC, bla GES and bla TLA genes were performed by PCR amplification, and the genotypes of ESBLs were determined by direct nucleotide sequence analysis of amplified products. RESULTS: Resistance rates of E.coli (n=246) and K.pneumoniae (n=239) isolates to ceftazidime were 8.5% and 20.1%, respectively. Most prevalent Ambler class A ESBL genotypes in E.coli isolates were bla CTX-M-15 (n=4) and bla CTX-M-3 (n=3), and each of bla CTX-M-14, bla SHV-12, and bla TEM-52 gene was also found in one isolate. Most prevalent ESBL genotypes in K.pneumoniae were bla SHV-12 (n=30) and bla CTX-M-3 (n=13), and bla CTX-M-14 (n=5). bla SHV-2a (n=3), bla SHV-5 (n=2), bla TEM-52 (n=1), bla GES-3 (n=2) genes were also found. CONCLUSION: CTX-M-type ESBL-producing E.coli and K.pneumoniae isolates are spreading, and a GES-type ESBL has emerged in Korea.

Antimicrobial Resistance of Clinically Important Bacteria Isolated from 12 Hospitals in Korea in 2004 / 대한임상미생물학회지

BACKGROUND: A rapid increase in antimicrobial-resistant bacteria has become a serious problem in many countries including Korea, but the rate and pattern of antimicrobial resistance may vary significantly depending on countries and even on hospitals. The aim of this study was to determine the nationwide prevalence of resistance among frequently isolated bacterial pathogens in Korea. METHODS: Routine susceptibility data for medically important bacterial pathogens from 12 university hospital and general hospital laboratories in Korea were analysed by patient group. These pathogens had been isolated during the period from April to November in 2004. RESULTS: The proportion of methicillin-resistant Staphylococcus aureus (MRSA) was 67%. Van-comycin-resistance rate of Enterococcus faecalis was 1% and that of E.faecium was 20%. The resistance rates of Streptococcus pneumoniae to penicillin and Haemophilus influenzae to ampicillin were 70% and 54%, respectively. The resistant rates of Escherichia coli and Klebsiella pneumoniae were 7-10% and 26-31% to the 3rd generation cephalosporin, respectively. The resistance rates to 3rd generation cephalosporin were 22-30% in Citrobacter freundii, 35-44% in Enterobacter cloacae and 15-22 % in Serratia marcescens. Imipenem resistance rates of Pseudomonas aeruginosa and Acinetobacter baumannii were 26% and 17%. Cotrimoxazole and levofloxacin resistance rates of Stenotrophomonas maltophilia were 46% and 44%, respectively. CONCLUSION: Antimicrobial resistance rates of clinically important pathogens in Korea were still high and were generally higher among the bacteria isolated from the intensive care unit patients. Strict infection control and continuous nationwide surveillance program will be required to manage the antimicrobial resistance problem.

Dissemination of CTX-M Type Extended-Spectrum beta-Lactamases and Emergence of CTX-M-12 in Escherichia coli / 대한진단검사의학회지

BACKGROUND: Clinical isolates of Escherichia coli were evaluated to determine the prevalence and genotypes of Ambler class A extended-spectrum beta -lactamases (ESBLs). METHODS: Clinical isolates of E. coli were collected from 12 hospitals from February through July, 2004. Antimicrobial susceptibility was tested by disk diffusion and agar dilution methods, and ESBLproduction was determined by double-disk synergy test. TEM, SHV, CTX-M, PER-1, VEB, IBC, GES, and TLA type ESBL genes were detected by PCR amplifications, and the PCR products were subjected to direct sequencing. RESULTS: The double-disk synergy test was positive in 90.9% (149 in 164) of the ceftazidime- or cefotaxime-resistant E. coli isolates. The most prevalent types of Ambler class A ESBLs in E. coliisolates were CTX-M-15 (n=53). CTX-M-14 (n=24), CTX-M-3 (n=9), CTX-M-9 (n=3), CTX-M-12 (n=3), SHV-2a (n=1), SHV-12 (n=5) and TEM-52 (n=3) were also found. CTX-M-12 ESBL had never been reported before in Korea. CONCLUSIONS: CTX-M type ESBL-producing E. coli isolates are spreading and CTX-M-12 is emerging in Korea.

Antimicrobial Resistance of Clinically Important Bacteria Isolated from 12 Hospitals in Korea / 대한임상미생물학회지

BACKGROUND: A rapid increase in antimicrobial-resistant bacteria has become a serious problem in Korea. Moreover, the antibiotic resistance problem has worsened noticeably during the past several years. The aim of this study was to determine the prevalence of resistance among frequently isolated gram-positive and -negative bacteria in Korea. METHODS: Routine susceptibility data for medically important bacteria isolated during 6 months of 2003 were collected from 12 university and general hospital laboratories in Korea. RESULTS: The proportion of methicillin-resistant Staphylococcus aureus (MRSA) was 66%; however, vancomycin-resistant strains were not detected. The rates of vancomycin-resistant Enterococcus faecium and penicillin-nonsusceptible Streptococcus pneumoniae (PNSP) were 22% and 73%, respectively. The resistance rates to 3rd generation cephalosporins and monobactam were: Escherichia coli 8-12%, Klebsiella pneumoniae 18-22%, Citrobacter freundii 22-32%, Enterobacter cloacae 34-37%, and Serratia marcescens 12-21%, respectively. Imipenem resistance rates of Acinetobacter baumannii and Pseudomonas aeruginosa were 23% and 25%, respectively. CONCLUSIONS: Antimicrobial resistant strains were already prevalent among the clinically important isolates, especially, MRSA, PNSP, and extended-spectrum cephalosporin resistant gram-negative bacilli in Korea. The imipenem-resistant rates of A. baumannii and P. aeruginosa increased, respectively, from 13% and 20% in 2002 to 23% and 25% in 2003. The results of this study will provide a basis for proper treatment of bacterial infections and prevention of spread of resistant bacteria. A continuous nationwide surveillance of antimicrobial resistance is very important and should be performed.

Prevalence of CTX-M-type Extended-Spectrum beta-Lactamase-Producing Escherichia coli and Klebsiella pneumoniae Isolates in Korea, 2003 / 대한임상미생물학회지

BACKGROUND: The aims of this study were to survey nationwide susceptibilities of Escherichia coli and Klebsiella pneumoniae isolates against cefotaxime and to determine the prevalences of CTX-Mtype extended-spectrum beta-lactamases(ESBLs). METHODS: During the period of February to July, 2003, E. coli and K. pneumoniae isolates were collected from 12 hospitals. Antimicrobial susceptibilities to cefotaxime were tested by the disk diffusion method. ESBL production was determined by the double disk synergy test. Cefotaxime-resistance of the ESBL-producers was transfered to E. coli DH5alphaand E. coli Top10-F by transformation. MICs of beta-lactam antibiotics were determined by the agar dilution method. Searches for blaCTX-M genes was performed by PCR amplication; pIs of beta-lactamases were determined by isoelectric focusing. RESULTS: Among 230 isolates of E. coli and 232 isolates of K. pneumoniae, 27 (11.7%) and 79 (34.1%) were intermediate or resistant to cefotaxime, respectively. Twenty-four (10.4%) isolates of E. coli and 58 (25.0%) K. pneumoniae isolates showed positive results in the double disk synergy test. Three isolates of E. coli and 13 K. pneumoniae isolates harbored blaCTX-M-3 gene, 4 E. coli isolates harbored blaCTX-M-15 gene, and 1 E. coli and 5 K. pneumoniae isolates harbored blaCTX-M-14 gene. CONCLUSION: E. coli and K. pneumoniae isolates producing CTX-M-type ESBLs were not uncommon in Korean hospitals. It is thought that periodical surveys are necessary for inspecting the spread of CTX-M-type ESBL genes are necessary.

Antimicrobial Resistance of Clinically Important Bacteria Isolated from Hospitals Located in Representative Provinces of Korea / 대한임상미생물학회지

BACKGROUND: A rapid increase of antimicrobial-resistant bacteria has become a serious problem in many countries. The aim of this study was to determine the prevalence of resistance among frequently isolated gram-positive and -negative bacteria in Korea. METHODS: Data of routine antimicrobial susceptibility test for medically important bacteria, isolated during 3 months of 2002, were collected from 12 university and 1 commercial laboratories in Korea. RESULTS: The proportions of methicillin-resistant Staphylococcus aureus (MRSA) were 60-88%, but vancomycin-resistant S. aureus was not detected. Among the Enterococcus faecium isolates, the resistance rate to vancomycin was 29%. The resistance rates of Escherichia coli and Klebsiella pneumoniae: 11% and 24% to cefotaxime, respectively, and 12% and 21% to cefoxitin, respectively. The resistance rates of Citrobacter freundii, Enterobacter cloacae, and Serratia marcescens: 28%, 34% and 21% to cefotaxime, respectively, <1%, 8% and 14% to cefepime, respectively. The resistance rates of Acinetobacter baumannii and Pseudomonas aeruginosa were: 65% and 37% to piperacillin, 64% and 19% to ceftazidime, 13% and 20% to imipenem, respectively. The resistant rates varied according to the hospital size. The resistance rates were generally higher among the isolates in the hospitals with more than 1,000 beds. The rates of penicillin-nonsusceptible Streptococcus pneumoniae were 58-90%. Among the Haemophilus influenzae isolates, 55-68% were resistant to ampicillin. CONCLUSIONS: Antimicrobial resistant strains were prevalent among the medically important clinical isolates, especially, MRSA, vancomycin-resistant enterococci, extended-spectrum -lactamase- or AmpC -lactamase-producing E. coli and K. pneumoniae, third generation cephalosporin-resistant C. freundii, E. cloacae and S. marcescens, imipenem-resistant A. baumannii and P. aeruginosa, penicillin-nonsusceptible S. pneumoniae and ampicillin-resistant H. influenzae. The antimicrobial resistance has become a serious problem in Korea.

A Comparison of the Sebum excretion rate and the Density of Propionibacterium acnes between Adult acne and Adolescent acne / 대한피부과학회지

BACKGROUND: Acne is principally a disorder of adolescence. However, a number of observational studies have documented a significant degree of acne in adult women. One study found a difference in women between late-onset acne and acne that persisted from adolescence. There were significant higher sebum excretion rates among women whose acne originated during the teenage years compared with late-onset acne groups. OBJECTIVE: The purpose of this study was to examine the clinical features of patients with acne and to compare the sebum excretion rates and the density of P acnes in adult acne with that in adolescent acne. METHODS: Thirty nine patients with acne vulgaris were clinically evaluated. Sebum secretion rates were evaluated by Sebutape method. The density of P acnes counted by scrub method. RESULTS: 1. The severity grades were mild to moderate in adult acne groups, consisting with the lower acne lesion counts than that of adolescent acne groups. 2. Sebum secretion rates by Sebutape(R) method showed different patterns in two groups. The mean value in the adult acne groups was lower than that in adolescent acne groups, but not statistically significant. Chin area dominant pattern, shown in adult acne groups, were not apparent in adolescent acne groups. 3. The density of P acnes was a lower mean value in the adult acne groups, but not statistically significant. Only in adolescent acne groups, the severity grades are well correlated to the density of P acnes. CONCLUSION: Adult acne was mild to moderate in severity. Clinically, adult acne differs from adolescent acne in that the lesions are located most commonly around the chin. Sebum excretion rate was the highest in the chin area of patients with adult acne. But there was no significant difference in two groups. Also the density of P acnes was not significantly different in two groups.

A Case Report of Mycobacterium Abscessus Septicemia Due to Chemoport Infection / 감염

Mycobacterium abscessus, a rapidly growing mycobacterium, is an opportunistic pathogen which causes a wide variety of clinical symptoms. Recently non-tuberculous mycobacterial infections are increasing among immunocompromised patients and made 4% of total cases of mycobacterial infection. To our knowledge, there has been no report of systemic infection caused by rapidly growing mycobacterium in Korea. We experienced a case of M. abscessus septicemia due to chemoport infection in a 47-year old female who was diagnosed as ovarian cancer stage IIIc and was in the immunocompromised state after systemic chemotherapy. The patient manifested with fever, chilling, headache, and nausea, though, there were no abnormalities on physical examination. When the patient was receiving empirical antibiotic therapy, a rapidly growing mycobacterium was detected in repeated blood cultures. She was improved with not only systemic an-tibiotic treatment but also removing the chemoport. But short course (4 weeks) of antibiotic therapy caused incomplete treatment and made multiple skin abscess. After incision and drainage of the lesions and administration of prolonged antibiotic therapy, no additional infection was observed. Based on our experience and the review of the literatures, catheter-related bacteremia due to rapidly growing mycobacterium, including M. abscessus, should be treated with catheter removal and appropriate antibiotic therapy for at least 3 to 6 months based on in vitro susceptibility testing. When a patient in neutropenic state presents sustained fever after treatment with conventional antibiotics, non-tuberculous mycobacterial infection should be considered.