Norichika Asoh

Emergence of Rifampin-Resistant Rhodococcus equi with Several Types of Mutations in the rpoB Gene among AIDS Patients in Northern Thailand

ABSTRACT The antimicrobial susceptibilities of 30 Rhodococcus equi isolates obtained from 30 patients between 1993 and 2001 in northern Thailand were investigated. The MICs showed a tendency toward resistance to various antibiotics but sensitivity to imipenem, minocycline, vancomycin, and teicoplanin (MICs, ≤0.5 μg/ml) and relative sensitivity to meropenem, clarithromycin, and ciprofloxacin (MICs, ≤2 μg/ml). Of the 30 isolates, 26 were susceptible (MICs, ≤1 μg/ml), 1 showed low-level resistance (MIC, 8 μg/ml), and 3 showed high-level resistance (MICs, ≥64 μg/ml) to rifampin. PCR amplification and DNA sequencing of the rpoB gene and molecular typing by pulsed-field gel electrophoresis (PFGE) were performed for eight R. equi isolates from eight AIDS patients with pneumonia or lung abscess caused by R. equi between 1998 and 2001, including one low- and three high-level rifampin-resistant isolates. As a result, two high-level rifampin-resistant strains with PFGE pattern A had a Ser531Trp (Escherichia coli numbering) mutation, and one high-level rifampin-resistant strain with PFGE pattern B had a His526Tyr mutation, whereas one low-level rifampin-resistant strain with PFGE pattern C had a Ser509Pro mutation. Four rifampin-susceptible strains with PFGE patterns D and E showed an absence of mutation in the rpoB region. Our results indicate the presence of several types of rifampin-resistant R. equi strains among AIDS patients in northern Thailand.

Low Concentrations of Mupirocin in the Pharynx following Intranasal Application May Contribute to Mupirocin Resistance in Methicillin-Resistant Staphylococcus aureus

ABSTRACT We describe a patient with methicillin-resistantStaphylococcus aureus (MRSA) colonizing the pharynx. The MIC of mupirocin was 0.25 μg/ml before treatment and increased after treatment to 8 μg/ml. Using pulsed-field gel electrophoresis, we confirmed that the genotypes of MRSA that colonized the pharynx before and after the use of mupirocin were identical. We measured the delivery of mupirocin to the pharynx in three normal volunteers and two patients. Low concentrations of mupirocin were present in the pharynx in all cases 10 min to 3 days after intranasal application. Our data suggested that low concentrations of the drug in the pharynx after intranasal application of mupirocin ointment might explain the selection of mupirocin resistance in MRSA.

High Rate of Transmission of Penicillin-Resistant Streptococcus pneumoniae between Parents and Children

ABSTRACT Transmission of Streptococcus pneumoniae between children and their parents was evaluated in 29 pairs from 25 families. The serotypes of 35 pneumococcal isolates from 18 (62.1%) of 29 child-parent pairs were identical. Of the 35 isolates, 23 showed intermediate resistance and 10 were fully resistant to penicillin G. PCR indicated that all 35 strains had at least one alteration in penicillin-binding protein genes pbp1a, pbp2x, and pbp2b and 33 strains had macrolide resistance genes mef(A) and/or erm(B). As a result, the PCR patterns of 16 of 18 pairs were identical. Molecular typing by pulsed-field gel electrophoresis showed that 12 pairs were indistinguishable, 3 pairs were closely related, 2 pairs were possibly related, and only one pair was different. Our data indicate the presence of a high rate of transmission of penicillin-resistant S. pneumoniae between children and their parents.

Possible High Rate of Transmission of Nontypeable Haemophilus influenzae, Including β-Lactamase-Negative Ampicillin-Resistant Strains, between Children and Their Parents

ABSTRACT The possible transmission of nontypeable Haemophilus influenzae between children and their parents was evaluated in 18 pairs of subjects from 15 families. Of the 33 isolates, 31 were found to be β-lactamase negative, including 10 β-lactamase-negative, ampicillin (AMP)-resistant (BLNAR) strains (AMP MIC, ≥1.0 μg/ml) and 2 were β-lactamase producing. Molecular typing by pulsed-field gel electrophoresis (PFGE) showed that 10 BLNAR isolates had 6 patterns, 23 non-BLNAR isolates had 13 patterns, and these patterns were different from each other, except for 1 pattern. As a result, the PFGE patterns in 14 of 18 pairs were indistinguishable and those in 4 pairs were different. These data indicate a possible high rate of intrafamilial transmission of nontypeable H. influenzae, including BLNAR strains, between children and their parents.

Enterocolitis Caused by Methicillin-Resistant Staphylococcus aureus: Molecular Characterization of Respiratory and Digestive Tract Isolates

We investigated the mechanism of outbreak of enterocolitis caused by methicillin‐resistant Staphylococcus aureus (MRSA). Five epidemiological markers [coagulase type, enterotoxin type, toxic shock syndrome toxin‐1 (TSST‐1) production, β‐lactamase production and pulsed‐field gel electrophoresis (PFGE)] of 45 strains of MRSA isolated simultaneously from the respiratory tract (nasal cavity and/or pharynx and/or sputum) and stool (plus one sample of gastric juice) in 13 patients (8 males and 5 females, mean age, 77.1 years) were compared retrospectively. Forty‐four of the 45 isolates of MRSA were positive for enterotoxin C and TSST‐1 production, and the remaining isolate was positive for enterotoxin A and negative for TSST‐1 production. All isolates were coagulase type II, and 27 showed β‐lactamase production. The patterns of coagulase type, enterotoxin type, TSST‐1 and β‐lactamase production of MRSA isolated from the respiratory tract were similar to those of MRSA isolated from the intestine in 12 of 13 patients. Molecular typing by PFGE demonstrated that the pattern of respiratory tract isolates was identical to those of stool isolates in 9 (69.2%), similar in 3 (23.1%), and different in 1 (7.7%). The data suggested that enterocolitis might be caused by the MRSA colonized in the respiratory tract and incorporated into the digestive tracts. Therefore, we propose that early eradication of MRSA in the respiratory tract is important for protection of patients against the development of enterocolitis, particularly in susceptible patients, e.g., immunocompromised or pre‐operated patients with digestive diseases, especially malignant disease.

Clinical and microbiological characteristics of community-acquired pneumonia among human immunodeficiency virus-infected patients in northern Thailand

Human immunodeficiency virus (HIV) infections are prevalent in Thailand. However, the clinical and microbiological characteristics of community-acquired pneumonia (CAP) in such patients are not completely clear at present. In the present study, we analyzed the characteristics of CAP in 191 HIV-infected patients (192 episodes, 130 males and 61 females, mean age 32.9 years, range: 20–62) who had been admitted to Nakornping Hospital in northern Thailand between December 1996 and January 2002. The mean peripheral blood CD4 lymphocyte count was 68.5/mm3 (range: 0–791). The most common organisms detected in the blood of the subjects were as follows: Penicillium marneffei, 13, Salmonella spp., 5, Cryptococcus neoformans, 4, Staphylococcus aureus, 3, and Rhodococcus equi, 3, and the most common organisms detected in sputum included Haemophilus influenzae, 38, P. marneffei, 10, Streptococcus pneumoniae, 10, R. equi, 9, and S. aureus, 9. Life-threatening meningitis in 5 (cryptococcal in 3 and tuberculous in 2), pneumothorax in 2, and tuberculous lymphadenitis in 1 were also noted, resulting in 21 fatalities (10.9%). The mean peripheral blood CD4 lymphocyte count for cases in which the subject died was 74.8/mm3 (range: 0–340). Logistic regression analysis demonstrated that high age (odds ratio of over 40 years: 15.62) and R. equi infection (odds ratio: 8.14) are related to death of HIV-infected patients with CAP. The above findings indicate that various types of organisms, including mixed organisms, cause CAP in HIV-infected patients in northern Thailand, and high age and R. equi infection seem to be risk factors for death.

Molecular characteristics of outbreaks of nosocomial infection with influenza A/H3N2 virus variants.

OBJECTIVE To describe outbreaks of nosocomial influenza infection with molecular methods and to elucidate the viral linkages among outbreak case patients including both inpatients and healthcare workers (HCWs). SETTING A 180-bed acute and long-term care hospital in Japan. METHODS Retrospective observational study of nosocomial outbreaks of infection with influenza A/H3N2. Together with information about onset dates and vaccination history, we obtained nasopharyngeal swab samples from individuals with cases of influenza or influenza-like illness (ILI). The hemagglutinin genes of the recovered viruses were sequenced and compared, along with those of community-circulating strains, for similarity by phylogenetic tree analysis. RESULTS The outbreaks occurred from February 26 through April 3, 2007, during the 2006-2007 epidemic season, and they involved 11 patients and 13 HCWs. The 2 outbreaks involved 2 different genotypes of influenza A/H3N2 viruses. These virus variants were closely related to the influenza strains that were circulating in the community during the same epidemic season. CONCLUSION This study showed the dissemination of highly homologous influenza virus variants among inpatients and HCWs within a short period, as a result of nosocomial transmission. These strains were also similar to influenza strains that were circulating in the community.

Possible Relationship of PFGE Patterns of Moraxella catarrhalis between Hospital- and Community-Acquired Respiratory Infections in a Community Hospital

We describe a prospective study of molecular analysis of Moraxella catarrhalis isolated from a community hospital. Our study was designed to investigate the possible relationship of pulsed‐field gel electrophoresis (PFGE) patterns of M. catarrhalis between hospital‐ and community‐acquired respiratory infections. A nosocomial outbreak of M. catarrhalis was observed between September 2000 and September 2001. During the study period, 40 strains of M. catarrhalis were isolated from a total of 32 patients with respiratory infections (26 strains from 18 inpatients, and 14 strains from 14 outpatients). We compared the PFGE patterns in 40 strains of M. catarrhalis isolated from the respiratory tract of the study patients. The genomic types of M. catarrhalis were classified into three PFGE patterns (A, B, and C). Interestingly, the nosocomial outbreak of M. catarrhalis included two patterns (A and B). Of the three patterns, two patterns (A and B) were found in both inpatients and outpatients. More interestingly, two subtypes of pattern B (B1 and B4) were simultaneously found in both inpatients and outpatients. Our results indicated that PFGE with SmaI chromosomal digestion is a suitable technique to establish the inter‐strain genetic relatedness of M. catarrhalis, and suggested that the outbreak of M. catarrhalis occasionally included miscellaneous PFGE patterns. The results also showed that PFGE patterns of M. catarrhalis isolates were similar between hospital‐ and community‐acquired respiratory infections. Analysis of the subtypes suggested that there might be some association between hospital‐ and community‐acquired respiratory infections caused by M. catarrhalis.

Antimicrobial Susceptibility and Serotype Distribution of Streptococcus pneumoniae and Molecular Characterization of Multidrug-Resistant Serotype 19F, 6B, and 23F Pneumococci in Northern Thailand

ABSTRACT Penicillin-resistant Streptococcus pneumoniae is widely spread worldwide. Our study was undertaken to examine the susceptibility and serotypes of S. pneumoniae in northern Thailand. Ninety-three S. pneumoniae strains were isolated from 93 patients at Chiang Mai University Hospital, Chiang Mai, Thailand, from September 1999 to June 2000. The strains were isolated from sputum (n = 51), blood (n = 15), nasopharynges (n = 14), and other sources (e.g., pus, ears, ascites, and cerebrospinal fluid) (n = 13). Of the 93 isolates, 29 (31.2%) were susceptible, 24 (25.8%) showed intermediate resistance (MIC, 0.12 to 1.0 μg/ml), and 40 (43.0%) were fully resistant (MIC, ≥2.0 μg/ml) to penicillin G. Seven (46.7%) from blood, 5 (35.7%) from nasopharynges, 15 (29.4%) from sputum, and 2 (15.4%) from other sources were susceptible isolates. Serotyping with the use of antiserum revealed differences in the predominant types that were susceptible (6A, 11A, and 19A), intermediately resistant (6B and 23F), and fully resistant (6B, 19F, and 23F). Molecular typing by pulsed-field gel electrophoresis of multidrug-resistant pneumococci showed four patterns (A, B, C, and D) for 16 isolates of serotype 19F, with pattern B being predominant (12 isolates). This finding was different from that with the Taiwan multidrug-resistant serotype 19F clone. Eleven isolates of serotype 6B all showed pattern E, and nine isolates of serotype 23F showed two patterns (F and G), with pattern F being predominant (seven isolates). This finding was similar to that with the Spanish multidrug-resistant serotype 23F clone. Our results indicated that the resistance of pneumococci to antibiotics in northern Thailand is progressing rapidly and that effort should be intensified to prevent any spread of pandemic multidrug-resistant serotypes 19F, 6B, and 23F.

Antimicrobial susceptibility and genetic characteristics of Haemophilus influenzae isolated from patients with respiratory tract infections between 1987 and 2000, including β-lactamase-negative ampicillin-resistant strains

The minimum inhibitory concentration (MIC) of five antibiotics and the presence of resistance genes was determined in 163 Haemophilus influenzae isolates collected over 13 years (1987–2000) in four two-yearly sampling periods from patients with respiratory tract infections. The prevalence of β-lactamase-negative ampicillin-susceptible strains was approximately 80% over the sampling period although fewer strains (65·9%) were recovered in the period 1995–1997. TEM-1 type β-lactamase-producing strains were less frequent starting at 15·6% and declining to 2·2% in the final sampling period. Low-β-lactamase-negative ampicillin-resistant (BLNAR) strains were uncommon in 1987–1989 (2·2%), peaked to 19·5% in 1995–1997, but fell back to 11·1% by 2000. Fully BLNAR strains were not detected until the last sampling period (6·7%). The MICs of ampicillin, levofloxacin, cefditoren and ceftriaxone remained stable but there was an eight-fold increase in the MIC of cefdinir over the sampling period. Pulsed-field gel electrophoresis of DNA digests showed that three representative BLNAR strains were genetically distinct and 11 DNA profiles were identified among 17 low-BLNAR strains. These data suggest that the number of genetically altered BLNAR and low-BLNAR strains are increasing in Japan.