[Detection methods and changes in metallo-beta-lactamase-producing Gram-negative rod isolates at Nagasaki University Hospital from 1991 to 2005].

Since plasmid-mediated metallo-beta-lactamase (MBL)-producing Pseudimonas aeruginosa was reported in Japan, MBL-producing Gram-negative rods (GNRs) have emerged worldwide. We developed a way to detect MBL-producing GNRs in routine examination using broth microdilution with the MBL inhibitor sodium mercaptoacetate (SMA) in frozen plates. Between 1996 and 2005, we evaluated this and other methods, including broth microdilution with another MBL inhibitor dipicolinic acid (DPA) in dry plates, conventional PCR, and a combined simple DNA preparation and enzymatic PCR product detection. The combined method is suitable for detecting IMP-type MBL-producing GNRs from numerous isolates. Broth microdilution with SMA at a concentration of 400 microg/mL had high performance and detected most PCR-positive MBL-producing GNRs in routine antimicrobial susceptibility testing. DPA in dry plates at 400 microg/mL yielded false positive results in 11.4% of isolates but worked satisfactorily at 175 microg/mL and 400 microg/mL of SMA in frozen plates. Until 1996, MBL had been detected from only 6 bacterial species, i.e., Pseudomonas aeruginosa, Pseudomonas putida, Pseudomonas stutzeri, Achromobacter xylosoxidans, Serratia marcescens, and Citrobacter freundii, MBL-producing GNRs were later found in other glucose nonfermenting GNRs such as Acinetobacter baumanii, Acinetobacter lwoffii, and Burkholderia cepacia complex and Enterobacteriaceae. Most MBL-producing bacteria were multidrug resistant and no antimicrobial agents exist that are active against such isolates in monotherapy, making their rapid detection very important in controlling infection control.

The first telithromycin-resistant Streptococcus pneumoniae isolate in Japan associated with erm(B) and mutations in 23S rRNA and riboprotein L4.

This report presents the case of a patient associated with a Streptococcus pneumoniae isolate that was resistant to a new ketolide antibiotic, telithromycin (minimum inhibitory concentration: 4 microg/ml). The patient, a 61-year-old female with bronchiectasis, was treated with 200-400 mg of clarithromycin daily for 6 years until the isolation of the resistant strain but without prior exposure to telithromycin. The strain was isolated from her sputum but not from the nasopharynx. This isolate carried erm(B) and had mutations in 23S rRNA and riboprotein L4. To our knowledge, this is the first case report concerning a telithromycin-resistant S. pneumoniae isolate in Japan by mutation in L4. Although the long-term clarithromycin administration may have contributed to the induction of resistance in this patient, this could not be confirmed, since S. pneumoniae was not isolated until the present episode.

Clinical and bacteriological characteristics of IMP-type metallo-beta-lactamase-producing Pseudomonas aeruginosa.

IMP-type metallo-beta-lactamase-producing bacteria have recently emerged worldwide. We conducted a case-control study in which 69 inpatients harboring bla(IMP)-positive Pseudomonas aeruginosa and 247 control subjects with bla(IMP)-negative pathogens were investigated. Prolonged hospitalization, antineoplastic chemotherapy, corticosteroid therapy (P=.001), and indwelling urinary catheters (P=.04) were risk factors for isolation of bla(IMP)-positive pathogens. The predominant source was urine (P=.001). The duration of antibiotic treatment and the total dose (including of carbapenems) were significantly greater among case patients than among control subjects (P<.01). bla(IMP)-positive P. aeruginosa isolates were more frequently resistant to multiple drugs (P=.001) and caused more infections (P=.001) than bla(IMP)-negative pathogens. There were no significant differences in bacteriological outcome (P=.94); however, infection-related death was more frequent among case patients than among control subjects (P=.023). These results suggest that precautionary measures against the spread of bla(IMP)-positive isolates are needed, because, for most of such pathogens, no antibiotic is potent enough to be used as a single agent in treatment of infection.