We describe the emergence of a new quinolone resistance pattern in Salmonella enterica isolates from Southeast Asia. These isolates are susceptible to nalidixic acid but exhibit reduced susceptibility to ciprofloxacin. The increase of such strains may threaten the value of the nalidixic acid disk test to screen for reduced fluoroquinolone susceptibility in salmonellas.

We tested the fl uoroquinolone susceptibility of 499 Salmonella enterica isolates collected from travelers returning to Finland during [2003][2004][2005][2006][2007]. Among isolates from travelers to Thailand and Malaysia, reduced fl uoroquinolone susceptibility decreased from 65% to 22% (p = 0.002). All isolates showing nonclassical quinolone resistance were from travelers to these 2 countries.

Human intestinal Enterococcus spp. was monitored during a 2-y period after 7 d clindamycin treatment. Consecutive faecal samples were collected from 8 healthy volunteers, 4 of whom had received clindamycin. After treatment, the number of enterococcal colonies was diminished and species variation extended. Erythromycin and clindamycin resistance increased from 19% to 69% and 0% to 67%, respectively. Elevated resistance levels lasted up to 9 months and erm(B) was detected in samples up to 6 months. Our results show that the clindamycin treatment had a prolonged impact on resistance and species variation.

The purpose of this study was to determine the prevalence of acquired antimicrobial resistance in Streptococcus pneumoniae isolated from nasopharyngeal swabs and blood and cerebrospinal fluid (CSF) specimens of 3,028 children hospitalized with signs or symptoms of pneumonia, sepsis, or meningitis in rural Philippines between 1994 and 2000. Pneumococci were identified using standard methods, serotyped, and their susceptibility to oxacillin, erythromycin, tetracycline, chloramphenicol, and trimethoprim-sulfamethoxazole was determined using the disk diffusion method. Penicillin minimum inhibitory concentrations (MICs) of the oxacillin-resistant isolates were further tested. The clonality of the penicillin-nonsusceptible (PNSP) isolates was analyzed using pulsed-field gel electrophoresis (PFGE) and multi-locus sequence typing (MLST). Altogether 1,048 isolates were analyzed, of which 35 were invasive and 1,013 nasopharyngeal isolates. None was resistant, but 22 (2.1%) were intermediately resistant to penicillin, 4 (0.2%) were resistant to chloramphenicol, 3 (0.2%) to erythromycin, 39 (3.7%) to tetracycline, and 4 (0.2%) to trimethoprim/sulfamethoxazole. Twelve of the 22 PNSP isolates were of serotype 14 and of sequence type 63. These included the two invasive PNSP isolates. PFGE profiling further identified three separate clusters among the sequence of type 63, serotype 14 (ST63(14)) isolates. Antimicrobial resistance in both invasive and nasopharyngeal pneumococcal pediatric isolates in rural Philippines is rare. In spite of this remote setting, the PNSP isolates of the serotype 14 clusters were of ST63 type, which has been described previously on other continents.

The telithromycin susceptibility of 210 erythromycin-resistant pneumococci was tested with the agar diffusion method. Twenty-six erm(B)-positive isolates showed heterogeneous resistance to telithromycin, which was manifested by the presence of colonies inside the inhibition zone. When these cells were cultured and tested, they showed stable, homogeneous, and high-level resistance to telithromycin.Telithromycin (TEL), the first ketolide drug, was developed to overcome macrolide resistance and introduced into clinical use a few years ago. The antimicrobial spectrum of TEL covers the most important respiratory pathogens, including macrolide-resistant pneumococci, but it is inactive against macrolidelincosamide-streptogramin B-resistant Streptococcus pyogenes and constitutively macrolide-lincosamide-streptogramin B-resistant Staphylococcus aureus strains (1,2,6,15,18).According to data collected over 3 years in the international PROTEKT study, only 10 TEL-resistant (TEL R) isolates were detected from among over 13,000 clinical pneumococci (9). A low occurrence of TEL-nonsusceptible pneumococci has also been reported in other studies (3,17,19,24). However, there is some evidence that TEL resistance might be emerging among pneumococci (8,11,13,21). Pneumococci with a macrolide resistance mechanism usually have elevated TEL MICs compared to macrolide-susceptible wild-type isolates (3,5,15). However, the TEL MICs of these isolates do not usually exceed the CLSI breakpoint for nonsusceptible isolates (Ն2 g/ ml) (10,14). Mutations at macrolide and ketolide binding sites, such as domains II and V of 23S rRNA and ribosomal proteins L4 and L22, have been reported to associate with an elevated TEL MIC. Mutations in the resistance determinant erm(B) have also been suggested to confer TEL resistance (13).In our previous study carried out in Finland, 2.8% of pneumococci (n ϭ 1,007) had TEL MICs of Ն2 g/ml, and nearly all such isolates carried erm(B). However, due to the lack of breakpoints for the agar dilution method used in the study, the proportion of telithromycin nonsusceptibility could not be determined (20). The objectives of this study were to investigate the TEL susceptibility of isolates with a known macrolide resistance determinant using an approved CLSI disk diffusion method (4) and to compare these results with those obtained by the agar dilution (5) and CLSI broth microdilution (4) methods.(Preliminary results have been presented at the 16th European Congress of Clinical Microbiology and Infectious Diseases, Nice, France, 2006, poster P 1277.) Bacterial isolates and susceptibility testing. Two hundred ten erythromycin-resistant (MIC Ն 0.5 g/ml) pneumococci with a known macrolide resistance determinant and 47 randomly selected erythromycin-susceptible pneumococci were investigated from among 1,007 Streptococcus pneumoniae isolates that were collected in 2002 in Finland for macrolide resistance surveillance purposes (20).TEL susceptibility was tested with 15-g TEL disks (Oxoid Ltd., Basingstoke, Hampshire, England) b...