Antibiotic resistance patterns of aerobic coryneforms and furazolidone-resistant Gram-positive cocci from the skin surface of the human axilla and fourth toe cleft

Samples of skin surface bacteria from 28 healthy subjects plated directly o n to selective and non-selective media revealed that the proportion of aero bic coryneforms and furazolidone-resistant Gram-positive cocci (FURECs) res istant to erythromycin was significantly greater in the fourth toe cleft th an in the axilla (P < 0.05). There were more erythromycin-resistant bacteri a than tetracycline-resistant bacteria at both sites (P = 0.001 for the toe cleft; P < 0.01 for the axilla). In total, 160 distinct isolates were obta ined, of which 42 were FURECs and 118 were aerobic coryneforms. Of these, 1 53 (96%) were resistant to erythromycin and 66 (41%) to tetracycline. All e xcept seven of the tetracycline-resistant strains were also resistant to er ythromycin. The resistant isolates belonged to a variety of species. CDC gr oup ANF corynebacteria were most numerous and composed 31% of all isolates. The majority (76%) of FURECs were Identified as Micrococcus luteus. MIC de terminations on selected strains revealed that tetracycline-resistant FUREC s were sensitive to doxycycline and minocycline, as were most tetracycline- resistant coryneforms. Nine coryneform isolates were cross-resistant to all three tetracyclines. Only a minority of erythromycin-resistant FURECs (21% ) demonstrated a macrolide-lincosamide-streptogramin type B (MLS)-resistant phenotype with inducible or constitutive cross-resistance to clindamycin a nd the type B streptogramin, pristinamycin I-A. Twenty-nine erythromycin-re sistant FURECs had a novel phenotype distinct from MLS and macrolide-strept ogramin type B resistance. In contrast, most coryneforms (79%) were MLS res istant. Among the remainder, two unusual erythromycin resistance phenotypes were apparent, both of which differed from the unusual phenotype in FURECs . This study has revealed that the non-staphylococcal aerobic flora of skin contains a considerable reservoir of tetracycline and erythromycin resista nce determinants. The three unusual macrolide resistance phenotypes may be associated with novel resistance mechanisms.