Gardnerella Vaginalis: Characteristics, Clinical Considerations, and Controversies B
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CLINICAL MICROBIOLOGY REVIEWS, July 1992, p. 213-237 Vol. 5, No. 3 0893-8512/92/030213-25$02.00/0 Copyright 1992, American Society for Microbiology Gardnerella vaginalis: Characteristics, Clinical Considerations, and Controversies B. WESLEY CATLINt Department ofMicrobiology, The Medical College of Wisconsin, Milwaukee, Wisconsin 53226 INTRODUCTION .................................................................. .214 IDENTIFICATION AND CHARACTERISTICS OF G. VAGINALIS ....... 0........... *** ...... 00 .............. *..214 Appearance of Cells and Colonies........................................... ........ 000 ........ 000 ........... 0.0 .........0.214 1%.9 1- Isolation Methods................................................................ ............... oo ........................ *..* ...215 Differential Tests................................................................. ..216 It . Presumptive identification.................................................. I.............................. .. 1lo ^.,1IA Confirmation................%.,%FARRAR 21143IMPRA . o . 0 o 0 . o . o o o o 0 o........... ............. 00.00 ....................................................__________ _ _ klosn Confusing catalase-negative bacteria........ .216 Methods: some yield inconsistent results... .217 1% s _ Other characteristics............................ ......... ......o. ... .2177 Rapid detection................................... .2:,17 Structure, Composition, and Toxic Products ;... ****O..* ....... 0.000.0 .................*.................................z'17 Cell wall............................................ .2117 R.nnnalvearrharidp Ihvpr >12 Pili .... ... .... ..... ... ........ .............218 Lipids........................oo.ooo.oo......oooo.. 218 Proteins................................ .....oooooooo. 219 DNA ......................................oooo... 219 Toxic products............. Surface Adhesion........................ Susceptibility to Chemotherapeutic Agents............. 5-Nitroimidazoles and -Lactams and carbapenems.221 Erythromycins ......221 ............................................222 Other antibacterial Growth Requirements.222 Epidemiological Genetic ANIMAL MODELS FOR STUDIES OF GARDNERELLA SIGNIFICANCE OF G. VAGINALIS IN BACTERIAL VAGINOSIS.223 Diagnostic Criteria.224 Endogenous Vaginal Flora 224 Influences on Endogenous Vaginal Flora 224 Flora Associated with Bacterial Cultural Microscopic findings Biochemical Bacterial vaginosis has a polymicrobic Transmission of Bacteria Associated with Vaginosis..227 G. VAGINALIS IN OTHER Endometrium, Fetal Membranes, and the Newbor Infant.228 Maternal Neonatal infections. Suppurative Female Urinary Tract.228 Male Urogenital Bloodstream .229 IMMUNOLOGICAL RESPONSES TO G. VAGINALIS INFECTION 230 CONCLUSIONS AND PROSPECTS........................................... t Present address: 3886 La Jolla Village Drive, La Jolla, CA 92037-1412. 213 214 CATLIN CLIN. MICROBIOL. REV. ACKNOWLEDGMENT ................ 231 REFERENCES ................ 231 INTRODUCTION of G. vaginalis, its differential and biological features, its pathogenic potential, and areas of fundamental research in Different interpretations of the clinical significance of need of further study. Gardnerella vaginalis, its Gram stain reaction, and its taxo- nomic position have generated considerable controversy. IDENTIFICATION AND CHARACTERISTICS First recognized by Leopold (126), the organism was named OF G. VAGINALIS Haemophilus vaginalis by Gardner and Dukes in 1955 (75) because it was a gram-negative rod successfully isolated on Appearance of Cells and Colonies blood agar but not on other agar media and it was believed responsible for a characteristic vaginal discharge. The ab- G. vaginalis cells are gram-negative to gram-variable, sence of requirements for X and V factors (hemin and NAD, small, pleomorphic rods that are nonmotile and do not respectively), which are needed for the growth of accepted possess flagella, endospores, or typical capsules (82, 172). In Haemophilus species, the tendency to retain the crystal vaginal fluid smears the Gram reaction of G. vaginalis may violet dye in the Gram reaction, and some corynebacterium- vary from positive to negative. The cellular morphology in a like features suggested that the organism might better be Papanicolaou preparation can be seen in noncrowded areas associated with the genus Corynebacterium. Hence, it was peripheral to the epithelial cells in Fig. 1. referred to as Corynebacterium vaginale by Zinnemann and The physiological state of the bacteria affects their mor- Turner (249) and others (56, 243). Two large taxonomic phology and staining reactions (107, 174). Both small cocco- studies published in 1980 (82, 174) analyzed data obtained by bacilli and longer forms occur in 24-h cultures of G. vaginalis a variety of biochemical methods, DNA-DNA hybridization, on blood agar. Their average dimensions are 0.4 by 1.0 to 1.5 and electron microscopy. The findings revealed that "Hae- ,um (59). Although cells can be up to 2 to 3 ,um in length, they mophilus vaginalis" forms a good taxospecies that displays do not elongate into filaments (82, 228). Smith (211) observed little or no similarity to established gram-positive or gram- that cultures on vaginalis agar (V agar; see below) exhibited negative genera. The need for a new genus led Greenwood many short rods that were gram negative, whereas the cells and Pickett (82) to propose the name Gardnerella vaginalis, were more pleomorphic, clumped, gram variable, and a proposal supported by Piot et al. (174). beaded on a medium containing starch, a fermentable com- In this review I shall use the name G. vaginalis for the pound. G. vaginalis growing in 48-h cultures of patients' organism that was called H. vaginalis or C. vaginale in the blood specimens were reported as predominantly gram pos- earlier literature. Where relevant, I shall mention the type itive (124, 245). The organism was partially or entirely gram strain of the species, indicated by T, which was used as a positive in the early exponential growth phase on the inspis- reference in some studies. Greenwood and Pickett (82) sated serum medium of Loeffler (174) or Roux (249). designated strain 594 of Gardner and Dukes as the G. The resemblance of G. vaginalis to coryneform (diphthe- vaginalis type strain and deposited it in the American Type roid) bacteria (45) was described by many investigators (3, Culture Collection as ATCC 14018T and in the National 13, 56, 59, 133, 164, 174, 208, 243, 246, 249). Angular and Collection of Type Cultures as NCTC 10287T. palisade (picket fence) arrangements of cells occur because The G. vaginalis-associated vaginal syndrome was earlier of snapping that accompanies division. Metaphosphate (vo- called nonspecific vaginitis in recognition of the absence of lutin) granules form in G. vaginalis, especially during culti- recognized agents of vaginitis, such as Trichomonas vagina- vation in the presence of a fermentable compound (59) or lis and Candida species. Until his death in 1982, Gardner sodium phosphate (243). These granules stain gram positive staunchly maintained that the term nonspecific should in- (56, 249) or are reddish purple (metachromatic) when stained clude only those conditions without assignable etiology and with alkaline methylene blue. that G. vaginalis vaginitis is a precisely defined, specific G. vaginalis is beta-hemolytic on media containing human vaginal infection that accounts for most vaginitides previ- or rabbit blood but not on sheep blood agar (24, 59, 82, 172, ously classified as nonspecific (73, 74). Substitution of the 208, 243). Hemolysis is improved by anaerobic incubation term bacterial vaginosis was recommended because vaginitis (119). For media prepared with blood bank blood, hemolysis suggests an inflammatory reaction of the vaginal epithelium, is clearest with blood which is "just time expired" (97). The which is usually absent (46, 73, 91, 201). This syndrome has importance of the composition of the basal medium to which also been given more than 15 other names (96, 200, 235). blood is added is illustrated by the observation that the The pathogenic role of G. vaginalis has been controver- diameters of colonies on Columbia agar base with 5% sheep sial. Inadequate media and methods led to earlier failures to blood were at least twice as large as those on soybean-casein detect small numbers of the organism in cultures of blood digest agar base with 5% sheep blood (78). Furthermore, and urogenital specimens. There is now a greater apprecia- hemolysis of human blood incorporated in Columbia agar tion of G. vaginalis as a cause of extravaginal infections. base from BBL Microbiology Systems was superior to that Lacking results of anaerobic cultures, investigators were obtained in the Difco Laboratories base of the same name blind to the complex ecology of the vagina in health and (173). disease. This deficiency has been corrected in recent studies On a medium prepared with 2% peptone, horse flesh of bacterial vaginosis which reveal a polymicrobic etiology digest, 1% maltose, and 4% human blood, Edmunds (59) that includes G. vaginalis, mycoplasmas, and various anaer- observed that G. vaginalis colonies were only 0.5 mm in obic bacteria (216). The role of G. vaginalis in disease has diameter after aerobic incubation for 3 days. Streptococcus been well described in several reviews (88, 104, 216, 239, pyogenes colonies were said to be "much larger" under the 240). same conditions. Dunkelberg and