Corynebacterium renale group infections

M G COLLETT

GENERAL INTRODUCTION: IRREGULAR, NON-SPORING, GRAM-POSITIVE RODS

Introduction

The most important diseases caused by the Corynebacterium renale group (C. renale, C. pilosum and C. cystitidis) of bacteria are contagious bovine pyelonephritis (a specific infection of the urinary tract of cattle characterized by acute to chronic purulent cystitis, ureteritis and pyelonephritis), ulcerative posthitis in bulls and adult wethers, and vulvitis in ewes.

Contagious bovine pyelonephritis has been recognized in Europe for over a century, and has also been reported in the Middle East, Japan, the USA, South America, Africa and Australia. ^{12, 50, 54, 66, 68, 71} There have also been occasional reports of ovine pyelonephritis and cystitis.^{2, 31} Enzootic posthitis is an important disease in adult wethers in the high rainfall areas of Australia, where reports go back to the early 1900s.⁶⁴

The pathogenicity varies between C. renale, C. pilosum and C. cystitidis. Infection with either C. renale or C. pilosum causes pyelonephritis and cystitis in cows, while C. cystitidis infection causes a cystitis which is more severe and haemorrhagic than that caused by the former organisms.^{33, 36, 94, 95}

In sheep, reports of posthitis and vulvitis caused by bacteria of the C. renale group have come from South Africa, Nigeria, Australia (where the disease is very important), New Zealand and North America.^{7, 16, 20,69, 78, 79, 93} Oslington⁶⁴ from Australia classified urease-positive diphtheroids isolated from diseased and healthy prepuces as C. renale (49,6 per cent), C. pilosum ( 34,6 per cent) and C. cystitidis (6,9 per cent) with 9,1 per cent unclassified. Corynebacterium renale may be part of the normal flora of the female genital tract of sheep and goats,^{58, 59} and the organism has also been isolated from the accessory sex organs and epididymis of healthy rams.⁴⁴

In goats, ulcerative posthitis has been described in India⁵³ and in Angora wethers in Texas,⁷³ while a most unusual case of disseminated necrogranulomatous osteomyelitis (with pathological fractures), lymphadenitis, hepatitis and nephritis has been reported in a dairy goat in the USA.³

Bacteria of the C. renale group can cause pyelonephritis and cystitis in horses.^{12, 23} Corynebacterium pilosum has been isolated from the urine of an incontinent gelding.⁸⁶ In South Africa, Steyn in 1940⁸³ was the first to describe ‘pisgoed’, which he considered to be non-contagious. Corynebacterium renale has been isolated on rare occasions from the prepuce of normal bulls and from cases of chronic pyelonephritis in cows and enzootic posthitis and vulvitis in sheep at the Onderstepoort Veterinary Institute in South Africa.³⁰ The organism has also been isolated from cases of ulcerative balanoposthitis and vulvovaginitis, a readily transmissible venereal disease of Dorper sheep in South Africa. Mycoplasma mycoides mycoides LC has been shown to play a major aetiological role in this disease (see Ulcerative balanoposthitis and vulvovaginitis of sheep).⁸⁹

Aetiology

Bacteria of the C. renale group (C. renale, C. pilosum and C. cystitidis) are aerobic and facultatively anaerobic. Although originally all were classified as C. renale (see the introduction, Irregular, non-sporing, Gram-positive rods: Table 1), biochemical^{14, 40} and antigenic differences,⁹⁴ and differences in nutritional requirements³² between strains necessitated the designation of new species.⁹⁵ These bacteria are rather large (0,7 to 3,0 μm or more), non-motile, non-sporing, non-capsulating, irregularly staining Gram-positive rods, often with pointed ends and pili.¹⁴ A special selective medium for the isolation of urinary corynebacteria from samples contaminated with faeces or urine of cows has been developed.³⁵ On blood agar, the colonies are small, dewdrop-like, raised, opaque, yellow or ivory-coloured, and dull without haemolysis.^{60, 88} Colonies grown on agar can be pushed intact across the surface.⁶⁰ The bacteria hydrolyze urea more rapidly than most other urease- positive bacteria.¹¹

Epidemiology

In cattle herds where pyelonephritis occurs, prevalence rates are in the region of 0,5 to 1,5 per cent and up to a third of affected animals may die or have to be culled.⁵⁴

Corynebacterium renale and C. pilosum can be isolated from the vulvovaginal and penile mucosa of healthy cows and bulls, respectively. On the other hand, C. cystitidis has only been isolated from diseased cows, although it does occur in the prepuce of healthy bulls.^{36, 39, 94, 95} Some 10 to 20 per cent of animals may be carriers of the bacteria. ^{21, 61} Healthy cows may shed bacteria in their urine intermittently or regularly for seven months or longer.^{4, 33} The organisms can survive in moist paddock soil for two (C. renale and C. cystitidis) to seven months (C. pilosum).²⁸

Multiparous cows are mainly affected.⁵⁴ The disease often follows parturition, but pregnant animals may also be affected.^{4, 87} The disease is rare in heifers and bulls.^{4, 12, 61} In dairy herds, there is evidence that C. renale spreads from animal to animal along stanchion lines.⁶¹ The spray of urine from infected cows can probably directly contaminate the vulvas of animals standing in close proximity to them.³⁵ Venereal transmission is possible in cows.⁷² Careless use of catheters can also play a role in the spread of the disease.⁶⁶

Cold weather^{4, 37} and the stress associated with peak production...