Research Article

Treatment of Endometritis Caused by Different Types of Bacteria by Cefoperazone Antibiotic and its Effect on the Days Open and Pregnancy Rate in Dairy Cows (Field Study)

Yahia A. Amin1*, Alaa Eldin Z. Mahmoud2, Mohamed Sabry Aref3, Abd El-Latif Shaker Seddek4, Waleed Younis5

1Department of Theriogenology, Faculty of Veterinary Medicine, Aswan University, Aswan, Egypt; 2Department of Theriogenology, Faculty of Veterinary Medicine, Sohag University, Sohag, Egypt; 3Department of Theriogenology, Faculty of Veterinary Medicine, South Valley University, Qena, Egypt; 4Department of Forensic Medicine and Toxicology, Faculty of Veterinary Medicine, South Valley University, Qena, Egypt; 5Department of Microbiology, Faculty of Veterinary Medicine, South Valley University, Qena, Egypt.

Received | October 24, 2021; Accepted | April 01, 2022; Published | June 20, 2022

*Correspondence | Yahia A Amin, https://orcid.org/ 0000-0003-4075-2664, Department of Theriogenology, Faculty of Veterinary Medicine, Aswan University, Aswan, Egypt; Email: yahiaamin2030@gmail.com

Citation | Amin YA, Mahmoud AEZ, Aref MS, Seddek AL, Younis W (2022). Treatment of endometritis caused by different types of bacteria by cefoperazone antibiotic and its effect on the days open and pregnancy rate in dairy cows (field study). J. Anim. Health Prod. 10(3): 311-319.

DOI | http://dx.doi.org/10.17582/journal.jahp/2022/10.3.311.319

ISSN | 2308-2801

 

 

Copyright: 2022 by the authors. Licensee ResearchersLinks Ltd, England, UK.

This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).

Introduction

Inflammation of the endometrium of dairy cows after parturition by 21 days or more without clinical signs is known as postpartum endometritis (Sheldon et al., 2006; Kusaka et al., 2020). Endometritis has been shown to reduce first-service conception rate and overall pregnancy risk (Barlund et al., 2008, Galvão et al., 2009, Cheong et al., 2011). Now, up to 40% of dairy cattle develop postpartum uterine disease every year, ranging from subclinical endometritis to life-threatening metritis (Sheldon et al., 2019). Recent research concerned with endometritis indicates that the economic impact of endometritis may reach millions of pounds annually (McNaughton, & Murray, 2009). Endometritis can be detected earlier by investigating the presence of purulent vaginal exudate, which poses the same deleterious effect on fertility (Runciman et al., 2008, Runciman et al., 2009, Dubuc et al., 2011). It is also evidenced that infertility associated with lactation may result from endometritis (Salasel et al., 2010). Endometritis does not only reduce fertility by the direct consequence of the inflammation in the uterus and oviduct but is also caused by the abnormal oestrous cycles and damaged oocytes occurring as a result of endometritis (Bromfield et al., 2015).

It was reported that the first fourteen days postpartum (PP) of dairy cattle are associated with a high bacterial contamination rate, reaching 80 - 90% of the cows (Sheldon et al., 2009). Failure to avoid contamination harms uterine function, causing clinical endometritis, which results from the persistence of pathogenic bacteria for at least 3 weeks postpartum (LeBlanc et al., 2002, Sheldon et al., 2009). Most outbreaks of clinical endometritis involve tissue damage, delayed uterine involution, disruption of endometrial function, and perturbation of ovarian cycles (Opsomer et al., 2000, Sheldon et al., 2009). Therefore, avoiding the incidence of endometritis requires a normal postpartum period, which is characterized by the prompt involution of the uterus and regeneration of damaged endometrium, the resumption of ovarian cyclical activity, and the control of pathogenic bacteria in the uterus (Sheldon et al., 2019). Future work should focus on determining which bacteria and virulence factors cause endometritis, and understanding how the host response to infection is regulated in the endometrium to develop strategies to limit the impact of uterine disease on fertility (Carneiro et al., 2016). Moreover, treatment of endometritis is urgent to overcome all pathogenic bacteria without causing significant hazard effects. Furthermore, treatment should be safer, not affect reproductive performance, and significantly decrease the time consumed to achieve pregnancy. Therefore, this study concerns with the determination of bacteria causes detrimental effects of inflammation of the female bovine reproductive tract on the establishment and maintenance of pregnancy. In addition to detecting the most sensitive antibiotic to different types of bacteria responsible for endometritis and its effect on the days open and pregnancy rate.

Materials and Methods

Animal Housing

One hundred Holstein Friesian dairy cows (primipara) ranging from 2.5-3 years with a body condition score of more than 3.5 were used in the present study (scale: 1 = thin, 5 = fat) (Bhalaru et al., 1987). The cows are located on a governmental dairy farm in the south of Egypt (Qena province). All cows were dried well 75 days before calving. The cows were kept in an open shed with a concrete floor. The main feeding stuff during the winter was barssem, rice straw, and concentrate mixture, while during the summer season, drawa was used instead of barseem. All the cows were bred by natural serving.

All experimental procedures were approved by the Ethics Committee for Animal Experiments of the Faculty of Veterinary Medicine, South Valley University, Qena, Egypt.

Clinical Examination of the cows

Clinical endometritis (CE) is defined as an inflammation of the endometrium occurring later than 21 days in milk (DIM) with purulent vaginal discharge and a cervical diameter of >7.5 cm or mucopurulent discharge after 26 DIM (LeBlanc et al., 2002a; Leutert et al., 2012).

Each cow was examined at the time of a routine gynaecological examination after calving. Non pregnant cows after 90 -120 days from the last calving were gynecologically examined, including rectal palpation and vaginal examination. The vaginal examination was performed and the nature of the vaginal discharge was detected. With the help of a flashlight, the cervix and vagina were visually examined for the presence and quality of discharge as previously described (Leutert et al., 2012). A 4-point scoring system (1 = clear mucus, 2 = mucus containing flecks of pus, 3 = discharge containing less than 50% pus, 4 = discharge containing more than 50% pus) to classify vaginal mucus was established by Williams et al. (2005) and has been used in recent studies (Sheldon et al., 2006; Dubuc et al., 2010; Kaufmann et al., 2010; Šavc et al., 2016). Grade 1 (clear mucus) was considered a normal vaginal secretion while grades 2, 3 and 4 were considered abnormal vaginal secretions. The intervals from parturition to the onset of ovarian activity, to the first observed estrous, and to conception were recorded for each cow.

Sampling for bacteriological isolation

Samples were collected for bacteriological examination immediately after clinical examination. Cows were classified into two groups. The first group is the control group (9 cows), while the second group is the endometritis group or treated group (91 cows). The endometritis group has a history of abnormal calving (dystocia) followed by a retained placenta and failure to conceive after natural serving within 90-120 days of calving. For each cow, the vulva lips were parted and swabs were collected from the uterine body. A transport medium composed of thioglycollate broth was used for transportation of the swabs at 4°C in an icebox and processed for bacteriological examination. It was cultured within 1 h of collection. Samples cultured on Nutrient broth, Nutrient media, Macconkey media, Blood agar, Mannitol media and EMB agar (Lab M Ltd., Lancashire, United Kingdom). Bacteria were identified after a 24-h incubation at 37°C for bacterial growth. Identification was based on the characteristics of colonies, hemolysis, gram stain, morphology, the catalyze, indole production, methyl red, Voges-Proskauer, and citrate production tests (Williams et al., 2005). All isolates were tested for in vitro antibiotic sensitivity (Muneer et al., 1991). Sensitivity to antibiotics was tested by the disc diffusion method and performed according to CLSI (formerly NCCLS) guidelines in Mueller-Hinton agar. For this purpose, a separate disc containing Cefoprazone 10 mg, Lincomycin 10 mg, Tetracycline 10 mg, Ampicillin/sulbactam 10 mg, Tobramycin 10 mg, and Pefloxacin 10 mg per disc was employed.

Methods of treatment

Cows with clinical endometritis were subjected to the treatment regimen using the most sensitive antibiotic to the causative microorganisms (Cefoprazone 4 gm) as the intrauterine route and Cefoprazone 4 gm intramuscular every 24 hours for 5 days.

Detection of uterine involution

The determination of uterine involution is based on gynaecological examinations at three times with a 14-day interval (days 14, 28, and 42) according to the following procedures: evaluation of the general health, detection of the nature of the vaginal secretion, palpation of the uterus, cervix, and ovaries. The uterus is considered completely involuted if the two horns of the uterus are symmetrical and all the uterine parts are present at the edge of the pelvic cavity with normal tonus, and consistency, in addition to the absence of pathological cervical discharge. Based on the case definition of endometritis derived previously, clinical resolution was subsequently defined as the absence of mucopurulent or worse discharge and cervical diameter of 2 fingers at the second examination.

Follow-up Examination was done 14 days after treatment. Clinical cure was detected by the absence of pus discharge. A second dose of treatment can be given to cases that are not clinically cured, and a further examination of these cases occurs for a third and final time after an additional 14 days. The presence of any turbid discharges at the third examination makes the case considered a clinical failure. Normal herd reproduction management was done on all cows after the curing of endometritis. This was achieved by the administration of one or more injections of PGF2α and or GnRH for estrus detection, synchronisation, or synchronisation of ovulation. The following data was recorded to evaluate the reproductive performance, which is: the interval from calving to the first estrus, the interval from calving to pregnancy (days open), and the number of services per conception. Transrectal palpation at 45 days post-breeding was done for pregnancy diagnosis.

Statistical analysis

The collected data was statistically analyzed. Statistical evaluation of the results was performed using SPSS® (SPSS 20, IL, USA). The results for the reproductive findings of the groups and the types of bacterial infections were analyzed using multivariate analysis (ANOVA). A P value < 0.05 was considered statistically significant.

Results

Incidence of endometritis and isolation of different bacteria

The average incidence of endometritis was 91%, depending on the bacterial growth. It is shown in Table (1) that various species of bacteria were isolated from uterine samples, which include Staphylococcus, Streptococcus, E. coli and Klebsiella. The infection is either a single infection (Staphylococcus only) (7 cows) or mixed infection (84 cows) while the control group has no bacterial growth (9 cows). It was found that the incidence of the mixed infection is higher than that of the single infection. Staphylococcus was the only microorganism that caused a single infection, while the other microorganisms were usually mixed. Mixed infection was classified into three types: infection with two microorganisms, infection with three microorganisms, and infection with four microorganisms. Mixed infection with two microorganisms has a higher incidence. The infection with Staphylococcus and E. coli is the higher incidence for the infection with two microorganisms (30 cows) (33%), while the infection with Streptococcus and Klebsiella is the least in incidence in infection with two microorganisms (only one cow). In the infection with three microorganisms, infections with Staphylococcus, E. coli and Klebsiella had the higher incidence (10 cows), while infections with Staphylococcus, Streptococcus and Klebsiella had the lower incidence (only one cow).

The effect of endometritis on uterine involution

The comparison between the groups of bacterial infections indicates that the Staphylococcus microorganism alone does not cause turbidity in the secretion, while in combination with other microorganisms like Streptococcus, E.coli, and Klebsiella, the turbidity was obvious. The turbidity varies according to the type of microorganisms, as it is low in the case of infection with Staphylococcus in combination with other microorganisms and moderate in the infection with Streptococcus in combination with E.coli, and reaches its maximum range in the infection of E.coli in combination with klebsiella, or the infection with three microorganisms or four microorganisms (Table 2).

The vaginal mucosa does not have congestion or has a light degree of congestion in the control group. While congestion was obvious in the case of infection with Staphylococcus microorganism alone (28.7%).The congestion increases in the case of infection with two microorganisms, such as infection with (Streptococcus and E.coli) (77 %), which was more prominant than infection with (Staphylococcus and Streptococcus), (Staphylococcus and E.coli) or (Staphylococcus and Klebsiella) (50%). It reaches its maximum (100 %) in the case of infection with (E.coli and Klebsiella) or infection with three microorganisms (Staphylococcus, Streptococcus and E.coli), (Staphylococcus, E.coli and Klebsiella) or four microorganisms (Staphylococcus, Streptococcus, E.coli and Klebsiella) (Table 2).

The cervix was slightly inflamed (slightly thick) in the case of infection with the Staphylococcus microorganism (28.7%) while this inflammation increased when the infection becomes combined with two microorganisms (50%) such as (Staphylococcus and Streptococcus), (Staphylococcus and Klebsiella). The inflammation also increases more in infection with (Staphylococcus conjugated with E.coli) (85%) or (Streptococcus conjugated with E.coli) to reach its maximum (100%) in infection with (E.coli conjugated with klebsiella) or infection with three microorganisms (Staphylococcus, Streptococcus and E.coli), (Staphylococcus, E.coli and Klebsiella ) or four microorganisms (Staphylococcus, Streptococcus, E.coli and Klebsiella) (Table 2).

The uterine horn was slightly inflamed (slightly thick and asymmetrical) in the infection with Staphylococcus microorganism (single infection), where this inflammation increased in the infection with two microorganisms depending on the virulence of the combined microorganisms, as it is higher in the case of infection with (Staphylococcus, E. coli) or (Streptococcus, E. coli) (77%) than the infection with (Staphylococcus, Streptococcus) or (Staphylococcus, Klebsiella) (50 %). The inflammation reaches its maximum in the case of infection with (E. coli, Klebsiella) or infection with three microorganisms (Staphylococcus, Streptococcus and E.coli), (Staphylococcus, E.coli and Klebsiella) or four microorganisms (Staphylococcus, Streptococcus, E.coli and Klebsiella) (Table 2).

Ovarian structures in relation to the type of bacterial infection

The clinical findings in the ovary in relation to the type of bacterial infection were shown in Table 2. The corpus luteum was the only structure found in the ovary in the cases of single infection with Staphylococcus microorganism, mixed infection as (Staphylococcus, Streptococcus) and/or (Staphylococcus, Streptococcus, E. coli and Klebsiella) (100%). The presence of the corpus luteum was higher in cases of infection with (Streptococcus, E. coli) where its incidence was (85%) and the rest (15%) was cystic ovaries. The incidence of CL in the aforementioned group was higher than its incidence in cases of infection with (Staphylococcus, E. coli) (70% CL and 30% cystic ovary), and higher than the incidence of infection with (E. coli, Klebsiella), (Staphylococcus, Streptococcus, E. coli) (75% CL and 25% cystic ovary). The presence of cystic ovary was prominent in cases of infection with (Staphylococcus, Klebsiella) or (Staphylococcus, E. coli, Klebsiella) as it occurs in 50 % of the infected cases while the other 50% have CL (Table 2).

The postpartum period in relation to the type of bacterial infection

The number of the cows treated in each dose was indicated in Table 3. The postpartum period to pregnancy (days open) was short in cases of single infection with Staphylococcus microorganism and mixed infection with Streptococcus and Klebsiella, but moderate in cases of mixed infection with two microorganisms such as (Staphylococcus, Streptococcus) and (Staphylococcus, Klebsiella). The postpartum period becomes longer in mixed infection with (Staphylococcus, E.coli) and (Streptococcus, E.coli). This period increases more in mixed infections with (E.coli, Klebsiella) and in mixed infections with three microorganisms like (Staphylococcus, Streptococcus, and E .coli) and (Staphylococcus, E.coli, and Klebsiella) to reach its maximum in mixed infection with four microorganisms (Staphylococcus, Streptococcus, E.coli, and Klebsiella) (Table 4).

The pregnancy rate was higher in cases of infection such as (Staphylococcus infection), mixed infections such as (Staphylococcus, Streptococcus) and (Staphylococcus, Streptococcus, E. coli and Klebsiella) (100%), while this rate decreased to moderate in cases of mixed infections such as (Staphylococcus, Klebsiella) or (Staphylococcus, E. coli and Klebsiella) (50%). The pregnancy rate was at a level above moderate in cases of mixed infection by (Streptococcus, E .coli) (85%), (E. coli, Klebsiella) (75%), (Staphylococcus, Streptococcus, and E. coli) (75%), and (Staphylococcus, E. coli) (70%) (Table 4).

 

Table 1: Bacteriological findings of the uterine swab and the most sensitive antibiotic

Type of infection	No. of bacterial infection	Name of microorganisms		No. of +ve samples by culture		The most sensitive antbiotic
Single	with one microorganism	Staphylococcus only		7	Cefoperazone , ampicillin/sulbactam
Mixed	with two microorganisms	Staphylococcus and Streptococcus		2	Cefoperazone , ampicillin/ sulbactam
		Staphylococcus and E.coli		30	Cefoperazone, pefloxacin
		Streptococcus and E.coli		13	Cefoperazone, pefloxacin
		Staphylococcus and Klebsiella		2	Cefoperazone, pefloxacin
		Streptococcus and Klebsiella		1	Cefoperazone, pefloxacin
		E.coli and Klebsiella		5	Cefoperazone, pefloxacin
	with three microorganisms	Staphylococcus, Streptococcus and E.coli		8	Cefoperazone, pefloxacin
		Staphylococcus, Klebsiella and E.coli		10	Cefoperazone, pefloxacin
		Streptococcus, Klebsiella and E.coli		2	Cefoperazone, pefloxacin
		Staphylococcus, Streptococcus and Klebsiella		1	Cefoperazone, pefloxacin
	with four microorganisms	Staphylococcus, Streptococcus, E.coli and Klebsiella		10	Cefoperazone, pefloxacin
CONTROL	No bacterial growth		9
TOTAL			100

 

Table 2: The reproductive clinical findings in relation to the type of bacterial infection of dairy cows:

Type of bacterial infection	Vaginal secretion		Vaginal Mucosa		Cervix diameter		Uterine horn diameter		Ovarian Findings
	Normal discharge	Abnormal discharge	Rosy red	Congested	Two fingers	Three fingers	Inflamed (3 fingers)	Non inflamed (2 fingers)	CL	Cyst
Control	100 a	0	75 a	25 d	75 a	25 d	25 d	75 a	100 a	0
Staphylococcus only	100 a	0	71.3 a	28.7 d	71.3 a	28.7 d	28.7 d	71.3 a	100 a	0
Staphylococcus and Streptococcus	50 b	50 c	50 b	50 c	50 b	50 c	50 c	50 b	90 b	0
Staphylococcus and E. coli	50 b	50 c	50 b	50 c	15 c	85 b	77 b	23 c	70 c	30 b
Staphylococcus and Klebsiella	50 b	50 c	50 b	50 c	50 b	50 c	50 c	50 b	50 d	50 a
Streptococcus and E. coli	23 c	77 b	23 c	77 b	15 c	85 b	77 b	23 c	85 c	15 c
E. coli and Klebsiella	0	100 a	0	100 a	0	100 a	100 a	0	75 c	25 c
Staphylococcus, Streptococcus and E. coli	0	100 a	0	100 a	0	100 a	100 a	0	75 c	25 c
Staphylococcus, E. coli and Klebsiella	0	100 a	0	100 a	0	100 a	100 a	0	50 d	50 a
Staphylococcus, Streptococcus, E. coli and Klebsiella	0	100 a	0	100 a	0	100 a	100 a	0	100 a	0

- The results are expressed as a percentage.

- CL: Corpus luteum

- Values bearing different superscripts in the same column differ significantly (P<0.05)

 

Table 3: The number of the cows treated in each dose

Total No. of cows	No. of cows for 1st dose	No. of cows for 2nddose	No. of cows for 3rd dose	Resist
91	21/91	20/70	30/50	20

 

Table 4: Fertility parameters (pregnancy rate and days open) of dairy cows in relation to the type of bacterial infections:

Type of bacterial infection	Total number of the cases	Pregnancy rate after treatment		Mean Postpartum days to pregnancy
		Pregnant	Non Pregnant
Control	9	100	0	113
Staphylococcus only	7	100	0	145
Staphylococcus and Streptococcus	2	100	0	150
Staphylococcus and E. coli	30	70	30	170
Staphylococcus and Klebsiella	2	50	50	160
Streptococcus and Klebsiella	1	100	0	145
Streptococcus and E. coli	13	85	15	180
E. coli and Klebsiella	5	75	25	245
Staphylococcus, Streptococcus and E. coli	8	75	25	245
Staphylococcus, Streptococcus,and Klebsiella	1	0	100	245
Staphylococcus, E. coli and Klebsiella	10	50	50	250
Streptococcus, Klebsiella and E. coli	2	50	50	250
Staphylococcus, Streptococcus, E. coli and Klebsiella	10	100	0	275

-The values of pregnancy rate after treatment are expressed as a percentage.

 

Discussion

Shortly after parturition, the uterus is a large organ and the normal involution is an aseptic process, but this is the exception rather than the rule, as the uterus that suffers from periparturient problems is larger and cannot control uterine infections. If dystocia occurs or if assistance is needed, the chances of bacterial contamination increase. Dystocia or uncorrected obstetrical manipulations cause excessive stretching of the uterus, which reduces its contractility. Consequently, retention of lochia occurs beyond the normal period, which exposes a good medium for bacterial growth and eventually causes endometritis.

The present work showed that the average incidence of endometritis was 91%. This result agrees with several previous studies that indicated mild to severe endometritis occurred in 90% of postpartum cows during the second to fourth postpartum weeks (Földi et al., 2006, Sheldon et al., 2004).

The results of the present study showed a wide variety of bacteria isolated from cows infected with PP endometritis. The bacteria most frequently isolated are Escherichia coli (E. coli), Staphylococcus spp, Streptococcus spp, and Klebsiella spp. The most common pathogenic species are E. coli and Staphylococcus spp. and this infection was mainly due to retained foetal membrane. Other bacteria, such as Streptococcus spp. have also been isolated as additional flora in connection with major uterine pathogens. These results are somewhat consistent with previous studies (Sheldon et al., 2004, Williams et al., 2005). These studies illustrated that the bacteria isolated were found to be obligate uterine pathogens (E. coli, Trueperella pyogenes), potential uterine pathogens (non-hemolytic streptococci) and opportunistic bacteria (Klebsiella spp., Proteus spp. and Staphylococci). Königsson et al. (2001) reported that E.coli, Streptococci, Fusobacterium necrophorum (F. necrophorum), and Trueperella pyogenes, were predominant bacteria in cows with endometritis resulting from retained foetal membranes. Later on, (Königsson et al., 2001, Williams et al., 2005, LeBlanc, 2008) demonstrated that E. coli and Streptococcus spp. are the most commonly isolated bacterial agents from the uterus of postpartum cows. However, the same authors reported that E. coli, A. pyogenes, F. necrophorum and Prevotella species were the most common and major uterine pathogens. Other bacteria, such as Streptococci, Staphylococci, and E. coli, have also been cultured and identified as having endometritis of varying severity (Zemjanis, 1980). It has been difficult to identify the most significant microbes associated with endometritis because both pathogenic and non-pathogenic organisms colonise the bovine endometrium, and many of them are fastidious (Studer, 1981).

It is noticed in the present work that some bacteria act synergistically to enhance the severity of uterine diseases like those occur in mixed infections with E. coli and Staphylococcus, and that of Streptococcus and E. coli. These results are close to the results stated by Singh et al. (2008) in which some bacteria, including A. pyogenes, F. necrophorum, and Prevotella spp., act synergistically to enhance the severity of the uterine disease. Each of these species produces substances to enhance bacterial growth. Some bacteria, such as F. Necrophorum, after invading the uterine tissue, produce a leucocidal toxin that suppresses phagocytosis (Singh et al., 2008, Sheldon, 2004) and protects A. Pyogenes, which subsequently produces catalase and a growth factor to support the proliferation of F. Necrophorum (Singh et al., 2008).

Under routine field conditions, it is suggested that herd records are first used to identify cows at risk of endometritis, such as cows with a history of retained placenta, dystocia, twins, hypocalcaemia, ketosis, or metritis. Then, the vaginal mucus should be examined for the presence of pus (Sheldon, 2020). The types of bacteria responsible for endometritis reflect the appearance and degree of turbidity of the uterine secretion. The present work found infection with Staphylococcus only has a clear secretion while combinations between Staphylococcus and E. coli, or Streptococcus, or Klebsiella cause turbidity of the secretion. Mixed infections usually cause turbidity of the secretion, which varies according to the severity and type of mixed microorganisms. Mixed infection with three microorganisms causes more turbidity than infection with two microorganisms, while infection with four microorganisms has the highest degree of turbidity. In the previous study, Williams et al. (2005) evaluated the appearance and odour of vaginal mucus and showed that mixed infections associated with purulent or mucopurulent discharge, while other mixed infections associated with a change in the odour of exudate, such as E. coli, non-hemolytic Streptococci, and A. pyogenes, cause foul-smelling exudates. Furthermore, several previous studies have also illustrated that clinical endometritis is characterised by the presence of purulent discharge excreted from the uterus. (Sheldon et al., 2002, Runciman et al., 2009, Pleticha et al., 2009). Recently, an experimental study was carried out on an in vivo model of clinical endometritis in Holstein heifers using pathogenic E. coli and Trueperella pyogenes (T. pyogenes). The study showed that heifers that received intrauterine infusion of pathogenic bacteria developed purulent vaginal mucus, an accumulation of echogenic fluid in the uterus, and an increased bacterial load in vaginal mucus (Piersanti et al., 2019).

Uterine involution necessitates a reduction in cervical diameter from approximately 30 cm immediately following parturition to approximately 2 cm at day 7 postpartum. Kasimanickam et al. (2004) found that the larger the diameter of the cervix after parturition, the longer the time taken for involution to occur. The results of our study indicate that cows suffering from endometritis have abnormalities in their cervix and uterine horn (very thick and more than 7.5 cm) while normal cows (control group) have a normal cervix (less than 7.5 cm). The results of the present study are in line with those of the previous one (Oltenacu et al., 1983) which mentioned that the diameter of the cervix was greater than 5.5 cm in primiparous and 6.0 cm in multiparous cows detected by rectal palpation 12 to 26 days postpartum was the best indicator of subsequent poor reproductive performance.

In the present work, it was found that cows bearing CL on the ovary have a decreased days-open and an increased pregnancy rate relative to cows with a cyst on the ovary or no palpable structures. These results are somewhat in accordance with that of Bonnett et al. (1993), who illustrated that cows that posed an early resumption of the ovary during the postpartum period at 26 days in milk acquired a 10 % increase in the pregnancy rate. Uterine infection postpartum could raise the secretion of PGF2α and cortisol, which is accompanied by the development of cystic ovarian disease (Etherington et al., 1985a, Etherington et al., 1985b, Bosu and Peter, 1987). This is also confirmed by the results of the current study, as some cows with uterine infection (endometritis) have cysts on their ovaries (21% of the cows) while the other cows have a CL.

In this study, the postpartum period to pregnancy (days-open) was increased due to endometritis and reached more than 125 days in cows infected with two microorganisms (mild endometritis) and reached 245 days in cows infected with four microorganisms (severe endometritis). The pregnancy rate reached approximately 78 %, in contrast, 22% of the cows were empty and they will be culled due to reproductive failure. These findings are in the same line with previous studies. McDougall et al. (2011) and Lee and Kim (2006) showed reduced pregnancy rates and subsequently increased culling rates in cows with uterine infection, while Gilbert et al. (2005) found endometritis was highly significant for reduced pregnancy rates where days open increased to 218 days.

Conclusion

It is concluded that the greater the number and virulence of the microorganisms responsible for the infection, the greater the severity of uterine inflammation and the longest PP period to pregnancy. Various types of bacteria are responsible for uterine infections causing endometritis, such as Staphylococcus, Streptococcus, E. coli, and Klebsiella. Cefoperazone is the most sensitive antibiotic for the treatment of complicated cases of postpartum endometritis caused by mixed infections and high-virulence bacteria. In addition, cefoperazone treatment hurries the uterine involution and, subsequently, decreases the days-open and increases the pregnancy rate.

Further researches should be carried out on cefoperazone treatment to discover its sensitivity against other types of microorganisms responsible for endometritis in animals and humans.

acknowledgements

The authors thank all workers in the governmental dairy farm of Qena province and the members of the microbiology lab belonging to the Faculty of Veterinary Medicine, South Valley University, for their help during the study.

Conflicts of interest

The authors have no conflict of interest to declare.

novelty statement

The current study showed that different bacterial species (Staphylococcus, Streptococcus, Escherichia coli, and Klebsiella) were isolated from cows suffering from postpartum endometritis. Cefoperazone is the antibiotic that is sensitive to these types of microorganisms responsible for endometritis and has a favorable effect on the days open and pregnancy rate.

authors contribution

Yahia, Alaa, Mohamed and Abd El-Latif conceived and designed the study. Yahia executed the experiment and interpreted the data, seriously revised the manuscript for necessary intellectual contents, and approved the final manuscript. Waleed and Yahia revised the manuscript. All the authors have approved the submitted version of the manuscript.

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