Chlamydophila pneumoniae

Infectious agent

The infectious agent is Chlamydophila pneumoniae, an obligate intracellular bacterium (previously named Chlamydia pneumoniae).

Identification

Clinical features

Chlamydophila pneumoniae infection is often mild. The initial infection appears to be the most severe with reinfection often asymptomatic. A spectrum of illness from pharyngitis and sinusitis to pneumonia and bronchitis may occur. Sometimes there is a biphasic illness

with initial upper respiratory

tract infection symptoms which resolve and then a dry cough and low grade fever. The organism may be an infectious precipitant of asthma and is implicated in about 5% of episodes of acute bronchitis. Cough occasionally persists for some

weeks despite appropriate antibiotic therapy.

Method of diagnosis

Chest X-ray may show small infiltrates. Most cases of pneumonia are mild but the illness can be severe in otherwise debilitated patients. Laboratory diagnosis is made with serology or culture:

• Serological diagnosis is made by detecting a four fold rise in antibody

titre using microimmunofluorescence (MIF). MIF is the only serological test

that can reliably differentiate chlamydial species. A single antibody titre is of little diagnostic value on its own as the seroprevalence of antibodies to C. pneumoniae approaches 50% in the adult

population. Seroconversion may take up to eight weeks in an initial infection but it tends to occur much more quickly in reinfection (one to two weeks). False positive antibody tests

can occur in the presence of a positive rheumatoid factor.

• Culture of nasopharyngeal aspirates, throat swabs or bronchial lavage fluid is possible. Swabs should be placed in chlamydia transport medium whilst other specimens can be collected in the usual containers. All samples should be kept refrigerated. Diagnosis by PCR is available through the Victorian Infectious Diseases Reference Laboratory (VIDRL) but it is currently only being used in investigation of outbreaks

of respiratory illness where conventional testing has not revealed the cause ofinfection.

Incubation period

The incubation period is approximately 21 days

Public health significance and occurrence

C. pneumoniae is emerging as a frequent cause of both upper and lower respiratory tract infections. It appears to be a common cause of mild pneumonia,especially in school age children. Up to

10% of cases of community-acquired pneumonia can be attributed to this organism. Asymptomatic carriage occurs in 2–5% of the population. Only about 10% of infections result in pneumonia. Epidemics of respiratory illness can occur and these usually occur in institutional settings such as military

barracks or nursing homes. Speculation regarding the bacteria’s involvement in the pathogenesis of atherosclerotic arterial disease continues. Seroepidemiologic studies have shown an association between

evidence of C. pneumoniae infection and atherosclerosis but the significance of this is not yet established. Studies are ongoing into the effect of prophylactic

antibiotic treatment on prevention of atherogenesis.

Possible links with Alzheimer’s disease, arthritis and asthma are also postulated.

Reservoir

Humans.

Mode of transmission

Transmission occurs person to person via respiratory secretions.

Period of communicability

Asymptomatic carriers may be an important source of infection. Symptomatic patients can carry the bacteria in the nasopharynx for months after illness.

Susceptibility and resistance

Everyone is susceptible to infection, with the risk of clinical disease increasing in patients with a chronic medical condition. Immunosuppressed patients do not seem to be more susceptible, but older debilitated patients may develop severe disease. Initial infection occurs in school-age children with up to 50% of the population becoming seropositive by 20 years of age. Infection does not produce complete immunity and reinfection can occur.

Control measures

Control of case

Mild to moderate infections are generally treated with roxithromycin or doxycycline. Consult the current version of Therapeutic guidelines: antibiotic (Therapeutic Guidelines Limited). Patients being managed in the community should be reviewed after 24 hours to assess treatment response. Therapy may need to be continued for up to 14 days. Isolation is not necessary, but the patient should be counselled on good respiratory hygiene, such as coughing into disposable tissues..

Special settings

Institutions

Avoid crowding in living and sleeping quarters.

                             Chlamydia (genital infection)

Infectious agent

Chlamydia trachomatis serogroups D–K cause disease.

Identification

Clinical features

Most women with urethral or endocervical chlamydial infection are asymptomatic. Clinical manifestations may include vaginal discharge, dysuria and post-coital or intermenstrual bleeding. Less frequent manifestations include urethral syndrome (dysuria and pyuria), bartholinitis, perihepatitis and proctitis.Complications and sequelae may result in chronic pelvic pain, infertility and ectopic pregnancy. Infections during pregnancy may cause preterm rupture of the membranes and preterm delivery. It can also cause conjunctivitis in the newborn and pneumonitis in the young infant.

The primary presentation of chlamydial infection in
males is urethritis but infection may be asymptomatic. Possible sequelae and complications of male urethral infection are epididymitis, infertility, Reiter’s syndrome and conjunctivitis. Receptive anal intercourse in men who have sex with men (MSM)

may result in chlamydial proctitis.

Method of diagnosis

Testing individuals at high risk of chlamydial infection is recommended. High risk individuals include those with a clinical presentation suggestive of chlamydial infection, individuals attending general practitioners for testing of sexually acquired infection (STI), those attending STI and family planning clinics and gay men’s health centres and partners of those already diagnosed with an STI. Laboratory investigations currently available are:

• cell culture (only in specialised laboratories)

• antigen assays including direct

immunofluorescence or enzyme immunoassay

• hybridisation assays such as the DNA probe

• amplification assays including PCR and ligase chain reaction (LCR).

The choice of test depends on the specimen type submitted, the cost of the test, the sensitivity and specificity of the test and the expertise and size of the laboratory.

Incubation period

The incubation period is poorly defined but is probably 7–14 days or longer.

Public health significance and occurrence

Infection with C. trachomatis has become a major public health problem because of the long term consequences of infection experienced predominantly by women. These include chronic pelvic pain, ectopic pregnancy and infertility. Rarely males may also become infertile. Chlamydia is the most commonly notified sexually transmissible bacterial disease in Victoria. It affects both genders. The annual number of notified cases has more than doubled since the early 1990s. Approximately 75% of infections are notified from individuals aged less than 30 years.

The prevalence of chlamydial genital infections in Australia has not been comprehensively established but it has been estimated to be 2.5 –14% in STD clinic patients, 5% in family planning

clients and up to 15% in commercial sex workers.

While the spontaneous cure rate has been estimated at 7.4%, immunity following infection is thought to be typespecific and only partially protective. As a result recurrent infections are common.

Risk factors for chlamydial infections include a relatively high number of sexual partners, a new sexual partner and lack of use of barrier contraceptive measures.

Endocervical C. trachomatis infection has also been associated with an increased risk of acquiring human

immunodeficiency virus (HIV) infection and may also increase HIV infectiousness.

Reservoir

Humans.

Mode of transmission

proportion of Transmission of C. trachomatis occurs primarily by sexual contact. Mother to baby transmission occurs when mothers colonised with C. trachomatis infect their babies as they are born vaginally. A high infections in women are asymptomatic resulting in untreated disease, ongoing transmission and an increased risk of sequelae.

Period of communicability

The period of communicability is unknown but may be months to years.

Susceptibility and resistance

Everyone is susceptible to infection.

Control measures

Preventive measures

Preventive measures include education about safe sex practices including use of condoms and early detection of infection by testing of those at risk.

Control of case

Azithromycin or doxycycline are used as first line antimicrobials to treat

chlamydial infection. Advice on the treatment of chlamydial infections can be found in Therapeutic guidelines:

antibiotic (Therapeutic Guidelines Limited) and the National managementguidelines for sexually transmissible infections (Venereology Society of Victoria, 2002). Specialist consultation should be sought

for complicated or disseminated infections.

Control of contacts

Sexual partners of individuals with chlamydial infection should be examined and investigated then treated empirically.

              Cholera and its treatment

Definition:

Cholera is an acute intestinal infection caused by ingestion of food or water contaminated with the bacterium Vibrio cholerae. It has a short incubation period, from less than one day to five days, and produces an enterotoxin that causes a copious, painless, watery diarrhoea that can quickly lead to severe dehydration and death if treatment is not promptly given. Vomiting also occurs in most patients.

Infectious agent

Vibrio cholerae serogroups O1 or O139 cause cholera.

Identification

Clinical features

Asymptomatic infection with V. cholerae is more frequent than clinical illness and bacteria may be present in faeces for 7–14 days. Mild cases of diarrhoea are common especially among children. In severe cases disease is characterized by a sudden onset of symptoms with profuse painless watery (rice water) stools, occasional vomiting, rapid dehydration, acidosis and circulatory collapse. In untreated cases, death may

occur in a few hours and the case fatality rate may exceed 50%.

Method of diagnosis

The diagnosis is confirmed by the isolation of V. cholerae serogroup O1 or O139 from faeces. A presumptive diagnosis can be made by visualization by dark field or phase microscopy of V. cholerae’s characteristic motility, specifically inhibited by preservative-free serotype-specific antiserum.

Incubation period

The incubation period is from a few hours to five days. It is usually two to three days.

Public health significance and occurrence

Cholera can occur in epidemics or pandemics. In any single epidemic one particular biovar tends to predominate. Endemic cholera occurs in parts of Africa, Central Europe and Asia. Cholera appears to be increasing worldwide in both the number of cases and their distribution. Only sporadic imported cases in returned travellers occur in Victoria. V. cholerae O1 is established in the riverine environment in some parts of Queensland and New South Wales however human disease is rare.

Reservoir

V. cholerae is often part of the normal flora of brackish water and estuaries and can be associated with algal blooms (plankton). Humans are one of the reservoirs of the pathogenic form of V. cholerae.

Mode of transmission

Transmission occurs person to person via respiratory secretions.

Period of communicability

Asymptomatic carriers may be an important source of infection. Symptomatic patients can carry the bacteria in the nasopharynx for months after illness.

Susceptibility and resistance

Transmission occurs through ingestion of contaminated water and food. Sudden large outbreaks are usually caused by a contaminated water supply. Direct person to person contact is rare.

Period of communicability

Persons are infectious during the acute stage and for a few days after recovery. By the end of the first week 70% of patients are non-infectious. By the end of the third week 98% are non-infectious. Occasionally the carrier state may persist for months and chronic biliary infection with intermittent shedding of organisms may last for years.

Susceptibility and resistance

Even in severe epidemics, clinically apparent disease rarely occurs in more than two per cent of those at risk. Gastric achlorhydria increases risk of disease. There is some evidence that breastfeeding reduces the risk of infection. Infection results in a rise in antibodies with increased resistance to reinfection. Infection with an O1 strain does not confer immunity against O139 strains and vice-versa.

Control measures

Preventive measures

Travellers to endemic areas should be advised on careful food and water consumption and personal hygiene. Travellers to endemic areas should carry oral rehydration powder available from pharmacies which must be reconstituted with boiled or sterilised water. Cholera vaccine is a heat-killed suspension of the Inaba and Ogawa serotypes of V. cholerae O1. It provides partial protection (approximately 50%) for

three to six months. It is not routinely recommended and advice to overseas travellers should emphasise careful selection of food and water rather tha immunisation. Officially, cholera vaccination certificates are no longer required by any country or territory. Unofficially, some countries may still require such a certificate, in which case a single dose of cholera vaccine would satisfy this requirement.

Control of case

Cholera is subject to quarantine conditions under the Commonwealth Quarantine Act 1908. Prompt fluid therapy with adequate volumes of electrolyte solution such as Gastrolyte is critical as life-threatening

dehydration may rapidly occur. This is usually all that is required for mild to moderate illness. Patients with severe dehydration require urgent intravenous fluid. Antimicrobial agents to which the strain is sensitive shorten the duration of diarrhoea and the duration of Vibrio excretion. Investigate possible sources of infection, particularly if there is no history of travel to an endemic region.

Control of contacts

Contacts should be observed for five days from the date of last exposure. This may include all fellow travellers of a case. Stool culture of any contacts with symptoms of diarrhoea and stool culture of all household contacts, even if asymptomatic, should be undertaken. Cases should also be looked for among those possibly exposed to a common source. Immunisation of contacts is not indicated.

Control of environment

Severely ill patients should be isolated in hospital, with standard precautions. Less severe cases can be managed at home. Disinfection of linen and articles used by the patient is required. Faeces and vomitus can be disposed of into the toilet without preliminary disinfection, except in areas with an inadequate sewage disposal system. Terminal cleaning of hospital rooms and equipment is required. In cases with no history of overseas travel, urgent investigation of potentially contaminated food and water supplies is indicated.